Delta-sigma based power converter control

Abstract

Power conversion systems and methods are provided that use a four-leg power converter and delta-sigma control. Each of the four phase legs includes an LC filter and power switching elements. A control system determines an electrical operational characteristic for each of the four phase legs and generates control reference targets in a stationary reference frame for each phase leg based on the electrical operational characteristics and a rotational reference frame. The rotational reference frame includes a direct axis (d-axis) component, a quadrature axis (q-axis) component, a delta axis (δ-axis) component, and a sigma axis (σ-axis) component. The delta axis component indicates a difference between a common mode and a neutral electrical characteristic, and the sigma axis component indicates a sum of the common mode and the neutral electrical characteristic. The control system drives the power switching elements of the four phase legs in accordance with the control reference targets.

Description

Attorney Docket No.: 175073.00272 DELTA‐SIGMA^BASED^POWER^CONVERTER^CONTROL^ ^ CROSS‐REFERENCE^TO^RELATED^APPLICATIONS^

[0001] This application claims priority to U.S. Provisional Application No. 63 / 662,735, filed on June 21, 2024, the contents of which are hereby incorporated by reference in their entirety. STATEMENT^REGARDING^FEDERALLY^SPONSORED^RESEARCH^

[0002] N / A ^ BACKGROUND^

[0003] Power converters of various types have been produced and used in many industries and contexts. Example power converters include alternating current (AC) to direct current (DC) rectifiers, DC to AC inverters, and DC to DC converters. AC to DC rectifiers, also referred to as AC / DC rectifiers, convert AC power to DC power. DC to AC inverters, also referred to as DC / AC inverters, convert DC power to AC power. Power converters can be used for various purposes, such as rectifying AC power from an AC grid power source to DC power for charging a battery, or inverting DC power from a battery to AC power to drive a motor or supply AC power to an AC grid. Further, power converters can be used in various contexts, such as in or connected to an electric vehicle, an engine generator, solar panels, and the like. SUMMARY^

[0004] Some embodiments described herein provide power converter systems, methods, and media that use delta-sigma (δσ)-based control of an AC / DC converter to, for example, actively control common mode current and / or voltage on a neutral leg of a three- phase AC system. Some embodiments described herein provide power converter systems, methods, and media that use Delta-Sigma (Δ / Σ)-based control of a DC / DC converter. Some embodiments described herein provide reconfigurable power converter systems, methods, and media that enable an AC / DC converter to operate in a three-phase mode or a single- -1- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 phase mode. Some embodiments described herein provide power converter systems, methods, and media that combine two more or more of delta-sigma-based control of an AC / DC converter, Delta-Sigma-based control of a DC / DC converter, and / or reconfigurable power converter systems.

[0005] In some examples, a power converter system is provided that includes: a four- leg power converter and a control system. The four-leg power converter includes a direct current (DC) voltage section including a DC bus and an alternating current (AC) voltage section including AC connection nodes, and four phase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements. The control system is coupled to the four-leg power converter and is configured to: determine at least one electrical operational characteristic for each of the four phase legs; generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ-axis) component, where the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and where the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the four phase legs in accordance with the control reference targets.

[0006] In some examples, a method of converting voltage is provided. The method includes: determining, by a control system, at least one electrical operational characteristic for each of four phase legs of a four-leg power converter having a direct current (DC) voltage section including a DC bus and an alternating current (AC) voltage section including AC connection nodes, the four phase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements. The method further includes generating, by the control system, control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference -2- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, where the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and where the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic. The method further includes driving, by the control system, the power switching elements of the four phase legs in accordance with the control reference targets.

[0007] In some examples, a non-transitory computer readable medium includes instructions stored thereon is provided. The instructions, when executed by a computer, control the computer to: determine at least one electrical operational characteristic for each of four phase legs of a four-leg power converter having a direct current (DC) voltage section including a DC bus and an alternating current (AC) voltage section including AC connection nodes, the four phase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements; generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, where the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and where the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the four phase legs in accordance with the control reference targets.

[0008] In some examples, a power converter system is provided. The power converter system includes: a direct current (DC) / DC converter with a DC voltage section including a DC bus and with a battery connection section including a positive battery terminal node and a negative battery terminal node, the DC / DC converter including: a first -3- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 half bridge including first power switching elements and a first LC filter, where the first LC filter is connected to the positive battery terminal node, and a second half bridge including second power switching elements and a second LC filter, where the second LC filter is connected to the negative battery terminal node; and a control system coupled to the DC / DC converter, the control system is configured to: determine a first electrical characteristic at the positive battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target.

[0009] In some examples, a method of converting voltage is provided. The method includes: determining, by a control system coupled to a direct current (DC) / DC converter, a first electrical characteristic at a positive battery terminal node of the DC / DC converter, where the DC / DC converter includes: a DC voltage section including a DC bus and with a battery connection section including the positive battery terminal node and a negative battery terminal node, a first half bridge including first power switching elements and a first LC filter, where the first LC filter is connected to the positive battery terminal node, and a second half bridge including second power switching elements and a second LC filter, where the second LC filter is connected to the negative battery terminal node; determining a second electrical characteristic at the negative battery terminal node; generating a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; driving the first power switching elements in accordance with the first DC / DC control reference target; and driving the second power switching elements in accordance with the second DC / DC control reference target.

[0010] In some examples, a non-transitory computer readable medium includes instructions stored thereon is provided. The instructions, when executed by a computer, control the computer to: determine a first electrical characteristic at a positive battery -4- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 terminal node of a direct current (DC) / DC converter, where the DC / DC converter includes: a DC voltage section including a DC bus and with a battery connection section including the positive battery terminal node and a negative battery terminal node, a first half bridge including first power switching elements and a first LC filter, where the first LC filter is connected to the positive battery terminal node, and a second half bridge including second power switching elements and a second LC filter, where the second LC filter is connected to the negative battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target.

[0011] In some examples, a power converter system is provided. The power converter system includes: an alternative current (AC) / direct current (DC) power converter including a DC bus and AC connection nodes, the AC / DC power converter having phase legs including a first phase leg, a second phase leg, and a third phase leg, each of the first, second, and third phase legs having a respective LC filter, respective power switching elements, and a respective AC connection node of the AC connection nodes; a DC / DC power converter with DC nodes coupled to the DC bus and with a battery connection section including a positive battery terminal node and a negative battery terminal node, the DC / DC power converter including a first half bridge including first power switching elements and a first LC filter, where the first LC filter is connected to the positive battery terminal node; and a control system coupled to the AC / DC power converter and the DC / DC power converter, the control system configured to: determine an operational mode for the AC / DC power converter to be a three-phase mode having three AC phases, control the AC / DC power converter in the three-phase mode in which the first, second, and third phase legs each correspond to a respective phase of the three AC phases and the AC connection node of the first phase leg is connected to a first node of a three-phase AC system, the AC connection node of the second phase leg is connected to a second node of the three-phase AC system, and the AC connection node of the third phase leg is connected to a third node of the three- -5- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 phase AC system, determine the operational mode for the AC / DC power converter to be a single-phase mode having a single AC phase, and control the AC / DC power converter in the single-phase mode in which the first and second phase legs each correspond to the single AC phase and the AC connection nodes of the first and second phase legs are connected to a first node of a single-phase AC system.

[0012] In some examples, a method of converting voltage is provided. The method includes: determining, by a control system, an operational mode for an alternative current (AC) / direct current (DC) power converter to be a three-phase mode having three AC phases, where the AC / DC power converter includes: a DC bus, AC connection nodes, and phase legs including a first phase leg, a second phase leg, and a third phase leg, each of the first, second, and third phase legs having a respective LC filter, respective power switching elements, and a respective AC connection node of the AC connection nodes, and where a DC / DC power converter with DC nodes is coupled to the DC bus and includes a battery connection section including a positive battery terminal node and a negative battery terminal node, the DC / DC power converter including a first half bridge including first power switching elements and a first LC filter, where the first LC filter is connected to the positive battery terminal node; controlling, by the control system, the AC / DC power converter in the three-phase mode in which the first, second, and third phase legs each correspond to a respective phase of the three AC phases and the AC connection node of the first phase leg is connected to a first node of a three-phase AC system, the AC connection node of the second phase leg is connected to a second node of the three-phase AC system, and the AC connection node of the third phase leg is connected to a third node of the three-phase AC system; determining, by the control system, the operational mode for the AC / DC power converter to be a single-phase mode having a single AC phase; and controlling, by the control system, the AC / DC power converter in the single-phase mode in which the first and second phase legs each correspond to the single AC phase and the AC connection nodes of the first and second phase legs are connected to a first node of a single-phase AC system.

[0013] In some examples, a non-transitory computer readable medium includes instructions stored thereon is provided. The instructions, when executed by a computer, control the computer to: determine an operational mode for an alternative current (AC) / direct current (DC) power converter to be a three-phase mode having three AC phases, -6- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 where the AC / DC power converter includes: a DC bus, AC connection nodes, and phase legs including a first phase leg, a second phase leg, and a third phase leg, each of the first, second, and third phase legs having a respective LC filter, respective power switching elements, and a respective AC connection node of the AC connection nodes, and where a DC / DC power converter with DC nodes is coupled to the DC bus and includes a battery connection section including a positive battery terminal node and a negative battery terminal node, the DC / DC power converter including a first half bridge including first power switching elements and a first LC filter, where the first LC filter is connected to the positive battery terminal node; control the AC / DC power converter in the three-phase mode in which the first, second, and third phase legs each correspond to a respective phase of the three AC phases and the AC connection node of the first phase leg is connected to a first node of a three-phase AC system, the AC connection node of the second phase leg is connected to a second node of the three- phase AC system, and the AC connection node of the third phase leg is connected to a third node of the three-phase AC system; determine the operational mode for the AC / DC power converter to be a single-phase mode having a single AC phase; and control the AC / DC power converter in the single-phase mode in which the first and second phase legs each correspond to the single AC phase and the AC connection nodes of the first and second phase legs are connected to a first node of a single-phase AC system.

[0014] The foregoing and other aspects and advantages of the present disclosure will appear from the following description. In the description, reference is made to the accompanying drawings that form a part hereof, and in which there is shown by way of illustration one or more embodiment. These embodiments do not necessarily represent the full scope of the invention, however, and reference is therefore made to the claims and herein for interpreting the scope of the invention. Like reference numerals will be used to refer to like parts from Figure to Figure in the following description. BRIEF^DESCRIPTION^OF^THE^DRAWINGS^

[0015] FIG.1 illustrates a power converter system according to some embodiments.

[0016] FIG. 2 illustrates an example half-bridge converter, according to some embodiments.

[0017] FIG. 3 illustrates a four-leg power converter system according to some embodiments. -7- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272

[0018] FIG.4A illustrates a delta (δ) axis current component in the four-leg converter of FIG.3, according to some embodiments.

[0019] FIG.4B illustrates a sigma (σ) axis current component in the four-leg converter of FIG.3, according to some embodiments.

[0020] FIG. 5 illustrates a power converter system including a four-leg power converter and a control system, according to some embodiments.

[0021] FIG. 6 illustrates a subset of the control system of FIG. 5, according to some embodiments.

[0022] FIG. 7 illustrates a process for converting voltage using a four-leg converter with delta-sigma-based control, according to some embodiments.

[0023] FIGS. 8A-8C illustrate switch-side inductor currents from simulation results, according to some embodiments.

[0024] FIGS. 9A-9B illustrate output voltage and current at a point of common coupling (PCC) from simulation results, according to some embodiments.

[0025] FIGS.10A-10B illustrate example power converter systems including a DC / DC converter, according to some embodiments.

[0026] FIG. 11 illustrates a power converter system with a contactor assembly to selectively bypass a DC / DC converter, according to some embodiments.

[0027] FIG.12 illustrates a DC / DC power converter system including a DC / DC power converter and control system, according to some embodiments.

[0028] FIG.13 illustrates a subset of the control system of FIG.12, according to some embodiments.

[0029] FIG. 14 illustrates a process for converting voltage with a DC / DC converter that uses differential mode (DM) and common mode (CM) variable decomposition, according to some embodiments.

[0030] FIGS. 15A-15C illustrate currents and voltages measured at an AC / DC stage from simulation results, according to some embodiments.

[0031] FIGS. 16A-16C illustrate currents and voltages from simulation results, according to some embodiments.

[0032] FIGS.17A-17D illustrate a reconfigurable power converter system, according to some embodiments. -8- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272

[0033] FIGS. 18A-18D illustrate another reconfigurable power converter system, according to some embodiments.

[0034] FIGS.19A-B illustrate a reconfigurable power converter system, according to some embodiments.

[0035] FIG.20 illustrates a process for operating a reconfigurable power converter, according to some embodiments.

[0036] FIG. 21 illustrates another process for operating a reconfigurable power converter, according to some embodiments.

[0037] FIG. 22 illustrates a power converter system including a four-leg power converter and a control system implementing a single-phase operational mode, according to some embodiments.

[0038] FIG. 23 illustrates a power converter system including a four-leg power converter and a control system implementing a split-phase operational mode, according to some embodiments.

[0039] FIGS. 24A and 24B illustrate condensed diagrams with six different configurations for a four-leg AC / DC converter, according to some embodiments.

[0040] FIG. 25 illustrates a functional block diagram for determining a reference phase θ of an AC signal of a power converter.

[0041] FIG.26 illustrates another power converter system including a four-leg power converter and a control system, according to some embodiments.

[0042] FIG.27 illustrates a subset of the control system of FIG.26, according to some embodiments. DETAILED^DESCRIPTION^

[0043] One or more embodiments are described and illustrated in the following description and accompanying drawings. These embodiments are not limited to the specific details provided herein and may be modified in various ways. Furthermore, other embodiments may exist that are not described herein. Also, functions performed by multiple components may be consolidated and performed by a single component. Similarly, the functions described herein as being performed by one component may be performed by multiple components in a distributed manner. Additionally, a component described as -9- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 performing particular functionality may also perform additional functionality not described herein. For example, a device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed.

[0044] In addition, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. For example, the use of “comprising,” “including,” “containing,” “having,” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Additionally, the terms “connected” and “coupled” are used broadly and encompass both direct and indirect connecting and coupling, and may refer to physical or electrical connections or couplings. Furthermore, the phase "and / or" used with two or more items is intended to refer to these items individually and together. For example, “a and / or b" is intended to mean: a (and not b); b (and not a); and a and b.

[0045] Power converters may include a transformer to provide isolation between the power converter and an AC source or load. However, such a transformer can add inefficiencies and size or volume to the power converter. Non-isolated power converters, also referred to as transformerless power converters, may experience unwanted signals or current (e.g., leakage current) from common mode voltages, which could discharge inadvertently and impact other coupled electronics or individuals. Additionally, three-phase AC system may experience unbalanced power across phases. Such unbalanced phases can lead to large (undesirable) circulating currents in the system.

[0046] In some examples, AC / DC power converters provided herein include a bridge circuit and LC filter for each AC phase of an AC system and for a neutral leg of the AC system, and employ delta-sigma-based control. By including a half bridge on the neutral leg, the AC / DC converter system can actively control current and voltage on the neutral leg and, thus, common mode current and voltage in the system. Further, the active control can balance an otherwise unbalanced three-phase AC system without use of an isolating transformer. Accordingly, the active control can provide a balanced system and can avoid, for example, hazardous voltages on the AC / DC converter. Still, in some examples, an isolating transformer can be provided to connect the AC / DC converter system to the three-phase AC system.

[0047] Some converter systems include both an AC / DC converter and a DC / DC converter, where the DC / DC converter may boost or buck a DC voltage received by the -10- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 DC / DC converter for use by the AC / DC converter (when inverting) or the DC / DC converter may boost or buck a DC voltage received from the AC / DC converter (when rectifying) to provide DC voltage at a desired level for a downstream DC device (e.g., for charging a battery). The DC voltage provided to the DC / DC converter may sometimes be within an acceptable range of the AC / DC converter or downstream device to use (i.e., boosting and bucking the voltage is not necessary). However, in some systems, the DC / DC converter is active nonetheless, adding a conversion stage and reducing efficiency of the system. Accordingly, in some examples provided herein, the DC / DC converter is selectively enabled or bypassed, depending on the input DC voltage level and the desired output DC voltage level.

[0048] Some converter systems that include both an AC / DC converter and a DC / DC converter may include an isolating transformer in the DC / DC converter, which may serve to provide isolation for both the DC / DC converter and the AC / DC converter. However, if such a DC / DC converter were bypassed to increase efficiency as described above, the isolating transformer would also be bypassed. In some examples provided herein, both the DC / DC converter and the AC / DC converter are transformerless and control common mode voltages and / or currents using other techniques (e.g., delta-sigma-based control). Accordingly, selectively bypassing the DC / DC converter to provide improved conversion efficiencies is acceptable within the converter system, without including a separate isolating transformer, a large common mode choke, and / or large capacitances Cy in the AC / DC converter to mitigate or reduce common mode voltages and currents in the system.

[0049] Additionally, in some examples, a DC / DC converter is provided that is controlled using differential mode (DM) and common mode (CM) variable decomposition. For example, a control system may control the DC / DC converter using Delta-Sigma-based control. Using Delta-Sigma control, as described herein, enables control of DC bus voltage with respect to a chassis ground (e.g., of an electric vehicle having the DC / DC converter as part of an on-board charger).

[0050] Some converter systems are designed for use with particular AC and / or DC systems. For example, some converter systems for charging electric vehicle batteries are designed for us with the US electrical grid, while others are designed for use with a Japanese, German, or Chinese electrical grid. Still further, some converter systems are designed for a single-phase grid connection, while others are designed for a three-phase grid connection or -11- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 split phase connection. Such converter systems are rigid and may limit usage options for users or require users to seek out particular converter systems for charging or the like. In some examples, power converters provided herein are reconfigurable to be usable with different types of AC systems, such as, for example, three-phase, single-phase, and split- phase AC systems. The power converters may be suitable for operation with various types of utility grids in various geographic locations (e.g., the United States, Japan, Germany, China, etc.).

[0051] Some embodiments described herein address these and / or other issues. For example, some embodiments described herein provide power converter systems, methods, and media that use delta-sigma-based control of an AC / DC converter to, for example, actively control common mode current and / or voltage on a neutral leg of a three-phase AC system. Some embodiments described herein provide power converter systems, methods, and media that use Delta-Sigma-based control of a DC / DC converter. Some embodiments described herein provide reconfigurable power converter systems, methods, and media that enable an AC / DC converter to operate in a three-phase mode, a single-phase mode, or split-phase mode. Some embodiments described herein provide power converter systems, methods, and media that combine two or more of delta-sigma-based control of an AC / DC converter, Delta- Sigma-based control of a DC / DC converter, and / or reconfigurable power converter systems.

[0052] Accordingly, disclosed herein are systems, methods, and media related to power converters, also referred to as voltage converters, that can implement delta-sigma- based control of an AC / DC converter, Delta-Sigma-based control of a DC / DC converter, and / or reconfigurable power converters.

[0053] FIG. 1 illustrates a power converter system 100 in accordance with some embodiments. The power converter system 100 includes a control system 105, a first load / source 110, a power converter 115, an LC filter 120, a second source / load 130, and one or more sensors 140. The control system 105 includes a central controller 150 with an electronic processor 155 and a memory 157, and, optionally, in some embodiments, includes one or more local controllers 160, each having an electronic processor 165 and a memory 167. The power converter system 100, as well as the other power converter systems provided herein, may be non-isolated power converter systems. That is, the power converter -12- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 system may be coupled to an AC source (e.g., single, three, or split phase power grid) or AC load (e.g., single-, three-, or split-phase motor) without a transformer. Use of a transformer is common in electrical circuits to provide isolation between the power converter and an AC source or load. However, such a transformer can add inefficiencies and size or volume to the power converter. Accordingly, power converter systems provided herein may be non- isolated, also referred to as transformerless, to increase efficiency and / or reduce size of the power converter systems. Because such power converters are provided without isolation by a transformer, the power converters may include additional features to prevent transmission of unwanted signals or current (e.g., leakage current) from passing between the power converters and other circuit components (e.g., DC sources, DC loads, AC sources, AC loads, and other structures in contact with or supporting the power converters). These additional features may include LC filters for each bridge circuit, active control of common mode voltage and / or current via a half bridge circuit on a neutral leg of a three-phase AC system, active control of DC bus voltage of a power converter, and the like described herein. In some examples, however, a transformer may be included to provide an isolated power converter in which the power converter 115 is coupled to an AC source or load via a transformer.

[0054] In operation, generally, the control system 105 controls power switching elements of the power converter 115 with control signaling (e.g., pulse-width modulated (PWM) signals) to convert power (i) from the DC load / source 110 functioning as a source to the second source / load 130 functioning as a load, or (ii) from the second source / load 130 functioning as a source to the DC load / source 110 functioning as a load. Accordingly, when the DC load / source 110 is functioning as a source for the power converter 115, the second source / load 130 is functioning as a load for the power converter 115. Conversely, when the DC load / source 110 is functioning as a load for the power converter 115, the second source / load 130 is functioning as a source for the power converter 115.

[0055] The DC load / source 110 may be a direct power (DC) load, a DC source, or both a DC load and DC source (i.e., functioning as DC source in some instances and as a DC load in other instances, depending on the mode of the power converter 115). In some examples, the DC load / source 110 is a battery including one or more battery cells (e.g., an electric vehicle battery or backup power battery). In other examples, DC load / source 110 may be a -13- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 capacitor, an ultracapacitor, a DC power supply from rectified AC source (e.g., AC grid power converted to DC power by diode bridge rectifier), or the like. The second source / load 130 may be an AC load, an AC source, both an AC load and AC source (i.e., functioning as an AC source in some instances and as an AC load in other instances, depending on the mode of the power converter 115). In some examples, the second source / load 130 may be an electric (AC) motor, an AC generator, AC power supply grid, or the like. In some examples, such as where the power converter 115 is a DC / DC converter, the second source / load 130 is a DC load, a DC source, or both a DC load and a DC source (i.e., functioning as DC source in some instances and as a DC load in other instances, depending on the mode of the power converter 115).

[0056] The DC load / source 110 is coupled to the power converter 115 at a first (DC) side or section of the power converter 115, and the second source / load 130 is coupled to the power converter 115 at a second side or section of the power converter 115. The first side may also be referred to as an input side or an output side of the power converter 115, depending on the mode of the power converter, or as a DC side of the power converter 115. The second side may also be referred to as an input side or an output side of the power converter, depending on the mode of the power converter, or as an AC side, second DC side, or filter side of the power converter 115. In some embodiments, the second side of the power converter 115 may be an AC side having single-phase AC power, three-phase AC power, or AC power with another number of phases.

[0057] In some embodiments, the power converter 115 operates with a high DC voltage level. For example, in operation, the DC side of the power converter 115 has a DC voltage (e.g., across input terminals of the power converter 115) of at least 200 V, at least 600 V, at least 800 V, at least 1000 V, at least 1200 V, between 200 V and 1200 V, between 600 V and 1200 V, between 800 V and 1200 V, or another range. Such high DC voltage levels may be desirable in some contexts, such as some electric vehicles. For example, some current electric vehicles (e.g., passenger vehicles and hybrid electric vehicles) operate with a DC bus voltage of between about 200 V and 400 V. This DC bus voltage for passenger electric vehicle may increase in the future. Further, some current electric vehicles (e.g., class 4-8, off-road, or otherwise larger electric vehicles) can operate with a DC bus voltage of more than 1000 V. However, high DC voltage levels may introduce challenges into a typical power converter -14- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 system, such as an increase in leakage currents, increases in common mode voltage, higher rates of change in common mode voltage, and the like. These challenges can lead to resonance on the LC filter 120, shaft voltages, excessive bearing currents (e.g., from discharge events when lubricant dielectric breakdown occurs) that can result in bearing failures, excessive motor shaft currents, excessive motor winding currents (e.g., insulation may be damaged), and excessive gear train currents (e.g., bearing currents can propagate into the gear train via electromagnetic interference (EMI) or noise, vibration, harshness (NVH) resulting from the damaged bearing race walls). Embodiments described herein, however, can mitigate such challenges through LC filters and control techniques described herein.

[0058] The LC filter 120 may include an LC filter for each phase and / or each phase leg of the power converter 115. Each LC filter may include at least an inductor and a capacitor, or at least an inductor and two capacitors, as illustrated in further detail, for example, in FIGS. 2, 3 (see, e.g., a switch-side filter inductor Lf, upper capacitor cf,up, and lower capacitor cf,lo, for each phase leg), as well as FIGS.4A, 4B, 5, 10A, 10B, 11, 12 ,17A-D, 18A-D, 19A-B, 22, and 23.

[0059] The sensor(s) 140 include, for example, one or more current sensors and / or one or more voltage sensors. For example, the sensor(s) 140 may include a respective current sensor and / or voltage sensor to monitor a current and / or voltage of one or more of the DC load / source 110, each phase or phase leg of the second source / load 130, each phase of the LC filter 120, or other nodes or components of the power converter 115. For example, when the LC filter 120 is a four-leg LC filter, the sensors 140 may include at least four current sensors, one for sensing current at each leg of a three leg LC filter 120. In some embodiments, additional or fewer sensors 140 are included in the power converter system 100. For example, the sensors 140 may also include one or more vibration sensors, temperature sensors, and the like. In some examples, the control system 105 infers a characteristic (e.g., current or voltage) of the power converter 115, rather than directly sensing the characteristic. The sensor(s) 140 may provide sensor data to the control system 105 indicative of the sensed characteristics of the power converter system 100. Such sensor data may, accordingly, indicate electrical operational characteristics of the power converter system 100. In some examples, the control system 105 infers or estimates a characteristic -15- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 (e.g., current or voltage) at one or more nodes of the power converter 115 based on the sensor data of a sensor of sensors 140 that senses a different type of characteristic or even a different component, rather than directly sensing the characteristic.

[0060] The input-output (I / O) interface 142 includes or is configured to receive input from one or more inputs (e.g., one or more buttons, switches, touch screen, keyboard, and the like), and / or includes or is configured to provide output to one or more outputs (e.g., LEDs, display screen, speakers, tactile generator, and the like). Other electronic devices and / or users may communicate with the power converter system 100 and, in particular, the control system 105, via the I / O interface 142. For example, the control system 105 may receive commands (e.g., from a user or another device) for the power converter system 100 indicating a target torque, target speed, target power level, conversion type, or the like. The control system 105, in response, may drive the power converter 115 to achieve the target and / or conversion type indicated by the command. For example, in some examples, the control system 105 may convert the commands to a DC bus reference voltage (Vdc*) and a reactive power reference (Q*) that the control system 105 then uses as reference targets for controlling the power converter 115.

[0061] The control system 105 generally monitors the power converter system 100 including the power converter 115 (e.g., based on sensor data from the sensor(s) 140), receives commands (e.g., via the I / O interface 142 or a memory 157, 167), and controls the power switching elements of the power converter 115 with control signaling (e.g., pulse- width modulated (PWM) signals) to convert power (e.g., in accordance with the sensor data and / or the commands). In some embodiments, the control system 105 includes a controller (e.g., the central controller 150) that performs this monitoring and control without additional local controllers. In other embodiments, the control system 105 is a cascaded control system including a central controller 150 and one or more local controllers 160. The cascaded control system may communicate in real time (e.g., each control cycle) monitoring information (e.g., sensor data) and control information between the central controller 150 and the one or more local controller 160. In some examples, the local controller(s) 160 each implement model predictive control (MPC) or another regulation control scheme (e.g., PID control, PI control, or the like). In some examples, the central controller implements a non- -16- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 MPC regulation technique, such as proportional integral derivative (PID) control or proportional integral (PI) control.

[0062] Each controller of the control system 105, including the central controller 150 and the local controllers 160, is an electronic controller that may include an electronic processor. Such an electronic controller may further include a memory (e.g., the memory 157 or 167). The memory is, for example, one or more of a read only memory (ROM), random access memory (RAM), or other non-transitory computer-readable media. The electronic processor 155, 165 is configured to, among other things, receive instructions and data from the memory 157, 167 and execute the instructions to, for example, carry out the functionality of the associated controller described herein, including the processes described herein. For example, the memory may include control software. In some embodiments, instead of or in addition to executing software from the memory to carry out the functionality of the controller described herein, the electronic processor includes one or more hardware circuit elements configured to perform some or all of this functionality. For example, the electronic processor 155, 166 may be or include an application specific integrated circuit (ASIC) or field programmable gate array (FPGA). Additionally, although a particular controller, electronic processor, and memory may be referred to as a respective, single unit herein, in some embodiments, one or more of these components is a distributed component. For example, in some embodiments, an electronic processor includes one or more microprocessors and / or hardware circuit elements. The electronic processor(s) as described herein, including the electronic processors 155, 166, may also be referred to as processing unit(s).

