System and method for control of zero sequence regulated power converters - Patents.com

Abstract

An embodiment is disclosed that includes a non-isolated N-phase DC / AC power converter, where N>1, having a DC voltage section and an N-phase AC voltage section, the power converter including an energy storage device in each of three phases of the AC voltage section. The energy storage device is typically electrically coupled to terminals of the DC voltage section. The system further includes a controller for controlling a voltage of the energy storage device, the controller including one or more switching devices for controlling a voltage at one or more terminals of the energy storage device, and at least one model predictive control (MPC) module for generating control signaling based on electrical operating characteristics of at least some of the storage elements to operate the one or more switching devices to establish a zero sequence voltage stabilization behavior at the terminals of the energy storage device.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 226,136, filed July 27, 2021, U.S. Provisional Application No. 63 / 242,840, filed September 10, 2021, U.S. Provisional Application No. 63 / 345,896, filed May 25, 2022, U.S. Provisional Application No. 63 / 351,768, filed June 13, 2022, U.S. Provisional Application No. 63 / 226,059, filed July 27, 2021, U.S. Provisional Application No. 63 / 270,311, filed October 21, 2021, and U.S. Provisional Application No. 63 / 319,122, filed March 11, 2022, each of which is incorporated by reference in its entirety herein.

[0002] STATEMENT REGARDING FEDERALLY FUNDED RESEARCH This invention was made with Government support under 1653574 awarded by the National Science Foundation. The Government has certain rights in this invention. [Background technology]

[0003] Various types of power converters are manufactured and used in many industries and situations. Exemplary power converters include alternating current (AC) to direct current (DC) rectifiers, DC-AC inverters, and DC-DC converters. An AC-DC rectifier, also called an AC / DC rectifier, converts AC power to DC power. A DC-AC inverter, also called a DC / AC inverter, converts DC power to AC power. Power converters can be used for a variety of purposes, such as rectifying AC power from an AC grid source into DC power for charging a battery, or converting DC power from a battery back to AC power to drive a motor or to supply AC power to an AC grid. Additionally, power converters can be used in or connected to electric vehicles, engine generators, solar panels, and the like in a variety of situations. Summary of the Invention

[0004] A power converter can be described in terms of power conversion efficiency, power density, and cost, among other characteristics. In general, it is desirable to have a power converter that has higher power efficiency, higher power density, and lower cost. A highly efficient power converter can convert power (e.g., AC to DC, DC to AC, and / or DC to DC) without significant energy loss. A less efficient power converter experiences higher energy losses during power conversion. Such energy losses may manifest, for example, as heat generated by the power converter while converting power. The power efficiency of a power converter, inductor, or other electronic component is expressed as a percentage between 0 and 100% and is expressed by the formula:

number

number

[0005] Energy costs, including monetary and environmental costs, continue to be a significant factor across many industries that incorporate power converters. Thus, even small increases in the power efficiency of a power converter (e.g., of a tenth of a percent) are significant and highly desirable. Similarly, reductions in materials and size of power converters are significant and highly desirable, allowing for reductions in the cost and physical space required to house the power converter in systems that incorporate the power converter.

[0006] In grid-connected power converter applications, such as electric vehicle (EV) chargers and photovoltaic (PV) power sources, leakage current and DC bus utilization are factors that affect performance. For leakage current issues, bulky line frequency transformers are typically installed to break the leakage path at the point of common coupling (PCC), which increases the cost, volume, and weight of the system. For DC bus utilization, the DC bus voltage needs to be boosted to at least twice the grid voltage swing to avoid saturation issues that bring additional switching losses and challenges to the switch voltage withstand capability.

[0007] Some embodiments disclosed herein address these or other problems. For example, some embodiments disclosed herein relate to a non-isolated power converter having one or more of: (i) injection of multiples of N-phase harmonics for zero sequence voltage control, (ii) a cascade control system, (iii) model predictive control (MPC) for active damping to mitigate resonance, (iv) variable frequency critical soft switching (VFCSS), and (v) a modular converter block. These features may be included in the power converter embodiments independently or in any combination. For example, the power converter may include one of the above features, any two of the above features, any three of the above features, any four of the above features, or all five of the above features. Furthermore, in combination with any of these embodiments, the power converter may include at least one LC filter for each of the N phases of the power converter (N≧1), where a capacitor of each LC filter is connected to the DC bus positive terminal or the negative terminal of the power converter, and optionally, an additional capacitor of each LC filter is connected to the other of the DC bus positive terminal or the negative terminal of the power converter. These capacitors of multiple phases with a common point connected to the positive or negative terminal of the DC bus form a bypass path for zero sequence voltage control. The capacitor coupled to the DC bus positive terminal (upper capacitor) can also reduce both EMI and the total ripple current handling requirements of the power converter without increasing the total capacitance or volume. In some embodiments disclosed herein, an additional drain-source capacitor (C DS ) may be coupled between the drain and source terminals of the power switching device to slow the voltage rise during an on-off transition. This slower voltage rise may reduce switching losses in the power switching device.

[0008] Some embodiments disclosed herein include systems, methods, and other implementations (including hardware, software, and hybrid hardware / software implementations) directed to a novel modular model predictive control (MPC) method for a non-isolated N-phase DC / AC converter with zero-sequence voltage stabilization capability, for N≧1, and optionally for regulated common-mode voltage injection (e.g., third harmonic injection (THI) for three-phase systems, or multiples of any other harmonic) for the purpose of increasing the available fundamental frequency AC voltage swing for a given DC voltage. When N=1 or N=2, the DC / AC power converter is considered to be a single-phase system. When N=3, the power converter is a three-phase system, and when N>3, the power converter is referred to as a multi-phase system. Although the description herein may focus on a three-phase system, various embodiments and features described are applicable to any number of phases.

[0009] This non-isolated topology is designed to connect the common point of the three-phase LC filter capacitors to the positive / negative DC bus terminals to bypass the zero-sequence leakage current. The zero-sequence voltage MPC controller stabilizes the zero-sequence capacitor voltage to a constant, in some embodiments, approximately half of the DC bus voltage. Thus, the leakage current flowing through the grid or other coupling elements is attenuated. Furthermore, the regulated third harmonic voltage injection (THI) technique disclosed herein improves the utilization of the DC bus. By adding the third harmonic to the zero-sequence voltage MPC reference, stability and robustness are improved. Compared to conventional THI techniques, grid-connected power quality is improved since no extra harmonics are injected into the grid. Explicit MPC per phase simplifies the implementation complexity on the controller (e.g., digital signal processor (DSP)) and does not require updating angular rates in the state space matrix, which allows for offline MPC optimization. Compared to conventional proportional-integral (PI) controllers, the embodiments of the MPC controller disclosed herein provide power converter control with improved dynamic performance and control bandwidth with faster response.

[0010] In some examples, the power converter is driven using a variable frequency critical soft switching (VFCSS) scheme, which can provide improved efficiency and reduced filter volume (i.e., improved power density) of the power converter.

[0011] In some examples, the power converter is implemented by a combination of modular converter units or modules, also called autoconverter modules (ACMs), that are coupled together like building blocks to form a power converter having desired specifications. Each ACM may include, for example, a circuit board with input / output connections (e.g., for coupling to other ACMs and a central controller) and a converter block including power switching elements and an LC filter (e.g., configured in a half-bridge configuration).

[0012] In one embodiment, a power converter system includes an N≧1 non-isolated n-phase power converter having a DC voltage section and an N-phase AC voltage section, the power converter including power switching elements. A control system configured to control the power converter and also configured to determine a rotating reference frame target, the rotating reference frame target including a zero-sequence component target, the zero-sequence component target based on a multiple of the N-phase harmonic injection. The control system generates N control reference targets in a stationary reference frame, one for each of n phases of the n-phase power converter, based on the rotating reference frame targets, and generates control signals for the power switching elements based on the n control reference targets and drives the power switching elements according to the control signals.

[0013] In one embodiment, a method for converting a voltage is introduced. The method includes a first step of determining rotating reference frame targets, where the rotating reference frame targets include a zero-sequence component target, and the zero-sequence component target is based on a multiple of an N-phase harmonic injection. The method includes a second step of generating N control reference targets in a stationary reference frame based on the rotating reference frame targets, where one control reference target is generated for each of N phases of a non-isolated N-phase power converter, where N≧1. The power converter includes a dc voltage section, an N-phase AC voltage section, and a power switching element. The method includes a third step of driving the power switching element of the power converter according to the N control reference targets.

[0014] In one embodiment, a power converter system includes N≧1 non-isolated N-phase power converters having a DC voltage section and an N-phase AC voltage section. The power converter includes, for each of the N phases, an LC filter, a power switching element, and a cascade control system for controlling the power converter. The cascade control system may include a central controller including a processing unit, the central controller configured to receive electrical operating characteristics of the power converter and generate at least n control reference targets including at least one control reference target for each of the N phases of the power converter. The cascade control system includes at least one local model predictive control (MPC) controller, each of the at least one local MPC controllers including a local processing unit and configured to receive the control reference targets of the n control reference targets and generate control signaling based on the control reference target to operate at least one switching element of the power switching elements corresponding to a phase of the local MPC controller using model predictive control (MPC).

[0015] In one embodiment, a method of power conversion is introduced. The method includes a first step of receiving electrical operating characteristics of a power converter by a central controller of a cascaded control system including at least one local model predictive control (MPC) controller cascaded with the central controller. The electrical operating characteristics are characteristics of a non-isolated n-phase power converter, N≧1, having a DC voltage section and an N-phase AC voltage section, the power converter including power switching elements. The method includes a second step of generating, by the central controller, at least n control reference targets including at least one control reference target for each of the N phases of the power converter. The method includes a third step of receiving, by each of the at least one local MPC controller, a control reference target of the N control reference targets and generating, by each of the at least one local MPC controller using model predictive control (MPC), a control signaling based on the received control reference target to actuate at least one switching element of the power switching elements corresponding to a phase of the local MPC controller.

[0016] In one embodiment, a non-isolated N-phase power converter system includes a DC voltage section and an N-phase AC voltage section. The LC filter includes, for each of the N phases, a switch-side inductor, a capacitor, an output-side inductor, a power switching element, and a sensor. The sensor is configured to sense a first electrical characteristic of a first component of the LC filter selected from the group of the switch-side inductor, the capacitor, or the output-side inductor, and generate sensor data indicative of the first electrical characteristic. The controller power converter includes an electronic processor, and the controller is configured to receive the sensor data from the sensor, perform state estimation based on the sensor data, estimate a second electrical characteristic of a second component of the LC filter different from the first component, and generate control signaling to drive the power switching element based on the second electrical characteristic.

[0017] In one embodiment, a method of power conversion using a non-isolated N-phase power converter is introduced. The method includes sensing, by a sensor, a first electrical characteristic of a first component of an LC filter of the power converter to generate sensor data indicative of the first electrical characteristic. The first component of the LC filter is selected from the group of a switch-side inductor, a capacitor, or an output-side inductor. The method also includes receiving, by a local controller, the sensor data from the sensor. The method also includes performing state estimation by the local controller based on the sensor data to estimate a second electrical characteristic of a second component of the LC filter different from the first component. The method also includes generating, by the local controller, control signaling to drive a power switching element associated with the LC filter based on the second electrical characteristic.

[0018] In one embodiment, a power conversion system includes one or more power converter modules. Each power converter module includes a positive direct current (DC) terminal and a negative DC terminal. The power switching element pair includes a high side power switching element coupled to the positive DC terminal and a low side power switching element coupled to the negative DC terminal. The high side power switching element and the low side power switching element are coupled to each other at a midpoint node. The LC filter is coupled to the midpoint node, the positive DC terminal, and the negative DC terminal. The local controller is configured to receive a control reference target and generate control signaling to drive the power switching element pair based on the control reference target using model predictive control (MPC) and variable frequency soft switching.

[0019] In one embodiment, a method of power conversion is introduced. The method includes receiving, by a local controller of a power converter module, a control reference target. The local controller is coupled to a power switching element pair including a high side power switching element coupled to a positive DC terminal of the power converter module and a low side power switching element coupled to a negative DC terminal of the power converter module. The high side power switching element and the low side power switching element are coupled together at a midpoint node, and an LC filter is coupled to the midpoint node, the positive DC terminal, and the negative DC terminal. The method also includes generating, by the local controller, control signaling to drive the power switching element pair based on the control reference target using model predictive control (MPC) and variable frequency soft switching. The method also includes filtering, by the LC filter, a power signal provided to or received from the midpoint node.

[0020] In one embodiment, a power converter system comprises a non-isolated N-phase power converter. For n>=1, the non-isolated N-phase power converter comprises: a DC voltage section; an N-phase AC voltage section; and a cascade control system for controlling the power converter. The cascade control system can include a central controller including a processing unit. The central controller is configured to receive electrical operating characteristics of the power converter and generate at least N control reference targets including at least one control reference target for each of the N phases of the power converter. A plurality of model predictive control (MPC) controllers including at least two local MPC controllers per phase of the N-phase power converter. Each local MPC controller is associated with a respective converter block including a pair of power switching elements and an LC filter for a phase corresponding to the local MPC controller. Each of the local MPC controllers is configured to receive a control reference target of the N control reference targets for a phase associated with the local MPC controller and generate control signaling based on the control reference signal to drive the pair of power switching elements associated with the local MPC controller using model predictive control.