[0063] In some examples, the control system 105 can include and implement multiple different converter control schemes to control the power converter 115 in different converter operational modes. For example, the control system 105 can implement an AC / DC converter operational mode selected from a plurality of different AC / DC converter operational modes when the power converter 115 includes an AC / DC converter, can implement a DC / DC converter operational mode selected from a plurality of different DC / DC converter operational modes when the power converter 115 includes a DC / DC converter, or can implement both an AC / DC converter operational mode and a DC / DC converter operational mode when the power converter includes both an AC / DC converter and a DC / DC converter. Example AC / DC converter operational modes that can be implemented by the -17- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 control system 105 include an asymmetric (delta-sigma) three-phase operational mode (see, e.g., the control system 505 of FIG.5 and the process 700 of FIG.7), a symmetric three-phase operational mode, an symmetric split-phase operational mode (see, e.g., the control system 2305 of FIG.23), an asymmetric split-phase operational mode, and a single phase operational mode (see, e.g., the control system 2205 of FIG.22). Example DC / DC converter operational modes that can be implemented by the control system 105 include a DC / DC Delta-Sigma operational mode (see, e.g., the control system 1205 of FIG.12 and the process 1400 of FIG. 14) and a half-bridge DC / DC operational mode (e.g., for controlling the DC / DC converter of FIG. 10B). The control system 105 may further be reconfigurable to select one or both an AC / DC operational mode and a DC / DC operational mode depending on the converter(s) currently coupled to the control system 105, the types of AC systems currently coupled to the AC / DC converter (e.g., three-phase, split-phase, or single-phase), among other factors (e.g., user input, sensor data, etc.).

[0064] FIG.2 illustrates an example of a half-bridge converter 200 that may serve as a building block for the power converter 115 of the power converter system 100 of FIG.1. As illustrated, the half-bridge converter 200 includes DC terminals 220 (also referred to as DC nodes, DC links, DC rails, etc. of a DC bus) having a positive DC terminal 222 and a negative DC terminal 224. The half-bridge converter 200 further includes interface terminals 225 (also referred to as interface nodes or AC connection nodes) having a first interface terminal 227 and second interface terminal 229. The half-bridge converter 200 may be operated as a bidirectional converter or as a unidirectional converter (in either direction), depending on the configuration and control of the system in which it is implemented. Accordingly, the DC terminals 220 may be input terminals and the interface terminals 225 may be output terminals in some examples (e.g., DC / DC conversion and DC / AC inversion), and the DC terminals 220 may be output terminals and the interface terminals 225 may be input terminals in some examples (e.g., AC / DC rectification). Additionally, the interface terminals 225 may be AC input terminals (e.g., for AC / DC rectification), may be AC output terminals (e.g., for a DC / AC inverter), or may be DC output terminals (e.g., for DC / DC conversion).

[0065] The half-bridge converter 200 further includes a DC link capacitor (CDC) 230, a, a high side (upper) power switching element (M1) 235 (also referred to as high-side or upper switch 235), a low side (lower) power switching element (M2) 240 (also referred to -18- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 as low-side or lower switch 240), a midpoint node 242 connecting a drain terminal of upper switch 235 and a source terminal of lower switch 240, and an LC filter 245. The LC filter 245 is an example of the LC filter 120 (FIG.1), or a portion thereof.

[0066] The power switching elements 235 and 240 may be field effect transistors (FETs), each having a respective gate, source, and drain terminal. The FETs may be, for example, a MOSFET, a silicon carbide (SiC) FET, a gallium nitride (GaN) FET, among other types of FETs.

[0067] The LC filter 245 includes a switch-side inductor Lf 250, a lower capacitor Cf,low 255, and an upper capacitor Cf,up 215. The switch-side inductor Lf 250 is coupled between the midpoint node 242 and a filter node 260. For example, a first end of the switch-side inductor Lf250 is coupled to the midpoint node 242, and a second end is coupled to the filter node 260. The lower capacitor Cf,low255 is coupled between the filter node 206 and the negative DC terminal 224. For example, a first end of the lower capacitor Cf,low255 is coupled to the filter node 260, and a second end is coupled to the negative DC terminal 224. The upper capacitor Cf,up 215 is coupled between the filter node 260 and the positive DC terminal 222. For example, a first end of the lower capacitor Cf,up 215 is coupled to the filter node 260, and a second end is coupled to the positive DC terminal 222.

[0068] In some examples, the LC filter 245 is an LCL filter (an LC filter with an additional inductor (L)), in which an additional (interface) inductor is coupled between the filter node 260 and the positive interface terminal 227.

[0069] In some examples, the converter further includes drain-source capacitors CDS265a and 265b, each respectively coupled across one of the switches 235, 240. In particular, a first drain-source capacitor 265a is provided across a source terminal 270a and drain terminal 275a of the upper switch (M1) 235, and a second drain-source capacitor 265b is provided across a source terminal 270b and drain terminal 275b of the lower switch (M2) 240. The drain-source capacitors (CDS) 265a-b may be generically and collectively referred to herein as drain-source capacitor(s) (CDS) 265. The drain-source capacitors (CDS) 265 can slow a voltage rise during an ON-to-OFF transition of the switches 235 and 240. This slowed voltage rise can, in turn, reduce the switching losses of the switches 235 and 240. In some examples of the half-bridge converter 200, one or both of the upper capacitor Cf,up215 and the drain-source capacitors CDSare not included in the half-bridge converter 200. -19- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272

[0070] As noted, in some examples, the half-bridge converter 200 may serve as a building block for the power converter 115 of the power converter system 100 in FIG.1. For example, multiple instances of the half-bridge converter 200 are paralleled or connected to collectively serve as an AC / DC converter or DC / DC converter of the power converter 115 of FIG. 1. Examples of such AC / DC converters and DC / DC converters including one or more instances of the half-bridge converter 200 are provided herein (see, e.g., FIGS.3, 5, 10A, 10B, 11, 12, 17A-D, 18A-D, 19A-B, 22, and 23). As used herein, a converter block may refer to a half bridge circuit such as described with respect to the half-bridge converter 200 of FIG.2. For example, a converter block may include the power switching elements 235 and 240, the LC filter 245 (including upper capacitor Cf,up 215, if present, and additional interface inductor, if present), the interconnecting nodes thereof (e.g., midpoint node 242, filter node 260, DC terminals 220, and interface terminals 225), and (if present) drain-source capacitors 265.

[0071] FIG. 3 illustrates four-leg power converter system 300. The system 300 includes an AC system 302, a four-leg power converter 304, and a DC system 306. With reference to FIG.1, the AC system 302 is an example of the second load / source 130, the four- leg power converter 304 is an example of the power converter 115 and LC filter 120, and the DC system 306 is an example of the DC load / source 110.

[0072] As illustrated in FIG.3, the DC system 306 includes a DC battery 310 and a DC bus capacitor (CDC) 312 (similar to the DC link capacitor CDC 230 of FIG.2), and the DC system 306 is coupled to the four-leg power converter 304 via a DC bus 314 (similar to DC terminals 220) with positive and negative terminals. The AC system 302 is a three-phase AC grid including a first AC leg or phase 320a, a second AC leg or phase 320b, a third AC leg or phase 320c, and a neutral leg 320d connected at a node 322. The AC system 302 is coupled to the four-leg power converter 304 via a point of common coupling (PCC) 326, which may include terminals, connectors, or the like connecting each leg 320a-d of the AC system 302 to a respective leg of the four-leg power converter 304 (in particular, to a filter node of each leg). The inductors Lfg,abcn illustrated along the conductors or wires between the PCC 326 and the respective filter nodes of each leg may be discrete inductor components or may represent inherent inductances of the conductors. -20- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272

[0073] The four-leg power converter 304 includes four legs, with each leg including a half-bridge converter similar to the half-bridge converter 200 of FIG. 2. Accordingly, the discussion with respect to the half-bridge converter 200 similarly applies to each leg of the four-leg power converter 304. Thus, for example, each leg of the four-leg power converter 304 includes a pair of power switching elements connected by a midpoint node and coupled across DC terminals (DC bus 314), and includes an LC filter coupled to the power switching elements by the midpoint node, to the filter node (also referred to as AC connection nodes 330a-330d), and to the DC bus 314.

[0074] As explained in further detail below, in some examples, a DC / DC converter is further included between the DC system 306 and the four-leg power converter 304 to boost and / or buck DC voltage between the components (see, e.g., FIGS.10A, 10B, 11, 17A-B, 18A- D, 19A-D, 22, and 23). In such examples, the DC / DC converter and the four-leg power converter 304 together may collectively be an example of the power converter 115 (see FIG. 1). In some examples, the DC / DC converter is selectively coupled and enabled using contactors (see, e.g., FIG.11). Further, in some examples, the AC system 302 is a single-phase AC system and the four-leg power converter 304 is operated as a single-phase converter (see, e.g., FIG.17B, 18B, 19B, 22), with or without a DC / DC converter coupling the four-leg power converter 304 to the DC system 306; or the AC system 302 is a split-phase AC system and the four-leg power converter 304 is operated as a split-phase converter (see, e.g., FIG. 17C-D, 18C-D, 23), with or without a DC / DC converter coupling the four-leg power converter 304 to the DC system 306.

[0075] In some examples, the four-leg power converter 304 is controlled by a control system (e.g., the control system 105) that may take into account the presence of the fourth leg coupled to the neutral leg 320d, which enables control of neutral leg current and, thus, control of each of the three phase-to-neutral (PTN) voltages independently. To perform such control, the control system 105 may use a dqδσ reference frame, through the use of a modified Clarke-Park transformation. As explained further below, the dqδσ reference frame is a rotational or synchronous reference frame that includes a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐ axis) component. The direct axis and quadrature axis components are similar to the direct axis and quadrature axis of a dqn reference frame that can be obtained using the Clarke-Park -21- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 transformation. The delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter. The sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic. For example, the sigma axis component may be the sum of the common mode electrical characteristic and the neutral electrical characteristic or an average of the common mode electrical characteristic and the neutral electrical characteristic (as the average is a scaled version of the sum and, thus, indicative of the sum).

[0076] Starting from the phase domain, state-space equations for the abcn system can be expressed as: ^^^^^,^^^^ ൌ^ ^^^^^^௫,^^^^െ ^ ^^^^^^^,^^^^(1a)where ^^^,^^^^is the inductor current, ^^^,^^^^is the voltage at the output of the inverter, ^^௫,^^^^is the voltage across the capacitor, ^^^,^^^^is the grid current, and ^^^,^^^^is the grid voltage.The matrix ^^ ∈ ℝସൈସ is the identity matrix. Lf, Cf, and Lg are the ϐilter inductance, ϐiltercapacitance, and grid inductance, respectively.

[0077] To transform from a standard or stationary abcn reference frame to the dqδσ reference frame, a modified Clarke-Park transformation may be used. Taking voltage as an example characteristic for transformation, the modified Clarke-Park transformation may include an extended Clarke transformation as follows: 1െ^^é െ0 ^^ ù ) where theby adding an extra component ^^௭, which represents the neutral voltage without a scaling factor. Thus, this -22- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 operation retains the characteristics of the standard three-phase system while incorporating the neutral conductor, thereby defining a new reference system that we denote as αβ0z. Then, the dq0 Park transformation is modified into the following version: ^^ௗécos^^ sin^^ 0 0െsin^^ cos^^ù ^^ఈ^^ఈ^^^^^^ê0 0^ ^ú^^^^ ^^^^^where ^^ sequencea the three-phase average voltage and the neutral voltage, and a ^^ఙvariable, whose value represents the sum of the three-phase average voltage and the neutral voltage.

[0078] Similarly, to transform from the dqδσ reference frame to the standard or stationary abcn reference frame, an inverse of this modified Clarke-Park transformation may be used. Additionally, while this transformation is illustrated for transforming voltage, the same transformation may be applied to transform current (i.e., from IABCD to Idqδσ, where each instance of “V” in the equations (2) and (3) is replaced with “I”). As with voltage, the d and q components are similar to a typical dq reference frame,the ^^ component represents the differential-mode current across the three-phases and the neutral, and the ^^ component represents the common-mode current of the three-phases and the neutral.

[0079] These transformations derive from the common and differential mode signal decomposition, as explained graphically in FIGS.4A-4B. FIGS.4A-4B illustrate the differential (^^) and common (^^) mode current decomposition for the four-leg power converter 304, where the half-bridge converter for each of the four legs is illustrated (i.e., as half-bridge converter for each phase leg 402a, 402b, 402c, and 402n, respectively). More particularly, FIG. 4A illustrates the delta axis current component ^^ఋindicating a difference between a common mode current and a neutral leg current of the four-leg power converter 304, where the ^^ఋcomponent is generated by a difference between the three-phase zero sequence voltage (^^^) and the neutral voltage (^^௭). The delta axis current component ^^ఋenables control of the current flowing throughneutral. FIG. 4B illustrates the sigma axis current component ^^ఙindicating a sum of the common mode current and the neutral leg current, -23- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 where the ^^ఙterm represents the control of the common-mode voltage of the four legs, working as a zero-sequence control.

[0080] A control system may control the four-leg power converter 304 in the ^^^^^^^^ domain. For example, turning to FIG. 5, a power converter system 500 is illustrated. The power converter system 500 includes the four-leg power converter 304 and a control system 505. With reference also to FIG. 1, the power converter system 500 is an example of the power converter system 100 and the control system 505 is an example of the control system 105. In the diagram of FIG.5, to simplify the control, the grid‐side filtering inductor and the grid inductance are merged together into one lumped component ^^^inserted on the grid side.

[0081] Generally, the control system 505 senses electrical operational characteristics for the four-leg power converter 304, uses the modified Clarke-Park transformation described above to generate control reference targets based in the dqδσ reference frame, and controls the four-leg power converter 304 based on the control reference targets. The control system 505 includes a first transformation block 510 to translate received electrical characteristics from the stationary abcn reference frame to the dqδσ reference frame, a phase-locked‐loop (PLL) block 512 to generate a phase angle (theta, θ), a DC bus control block 514, a reactive power control block 516, control blocks 518a-d (including grid current control blocks 518a-c and voltage control block 518d), a second transformation block 520, and a variable frequency critical soft switching (VFCSS) block 522.

[0082] FIG.6 illustrates a subset 600 of the control system 505 including the second transformation block 520 and the VFCSS block 522. More particularly, in FIG.6, the second transformation block 520 is illustrated as including a delta-sigma translator 520a and four regulators 520b, one regulator 520b for each leg of the power converter system 500.

[0083] Further, the VFCSS block 522 is illustrated as having a VFCSS sub-block 522a and a switch driver 522b, one for each leg of the power converter system 500. The regulator 520b, VFCSS sub-block 522a, and switch driver 522b for each phase may be implemented on a respective one of local controllers 660a, 660b, 660c, 660n (also referred to as the local controllers 660a-n). The local controllers 660a-n may be an example of the local controllers 160 of FIG. 1. The delta-sigma translator 520a and remaining components of the control -24- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 system 505 illustrated in FIG.5 (aside from the VFCSS block 522) may be implemented on a central controller, such as, for example, the central controller 150 of FIG.1. Each of the local controllers 660, 160 and central controller 150 may be implemented by separate hardware (e.g., a separate microprocessor, FPGA, etc.) or one or more of these controllers may be virtual controllers that share hardware (e.g., implemented on the same microprocessor, FPGA, etc.). In some examples, the switch drivers 522b are implemented as hardware components that are separate from the local controllers 660a, 660b, 660c, 660n.

[0084] An example operation of the power converter system 500 is described in further detail with respect to FIG.7. FIG. 7 illustrates a process 700 for converting voltage using a four-leg converter with a delta-sigma-based control is illustrated. The process 700 is described as being carried out by the power converter system 100 implemented as the power converter system 500 of FIG.5. However, in some embodiments, the process 700 is implemented by another power converter system or by the power converter system 100 implementing another power converter system (e.g., the AC / DC converter 1015 of FIG.11, the reconfigurable system 1700 of FIGS.17A-B, the reconfigurable system 1800 of FIGS.18A- B, the reconfigurable system 1900 of FIGS.19A-B, and the power converter system 2600 of FIG.26). Additionally, although the blocks of the process 700 are illustrated in a particular order, in some embodiments, one or more of the blocks may be executed partially or entirely in parallel, may be executed in a different order than illustrated in FIG.7, or may be bypassed.

[0085] In block 705, a control system determines at least one electrical operational characteristic for each of four phase legs of a four-leg power converter, where the four-leg power converter includes a direct current (DC) voltage section including a DC bus and an^ alternating current (AC) voltage section including AC connection nodes, and the four phase legs includes a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg each having a respective LC filter and respective power switching elements. For example, with reference to FIG.5, the control system 505 determines at least one electrical operational characteristic for each phase leg 402a, 402b, 402c, and 402n of the four-leg power converter 304 (also referred to as phase legs 402a-n). With continued reference to FIG.5, the electrical operational characteristic may include, for example, one or more of inductor current Il,abcn (current through the inductor of each LC filter), grid voltage Vg,abcn(voltage across the lower capacitor of each LC filter), and / or grid current Ig,abcn. The control system 505 may obtain -25- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 these electrical operational characteristics via one or more sensors (e.g., the sensors 140 of FIG.1). In block 705, the control system 505 may further receive a DC bus voltage (VDC), a DC bus current (IDC), a reactive power (Q), among other electrical characteristics for the four-leg power converter 304 (e.g., via the sensors 140 of FIG.1).

[0086] In block 710, the control system generates control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and on a rotational reference frame. In block 710, the control reference targets include a respective control reference target for each of the four phase legs, and the rotational reference frame includes a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component. For example, with reference to FIG.5, the control system 505 translates the at least one electrical operational characteristics (e.g., inductor current (Il,abcn), grid voltage (Vg,abcn), and / or grid current (Ig,abcn)) from the stationary abcn reference frame to the rotational dqδσ reference frame using the first transformation block 510. The first transformation block 510 may represent the modified Clarke-Park transformation described above, which the control system 505 may execute via the transformation block 510 to transform the input electrical operational characteristics (inductor current (Il,abcn), grid voltage (Vg,abcn), and / or grid current (Ig,abcn)) to the rotational dqδσ reference frame. In some examples, one or more of the transformation sub-blocks of the first transformation block 510 illustrated (e.g., the inductor current (Il,abcn) transformation sub-block) are not included. The control system 505 may also determine the phase angle theta (θ) of the grid using the PLL block 512 based on Vg,q* (output by the grid q current control block 518b) and sensed Vg,q. See also discussion of FIG. 25 for additional details on an example of the PLL block 512. The first and second transformation blocks 510 and 520 may use the phase angle theta (θ) as part of the respective transformations of these blocks.

[0087] The DC bus control 514 receives a reference DC bus voltage (VDC*) for the DC bus 314 and a sensed DC bus voltage (VDC), and generates a reference grid d‐current (Ig,d*) based on the difference therebetween. For example, the control system 505 may generate the reference grid d-current to control the grid d-current based on the DC bus control block 514 to keep the DC bus voltage stable and deliver the desired or required active power. The reference DC bus voltage (VDC*) may be obtained from a memory (e.g., the memory 157) or -26- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 input via an I / O interface (e.g., the I / O interface 142). This d-loop control may be used to control the active power flow by setting the reference grid d-current (Ig,d*).

[0088] The reactive power control 516 receives a reactive power reference (Q*) and a reactive power (Q) for the converter 304, and generates a refence grid q-current (Ig,q*) based on the difference therebetween. In some examples, the reactive power control 516 is not included or idle, and the reference grid q-current (Ig,q*) is set to zero; but, in other examples, the reference grid q-current (Ig,q*) may be set to a non-zero value according to the output of the reactive power control 516. This q-loop control may be used to control the reactive power flow by setting the reference grid q-current (Ig,q*).

[0089] In some examples, the control system 505 the grid delta current ^^^,ఋto be zero by setting the reference grid delta current ^^^,ఋ* to zero, for example, to set the current through the neutral conductor to zero to simulate a balanced three-phase scenario. In some examples, the control system 505 sets the reference grid delta current ^^^,ఋ* to a non- zero value to control unbalanced conditions or applications where the neutral is used as return conductor. This δ‐loop control may be used to control the neutral current, which may be implemented, for example, for unbalanced or asymmetric conditions.

[0090] In some examples, the control system 505 also controls the grid sigma voltage (^^^,ఙ) to be stable at half of the voltage of the DC bus 314 by setting the reference grid sigma voltage (^^^,ఙ*) to be at half of the voltage of the DC bus 314, to avoid leakage flowing back to the grid because the zero-sequence current will be captured by the bypassing capacitors. This σ‐loop control may be used to control the common-mode voltage by keeping thereference grid sigma voltage (^^^,ఙ*) at a fixed value (e.g., ^^^^ ോ 2) to minimize or reduceleakage current circulation.

[0091] Error blocks 524a-d may receive the reference values Ig,d*,^Ig,q*,^Ig,δ*,^VDC* / 2, respectively, and compare to an actual value (Ig,d,^Ig,q,^Ig,δ,^Vg,σ) output by the transformation block 510, and generate an error signal (eg,d,^eg,q,^eg,δ,^eg,σ) to provide to the control blocks 518a-d. The control blocks 518a-d may then generate voltage reference values Vg,d*,^Vg,q*,^ Vg,δ*,^Vg,σ*, respectively, and provide these reference values to the second transformation block 520. For example, each of the control blocks 518a-d may be a regulator (e.g., implementing PID control, PI control, or the like) that generates voltage reference values, -27- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 based on a received error signal to ultimately cause the control system 505 to drive the power converter system 500 such that the actual values (Ig,d,^Ig,q,^Ig,δ,^Vg,σ) track the reference values Ig,d*,^Ig,q*,^Ig,δ*,^VDC* / 2.

[0092] The voltage reference values Vg,d*,^Vg,q*,^Vg,δ*,^Vg,σ* are control reference targets in the rotational dqδσ reference frame (also referred to as rotational reference frame targets). The second transformation block 520 may ultimately translate the reference values into duty cycle values Da,^Db,^Dc,^Dn for a pulse-width modulated (PWM) signal (fsw,abcn) to drive the power switching elements of each leg of the four-leg power converter 304. FIG.6 illustrates a functional diagram of one example of the second transformation block 520. As part of the translation by the second transformation block 520 (and as part of block 710 of the process 700), the voltage reference values Vg,d*,^Vg,q*,^Vg,δ*,^Vg,σ* (control reference targets in the rotational dqδσ reference frame) may be translated to voltage reference values Vg,a*,^ Vg,b*,^Vg,c*,^Vg,n* (control reference targets in the stationary abcn reference frame).

[0093] With reference to FIG.6, the voltage reference values Vg,d*,^Vg,q*,^Vg,δ*,^Vg,σ* are provided to the delta-sigma translator 520a. The delta-sigma translator 520a may translate the voltage reference values from the rotational dqδσ reference frame to the stationary abcn reference frame. More particularly, the delta-sigma translator 520a may represent the modified inverse Clarke-Park transformation described above, which the control system 505 may execute via the delta-sigma translator 520a to transform the voltage reference valuesVg,d*,^ Vg,q*,^ Vg,δ*,^ Vg,σ* from the rotational dqδσ reference frame to the stationary abcnreference frame. The delta-sigma translator 520a may also receive the previously noted phase angle theta (θ) of the grid from the PLL block 512 for use in the modified inverse Clarke-Park transformation to perform the translation.

[0094] Accordingly, in block 710, the delta-sigma translator 520a of the control system 505 may generate the control reference targets Vg,a*,^Vg,b*,^Vg,c*,^Vg,n* in the stationary abcn reference frame, based on the at least one electrical operational characteristics and on the dqδσ rotational reference frame.

[0095] In block 715 of FIG.7, the control system may drive the power switching elements of the four phase legs in accordance with the control reference targets. For example, with reference to FIG. 5, the control system 505 may drive the power switching elements of the four phase legs 402a-n by outputting respective PWM signals 530 (having -28- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 duty cycle Dabcnand frequency fsw,abcn) to the power switching elements of each leg 402a-n of the four-leg power converter 304. For each leg 402a-n, the PWM signals of the PWM signals 530 may include a non-inverted PWM signal for a first power switching element (e.g., S1) and an inverted PWM signal for a second power switching element (e.g., S2), where the inverted PWM signal is inverted with respect to the non-inverted PWM signal (e.g., the inverted PWM signal is 180 degrees out of phase with respect to the non-inverted PWM signal), but has the same duty cycle and frequency. For example, for the phase leg 402a, the non-inverted and inverted PWM signal pair of the PWM signals 530 may have a duty cycle of Da and a frequency of fsw,a; for the phase leg 402b, the non-inverted and inverted PWM signal pair of the PWM signals 530 may have a duty cycle of Db and a frequency of fsw,b; for the phase leg 402c, the non-inverted and inverted PWM signal pair of the PWM signals 530 may have a duty cycle of Dcand a frequency of fsw,c; for the neutral phase leg 402n, the non-inverted and inverted PWM signal pair of the PWM signals 530 may have a duty cycle of Dnand a frequency of fsw,n.

[0096] By driving the power switching elements of the four phase legs, the four-leg power converter 304 converts power between AC and DC. For example, when in a rectification mode, in block 715, the four-leg power converter 304 may receive AC power from the AC system 302 and output DC power to the DC system 306. When in an inversion mode, in block 715, the four-leg power converter 304 may receive DC power from the DC system 306 and output AC power to the AC system 302. In some examples, the AC system 302 receiving the AC power is a three-phase AC grid (whether a utility grid or a local or microgrid), as illustrated in FIG.5; in other examples, a three-phase AC traction motor of an electric vehicle is coupled to the four-leg power converter 304 in place of the AC system 302. In some examples, contactors (e.g., relays, FETs, etc.) may be provided to selectively connect the four-leg power converter 304 via the AC connection nodes (e.g., the filter node of each phase leg 402a-n) to either the AC system 302 or the three-phase AC traction motor.

[0097] As shown in FIG. 5, the duty cycle (Dabcn) may be generated by the second transformation block 520, and the switching frequency (fsw,abcn ) may be generated by the VFCSS block 522. Turning to FIG. 6, additional details with respect to an example of generating the duty cycle (Dabcn) and the switching frequency (fsw,abcn ) are illustrated.

[0098] In FIG.6, one of the control reference targets Vg,a*,^Vg,b*,^Vg,c*,^Vg,n* output by the delta-sigma translator 520a are provided to each of local controllers 660a, 660b, 660c, -29- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 and 660n, respectively. More particularly, the control reference target Vg,a* is provided to the (Rega) regulator 520b of the local controller 660a, the control reference target Vg,b* is provided to the (Regb) regulator 520b of the local controller 660b, the control reference target Vg,c* is provided to the (Regc) regulator 520b of the local controller 660c, and the control reference target Vg,n* is provided to the (Regn) regulator 520b of the local controller 660n. Each regulator 520b further receives a corresponding sensed or actual grid voltage value Vg,a*,^Vg,b*,^Vg,c*,^Vg,n*, and generate a corresponding duty cycle Da, Db, Dc, Dn based on the received control reference target and the sensor or actual grid voltage value. For example, each of the regulators 520b may implement model predictive control (MPC) or another regulation control scheme (e.g., PID control, PI control, or the like) that provides an output duty cycle (Dabcd) based on a difference between an input reference target (e.g., Vg,abcd*) and an input actual value (e.g., Vg,abcd). Each regulator may generate an output (e.g., duty cycle Da, Db, Dc, Dn) to ultimately adjust the actual value (e.g., Vg,abcd) towards the input reference target (e.g., Vg,abcd*). For example, in some examples, the Regaregulator 520b determines or receives a difference between Vg,a* (an input reference target) and Vg,a (an actual value), and generates Da (an output duty cycle) to steer the actual value (Vg,a) to track (Vg,a*).

[0099] Further, in FIG.6, each local controller 660a-660d has a corresponding one of the VFCSS sub-blocks 522a. Each of the VFCSS sub blocks 522a may receive the duty cycle Da, Db, Dc, or Dn generated by the corresponding regulator 520b, along with an inductor current (IL,a, IL,b, IL,c, IL,n) for each phase leg and the DC bus voltage (VDC). Each of the VFCSS sub-blocks 522a may output a respective frequency value as the switching frequency for a corresponding phase leg (e.g., Fsw,a, Fsw,b, Fsw,c, Fsw,nfor phase leg 402a, 402b, 402c, 402n).

[0100] The switching frequency is determined by the VFCSS sub-blocks 522a to enable the power switching elements of the phase legs 402a-402n to achieve soft-switching. By varying the switching frequency to achieve using soft-switching, as opposed to hard switching, high turn-on losses of the upper switch are substituted with low turn-off losses of the lower switch of each phase leg 402a-402n . More particularly, in some examples, to realize soft switching, the VFCSS sub-blocks 522a reshape the phase leg inductor current ripple such that the vertex and nadir points are positive and negative. The vertex and nadir point ripple value should be large enough to guarantee a full soft switching. With reference -30- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 to the half-bridge converter 200 of FIG. 2 (which is an example implementing of the half bridge of each of phase leg 402a), in the period when ^^^is turned on, the phase leg inductor current is discharging ^^^switch capacitor, ^^^ௌ265a. The ^^^zero voltage switching can be realized under the circumstance of ^^^ௌ265a being discharged before ^^^is on. Inthe same way, a direction from the phase inductor current is required tocompletely discharge ^^ଶswitch capacitor, ^^^ௌ265b, before ^^ଶis on.