[0021] In one embodiment, a method of voltage conversion using N≧1 non-isolated N-phase power converter is introduced. The method includes receiving, by a central controller of a cascaded control system, a plurality of local model predictive control (MPC) controllers cascaded with the central controller. The method also receives electrical operating characteristics of the power converter, the power converter including a DC voltage section and an N-phase AC voltage section. The plurality of local MPC controllers includes at least two local MPC controllers per phase of the N-phase power converter. Each local MPC controller is associated with a respective converter block including a pair of power switching elements and an LC filter for a phase corresponding to the local MPC controller. The method also includes generating, by the central controller, at least N control reference targets including at least one control reference target for each of the N phases of the power converter. The method also includes receiving, by each of the local MPC controllers, a control reference target among the N control reference targets for a phase associated with the local MPC controller. The method also includes using model predictive control (MPC) to generate control signaling based on the control reference targets received by each of the local MPC controllers to drive pairs of power switching elements associated with the local MPC controllers.

[0022] The above and other aspects and advantages of the present disclosure will become apparent from the following description. In the description, reference is made to the accompanying drawings, which form a part of this specification and show one or more embodiments by way of example. However, these embodiments do not necessarily represent the full scope of the invention, and therefore, reference should be made to the claims and this specification to interpret the scope of the invention. In the following description, like reference numerals are used to refer to like parts from figure to figure. [Brief description of the drawings]

[0023] [Figure 1] 1 illustrates a power converter system according to some embodiments. [Diagram 2] 1 illustrates a half-bridge power converter according to some embodiments. [Diagram 3] 1 illustrates a multi-phase power converter system according to some embodiments. [Figure 4] 1 illustrates a converter system according to some embodiments. [Figure 5A-B] 13 illustrates a waveform for third harmonic injection according to some embodiments. [Figure 6] 1 illustrates a communication system for a cascade control system according to some embodiments. [Figure 7] 1 illustrates an MPC-based converter system according to some embodiments. [Figure 8] 1 illustrates a model predictive control (MPC) control system according to some embodiments. [Figure 9] 1 illustrates a state estimator according to some embodiments. [Figure 10] 1 illustrates timing diagrams and boundary conditions for soft switching according to some embodiments. [Figure 11] 1 illustrates a control system for variable frequency critical soft switching according to some embodiments. [Figure 12] 1 illustrates a power converter system including model predictive control (MPC) with variable frequency critical soft switching (VFCSS) in accordance with some embodiments. [Figure 13] 1 illustrates a control system for local MPC-VFCSS control using variable continuous frequency critical soft switching (VCFCCS) according to some embodiments. [Figure 14] 1 illustrates a control system for local MPC-VFCSS control using variable discrete frequency critical soft switching (VDFCCS) according to some embodiments. [Figure 15] 1 illustrates waveforms for VCFCCS and VDFCCS control according to some embodiments. [Figure 16] 1 illustrates plots of carrier and sampling signals for VDFCCS control according to some embodiments. [Figure 17A-B]1 shows experimental results for a power converter according to some embodiments. [Figure 18A-B] 1 illustrates an auto-converter module according to some embodiments. [Figure 19] 1 illustrates a power converter incorporating an auto-converter module according to some embodiments. [Figure 20] 1 illustrates a control diagram for a two-phase converter according to some embodiments. [Figure 21] 1 illustrates a process for transforming voltage using harmonic injection according to some embodiments. [Figure 22] 1 illustrates a process for converting voltage using a cascade control system according to some embodiments. [Diagram 23] 1 illustrates a process for converting power using state estimation according to some embodiments. [Figure 24] 1 illustrates a process for converting power using MPC-based control and variable frequency critical soft switching according to some embodiments. [Diagram 25] 1 illustrates a process for converting power in a modular power converter having multiple parallel converters per phase according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] One or more embodiments are described and illustrated in the following description and the accompanying drawings. These embodiments are not limited to the specific details provided herein and may be modified in various ways. Furthermore, there may be other embodiments not described herein. Also, functions performed by multiple components may be integrated and performed by a single component. Similarly, functions described herein as being performed by one component may be distributed and performed by multiple components. Furthermore, components described as performing a particular function may also perform additional functions not described herein. For example, a device or structure that is "configured" in a particular way may be configured in at least that way, but may also be configured in other ways not recited.

[0025] As used in this application, "non-transitory computer-readable medium" includes all computer-readable media, but not consisting of a transitory propagating signal. Thus, non-transitory computer-readable media can include, for example, hard disks, CD-ROMs, optical storage devices, magnetic storage devices, Read Only Memory (ROM), Random Access Memory (RAM), register memory, processor cache, or any combination thereof.

[0026] Furthermore, the phrases and terms used herein are for purposes of explanation and should not be considered 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. Furthermore, the terms "connected" and "coupled" are used broadly and include both direct and indirect connections and couplings and can refer to physical or electrical connections or couplings. Furthermore, the step "and / or" used in conjunction with two or more items is intended to cover the items individually and both items together. For example, "a and / or b" is intended to cover a (and not b), b (and not a), and a and b.

[0027] Disclosed herein are systems and methods relating to power converters, also referred to as voltage converters, that can provide power conversion with, among other advantages, increased power efficiency, increased power density, and / or reduced cost.

[0028] FIG. 1 illustrates a power converter system 100 according to some embodiments. The power converter system 100 includes a control system 105, a first direct current (DC) 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 having an electronic processor 155 and memory 157, and optionally, in some embodiments, one or more local controllers 160, each having an electronic processor 165 and memory 167. The power converter system 100, as well as other power converter systems provided herein, may be non-isolated power converter systems. That is, the power converter system may be coupled to an AC power source (e.g., a single-phase or three-phase power grid) or an AC load (e.g., a single-phase or three-phase motor) without a transformer. The use of a transformer is common in electrical circuits to provide isolation between a power converter and an AC power source or load. However, such a transformer may add inefficiency and size or volume to the power converter. Thus, the power converter systems provided herein are non-isolated, also referred to as transformerless, to increase efficiency and / or reduce size of the power converter system. Because the power converter is provided without transformer isolation, the power converter may include additional features to prevent transmission of unwanted signals or currents (e.g., leakage currents) from passing between the power converter and other circuit components (e.g., DC power sources, DC loads, AC power sources, AC loads, and other structures that contact or support the power converter). These additional features may include LC filters, zero sequence control of common mode voltages, harmonic injection, model predictive control, variable frequency critical soft switching, etc.

[0029] In operation, generally, the control system 105 controls the power switching elements of the power converter 115 using control signaling (e.g., pulse width modulated (PWM) signals) to convert power (i) from the DC load / power source 110 acting as a power source to the second power source / load 130 acting as a load, or (ii) from the second power source / load 130 acting as a power source to the DC load / power source 110 acting as a load. Thus, when the DC load / power source 110 is acting as a power source for the power converter 115, the second power source / load 130 is acting as a load for the power converter 115. Conversely, when the DC load / power source 110 is acting as a load for the power converter 115, the second power source / load 130 is acting as a power source for the power converter 115.

[0030] The DC load / power source 110 may be a direct current (DC) load, a DC power source, or both a DC load and a DC power source (i.e., depending on the mode of the power converter 115, it functions as a DC power source in some cases and as a DC load in other cases). In some examples, the DC load / power source 110 is a battery. In other examples, the DC load / power source 110 may be a capacitor, an ultracapacitor, a DC power source from a rectified AC power source (e.g., AC grid power converted to DC power by a diode bridge rectifier), etc. The second power source / load 130 may be an AC load, an AC power source, both an AC load and an AC power source (i.e., depending on the mode of the power converter 115, it functions as an AC power source in some cases and as an AC load in other cases), a DC load, a DC power source, or both a DC load and a DC power source (i.e., depending on the mode of the power converter 115, it functions as a DC power source in some cases and as a DC load in other cases). In some examples, the power source / load 130 may be an electric (AC) motor, an AC generator, an AC power supply grid, a DC battery, a DC capacitor, a DC ultracapacitor, a DC power source from a rectified AC power source (e.g., AC grid power converted to DC power by a diode bridge rectifier), etc.

[0031] 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 (AC) side or section of the power converter 115. The first side may be referred to as the input side or output side of the power converter 115 or may be referred to as the DC side of the power converter 115 depending on the mode of the power converter. The second side may be referred to as the input side or output side of the power converter or may be referred to as the AC side of the power converter 115 depending on the mode of the power converter. 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 having another number of phases.

[0032] In some embodiments, power converter 115 operates at high DC voltage levels. For example, during operation, the DC side of power converter 115 has a DC voltage (e.g., between the input terminals of power converter 115) of at least 200V, at least 600V, at least 800V, at least 1000V, at least 1200V, between 200V and 1200V, between 600V and 1200V, between 800V and 1200V, or another range. Such high DC voltage levels may be desirable in some situations, such as some electric vehicles. For example, some current electric vehicles (e.g., passenger cars and hybrid electric vehicles) operate with a DC bus voltage of about 200V to 400V. This DC bus voltage for passenger electric vehicles may increase in the future. Additionally, while some current electric vehicles (e.g., Class 4-8, off-road, or other larger electric vehicles) can operate with DC bus voltages in excess of 1000V, the high DC voltage levels can introduce challenges to typical power converter systems, such as increased leakage currents, increased common mode voltages, and higher rates of change of common mode voltages. These challenges can lead to resonances on the LC filter 120, shaft voltages, excessive bearing currents that can result in bearing failure (e.g., from discharge events when lubricant breakdown occurs), excessive motor shaft currents, excessive motor winding currents (e.g., insulation can be damaged), and excessive gear train currents (e.g., bearing currents can propagate to the gear train via electromagnetic interference (EMI) or noise, vibration, and harshness (NVH) resulting from damaged bearing race walls). However, the embodiments described herein can mitigate such challenges through improved LC filters and control techniques including harmonic injection, cascade controllers, MPC control, and / or variable frequency critical soft switching (VFCSS).

[0033] LC filter 120 may include an LC filter for each phase of power converter 115. Each LC filter may include at least an inductor and a capacitor, or at least an inductor and two capacitors, as described in more detail below (see, e.g., the description of FIGS. 2 and 3).

[0034] The sensors 140 include, for example, one or more current sensors and / or one or more voltage sensors. For example, the sensors 140 may include respective current and / or voltage sensors for monitoring the current and / or voltage of one or more of the DC load source 110, each phase of the second power source / load 130, each phase of the LC filter 120, or other nodes or components of the power converter 115. For example, if the LC filter 120 is a three-phase LC filter, the sensors 140 may include at least three current sensors, one for sensing the current of each phase of the three-phase LC filter 120. In some embodiments, additional or fewer sensors 140 are included in the system 100. For example, the sensors 140 may also include one or more vibration sensors, temperature sensors, etc. 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 sensors 140 may provide sensor data to the control system 105 indicative of the sensed characteristic of the system 100. Such sensor data may thus be indicative of electrical operating characteristics of system 100. In some examples, control system 105 infers or estimates a characteristic (e.g., current or voltage) at one or more nodes of power converter 115 based on sensor data from sensors 140 that do not directly sense the characteristic, but rather sense a different type of characteristic or even a different component. Further discussion of such inferences or estimates is provided below with respect to state estimation.

[0035] 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, a touch screen, a keyboard, etc.) and / or includes or is configured to provide output to one or more outputs (e.g., LEDs, a display screen, a speaker, a haptic generator, etc.). Other electronic devices and / or a user may communicate with system 100, and in particular control system 105, via I / O interface 142. For example, control system 105 may receive commands (e.g., from a user or another device) for power converter system 100 indicating a target torque, a target speed, a target power level, a conversion type, etc. In response, control system 105 may drive power converter 115 to achieve the target and / or conversion type indicated by the command.

[0036] The control system 105 generally monitors the system 100, including the power converter 115 (e.g., based on sensor data from the sensors 140), receives commands (e.g., via the input / output interface 142), and controls the power switching elements of the power converter 115 using control signaling (e.g., pulse width modulated (PWM) signals) to convert power (e.g., according to the sensor data and / or 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 that includes the central controller 150 and one or more local controllers 160. The cascaded control system can communicate 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 controllers 160. In some examples, the local controllers 160 each implement model predictive control (MPC) or another regulatory control scheme (e.g., PID control, PI control, etc.). In some examples, the central controller implements a non-MPC regulation technique, such as proportional-integral-derivative (PID) control or proportional-integral (PI) control.

[0037] 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 electronic controllers may further include a memory (e.g., memory 157 or 167). The memory may be, for example, one or more of a read-only memory (ROM), a random access memory (RAM), or other non-transitory computer-readable medium. 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 perform the associated controller functions described herein, including, for example, 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 perform the controller functions described herein, the electronic processor includes one or more hardware circuit elements configured to perform some or all of this functionality. Furthermore, although certain controllers, electronic processors, and memories may be referred to herein as respective single units, in some embodiments, one or more of these components are distributed components. For example, in some embodiments, the electronic processor includes one or more microprocessors and / or hardware circuit elements.