[0101] The turn-on timing for switching transitions and the least required inductor current ripple may be determined by the discharge, ^^^^^d ^^^^௫f upper / lower switch output capacitors. The phase leg side inductor current vertex / nadir point values, ^^^,^ೌ^critical soft ^^^ switching operation can be expressed by the drain-source current through the upper and lower switches, ^^^ௌ,ெ^and ^^^ௌ,ெଶ, and the current through the upper and lower switch output capacitance, ^^^^ௌ,ெ^and ^^^^ௌ,ெଶ. The phase leg side inductor current ripple nadir point, ^^^,^^^s taken as an example for the derivation as below: ^^^,^^^ ൌ െ^^^ௌ,ெଶ ^ ^^^^ௌ,ெ^ െ ^^^^ௌ,ெଶ, (4)where the ^^^^ௌ,ெ^and ^^^^ௌ,ெଶare the derivative functions of upper / lower switch output capacitors, ^^^ௌ,ெ^and ^^^ௌ,ெଶ, and drain-source voltages, ^^^ௌ,ெ^and ^^^ௌ,ெଶ. ^^^^ௌ,ெ^can be expressed as: ^^ ,ெ^ ൌ ^^ௗ௩ವೄ,ಾభ^^ௌ ^ௌ,ெ^ௗ௧ . (5)

[0102] Then, with the integral calculation in each switching dead time period, ^^ௗ, the required ^^^,^^^specific dead time can be further expressed by the discharge, ^^^^^fupper / lower switch output capacitors as 0.5^^^,^^^^^ௗ ^ ^^^^^ ^ 0corresponding analyticalderivations of ^^^,^^^d ^^^^^e demonstrated as: ^^ ൌ െ^൫^ವೄ,ಾభା^ವೄ,ಾమ൯൫ௗ௩ವೄ,ಾమ൯^,^^^ ^^ௌ,ெଶ െௗ௧ , (6) and ^^^^^ ൌ ^்^^ ^^^^,^^^ െ ^^^ௌ,ெଶ^^^^^ ^^^^ ൌ ^^^^^ െ ^^^^ௌ,ெ^^^^^ௌ,ெଶ^ ^ ^^^ௌ,ெଶ^^^^ௌ,ெଶ^^ ^^^^^ௌ,ெଶ ൌM2 switch datasheets, and dead time can be pre-defined, the minimum current ripple can then be derived to achieve the soft switching by variable switching frequency. -31- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272

[0104] Thus, the VFCSS controller may receive the inductor current (iL), dc rail voltage (vdc), and inductance of the inductor (Lf), and duty cycle from the MPC controller 410, and determine from these inputs a switching frequency (fsw) to achieve soft switching by the four-leg power converter 304.

[0105] Accordingly, the desired switching frequency (fsw) may be derived according to a threshold current, ^^௧^, of soft switching operation criteria. The phase leg side inductor current ripple, Δ^^^, can be demonstrated as Δ^^ ൌ ௗ^^ିௗ^௩^^^^ೞ^^. (8) and the soft switching operation and nadir points of the phase legside inductor current values to than -^^௧^. Thus, the derivation of the time-varying switching frequency, ^^^௪, can be demonstrated as ^^^௪ൌ^^ିௗ^ௗ௩^^ଶ൫^^,ೌೡ^ାூ^^൯^^ , ^^^,^௩^ ^ 0 (9)in which ^^^,^௩^current.

[0106] In some examples, instead of variable frequency critical soft switching, the control system 550 uses soft switching, variable frequency soft switching, or critical soft switching. For example, a static switching frequency may be used that results in soft switching, or in critical soft switching. In some these examples, the switching frequency fsw,abcnmay be provided from a memory (e.g., the memory 157) to the switch drivers 522b. As used herein, a control system that implements soft switching may refer to the control system implementing static frequency (non-critical) soft switching, static frequency critical soft switching, variable frequency (non-critical) soft switching, and / or variable frequency critical soft switching. Similarly, a control system that implements variable frequency soft switching may refer to the control system implementing variable frequency (non-critical) soft switching and / or variable frequency critical soft switching.

[0107] As illustrated in FIG. 6, the switch driver 522b of each local controller 660a, 660b, 660c, 660n may receive a corresponding one of the switching frequencies fsw,abcn from the VFCSS sub-blocks 522a, and may also receive a corresponding one of the duty cycles Dabcnfrom the regulator blocks 520b. Each switch driver 522b may generate a respective PWM -32- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 signal pair 530a, 530b, 530c, 530n of the PWM signals 530 (see FIG. 5), where each pair includes a noninverted PWM signal and an inverted PWM signal having the duty cycle and frequency specified by the inputs, as described above. For example, the PWM signal pair 530a has a duty cycle of Daand a switching frequency of fsw,a.

[0108] The PWM signals 530 (FIG. 5), including the PWM signal pairs 530a, 530b, 530c, and 530n (FIG.6), may be received by and drive the switching of the power switching elements of the phase legs 402a, 402b, 402c, and 402n (FIG.5). For example, with reference back to FIG.3, the PWM signal pair 530a may control switches S1 and S2, the PWM signal pair 530b may control switches S3 and S4, the PWM signal pair 530c may control the switches S5 and S6, and the PWM signal pair 530n may control the switches S7 and S8.

[0109] In some examples, rather than an additional local level of regulation for each phase leg provided by the regulators 520b, the second transformation block 520 translates the control reference target for each phase leg (e.g., Vg,abcn*) to a duty cycle by using, for example, a function to calculate respective duty cycles using the control reference targets or a lookup table to map the control reference targets to respective duty cycles. Thus, in some examples, the second transformation block 520 may perform the translation to generate duty cycles Dabcn without using sensed or actual value corresponding to the control reference target (e.g., Vg,a, Vg,b, Vg,c, Vg,n ) as feedback for local regulation. Accordingly, in some examples, in place of the regulators 520b, a translator block is present to perform this translation from control reference target to duty cycle.

[0110] By including a (fourth) half bridge on the neutral phase leg 402n, the system 500 can provide a balanced power system. That is, the system 500 can actively balance the three phases of the AC system 302 and the four-leg power converter 304. This balancing may be advantageous, for example, when using the four-leg power converter 304 to feed or power the AC system 302 in a grid forming mode, for example, when the AC system 302 is a three- phase AC utility grid or local AC grid (e.g., of a building or facility). Such three-phase AC grids can have significantly more power on one or two phases than the other phase(s), which, unless balanced, can lead to large (undesirable) circulating currents in the system. By controlling the current or voltage in the neutral phase leg 402n using the fourth half bridge, the system 500 can actively balance the AC system 302, and avoid, for example, hazardous voltages on the four-leg power converter 304. Using the delta-sigma control, the system 500 -33- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 can modulate the power factor to provide power factor correction (PFC) and can modulate the DC bus 314, both of which may further stabilize the common mode voltage and current in the system. Thus, the system 500 allows for common mode control and, as a result, allows to control voltage and zero current (e.g., leakage current, etc.). Furthermore, the system 500 can balance the three-phases of the AC system 302 without including an isolating transformer. Such an isolating transformer can be large or bulky, costly, and reduce efficiencies in power conversion. Still, in some examples, an isolating transformer could be provided to connect the four-leg power converter 304 to the AC system 302. Additionally, the system 500 can balance the system without using as large of a capacitor as may otherwise be required (e.g., to prevent unbalanced voltages on the DC bus 314).

[0111] As noted above, in some examples, the four-leg power converter 304 is coupled to a three-phase AC traction motor of an electric in place of the AC system 302. When the converter 304 is coupled to and driving a traction motor (e.g., operating in a traction mode), the system 500 may be more likely to be balanced. Accordingly, in such examples, the control system 505 may detect or determine that the converter 304 is coupled to the traction motor, and may selectively operate with three-phases, rather than use the neutral leg to balance the system 500. That is, the control system 305 may control the converter phase legs 402a, 402b, and 402c to convert power, and disable operation of the neutral phase leg 402n (e.g., by disconnecting the neutral phase leg 402n and disabling the δ-loop). Similarly, when the four-leg power converter 304 is coupled to a three-phase grid and operating in a grid following mode, the system 500 may again be more likely to be balanced. Accordingly, in such examples, the control system 505 may detect or determine that the converter 304 is operating in a grid following mode, and may selectively operate with three-phases, rather than use the neutral leg to balance the system 500. In other examples, the control system 505 may operate with the four legs 402a, 402b, 402c, and 402n regardless of whether the system 500 is operating in a traction mode or a grid following mode. When the converter 304 is operating in a balanced system, the control system 500 may employ symmetric control modes (e.g., using three phase legs and disabling the neutral phase leg), and when the converter 304 is operating in an unbalanced system, the control system 500 may employ asymmetric control modes (e.g., using the three phase legs and the neutral phase leg). -34- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 Simulation Results

[0112] The power converter system 500, including the four-leg power converter 304 and the control system 505, was validated through a simulated model in PLECS. The parameters used for the simulations were: VDC= 800 V, Lf= 8 µH, Lf,ESR= 15 mΩ, Cf= 12 µF, Cf,ESR = 3.5 mΩ, CDC = 24 µF, Lg = 15 µH, Lg,ESR = 7.5 mΩ, Fg = 50 Hz, Vg,LLRMS= 400 V, IRMS = 16 A. Results of the simulation are shown in FIGS.8A-8C and FIGS.9A-9B. In particular, FIGS.8A- 8C depict switch-side inductor currents (IL,A, IL,b, and IL,c), which show three different behaviors depending on the regulator on-state (PI On-Signal) and on the d‐current reference (Idref). The current trend matches with the expected theoretical current trend generated using the discrete VF-CSS technique since the switching frequency is higher around the zero- crossing of the signal, while it decreases approaching the crest of the waveform.

[0113] The output voltage and current at the point of common coupling (PCC) are illustrated in FIGS. 9A-9B. In particular, a top graph 900 of FIG. 9A illustrates the output voltage and a bottom graph 905 of FIG. 9B illustrates the output current. In the top graph 900, the three-phase output voltage is controlled to be centered at VDC / 2, matching with the neutral voltage (Vn). In the bottom graph 905, when the regulators are in their active state, and the current reference is given, the output current tends to behave as a balanced three- phase current with the neutral current fixed at zero, thereby confirming the robustness of the control scheme.

[0114] FIGS.10A-10B illustrate two example power converter systems 1000a, 1000b, respectively, that include a DC system 1005, a DC / DC converter 1010, an AC / DC converter 1015, and an AC system 1020. With reference also to FIG. 1, the AC system 1020 is an example of the second load / source 130, the DC / DC converter 1010 and AC / DC converter 1015 are, collectively, an example of the power converter 115 and LC filter 120, and the DC system 1005 is an example of the DC load / source 110. Additionally, in at least some examples, the DC system 1005 may be similar to the DC system 306 of FIG. 3 and the AC system 1020 may be similar to the AC system 302 of FIG. 3. The DC / DC converters 1010 include a positive DC rail 1030 and a negative DC rail 1032 that couple to the AC / DC converter 1015 and to the DC system 1005. -35- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272

[0115] In FIG. 10A, the DC / DC converter 1010 is also labeled as DC / DC converter 1010a, and in FIG.10B, the DC / DC converter 1010 is also labeled as DC / DC converter 1010b. The DC / DC converter 1010a of FIG. 10A includes two half bridge circuits 1012a-b, each similar to the half-bridge converter 200 of FIG. 2. The DC / DC converter 1010b of FIG. 10B includes one half bridge circuit, which is similar to the half-bridge converter 200 of FIG.2.

[0116] Each half-bridge 1012a and 1012b of the DC / DC converter 1010a includes a pair of power switching elements (M1 and M2 for half-bridge 1012a, and M3 and M4 for half- bridge 1012b) connected by a midpoint node and coupled across DC terminals (DC rails 1030 and 1032), and includes an LC filter coupled to the power switching elements by the midpoint node, to the filter node, and to the DC rails 1030 and 1032. In FIG.10A, the DC / DC converter 1010a includes filter nodes 1034 and 1036 respectively coupling the DC / DC converter 1010a (and particularly, the LC filter thereof) to positive and negative terminals of the DC system 1005 (e.g., to the DC voltage source or battery 1040 (VDC) of the DC system 1005). The filter nodes 1034 and 1036 may also be referred to a positive battery terminal node and a negative battery terminal node, respectively, that make up a battery connection section fo the DC / DC converter 1010a.

[0117] In FIG.10B, the DC / DC converter 1010b includes a filter node 1038 coupling the DC / DC converter 1010b (and particularly, the LC filter thereof) to a positive terminal of the DC system 1005 (e.g., to the positive terminal of the DC voltage source VDC of the DC system 1005). The DC / DC converter 1010b further includes a connection between the negative DC rail 1032 and a negative terminal of the DC system 1005 (e.g., to the negative terminal of the DC voltage source VDCof the DC system 1005). The filter node may also be referred to a positive battery terminal node and the DC rail 1032 may also be referred to as a negative battery terminal node, where the positive and negative battery terminal nodes make up a battery connection section of the DC / DC converter 1010b.

[0118] The DC / DC converter 1010 is configured to boost (increase) and / or buck (decrease) DC voltage between components. For example, in FIGS.10A and 10B, the DC / DC converter 1010 is configured to boost and / or buck DC voltage between the DC system 1005 and the AC / DC converter 1015. For example, when the DC / AC converter is operating as a rectifier and rectifying AC power received from the AC system 1020 to DC power, the DC / DC converter 1010 may be configured to increase or decrease the DC voltage of the received DC -36- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 power and provide the increased or decreased DC voltage to the DC system 1005 (e.g., to charge a battery represented by the VDCin FIGS 10A-10B). Additionally, when the DC / AC converter is operating as an inverter and inverting DC power received from the DC system 1005 to AC power, the DC / DC converter 1010 may be configured to increase or decrease the DC voltage of the received DC power and provide the increased or decreased DC voltage to the AC / DC converter 1015 (e.g., to drive an AC motor or output power onto an AC grid).

[0119] In some examples, in place of the AC / DC converter 1015 and the AC system 1020, the DC / DC converter 1010 of FIG. 10A and / or FIG. 10B is coupled to a DC system similar to the DC load / source 110 of FIG. 1 (e.g., a battery, an electrical subsystem of a vehicle, a DC grid, etc.). In other words, with reference also to FIG.1, the DC / DC converter 1010 may serve as the power converter 115 and the LC filter 120, and the second source / load 130 may also be a DC source / load, similar to the DC load / source 110.

[0120] A controller (e.g., of the control system 105 of FIG. 1) may control the switching elements of the DC / DC converter 1010 to perform the boost and / or buck conversion of the DC / DC converter 1010. An example control scheme for controlling the DC / DC converter 1010 and, in particular, the DC / DC converter 1010a, is provided in further detail below.

[0121] Turning to FIG. 11, an example power converter system 1100 is illustrated. The power converter system 1100 may be similar to examples of the power converter system 1000a of FIG.10A in which the AC / DC converter 1015 is similar to the four-leg power converter 304 and the AC system 1020 is similar to AC system 302. However, in FIG.11, a contactor assembly 1105 is provided to connect the DC / DC converter 1010a and the DC system 1005. The contactor assembly 1105 may be part of the DC system 1005, the DC / DC converter 1010, or a separate component linking the DC system 1005 and the DC / DC converter 1010. Additionally, in some examples, the power converter system 1100 includes the DC / DC converter 1010b of FIG.10B in place of the DC / DC converter 1010a of FIG.10A, and / or the AC system 1020 is a single-phase AC grid, a three-phase motor, or a single-phase motor.

[0122] The contactor assembly 1105 includes filter contactors F1, F2 and DC rail contactors D1,D2. The filter contactors and the DC rail contactors are switches (e.g., relays, FETs, or the like) controllable by a control system (e.g., the control system 105 of FIG.1). The -37- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 contactor assembly 1105 has two operational states: a bypass state in which filter contactors F1, F2are open and the DC rail contactors D1,D2are closed and a DC conversion state in which filter contactors F1, F2are closed and the DC rail contactors D1,D2are open. In the bypass state, the DC rails 1030 and 1032 are connected to the DC system 1005 (e.g., to the battery represented by Vbatt), thereby providing a bypass path that bypasses the DC / DC converter 1010 (e.g., the power switching elements and LC filter thereof). In the DC conversion state, the bypass path is severed and the DC / DC converter 1010 may operate to perform DC / DC conversion. For example, DC power received via the DC rails 1030, 1032 from the AC / DC converter 304, 1015 may be boosted or reduced and provided to the DC system 1005 via the closed filter contactors F1, F2.

[0123] Although the DC / DC converter 1010 is able to provide an efficient DC / DC conversion, converting power by the DC / DC converter 1010 nevertheless involves some losses and, thus, some reduction in efficiency for the power converter system 1100 when converting. By selectively controlling the contactor assembly 1105, the DC / DC converter 1010 can be selectively bypassed when, for example, DC / DC power conversion is not desired or required. For example, the DC system 1005 may have a defined operating range (e.g., defined by a low and high voltage threshold). When DC power output by the AC / DC converter 304, 1015 is at a voltage level within the operating range of the DC system 1005, the contactor assembly 1105 may be controlled to the bypass state so that the DC / DC converter 1010 is bypassed, and the efficiency of the power converter system 1100 may increase. However, when the DC power output by the AC / DC converter 304, 1015 is above or below the operating range of the DC system 1005, the contactor assembly 1105 may be controlled to the DC conversion state so that the DC / DC converter 1010 may convert (boost or buck) the DC voltage to be within the operating range of the DC system 1005.

[0124] In some examples, the power converter system 1100 is implemented with an electric vehicle, where the DC battery 1040 is an electric vehicle battery (e.g., for powering a traction motor of the electric vehicle). In such a system, a control system (e.g., the control system 105) may determine a voltage level of the DC battery 1040, control the contactor assembly 1105 to connect the DC battery 1040 to the DC rails 1030, 1032 to charge the DC battery 1040 when the voltage level is above a threshold. Further, the control system 105 may, when the voltage level is below the threshold, control the contactor assembly 1105 to -38- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 connect the DC battery 1040 to the DC / DC converter 1010, and drive the DC / DC converter 1010 to step-down DC voltage on the DC rails 1030, 1032 from a first level to a second level to charge the DC battery 1040 with DC voltage at the second level.

[0125] By including the DC / DC converter 1010 in the power converter system 1100, the DC system 1005 may be designed to have a smaller operating range, an operating range with a lower upper threshold, and / or an operating range with a higher lower threshold than may otherwise be possible for the power converter system 1100, which may enable a reduced size or cost of the DC system 1005, or a DC system 1005 with higher overall efficiency. Further, by selectively bypassing the DC / DC converter 1010 when DC power on the DC rails 1030 and 1032 is within the operating range of the DC system 1005, the reduced efficiencies caused by the DC / DC converter 1010 can be avoided in these circumstances.

[0126] In some examples, in place of the AC / DC converter 1015 and the AC system 1020, the power converter system 1100 of FIG.11 includes the DC / DC converter 1010,1010a coupled to a DC system similar to the DC load / source 110 of FIG. 1 (e.g., a battery, an electrical subsystem of a vehicle, a DC grid, etc.).

[0127] FIG. 12 illustrates a DC / DC power converter system 1200 that controls the DC / DC converter 1010a using differential mode (DM) and common mode (CM) variable decomposition. The DC / DC power converter system 1200 includes the DC / DC converter 1010a and a control system 1205. With reference also to FIG.1, the DC / DC power converter system 1200 is an example of the power converter system 100, the control system 1205 is an example of the control system 105, and the DC / DC converter 1010a is an example of the power converter 115 and LC filter 120 (or a portion thereof).

[0128] Generally, the control system 1205 senses electrical operational characteristics for the DC / DC converter 1010a, uses differential mode (DM) and common mode (CM) variable decomposition to generate Delta / Sigma (Δ / Σ) components through a linear transformation, generates control reference targets based on the Delta / Sigma (Δ / Σ) components, and controls the DC / DC converter 1010a based on the control reference targets.

[0129] The control system 1205 includes a first ΔΣ transformation block 1210 to translate received electrical characteristics from a measured format to Delta / Sigma (Δ / Σ) components, a battery voltage controller 1215, a battery current controller 1220, a battery -39- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 Sigma voltage control block 1225, a second ΔΣ transformation block 1230, and a variable frequency critical soft switching (VFCSS) block 1235.

[0130] The first ΔΣ transformation block 1210 may include sub-blocks 1210a, 1210b, 1210c. The sub-block 1210a may translate voltage at positive and negative legs of the DC system 1005 (V+, V-) to Delta / Sigma voltage components VΔ and VΣ. The sub-block 1210b may translate current at positive and negative legs of the DC system 1005 (I+ and I-) to Delta / Sigma current components IΔ and IΣ. The sub-block 1210c may translate inductor current for each of the positive and negative legs of the DC system 1005 (IL+ and IL-) to Delta / Sigma components ILΔ and ILΣ. To perform the translation, the sub-blocks 1210a may perform a linear transformation as follows: ^^^ 1 െ^^ ^^ ^^൨ ൌ ^ 1 ା ା^^^ ^ ൨ ൌ ^^^^^^ ^ ൨ (10)ஊଶ1 1 ^^ ^^

[0131] A the sub-blocks 1210band 1210c, replacing the voltage characteristics with the respective current characteristics for those sub-blocks.

[0132] Generally, the Delta components may regulate battery charging and discharging operations (e.g., using constant current (CC) and constant voltage (CV) algorithms), while the Sigma components may maintain the common mode (e.g., common mode voltage) stable.

[0133] FIG. 13 illustrates a subset 1300 of the control system 1205 including the second ΔΣ transformation block 1230 and the VFCSS block 1235. More particularly, in FIG. 13, the second ΔΣ transformation block 1230 is illustrated as including a Delta-Sigma translator 1230a and two regulators 1230b for each leg of the DC / DC converter 1010a.

[0134] Further, the VFCSS block 1235 is illustrated as having a VFCSS sub-block 1235a and a switch driver 1235b, one for each leg of the DC / DC converter 1010a. The regulator 1230b, VFCSS sub-block 1235a, and switch driver 1235b for each phase may be implemented on a respective one of local controllers 1360a and 1360b. The local controllers 13360a-b may be an example of the local controllers 160 of FIG. 1. The Delta-Sigma translator 1230a and remaining components of the control system 1205 illustrated in FIG. 12 (aside from the VFCSS block 1235) may be implemented on a central controller, such as, for example, the central controller 150 of FIG.1. Each of the local controllers 1360, 160 and -40- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 central controller 150 may be implemented by separate hardware (e.g., a separate microprocessor, FPGA, etc.) or one or more of these controllers may be virtual controllers that share hardware (e.g., implemented on the same microprocessor, FPGA, etc.). In some examples, the switch drivers 1235b are implemented as hardware components that are separate from the local controllers 1360a-b.

[0135] An example operation of the DC / DC power converter system 1200 is described in further detail with respect to the process 1400 of FIG.14. In FIG.14, a process 1400 for converting voltage with a DC / DC converter that uses differential mode (DM) and common mode (CM) variable decomposition is illustrated. The process 1400 is described as being carried out by the power converter system 100 implemented as the DC / DC power converter system 1200 of FIG. 12. However, in some embodiments, the process 1400 is implemented by another power converter system or by the power converter system 100 implementing another power converter system (e.g., the DC / DC converter 1010a of FIGS. 10A and 11, the reconfigurable system 1700 of FIGS.17A-B, the reconfigurable system 1800 of FIGS.18A-B, and the reconfigurable system 1900 of FIGS.19A-B,). Additionally, although the blocks of the process 1400 are illustrated in a particular order, in some embodiments, one or more of the blocks may be executed partially or entirely in parallel, may be executed in a different order than illustrated in FIG.14, or may be bypassed.

[0136] In block 1405, a control system determines a first electrical characteristic at a positive battery terminal node of a battery connection section of a DC / DC converter, where the DC / DC converter further includes a DC voltage section including a DC bus, a first half bridge including first power switching elements and a first LC filter, wherein the first LC filter is connected to the positive battery terminal node, and a second half bridge including second power switching elements and a second LC filter, wherein the second LC filter is connected to the negative battery terminal node. For example, with reference to FIG. 12, the control system 1205 determines a first electrical operational characteristic at the filter node 1034 of the half bridge 1012a of the DC / DC converter 1010a. With continued reference to FIG.12, the electrical operational characteristic may include, for example, voltage at the filter node 1034 for a positive leg of the DC system 1005 (V+) and / or current at the filter node 1034 for the positive leg of the DC system 1005 (I+). The control system 1205 may obtain these -41- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 electrical operational characteristics via one or more sensors (e.g., the sensors 140 of FIG. 1).

[0137] In block 1410, the control system determines a second electrical characteristic at a negative battery terminal node of the battery connection section of the DC / DC converter. For example, with reference to FIG. 12, the control system 1205 determines a second electrical operational characteristic at the filter node 1036 of the half bridge 1012b of the DC / DC converter 1010a. With continued reference to FIG. 12, the electrical operational characteristic may include, for example, voltage at the filter node 1036 for a negative leg of the DC system 1005 (V-) and / or current at the filter node 1036 for the positive leg of the DC system 1005 (I-). The control system 1205 may obtain these electrical operational characteristics via one or more sensors (e.g., the sensors 140 of FIG.1).

[0138] In blocks 1405 and / or 1410, the control system 1205 may further receive an inductor current (IL+ and IL-) through an inductor of the LC filter of each half bridge 1012a- b, among other electrical characteristics for the DC / DC converter 1010a (e.g., via the sensors 140 of FIG.1).

[0139] In block 1415, the control system generates a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic. For example, with reference to FIG. 12, the control system 1205 translates the first and second electrical operational characteristics obtained in blocks 1405 and 1410 (e.g., V-, V+ and / or I-, I+) using the first ΔΣ transformation block 1210 to generate Delta and Sigma components for the first and second electrical characteristics. For example, as described above, the sub-block 1210a may translate voltage at positive and negative legs of the DC system 1005 (V+, V-) to Delta / Sigma voltage components VΔ and VΣ. Additionally or alternatively, the sub-block 1210b may translate current at positive and negative legs of the DC system 1005 (I+ and I-) to Delta / Sigma current components IΔ and IΣ. Additionally, in some examples, the sub-block 1210c may translate inductor current for each of the positive and negative legs of the DC system 1005 (IL+ and IL-) to Delta / Sigma components ILΔ and ILΣ. To perform the translation, the sub-blocks 1210a may perform a linear transformation as described above. In some examples of block 1415, and as illustrated in FIG.12, , the first ΔΣ transformation block 1210 -42- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 translates each of the V- and V+, the I- and I+, and the IL+ and IL- pairs of characteristics to corresponding Delta and Sigma components.

[0140] The control system 1205 may then use the Delta and Sigma components to generate the first DC / DC control reference target and second DC / DC control reference target. For example, an error block 1240 may receive the Delta voltage component VΔ and a reference Delta voltage component VΔ* and provide a difference between the values (e.g., an error signal) to the battery voltage controller 1215. The reference Delta voltage component VΔ* may be a desired voltage across the positive and negative battery terminals of the battery 1040. The reference Delta voltage component VΔ* may be obtained from a memory (e.g., the memory 157) or input via an I / O interface (e.g., the I / O interface 142). The battery voltage controller 1215 may generate a reference Delta current component (IΔ*) and provide the component to an error block 1242. For example, the battery voltage controller 1215 may be a regulator (e.g., implementing PID control, PI control, or the like) that generates the reference Delta current component (IΔ*) to ultimately cause the control system 1205 to drive the DC / DC converter 1010a such that the Delta voltage component VΔ tracks the reference Delta voltage component VΔ* .

[0141] The error block 1242 receives the reference Delta current component (IΔ*) and the Delta current component (IΔ) from the first ΔΣ transformation block 1210. The error block 1242 provides a difference between the values (e.g., an error signal) to the battery current controller 1220. The battery current controller 1220 may generate a target voltage delta VΔ** and provide the target voltage delta VΔ** to the second ΔΣ transformation block 1230. For example, the battery current controller 1220 may be a regulator (e.g., implementing PID control, PI control, or the like) that generates the target voltage Delta VΔ** to ultimately cause the control system 1205 to drive the DC / DC converter 1010a such that the Delta current component IΔ tracks the reference Delta current component IΔ*.

[0142] Additionally, an error block 1244 may receive the Sigma voltage component VΣ and a reference Sigma voltage component VΣ* and provide a difference between the values (e.g., an error signal) to the battery Σ voltage controller 1225. The reference Sigma voltage component VΣ* may be a desired voltage sum of voltages at the positive and negative battery terminals of the battery 1040. The reference Sigma voltage component VΣ* may be obtained from a memory (e.g., the memory 157) or input via an I / O interface (e.g., the I / O interface -43- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 142). The battery Σ voltage controller 1225 may generate a target voltage Sigma (VΣ**) and provide the component to the second ΔΣ transformation block 1230. For example, the battery Σ voltage controller 1225 may be a regulator (e.g., implementing PID control, PI control, or the like) that generates the target voltage Sigma (VΣ**) to ultimately cause the control system 1205 to drive the DC / DC converter 1010a such that the Sigma voltage component VΣ tracks the reference Sigma voltage component VΣ*.