[0038] 2 illustrates an example of a half-bridge converter 200 that can function as the power converter 115 of the system 100 of FIG. 1. As illustrated, the converter 200 includes a DC terminal 220 (also referred to as a DC node, DC link, DC rail, etc.) having a positive DC terminal 222 and a negative DC terminal 224. The converter 200 further includes an interface terminal 225 (also referred to as an interface node) having a positive interface terminal 227 and a negative interface terminal 229. The converter 200 can operate as a bidirectional converter or a unidirectional converter (in either direction), depending on the configuration and control of the system in which it is implemented. Thus, in some examples, the DC terminal 220 can be an input terminal and the interface terminal 225 can be an output terminal (e.g., DC / DC conversion and DC / AC inversion), and in some examples, the DC terminal 220 can be an output terminal and the interface terminal 225 can be an input terminal (e.g., AC / DC rectification). Furthermore, the interface terminal 225 may be an AC input terminal (for example, for AC / DC rectification), an AC output terminal (for example, for a DC / AC inverter), or a DC output terminal (for example, for DC / DC conversion).

[0039] The converter 200 includes a DC link capacitor (C DC 1. The system further includes a high side (upper) power switching element (M1) 235 (also referred to as an upper switch or upper FET 235), a low side (lower) power switching element (M2) 240 (also referred to as a lower switch or lower FET 240), a midpoint node 242 connecting the drain terminal of the upper switch 235 and the source terminal of the lower switch 240, and an LC filter 245. The LC filter 245 is an example of the LC filter 120 of the system 100 of FIG.

[0040] The power switching elements 235 and 240 may each be a field effect transistor (FET) having respective gate, source, and drain terminals. The FETs may be, for example, MOSFETs, silicon carbide (SiC) FETs, gallium nitride (GaN) FETs, among other types of FETs.

[0041] The LC filter 245 is connected to the switch-side inductor L SW 250 and the lower capacitor C B 255 and the upper capacitor C A 215. The switch side inductor L SW 250 is coupled between the midpoint node 242 and a filter node 260. For example, the switch-side inductor L SW One end of the lower capacitor C250 is coupled to the midpoint node 242 and the other end is coupled to the filter node 260. B 255 is coupled between the filter node 206 and the negative DC terminal 224. For example, the lower capacitor C B A first end of 255 is coupled to the filter node 260 and a second end is coupled to the negative DC terminal 224. A 215 is coupled between the filter node 260 and the positive DC terminal 222. For example, the lower capacitor C A A first end of 215 is coupled to the filter node 260 and a second end is coupled to the positive DC terminal 222 .

[0042] In some examples, LC filter 245 is an LCL filter (an LC filter with an additional inductor (L)) in which an additional (interface) inductor is coupled between filter node 260 and the positive interface terminal 227.

[0043] The upper capacitor 215 allows the ripple currents at both the input and output nodes (nodes 222, 227) of the converter 200 to be shared. Since the ripple currents on the input and output nodes have some correlation, the differential mode currents at these input and output nodes can be cancelled through this capacitance. This reduction in differential mode currents can result in improved EMI performance and reduced total capacitor ripple current when compared to a typical half-bridge converter (e.g., when the total capacitance between the two converters is held constant). Furthermore, the reduction in total capacitor ripple current can allow for a reduction in capacitor size, for example, when the capacitor ripple current drives the capacitor sizing.

[0044] The converter is connected to a drain-source capacitor, C DS 265a and 265b, each coupled across one of the switches 235, 240, respectively. In particular, a first drain-source capacitance 265a is provided across the source terminal 270a and the drain terminal 275a of the upper switch (M1) 235, and a second drain-source capacitance 265b is provided across the source terminal 270b and the drain terminal 275b of the lower switch (M2) 240. DS ) 265a-b are collectively referred to herein as drain-source capacitors (C DS )265.

[0045] Drain-source capacitor (C DS ) 265 can slow down the voltage rise during the on-off transitions of switches 235 and 240. This slower voltage rise can in turn reduce the switching losses of switches 235 and 240.

[0046] In some examples of converter 200, the upper capacitor C A 215 and the drain-source capacitor C DS One or both of these are not included in converter 200.

[0047] As previously mentioned, in some examples, power converter 200 can function as power converter 115 of system 100 of FIG. 1. In the context of power converter 115 (and thus power converter 200) implementing an AC / DC rectifier or a DC / AC inverter, power converter 200 is a single-phase power converter 200. In some examples, multiple instances of power converter 200 are paralleled to collectively function as power converter 115 of FIG. 1 to provide single-phase conversion (whether rectification or inversion) or to provide DC / DC power conversion. In some examples, power converter 115 is a multi-phase power converter (e.g., operates with three or more phases of AC power). In such examples, power converter 115 can include multiple instances of power converter 200, each associated with a phase of the AC power, each instance having a shared DC terminal 220, and each instance having an independent V interface 2, 3 and 4. Examples of such power converters are provided in Figures 3, 4, 7 and 12. In some of these examples, as shown in Figures 19-20, multiple instances of power converters 200 are paralleled to collectively provide power conversion for each phase (e.g., two parallel power converters 200 for phase A, two parallel power converters 200 for phase B, and two parallel power converters 200 for phase C). In some examples, the particular number of parallel power converters 200 and the number of phases vary.

[0048] As used herein, converter block may refer to a half-bridge circuit as described with respect to converter 200 of Figure 2. For example, converter block 262 may include power switching elements 235 and 240, LC filter 245 (including upper capacitor 215 (if present) and additional interface inductors (if present)), their interconnection nodes (e.g., midpoint node 242, filter node 260, DC terminal 220, and interface terminal 225), and drain-source capacitor 265 (if present).

[0049] 3 shows a multi-phase power converter system 300 coupled to an AC grid 302. The multi-phase converter system 300 includes a multi-phase converter 304 coupled on the DC side to a battery 306 and coupled to the AC grid 302 via an LCL filter 308. The multi-phase converter 304 may function as the power converter 115 of the system 100 of FIG. 1, and the LCL filter 308 may function as the LC filter 120 of the system 100 of FIG. 1. In operation, the multi-phase converter 300 may function as a DC / AC inverter or an AC / DC rectifier, depending on the power source and the switching of the power switching elements.

[0050] 2. Each instance includes an upper switch 235 and a lower switch 240 with a drain-source capacitor coupled across each of the switches. The multi-phase converter 300 is further coupled to a battery 306 via DC terminals 220 and to the AC grid 302 via interface terminals 225. The multi-phase converter 300 includes three LCL filters 308. Each LCL filter 308 includes components similar to the LC filter 245 of FIG. 2 and includes an interface inductor (LCL) coupled between a filter node 260 and the interface terminal 225. fg That is, the LCL filter 308 includes a switch-side inductor 250 (L fs,a , L fs,b , or L fs,c ) and the lower capacitor 255 (C f,a , Cf,b , and C f,c ), and upper capacitor 215 (C f,a , C f,b , or C f,c A switch-side inductor 250 is coupled between the midpoint node 242 and a filter node 260.

[0051] In the depicted example, multi-phase converter 300 is coupled to a battery 306 and an AC grid 302. In other examples, multi-phase converter 300 is coupled to a DC source / load other than battery 306 (e.g., a capacitor, an ultracapacitor, a DC source from rectified AC power, etc.) and / or an AC source / load other than grid 305 (e.g., a three-phase motor, an engine generator, etc.). Additionally, multi-phase converter 300 includes a drain-source capacitor per switch, an upper capacitor 215 per phase, and an interface inductor per phase, although some examples do not include one or more of these components.

[0052] As shown in Figures 2 and 3, in some examples of the power converter system provided herein, the LC filter 120 (implemented as LC filter 245 in Figure 2 and 308 in Figure 3) includes an LC filter for each phase, with the common point of each capacitor connected to the negative terminal (and / or positive terminal) of the DC bus. This connection creates a bypass path for zero sequence voltage control. By utilizing topological modifications and zero voltage control, the common mode voltage can be stabilized and leakage current can be reduced.

[0053] Systems 100 and 400 are each examples of power converter systems that may incorporate various features provided herein, alone and in combination. In the following sections, the disclosure describes (I) Three-Phase Converter Modeling, (II) Harmonic Injection, (III) Cascade Control System, (IV) Model Predictive Control, (V) State Estimation, (VI) Variable Frequency Critical Soft Switching, and (VI) Modular Converter Blocks. These headings are included for convenience and should not be construed as limiting.

[0054] I. Three-phase Converter Modeling In some examples provided herein, a control scheme for controlling a power converter is based on a dq0 coordinate system. By using the dq0 coordinate system as provided herein, the control scheme can utilize the zero-sequence voltage component to control the common-mode voltage. Compared to the abc coordinate system, the active / reactive power and the common-mode voltage can be independently controlled with the d, q, and zero-sequence components of the dq0 coordinate system. From the abc reference coordinate system, a coordinate system model of a three-phase converter (e.g., as shown in FIG. 3) can be derived.

[0055] The state space equation in the abc coordinate system is

number

number

number

number

[0056] Because it is difficult to control a time-varying sinusoidal reference in the abc coordinate system and it is convenient to calculate the active / reactive power in the dq0 coordinate system to stabilize the zero-sequence voltage, the state-space model is transformed to the dq0 reference coordinate system for control purposes. For example, the dq0 coordinate system transformation is useful because the dq0 coordinate system can transform a time-varying sinusoidal waveform into an equivalent constant DC value. To implement control, the DC value may be easier to control than the AC value. However, conventional methods mainly utilize the dq system without considering the zero (zero sequence) component. The topology of the converter system 300, in which the common points of the AC three-phase capacitors are connected to the positive and / or negative terminals of the DC bus, allows for the extraction of the zero sequence from the abc coordinate system to the dq0 coordinate system and the control of the zero sequence voltage to half of the DC bus voltage. Thus, the common-mode voltage v cm is the zero sequence component and can be stabilized to a constant accordingly.

[0057] For a reference coordinate system transformation with zero sequence components, the abc coordinate system can be first transformed to αβ0 and then transformed to the dq0 coordinate system. From abc to αβ0, the Clarke transformation is applied as follows:

number

[0058] In the αβ0 system, the signal consists of two orthogonal sinusoidal AC waveforms in the α and β coordinate systems and a zero sequence component. A Park transformation is secondly performed to transform the αβ0 stationary reference frame into the rotating dq0 coordinate system, which is calculated as follows:

number

[0059] Based on the above Park and Clark equations for coordinate system transformation, the above state space equations can be transformed from abc to dq0.

number

number

number

number

[0060] By utilizing the dq0 state-space equation and the connection of three-phase capacitors with the positive / negative terminals of the DC bus and the common point, the zero-sequence voltage can be explicitly controlled and u cm can be stabilized.

[0061] In some examples, a different rotating reference frame other than the dq0 reference frame is used by the control system 105.

[0062] II. Harmonic injection for zero sequence voltage control In some power converter applications, such as grid-connected power converters for electric vehicle (EV) chargers for photovoltaic (PV) arrays, leakage current and DC bus utilization are two factors that affect the converter's performance. To address leakage current, a bulky line frequency transformer is typically installed to break the leakage path at the point of common coupling (PCC), which increases the cost, volume, and weight of the system. To improve DC bus utilization, the DC bus voltage can be stepped up (e.g., to be at least twice the grid voltage amplitude to avoid saturation issues), which brings extra switching losses and challenges to the switch voltage withstand capability.

[0063] To address these and other issues, in some examples, harmonic signals are injected into the power converter systems provided herein, which may be non-isolated (transformerless) converters. Conventional harmonic injection involves direct injection in the duty cycle used to modulate the switching elements, which reduces control stability and robustness, can cause divergence in PWM modulation, and injects extra harmonics into the grid, reducing the power quality of the grid voltage and current. In contrast, in some examples provided herein, the systems and methods provide harmonic injection for zero sequence voltage control. The disclosed systems and methods improve DC bus utilization without reducing control stability and robustness, and without injecting additional harmonics into the grid (or other AC sources or loads).

[0064] In some embodiments, a power converter system (e.g., system 100) has a non-isolated N-phase power converter and a control system that injects multiples of N-th phase harmonics for zero-sequence voltage control. For example, for a three-phase power converter (i.e., N=3), the injected harmonics may be third harmonic injection (THI), sixth harmonic injection, etc. Furthermore, rather than injecting harmonics directly into the duty cycle for modulation, in some examples, the system injects harmonics (e.g., sinusoidal or triangular voltage signals) into a zero-sequence voltage control signal of a set of direct quadrature zero-sequence (dq0) rotating reference frame control signals. The control signals may also be referred to as rotating reference frame reference targets. This approach provides additional regulation via constraints on the dq0 rotating reference frame control signals that do not apply when harmonics are injected directly into the duty cycle for modulation. Thus, system stability and robustness may be improved compared to direct duty cycle side injection techniques.

[0065] For example, referring to FIG. 4, a power converter system 100 is shown that may be an example of the power converter system 400 of FIG. 1. As shown, the power converter system 400 is a non-isolated three-phase power converter that includes a control system 105 that includes a central controller 150 and three local controllers 160a-c (each instance of the local controller 160 of FIG. 1). Each of the local controllers 160a-c may be associated with and control a respective converter block 262a-c. The converter blocks 262a-c may be instances of the converter block 262 described with respect to FIG. 2. The local controllers 160a-c may implement a particular control scheme for performing control of the associated converter block 262a-c. For example, the local controllers 160a-c may implement model predictive control (MPC), proportional-integral (PI) control, proportional-integral-derivative (PID) control, or another type of control or regulation, as described further below. In some embodiments, rather than a cascaded control system as shown, the control system 105 does not include the local controllers 160a-c. For example, the reference voltages generated by the central controller 150 may instead be directly mapped (eg, by a look-up table) to respective duty cycle values ​​provided to respective gate drivers 402 for each power switching element of the converter.

[0066] As shown, the central controller 150 controls the power converters 304 (e.g., i L,abc ;i g,abc ,v g,abc ) electrical characteristics of a reference electrical characteristic (e.g., i g,d *;i g,q *,v g,q*) and determines the fundamental frequency (theta or θ) of the AC load / source (e.g., AC grid) coupled to terminal 225. Based on these received and determined values, central controller 150 generates control reference signals in the dq0 reference frame. Central controller 150 then transforms the control reference signals to the stationary (abc) reference frame via dq0 / abc reference frame translator 410 and converts these control reference targets or 415 (e.g., v a *,v b *, and v c *) is provided to the local controllers 160a to 160c.

[0067] More specifically, the central controller 150 transforms the received electrical characteristics of the power converter 304 from a stationary reference frame to a dq0 reference frame (e.g., via the abc / dq0 translator 412). The central controller 150 converts the transformed electrical characteristics into the dq0 reference frame (e.g., i g,d * to i g,d and i g,q * to i g,q ) to a reference electrical characteristic in the voltage controlled reference signal (e.g., v d * and v q For example, regulator 413 (e.g., a PI or PID controller) generates the d and q components of a voltage control reference signal (v d *) to generate the resulting d component, the reference d component and the transformed grid current value (i g,d * and i g,d ) can be compared to the voltage control reference signal (v q *) to generate the resulting q-component of the reference and the transformed grid current value (i g,q * and i g,q ) can be compared to the d and q components of the voltage controlled reference signal. These d and q components of the voltage controlled reference signal are provided to a dq0 / abc translator 410. g,d * and i g,q) may be provided to central controller 150 by I / O interface 142 (see FIG. 1) from a memory (eg, memory 157) or another source based on received user input commands.

[0068] For the zero-sequence (0) reference component, the power converter system 400 uses a harmonic injector 405 (e.g., provided as part of the central controller 150). That is, the harmonic injector 405 generates the harmonic injection and provides the zero-sequence component target to the dq0 / abc reference frame translator 410.

[0069] As shown in FIG. 4, the harmonic injector 405 is a DC offset (e.g., V dc 2 and 3 , the control reference target 415 receives the voltage reference V OUT output by the translator 410, which refers to the target voltage of the lower capacitor of the control block 262a-c (e.g., capacitor 255, see FIGS. 2 and 3 ), the fundamental frequency (theta or θ) of the AC section of the power converter 115, and the control reference target 415 for each phase of the power converter 115. In this example, the control reference target 415 (also referred to as the power reference target) is the voltage reference V OUT output by the translator 410, which refers to the target voltage of the lower capacitor of the control block 262a-c (e.g., capacitor 255, see FIGS. 2 and 3 ). c,a* , V c,b* , and V c,c* Based on these characteristics, the harmonic injector 405 can calculate the zero sequence component target. In some embodiments, the harmonic injector 405 calculates the zero sequence reference component by summing two components: (i) a DC offset and (ii) a multiple of the Nth phase harmonic injection.

[0070] The first component, DC offset, is the DC bus voltage (V dcThis DC offset component of the zero sequence reference ultimately prevents leakage currents from flowing to the grid. That is, the zero sequence output current can be attenuated by a stabilization control of the zero sequence capacitor voltage provided by this DC offset, which is used as an input for the zero sequence voltage reference. The operating principle of the zero sequence voltage control is based on three-phase output capacitor voltage reference tracking. Specifically, in the central controller, the zero sequence component of the reference is set to half of the measured DC bus voltage v dc / 2. This reference is combined with a dq component reference from the output of the grid-side inductor current controller and then transformed to the abc reference frame as the control reference target 415 of the local controllers 160a-c. Thus, each of the control reference targets 415 can be composed of a sinusoidal AC component (based on the dq input to the translator 410) and a zero-sequence DC component (based on the zero-sequence (0) input to the translator 410). Thus, based on the control reference target 415 with the zero-sequence control integrated, the local controllers 160a-c adjust the zero-sequence voltage control to provide a stabilized common mode capacitor voltage and low leakage current. In some examples of the converter 300, this DC offset as a zero-sequence voltage reference provides its own advantages, so the DC offset can be used to reduce harmonic injection (e.g., the output of the injector 405 reduces the DC offset (V dc 410 as a zero sequence voltage reference without the addition of

[0071] In another example, DC bus utilization can be further improved by injecting an Nth phase harmonic along with this DC offset. By injecting an Nth harmonic into the zero-sequence voltage reference (i.e., summed with the DC offset), these two components form the zero-sequence portion of the control reference target 415 for the local controllers 160a-c. Thus, the local controllers 160a-c for each phase inject the capacitor voltage (v c、abc ) to adjust the

[0072] The harmonic injector 405 may calculate the Nth phase harmonic injection multiple based on the fundamental frequency and the control reference target 415. Thus, in some embodiments, the Nth phase harmonic injection multiple may be considered as a feedback signal calculated from N previous control reference targets generated by the control system in the stationary (abc) reference frame based on previously received rotating reference frame targets. In some embodiments, the Nth phase harmonic injection multiple is a sinusoidal signal. The harmonic injector 405 may derive the sinusoidal signal based on the Nth order of the fundamental frequency of the AC voltage section of the power converter. In other embodiments, the Nth phase harmonic injection is a triangular signal. The harmonic injector 405 may derive the triangular signal based on the average of the maximum and minimum values ​​of the fundamental frequency (θ) of the AC voltage section of the power converter. An exemplary equation that the harmonic injector 405 may use to calculate the sinusoidal or triangular signal is shown below:

[0073] Sine wave injection for third harmonic injection (Sin-RTHI) may be implemented by deriving a third order grid fundamental frequency (θ) component to be superimposed on the zero sequence voltage reference. The Sin-RTHI zero sequence voltage reference can be expressed as follows: v * 0,3rd =v dc / 2+V m D 3rd sin(3ωt)

[0074] Therefore, the abc coordinate system Sin-RTHI three-phase capacitor voltage reference v * c,abc can be expressed as follows: v * c,a =v * c,a +V m D 3rd sin(3ωt)

number

number

number

[0075] By utilizing harmonic injection into the zero-sequence voltage, the peak-to-peak capacitor voltage can be reduced to improve DC bus utilization and avoid duty cycle saturation at lower DC bus voltages. Figure 5A shows simulated waveforms of the third-order, fundamental frequency, and injection capacitor voltages for one grid period for Sin-RTHI.

[0076] The triangular space vector for third harmonic injection (Tri-RTHI) may be implemented by deriving the average of the maximum and minimum grid fundamental frequency component capacitor voltages superimposed on the zero sequence voltage reference. The Tri-RTHI zero sequence voltage reference can be expressed as follows: v * 0,3rd =v dc / 2-D 3rd [max(v * c,abc )+min(v * c,abc )]

[0077] Therefore, the abc coordinate system Tri-RTHI three-phase capacitor voltage reference v * c,abc can be expressed as follows: v * c,a =v * c,a -D 3rd [max(v * c,abc )+min(v * c,abc )] v * c,b =v * c,b -D 3rd [max(v * c,abc )+min(v * c,abc )] v * c,c =v * c,c -D 3rd [max(v* c,abc )+min(v * c,abc )].

[0078] FIG. 5B shows the simulated waveforms of the third fundamental frequency and the injection capacitor voltage for one grid period for the Tri-RTHI.

[0079] As shown in Figures 5A-5B, the DC bus utilization can also be improved to avoid the problem of duty cycle saturation. To evaluate the effectiveness of the injected third harmonic in Figures 5A-5B, the voltage gain is calculated by multiplying the fundamental component capacitor voltage peak value v base and the reference modulation waveform peak value v THI It can be defined as the ratio of

number

[0080] The maximum voltage gain of the continuous third harmonic injection method can be derived as π / 3 when the third harmonic is at the zero crossing point. Therefore,

number

[0081] By utilizing the disclosed harmonic injection techniques, the DC bus voltage can be reduced (eg, by a factor of 1.15), thus reducing the voltage stress and switching losses of the power switching elements.

[0082] In some embodiments, a control reference target 415 (here, V c,a* ,V c,b* , and V c,c*Instead of calculating the Nth phase harmonic injection multiple using a 1 / 2 Ω resistor, harmonic injector 405 may derive the Nth phase harmonic injection from a direct or indirect voltage measurement of each phase of power converter 115. For example, in the case of DC voltage measurements, harmonic injector 405 may receive an output from a respective voltage sensor of each of the N phases of power converter 115, or an output from an analog-to-digital converter (ADC) that converts the respective analog output of the voltage sensor into a digital signal indicative of a voltage measurement. As another example, in the case of indirect voltage measurements, harmonic injector 405 may receive one or more communications from local controller 160 indicating a voltage measurement of each of the N phases of power converter 115. Here, local controller 160 may measure the voltage directly and communicate the measurement to harmonic injector 405 as a voltage measurement. In both the direct and indirect examples, the voltage measurements are each calculated by measuring the capacitance (e.g., lower capacitor C) of an LC filter of each phase of power converter 115. B Or C f 255) (e.g., V c,a ,V c,b , and V c,c ) may also be used.

[0083] In these embodiments using direct or indirect voltage measurements, the Nth phase harmonic injection multiple can be considered a feedback signal calculated from at least N voltage measurements, including at least one voltage measurement for each phase of power converter 115. In some of these embodiments, the Nth phase harmonic injection multiple is a sinusoidal or triangular signal. The above example equations that harmonic injector 405 can use to calculate a sinusoidal or triangular signal can similarly be used to calculate a sinusoidal or triangular signal in these embodiments, with the voltage measurement signal replacing the control reference target in the equation, respectively.

[0084] Further, in some embodiments of power converter system 100, N is three and the multiple of the Nth phase harmonic injection is a third of the fundamental frequency of the AC voltage section of the power converter. However, as previously mentioned, in some embodiments, N may be another integer value and / or another multiple of the Nth phase harmonic may also be selected.

[0085] Although described with respect to system 400 of FIG. 4, the harmonic injection feature may, at least in some examples, be incorporated into the other power converter systems disclosed herein.

[0086] III.Cascade Control System In some embodiments, the power converter system includes a non-isolated N-phase power converter and a cascade control system. The cascade control system includes a central controller and at least one local controller. For example, with reference to systems 100 and 400 of FIGS. 1 and 4 above, the control system 105 may be a cascade control system including a central controller 150 cascaded with one or more local controllers 160. When the control system 105 is referred to herein as a cascade control system 105, it should be understood that the control system 105 includes at least one of the optional local controllers 160 in addition to the central controller 150. The cascade control system 105 may provide, for example, resonance damping, improved dynamic performance, and / or leakage current damping capabilities. Additionally, the cascade control system 105 may improve modularity of components (e.g., facilitating the addition and removal of local controllers and corresponding converter blocks as a modular auto-converter module), as described in more detail below with respect to FIGS. 18A-20.

[0087] In some embodiments of the cascade control system 105, the central controller 150 provides an outer loop of control, and each of the local controllers 160 provides a separate inner loop of control. For example, the central controller 150 may implement a PI controller, a PID controller, or other tuning controller that regulates control of the power converter 115 in a rotating reference frame (e.g., a dq0 reference frame). As part of the outer loop of control, the central controller 150 generates a control reference target (e.g., target 415) based on the regulation in the rotating reference frame. The control reference target may be generated in a stationary (abc) reference frame. Additionally, the central controller 150 may provide the control reference target to the local controllers 160. The local controllers 160 may be configured to control one or more of the N phases of the power converter 115, and the control of the N phases of the power converter 115 is divided among the local controllers 160. Thus, each phase of the power converter 115 may be associated with and controlled by a particular local controller 160.