[0143] The second ΔΣ transformation block 1230 may ultimately translate the target voltages Delta and Sigma (VΔ** and VΣ**) into duty cycle values D+ and D‐ for a pulse-width modulated (PWM) signal (fsw+-) to drive the power switching elements of each half bridge 1012a-b of the DC / DC converter 1010a. FIG. 13 illustrates a functional diagram of one example of the second ΔΣ transformation block 1230. As part of the translation by the second ΔΣ transformation block 1230 (and as part of block 1415 of the process 1400), the target voltages Delta and Sigma VΔ** and VΣ** (Delta Sigma control targets) may be translated to voltage reference values V+* and V-* (a first DC / DC control reference target and a second DC / DC control reference target).

[0144] With reference to FIG. 13, the target voltages Delta and Sigma VΔ** and VΣ** are provided to the Delta-Sigma translator 1230a. The Delta-Sigma translator 1230a may translate the target voltages Delta and Sigma VΔ** and VΣ** to voltage reference values V+* and V-*. More particularly, the Delta-Sigma translator 1230a may represent an inverse of the linear transformation described above with respect to the translation performed by the sub- block 1210a, which the control system 1205 may execute via the Delta-Sigma translator 1230a to transform the target voltages Delta and Sigma VΔ** and VΣ** to voltage reference values V+* and V-*.

[0145] Accordingly, in block 1415, the Delta-Sigma translator 1230a of the control system 1205 may generate the first DC / DC control reference target and the second DC / DC control reference target, based on the difference (Δ) between the first electrical characteristic and the second electrical characteristic and on the sum (Σ) of the first electrical characteristic and the second electrical characteristic.

[0146] In block 1420, the control system may drive the first power switching elements in accordance with the first DC / DC control reference target. For example, and as explained further below, the control system 1205 may drive the power switching elements -44- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 M1 and M2 of the half bridge 1012a by outputting PWM signals 1250 generated based on the voltage reference value V+* (see FIG.13).

[0147] In block 1425, drive the second power switching elements in accordance with the second DC / DC control reference target. For example, the control system 1205 may drive the power switching elements M3 and M4 of the half bridge 1012b by outputting PWM signals 1250 generated based on the voltage reference value V-* (see FIG.13).

[0148] The control system 1205 may execute blocks 1420 and 1425 in parallel to drive the first and second half bridge circuits 1210a-b. For each half bridge circuit 1210a-b, the PWM signals of the PWM signals 1250 may include a non-inverted PWM signal for a first power switching element (e.g., M1) and an inverted PWM signal for a second power switching element (e.g., M2), where the inverted PWM signal is inverted with respect to the non- inverted PWM signal (e.g., the inverted PWM signal is 180 degrees out of phase with respect to the non-inverted PWM signal), but has the same duty cycle and frequency. For example, for the half bridge 1012a, the non-inverted and inverted PWM signal pair of the PWM signals 1250 may have a duty cycle of D+ and a frequency of fsw+; and, for the half bridge 1012b, the non-inverted and inverted PWM signal pair of the PWM signals 1250 may have a duty cycle of D‐ and a frequency of fsw-.

[0149] As shown in FIG.12, the duty cycle (D+-) may be generated by the second ΔΣ transformation block 1230, and the switching frequency (fsw+-) may be generated by the VFCSS block 1235. Turning to FIG. 13, additional details with respect to an example of generating the duty cycle (D+-) and the switching frequency (fsw+-) are illustrated.

[0150] In FIG.13, one of the voltage reference value V+-* output by the Delta-Sigma translator 1230a are provided to each of local controllers 1360a and 1360b, respectively. More particularly, the control reference target V+* is provided to the (Reg+) regulator 1230b of the local controller 1360a, and the control reference target V-* is provided to the (Reg-) regulator 1230b of the local controller 1360b. Each regulator 1230b further receives a corresponding sensed or actual voltage value V+, V- and generates a corresponding duty cycle D+, D‐ based on the received control reference target and the sensed or actual voltage value V+, V-. For example, each of the regulators 1230b may implement model predictive control (MPC) or another regulation control scheme (e.g., PID control, PI control, or the like) that provides an output duty cycle (D+-) based on a difference between an input reference -45- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 target (e.g., V+-*) and an input actual value (e.g., V+-). Each regulator may generate an output (e.g., duty cycle D+, D‐) to ultimately adjust the actual value (e.g., V+-) towards the input reference target (e.g., V+-*). For example, in some examples, the Reg+regulator 1230b determines or receives a difference between V+* (an input reference target) and V+ (an actual value), and generates D+ (an output duty cycle) to steer the actual value (V+) to track (V+*).

[0151] Further, in FIG.13, each local controller 1360a-1360b has a corresponding one of the VFCSS sub-blocks 1235a. Each of the VFCSS sub blocks 1235a may receive the duty cycle D+ or D‐ generated by the corresponding regulator 1230b, along with an inductor current (IL+, IL-) for each half bridge and a voltage (V+, V-) for each battery terminal node. Each of the VFCSS sub-blocks 1235a may output a respective frequency value as the switching frequency for a corresponding phase leg (e.g., fsw+, fsw- for half bridge 1012a and 1012b).

[0152] The switching frequency is determined by the VFCSS sub-blocks 1235a to enable the power switching elements of the half bridges 1012a-b to achieve soft-switching. By varying the switching frequency to achieve using soft-switching, as opposed to hard switching, high turn-on losses of the upper switch are substituted with low turn-off losses of the lower switch of each half bridge 1012a-b. More particularly, in some examples, to realize soft switching, the VFCSS sub-blocks 1235a reshape the phase leg inductor current ripple such that the vertex and nadir points are positive and negative. The vertex and nadir point ripple value should be large enough to guarantee a full soft switching. With reference to the half-bridge converter 200 of FIG.2 (which is an example implementation of each of the half bridges 1012a and 1012b), in the period when ^^^is turned on, the phase leg inductor current is discharging ^^^switch capacitor, ^^^ௌ265a. The ^^^zero voltage switching can be realized under theof ^^^ௌ265a beingdischarged before ^^^is on. In the same way, a reversed direction from the phase leg inductor currentto completely discharge ^^ଶswitch capacitor, ^^^ௌ265b, before ^^ଶis on. The particular switching frequency fsw+, fsw- can be determined using the equations (9) and (10) described above.

[0153] In some examples, instead of variable frequency critical soft switching, the control system 1205 uses soft switching, variable frequency soft switching, or uses critical -46- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 soft switching. For example, a static switching frequency may be used that results in soft switching, or in critical soft switching. In some of these examples, the switching frequency fsw,abcnmay be provided from a memory (e.g., the memory 157) to the switch drivers 1235b.

[0154] As illustrated in FIG. 13, the switch driver 1235b of each local controller 1360a, 1360b may receive a corresponding one of the switching frequencies fsw+- from the VFCSS sub-blocks 1235a, and may also receive a corresponding one of the duty cycles D+- from the regulators 1230b. Each switch driver 1235b may generate a respective PWM signal pair 1250a, 1250b of the PWM signals 1250 (see FIG. 12), where each pair includes a noninverted PWM signal and an inverted PWM signal having the duty cycle and frequency specified by the inputs, as described above. For example, the PWM signal pair 1250a has a duty cycle of D+ and a switching frequency of fsw+.

[0155] The PWM signals 1250 (FIG.12), including the PWM signal pairs 1250a, 1250b (FIG.13), may be received by and drive the switching of the power switching elements of the half bridges 1012a-b (FIG. 12). For example, the PWM signal pair 1250a may control switches M1 and M2, the PWM signal pair 1250b may control switches M3 and M4.

[0156] In some examples, rather than an additional local level of regulation for each phase leg provided by the regulators 1230b, the second ΔΣ transformation block 1230 translates the control reference target for each phase leg (e.g., V+*, V-*) to a duty cycle by using, for example, a function to calculate respective duty cycles using the control reference targets or a lookup table to map the control reference targets to respective duty cycles. Thus, in some examples, the second ΔΣ transformation block 1230 may perform the translation to generate duty cycles D+, D‐ without using sensed or actual value corresponding to the control reference target (e.g., V+, V-) as feedback for local regulation. Accordingly, in some examples, in place of the regulators 1230b, a translator block is present to perform this translation from control reference target to duty cycle.

[0157] The process 1400 for converting voltage using (DM) and (CM) variable decomposition is operable with the DC / DC converter 1010a in a system that incorporates the four-leg power converter 304, as illustrated in FIG. 11. In some examples, the process 1400 is operable with the DC / DC converter 1010a in a system that includes other types of AC / DC converters (e.g., including single phase AC / DC converters, three phase AC / DC converters that do not include a half bridge for a neutral leg, etc.) and other DC -47- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 loads / sources. In some examples, the process 1400 is operable with the DC / DC converter 1010a when coupled to a DC system similar to the DC load / source 110 of FIG. 1 (e.g., a battery, an electrical subsystem of a vehicle, a DC grid, etc.), rather than an AC / DC converter and AC grid.

[0158] Additionally, the DC / DC converter 1010a may implement the process 1400 and be incorporated in a system that selectively enables or bypasses the DC / DC converter 1010a (e.g., using contactor assembly 1105) as described with respect to FIG.11, or may be in a system that does not provide such selective bypassing.

[0159] In some examples, the power converters disclosed herein are transformerless. For example, as illustrated in FIGS.5, 10, 11, the converters 304, 1010, and / or 1015 may not include an isolating transformer. Some systems may include an isolating transformer in a DC / DC converter, which may serve to provide isolation for a coupled AC / DC converter (e.g., 304, 1015). However, if the DC / DC converter is bypassed (e.g., as discussed with respect to FIG.11), the isolation provided by the DC / DC converter is no longer present for use by the AC / DC converter. In such examples, a system may include a separate isolating transformer, a large common mode choke, and / or large capacitances Cy in the AC / DC converter to mitigate or reduce common mode voltages and currents in the system. However, by using the delta-sigma based control of the four-leg power converter 304 described with respect to FIGS. 5-7, the common mode voltage and current associated with the neutral leg can be explicitly and actively controlled. With such active control, a DC / DC converter (with or without an isolating transformer) may be selectively bypassed (to provide the discussed efficiency improvements), the size of a common mode choke can be reduced by an order of magnitude relative to systems that do not include active control, and an isolating transformer may not be included for the four-leg power converter 304. For example, the size of the common mode choke can be reduced by a factor two to one hundred times, by five to one hundred times, by ten to twenty times, by two to ten times, by five to ten times, or another range within five to one hundred times. In some examples, the common mode choke may be 4 millihenries (mH), less than 20 mH, less than 10 mH, less than 5 mH, between 4 and 10 mH, or between 4 and 20 mH. In contrast, a common mode choke in other three phase systems may be in the hundreds of millihenries or many tens of millihenries. -48- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 Simulation Results

[0160] The power converter system 1100 (FIG. 11), including the four-leg power converter 304 implementing the control scheme described with respect to FIGS.5-7, and the DC / DC converter 1010a implementing the control scheme described with respect to FIGS. 12-14, has been validated through a simulated model in PLECS / Simulink. The main parameters used for the simulations are: ^^^^= 800 V, ^^^= 8 H, ^^^,ாௌோ= 15 mΩ, ^^^= 12 F, ^^^,ாௌோ= 3.5 mΩ, ^^^^= 144 F, ^^^= 15 H, ^^^,ாௌோ= 7.5 mΩ, ^^^= 50 Hz, ^^^ோ,^ெ^ௌ= 400 V, ^^^^௧௧= 400 V, ^^^∗= 16 A. Results of the simulation are shown in FIGS.15A-15C and FIGS.16A-16C. More particularly, FIGS.15A-15C depict currents and voltages measured at the AC / DC stage (the four-leg power converter 304). In particular, chart 1505 of FIG.15A shows the switch- side inductor currents, which exhibit three different behaviors depending on the regulator state and on the reference applied to the battery current controller. The current trend matches with the expected theoretical one generated using the discrete VF-CSS technique since the switching frequency is higher around the zero-crossing of the signal, while it decreases approaching the crest of the waveform. Chart 1510 of FIG. 15B highlights the three-phase output voltage measured at the point of common coupling (PCC), which is controlled to be centered at^ವ^ଶ , matching with the neutral voltage (^^^,^). Chart 1515 of FIG. 15C shows the three-current at the PCC, which, as soon as the regulators are in their active state, and a current step is applied to the DC / DC stage (DC / DC converter 1010a), tends to behave as a balance three-phase current, with the neutral current fixed at zero.

[0161] Moving to the battery interface, FIGS. 16A-16C shows simulation results obtained at the DC / DC converter 1010a. Specifically, chart 1605 of FIG.16A highlights the switch side inductor currents, whose trends corresponds to the theoretical one for DC currents in soft-switching operation when the regulator is active and a current step is applied. Chart 1610 of FIG. 16B depicts the output voltages measured at the battery terminals which are stabilized by the Σ - voltage controller. Chart 1615 of FIG.16C represents the current measured at the battery terminals which, as soon as a reference current step is applied, it adjusts to the value of ^^^∗as expected.-49- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272

[0162] FIGS. 17A-19B illustrate three example reconfigurable power converter systems 1700, 1800, and 1900 (also referred to as reconfigurable systems). As explained further below, each reconfigurable system 1700, 1800, and 1900 includes an AC / DC converter and a DC / DC converter sharing DC rails, where the AC / DC converter can operate in a three-phase mode when connected to a three-phase AC system 1705 and in a single- phase mode when connected to a single-phase AC system 1710. Additionally, when operating in a three-phase mode, the AC / DC converters of the reconfigurable systems 1700 and 1800 can operate in a symmetric three-phase operational mode or asymmetric three-phase operational mode. Additionally, the AC / DC converters of the reconfigurable systems 1700 and 1800 can operate in a symmetric split-phase operational mode or asymmetric split- phase operational mode when connected to a split-phase AC system 1712. The reconfigurable systems 1700, 1800, and 1900 are further coupled to a DC system 1715. With reference also to FIG. 1, each of the reconfigurable systems 1700, 1800, and 1900 is an example of a combination of the power converter 115 and LC filter 120; each of the three- phase AC system 1705, the single-phase AC system 1710, and the split-phase AC system 1712 is an example of the second source / load 130; and the DC system 1715 is an example of the DC load / source 110. Although not illustrated in FIGS.17A-19B, the control system 105 may control operation of the reconfigurable system 1700, 1800, 1900, as discussed with respect to FIG.1. Thus, for example, the control system 105 may be adaptable and reconfigurable to operate in the multiple operational modes described (e.g., single-phase, symmetric three- phase, asymmetric three-phase, symmetric split-phase, and asymmetric split-phase operational modes). The three-phase AC system 1705 may include an AC load or source including a first AC phase leg 1705a (VAC-a), a second AC phase leg 1705b (VAC-b), and a third AC phase leg 1705c (VAC-c). The single-phase AC system 1710 may include a single-phase AC load or source (AC load / source 1710a) including a first leg or node (VAC+) and a second leg or node (VAC-). The split-phase AC system 1712 may include split-phase AC loads or sources with a first phase 1712a and a second phase 1712b, including a first leg or node 1714a (VAC+) and a second leg or node 1714b (VAC-). The DC system 1715 may include a DC battery 1715a with a positive DC terminal (VDC+) and a negative DC terminal (VDC-). Also represented in the DC system 1715 is a chassis ground (as a ground node between capacitances Cy) in FIG.17A- -50- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 B. The chassis ground is, for example, the chassis ground for an electric vehicle in which the reconfigurable system 1700 may be incorporated as an on-board charger.

[0163] Additionally, in at least some examples, the DC system 1715 may be similar to the DC system 306 of FIG. 3 and / or the DC system 1005 of FIGS. 10-12. In at least some examples, the AC system 1705 may be similar to the AC system 302 of FIG.3 and / or the AC system 1020 of FIG.10. In at least some examples, the AC system 1710 may be similar to the AC system 1020 of FIG.10,

[0164] By designing the reconfigurable systems 1700, 1800, and 1900 to be reconfigurable between three-phase (symmetric and asymmetric), single-phase, and split- phase (symmetric and asymmetric), the systems may be suitable for operation with various types of utility grids in various geographic locations. For example, each of the reconfigurable systems 1700, 1800, and 1900 may be incorporated into an electric vehicle, for example, to serve as an on-board charger. The reconfigurable nature of the systems enables the incorporation of any one of the reconfigurable systems 1700, 1800, and / or 1900 into an electric vehicle regardless of the intended location in which the vehicle may be located (e.g., the United States, Japan, Germany, China, etc.). The reconfigurable systems 1700, 1800, and / or 1900 are each adaptable for use with single-phase utility grids and three-phase utility grids of various types.

[0165] Turning to FIGS. 17A, 17B, 17C, and 17D, the reconfigurable system 1700 includes a four-leg AC / DC converter 1725 and a DC / DC converter 1730. The four-leg AC / DC converter 1725 may be similar to the four-leg power converter 304 (e.g., of FIGS. 3), including having four half bridge circuits as described above (labeled 1725a-d). Each half bridge circuit further includes AC connection nodes 1706a-d (labeled only in FIG.17A, but present in other figures), which are similar to the AC connection nodes 225 of FIG. 2 and 330a-330d of FIG. 3. Additional labels of the components of the four-leg power converter 304 (e.g., of FIG.3) similarly apply to components of the four-leg AC / DC converter 1725, but are not illustrated to simplify the diagram (e.g., in FIG.17A). The reconfigurable system 1700 is illustrated in a three-phase configuration 1740 in FIG.17A, in a single-phase configuration 1750 in FIG. 17B, in a symmetric split-phase configuration 1760 in FIG. 17C, and in an asymmetric split-phase configuration 1780 in FIG.17D. The DC / DC converter 1730 is similar -51- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 to the DC / DC converter 1010a (e.g., of FIG.10A), including having two half bridge circuits as described above.

[0166] In the three-phase configuration 1740 of FIG.17A, the AC / DC converter 1725 may be driven in a three-phase operational mode by a control system (e.g., the control system 105 implementing the control system 505) using delta-sigma-based control, such as described with respect to FIGS.5 and 6 and the process 700 of FIG.7. For example, this delta- sigma-based control, an asymmetrical control mode, may be used when the AC system 1705 is unbalanced. In other examples, when the AC system 1705 is balanced, the control system may control the AC / DC converter 1725 using a symmetric control mode. In the symmetric control mode, the control system 105 may control the AC / DC converter 1725 by driving three of the half bridge circuits and corresponding phase legs 1705a-c, and disabling the neutral phase leg VAC-nand corresponding half bridge circuit. For example, the control system 105 may use rotational reference frame (e.g., the dq reference frame) control cascaded with per phase leg regulating control in the stationary reference frame (e.g., the abc reference frame). For example, the control system 105 may translate sensed grid current from the stationary reference frame to the rotational reference frame (e.g., ig,abc to ig,dq using the Park and Clarke transforms), provide the sensed grid current and a target grid current (e.g., ig,dq to ig,dq*) to a regulator block of the control system 105 (e.g., a proportional integral (PI) regulator or proportional integral derivative (PID) regulator) to generate a control reference voltage for a voltage across an output capacitor (e.g., vc,dq*) to urge the sensed grid current towards the target grid current, and then translate the control reference voltage to the stationary reference frame (e.g., vg,dqto vg,abcusing the inverse Park and Clarke transforms). The control system 105 may then provide the control reference voltage for each phase leg (e.g., vg,a, vg,b, vg,c) to a local regulator of the control system 105 for each of the three phase legs (e.g., a PI or PID controller for each phase leg), which can also receive a sensed voltage across the capacitor for each of the three phase legs (e.g., vc,a^or^vc,b), and generate a duty cycle reference value for switching elements of each of the three phase leg of the AC / DC converter 1725 to urge the voltage across the capacitor for each phase leg towards the corresponding control reference voltage.

[0167] Also in the three-phase configuration 1740 of FIG.17A, the DC / DC converter 1730 may be driven using Delta-Sigma-based control by the control system (e.g., the control -52- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 system 105 implementing the control system 1205), such as described with respect to FIGS. 12 and 13 and the process 1400 of FIG. 14, or may be driven according to other DC / DC control schemes. Accordingly, the control system 105 may include or implement both the control system 505 of FIG.5 and the control system 1205 of FIG.12, in some examples.

[0168] In the single-phase configuration 1750 of FIG.17B, the AC / DC converter 1725 is driven in a single-phase operational mode by the control system (e.g., the control system 105). In the single-phase operational mode, the control system 105 may drive the power switching elements of the pair of half bridge circuits coupled to the first leg of the AC load / source 1710a in parallel (i.e., using the same PWM signals) and may drive the power switching elements of the pair of half bridge circuits coupled to the second leg of the AC load / source 1710a in parallel (i.e., using the same PWM signals). As used herein, the “same PWM signals” refers to PWM signals having substantially the same frequency and duty cycle (e.g., a frequency or duty cycle within 0.5 %, 1%, or 2% of each other), but each switch may receive a distinct PWM signal.

[0169] In some examples, in the single-phase configuration 1750, the control system 105 may control the AC / DC converter 1725 using a rotational reference frame (e.g., the dq reference frame) control cascaded with per phase leg regulating control in the stationary reference frame (e.g., the ab reference frame). For example, the control system 105 may translate sensed grid current from the stationary reference frame to the rotational reference frame (e.g., ig,ab to ig,dq using the Park and Clarke transforms), provide the sensed grid current and a target grid current (e.g., ig,dqto ig,dq*) to a regulator block of the control system 105 (e.g., a proportional integral (PI) regulator or proportional integral derivative (PID) regulator) to generate a control reference voltage for a voltage across an output capacitor (e.g., vc,dq*) to urge the sensed grid current towards the target grid current, and then translate the control reference voltage to the stationary reference frame (e.g., vg,dq to vg,ab using the inverse Park and Clarke transforms). The control system 105 may then provide the control reference voltage for each phase leg (e.g., vg,a or vg,b) to a local regulator of the control system 105 for each phase leg (e.g., a PI or PID controller for each phase leg), which can also receive a sensed voltage across the capacitor for each phase leg (e.g., vc,a^or^vc,b), and generate a duty cycle reference value for switching elements of each phase leg of the AC / DC converter 1725 to urge the voltage across the capacitor for each phase leg towards the corresponding control -53- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 reference voltage. The duty cycle for the first phase leg (e.g., vAC+) may be used to drive the switching elements of the pair of half bridge circuits for the first phase leg, and the duty cycle for the second phase leg (vAC‐) may be used to drive the switching elements of the pair of half bridge circuits for the second phase leg. An example control block diagram to implement control of the AC / DC converter 1725 in the single phase mode is provided in and described with respect to FIG.22.

[0170] In other examples, the control system 105 may use a modified version of the Delta-Sigma-based control, for example, as described with respect to FIGS.12 and 13 and the process 1400 of FIG. 14, to control the AC / DC converter 1725 in the single-phase configuration 1750. For example, in contrast to the illustration in FIG.12, the AC load / source 1710a would be provided in place of the DC battery 1040, the first pair of half bridge circuits could be treated as an equivalent single phase converter for the first phase leg (similar to phase leg 1012a) and the second pair of half bridge circuits could be treated as an equivalent single phase converter for the second phase leg (similar to phase leg 1012b). In a DC / DC converter mode (as shown in FIGS. 12-13), the Delta sequence may be controlled to a constant DC value. In contrast, in DC / AC converter operation, the Delta sequence is controlled to a desired grid magnitude and frequency. Thus, the single-phase DC / AC mode can use the same control layout as the DC / DC operation mode, but operate with a sinusoidal control reference. The single-phase AC grid terminals (connection points of the AC / DC converter 1725 to the single-phase AC grid) may be a line (L) and neutral (N) connector or two line connectors L1 and L2, depending on the grid. These connectors can be connected to a respective bridge circuit of one or multiple phase legs. For example, in FIG.17B, the AC / DC converter 1725 has two single-phase grid terminals, each connecting a respective pair of half-bridge circuits to a line connector L1 or L2. But, in other examples, the two single-phase grid terminals may connect a respective pair of half-bridge circuits to a line connector (L) or neutral (N), or the two single-phase grid terminals may be connected to a (one) respective half-bridge circuit and a line connector L1 or L2 (or L and N). In other configurations, the neutral (N) connector can be connected to a middle point of a capacitive divider (see FIG. 19B).

[0171] Also in the single-phase configuration 1750 of FIG.17B, the DC / DC converter 1730 may be driven using Delta-Sigma-based control by the control system (e.g., the control -54- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 system 105 implementing the control system 1205), such as described with respect to FIGS. 12 and 13 and the process 1400 of FIG. 14, or may be driven according to other DC / DC control schemes.

[0172] In the symmetric split-phase configuration 1760 of FIG. 17C, the AC / DC converter 1725 is driven in a symmetric split-phase operational mode by the control system (e.g., the control system 105). In the symmetric split-phase operational mode, the control system 105 may drive the power switching elements of the pair of half bridge circuits coupled to the first leg 1714a (VAC) in parallel (i.e., using the same PWM signals) and may drive the power switching elements of the pair of half bridge circuits coupled to the second leg 1714b (VAC) in parallel (i.e., using the same PWM signals). The PWM signals used to drive the power switching elements of the half bridge circuits of the AC / DC converter 1725 may have the same switching frequency and duty cycle; however, the AC signal on the first leg 1714a may be 180 degrees out of phase with AC signal the second leg 1714b. An example control block diagram to implement control of the AC / DC converter 1725 in the symmetric split-phase operational phase mode is provided in and described with respect to FIG.23.

[0173] In the asymmetric split-phase configuration 1780 of FIG. 17D, the AC / DC converter 1725 is driven in an asymmetric split-phase operational mode by the control system (e.g., the control system 105). In the asymmetric split-phase operational mode, the control system 105 may drive the power switching elements of one half bridge circuit coupled to the first leg 1714a (VAC) in parallel (i.e., using the same PWM signals) with another half bridge circuit coupled to the second leg 1714b (VAC). The PWM signals used to drive the power switching elements of the half bridge circuits coupled to the first and second legs 1714a,b of the AC / DC converter 1725 may have the same switching frequency and duty cycle; however, the AC signal on the first leg 1714a may be 180 degrees out of phase with AC signal on the second leg 1714b. Additionally, a third half bridge circuit of the AC / DC converter 1725 may be coupled to a neutral leg 1714c of the split phase AC system 1712, as illustrated in FIG.17D. An example control block diagram to implement control of the AC / DC converter 1725 in the asymmetric split-phase operational phase mode is provided in and described with respect to FIG.23.

[0174] The reconfigurable system 1700 may be configured in the three-phase configuration 1740 based on the connection to a three-phase AC system (e.g., AC system -55- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 1705) as illustrated in FIG.17A, may be configured in the single-phase configuration 1750 based on the connection to a single-phase AC system (e.g., AC system 1710) as illustrated in FIG.17B, may be configured in the symmetric split-phase configuration 1760 based on the connection to a split-phase AC system (e.g., AC system 1712) as illustrated in FIG.17C, and may be configured in the asymmetric split-phase configuration 1780 based on the connection to a split-phase AC system (e.g., AC system 1712) as illustrated in FIG.17D. The control system that drives the reconfigurable system 1700 (e.g., the control system 105) may detect or determine the type of AC system connected to the AC / DC converter 1725 (e.g., single, three-phase, symmetric split-phase, and asymmetric split-phase) and, in response, control the reconfigurable system 1700 to be in the configuration that corresponds to the type of AC system that is connected.

[0175] Turning to FIGS. 18A, 18B, 18C, and 18D, the reconfigurable system 1800 includes the four-leg AC / DC converter 1725 as described above with respect to FIGS.17A- 17D, and a DC / DC converter 1830. The DC / DC converter 1830 is similar to the DC / DC converter 1010b (e.g., of FIG. 10B), including having one half bridge circuit as described above. The reconfigurable system 1800 is illustrated in a three-phase configuration 1840 in FIG. 18A, in a single-phase configuration 1850 in FIG. 18B, in a symmetric split-phase configuration 1860 in FIG.18C, and in an asymmetric split-phase configuration 1880 in FIG. 17D.

[0176] In the three-phase configuration 1840 of FIG.18A, the AC / DC converter 1725 may be driven in a three-phase operational mode by a control system (e.g., the control system 105 implementing the control system 505) using delta-sigma-based control, such as described with respect to FIGS.5 and 6 and the process 700 of FIG.7. For example, this delta- sigma-based control, an asymmetrical control mode, may be used when the AC system 1705 is unbalanced. In other examples, when the AC system 1705 is balanced, the control system may control the AC / DC converter 1725 using a symmetric control mode. In the symmetric control mode, as described with respect to FIG.17A, the control system 105 may control the AC / DC converter 1725 by driving three of the half bridge circuits and corresponding phase legs 1705a-c, and disabling the neutral phase leg VAC-nand corresponding half bridge circuit. -56- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 Also in the three-phase configuration 1840 of FIG.18A, the DC / DC converter 1830 may be driven according to a DC / DC control scheme.

[0177] In the single-phase configuration 1850 of FIG.18B, the AC / DC converter 1725 is driven in a single-phase operational mode by the control system (e.g., the control system 105). In the single-phase operational mode, the control system 105 may drive the power switching elements of the pair of half bridge circuits coupled to the first leg of the AC load / source 1710a in parallel (i.e., using the same PWM signals) and may drive the power switching elements of the pair of half bridge circuits coupled to the second leg of the AC load / source 1710a in parallel (i.e., using the same PWM signals).

[0178] In some examples, the control system 105 may control the AC / DC converter 1725 in the single-phase operational mode using a rotational reference frame (e.g., the dq reference frame) control cascaded with per phase leg regulating control in the stationary reference frame (e.g., the ab reference frame), as described with respect to FIG.17B. An example control block diagram to implement control of the AC / DC converter 1725 in the single phase mode is provided in and described with respect to FIG.22. In other examples, the control system 105 may use a modified version of the Delta-Sigma-based control to control the AC / DC converter 1725 in the single-phase configuration 1850, as described with respect to FIG.17B.

[0179] Also in the single-phase configuration 1850 of FIG.18B, the DC / DC converter 1730 may be driven according to a DC / DC control scheme, like in the three-phase configuration 1840.

[0180] In the symmetric split-phase configuration 1860 of FIG. 18C, the AC / DC converter 1725 is driven in a symmetric split-phase operational mode by the control system (e.g., the control system 105). In the symmetric split-phase operational mode, the control system 105 may drive the power switching elements of the pair of half bridge circuits coupled to the first leg 1714a (VAC) in parallel (i.e., using the same PWM signals) and may drive the power switching elements of the pair of half bridge circuits coupled to the second leg 1714b (VAC) in parallel (i.e., using the same PWM signals). The PWM signals used to drive the power switching elements of the half bridge circuits of the AC / DC converter 1725 may have the same switching frequency and duty cycle; however, the AC signal on the first leg 1714a may be 180 degrees out of phase with AC signal the second leg 1714b. An example -57- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 control block diagram to implement control of the AC / DC converter 1725 in the symmetric split-phase operational phase mode is provided in and described with respect to FIG.23.

[0181] In the asymmetric split-phase configuration 1880 of FIG. 18D, the AC / DC converter 1725 is driven in an asymmetric split-phase operational mode by the control system (e.g., the control system 105). In the asymmetric split-phase operational mode, the control system 105 may drive the power switching elements of one half bridge circuit coupled to the first leg 1714a (VAC) in parallel (i.e., using the same PWM signals) with another half bridge circuit coupled to the second leg 1714b (VAC). The PWM signals used to drive the power switching elements of the half bridge circuits coupled to the first and second legs 1714a,b of the AC / DC converter 1725 may have the same switching frequency and duty cycle; however, the AC signal on the first leg 1714a may be 180 degrees out of phase with AC signal on the second leg 1714b. Additionally, a third half bridge circuit of the AC / DC converter 1725 may be coupled to a neutral leg 1714c of the split phase AC system 1712, as illustrated in FIG.17D. An example control block diagram to implement control of the AC / DC converter 1725 in the asymmetric split-phase operational phase mode is provided in and described with respect to FIG.23.

[0182] The reconfigurable system 1800 may be configured in the three-phase configuration 1840 based on the connection to a three-phase AC system (e.g., AC system 1705) as illustrated in FIG.18A, may be configured in the single-phase configuration 1850 based on the connection to a single-phase AC system (e.g., AC system 1710) as illustrated in FIG.18B, may be configured in the symmetric split-phase configuration 1860 based on the connection to a split-phase AC system (e.g., AC system 1712) as illustrated in FIG.18C, and may be configured in the asymmetric split-phase configuration 1880 based on the connection to a split-phase AC system (e.g., AC system 1712) as illustrated in FIG.18D. The control system that drives the reconfigurable system 1800 (e.g., the control system 105) may detect or determine the type of AC system connected to the AC / DC converter 1725 (e.g., single or three-phase) and, in response, control the reconfigurable system 1800 to be in the configuration that corresponds to the type of AC system that is connected.

[0183] Turning to FIGS. 19A and 19B, the reconfigurable system 1900 includes a three-leg AC / DC converter 1925 and a DC / DC converter 1730. The three-leg AC / DC -58- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 converter 1925 may be similar to the four-leg power converter 304 (e.g., of FIGS.3), except lacks the fourth half bridge for the neutral leg of the AC system 1705. As illustrated in FIGS. 19A-19B, in place of the fourth half bridge, two capacitors may be provided across DC rails, with a midpoint node connecting to the neutral leg of the AC system 1705. The DC / DC converter 1730 is similar to the DC / DC converter 1010a (e.g., of FIG.10A), including having two half bridge circuits as described above. The reconfigurable systems 1700 is illustrated in a three-phase configuration 1940 in FIG.19A and in a single-phase configuration 1950 in FIG.19B.

[0184] In the three-phase configuration 1940 of FIG.19A, the AC / DC converter 1925 is driven in a three-phase operational mode by a control system (e.g., the control system 105 implementing the control system 505) using delta-sigma-based control, such as described with respect to FIGS.5 and 6 and the process 700 of FIG.7. However, because the fourth half- bridge is not present in the AC / DC converter 1925, the sigma component (σ) may be eliminated or ignored by the control system 505. Also in the three-phase configuration 1940 of FIG.19A, the DC / DC converter 1730 may be driven using Delta-Sigma-based control by the control system (e.g., the control system 105 implementing the control system 1205), such as described with respect to FIGS. 12 and 13 and the process 1400 of FIG. 14, or may be driven according to other DC / DC control schemes.

[0185] In the single-phase configuration 1950 of FIG.19B, the AC / DC converter 1925 is driven in a single-phase operational mode by the control system (e.g., the control system 105). In the single-phase operational mode, the control system 105 may drive the power switching elements of the half bridge circuits coupled to the first leg of the AC load / source 1710a in parallel (i.e., using the same PWM signals) and a midpoint node of the two capacitors provided across DC rails may be connected to the neutral leg of the AC load / source 1710a. In some examples, the control system 505 may control the three half bridge circuits using delta-sigma-based control, such as described with respect to FIGS.5 and 6 and the process 700 of FIG.7. However, because the fourth half-bridge is not present in the AC / DC converter 1925, the sigma component (σ) may be eliminated or ignored by the control system 505. Also in the single-phase configuration 1950 of FIG. 19B, the DC / DC converter 1730 may be driven using Delta-Sigma-based control by the control system (e.g., the control system 105 implementing the control system 1205), such as described with -59- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 respect to FIGS.12 and 13 and the process 1400 of FIG.14, or may be driven according to other DC / DC control schemes.

[0186] The reconfigurable system 1900 may be configured in the three-phase configuration 1940 based on the connection to a three-phase AC system (e.g., AC system 1705) as illustrated in FIG. 19A, and may be configured in the single-phase configuration 1950 based on the connection to a single-phase AC system (e.g., AC system 1710) as illustrated in FIG.19B. The control system that drives the reconfigurable system 1900 (e.g., the control system 105) may detect or determine the type of AC system connected to the AC / DC converter 1925 (e.g., single or three-phase) and, in response, control the reconfigurable system 1900 to be in the configuration that corresponds to the type of AC system that is connected.

[0187] In some examples of each of the reconfigurable systems 1700, 1800, and 1900 of FIGS.17A-19B, the DC / DC converter may be selectively enabled or bypassed, for example, as described with respect to FIG.11 using contactor assembly 1105.

[0188] In some examples, an external plug that couples to the AC / DC converter 1725 or 1925 may make and / or break the connections to the AC system 1705 and / or 1710 illustrated in FIGS. 17A-19B. For example, an external plug may function this way when reconfigurable systems 1700, 1800, and / or 1900 are used with or integrated into an electric vehicle, where the DC battery 1715a is an electric battery for powering a traction motor of the electric vehicle. In some such systems, the AC system 1705 and 1710 are example AC grids to which the reconfigurable systems 1700, 1800, and / or 1900 may connect to receive charging power to charge the DC battery 1715a. With reference to FIGS.17A, 18A, and 19A, a three-phase plug may be used to provide the connections between the AC system 1705 (e.g., the AC legs 1705a, 1705b, 1705c, 1705n) and the AC connection nodes of the AC / DC converters 1725, 1925, as illustrated. With reference to FIGS.17B, 18B, and 19B, a single- phase plug may be used to provide the connections between the AC system 1710 (e.g., the legs VAC+ and VAC-) and the AC connection nodes of the AC / DC converters 1725, 1925, as illustrated.

[0189] Of the reconfigurable systems 1700, 1800, and 1900, the reconfigurable system 1700 may be more compact and provide more flexibility for mitigating common mode challenges, as the neutral leg can be actively controlled (using delta-sigma control as -60- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 described with respect to FIGS.5-7) and the DC bus voltage with respect to chassis ground can be controlled (using Delta-Sigma control as described with respect to FIGS.10A-14). The reconfigurable system 1800 may be less expensive, due to reduced hardware, relative to the reconfigurable system 1700, but, with one of the DC / DC legs eliminated, the reconfigurable system 1800 loses the ability to control the internal DC bus of the converters 1725, 1830 because the bus is linked to the DC system 1715, and the reconfigurable system 1800 cannot directly control the chassis voltage with respect to earth ground. The reconfigurable system 1900 may be less expensive, due to reduced hardware, relative to the reconfigurable system 1700, but may be implemented with filters having larger capacitors (e.g., at the neutral leg of the AC system in place of the fourth half bridge) to passively balance the AC system, rather than actively balance, like in the reconfigurable systems 1700 and 1800.

[0190] FIG. 20 illustrates a process 2000 for operating a reconfigurable power converter. The process 2000 is described as being carried out by the power converter system 100 implemented as one of the reconfigurable systems 1700, 1800, or 1900. However, in some embodiments, the process 2000 is implemented by another power converter system. Additionally, although the blocks of the process 2000 are illustrated in a particular order, in some embodiments, one or more of the blocks may be executed partially or entirely in parallel, may be executed in a different order than illustrated in FIG.20, or may be bypassed.

[0191] In block 2005, a control system determines an operational mode for an AC / DC power converter to be a three-phase mode having three AC phases, where the AC / DC power converter is part of a reconfigurable power converter system including the AC / DC power converter and a DC / DC power converter. In some examples, the control system further determines whether the three-phase mode is a symmetric control mode or an asymmetric control mode. Here, the AC / DC power converter (e.g., the AC / DC converter 1725 or 1925 in FIGS. 17A-19B) includes a DC bus and AC connection nodes, the AC / DC power converter having phase legs including a first phase leg, a second phase leg, and a third phase leg, each of the first, second, and third phase legs having a respective LC filter, respective power switching elements, and a respective AC connection node of the AC connection nodes. Also, the DC / DC power converter (e.g., the DC / DC converter 1730 or 1830 in FIGS. 17A-19B) includes DC nodes coupled to the DC bus and with a battery connection section including a -61- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 positive battery terminal node and a negative battery terminal node, the DC / DC power converter including a first half bridge including first power switching elements and a first LC filter, wherein the first LC filter is connected to the positive battery terminal node.

[0192] As an example, in block 2005, the control system 105 (of FIG.1) determines a type of AC system coupled to the AC / DC power converter to be a three-phase AC system. For example, the control system 105 controlling the reconfigurable system 1700, 1800, or 1900 may determine that the AC / DC converter 1725 or 1925 is coupled to the three-phase AC system 1705. To make the determination, the control system 105 may, for example, receive an indication of an AC system type, which indicates that a coupled AC system is a three-phase system, from the I / O interface 142 (e.g., based on a user input), or may detect using one or more sensors 140 on the legs of the coupled AC system (e.g., on the legs of the AC system 1705) that voltage or current is changing on the legs in a manner indicating a three-phase AC system (e.g., the voltage or current on each leg being 120 degrees phase shifted with respect to the other legs). In some examples, as part of this determination that the AC system is a three-phase AC system, the control system 105 uses similar technique to further determine whether the AC system 1705 is balanced (suggesting a symmetric control mode) or unbalanced (suggesting an asymmetric control mode).

[0193] In block 2010, the control system controls the AC / DC power converter in the three-phase mode. In the three-phase mode, the first, second, and third phase legs each correspond to a respective phase of the three AC phases, and the AC connection node of the first phase leg is connected to a first node of a three-phase AC system, the AC connection node of the second phase leg is connected to a second node of the three-phase AC system, and the AC connection node of the third phase leg is connected to a third node of the three- phase AC system. For example, in FIG.17A and 18A, a first half bridge of the AC / DC converter 1725 is connected via a first AC connection node to the first AC phase leg 1705a (VAC-a), a second half bridge of the AC / DC converter 1725 is connected via a second AC connection node to the second AC phase leg 1705b (VAC-b), and a third half bridge of the AC / DC converter 1725 is connected via a third AC connection node to the third AC phase leg 1705c (VAC-c). Similarly, in FIG.19A, a first half bridge of the AC / DC converter 1925 is connected via a first AC connection node to the first AC phase leg 1705a (VAC-a), a second half bridge of the AC / DC converter 1925 is connected via a second AC connection node to the second AC phase leg -62- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 1705b (VAC-b), and a third half bridge of the AC / DC converter 1925 is connected via a third AC connection node to the third AC phase leg 1705c (VAC-c).

[0194] Further, to control the AC / DC converter 1725 in the three-phase mode (in the reconfigurable systems 1700 and 1800 of FIGS.17A and 18A), the control system 105 may drive the AC / DC converter 1725 using delta-sigma-based control, such as described with respect to FIGS.5 and 6 and the process 700 of FIG.7. For example, this delta-sigma-based control, an asymmetrical control mode, may be used when the control system 105 determines that the AC system to which the AC / DC converter 1725 is connected is unbalanced. In other examples, when the control system 105 determines that the AC system to which the AC / DC converter 1725 is connected is balanced, the control system may control the AC / DC converter 1725 using a symmetric control mode. In the symmetric control mode, as described with respect to FIG. 17B, the control system 105 may control the AC / DC converter 1725 by driving three of the half bridge circuits and corresponding phase legs 1705a-c, and disabling the neutral phase leg VAC-nand corresponding half bridge circuit. To control the AC / DC converter 1925 in the three-phase mode (in the reconfigurable system 1900 of FIG.19A), the control system 105 may drive the AC / DC converter 1925 using a three- phase inverter control scheme.

[0195] Further, to control the DC / DC converter 1730 in the three-phase mode (in the reconfigurable systems 1700 and 1900 of FIGS.17A and 19A), the control system 105 may drive the DC / DC converter 1730 using Delta-Sigma-based control by the control system (e.g., the control system 105 implementing the control system 1205), such as described with respect to FIGS.12 and 13 and the process 1400 of FIG.14, or may be driven according to other DC / DC control schemes. To control the DC / DC converter 1830 in the three-phase mode (in the reconfigurable system 1800 of FIG.18A), the control system 105 may drive the DC / DC power converter 1835 using a DC / DC control scheme.

[0196] In block 2015, the control system determines the operational mode for the AC / DC power converter to be a single-phase mode having a single AC phase. For example, the control system 105 (of FIG. 1) determines a type of AC system coupled to the AC / DC power converter to be a single-phase AC system. For example, the control system 105 controlling the reconfigurable system 1700, 1800, or 1900 may determine that the AC / DC converter 1725 or 1925 is coupled to the single-phase AC system 1710. To make the -63- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 determination, the control system 105 may, for example, receive an indication of an AC system type, which indicates that a coupled AC system is a single-phase system, from the I / O interface 142 (e.g., based on a user input), or may detect using one or more sensors 140 on the legs of the coupled AC system (e.g., on the legs of the AC system 1710) that voltage or current is changing on the legs in a manner indicating a single-phase AC system. For example, voltage or current at the AC connection node of a first pair of half bridges of the AC / DC converter 1725 or 1925 are in phase with one another, and phase-shifted 180 degrees with respect to voltage or current on the AC connection node of the other pair of half bridges (for reconfigurable systems 1700 and 1800) or of the third half bridge (for reconfigurable system 1900).

[0197] In block 2020, the control system controls the AC / DC power converter in the single-phase mode. In the single-phase mode, the first and second phase legs each correspond to the single AC phase and the AC connection nodes of the first and second phase legs are connected to a first node of a single-phase AC system. For example,

[0198] For example, in FIG.17B and 18B, a first and a second half bridge of the AC / DC converter 1725 are connected via a first and second AC connection node to a first leg or node (VAC+) of the single-phase AC load / source 1710a, and a third and a fourth half bridge of the AC / DC converter 1725 are connected via a third and fourth AC connection node to the second leg or node (VAC-) of the single-phase AC load / source 1710a. Similarly, in FIG.19B, a first and a second half bridge of the AC / DC converter 1925 are connected via a first and second AC connection node to a first leg or node (VAC+) of the single-phase AC load / source 1710a, and a third half bridge of the AC / DC converter 1925 is connected via a third AC connection node to the second leg or node (VAC-) of the single-phase AC load / source 1710a and to a midpoint node of the capacitor pair in the AC / DC converter 1925 (the capacitor pair provided in place of the fourth half bridge that is found in the AC / DC converter 1725).

[0199] Further, to control the AC / DC converter 1725 in the single-phase mode (in the reconfigurable systems 1700 and 1800 of FIGS.17A and 18A), the control system 105 may drive the power switching elements of the pair of half bridge circuits coupled to the first leg of the AC load / source 1710a in parallel (i.e., using the same PWM signals) and may drive the power switching elements of the pair of half bridge circuits coupled to the second leg of the AC load / source 1710a in parallel (i.e., using the same PWM signals). The PWM signals for the -64- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 two pairs of half bridge circuits may be 180 degrees out-of-phase with one another. To control the AC / DC converter 1925 in the single-phase mode (in the reconfigurable system 1900 of FIG. 19A), the control system 105 may drive the power switching elements of the pair of half bridge circuits coupled to the first leg of the AC load / source 1710a in parallel (i.e., using the same PWM signals) and may separately drive the power switching elements of the third half bridge circuit coupled to the second leg of the AC load / source 1710a. The PWM signals for the pair of half bridge circuits may be 180 degrees out-of-phase with the PWM signals for the third half bridge circuit.

[0200] The above-described single-phase mode may be referred to as a parallel single-phase mode because at least two half bridges of the AC / DC converter 1725, 1925 have AC nodes connected to a leg of the AC load / source 1710a and are driven in parallel.

[0201] Further, to control the DC / DC converter 1730 in the single-phase mode (in the reconfigurable systems 1700 and 1900 of FIGS.17B and 19B), the control system 105 may drive the DC / DC converter 1730 using Delta-Sigma-based control, for example, as described with respect to FIGS.12 and 13 and the process 1400 of FIG.14, or may be driven according to other DC / DC control schemes. To control the DC / DC converter 1830 in the single-phase mode (in the reconfigurable system 1800 of FIG.18B), the control system 105 may drive the DC / DC power converter 1835 using a DC / DC control scheme.

[0202] In some examples of the process 2000, the control system may further control the AC / DC power converter in a non-parallel single-phase mode. For example, with respect to the reconfigurable systems 1700 and 1800 of FIGS. 17B and 18B, in the non-parallel single-phase mode, the first half bridge may be connected to the first leg of the AC load / source 1710a (VAC+), the second half bridge may be idle (e.g., and disconnected from the AC load / source 1710a), the third half bridge may be connected to the second leg of the AC load / source 1710a (VAC-), and the fourth half bridge may be idle (e.g., and disconnected from the AC load / source 1710a). As another example, with respect to the reconfigurable system 1900 of FIG.19B, in the non-parallel single-phase mode, the first half bridge may be connected to the first leg of the AC load / source 1710a (VAC+), the second half bridge may be idle (e.g., and disconnected from the AC load / source 1710a), the third half bridge may be connected to the second leg of the AC load / source 1710a (VAC-), and the midpoint node of the capacitor pair in the AC / DC converter 1925 (the capacitor pair provided in place of the -65- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 fourth half bridge that is found in the AC / DC converter 1725) may be disconnected or connected to the second leg of the AC load / source 1710a (VAC-). To control the AC / DC converter 1725 or 1925 in the non-parallel single-phase mode (in the reconfigurable systems 1700, 1800, or 1900 of FIGS.17B, 18B, and 19B), the control system 105 may drive the power switching elements of the first half bridge circuit coupled to the first leg of the AC load / source 1710a and may drive the power switching elements of the third half bridge circuit coupled to the second leg of the AC load / source 1710a, where the PWM signals for the first and third half bridge circuits may be 180 degrees out-of-phase with one another.

[0203] In some examples of the process 2000, the control system may selectively enable or bypass the DC / DC converter (e.g., the DC / DC converter 1730 or 1830 of FIGS.17A- 19B), for example, as described with respect to FIG.11 by controlling a contactor assembly included in the reconfigurable systems 1700, 1800, and / or 1900, similar to the contactor assembly 1105. For example, the DC / DC converter may have a defined operating range (e.g., defined by a low and high voltage threshold). When DC power on the DC system 1715 is at a voltage level within the operating range of the DC / DC converter, the control system may control the contactor assembly to the bypass state so that the DC / DC converter is bypassed. However, when DC power on the DC system 1715 is at a voltage level above or below the operating range of the DC / DC converter, the control system may control the contactor assembly to the DC conversion state so that the DC / DC converter may convert (boost or buck) the DC voltage to be within the operating range of the DC system 1715.

[0204] While the process 2000 is described with respect to controlling an AC / DC converter in a three-phase mode (symmetric or asymmetric) and a single-phase mode, in some examples, the process 2000 (and the control system 105) may additionally or alternatively be used to control an AC / DC converter in a split phase mode, which may be symmetric (see, e.g., FIGS. 17C and 18C) or asymmetric (see, e.g., FIGS. 17D and 18D). For example, FIG. 21 illustrates another process 2100 for operating a reconfigurable power converter. The process 2100 is described as being carried out by the power converter system 100 implemented as one of the reconfigurable systems 1700 or 1800. However, in some embodiments, the process 2100 is implemented by another power converter system. Additionally, although the blocks of the process 2100 are illustrated in a particular order, in -66- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 some embodiments, one or more of the blocks may be executed partially or entirely in parallel, may be executed in a different order than illustrated in FIG.21, or may be bypassed.

[0205] In block 2105, a control system (e.g., the control system 105) determines an operational mode for an AC / DC power converter (e.g., the AC / DC power converter 1725, 1825, or 1925). The operational mode may be selected from a plurality of potential operational modes including any combination of the following operational modes: a single phase operational mode, a symmetric three-phase operational mode, an asymmetric (delta- sigma) three-phase operational mode, an asymmetric split-phase operational mode, and a symmetric split-phase operational mode.

[0206] As an example, in block 2105, the control system 105 determines the operational mode based on determining a type of AC system coupled to the AC / DC power converter. For example, the control system 105 may determine whether the coupled AC system is a three-phase balanced AC system, a three-phase unbalanced AC system, a split- phase balanced AC system, a split-phase unbalanced AC system, or a single-phase AC system. The control system 105 then determines the operational mode to be the operational mode that corresponds to the determined type of AC system. For example, the control system 105 may determine: (1) that the AC / DC converter 1725 is coupled to the three-phase AC system 1705 (unbalanced) and determine the operational mode to be an asymmetric (delta-sigma) three-phase operational mode, (2) that the AC / DC converter 1725 is coupled to the three- phase AC system 1705 (balanced) and determine the operational mode to be a symmetric three-phase operational mode, (3) that the AC / DC converter 1725 is coupled to the split- phase AC system 1712 (balanced) and determine the operational mode to be an symmetric split-phase operational mode, (4) that the AC / DC converter 1725 is coupled to the split- phase AC system 1712 (unbalanced) and determine the operational mode to be an asymmetric split-phase operational mode, or (5) that the AC / DC converter 1725 is coupled to the single-phase AC system 1710 (balanced or unbalanced) and determine the operational mode to be a single phase operational mode. The control system 105 may determine the type of AC system to which the AC / DC converter 1725 is coupled by using one or more sensors 140 on the legs of the coupled AC system (e.g., on the legs of the AC system 1705, 1710, 1712) to detect that voltage or current is changing on the legs in a manner indicating one of the types of AC systems. -67- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272

[0207] As another example, in block 2105, the control system 105 determines the operational mode in response to receipt of an indication of the type of AC system from the I / O interface 142 (e.g., based on a user input).

[0208] Upon determining the operational mode in block 2105, the control system 105 proceeds to the corresponding block 2110, 2115, 2120, 2125, or 2130 to control the AC / DC converter 1725 in the determined operational mode. For example, in response to determining that the operational mode is the single phase operational mode, the control system 105 proceeds to block 2110 to control the AC / DC converter in the single phase operational mode. Similarly, in response to determining that the operational mode is the symmetric three-phase operational mode, the control system 105 proceeds to block 2115 to control the AC / DC converter in the symmetric three-phase operational mode; in response to determining that the operational mode is the asymmetric (delta-sigma) three-phase operational mode, the control system 105 proceeds to block 2120 to control the AC / DC converter in the asymmetric (delta-sigma) three-phase operational mode; in response to determining that the operational mode is the symmetric split-phase operational mode, the control system 105 proceeds to block 2125 to control the AC / DC converter in the symmetric split-phase operational mode; and in response to determining that the operational mode is the asymmetric split-phase operational mode, the control system 105 proceeds to block 2130 to control the AC / DC converter in the asymmetric split-phase operational mode.

[0209] Control of the AC / DC power converter by the control system 105 in these various modes of the blocks 2110, 2115, 2120, 2125, and 2130 have at least in part been previously described herein (e.g., with respect to FIG.5 and 17A-18D) and that description similarly applies to these blocks and is thus not restated. Further, additional diagrams of control logic for controlling an AC / DC power converter (e.g., the AC / DC power converter 1725) in a single phase operational mode and a symmetric split-phase operational mode are provided in FIGS.22 and 23, respectively, and discussed further below.

[0210] In some examples, the AC system to which the AC / DC power converter 1725 changes (e.g., one or more times). In such examples, the process 2110 may return to block 2105 such that the control system 105 can determine a next operational mode for the AC / DC power converter 1725 and, then, control the AC / DC power converter 1725 in that next operational mode. Accordingly, in some examples, the control system 105 may control the -68- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 AC / DC power converter 1725 in each of the five operational modes illustrated in FIG.21 at different instances in time (e.g., in any order) or in each of any subset of the five operational modes illustrated in FIG.21 at different instances in time.

[0211] FIG. 22 illustrates a power converter system 2200 implementing a single- phase AC / DC conversion. The power converter system 2200 includes a control system 2205 and a four-leg AC / DC power converter, which is illustrated as the four-leg power converter 1725 but may also be the four-leg power converter 304. With reference also to FIG. 1, the power converter system 2200 is an example of the power converter system 100 and the control system 2205 is an example of the control system 105. Although not illustrated, in some examples, the four-leg power converter 1725 is also coupled to a DC / DC converter, as discussed with respect to FIGS.10A-10B. In the diagram of FIG.22, to simplify the control, the grid‐side filtering inductor and the grid inductance are merged together into one lumped component ^^^inserted on the grid side.

[0212] Generally, to implement the single-phase operational mode, the control system 2205 senses electrical operational characteristics for the four-leg power converter 1725, uses the Clarke-Park transformation described above to generate control reference targets based in the dq reference frame, and controls the four-leg power converter 1725 based on the control reference targets. The control system 2205 includes a first transformation block 2210 to translate received electrical characteristics from the stationary pn reference frame to the dq reference frame, a phase-locked‐loop (PLL) block 2212 to generate a phase angle (theta), current control blocks 2218a-c, a second transformation block 2220, and a variable frequency critical soft switching (VFCSS) block 2222.

[0213] More specifically, in the single-phase operational mode, the four-leg power converter 1725 may be reconfigured by interleaving the phases together in order to create two pairs that can be connected to the AC source 1710a, similar to as described with respect to FIGS.17B and 18B. The control system 2205 regulates in a synchronous reference frame using the Park transformation and operates in a dq0 domain. For example, the first transformation block 2210 may translate the current and voltage of the phase (p) and neutral (n) legs using the Clarke transformation into the αβ0 reference frame. The first -69- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 transformation block 2210 may then apply the Park transformation to translate the current and voltage from the αβ0 reference frame to the dq0 reference frame. In the phase domain, the state-space equations for the pn system can be expressed as: ^^^^^,^^ ൌ^ ^^^^^^௫,^^െ ^ ^^^^^^^,^^(11a)

[0214] where iL,pn is the inductor current, vx,pn is the voltage at the output of the inverter leg, vc,pnis the voltage across the filtering capacitor, ig,pnis the grid output current, and vg,pn is the grid voltage. The matrix I ∈ R2×2 is the identity matrix. Lf , Cf and Lg are the filter inductance, filter capacitance and grid inductance, respectively. The subscript of the variables are used to identify the conductor wire and indicates phase (p) and neutral (n). Given the phase domain quantities, the αβ0 voltages are obtained as follows: ^^ఈ 1 െ^^ ^1^ ^^ ^^ ^ ^^

[0215] where,component (0) is assigned to the voltage of the neutral conductor, the α component is obtained by shifting the phase voltage down with respect to the neutral voltage, while the β component is obtained by applying a 90° phase shift to the α component thus creating a fictitious axis. This phase shift is represented to the exponential term where T is the period of the voltage of the AC system 1710a and s is the Laplace operator. Given the αβ0 quantities, the Park transformation is then applied to obtain the dq0 system. The Park transformation is expressed as: cos^^ sin^^ 0^^ ^^^^^^^^ ^ ^^ Attorney Docket No.: 175073.00272

[0216] The current control blocks 2218a-c, also referred to as regulators 2218a-c, operate in the dq0 domain, where the d‐loop is used to control the active power, the q-loop is used to control the reactive power, and the 0-loop is used to set the common mode voltage, which may be kept fixed at Vdc / 2 to suppress leakage current circulation. Given the output of the regulators 2218a-c, the second transformation block 2220 may compute duty cycles (Dpn) for the switches of each leg of the converter 1725 by applying the inverse Park transformation to move back from the dq0 domain to αβ0 domain and then performing the inverse operation of equation (12) neglecting the β component. Specifically, the mathematical operation is expressed as: ^^^^^ ^ ^^^ ^ ൌ ^1 10 1^ ^ ఈ^^^^ (14)

[0217] The second may, similar to the secondtransformation block 520 of FIGS.5-6, include a reference frame translation stage (see, e.g., block 520a of FIG.6, although different reference frame translations are performed) and a regulator stage (see, e.g., regulators 520b of FIG.6) to generate duty cycles from the input voltage reference values. The VFCSS block 2222 of the control system 2205 uses the generated duty cycles (Dp, Dn), along with the bus voltage Vdc and inductor current IL, to compute the switching frequencies fsw,pn using the VFCSS technique, as described with respect to the VFCSS block 522 and FIG.5.