[0088] Each local controller 160 implements inner loop control via model predictive control (MPC), PI control, PID control, or another tuning technique based on a control reference target (e.g., target 415) received from the central controller 150. For example, each local controller 160 also controls the voltage (v c ) may receive a measured or estimated voltage value of the capacitor voltage (v c ) and a control reference target (e.g., v c *), each local controller 160 controls its associated converter block 262 to produce a capacitor voltage (v c). The inner loop control provided by each local controller 160 includes generating control signaling to be provided to the power switching elements of power converter 115 (or, in FIG. 3, converter 304). For example, with reference to FIGS. 3 and 4, local controller 160a provides control signaling to the power switching elements 235, 240 (M1, M2) of a first phase of power converter 115, local controller 160b provides control signaling to the power switching elements 235, 240 (M3, M4) of a second phase of power converter 115, and local controller 160c provides control signaling to the power switching elements 235, 240 (M5, M6) of a third phase of power converter 115.

[0089] The central controller 150 and the local controllers 160 can communicate both monitoring information (e.g., sensor data) and control information with each other in real time (e.g., each control cycle). For example, each local controller 160 can determine and transmit to the central controller 150 electrical operating characteristics specific to one or more phases of the power converter 115 with which the local controller 160 is associated in real time. For example, with reference to FIG. 4, these electrical operating characteristics may be determined in real time based on the V g,abc ,i g,abc , and i L,abc( For example, V from the local controller 160a g,a ,i g,a , and i L,a; V from local controller 160b g,b ,i g,b , and i L,b; ;V from local controller 160c g,c ,i g,c , and i L,c)In some embodiments, the local controllers 160 provide other electrical operating characteristics. Additionally, the central controller 150 can determine and transmit a control reference target (e.g., 415) in real time to each local controller 160. Although the control reference target 415 is shown as a voltage reference target, in some examples, the control reference target 415 can be a current reference target (e.g., i L,abc * or i g,abc *) In such an example, the local controller 160 can control the power switching elements of each phase according to the current reference target.

[0090] 6 illustrates a communication system 600 for a cascade control system such as that described above with respect to converter system 400 and other converter systems provided herein. Communication system 600 illustrates an example of communication for at least some examples of converter system 100 and converter system 400 (e.g., where n=3). For example, communication system 600 is an example of a communication system that enables the communication described above with respect to the cascade control system of FIG.

[0091] The communication system 600 includes a central controller 150 and local systems 605a-n. Each local system includes a respective local controller 160a-n and a respective local converter or converter block 262a-n (an instance of the converter block 262 described with respect to FIG. 2). The central controller 150 and the local controllers 160a-n are communicatively coupled via a communication bus 615. The communication bus 615 may include a collection of dedicated communication paths between each local controller 160 and the central controller 150, may include a shared communication path between the local controllers 160 and the central controller 150 (e.g., the communication includes addressing information to identify the intended destination device), or may include a combination thereof.

[0092] As previously mentioned, the central controller 150 and the local controllers 160 can communicate both monitoring information (e.g., sensor data) and control information with each other in real time (e.g., each control cycle). For example, the local controller 160 can g,abc ,i g,abc , and i L,abc The electrical operating characteristics, including one or more of: c,abc *,i L,abc *, or i g,abc *) to their corresponding converter blocks 262. The local controllers 160 may further generate and send PWM control signals to their corresponding converter blocks 262. The PWM control signals output by the local controllers 160 may indicate the duty cycle and / or frequency of the PWM signals driving the gate terminals of each power switching element of the converter blocks 262, or may be the PWM signals themselves. Each converter block 262 may further include a respective gate driver for driving the power switching elements of the converter block, or the gate drivers for the local converter systems 605 may be considered part of the corresponding local controller 160.

[0093] As described in more detail below, in some embodiments, a state estimator (e.g., state estimator 900 in FIG. 9 ) is associated with each of the local controllers and provides estimates of one or more electrical operating characteristics of the phase associated with the local controller based on sampling of other electrical characteristics of the phase. For example, the state estimator may estimate the capacitor voltage (v c,abc ) and the grid-side inductor current (i g,abc ), the switched inductor current of the phase (referred to herein as the inductor current i L,abcA Luenberger observer technique can be implemented to estimate the state estimator (also called the state estimator). The use of a state estimator can reduce the number of sensors used in the system to provide electrical characteristics to the MPC controller, thereby reducing the cost and / or size of the motor circuit.

[0094] In some embodiments, the cascade control system further incorporates one or both of harmonic injection, as previously described, or MPC for active damping to mitigate resonances, as described below.

[0095] IV. Model Predictive Control In some embodiments, a power converter system includes a non-isolated N-phase power converter and a control system that utilizes model predictive control (MPC). When used in a power converter system (e.g., systems 100 and 400), MPC can provide, for example, active resonance damping, improved dynamic performance, and / or leakage current damping capabilities.

[0096] A controller of the control system 105, such as the central controller 150 or the local controllers 160, that implements MPC may be referred to as an MPC controller. The MPC controller may be configured to determine electrical operating characteristics of the power converter 115 (e.g., characteristics of each phase of the converter), determine one or more control reference targets for the power converter 115 (e.g., targets per converter phase), and then generate control signaling based on an MPC algorithm that uses the electrical operating characteristics and the control reference targets. The control signaling may be applied to operate power switching elements of the power converter 115 to perform voltage conversion and active damping and to mitigate resonances in the filter circuit 120 of the power converter 115.

[0097] An MPC controller (or MPC controller) may implement an MPC algorithm for each phase of the power converter 115 to generate control signaling. As used herein, MPC may refer to a control algorithm that is dynamically dependent or aware of the system (e.g., implements or uses a dynamic model that represents the converter under control) and predicts input commands or reference values ​​for controlling the behavior of the system by calculations based on the electrical characteristics of the converter and the dynamic model. Thus, MPC as used herein may refer to model predictive control algorithms (as described in more detail below) in a stricter usage of the term, as well as other dynamic predictive algorithms (e.g., a linear quadratic regulator (LQR) control algorithm).

[0098] In one example, to implement the MPC algorithm for a particular phase, the MPC controller can solve a cost function using the electrical characteristics and control reference target of that phase at each control period. By solving the cost function, the MPC controller can predict future steps of control signaling to operate power switching elements to control the power of that phase of the AC voltage section of the power converter toward the control reference target. The MPC controller can then generate the control signaling for that particular stage based on the first step of the future steps of the control signal. Thus, in contrast to the PI control algorithm, the MPC algorithm derives the optimal duty cycle by linearly processing the state variables and tracking error with specific coefficients. Since no integration procedure is required in MPC, the dynamic performance of MPC can be improved compared to the PI technique with less overshoot and faster tracking speed. Furthermore, since MPC has a higher control bandwidth, the MPC controller can provide active damping terms to mitigate (reduce or eliminate) LC or LCL resonances that may otherwise be present in the filter circuit in the AC section of the power converter 115.

[0099] Figure 7 illustrates a power converter system 700 including MPC control. Converter system 700 is an example of systems 100 and 400 described above, in which local controllers 160 are implemented as MPC controllers. In particular, in Figure 7, these local controllers are identified as local MPC controllers 760a-c. Thus, the above description of system 400 of Figure 4 also applies to system 700 of Figure 7, with like numbers used for like components.

[0100] As shown in Figure 7, converter system 700 includes a control system 105, which is a specific example of the control system 705 referenced above (e.g., with respect to Figures 1 and 4). The control system 705 includes a central controller 150 and local controllers 760a-c. Although shown separately, the gate drivers 402 may also be considered part of the local controllers 760a-c. The converter system 700 is a three-phase converter configured to function as an AC / DC rectifier and / or a DC / AC inverter.

[0101] The central controller 150 may, for example, in a manner similar to that described above with reference to FIGS. 4 and 6, provide three-phase control references (three-phase capacitor voltage references v c,abc The local MPC controllers 760a-c also generate L,abc and v * c,abc By adjusting the weighting coefficient between the switch-side inductor current i L,abc Adjust.

[0102] Each local MPC controller 760 performs MPC-based control for each phase in the stationary abc coordinate system. In this example, the MPC-based control involves applying a dynamic model of the corresponding converter circuit under control (e.g., converter block 262a-c of a particular phase associated with each MPC controller 760a-c). More specifically, the MPC-based control involves solving an optimization function defined based on the dynamic model to identify an (optimal) control input (or inputs). The dynamic model may include measurements or estimates of the dynamic system as well as target or reference commands. In some examples, the MPC-based control involves solving an optimization function for each control period over a finite time range to identify control inputs for each step within the time range to achieve a desired output. The control input of the first step is then applied while the other control inputs are discarded. In the next control period, the process is repeated to identify the next control input. In some examples, another MPC control algorithm is implemented.

[0103] Using local MPC controllers 760 to implement MPC-based control for each phase in the stationary abc coordinate system includes, for example: (1) the state-space matrices of the LC for each phase are simpler than the rotating dq (or dq0) system for implementing offline piecewise affine optimization code in lower-cost controller hardware (e.g., cheaper DSP controllers); (2) the explicit MPC state-space matrices for the offline optimization calculations allow the omission of the time-varying angular velocity term ω used in the calculations; and (3) the MPC for each phase for LC is more flexible in terms of modular design for extending the number of parallelized phases and other topologies, e.g., DC / DC, single-phase DC / AC converters.

[0104] In the case of MPC implementation, for each control period, the local MPC controllers 760a-c receive the sensor 140 (e.g., the switch-side inductor current (i L,abc ), capacitor voltage (v c,abc ), and grid current (i g,abc) from the central controller 150 and a control reference target 415 (here, a capacitor voltage reference, v * c,abc ) may be received. As previously mentioned, each of the electrical properties from sensors 140 may be directed to be sensed (e.g., by a current or voltage sensor), or one or more of the electrical properties may be inferred from another sensed electrical property (e.g., see the state estimation discussion below).

[0105] In some examples, each of the local MPC controllers 760a-c includes an offline generated piecewise affine search tree that is used to derive a duty cycle (e.g., an optimal duty cycle) for explicit MPC control. To this end, the state equation of the switch-side LC filter (e.g., LC filter 308) can be expressed as follows:

number

number

[0106] For the flexibility of implementing explicit MPC and the convenience of experimentally adjusting the DC bus voltage during testing, the last term U dc d(k) is the phase leg output voltage u x (k) can be substituted. The state space model can be expressed in standard matrix form as follows: X k+1 =AX k +Bv k +Ee k where the variables and matrices are

number

number

[0107] In the MPC formulation, the inductor current / capacitor voltage reference is

number

number

number

number

[0108] Therefore, the cost function contains two terms.

number

[0109] For the penalty cost function, Q and R represent the weighting coefficient matrices applied to the state and input values, respectively. Specifically, Q is a 2 × 2 row [Q 11 ,0;0,Q 22 ] column. Because the goal of the local MPC controllers 760a-c is to track the output capacitor voltage reference, in some examples, the corresponding weighting coefficient Q 22 is the switch-side inductor current term Q 11 R is constructed to be larger (e.g., 1000 times larger) than R. R is a 1 × 1 matrix [R 11 ]. R 11 Q 22 In other examples, other weighting factors may be used.

[0110] The constraints of the MPC controller can be expressed as follows:

number

number

[0111] FIG. 8 illustrates an exemplary implementation of an MPC control system 800 that may be executed by each of the local MPC controllers 760a-c. In this example, the MPC algorithm is implemented in an explicit manner. The MPC control algorithm executed by the local MPC controllers 760a-c is represented by an MPC control block 805. Specifically, a piecewise affine (PWA) feedback law is generated offline based on preselected state space modeling and constraints. The corresponding MPC partitions 810 are then stored in the memory of each local MPC controller 760a-c to be available for online search. In each control period, the MPC control block 805 searches n regions of the PWA MPC partition 810 (at block 820) to identify an active region r based on the input 815 received by the MPC control block 805. For example, the MPC control block 805 can use a binary search tree to search and quickly find the active region r from the n regions. Furthermore, each of the n regions is associated with a respective pair of identification H and K matrices. Therefore, the applicable active region r is determined by the matrix H r and K r This is determined based on the matrix H r ,K r Based on this, an applicable active region 4 is identified. Next, for the active region r, the corresponding feedback law matrix F r and G r(block 825) to calculate an input matrix that contains optimal input values ​​over a prediction horizon (or time window). The first value of the input matrix is ​​then output and applied to the dynamic system for MPC control, while the other input values ​​of the input matrix are discarded.

[0112] Thus, the (offline generated) MPC partitions 810 represent n regions of PWA feedback laws for the MPC control block 805 to search. During operation of the MPC control block 805 (online), the identity matrix H r and K r leads to the active region of the MPC partition 810, and the corresponding matrix F r and G r is the optimal input value for PWM modulation (u N (k)), where uN(k)=(v dc *d(k)), where vdc is the DC bus voltage between the DC terminals 220 (see, for example, FIG. 3), and d(k) is the duty cycle of the PWM control signal. r ,G r is derived based on the cost function and constraints described above.

[0113] In each control cycle, the MPC control block 805 receives an input 815 (e.g., i L (k),v(k),i g (k) and v c,ref (k), where k indicates phase a, b, or c, and the corresponding search matrix H r and K r Then, find the active region r with F s、c and G s、cA duty cycle d(k) is derived using a particular control law matrix of and output by the control block 805 (e.g., as part of uN(k)). The output duty cycle (d(k)) may be a value between 0 and 1. The output duty cycle is provided to a dynamic system 830 representing the converter block 262 (e.g., a gate driver associated with a local MPC controller 760a-c implementing the MPC control block 805 may receive the output duty cycle).