[0218] FIG.23 illustrates a power converter system 2300 implementing a split-phase AC / DC conversion using a symmetric split-phase operational mode. The power converter system 2300 includes a control system 2205 and a four-leg AC / DC power converter, which is illustrated as the four-leg power converter 1725 but may also be the four-leg power converter 304. With reference also to FIG.1, the power converter system 2300 is an example of the power converter system 100 and the control system 2305 is an example of the control system 105. Although not illustrated, in some examples, the four-leg power converter 1725 is also coupled to a DC / DC converter, as discussed with respect to FIGS. 10A-10B. In the -71- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 diagram of FIG. 23, to simplify the control, the grid‐side filtering inductor and the grid inductance are merged together into one lumped component ^^^inserted on the grid side.

[0219] Generally, to implement the symmetric split-phase operational mode, the control system 2305 senses electrical operational characteristics for the four-leg power converter 1725, uses the Clarke-Park transformation described above to generate control reference targets based in the dq reference frame, and controls the four-leg power converter 1725 based on the control reference targets. The control system 2305 includes a first transformation block 2310 to translate received electrical characteristics from the stationary pn reference frame to the dq reference frame, a phase-locked-loop (PLL) block 2312 to generate a phase angle (theta), current control blocks 2318a-c, a second transformation block 2320, and a variable frequency critical soft switching (VFCSS) block 2322.

[0220] More specifically, in the symmetric split-phase operational mode, the four-leg power converter 1725 may be reconfigured to connect a first pair of half bridge circuits together at their respective AC connection nodes to connect to a first phase 1712a of the split-phase AC system and a second pair of half bridge circuits together at their respective AC connection nodes to connect to a second phase 1712b of the split-phase AC system. In the symmetric split-phase operational mode, the four-leg power converter 1725 can be treated similar to a single-phase device by making some adjustment on the definition of the αβ0 reference frame. In particular, given the phase domain quantities, which are the same as the ones described in the single-phase case, the αβ0 voltages may be obtained as follows: ^ ଶെ ^é ଶ ù

[0221] where,as the average voltage of the two phases, while the α component may be obtained as the differential component. The β component may be calculated by shifting the α component 90° as in the single-phase case. Then, the Park transformation, described above, may be applied to obtain the dq0 -72- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 system. In the control system 2305, like the single-phase case, the d-loop is used to control the active power, the q-loop is used to control the reactive power, and the 0-loop is used to keep the common mode voltage stable. Given the outputs of the current control blocks 2318a-c, also referred to as the regulators 2318a-c, the second transformation block 2320 may compute duty cycles (Dpn) for the switches of each leg of the converter 1725 by applying the inverse Park transformation to move back from the dq0 domain to αβ0 domain and then performing the inverse operation of the equation (15), which is expressed as: ^^ ^^ 1 1^^ఈ^^^ ^ ൌ ^െ1 1^ ^^^^^ (16)

[0222] As shown in FIG. 17D, the converteralso be used to implement a split-phase AC / DC conversion using an asymmetric split-phase operational mode. Similarly, the power converter system 2300 may be used to implement split-phase AC / DC conversion using an asymmetric split-phase operational mode (e.g., when the split-phase AC system including first and second phases 1712a-b is unbalanced). In this configuration, half bridge 1725a may be coupled to the first phase 1712a, the half bridge 1725c may be coupled to the second phase 1712b, and the half bridge 1712b may be coupled to the neutral line 1714c.

[0223] In the asymmetric split-phase operational mode, given the presence of an extra conductor (neutral line 1714c) to be controlled, the zero sequence component is assigned to the voltage of the neutral conductor and the other two conductors can be renamed as phase-1 and phase-2 instead of phase and neutral, because the newly conductor available will be the effective neutral connection. The outputs of the regulators 2318a-c may then be provided to the second transformation block 2320. Then, using the second transformation block 2320, the αβ0 voltages are obtained as follows: ^^ఈ 1 െ1^^ ^^^^

[0224] Theby considering the same α component and shifting it by 180°. The active phases voltage reference can be expressed as: -73- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 ^^^^ 1 1^^ ^ ^^൩ ൌ ^ ൩ ఈ^ଶ െ1 1 ^^ (18) ^^ ^^^^

[0225] The second may, similar to the second transformation block 520 offrame translation stage (see, e.g., block 520a of FIG.6, although different reference frame translations are performed) and a regulator stage (see, e.g., regulators 520b of FIG.6) to generate duty cycles from the input voltage reference values. Thus, the output of the second transformation block 2320 may include a duty cycle for each of the three phase legs, indicated as duty cycles D1, D2, Dn. The VFCSS block 2322 of the control system 2205 uses the generated duty cycles (D1, D2, Dn), along with the bus voltage Vdc and inductor current IL, to compute the switching frequencies fsw,pnusing the VFCSS technique, as described with respect to the VFCSS block 522 and FIG. 5.

[0226] The various power converters disclosed herein may be used in various contexts. In some examples, one or more of the power converters 115, 304, 1010, 1015, 1700, 1800, 1900, or corresponding systems including such power converters, is implemented in an electric vehicle. For example, with reference to FIG.5, the four-leg power converter 304 may be incorporated into an electric vehicle, and the control system 505 is further configured to drive the power switching elements of the four phase legs 402a-n in accordance with the control reference targets Vg,a*, Vg,b*, Vg,c*, and Vg,n* (see, e.g., block 715 of FIG.7) to rectify power AC power or invert DC power. For example, in a rectification mode, when the electric vehicle (or, more particularly, the power converter of the electric vehicle) is coupled to an AC source (e.g., via a plug connected to an AC grid) via AC connection nodes, the power converter rectifies an AC signal received via the AC connection nodes and outputs DC charging power via the DC bus 314 to charge an electric vehicle battery (e.g., the battery 310). Accordingly, the four-leg power converter 304 may be referred to as an on- board charger or on-board converter that is on-board the electric vehicle (e.g., as opposed to a wall-mounted or otherwise separate charging device). In some examples, a DC / DC converter (e.g., the DC / DC converter 1010) may be positioned between the four-leg power converter 304 and the battery 310 to boost or buck the DC charging power before reaching -74- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 the battery 310, as described with respect to FIG.10A-13. Additionally, in an inversion mode, the four-leg power converter 304 inverts DC power received from the electric vehicle battery (e.g., the battery 310) and outputs a generated AC signal via the AC connection nodes. The AC signal may be output to an AC utility grid (e.g., via the aforementioned plug), may drive an AC motor of the electric vehicle, and / or may provide power to a local microgrid powered by the electric vehicle.

[0227] FIGS. 24A and 24B illustrate in condensed diagrams six different configurations, also described previously in this disclosure, for a four-leg AC / DC converter. More particularly, FIG.24A illustrates a four-leg AC / DC power converter, which is illustrated as the four-leg power converter 1725, but may also be the four-leg power converter 304. FIG. 24A illustrates the four-leg power converter 1725 in three selectable symmetric operational modes including a symmetric three-phase, a symmetric split-phase, and a symmetric single- phase operational mode. FIG. 24B illustrates the four-leg power converter 1725 in three selectable asymmetric operational modes including an asymmetric three-phase, an asymmetric split-phase, and an asymmetric single-phase operational mode. At any one time, one of the six AC systems illustrated in FIGS.24A and 24B (balanced three-phase, split-phase, or single-phase or unbalanced three-phase, split-phase, single-phase) may be coupled to the four-leg power converter 1725 and one of the six operational modes may be selected and implemented by the four-leg power converter 1725. The symmetric operational modes are generally used for balanced AC systems, while the asymmetric operational modes are generally used for unbalanced AC systems. The symmetric and asymmetric operational modes for the single-phase AC system may include the same arrangement and control scheme, whereas the symmetric and asymmetric operational modes for three-phase and split-phase AC systems may vary, as previously described herein.

[0228] FIG.25 illustrates a functional block diagram 2500 for determining a reference phase θ of an AC signal of a power converter. The diagram 2500 illustrates an example of the PLL block 512 of FIG.5. The function blocks 2520 determine and output the reference phase angle reference (θ*), which may be provided as the determined phase angle (θ) (e.g., output by the PLL 512 in FIG.5). -75- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272

[0229] Turning to FIG. 26, a power converter system 2600 is illustrated. Like the power converter system 500 of FIG. 5, the power converter system 2600 may control the four-leg power converter 304 in the ^^^^^^^^ domain. The power converter system 2600 includes the four-leg power converter 304 and a control system 2605. With reference also to FIG.1, the power converter system 2600 is an example of the power converter system 100 and the control system 2605 is an example of the control system 105. In the diagram of FIG. 26, to simplify the control, the grid‐side filtering inductor and the grid inductance are merged together into one lumped component ^^^inserted on the grid side.

[0230] Generally, the power converter system 2600 is similar to the power converter system 500 except that the control system 2605 includes both current and voltage-based regulation. Accordingly, the description of the power converter system 500 generally applies to the power converter system 2600 unless otherwise described, and the power converter system 2600 may be implemented in the various systems and methods described herein in place of the power converter system 500. Accordingly, like numbers used in FIG.26 indicate like parts with respect to FIG.5, unless otherwise noted.

[0231] Like the control system 505, the control system 2605 senses electrical operational characteristics for the four-leg power converter 304, uses the modified Clarke- Park transformation described above to generate control reference targets (first in the dqδσ reference frame and then translated to the stationary reference frame (abcn)), and controls the four-leg power converter 304 based on the control reference targets. The control system 2605 includes a first transformation block 510 to translate received electrical characteristics from the stationary abcn reference frame to the dqδσ reference frame, a phase-locked‐loop (PLL) block 512 to generate a phase angle (theta, θ), a DC bus control block 514, a reactive power control block 516, control blocks 2618a-d (including grid current control blocks 2618a-c and grid voltage control block 2618d), a second transformation block 2620, error blocks 2624a-d, and a variable frequency critical soft switching (VFCSS) block 522. In some examples, the first transformation block 510 of FIG.26 may be simplified to generate fewer values, such as, for example, just Vg,q, or another subset of those illustrated in FIG.26.

[0232] FIG. 27 illustrates a subset 2700 of the control system 2605 including the second transformation block 2620, regulator blocks 2705a-d (one regulator 2705 for each -76- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 leg), and the VFCSS block 522. Generally, the subset 2700 is similar to the subset 600 of FIG. 6 except that the subset 2700 includes both current and voltage-based regulation. Accordingly, the description of the subset 600 generally applies to the subset 2700 unless otherwise described. Accordingly, like numbers used in FIG. 27 indicate like parts with respect to FIG.6, unless otherwise noted. Further, the second transformation block 2620 is similar to the delta-sigma translator 520a, except that the second transformation block 2620 receives current reference values for the dqδ axes of the dqδσ reference frame (Ig,d*, Ig,q*, Ig,δ*), rather than voltage reference values. However, like the delta-sigma translator 520a, the second transformation block 2620 translates input values from the dqδσ reference frame to the abcn reference frame using similar functions as described with respect to the delta- sigma translator 520a. Accordingly, the second transformation block 2620 may also be referred to as a delta-sigma translator.

[0233] The regulator 2705, VFCSS sub-block 522a, and switch driver 522b for each phase may be implemented on a respective one of local controllers 660a, 660b, 660c, 660n (also referred to as the local controllers 660a-n). The local controllers 660a-n may be an example of the local controllers 160 of FIG. 1. The second transformation block 2620 and remaining components of the control system 2605 illustrated in FIG. 26 (aside from the VFCSS block 522) may be implemented on a central controller, such as, for example, the central controller 150 of FIG.1. Each of the local controllers 660, 160 and central controller 150 may be implemented by separate hardware (e.g., a separate microprocessor, FPGA, etc.) or one or more of these controllers may be virtual controllers that share hardware (e.g., implemented on the same microprocessor, FPGA, etc.). In some examples, the switch drivers 522b are implemented as hardware components that are separate from the local controllers 660a, 660b, 660c, 660n.

[0234] Returning briefly to FIG.7, the process 700 for converting voltage using a four- leg converter with a delta-sigma-based control may also be carried out by the power converter system 100 implemented as the power converter system 2600 of FIG.26. For the power converter system 2600, the process 700 may be executed in a similar manner as described with respect to the power converter 500, except that the generation of the control reference target in block 710 varies in light of the modified control blocks in the control system 2605 of FIG.26 relative to the control system 505 of FIG.5. More particularly, with -77- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 reference to FIGS.7, 26, and 27, the control system 2605 (FIG.26) may execute block 710 (Fig.7) to generate a control reference target in a stationary reference frame for each of the four phase legs based on the at least one electrical operational characteristic and a rotational (dqδσ) reference frame. For example, the reference grid currents ^^^,ௗ*, ^^^,^*, and ^^^,ఋ* and the grid sigma voltage ^^^,ఙ* in FIG.26 (control reference targets in the (dqδσ) reference frame) may be generated in a similar manner as described with respect to FIG. 5. These control reference targets may be provided to the second transformation block 2620 to convert from the rotational (dqδσ) reference frame to the stationary (abcn) reference frame, producing the following control reference targets in the stationary reference frame: grid reference currents ^^^,^*, ^^^,^*, and ^^^,^* and the grid neutral voltage ^^^,^*. Moreover, the second use the phase angle (θ) by the PLL block 512 togenerate targets in the stationary frame. As discussed elsewhere herein, the PLL block 512 may use grid voltage in the q-axis of the rotational (dqδσ) reference frame (^^^,^) to generate the phase angle (θ), where the q-axis grid voltage (^^^,^) is output by the first transformation block 510 (translated from the measured grid voltage (^^^,^^^^)). At least in this way, the control system 2605 generates the control reference targets in the stationary reference frame based on at least one the electrical operational characteristic (^^^,^^^^) of the converter 304, and based on the rotational (dqδσ) reference frame. The control system 2605 generates the control reference targets in the stationary reference frame based on the rotational (dqδσ) reference frame also because of the translation by the second transformation block 2620.

[0235] Error blocks 2624a-d may receive the grid reference values Ig,a*,^Ig,b*,^Ig,c*, Vg,n*, respectively, and compare to corresponding actual values (Ig,a,^Ig,b,^Ig,c,^Vg,n), which are also provided to the transformation block 510, and generate an error signal (eg,a,^eg,b,^eg,c,^eg,n) to provide to the control blocks 2618a-d. The control blocks 2618a-d may then generate duty cycle values Da,^Db,^Dc,^Dn for a pulse-width modulated (PWM) signal (fsw,abcn) respectively. For example, each of the control blocks 2618a-d may be a regulator (e.g., implementing PID control, PI control, or the like) that generates voltage reference values, based on a received error signal to ultimately cause the control system 2605 to drive the power converter system 2600 such that the actual values (Ig,a,^Ig,b,^Ig,c,^Vg,n) track the reference values Ig,a*,^Ig,b*,^Ig,c*, -78- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 and^Vg,n*. In FIG.27, the error blocks 2624a-d and the control blocks 2618a-d are illustrated as a combined blocks in the form of the regulators 2705a-d. For example, the regulator 2705a (FIG.27) may include the error block 2624a and the control block 2618a (FIG.26).

[0236] The current reference values Ig,d*,^Ig,q*,^Ig,δ* and voltage reference value^Vg,σ* are control reference targets in the rotational dqδσ reference frame. The second transformation block 2620, the regulator blocks 2705a-d, and the VFCSS blocks may ultimately translate the reference values into duty cycle values Da,^Db,^Dc,^Dn for a pulse-width modulated (PWM) signal (fsw,abcn) to drive the power switching elements of each leg of the four-leg power converter 304. For example, the second transformation block 2620 translates input values from the dqδσ reference frame (Ig,d*,^Ig,q*,^Ig,δ*, Vg,σ* ) to the abcn reference frame using similar functions as described with respect to the delta-sigma translator 520a. The grid reference values Ig,a*,^Ig,b*,^Ig,c*, Vg,n* generated by the second transformation block 2620 are received the regulators 2705a-d, which also receive the actual values (Ig,a,^Ig,b,^Ig,c,^Vg,n) and, based thereon, generate the duty cycle values Da,^Db,^Dc,^Dnusing a regulation algorithm (e.g., using a PI, PID, or MPC control algorithm). Accordingly, in block 710, the control system 2605may generate the control reference targets Ig,a*,^ Ig,b*,^ Ig,c*,^ Vg,n* in the stationary abcnreference frame, based on the at least one electrical operational characteristics and on the dqδσ rotational reference frame. The VFCSS 522 may then generate PWM signals based on the duty cycle values Da,^Db,^Dc,^Dn received, for example, as previously described with respect to FIG.6. The generation of the duty cycles by the regulators 2705a-d and the PWM signals by the VFCSS 522 may be part of block 715 of the process 700 (FIG.7).

[0237] Accordingly, rather than controlling the voltage on each leg of the converter 304, as described with respect to FIGS. 5-6, the control system 2605 controls or regulates the voltage on the neutral leg (n) of the converter 304, and controls or regulates the current on the other legs a, b, c of the converter 304. Like in the examples of FIGS.5-6, in the power converter system 2600 of FIG. 26, the sigma (σ)‐loop control may be used to control the common-mode voltage by keeping the reference grid sigma voltage (^^^,ఙ*) at a fixed value(e.g., ^^^^ ോ 2) to minimize or reduce leakage current circulation. FIG. 26 illustrates twotechniques to generate the control reference target for the common-mode voltage, the reference grid sigma voltage (^^^,ఙ*). First, the reference grid sigma voltage (^^^,ఙ*) may be set-79- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272to ^^^^ ോ 2. Second, the reference grid sigma voltage (^^^,ఙ*) may be set to an output of acompensator 2640, which may receive an error value output by error block 2642 that is indicative of a difference between the grid sigma voltage (^^^,ఙ), output by the ϐirsttransformation block 510, and half of the DC bus voltage (^^^^ ോ 2).

[0238] In other examples, the control system 2605 is modified to include voltage regulation of additional legs such that two or three legs of the converter 304 are voltage- regulated, as opposed to one (as shown in FIG. 26) or four (as shown in FIG. 5). In such examples, for each such leg with voltage regulation, the voltage regulation may be performed similar to as shown and described with respect to FIG.5. In further examples, a different leg (other than the neutral leg (n) (e.g., phase leg a, b, and / or c) is voltage-regulated, while one or more other legs are current-regulated. For example, the control system 2605 may be modified to control the voltage on phase leg a and modulate relative to phase leg a. For example, the control system 2605 may regulate the voltage on a first phase leg (e.g., phase leg a) to obtain a desirable common mode voltage, while the other phase legs are current- regulated. Although neutral leg may be selected for this purpose (e.g., as shown in FIG.26) because it may be closest to ground, in split-phase, this may not be the case. In such examples of split phase, single phase, or in three-phase converters (without a neutral), one phase leg (e.g., phase leg a) may be regulated by the control system to control common mode voltage, while the other phase legs are current-regulated. Accordingly, the control reference targets generated by the control system 2605 and 505 may be all voltage reference targets (see, e.g., FIG.5), one voltage reference target and three current reference targets (see, e.g., FIG.26), or another combination of voltage and current reference targets (e.g., for other examples as explained in this paragraph).

[0239] Although the power converter systems 500 and 2600 of FIGs. 5 and 26, respectively, have been discussed primarily in terms of connection to a sinusoidal AC grid, in some examples, these converter can operate on grids or interconnects with non-sinusoidal waveforms. In such examples, the common mode voltage may still be controlled to reduce or limit leakage currents using the dqδσ reference frame and the principles described herein.

[0240] The various VFCSS blocks provided herein (e.g., VFCSS 522, 1235, and 2222) may implement variable frequency critical soft switching, as described. However, in some -80- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 example, one or more of these VFCSS blocks may implement another form of soft switching, e.g., static frequency (non-critical) soft switching, static frequency critical soft switching, variable frequency (non-critical) soft switching, and / or variable frequency critical soft switching. Similarly, a VFCSS block that implements variable frequency soft switching may refer to the control system implementing variable frequency (non-critical) soft switching and / or variable frequency critical soft switching.

[0241] Performing the various techniques and operations described herein may be facilitated by an electronic controller (e.g., a processor-based computing device), such as, for example, a central controller 150, local controller 160, control system 505, local controllers 660a-n, local controllers 1360a-b, control system 1205, or the like as described herein. Such an electronic controller may include a processor-based device such as a computing device, and so forth, that may include a central processor unit (CPU) or a processing core. In addition to the CPU or processing core, the system includes main memory, cache memory, and bus interface circuits. The electronic controller may include a memory storage device, such as a hard drive (solid state hard drive, or other types of hard drive), or flash drive associated with the computer system. The electronic controller may further include a keyboard, or keypad, or some other user input interface, and a monitor, e.g., an LCD (liquid crystal display) monitor, that may be placed where a user can access them.

[0242] The electronic controller is configured to facilitate, for example, the implementation of a power converter (e.g., by controlling the switching devices of, for example, a non-isolated power converter system). The storage device may thus include a computer program product that when executed on the electronic controller (which, as noted, may be a processor-based device) causes the processor-based device to perform operations to facilitate the implementation of procedures and operations described herein. The electronic controller may further include peripheral devices to enable input / output functionality. Such peripheral devices may include, for example, flash drive (e.g., a removable flash drive), or a network connection (e.g., implemented using a USB port and / or a wireless transceiver), for downloading related content to the connected system. Such peripheral devices may also be used for downloading software containing computer instructions to enable general operation of the respective system / device. Alternatively and / or additionally, in some embodiments, special purpose logic circuitry, e.g., an FPGA (field programmable gate -81- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 array), an ASIC (application-specific integrated circuit), a DSP processor, a graphics processing unit (GPU), application processing unit (APU), etc., may be used in the implementations of the electronic controller. Other modules that may be included with the electronic controller may include a user interface to provide or receive input and output data. The electronic controller may include an operating system.

[0243] Computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and may be implemented in a high-level procedural and / or object-oriented programming language, and / or in assembly / machine language. As used herein, the term “machine-readable medium” refers to any non-transitory computer program product, apparatus and / or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and / or data to a programmable processor, including a non- transitory machine-readable medium that receives machine instructions as a machine- readable signal.

[0244] In some embodiments, any suitable computer readable media can be used for storing instructions for performing the processes / operations / procedures described herein. For example, in some embodiments computer readable media can be transitory or non-transitory. For example, non-transitory computer readable media can include media such as magnetic media (such as hard disks, floppy disks, etc.), optical media (such as compact discs, digital video discs, Blu-ray discs, etc.), semiconductor media (such as flash memory, electrically programmable read only memory (EPROM), electrically erasable programmable read only Memory (EEPROM), etc.), register memory, a processor cache, or any suitable media that is not fleeting or not devoid of any semblance of permanence during transmission, and / or any suitable tangible media. As another example, transitory computer readable media can include signals on networks, in wires, conductors, optical fibers, circuits, any suitable media that is fleeting and devoid of any semblance of permanence during transmission, and / or any suitable intangible media. As used in the present application, “non- transitory computer-readable medium” comprises all computer-readable media but does not consist of a transitory, propagating signal.

[0245] Although particular embodiments have been disclosed herein in detail, this has been done by way of example for purposes of illustration only, and is not intended to be -82- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 limiting with respect to the scope of the appended claims, which follow. Features of the disclosed embodiments can be combined, rearranged, etc., within the scope of the invention to produce more embodiments. Some other aspects, advantages, and modifications are considered to be within the scope of the claims provided below. The claims presented are representative of at least some of the embodiments and features disclosed herein. Other unclaimed embodiments and features are also contemplated. EXAMPLES

[0246] Example 1: A method, apparatus, and / or non-transitory computer-readable medium storing processor-executable instructions for a power converter system comprising: a four-leg power converter with a direct current (DC) voltage section including a DC bus and an alternating current (AC) voltage section including AC connection nodes, the power converter including four phase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements; and a control system coupled to the four-leg power converter, the control system is configured to: determine at least one electrical operational characteristic for each of the four phase legs; generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, where the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and where the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the four phase legs in accordance with the control reference targets.

[0247] Example 2: The method, apparatus, and / or non-transitory computer readable medium of Example 1, wherein the control system is configured to control the four-leg converter in at least one operational mode selected from a group of operational modes including: a three-phase mode in which the four-leg power converter is controlled as a three- phase converter and in which the first, second, and third phase legs correspond to a -83- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 respective phase of the three-phase converter and in which the fourth phase leg corresponds to a neutral leg; a parallel single-phase mode in which the four-leg power converter is controlled as a single-phase converter where the first and second phase legs are coupled to a first node of the AC connection nodes and operated in parallel and where the third and fourth phase legs are coupled to a second node of the AC connection nodes and operated in parallel and 180 degrees phase-shifted relative to the first and second phase legs; or a single- phase mode in which the four-leg power converter is controlled as a single-phase converter where the first phase leg is coupled to a first node of the AC connection nodes, the second phase leg is idle, the third phase leg is coupled to a second node of the AC connection nodes and operated 180 degrees phase-shifted relative to the first phase leg, and the fourth phase leg is idle.

[0248] Example 3: The method, apparatus, and / or non-transitory computer readable medium of Example 1 or 2, wherein the control system is configured to control the four-leg power converter in at least two operational modes selected from a group of operational modes including: a symmetric three-phase mode, an asymmetric three-phase mode, a symmetric split-phase mode, an asymmetric split-phase mode, and a single-phase mode.

[0249] Example 4: The method, apparatus, and / or non-transitory computer readable medium of Example 1 to 3, wherein, to generate the control reference targets in the stationary reference frame based on the at least one electrical operational characteristics and the rotational reference frame, the control system is configured to: translate the at least one electrical characteristics into translated values in the rotational reference frame; determine, using the translated values, a rotational reference frame target for each of the rotational reference frame components including a direct axis (d‐axis) target, a quadrature axis (q‐axis) target, a delta axis (δ‐axis) target, and a sigma axis (σ‐axis) target; and translate the rotational reference frame targets into the stationary reference frame to generate the control reference targets in the stationary reference frame.

[0250] Example 5: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 4, wherein, to drive the power switching elements of the four phase legs in accordance with the control reference targets, the control system is configured to: determine a duty cycle for a switching control signal for each phase leg of the four phase legs based on the control reference targets; and drive the power switching -84- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 elements of the four phase legs in accordance with the respective duty cycles for each phase leg of the four phase legs.

[0251] Example 6: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 5, wherein,, to drive the power switching elements of the four phase legs in accordance with the control reference targets, the control system is further configured to: determine a respective switching frequency for the switching control signal for each phase leg of the four phase legs to achieve soft switching control, and thereby implement variable frequency soft switching.

[0252] Example 7: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 5, wherein the control system may include: a central controller configured to: determine the at least one electrical operational characteristic for each of the four phase legs, and generate the control reference targets in the stationary reference frame; and a local controller for each phase leg of the four phase legs, each local controller configured to: receive a control reference target of the control reference targets, determine the duty cycle for the phase leg corresponding to the local controller based on the control reference target, and drive the power switching elements of the phase leg corresponding to the local controller in accordance with the duty cycle for the phase leg corresponding to the local controller.

[0253] Example 8: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 7, wherein the four-leg power converter is further coupled to a DC / DC converter via the DC bus.

[0254] Example 9: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 8, wherein, the control system is further configured to: determine a voltage level of an electric vehicle battery, control a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, control the set of contactors to connect the electric vehicle battery to the DC / DC converter, and drive the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level.

[0255] Example 10: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 9, wherein the DC / DC converter is a full bridge -85- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 converter that includes a first half bridge including first power switching elements and a first LC filter and a second half bridge including second power switching elements and a second LC filter, and where the first LC filter is connected to a positive battery terminal node and the second LC filter is connected to a negative battery terminal node.

[0256] Example 11: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 10, wherein the control system is configured to: determine a first electrical characteristic at the positive battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target.

[0257] Example 12: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 11, wherein, to generate the first DC / DC control reference target and the second DC / DC control reference target based on the difference (Δ) the sum (Σ) of the first electrical characteristic and the second electrical characteristic, the control system is further configured to: determine the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; determine a difference reference target (Δ**) and a sum reference target (Σ**) based on the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; and translate the difference reference target (Δ**) and the sum reference target (Σ**) to the first DC / DC control reference target and the second DC / DC control reference target.

[0258] Example 13: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 14, wherein, to drive the first and second power switching elements in accordance with the first and second DC / DC control reference targets, the control system is configured to: determine a first duty cycle for a first switching control signal for the first power switching elements based on the first control reference target; determine a second duty cycle for a second switching control signal for the second power switching elements based on the second control reference target; drive the first power -86- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 switching elements in accordance with the first duty cycle; and drive the second power switching elements in accordance with the second duty cycle.

[0259] Example 14: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 13, wherein the control system is further configured to: determine a first switching frequency for the first switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching; and determine a second switching frequency for the second switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching.

[0260] Example 15: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 14, wherein the control system is further configured to: implement a first switching frequency for the first switching control signal to achieve soft switching control or critical soft switching control; and implement a second switching frequency for the second switching control signal to achieve soft switching control or critical soft switching control.

[0261] Example 16: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 15, wherein the control system may include: a central controller configured to: determine the first and second electrical operational characteristics, and generate the first DC / DC control reference target and the second DC / DC control reference target; a first local controller for the first half bridge, the first local controller configured to: receive the first DC / DC control reference target, determine the first duty cycle for the first switching control signal for the first power switching elements based on the first control reference target, and drive the first power switching elements in accordance with the first duty cycle; and a second local controller for the second half bridge, second first local controller configured to: receive the second DC / DC control reference target, determine the second duty cycle for the second switching control signal for the second power switching elements based on the second control reference target, and drive the second power switching elements in accordance with the second duty cycle.

[0262] Example 17: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 16, wherein the DC / DC converter is a half bridge converter including an LC filter. -87- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272

[0263] Example 18: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 17, wherein the power switching elements of each phase leg of the four phase legs includes a high-side switch and a low-side switch connected together at a midpoint node, and where the LC filter of each phase leg of the four phase legs includes an inductor coupled between the midpoint node of the phase leg and a filter node of the phase leg, an upper capacitor coupled between the filter node of the phase leg and a positive DC bus node of the DC bus, and a lower capacitor coupled between the filter node of the phase leg and a negative DC bus node of the DC bus.

[0264] Example 19: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 18, wherein the four-leg power converter is incorporated into an electric vehicle, and where the control system is further configured to drive the power switching elements of the four phase legs in accordance with the control reference targets to at least one selected from a group of: rectify an AC signal received via the AC connection nodes and output DC charging power via the DC bus to charge an electric vehicle battery; or invert DC power from the electric vehicle battery and output a generated AC signal via the AC connection nodes.

[0265] Example 20: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 19, wherein the control reference targets are: all voltage reference targets, or a combination of current reference targets and voltage reference targets.

[0266] Example 21: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 1 to 20, wherein, to generate the control reference targets in the stationary reference frame based on the at least one electrical operational characteristics and the rotational reference frame, the control system is configured to: determine a rotational reference frame target for each component of the rotational reference frame including a direct axis (d-axis) target, a quadrature axis (q-axis) target, a delta axis (δ- axis) target, and a sigma axis (σ-axis) target; and translate the rotational reference frame targets into the stationary reference frame to generate the control reference targets in the stationary reference frame, the control reference targets in the stationary reference frame including a phase a target, a phase b target, a phase c target, and a neutral leg target, wherein -88- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 the phase a target, the phase b target, and the phase c target are current targets and the neutral leg target is a voltage target.

[0267] Example 22: A method, apparatus, and / or non-transitory computer-readable medium storing processor-executable instructions for a power converter system may include: a direct current (DC) / DC converter with a DC voltage section including a DC bus and with a battery connection section including a positive battery terminal node and a negative battery terminal node, the DC / DC converter including: a first half bridge including first power switching elements and a first LC filter, where the first LC filter is connected to the positive battery terminal node, and a second half bridge including second power switching elements and a second LC filter, where the second LC filter is connected to the negative battery terminal node; and a control system coupled to the DC / DC converter, the control system is configured to: determine a first electrical characteristic at the positive battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target.

[0268] Example 23: The method, apparatus, and / or non-transitory computer readable medium of Example 22, wherein, to generate the first DC / DC control reference target and the second DC / DC control reference target based on the difference (Δ) the sum (Σ) of the first electrical characteristic and the second electrical characteristic, the control system is further configured to: determine the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; determine a difference reference target (Δ**) and a sum reference target (Σ**) based on the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; and translate the difference reference target (Δ**) and the sum reference target (Σ**) to the first DC / DC control reference target and the second DC / DC control reference target.

[0269] Example 24: The method, apparatus, and / or non-transitory computer readable medium of Example 22 or 23, wherein, to drive the first and second power -89- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 switching elements in accordance with the first and second DC / DC control reference targets, the control system is configured to: determine a first duty cycle for a first switching control signal for the first power switching elements based on the first control reference target; determine a second duty cycle for a second switching control signal for the second power switching elements based on the second control reference target; drive the first power switching elements in accordance with the first duty cycle; and drive the second power switching elements in accordance with the second duty cycle.

[0270] Example 25: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 22 to 24, wherein the control system is further configured to: determine a first switching frequency for the first switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching; and determine a second switching frequency for the second switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching.

[0271] Example 26: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 22 to 25, wherein the control system is further configured to: implement a first switching frequency for the first switching control signal to achieve soft switching control or critical soft switching control; and implement a second switching frequency for the second switching control signal to achieve soft switching control or critical soft switching control.

[0272] Example 27: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 22 to 26, wherein the control system may include: a central controller configured to: determine the first and second electrical operational characteristics, and generate the first DC / DC control reference target and the second DC / DC control reference target; a first local controller for the first half bridge, the first local controller configured to: receive the first DC / DC control reference target, determine the first duty cycle for the first switching control signal for the first power switching elements based on the first control reference target, and drive the first power switching elements in accordance with the first duty cycle; and a second local controller for the second half bridge, second first local controller configured to: receive the second DC / DC control reference target, determine the second duty cycle for the second switching control signal for the second -90- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 power switching elements based on the second control reference target, and drive the second power switching elements in accordance with the second duty cycle.

[0273] Example 28: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 22 to 27, wherein the DC / DC converter is further coupled to an alternating current (AC) / DC power converter via the DC bus.

[0274] Example 29: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 22 to 28, wherein the control system is further configured to: determine a voltage level of an electric vehicle battery coupled to the positive battery terminal and the negative battery terminal, control a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, control the set of contactors to connect the electric vehicle battery to the DC / DC converter, and drive the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level by the driving of the first power switching elements in accordance with the first DC / DC control reference target and the driving of the second power switching elements in accordance with the second DC / DC control reference target.

[0275] Example 30: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 22 to 29, wherein the AC / DC power converter is a four- leg power converter with a direct current (DC) voltage section connected to the DC bus and an alternating current (AC) voltage section including AC connection nodes, the power converter including four phase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements; and the control system is coupled to the four-leg power converter and is further configured to: determine at least one electrical operational characteristic for each of the four phase legs; generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, where the -91- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and where the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the four phase legs in accordance with the control reference targets.

[0276] Example 31: A method, apparatus, and / or non-transitory computer-readable medium storing processor-executable instructions for a reconfigurable power converter system may include: an alternative current (AC) / direct current (DC) power converter including a DC bus and AC connection nodes, the AC / DC power converter having phase legs including a first phase leg, a second phase leg, and a third phase leg, each of the first, second, and third phase legs having a respective LC filter, respective power switching elements, and a respective AC connection node of the AC connection nodes; a DC / DC power converter with DC nodes coupled to the DC bus and with a battery connection section including a positive battery terminal node and a negative battery terminal node, the DC / DC power converter including a first half bridge including first power switching elements and a first LC filter, where the first LC filter is connected to the positive battery terminal node; and a control system coupled to the AC / DC power converter and the DC / DC power converter, the control system configured to: determine an operational mode for the AC / DC power converter to be a three-phase mode having three AC phases, control the AC / DC power converter in the three- phase mode in which the first, second, and third phase legs each correspond to a respective phase of the three AC phases and the AC connection node of the first phase leg is connected to a first node of a three-phase AC system, the AC connection node of the second phase leg is connected to a second node of the three-phase AC system, and the AC connection node of the third phase leg is connected to a third node of the three-phase AC system, determine the operational mode for the AC / DC power converter to be a single-phase mode having a single AC phase, and control the AC / DC power converter in the single-phase mode in which the first and second phase legs each correspond to the single AC phase and the AC connection nodes of the first and second phase legs are connected to a first node of a single-phase AC system.

[0277] Example 32: The method, apparatus, and / or non-transitory computer readable medium of Example 31, wherein the three-phase mode is an asymmetric three- phase mode, wherein phase legs of the AC / DC power converter further include a fourth -92- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 phase leg having a fourth LC filter, fourth power switching elements, and a fourth AC connection node, where, in the asymmetric three-phase mode, the fourth phase leg corresponds to a neutral leg and the fourth AC connection node is connected to a neutral node of the three-phase AC system, and where, in the single-phase mode, the third and fourth phase legs are connected to a second node of the single-phase AC system, and are operated in parallel and 180 degrees phase-shifted relative to the first and second phase legs.

[0278] Example 33: The method, apparatus, and / or non-transitory computer readable medium of Example 31 or 32, wherein the control system is further configured to: determine the operational mode for the AC / DC power converter to be a symmetric three- phase mode having three AC phases that are separated by 120 degrees, and control the AC / DC power converter in the symmetric three-phase mode in which: the first, second, and third phase legs each correspond to a respective phase of the three AC phases and the AC connection node of the first phase leg is connected to the first node of a three-phase AC system, the AC connection node of the second phase leg is connected to the second node of the three-phase AC system, and the AC connection node of the third phase leg is connected to the third node of the three-phase AC system, and operation of the fourth phase leg is disabled.

[0279] Example 34: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 31 to 33, wherein the control system is further configured to: determine the operational mode for the AC / DC power converter to be a symmetric split-phase mode having two AC phases that are separated by 180 degrees, and control the AC / DC power converter in the symmetric split-phase mode in which: the first and second phase legs corresponds to a first AC phase of the two AC phases and the AC connection nodes of the first phase leg and of the second phase leg are connected to a first node of a split-phase AC system, and the third and fourth phase legs corresponds to a second AC phase of the two AC phases and the AC connection nodes of the third phase leg and of the fourth phase leg are connected to a second node of the split-phase AC system.

[0280] Example 35: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 31 to 34, wherein the control system is further configured to: determine the operational mode for the AC / DC power converter to be a asymmetric split-phase mode having two AC phases that are separated by 180 degrees, and -93- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 control the AC / DC power converter in the asymmetric split-phase mode in which: the first phase leg corresponds to a first AC phase of the two AC phases and the AC connection node of the first phase leg is connected to a first node of a split-phase AC system, the second phase leg corresponds to a second AC phase of the two AC phases and the AC connection node of the second phase leg is connected to a second node of the split-phase AC system, and the fourth phase leg corresponds to a neutral leg and the fourth AC connection node is connected to a neutral node of the split-phase AC system.

[0281] Example 36: The method, apparatus, and / or non-transitory computer readable medium of Example 31 or 35, wherein the control system is configured to: determine at least one electrical operational characteristic for each of the phase legs; generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐ axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, where the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and where the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the phase legs in accordance with the control reference targets.

[0282] Example 37: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 31 to 36, wherein the DC / DC power converter further includes a second half bridge including second power switching elements and a second LC filter, where the second LC filter is connected to the negative battery terminal node.

[0283] Example 38: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 31 to 37, wherein the control system is configured to: determine a first electrical characteristic at the positive battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive -94- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target.

[0284] Example 39: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 31 to 38, wherein the control system is further configured to: determine the operational mode for the AC / DC power converter to be a reduced single-phase mode having the single AC phase, and control the AC / DC power converter in the reduced single-phase mode in which the first phase leg is connected to the first node of the single-phase AC system, the second phase leg is idle, the third phase leg is connected to the second node of the single-phase AC system, and the fourth phase leg is idle.

[0285] Example 40: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 31 to 39, wherein the control system is further configured to: determine a voltage level of an electric vehicle battery coupled to the positive battery terminal and the negative battery terminal, control a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, control the set of contactors to connect the electric vehicle battery to the DC / DC converter, and drive the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level.

[0286] Example 41: The method, apparatus, and / or non-transitory computer readable medium of any of Examples 31 to 40, wherein the AC / DC power converter further includes a split phase capacitor block coupled to the DC bus and including an upper capacitor, a lower capacitor, a midpoint node coupled between the upper capacitor and lower capacitor, where, in the three-phase mode, the midpoint node is connected to a neutral node of the three-phase AC system, and where, in the single-phase mode, the three phase legs correspond to the single AC phase and the AC connection nodes of the three phase legs are connected to the first node of the single-phase AC system, and the midpoint node is coupled to a second node of the single-phase AC system and is 180 degrees phase-shifted relative to the first, second, and third phase legs.

[0287] Example 42: method, apparatus, and / or non-transitory computer readable medium of any of Examples 31 to 41, wherein the control system is further configured to: -95- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 determine the operational mode for the AC / DC power converter to be a symmetric three- phase mode; control the AC / DC power converter in the symmetric three-phase mode; determine the operational mode for the AC / DC power converter to be a symmetric split- phase mode; control the AC / DC power converter in the symmetric split-phase mode; determine the operational mode for the AC / DC power converter to be a asymmetric split- phase mode; and control the AC / DC power converter in the asymmetric split-phase mode. -96- Q   B\175073.00272\95982016.5

Claims

Attorney Docket No.: 175073.00272 WHAT IS CLAIMED IS:

1. A power converter system comprising: a four-leg power converter with a direct current (DC) voltage section including a DC bus and an^alternating current (AC) voltage section including AC connection nodes, the four- leg power converter including four phase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements; and a control system coupled to the four-leg power converter, the control system is configured to: determine at least one electrical operational characteristic for each of the four phase legs; generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, wherein the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and wherein the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the four phase legs in accordance with the control reference targets.

2. The power converter system of claim 1, wherein the control system is configured to control the four-leg power converter in at least one operational mode selected from a group of operational modes including: a three-phase mode in which the four-leg power converter is controlled as a three- phase converter and in which the first, second, and third phase legs correspond to a respective phase of the three-phase converter and in which the fourth phase leg corresponds to a neutral leg; -97- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 a parallel single-phase mode in which the four-leg power converter is controlled as a single-phase converter wherein the first and second phase legs are coupled to a first node of the AC connection nodes and operated in parallel and wherein the third and fourth phase legs are coupled to a second node of the AC connection nodes and operated in parallel and 180 degrees phase-shifted relative to the first and second phase legs; or a single-phase mode in which the four-leg power converter is controlled as a single- phase converter wherein the first phase leg is coupled to a first node of the AC connection nodes, the second phase leg is idle, the third phase leg is coupled to a second node of the AC connection nodes and operated 180 degrees phase-shifted relative to the first phase leg, and the fourth phase leg is idle.

3. The power converter system of claim 1, wherein the control system is configured to control the four-leg power converter in at least two operational modes selected from a group of operational modes including: a symmetric three-phase mode, an asymmetric three-phase mode, a symmetric split-phase mode, an asymmetric split-phase mode, and a single-phase mode.

4. The power converter system of claim 1, wherein, to generate the control reference targets in the stationary reference frame based on the at least one electrical operational characteristics and the rotational reference frame, the control system is configured to: translate the at least one electrical characteristics into translated values in the rotational reference frame; determine, using the translated values, a rotational reference frame target for each component of the rotational reference frame including a direct axis (d‐axis) target, a quadrature axis (q‐axis) target, a delta axis (δ‐axis) target, and a sigma axis (σ‐axis) target; and translate the rotational reference frame targets into the stationary reference frame to generate the control reference targets in the stationary reference frame. -98- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 5. The power converter system of claim 1, wherein, to drive the power switching elements of the four phase legs in accordance with the control reference targets, the control system is configured to: determine a duty cycle for a switching control signal for each phase leg of the four phase legs based on the control reference targets; and drive the power switching elements of the four phase legs in accordance with the respective duty cycles for each phase leg of the four phase legs.

6. The power converter system of claim 5, wherein, to drive the power switching elements of the four phase legs in accordance with the control reference targets, the control system is further configured to: determine a respective switching frequency for the switching control signal for each phase leg of the four phase legs to achieve soft switching control, and thereby implement variable frequency soft switching.

7. The power converter system of claim 5, wherein the control system comprises: a central controller configured to: determine the at least one electrical operational characteristic for each of the four phase legs, and generate the control reference targets in the stationary reference frame; and a local controller for each phase leg of the four phase legs, each local controller configured to: receive a control reference target of the control reference targets, determine the duty cycle for the phase leg corresponding to the local controller based on the control reference target, and drive the power switching elements of the phase leg corresponding to the local controller in accordance with the duty cycle for the phase leg corresponding to the local controller.

8. The power converter system of claim 1, wherein the four-leg power converter is further coupled to a DC / DC converter via the DC bus. -99- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 9. The power converter system of claim 8, wherein the control system is further configured to: determine a voltage level of an electric vehicle battery, control a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, control the set of contactors to connect the electric vehicle battery to the DC / DC converter, and drive the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level.

10. The power converter system of claim 8, wherein the DC / DC converter is a full bridge converter that includes a first half bridge including first power switching elements and a first LC filter and a second half bridge including second power switching elements and a second LC filter, and wherein the first LC filter is connected to a positive battery terminal node and the second LC filter is connected to a negative battery terminal node.

11. The power converter system of claim 10, wherein the control system is configured to: determine a first electrical characteristic at the positive battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target. -100- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 12. The power converter system of claim 11, wherein, to generate the first DC / DC control reference target and the second DC / DC control reference target based on the difference (Δ) the sum (Σ) of the first electrical characteristic and the second electrical characteristic, the control system is further configured to: determine the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; determine a difference reference target (Δ**) and a sum reference target (Σ**) based on the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; and translate the difference reference target (Δ**) and the sum reference target (Σ**) to the first DC / DC control reference target and the second DC / DC control reference target.

13. The power converter system of claim 11, wherein, to drive the first and second power switching elements in accordance with the first and second DC / DC control reference targets, the control system is configured to: determine a first duty cycle for a first switching control signal for the first power switching elements based on the first DC / DC control reference target; determine a second duty cycle for a second switching control signal for the second power switching elements based on the second DC / DC control reference target; drive the first power switching elements in accordance with the first duty cycle; and drive the second power switching elements in accordance with the second duty cycle.

14. The power converter system of claim 13, wherein the control system is further configured to: determine a first switching frequency for the first switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching; and determine a second switching frequency for the second switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching. -101- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 15. The power converter system of claim 13, wherein the control system is further configured to: implement a first switching frequency for the first switching control signal to achieve soft switching control or critical soft switching control; and implement a second switching frequency for the second switching control signal to achieve soft switching control or critical soft switching control.

16. The power converter system of claim 13, wherein the control system comprises: a central controller configured to: determine the first and second electrical characteristics, and generate the first DC / DC control reference target and the second DC / DC control reference target; a first local controller for the first half bridge, the first local controller configured to: receive the first DC / DC control reference target, determine the first duty cycle for the first switching control signal for the first power switching elements based on the first DC / DC control reference target, and drive the first power switching elements in accordance with the first duty cycle; and a second local controller for the second half bridge, second first local controller configured to: receive the second DC / DC control reference target, determine the second duty cycle for the second switching control signal for the second power switching elements based on the second DC / DC control reference target, and drive the second power switching elements in accordance with the second duty cycle.

17. The power converter system of claim 10, wherein the DC / DC converter is a half bridge converter including an LC filter.

18. The power converter system of claim 1, -102- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 wherein the power switching elements of each phase leg of the four phase legs includes a high-side switch and a low-side switch connected together at a midpoint node, and wherein the LC filter of each phase leg of the four phase legs includes an inductor coupled between the midpoint node of the phase leg and a filter node of the phase leg, an upper capacitor coupled between the filter node of the phase leg and a positive DC bus node of the DC bus, and a lower capacitor coupled between the filter node of the phase leg and a negative DC bus node of the DC bus.

19. The power converter system of claim 1, wherein the four-leg power converter is incorporated into an electric vehicle, and wherein the control system is further configured to drive the power switching elements of the four phase legs in accordance with the control reference targets to at least one selected from a group of: rectify an AC signal received via the AC connection nodes and output DC charging power via the DC bus to charge an electric vehicle battery; or invert DC power from the electric vehicle battery and output a generated AC signal via the AC connection nodes.

20. The power converter system of claim 1, wherein the control reference targets are: all voltage reference targets, or a combination of current reference targets and voltage reference targets.

21. The power converter system of claim 1, wherein, to generate the control reference targets in the stationary reference frame based on the at least one electrical operational characteristics and the rotational reference frame, the control system is configured to: determine a rotational reference frame target for each component of the rotational reference frame including a direct axis (d‐axis) target, a quadrature axis (q‐axis) target, a delta axis (δ‐axis) target, and a sigma axis (σ‐axis) target; and translate the rotational reference frame targets into the stationary reference frame to generate the control reference targets in the stationary reference frame, the control reference targets in the stationary reference frame including a phase a target, a phase b -103- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 target, a phase c target, and a neutral leg target, wherein the phase a target, the phase b target, and the phase c^target are current targets and the neutral leg target is a voltage target.

22. A method of converting voltage, the method comprising: determining, by a control system, at least one electrical operational characteristic for each of four phase legs of a four-leg power converter having a direct current (DC) voltagesection including a DC bus and an^ alternating current (AC) voltage section including ACconnection nodes, the four phase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements; generating, by the control system, control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, wherein the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and wherein the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and driving, by the control system, the power switching elements of the four phase legs in accordance with the control reference targets.

23. The method of claim 22, further comprising controlling, by the control system, the four- leg power converter in at least one operational mode selected from a group of operational modes including: a three-phase mode in which the four-leg power converter is controlled as a three- phase converter and in which the first, second, and third phase legs correspond to a respective phase of the three-phase converter and in which the fourth phase leg corresponds to a neutral leg; a parallel single-phase mode in which the four-leg power converter is controlled as a single-phase converter wherein the first and second phase legs are coupled to a first node of -104- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 the AC connection nodes and operated in parallel and wherein the third and fourth phase legs are coupled to a second node of the AC connection nodes and operated in parallel and 180 degrees phase-shifted relative to the first and second phase legs; or a single-phase mode in which the four-leg power converter is controlled as a single- phase converter wherein the first phase leg is coupled to a first node of the AC connection nodes, the second phase leg is idle, the third phase leg is coupled to a second node of the AC connection nodes and operated 180 degrees phase-shifted relative to the first phase leg, and the fourth phase leg is idle.

24. The method of claim 22, further comprising controlling, by the control system the four- leg power converter in at least two operational modes selected from a group of operational modes including: a symmetric three-phase mode, an asymmetric three-phase mode, a symmetric split-phase mode, an asymmetric split-phase mode, and a single-phase mode.

25. The method of claim 22, wherein generating the control reference targets in the stationary reference frame based on the at least one electrical operational characteristic and the rotational reference frame comprises: translating the at least one electrical characteristic into translated values in the rotational reference frame; determining, using the translated values, a rotational reference frame target for each component of the rotational reference frame including a direct axis (d‐axis) target, a quadrature axis (q‐axis) target, a delta axis (δ‐axis) target, and a sigma axis (σ‐axis) target; and translating the rotational reference frame targets into the stationary reference frame to generate the control reference targets in the stationary reference frame.

26. The method of claim 22, wherein driving the power switching elements of the four phase legs in accordance with the control reference targets comprises: determining a duty cycle for a switching control signal for each phase leg of the four phase legs based on the control reference targets; -105- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 driving the power switching elements of the four phase legs in accordance with the respective duty cycles for each phase leg of the four phase legs; and determining a respective switching frequency for the switching control signal for each phase leg of the four phase legs to achieve soft switching control, and thereby implement variable frequency soft switching.

27. The method of claim 22, wherein the four-leg power converter is further coupled to a DC / DC converter via the DC bus and the method further comprises: determining a voltage level of an electric vehicle battery, controlling a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, controlling the set of contactors to connect the electric vehicle battery to the DC / DC converter, and driving the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level.

28. The method of claim 22, wherein the four-leg power converter is further coupled to a DC / DC converter via the DC bus, wherein the DC / DC converter is a full bridge converter that includes a first half bridge including first power switching elements and a first LC filter and a second half bridge including second power switching elements and a second LC filter, and wherein the first LC filter is connected to a positive battery terminal node and the second LC filter is connected to a negative battery terminal node.

29. The method of claim 28, the method further comprising: determining a first electrical characteristic at the positive battery terminal node; determining a second electrical characteristic at the negative battery terminal node; generating a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the -106- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; driving the first power switching elements in accordance with the first DC / DC control reference target; and driving the second power switching elements in accordance with the second DC / DC control reference target.

30. The method of claim 22, wherein the four-leg power converter is incorporated into an electric vehicle, and the method further comprises: driving the power switching elements of the four phase legs in accordance with the control reference targets to at least one selected from a group of: rectify an AC signal received via the AC connection nodes and output DC charging power via the DC bus to charge an electric vehicle battery; or invert DC power from the electric vehicle battery and output a generated AC signal via the AC connection nodes.

31. The method of claim 22, wherein the control reference targets are: all voltage reference targets, or a combination of current reference targets and voltage reference targets.

32. The method of claim 22, wherein generating the control reference targets in the stationary reference frame based on the at least one electrical operational characteristics and the rotational reference frame includes: determining a rotational reference frame target for each component of the rotational reference frame including a direct axis (d‐axis) target, a quadrature axis (q‐axis) target, a delta axis (δ‐axis) target, and a sigma axis (σ‐axis) target; and translating the rotational reference frame targets into the stationary reference frame to generate the control reference targets in the stationary reference frame, the control reference targets in the stationary reference frame including a phase a target, a phase b target, a phase c target, and a neutral leg target, wherein the phase a target, the phase b target, and the phase c^target are current targets and the neutral leg target is a voltage target. -107- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 33. A non-transitory computer readable medium comprising instructions stored thereon that, when executed by a computer, control the computer to: determine at least one electrical operational characteristic for each of four phase legs of a four-leg power converter having a direct current (DC) voltage section including a DC busand an^ alternating current (AC) voltage section including AC connection nodes, the fourphase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements; generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, wherein the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and wherein the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the four phase legs in accordance with the control reference targets.

34. The computer readable medium of claim 33, where the instructions, when executed by a computer, further control the computer to: control the four-leg power converter in at least one operational mode selected from a group of operational modes including: a three-phase mode in which the four-leg power converter is controlled as a three- phase converter and in which the first, second, and third phase legs correspond to a respective phase of the three-phase converter and in which the fourth phase leg corresponds to a neutral leg; a parallel single-phase mode in which the four-leg power converter is controlled as a single-phase converter wherein the first and second phase legs are coupled to a first node of -108- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 the AC connection nodes and operated in parallel and wherein the third and fourth phase legs are coupled to a second node of the AC connection nodes and operated in parallel and 180 degrees phase-shifted relative to the first and second phase legs; or a single-phase mode in which the four-leg power converter is controlled as a single- phase converter wherein the first phase leg is coupled to a first node of the AC connection nodes, the second phase leg is idle, the third phase leg is coupled to a second node of the AC connection nodes and operated 180 degrees phase-shifted relative to the first phase leg, and the fourth phase leg is idle.

35. The computer readable medium of claim 33, wherein, to generate the control reference targets in the stationary reference frame based on the at least one electrical operational characteristic and the rotational reference frame, the instructions further control the computer to: translate the at least one electrical characteristic into translated values in the rotational reference frame; determine, using the translated values, a rotational reference frame target for each component of the rotational reference frame including a direct axis (d‐axis) target, a quadrature axis (q‐axis) target, a delta axis (δ‐axis) target, and a sigma axis (σ‐axis) target; and translate the rotational reference frame targets into the stationary reference frame to generate the control reference targets in the stationary reference frame.

36. The computer readable medium of claim 33, wherein, to drive the power switching elements of the four phase legs in accordance with the control reference targets, the instructions further control the computer to: determine a duty cycle for a switching control signal for each phase leg of the four phase legs based on the control reference targets; drive the power switching elements of the four phase legs in accordance with the respective duty cycles for each phase leg of the four phase legs; and -109- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 determine a respective switching frequency for the switching control signal for each phase leg of the four phase legs to achieve soft switching control, and thereby implement variable frequency soft switching.

37. The computer readable medium of claim 33, wherein the four-leg power converter is further coupled to a DC / DC converter via the DC bus and the instructions, when executed by a computer, further control the computer to: determine a voltage level of an electric vehicle battery, control a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, control the set of contactors to connect the electric vehicle battery to the DC / DC converter, and drive the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level.

38. The computer readable medium of claim 33, wherein the four-leg power converter is further coupled to a DC / DC converter via the DC bus, wherein the DC / DC converter is a full bridge converter that includes a first half bridge including first power switching elements and a first LC filter and a second half bridge including second power switching elements and a second LC filter, and wherein the first LC filter is connected to a positive battery terminal node and the second LC filter is connected to a negative battery terminal node.

39. The computer readable medium of claim 38, where the instructions, when executed by a computer, further control the computer to: determine a first electrical characteristic at the positive battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second -110- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target.