[0114] In some examples, control system 105 includes N MPC controllers (e.g., N local controllers 160, where N>1), one for each phase of power converter 115. In some embodiments, each MPC controller receives a control reference target for the phase associated with the MPC controller from a central controller (e.g., central controller 150). In other (non-cascaded control system) embodiments, each MPC controller determines its respective control reference target locally. For example, the MPC controllers may execute a separate MPC algorithm to derive the control reference target, or may include a non-MPC algorithm (e.g., a PI control algorithm, a PID control algorithm, etc.) executed to derive the control reference target.

[0115] In some embodiments, a state estimator is associated with each of the N MPC controllers to provide an estimate of one or more electrical characteristics of the phase associated with the MPC controller based on sampling of other electrical characteristics of the phase. For example, the state estimator may estimate the capacitor voltage (v c,abc ) and the grid-side inductor current (i g,abc ), the switched-side inductor current of the phase (referred to herein as the inductor current i L,abcA Luenberger observer technique can be implemented to estimate the state estimator (also called the state estimator). The use of a state estimator can reduce the number of sensors used in the system to provide electrical characteristics to the MPC controller, thereby reducing the cost and / or size of the motor circuit.

[0116] In some embodiments, an MPC for active damping to mitigate resonance may be included in a power converter that includes one or both of a cascade control system and harmonic injection, as previously described.

[0117] V. State Estimator As described herein, in some examples, the control system 105 or controller 150, 160, 760, or 805 uses or implements a state estimator to determine one or more electrical characteristics of the corresponding converter under control. The use of a state estimator can reduce the number of sensors in the system, which can reduce sensor cost, reduce converter volume (improve power density), and / or improve control performance through noise immunity (i.e., reduced noise) compared to sensing specific electrical characteristics.

[0118] For example, with reference to the various power converter systems described herein (e.g., converter systems 100, 200, 300, 700), three variables are considered: the switch-side inductor current (i Lfs ), filter capacitor voltage (v Cf ), and the grid filter inductor (i Lfg) can be estimated by the other two variables. FIG. 9 shows a state estimator 900 for use with cascaded model predictive control of an LCL filter system, such as converter 700 of FIG. 7. However, state estimator 900 is applicable to other converters using similar principles. State estimator 900 may be implemented by one of the controllers (e.g., controllers 150, 160, 760, 805), for example, as controller hardware or an executable software block. For example, referring to FIG. 7, state estimator 900 may be incorporated into each of local MPC controllers 760. Also, an example of a state estimator 900 included within a local MPC controller is shown in FIG. 12.

[0119] Specifically, the state estimator 900 calculates the capacitor voltage v Cf and the grid side inductor current i Lfg By sampling the switch-side inductor current

number

number

number

[0120] The state space equations for the discrete-time state estimator can be expressed in the standard matrix form:

number

number

number

number

number

[0121] L E is a 3×2 observer gain matrix that can be adjusted to achieve the minimum estimation error. A diagram of the state estimator is shown in Figure 9. The state observer minimizes the estimation error e(k) using the following dynamic equation: e k+1 =(A E -L E C E )e k It is.

[0122] The estimated gain can be derived by:

number

number

[0123] In this particular example, a system incorporating state estimator 900 may not have a current sensor to directly sense the switch-side inductor current, but may instead rely on estimating this current value (e.g., based on a sensed voltage on the low-side capacitor and / or a sensed current in the grid-side inductor). This approach may be beneficial because it may be difficult to directly sense the switch-side inductor current with a current sensor, for example, due to noise from the proximity of the sensor to the power switching devices of the converter.

[0124] In some embodiments, such a state estimator may be included in a power converter that includes one or more of a cascade control system, harmonic injection, or MPC-based control, as previously described.

[0125] VI. Variable Frequency Critical Soft Switching In some examples, one or more of the controllers provided herein (e.g., controllers 150, 160, 760) drive their corresponding power converter blocks 262 (e.g., forming converters 115, 200, 300, or 304) using a variable frequency critical soft switching (VFCSS) scheme. The VFCSS scheme can provide improved efficiency and reduced filter volume (i.e., improved power density) of the power converter. Soft switching allows turn-on switching losses to be replaced by turn-off switching losses, which is at least beneficial because the turn-on losses of at least some FETs (e.g., SiC FETs) are typically much larger than the turn-off losses. This VFCSS technique allows for an increase in switching frequency (e.g., 5 times) and a reduction in inductance (e.g., 20 times) while reducing FET switching losses, resulting in improved power density and efficiency.

[0126] VFCSS is implemented by varying the switching frequency to achieve a desired inductor ripple current in an LC filter (e.g., in LC filter 245 and switch-side inductor 250 of LC filter 308 in FIGS. 2 and 3) to provide a soft switching transition. The desired inductor ripple current is determined by the inductor current valley point being equal to the inductor threshold current I L,thr For a converter such as converter 200 of FIG. 2 or converter 304 of FIG. 3, I L,thr is set according to the dead time of inductor 250 and the boundary conditions of the peak / valley inductor current, which can be derived from the output capacitance of the corresponding switching elements 235, 240. d ) and peak-valley inductor current I L,max 及び I L,min , and , respectively. The inductor current and dead time values ​​that result in soft switching are identified as the soft turn on switching region or regions, and the inductor current and dead time values ​​that do not result in soft switching are identified as the hard switching region or regions. The soft switching region represents the operating region where there is sufficient time and current to discharge the output capacitance of the power switching element (M1 or M2) before turning on. Analytically, these boundaries are expressed as follows: (1 / 2)I L,max T d ≦Q min ≦0, (1 / 2)I L,min T d ≧Q max ≧0 Here, Q min and Q max is the minimum discharge threshold of the switch output capacitance for soft switching.

[0127] For large positive values ​​of the DC inductor current, the threshold current level -I L,thrA large current ripple (e.g., greater than 200% or in the range of 200%-300% of the current through the inductor) is used or required to keep the valley inductor current point lower than the threshold current I. The negative inductor current discharges the upper switch output capacitance during the turn-off transition of the lower switch. Similarly, for high negative values ​​of DC inductor current, the peak inductor current point is higher than the threshold current I. L,thr A large current ripple is also used or required to ensure that the threshold current is greater than . Zero voltage switching (ZVS) of the lower switch is achieved if the output capacitance of the lower switch is fully discharged by the positive inductor current during the turn-off transition of the upper switch. In general, to achieve complete soft switching over the entire cycle (e.g., the entire grid cycle), the current ripple should be large enough to ensure a bidirectional inductor current path or the dead time should be extended. Since an unnecessarily long dead time can introduce distortion, the VFCSS adjusts the switching frequency to maintain critical soft switching over the entire cycle. The VFCSS scheme is implemented to maintain a positive threshold current during the negative part of the cycle and a negative threshold current during the positive part of the cycle. The switching frequency to achieve this for any threshold can be calculated by the following equation:

number

[0128] 11 illustrates a control system 1100 for controlling a pair of switching elements of a power converter. In particular, the control system 1100 illustrates a controller 1160 that implements an exemplary control scheme for VFCSS control of the converter block 262 (see FIG. 2). In some examples, the controller 1160 is a specific implementation of one or more of the controllers 150, 160, 750, and 760. The controller 1160 determines a reference duty cycle (d*) and a reference switching frequency (f SW The frequency generating controller 1110 includes a duty cycle generating controller 1105 and a frequency generating controller 1110, which may be regulators for generating a reference duty cycle (d*), respectively, based on sensed (or estimated) characteristics of the power converter 210, such as current and / or voltage, provided by the sensor 140, the state estimator 900, or a combination thereof. For example, the duty cycle generating controller 1105 may implement a PID controller, an MPC controller (see, e.g., MPC control block 805), or another type of regulator. The frequency generating controller 1110 may generate a reference duty cycle (d*), respectively, based on sensed (or estimated) characteristics of the converter block 262, such as current and / or voltage, provided by the sensor 140, the state estimator 900, or a combination thereof. SW *Based on the above formula to calculate the reference switching frequency (f SW *) can be generated.

[0129] The gate driver 1115 receives a reference duty ratio (d*) and a reference switching frequency (f SW *) based on the received reference values. The gate driver 1115 generates a first PWM control signal for the upper switch (M1) 235 and a second PWM control signal for the lower switch (M2) 240 based on the received reference values. For example, the gate driver 1115 generates a PWM control signal for the upper switch (M1) 235 and a second PWM control signal for the lower switch (M2) 240 at a frequency (f SW ) and generates a first PWM control signal having a duty cycle (d1) equal to the reference duty cycle (d*). Similarly, the gate driver 1115 generates a first PWM control signal having a reference switching frequency (f SW*) is equal to the frequency (f SW ) and 1-d1-(T d / f SW ) and / or a second PWM control signal with a duty cycle d2 equal to (1-D)*Tsw-(Td / fsw), and an ON edge of the second PWM control signal occurs a time T later than an OFF edge of the first PWM control signal. d / 2, and the OFF edge of the second PWM control signal is delayed by a time T d / 2 precedes.

[0130] While FIG. 11 illustrates VFCSS control for a single phase, FIG. 12 illustrates a VFCSS scheme implemented in a three-phase MPC control based power converter. More specifically, FIG. 12 illustrates a power converter system 1200 including MPC control with variable frequency critical soft switching (VFCSS). Converter system 1200 is another example of power system 100 and is similar to systems 400 and 700 described above, except that local controller 160 is implemented as an MPC-VFCSS controller. In particular, in FIG. 12, these local controllers are identified as local MPC-VFCSS controllers 1260a-c. Thus, the above description of system 100 of FIG. 1, system 400 of FIG. 4, and system 700 of FIG. 7 also apply to system 1200 of FIG. 12, with like numbers used for like components. Further, because system 1200 is in some respects an extrapolation of the single-phase VFCSS of FIG. 11 to a polyphase system, like components are numbered similarly with the addition of a phase designation of "a," "b," or "c," as the case may be (e.g., each of the three instances of frequency controller 1110 of FIG. 11 are identified as frequency controllers 1110a, 1110b, or 1110c in FIG. 12).

[0131] As shown in FIG. 12, converter system 1200 includes a control system 1205, which is a specific example of control system 105 and is similar to control system 705 referenced above (e.g., with respect to FIGS. 1, 4, and 7). Control system 1205 includes central controller 150 and local MPC-VFCSS controllers 1260a-c. Although shown separately, gate drivers 1115a-c may also be considered part of local MPC-VFCSS controllers 1260a-c. Converter system 1200 implements a three-phase converter configured to function as an AC / DC rectifier and / or DC / AC inverter. Thus, a converter circuit (e.g., power switching elements) identified as converter 304 may include respective converter blocks 262a-c for each phase a, b, c.

[0132] The central controller 150 calculates three-phase control references (three-phase capacitor voltage references v ) in the stationary abc reference frame based on the electrical characteristics of the converter 304 from the local controllers MPC-VFCSS 1260a-c, for example in a manner similar to that described above with respect to FIGS. c,abc *)

[0133] 12, each of the local MPC-VFCSS controllers 1260a-c includes a respective MPC controller 760a-c, a respective state estimator 900a-c, and a respective frequency controller 1110a-c. The MPC controllers 760a-c may function similarly to the MPC controllers 760a-c of FIG. 7, and may include a duty cycle reference d for the phase a, b, or c corresponding to the particular MPC controller 760a-c. a *,d b *, or d c11 to provide a reference frequency fsw* for a phase a, b, or c corresponding to a particular frequency controller 1110a-c. Further examples of frequency controllers 1110a-c are described below with reference to FIGS. 13-14. Gate drivers 1115a-c may function similarly to gate driver 1115 of FIG. 11 to provide an estimate of a phase a, b, or c corresponding to a particular state estimator 900a-c based on measurements provided by sensors 140. Frequency controllers 1110a-c may function similarly to frequency controller 1110 of FIG. 11 to provide a reference frequency fsw* for a phase a, b, or c corresponding to a particular frequency controller 1110a-c. Further examples of frequency controllers 1110a-c are described below with reference to FIGS. 13-14. Gate drivers 1115a-c may function similarly to gate driver 1115 of FIG. 11 to provide a reference frequency fsw* for a phase a, b, or c corresponding to a particular frequency controller 1110a-c. abc * and reference switching frequency f SW,abc Based on the *, a PWM control signal is provided to the power switching elements of the converter 304 for phase a, b, or c corresponding to the particular gate driver 1115a-c.

[0134] In some examples, state estimators 900a-c are not provided in system 1200, and instead, each of the measurements used by MPC controllers 760a-c and frequency controllers 1100a-c are provided by direct sensing via sensors 140 (e.g., as shown in FIGS. 11 and 14). In some examples, instead of MPC controllers 760a-c, separate local controllers 160a-c (e.g., PI or PID controllers) are provided for local PWM regulation of each phase of converter 304.

[0135] 13 and 14 show the reference switching frequency f SW12 show an example of a local MPC-VFCSS controller 1260 having different control strategies for generating the frequency .times. ...

[0136] The two controllers 1360 and 1460 are implemented to achieve the key soft switching behavior for high efficiency at different types of frequencies. The continuous frequency controller 1360 derives the continuous switching frequency based on the critical soft switching boundary conditions and then directly implements the frequency value into the PWM control signal (via the gate driver 1115). The continuous frequency controller 1360 also derives the switch-side inductor current value (i Lfs,est On the other hand, the discrete frequency controller 1460 discretizes the calculated switching frequency at multiples of the sampling frequency for PWM, and does not need to use the state estimator 900 to derive the switch-side inductor current value.

[0137] FIG. 15 shows the switch-side inductor current waveform 1500 for VCF-CSS and switch-side inductor current waveform 1505 VDF-CSS, respectively. The envelopes of VCF-CSS and VDF-CSS are smooth and discretized due to the different types of switching frequencies. Both techniques can achieve important soft-switching behavior to improve efficiency. Both VCF-CSS and VDF-CSS techniques can be combined with MPC-based control to address the time-varying switching frequency, and MPC-based control can improve transient performance with less oscillations and spikes, even in the case of discretized frequency VDF-CSS techniques. Therefore, the corresponding di / dt stress on the power switching elements of the converter is low.

[0138] More specifically, referring to FIG. 13, a continuous frequency controller 1360 can be designed to calculate a desired continuous switching frequency based on the peak / valley switch-side inductor current and critical soft-switching boundary conditions. More specifically, the continuously varying switching frequency f SW,cal is the threshold current for the critical soft switching boundary condition (I th ) is derived based on the switch side inductor current ripple Δi Lfs can be calculated as follows:

number

number

number

[0139] As shown in FIG. 13, a continuous frequency control block 1310 (an example of the frequency controllers 1110a to 1110c in FIG. 12) receives i Lfs,est ,v Cf,est and i Lfg,est and a reference duty cycle value (d*) from the MPC controller 760. Based on these received values, the continuous frequency control block 1310 determines the reference switching frequency f SW,cal The frequency controller 1310 calculates the reference switching frequency f SW,cal to the gate driver 1115.

[0140] State estimator 900 can provide a more accurate switch-side inductor current value for reference switching frequency calculation compared to direct sampling of the current (e.g., via sensor 140). For example, direct sampling via sensor 140 can result in deviation of the sampling from the true average inductor current value when the switching frequency changes, especially when critical soft switching current ripple is large. However, this deviation error can be mitigated as a result of the calculations performed by state estimator 900.

[0141] 14, discrete frequency controller 1460 includes similar components as continuous frequency controller 1360 (similarly numbered), except that it includes a discrete frequency control block 1410 instead of continuous frequency control block 1310 and state estimator 900. Discrete frequency control block 1410, like continuous frequency control block 1310, is another example of frequency controllers 1110a-c of FIG. 12. Instead of state estimator 900, discrete frequency controller 1460 (including MPC controller 760 and discrete frequency control block 1410) receives measurements from sensors 140 for associated currents and voltages.

[0142] In the discrete frequency controller 1460, the continuously varying switching frequency in the above equation is a function of the fundamental sampling frequency f SW,base The PWM signal is then further discretized into predetermined frequency bandwidth sections designed as integer multiples of f. Thus, the discretized variable switching frequency in the PWM signal is SW,base (

number

[0143] The relationship between the PWM switching carrier signal and the sampling signal (for the sensor 140) is shown in plot 1600 of FIG. SW,base 2F from SW,base , then f SW,base A variable switching frequency to is shown. The process of frequency discretization can be expressed as follows:

number

[0144] The discretized frequency may ring back and forth due to the oscillation of sampling noise during frequency change transients. After the frequency discretization process, a hysteresis loop is constructed to remove the frequency oscillation. Then, the reference discretized frequency (f SW,discrete ) to the gate driver 1115 to control the frequency of the PWM control signal to the converter 304.

[0145] Compared with VCF-CSS, VDF-CSS discretizes the switching frequency to multiple times the fundamental sampling frequency. This allows the switch-side inductor current to be sampled at the mean point of the current ripple without deviation from the correct value, as shown in Figure 16. Therefore, i Lfs Even without a state estimator to estimate V, the inductor current sampling can be accurate for critical soft-switching calculations at high current ripple.

[0146] 17A and 17B include plots 1700 and 1705, respectively, illustrating exemplary experimental results of one example of a power converter system 1200 as described herein incorporating a three-phase converter with SiC FETs (see, e.g., FIG. 3), third harmonic injection (see, e.g., FIG. 4), a cascaded control system (see, e.g., FIGS. 4, 6, and 7), an MPC-based local controller in the cascaded control system (see, e.g., FIG. 7), and variable frequency soft switching (see, e.g., FIGS. 11-14). Other examples provided do not include one or more of these features (e.g., a zero sequence voltage control reference of Vdc / 2 is provided in place of the third harmonic injection, or another local regulator is included in place of the local MPC-based control).

[0147] In Figure 17A, plot 1700 shows rate power (W) versus switching frequency (Hz) for power converter system 1200 as well as several other example systems. In Figure 17B, plot 1705 shows power density (kW / L) versus efficiency (%). As shown, in comparison to other systems, power converter system 1200 can achieve a high switching frequency and a balance of both high power density and high efficiency.

[0148] In some embodiments, a VFCSS as described may be included in a power converter that includes one or more of a cascade control system, harmonic injection, MPC-based control, or a state estimator as described herein.

[0149] VII. Modular Power Converters This section describes systems and methods for modular power converters composed of one or more modular power converter units, also referred to as autoconverter modules or power converter modules. Such autoconverter modules (ACMs) can be easily connected together for different applications and remain highly efficient power converters across different applications. As described further below, in some examples, each modular power converter may provide a single-phase multi-phase power output (e.g., in a DC / AC inverter application) or may receive a single-phase multi-phase power input (e.g., in an AC / DC rectifier application). In some examples, multiple modular power converters are coupled together in parallel for each phase of a multi-phase modular power converter. Any of the power converters previously described herein can be implemented as a modular power converter based on the principles described in this section. That is, in some examples, one or more of the previously described power converters 100, 400, 700, and 1200 are modular power converters composed of one or more ACMs.

[0150] Referring to FIG. 18A, a modular power converter 1800 is shown having a single ACM 1805. In FIG. 18B, a modular power converter 1820 is shown having n ACMs 1805 connected in parallel. Each ACM 1805 has a DC link capacitor (C DC ), a high-side switch, a low-side switch, a midpoint node connecting the drain terminal of the high-side switch and the source terminal of the low-side switch, and an LC filter. As shown, the ACM1805 converter 200 includes a source-drain capacitor for each of the high-side and low-side switches, and the LC filter includes both the high-side and low-side capacitors, as will be described in more detail with reference to FIG. 2. In some examples, one or more of the source-drain capacitor and the high-side capacitor of the LC filter are not included in the ACM1805 converter 200. Similar to FIG. 2, the ACM1805 converter 200 further includes DC terminals 220 including a positive DC terminal 222 and a negative DC terminal 224, and interface terminals 225 including a positive interface terminal 227 and a negative interface terminal 229.

[0151] Further, each ACM 1805 may include a single printed circuit board (PCB) on which the elements of converter 200 are mounted. Additionally, although not shown in FIGS. 18A-18B, a local controller 160 (e.g., in the form of a local MPC controller 760 or a local MPC-VCSS controller 1260) may be part of each ACM 1805 and may be implemented or otherwise included on the same PCB as converter 200 for that ACM. The PCB may be represented by a dashed box around each ACM 1805. Each ACM 1805 may be of a similar size, orientation, and general configuration so that it is modular and can be interchanged in and out of the converter system with another ACM 1805.

[0152] In some examples, a modular power converter is provided, such as modular power converter 1820, that includes n ACMs 1805 coupled to each other as shown in FIG. 18B and further coupled to a central controller (e.g., central controller 150) as shown in various power converter systems of the present disclosure (see, e.g., FIGS. 4, 6, 7, and 12). As described with respect to these examples, the central controller 150 can determine target operating parameters (e.g., at a macro level) for the modular ACMs 1805 and provide these target operating parameters to local controllers of those ACMs 1805. The local controllers can then control and adjust the power switching elements of their respective ACMs 1805 in accordance with their target operating parameters.

[0153] 18B , in some examples, the n ACMs 1805 include at least two power converter modules or three power converter modules coupled in parallel such that the positive DC terminals 222 of each ACM 1805 are coupled to each other, the negative DC terminals 224 of each ACM 1805 are coupled to each other, and the negative interface terminals 229 of each ACM 1805 are coupled to each other. Additionally, the positive interface terminals 227 of the ACMs 1805 of a particular phase of the AC may be coupled to each other, or in the example of one ACM 1805 per phase, each positive interface terminal 227 may be independent of (i.e., not coupled to) any other positive interface terminals 227 of the active ACMs 1805.

[0154] In some examples, modular power converters 1800 and 1820 are AC-DC rectifiers, DC-AC inverters, or multi-mode power converters having an AC-DC rectifier mode and a DC-AC inverter mode.

[0155] In some examples of modular power converters 1800 and 1820, each local controller is configured to drive a pair of power switching elements of one or more ACMs 1805 using variable frequency critical soft switching at a frequency of at least 100 kHz, between 100 kHz and 1 MHz, or between 300 kHz and 1 MHz. In some examples, the LC filter of each of the one or more power converter modules is configured to filter an AC power signal received by the LC filter, wherein the AC power signal has a current ripple of at least 200% of the local average current.

[0156] In some embodiments, a process for converting power with a modular power converter is provided. For example, the process may include receiving input power by one or more power converter modules. Each of the one or more power converter modules may include a circuit board having a positive direct current (DC) terminal and a negative DC terminal, a capacitor coupled across the positive and negative DC terminals, a power switching element pair, an LC filter including a capacitor and an inductor, a local controller coupled to the power switching element pair, the positive and negative DC terminals, the capacitor, the power switching element pair, the LC filter, and the local controller, as described above. The process may further include driving, by the local controller, the power switching element pair using variable frequency soft switching to convert the input power to an output power. The process may further include communicating, by a central controller, with each local controller of the one or more power converter modules.

[0157] Figure 19 illustrates a modular three-phase power converter 1900. Converter system 1900 is another example of power system 100 and may incorporate elements of systems 400, 700, 1200 previously described. Thus, the above discussion of similar aspects of system 100 of Figure 1, as well as system 400 of Figure 4, system 700 of Figure 7, and system 1200 of Figure 12 also applies to system 1900 of Figure 19, with similar numbers used for similar components.

[0158] The modular three-phase power converter 1900 includes three ACMs 1905, one for each phase of the three-phase power converter 1900. Each ACM 1905 is generally similar to the ACM 1805 of FIGS. 18A and 18B, but includes m parallel-connected converter blocks 262 in each ACM 1905. For example, in FIG. 19, three converter blocks 262 in the ACM 1905 for phase C are labeled, although there may be additional converter blocks 262 in phase C. In FIG. 19, three converter blocks 262 are also illustrated but not labeled for phases A and B for ease of illustration. As shown, each ACM 1905 includes shared DC and interface terminals for the m converter blocks 262 that make up that particular ACM 1905. Additionally, each converter block 262 in each ACM 1905 may be associated with a local controller on the same PCB as the converter block 262. Thus, the converter 1900 may include 3×m local controllers for a one-to-one relationship with the 3×m converter blocks 262. In other examples, a local controller may control multiple converter blocks 262. The local controller may be implemented as one of the local controllers described herein, such as local controller 160, 760, or 1260. In FIG. 19, the 3×m local controllers are represented by local MPC controllers 7601-760. 3m It is implemented as:

[0159] 19 is illustrated as having m converter blocks 262 and corresponding local MPC controllers each, in some examples, the ACM 1905 is an ACM assembly that includes m ACMs 1805. In other words, each phase of the converter 1900 may include multiple ACMs 1905 connected together to form the ACM 1805. Furthermore, in some embodiments, the power converter 1900 is constructed without modular ACMs 1805 or ACMs 1905 (e.g., the circuitry may not be modularized but rather may be on multiple circuit boards, custom boards, etc.).

[0160] 20 shows a control diagram for connecting another example of a single-phase converter 2000 of the power system 100 to one phase of the grid, which may be similar to the three-phase converter 1900, except that there is no third (C) phase and corresponding components (e.g., ACM 1905 for phase C). The single-phase converter 200 is configured with two phase legs ΦA and ΦB, which are connected to two terminals of a single-phase grid. Thus, the control diagram is equally applicable to the three-phase converter 1900, except that in the three-phase example, additional reference voltages (vc, c*) are provided to the local MPC control layer 2005, which has an ACM 1905 for the third (C) phase.