40. The computer readable medium of claim 33, wherein the four-leg power converter is incorporated into an electric vehicle, and the instructions, when executed by a computer, further control the computer to: drive the power switching elements of the four phase legs in accordance with the control reference targets to at least one selected from a group of: rectify an AC signal received via the AC connection nodes and output DC charging power via the DC bus to charge an electric vehicle battery; or invert DC power from the electric vehicle battery and output a generated AC signal via the AC connection nodes.

41. The computer readable medium of claim 33, wherein the control reference targets are: all voltage reference targets, or a combination of current reference targets and voltage reference targets.

42. The computer readable medium of claim 33, wherein, to generate the control reference targets in the stationary reference frame based on the at least one electrical operational characteristics and the rotational reference frame, the instructions, when executed by a computer, further: determine a rotational reference frame target for each component of the rotational reference frame including a direct axis (d‐axis) target, a quadrature axis (q‐axis) target, a delta axis (δ‐axis) target, and a sigma axis (σ‐axis) target; and translate the rotational reference frame targets into the stationary reference frame to generate the control reference targets in the stationary reference frame, the control reference targets in the stationary reference frame including a phase a target, a phase b -111- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 target, a phase c target, and a neutral leg target, wherein the phase a target, the phase b target, and the phase c^target are current targets and the neutral leg target is a voltage target.

43. A power converter system comprising: a direct current (DC) / DC converter with a DC voltage section including a DC bus and with a battery connection section including a positive battery terminal node and a negative battery terminal node, the DC / DC converter including: a first half bridge including first power switching elements and a first LC filter, wherein the first LC filter is connected to the positive battery terminal node, and a second half bridge including second power switching elements and a second LC filter, wherein the second LC filter is connected to the negative battery terminal node; and a control system coupled to the DC / DC converter, the control system is configured to: determine a first electrical characteristic at the positive battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target.

44. The power converter system of claim 43, wherein, to generate the first DC / DC control reference target and the second DC / DC control reference target based on the difference (Δ) the sum (Σ) of the first electrical characteristic and the second electrical characteristic, the control system is further configured to: -112- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 determine the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; determine a difference reference target (Δ**) and a sum reference target (Σ**) based on the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; and translate the difference reference target (Δ**) and the sum reference target (Σ**) to the first DC / DC control reference target and the second DC / DC control reference target.

45. The power converter system of claim 43, wherein, to drive the first and second power switching elements in accordance with the first and second DC / DC control reference targets, the control system is configured to: determine a first duty cycle for a first switching control signal for the first power switching elements based on the first DC / DC control reference target; determine a second duty cycle for a second switching control signal for the second power switching elements based on the second DC / DC control reference target; drive the first power switching elements in accordance with the first duty cycle; and drive the second power switching elements in accordance with the second duty cycle.

46. The power converter system of claim 45, wherein the control system is further configured to: determine a first switching frequency for the first switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching; and determine a second switching frequency for the second switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching.

47. The power converter system of claim 45, wherein the control system is further configured to: implement a first switching frequency for the first switching control signal to achieve soft switching control or critical soft switching control; and -113- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 implement a second switching frequency for the second switching control signal to achieve soft switching control or critical soft switching control.

48. The power converter system of claim 45, wherein the control system comprises: a central controller configured to: determine the first and second electrical characteristics, and generate the first DC / DC control reference target and the second DC / DC control reference target; a first local controller for the first half bridge, the first local controller configured to: receive the first DC / DC control reference target, determine the first duty cycle for the first switching control signal for the first power switching elements based on the first DC / DC control reference target, and drive the first power switching elements in accordance with the first duty cycle; and a second local controller for the second half bridge, second first local controller configured to: receive the second DC / DC control reference target, determine the second duty cycle for the second switching control signal for the second power switching elements based on the second DC / DC control reference target, and drive the second power switching elements in accordance with the second duty cycle.

49. The power converter system of claim 43, wherein the DC / DC converter is further coupled to an alternating current (AC) / DC power converter via the DC bus.

50. The power converter system of claim 49, wherein the control system is further configured to: determine a voltage level of an electric vehicle battery coupled to the positive battery terminal node and the negative battery terminal node, -114- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 control a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, control the set of contactors to connect the electric vehicle battery to the DC / DC converter, and drive the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level by the driving of the first power switching elements in accordance with the first DC / DC control reference target and the driving of the second power switching elements in accordance with the second DC / DC control reference target.

51. The power converter system of claim 49, wherein the AC / DC power converter is a four-leg power converter with a direct current (DC) voltage section connected to the DC bus and an^alternating current (AC) voltage section including AC connection nodes, the four-leg power converter including four phase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements; and the control system is coupled to the four-leg power converter and is further configured to: determine at least one electrical operational characteristic for each of the four phase legs; generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, wherein the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and wherein the sigma axis component -115- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the four phase legs in accordance with the control reference targets.

52. A method of converting voltage, the method comprising: determining, by a control system coupled to a direct current (DC) / DC converter, a first electrical characteristic at a positive battery terminal node of the DC / DC converter, wherein the DC / DC converter includes: a DC voltage section including a DC bus and with a battery connection section including the positive battery terminal node and a negative battery terminal node, a first half bridge including first power switching elements and a first LC filter, wherein the first LC filter is connected to the positive battery terminal node, and a second half bridge including second power switching elements and a second LC filter, wherein the second LC filter is connected to the negative battery terminal node; determining a second electrical characteristic at the negative battery terminal node; generating a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; driving the first power switching elements in accordance with the first DC / DC control reference target; and driving the second power switching elements in accordance with the second DC / DC control reference target.

53. The method of claim 52, wherein generating the first DC / DC control reference target and the second DC / DC control reference target based on the difference (Δ) the sum (Σ) of the first electrical characteristic and the second electrical characteristic comprises: determining the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; -116- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 determining a difference reference target (Δ**) and a sum reference target (Σ**) based on the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; and translating the difference reference target (Δ**) and the sum reference target (Σ**) to the first DC / DC control reference target and the second DC / DC control reference target.

54. The method of claim 52, wherein driving the first and second power switching elements in accordance with the first and second DC / DC control reference targets comprises: determining a first duty cycle for a first switching control signal for the first power switching elements based on the first DC / DC control reference target; determining a second duty cycle for a second switching control signal for the second power switching elements based on the second DC / DC control reference target; driving the first power switching elements in accordance with the first duty cycle; and driving the second power switching elements in accordance with the second duty cycle.

55. The method of claim 54, further comprising: determining a first switching frequency for the first switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching; and determining a second switching frequency for the second switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching.

56. The method of claim 54, further comprising: implementing a first switching frequency for the first switching control signal to achieve soft switching control or critical soft switching control; and implementing a second switching frequency for the second switching control signal to achieve soft switching control or critical soft switching control.

57. The method of claim 54, further comprising: -117- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 determining, by a central controller of the control system, the first and second electrical characteristics; generating, by the central controller, the first DC / DC control reference target and the second DC / DC control reference target; receiving, by a first local controller for the first half bridge, the first DC / DC control reference target; determining, by the first local controller, the first duty cycle for the first switching control signal for the first power switching elements based on the first DC / DC control reference target; driving, by the first local controller, the first power switching elements in accordance with the first duty cycle; receiving, by a second local controller for the second half bridge, the second DC / DC control reference target; determining, by the second local controller, the second duty cycle for the second switching control signal for the second power switching elements based on the second DC / DC control reference target; and driving, by the second local controller, the second power switching elements in accordance with the second duty cycle.

58. The method of claim 52, wherein the DC / DC converter is further coupled to an alternating current (AC) / DC power converter via the DC bus.

59. The method of claim 58, further comprising: determining a voltage level of an electric vehicle battery coupled to the positive battery terminal node and the negative battery terminal node, controlling a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, controlling the set of contactors to connect the electric vehicle battery to the DC / DC converter, and -118- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 driving the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level by the driving of the first power switching elements in accordance with the first DC / DC control reference target and the driving of the second power switching elements in accordance with the second DC / DC control reference target.

60. The method of claim 58, wherein the AC / DC power converter is a four-leg power converter with a direct current (DC) voltage section connected to the DC bus and an^ alternating current (AC) voltage section including AC connection nodes, the four-leg power converter including four phase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements; and wherein the method further comprises: determining at least one electrical operational characteristic for each of the four phase legs; generating control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, wherein the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and wherein the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and driving the power switching elements of the four phase legs in accordance with the control reference targets.

61. A non-transitory computer readable medium storing instructions that, when executed by a computer, control the computer to: -119- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 determine a first electrical characteristic at a positive battery terminal node of a direct current (DC) / DC converter, wherein the DC / DC converter includes: a DC voltage section including a DC bus and with a battery connection section including the positive battery terminal node and a negative battery terminal node, a first half bridge including first power switching elements and a first LC filter, wherein the first LC filter is connected to the positive battery terminal node, and a second half bridge including second power switching elements and a second LC filter, wherein the second LC filter is connected to the negative battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target.

62. The computer readable medium of claim 61, wherein, to generate the first DC / DC control reference target and the second DC / DC control reference target based on the difference (Δ) the sum (Σ) of the first electrical characteristic and the second electrical characteristic, the instructions further control the computer to: determine the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; determine a difference reference target (Δ**) and a sum reference target (Σ**) based on the difference (Δ) and the sum (Σ) of the first electrical characteristic and the second electrical characteristic; and translate the difference reference target (Δ**) and the sum reference target (Σ**) to the first DC / DC control reference target and the second DC / DC control reference target. -120- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 63. The computer readable medium of claim 61, wherein, to drive the first and second power switching elements in accordance with the first and second DC / DC control reference targets, the instructions further control the computer to: determine a first duty cycle for a first switching control signal for the first power switching elements based on the first DC / DC control reference target; determine a second duty cycle for a second switching control signal for the second power switching elements based on the second DC / DC control reference target; drive the first power switching elements in accordance with the first duty cycle; and drive the second power switching elements in accordance with the second duty cycle.

64. The computer readable medium of claim 63, wherein the instructions, when executed, further control the computer to: determine a first switching frequency for the first switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching; and determine a second switching frequency for the second switching control signal to achieve soft switching control, and thereby implement variable frequency soft switching.

65. The computer readable medium of claim 63, wherein the instructions, when executed, further control the computer to: implement a first switching frequency for the first switching control signal to achieve soft switching control or critical soft switching control; and implement a second switching frequency for the second switching control signal to achieve soft switching control or critical soft switching control.

66. The computer readable medium of claim 63, wherein the instructions, when executed, further control the computer to: determine, by a central controller, the first and second electrical characteristics; generate, by the central controller, the first DC / DC control reference target and the second DC / DC control reference target; receive, by a first local controller for the first half bridge, the first DC / DC control reference target; -121- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 determine, by the first local controller, the first duty cycle for the first switching control signal for the first power switching elements based on the first DC / DC control reference target; drive, by the first local controller, the first power switching elements in accordance with the first duty cycle; receive, by a second local controller for the second half bridge, the second DC / DC control reference target; determine, by the second local controller, the second duty cycle for the second switching control signal for the second power switching elements based on the second DC / DC control reference target; and drive, by the second local controller, the second power switching elements in accordance with the second duty cycle.

67. The computer readable medium of claim 61, wherein the DC / DC converter is further coupled to an alternating current (AC) / DC power converter via the DC bus.

68. The computer readable medium of claim 67, wherein the instructions, when executed, further control the computer to: determine a voltage level of an electric vehicle battery coupled to the positive battery terminal node and the negative battery terminal node, control a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, control the set of contactors to connect the electric vehicle battery to the DC / DC converter, and drive the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level by the driving of the first power switching elements in accordance with the first DC / DC control reference target and the driving of the second power switching elements in accordance with the second DC / DC control reference target. -122- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 69. The computer readable medium of claim 67, wherein the AC / DC power converter is a four-leg power converter with a direct current (DC) voltage section connected to the DC bus and an^alternating current (AC) voltage section including AC connection nodes, the four-leg power converter including four phase legs including a first phase leg, a second phase leg, a third phase leg, and a fourth phase leg, each of the first, second, third and fourth phase legs having a respective LC filter and respective power switching elements; and wherein the instructions, when executed, further control the computer to: determine at least one electrical operational characteristic for each of the four phase legs; generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the four phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, wherein the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the four-leg power converter, and wherein the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the four phase legs in accordance with the control reference targets.

70. A reconfigurable power converter system comprising: an alternative current (AC) / direct current (DC) power converter including a DC bus and AC connection nodes, the AC / DC power converter having phase legs including a first phase leg, a second phase leg, and a third phase leg, each of the first, second, and third phase legs having a respective LC filter, respective power switching elements, and a respective AC connection node of the AC connection nodes; a DC / DC power converter with DC nodes coupled to the DC bus and with a battery connection section including a positive battery terminal node and a negative battery terminal node, the DC / DC power converter including a first half bridge including first power -123- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 switching elements and a first LC filter, wherein the first LC filter is connected to the positive battery terminal node; and a control system coupled to the AC / DC power converter and the DC / DC power converter, the control system configured to: determine an operational mode for the AC / DC power converter to be a three- phase mode having three AC phases, control the AC / DC power converter in the three-phase mode in which the first, second, and third phase legs each correspond to a respective phase of the three AC phases and the AC connection node of the first phase leg is connected to a first node of a three-phase AC system, the AC connection node of the second phase leg is connected to a second node of the three-phase AC system, and the AC connection node of the third phase leg is connected to a third node of the three-phase AC system, determine the operational mode for the AC / DC power converter to be a single- phase mode having a single AC phase, and control the AC / DC power converter in the single-phase mode in which the first and second phase legs each correspond to the single AC phase and the AC connection nodes of the first and second phase legs are connected to a first node of a single-phase AC system.

71. The reconfigurable power converter system of claim 70, wherein the three-phase mode is an asymmetric three-phase mode, wherein phase legs of the AC / DC power converter further include a fourth phase leg having a fourth LC filter, fourth power switching elements, and a fourth AC connection node, wherein, in the asymmetric three-phase mode, the fourth phase leg corresponds to a neutral leg and the fourth AC connection node is connected to a neutral node of the three- phase AC system, and wherein, in the single-phase mode, the third and fourth phase legs are connected to a second node of the single-phase AC system, and are operated in parallel and 180 degrees phase-shifted relative to the first and second phase legs. -124- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 72. The reconfigurable power converter system of claim 71, wherein the control system is further configured to: determine the operational mode for the AC / DC power converter to be a symmetric three-phase mode having three AC phases that are separated by 120 degrees, and control the AC / DC power converter in the symmetric three-phase mode in which: the first, second, and third phase legs each correspond to a respective phase of the three AC phases and the AC connection node of the first phase leg is connected to the first node of a three-phase AC system, the AC connection node of the second phase leg is connected to the second node of the three- phase AC system, and the AC connection node of the third phase leg is connected to the third node of the three-phase AC system, and operation of the fourth phase leg is disabled.

73. The reconfigurable power converter system of claim 71, wherein the control system is further configured to: determine the operational mode for the AC / DC power converter to be a symmetric split-phase mode having two AC phases that are separated by 180 degrees, and control the AC / DC power converter in the symmetric split-phase mode in which: the first and second phase legs corresponds to a first AC phase of the two AC phases and the AC connection nodes of the first phase leg and of the second phase leg are connected to a first node of a split-phase AC system, and the third and fourth phase legs corresponds to a second AC phase of the two AC phases and the AC connection nodes of the third phase leg and of the fourth phase leg are connected to a second node of the split-phase AC system.

74. The reconfigurable power converter system of claim 71, wherein the control system is further configured to: -125- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 determine the operational mode for the AC / DC power converter to be a asymmetric split-phase mode having two AC phases that are separated by 180 degrees, and control the AC / DC power converter in the asymmetric split-phase mode in which: the first phase leg corresponds to a first AC phase of the two AC phases and the AC connection node of the first phase leg is connected to a first node of a split- phase AC system, the second phase leg corresponds to a second AC phase of the two AC phases and the AC connection node of the second phase leg is connected to a second node of the split-phase AC system, and the fourth phase leg corresponds to a neutral leg and the fourth AC connection node is connected to a neutral node of the split-phase AC system.

75. The reconfigurable power converter system of claim 71, wherein the control system is configured to: determine at least one electrical operational characteristic for each of the phase legs; generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, wherein the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the AC / DC power converter, and wherein the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the phase legs in accordance with the control reference targets. -126- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 76. The reconfigurable power converter system of claim 71, wherein the DC / DC power converter further includes a second half bridge including second power switching elements and a second LC filter, wherein the second LC filter is connected to the negative battery terminal node.

77. The reconfigurable power converter system of claim 76, the control system is configured to: determine a first electrical characteristic at the positive battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target.

78. The reconfigurable power converter system of claim 71, wherein the control system is further configured to: determine the operational mode for the AC / DC power converter to be a reduced single-phase mode having the single AC phase, and control the AC / DC power converter in the reduced single-phase mode in which the first phase leg is connected to the first node of the single-phase AC system, the second phase leg is idle, the third phase leg is connected to the second node of the single-phase AC system, and the fourth phase leg is idle. -127- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 79. The reconfigurable power converter system of claim 70, wherein the control system is further configured to: determine a voltage level of an electric vehicle battery coupled to the positive battery terminal node and the negative battery terminal node, control a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, control the set of contactors to connect the electric vehicle battery to the DC / DC converter, and drive the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level.

80. The reconfigurable power converter system of claim 70, wherein the AC / DC power converter further includes a split phase capacitor block coupled to the DC bus and including an upper capacitor, a lower capacitor, a midpoint node coupled between the upper capacitor and lower capacitor, wherein, in the three-phase mode, the midpoint node is connected to a neutral node of the three-phase AC system, and wherein, in the single-phase mode, three phase legs including the first phase leg, the second phase leg, and the third phase leg correspond to the single AC phase and the AC connection nodes of the three phase legs are connected to the first node of the single-phase AC system, and the midpoint node is coupled to a second node of the single-phase AC system and is 180 degrees phase-shifted relative to the first, second, and third phase legs.

81. A method of converting voltage, the method comprising: determining, by a control system, an operational mode for an alternative current (AC) / direct current (DC) power converter to be a three-phase mode having three AC phases, wherein the AC / DC power converter includes: a DC bus, AC connection nodes, and phase legs including a first phase leg, a second phase leg, and a third phase leg, each of the first, second, and third phase legs having a respective LC filter, respective -128- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 power switching elements, and a respective AC connection node of the AC connection nodes, and wherein a DC / DC power converter with DC nodes is coupled to the DC bus and includes a battery connection section including a positive battery terminal node and a negative battery terminal node, the DC / DC power converter including a first half bridge including first power switching elements and a first LC filter, wherein the first LC filter is connected to the positive battery terminal node; controlling, by the control system, the AC / DC power converter in the three-phase mode in which the first, second, and third phase legs each correspond to a respective phase of the three AC phases and the AC connection node of the first phase leg is connected to a first node of a three-phase AC system, the AC connection node of the second phase leg is connected to a second node of the three-phase AC system, and the AC connection node of the third phase leg is connected to a third node of the three-phase AC system; determining, by the control system, the operational mode for the AC / DC power converter to be a single-phase mode having a single AC phase; and controlling, by the control system, the AC / DC power converter in the single-phase mode in which the first and second phase legs each correspond to the single AC phase and the AC connection nodes of the first and second phase legs are connected to a first node of a single-phase AC system.

82. The method of claim 81, wherein the three-phase mode is an asymmetric three-phase mode, wherein phase legs of the AC / DC power converter further include a fourth phase leg having a fourth LC filter, fourth power switching elements, and a fourth AC connection node, wherein, in the asymmetric three-phase mode, the fourth phase leg corresponds to a neutral leg and the fourth AC connection node is connected to a neutral node of the three- phase AC system, and wherein, in the single-phase mode, the third and fourth phase legs are connected to a second node of the single-phase AC system, and are operated in parallel and 180 degrees phase-shifted relative to the first and second phase legs. -129- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 83. The method of claim 82, further comprising: determining the operational mode for the AC / DC power converter to be a symmetric three-phase mode having three AC phases that are separated by 120 degrees; and controlling the AC / DC power converter in the symmetric three-phase mode in which: the first, second, and third phase legs each correspond to a respective phase of the three AC phases and the AC connection node of the first phase leg is connected to the first node of a three-phase AC system, the AC connection node of the second phase leg is connected to the second node of the three-phase AC system, and the AC connection node of the third phase leg is connected to the third node of the three- phase AC system, and operation of the fourth phase leg is disabled.

84. The method of claim 82, further comprising: determining the operational mode for the AC / DC power converter to be a symmetric split-phase mode having two AC phases that are separated by 180 degrees; and controlling the AC / DC power converter in the symmetric split-phase mode in which: the first and second phase legs corresponds to a first AC phase of the two AC phases and the AC connection nodes of the first phase leg and of the second phase leg are connected to a first node of a split-phase AC system, and the third and fourth phase legs corresponds to a second AC phase of the two AC phases and the AC connection nodes of the third phase leg and of the fourth phase leg are connected to a second node of the split-phase AC system.

85. The method of claim 82, further comprising: determining an operational mode for the AC / DC power converter to be a asymmetric split-phase mode having two AC phases that are separated by 180 degrees; and controlling the AC / DC power converter in the asymmetric split-phase mode in which: the first phase leg corresponds to a first AC phase of the two AC phases and the AC connection node of the first phase leg is connected to a first node of a split-phase AC system, -130- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 the second phase leg corresponds to a second AC phase of the two AC phases and the AC connection node of the second phase leg is connected to a second node of the split-phase AC system, and the fourth phase leg corresponds to a neutral leg and the fourth AC connection node is connected to a neutral node of the split-phase AC system.

86. The method of claim 82, further comprising: determining at least one electrical operational characteristic for each of the phase legs; generating control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, wherein the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the AC / DC power converter, and wherein the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and driving the power switching elements of the phase legs in accordance with the control reference targets.

87. The method of claim 82, the method further comprising: determining the operational mode for the AC / DC power converter to be a reduced single-phase mode having the single AC phase, and controlling the AC / DC power converter in the reduced single-phase mode in which the first phase leg is connected to the first node of the single-phase AC system, the second phase leg is idle, the third phase leg is connected to the second node of the single-phase AC system, and the fourth phase leg is idle.

88. The method of claim 81, the method further comprising: controlling the DC / DC power converter to convert received DC power from a first voltage level to a second voltage level. -131- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 89. The method of claim 81, wherein the DC / DC power converter further includes a second half bridge including second power switching elements and a second LC filter, wherein the second LC filter is connected to the negative battery terminal node, the method further comprising: determining a first electrical characteristic at the positive battery terminal node; determining a second electrical characteristic at the negative battery terminal node; generating a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; driving the first power switching elements in accordance with the first DC / DC control reference target; and driving the second power switching elements in accordance with the second DC / DC control reference target.

90. The method of claim 81, the method further comprising: determining a voltage level of an electric vehicle battery coupled to the positive battery terminal node and the negative battery terminal node, controlling a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, controlling the set of contactors to connect the electric vehicle battery to the DC / DC converter, and driving the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level.

91. The method of claim 81, wherein the AC / DC power converter further includes a split phase capacitor block coupled to the DC bus and including an upper capacitor, a lower capacitor, a midpoint node coupled between the upper capacitor and lower capacitor, -132- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 wherein, in the three-phase mode, the midpoint node is connected to a neutral node of the three-phase AC system, and wherein, in the single-phase mode, three phase legs including the first phase leg, the second phase leg, and the third phase leg correspond to the single AC phase and the AC connection nodes of the three phase legs are connected to the first node of the single-phase AC system, and the midpoint node is coupled to a second node of the single-phase AC system and is 180 degrees phase-shifted relative to the first, second, and third phase legs.

92. A non-transitory computer readable medium storing instructions that, when executed by a computer, control the computer to: determine an operational mode for an alternative current (AC) / direct current (DC) power converter to be a three-phase mode having three AC phases, wherein the AC / DC power converter includes: a DC bus, AC connection nodes, and phase legs including a first phase leg, a second phase leg, and a third phase leg, each of the first, second, and third phase legs having a respective LC filter, respective power switching elements, and a respective AC connection node of the AC connection nodes, and wherein a DC / DC power converter with DC nodes is coupled to the DC bus and includes a battery connection section including a positive battery terminal node and a negative battery terminal node, the DC / DC power converter including a first half bridge including first power switching elements and a first LC filter, wherein the first LC filter is connected to the positive battery terminal node; control the AC / DC power converter in the three-phase mode in which the first, second, and third phase legs each correspond to a respective phase of the three AC phases and the AC connection node of the first phase leg is connected to a first node of a three-phase AC system, the AC connection node of the second phase leg is connected to a second node of the three-phase AC system, and the AC connection node of the third phase leg is connected to a third node of the three-phase AC system; determine the operational mode for the AC / DC power converter to be a single-phase mode having a single AC phase; and -133- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 control the AC / DC power converter in the single-phase mode in which the first and second phase legs each correspond to the single AC phase and the AC connection nodes of the first and second phase legs are connected to a first node of a single-phase AC system.

93. The computer readable medium of claim 92, wherein the three-phase mode is an asymmetric three-phase mode, wherein phase legs of the AC / DC power converter further include a fourth phase leg having a fourth LC filter, fourth power switching elements, and a fourth AC connection node, wherein, in the asymmetric three-phase mode, the fourth phase leg corresponds to a neutral leg and the fourth AC connection node is connected to a neutral node of the three- phase AC system, and wherein, in the single-phase mode, the third and fourth phase legs are connected to a second node of the single-phase AC system, and are operated in parallel and 180 degrees phase-shifted relative to the first and second phase legs.

94. The computer readable medium of claim 93, wherein the instructions, when executed, further control the computer to: determine the operational mode for the AC / DC power converter to be a symmetric three-phase mode; control the AC / DC power converter in the symmetric three-phase mode; determine the operational mode for the AC / DC power converter to be a symmetric split-phase mode; control the AC / DC power converter in the symmetric split-phase mode; determine the operational mode for the AC / DC power converter to be a asymmetric split-phase mode; and control the AC / DC power converter in the asymmetric split-phase mode.

95. The computer readable medium of claim 93, wherein the instructions, when executed, further control the computer to: determine at least one electrical operational characteristic for each of the phase legs; -134- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 generate control reference targets in a stationary reference frame based on the at least one electrical operational characteristics and a rotational reference frame, the control reference targets including a respective control reference target for each of the phase legs, the rotational reference frame including a direct axis (d‐axis) component, a quadrature axis (q‐axis) component, a delta axis (δ‐axis) component, and a sigma axis (σ‐axis) component, wherein the delta axis component indicates a difference between a common mode electrical characteristic and a neutral electrical characteristic of the AC / DC power converter, and wherein the sigma axis component indicates a sum of the common mode electrical characteristic and the neutral electrical characteristic; and drive the power switching elements of the phase legs in accordance with the control reference targets.

96. The computer readable medium of claim 93, wherein the DC / DC power converter further includes a second half bridge including second power switching elements and a second LC filter, wherein the second LC filter is connected to the negative battery terminal node.

97. The computer readable medium of claim 96, wherein the instructions, when executed, further control the computer to: determine a first electrical characteristic at the positive battery terminal node; determine a second electrical characteristic at the negative battery terminal node; generate a first DC / DC control reference target and a second DC / DC control reference target based on a difference (Δ) between the first electrical characteristic and the second electrical characteristic and on a sum (Σ) of the first electrical characteristic and the second electrical characteristic; drive the first power switching elements in accordance with the first DC / DC control reference target; and drive the second power switching elements in accordance with the second DC / DC control reference target.

98. The computer readable medium of claim 93, wherein the instructions, when executed, further control the computer to: -135- Q   B\175073.00272\95982016.5Attorney Docket No.: 175073.00272 determine the operational mode for the AC / DC power converter to be a reduced single-phase mode having the single AC phase, and control the AC / DC power converter in the reduced single-phase mode in which the first phase leg is connected to the first node of the single-phase AC system, the second phase leg is idle, the third phase leg is connected to the second node of the single-phase AC system, and the fourth phase leg is idle.

99. The computer readable medium of claim 92, wherein the instructions, when executed, further control the computer to: determine a voltage level of an electric vehicle battery coupled to the positive battery terminal node and the negative battery terminal node, control a set of contactors to connect the electric vehicle battery to the DC bus to charge the electric vehicle battery when the voltage level is above a threshold, and when the voltage level is below the threshold, control the set of contactors to connect the electric vehicle battery to the DC / DC converter, and drive the DC / DC converter to step-down DC voltage on the DC bus from a first level to a second level to charge the electric vehicle battery with DC voltage at the second level.

100. The computer readable medium of claim 92, wherein the AC / DC power converter further includes a split phase capacitor block coupled to the DC bus and including an upper capacitor, a lower capacitor, a midpoint node coupled between the upper capacitor and lower capacitor, wherein, in the three-phase mode, the midpoint node is connected to a neutral node of the three-phase AC system, and wherein, in the single-phase mode, three phase legs including the first phase leg, the second phase leg, and the third phase leg correspond to the single AC phase and the AC connection nodes of the three phase legs are connected to the first node of the single-phase AC system, and the midpoint node is coupled to a second node of the single-phase AC system and is 180 degrees phase-shifted relative to the first, second, and third phase legs. -136- Q   B\175073.00272\95982016.5

Images