[0161] In FIG. 20, the local MPC control layer 2005 includes an ACM 1905 for phase A and phase B. The ACM 1905 for phase A includes x local MPC controllers 760a1 to 760a x Each local MPC controller 760a corresponds to a pair of gate drivers 402 and an instance of a converter block 262 (e.g., includes a pair of FETs and an LC filter). Similarly, the ACM 1905 for the B phase includes x local MPC controllers 760b1 to 760b x, where each local MPC controller 760b corresponds to a pair of gate drivers 402 and an instance of a converter block 262 (e.g., including a pair of FETs and an LC filter). In some examples, the ACM 1905 of the power converter 2000 of FIG. 20 may use the local MPC-VFCSS controller 1260 of FIG. 12 rather than the local MPC controller 760, and thus also incorporate the variable frequency critical soft switching and / or state estimator 900.

[0162] The modular multi-phase MPC power converter of Figures 19 and 20 implements a converter with power modules stacked in parallel for each phase to increase the current and power rating of each phase of the converter. Each of the stacked power modules receives a control reference target (e.g., a reference voltage (v cf,abc 12 and 13. Each local MPC controller in converters 1900 and 2000 of FIGS. 19-20 functions similarly to local MPC controller 760 and local MPC-VCSS controller 1260 described with respect to FIGS. 7 and 12, respectively, to control converter block 262 corresponding to the particular local MPC controller.

[0163] Thus, the ACMs 1805 and 1905 and cascaded MPC control described herein provide a modular power converter system whereby the ACMs 1805 and / or 1905 can be used as modular building blocks to design modular power converters meeting desired specifications in terms of number of phases, current ratings, power ratings, etc.

[0164] Although the various converter circuits provided herein are described primarily in the context of power switching element pairs including an upper switch and a lower switch, in some examples, one or more of these converters include power switching elements arranged in a multi-level switch topology (e.g., a three-level or five-level switch topology), and the power switching element pairs of each power converter module may include two or more high-side switching elements and two or more low-side switching elements.

[0165] In addition to the functions and operations of the various power converters previously described, the following are examples of the operating processes of the disclosed power converters.

[0166] In Figure 21, a process 2100 for converting a voltage using harmonic injection is provided. Process 2100 is described as being performed by power converter system 400 implemented as power converter system 100 of Figure 4. However, in some embodiments, process 2100 may be implemented by another power converter system, or by power converter system 100 implementing another power converter system (e.g., converter systems 700, 1200, 1900, 2000, or another system provided herein). Additionally, although the blocks of process 2100 are shown in a particular order, in some embodiments, one or more of the blocks may be performed partially or wholly in parallel, may be performed in a different order than that shown in Figure 21, or may be bypassed.

[0167] In block 2105, the control system 105 determines a rotating reference frame target including a zero sequence component target, where the zero sequence component target is based on a multiple of the Nth phase harmonic injection. For example, referring to FIG. 4, the central controller 150 determines a rotating reference frame target v d *,v q*, and v0* can be determined. The zero sequence component target is generated by harmonic injector 405, as described above. For example, harmonic injector 405 can calculate the zero sequence component target based on summing two components: (i) a DC offset (e.g., Vdc / 2) and (ii) a multiple of the Nth phase harmonic injection (e.g., the third harmonic).

[0168] In block 2110, the control system 105 generates N control reference targets in the stationary reference frame based on the rotating reference frame targets (N≧1, one control reference target is generated for each of the N phases of the non-isolated N-phase power converter). For example, referring to FIG. 4, the central controller 150, via the translator 410, translates the rotating reference frame targets to control the reference targets in the stationary reference frame. In particular, the translator 410 translates the control reference target v c,a *,v c,b *, and v c,c Generate *.

[0169] In block 2115, the control system 105 drives the power switching elements of the power converter according to the N control reference targets. For example, referring to FIG. 4, the local controllers 160a-c may drive the power switching elements of the power converter according to the N control reference targets v c,a *,v c,b *, and v c,c * based on the local controllers 160a-c to drive the power switching elements of the converter 304 (see also, e.g., FIG. 3). The local controllers 160a-c can drive the power switching elements using various techniques as provided herein, including, for example, MPC-based control, PID control, PI control. The local controllers 160a-c can further include variable frequency critical soft switching (see, e.g., FIGS. 11-16) and / or can be based on state estimation (see, e.g., state estimator 900 of FIG. 9).

[0170] As mentioned above, although process 2100 is described with respect to converter 400 of FIG. 4, process 2100 may similarly be performed by converters 700, 1200, 1900, and / or 2000. In such a case, central controller 150 (present in each of these converters) may function similarly to above to perform blocks 2105 and 2110, and the local controllers (e.g., local MPC controller 760 or local MPC-VCSS controller 1260) of each respective converter system may perform block 2115 to drive their associated power switching elements in accordance with the N control reference targets described herein (e.g., in the description of these local controllers 760 and local MPC-VCSS controller 1260).

[0171] In Fig. 22, a process 2200 for converting a voltage using a cascade control system is provided. Process 2200 is described as being performed by power converter system 700 implemented as power converter system 100 of Fig. 7. However, in some embodiments, process 2200 may be implemented by another power converter system, or by power converter system 100 implementing another power converter system (e.g., converter systems 400, 1200, 1900, 2000, or another system provided herein). Additionally, although the blocks of process 2200 are shown in a particular order, in some embodiments, one or more of the blocks may be performed partially or wholly in parallel, may be performed in a different order than that shown in Fig. 22, or may be bypassed.

[0172] In block 2205, the central controller receives electrical operating characteristics of the non-isolated N-phase power converter (where N≧1). For example, referring to FIG. 7, the central controller 150 receives the electrical operating characteristics v g,abc ,i g,abc , and i L,abcIn some examples, the central controller 150 receives fewer, additional, and / or different electrical operating characteristics of the power converters. The central controller 150 can receive the electrical operating characteristics from one or more of the local MPC controllers 760a-c and / or the sensors 140. As described with respect to FIG. 7, the central controller 150 and the local MPC controllers 760 form a cascade control system.

[0173] In block 2210, the central controller generates at least N control reference targets, including at least one control reference target for each of the N phases of the power converter. For example, referring to FIG. 7, the central controller 150 generates a rotating reference frame target (e.g., v d *,v q In particular, the translator 410 translates the control reference targets v, which represent the target voltages across the lower capacitors 255 (see, e.g., FIGS. 2 and 3) of each phase of the converter. c,a *,v c,b *, and v c,c Generate *.

[0174] In block 2215, each of the local MPC controllers 760a-c receives a control reference target among the N control reference targets. For example, the local MPC controller 760a receives the control reference target v c,a *, and the local MPC controller 760b receives the control reference target v c,b * The local MPC controller 760c receives the control reference target v c,c *Receive.

[0175] In block 2220, each of the local MPC controllers generates control signaling based on the received control reference target v to operate at least one switching element using model predictive control (MPC). For example, referring to FIG. 7, the local MPC controllers 760a-c generate control signaling based on the received control reference target v received from the central controller 150. c,a *,v c,b *, and v c,c * to drive power switching elements of converter 304 (see also, e.g., FIG. 3). Local MPC controllers 760a-c generate control signaling using MPC, as described in more detail above with respect to MPC controllers 760a-c and FIG. 7. In some examples, local MPC controllers 760a-c may further include variable frequency critical soft switching (see, e.g., FIGS. 11-16) and / or may be based on state estimation (see, e.g., state estimator 900 of FIG. 9).

[0176] The control signal may be a PWM control signal (or signals) provided to one (or both) of the power switching elements 235, 240 (e.g., at a gate terminal of the switching element), a reference duty cycle (d*) indicative of the duty cycle of the PWM control signal, and / or a reference switching frequency f SW * (For example, in the case of VFCSS) may be possible.

[0177] In Figure 23, a process 2300 for converting power using state estimation is provided. Process 2300 is described as being performed by power converter system 700 implemented as power converter system 100 of Figure 7. However, in some embodiments, process 2300 may be implemented by another power converter system, or by power converter system 100 implementing another power converter system (e.g., converter systems 400, 1200, 1900, 2000, or another system provided herein). Additionally, although the blocks of process 2300 are shown in a particular order, in some embodiments one or more of the blocks may be performed partially or wholly in parallel, may be performed in a different order than that shown in Figure 23, or may be bypassed.

[0178] In block 2305, a sensor (e.g., collectively sensors 140 or sensors of sensors 140) senses a first electrical characteristic of a first component of an LC filter (e.g., LC filter 308) of power converter system 700 to generate sensor data indicative of the first electrical characteristic. The first component of the LC filter may be a switch-side inductor, a capacitor, or an output-side inductor. For example, with reference to FIG. 3, LC filter 308 (also present in power converter system 400 of FIG. 7) includes switch-side inductor 250, low-side capacitor 255, and output-side inductor (grid inductor) 312.

[0179] At block 2310, a local controller (e.g., MPC controller 760a, 760b, or 760c of FIG. 7) receives sensor data from a sensor. The local controller may include a state estimator, such as state estimator 900 (see FIG. 9).

[0180] In block 2315, a local controller (e.g., local MPC controller 760a, 760b, or 760c) performs state estimation based on the sensor data to estimate a second electrical characteristic of a second component of the LC filter different from the first component. For example, with reference to FIGS. 3 and 7, the LC filter 308 includes three LC filters, one for each phase A, B, and C. Thus, in the context of this block 2315, an LC filter may refer to such an LC filter for one phase (e.g., phase A in FIG. 3) and be associated with a pair of power switching elements (e.g., upper switch (M1) 235 and lower switch (M2) 240 in FIG. 3) and one local controller (e.g., local MPC controller 760a in FIG. 7). In some examples, in block 2315 (and see FIG. 3 ), if the first component is phase A low side capacitor 255, the second component may be phase A switched inductor 250 or phase A output inductor 312. Alternatively, if the first component is phase A output inductor 312, the second component may be phase A switched inductor 250 or phase A low side capacitor 255.

[0181] To perform state estimation, the state estimator of the local controller 160 may solve the state space equations to implement a Luenberger observer, as described above with respect to state estimator 900 of Figure 9. Instead of the Luenberger observer, other estimation techniques may be used, such as, but not limited to, optimization-based estimators, sliding mode estimators, and disturbance estimators.

[0182] In block 2320, the local controller generates control signaling for driving the power switching elements associated with the LC filter based on the (estimated) second electrical characteristic. The power switching elements 235, 240 associated with the LC filter may be the power switching elements 235, 240 coupled to the LC filter via the midpoint node 242 connecting the power switching elements 235, 240 as shown in FIG. 3. For example, in the context of the converter system 700 of FIG. 7, the local MPC controller 760a, 760b, or 760c generates the control signaling as described above in more detail with respect to the MPC controllers 760a-c and FIG. 7. In some examples, the local MPC controller 760a-c may further include variable frequency critical soft switching (see, e.g., FIGS. 11-16) and / or may be based on state estimation (see, e.g., state estimator 900 of FIG. 9). In some examples, the local controller of block 2320 generates the control signaling based on the second electrical characteristic using a regulation technique other than MPC, such as a PID control or PI control technique.

[0183] The control signaling may include a PWM control signal provided to the power switching elements 235, 240 (e.g., at a gate terminal of the switching element), a reference duty cycle (d*) indicative of the duty cycle of the PWM control signal, and / or a reference switching frequency f indicative of the switching frequency of the PWM control signal. SW * (For example, in the case of VFCSS) may be possible.

[0184] 7 is a three-phase converter with a cascaded control system, in some examples process 2300 is performed with a single-phase converter with a cascaded control system (e.g., with one central controller 150 and one local MPC controller 760), or process 2300 is performed with a single-phase converter without a cascaded control system (e.g., with one local MPC controller 760 and no central controller 150). Further, in some examples, power converter system 400 (including any of local controllers 160a, 160b, 160c) performs process 2300, power converter system 1200 (including local MPC-VCSS controllers 1260a, 1260b, or 1260c) performs process 2300, and power converter 1900 (including local MPC controllers 760a, 760b, or 760c) performs process 2300. 01 ~ 3m ) performs process 2300, and / or power converter 2000 (using one of local MPC controllers 760) performs process 2300. Further, in some examples of power converters having multiple phases with one or more controllers per phase (see, e.g., power converter systems 400, 700, 1200, 1900, and 2000), each local controller includes a state estimator for estimating one or more electrical characteristics of an associated LC filter component based on sensor data of another component of the LC filter.

[0185] In Figure 24, a process 2400 for converting power using MPC-based control and variable frequency critical soft switching is provided. Process 2400 is described as being performed by power converter system 1200 implemented as power converter system 100 of Figure 12. However, in some embodiments, process 2400 may be implemented by another power converter system, or by power converter system 100 implementing another power converter system (e.g., converter systems 400, 700, 1900, or 2000, or another system provided herein). Additionally, although the blocks of process 2400 are shown in a particular order, in some embodiments one or more of the blocks may be performed partially or wholly in parallel, may be performed in a different order than that shown in Figure 24, or may be bypassed.

[0186] In block 2405, a local controller of the power converter system receives the control reference target. For example, the local MPC-VCSS controller 1260a receives the control reference target v from the central controller 150, as described above with respect to FIG. c,a *. As shown in FIG. 12, local MPC-VCSS controller 1260a is coupled to a pair of power switching elements of converter 304 including a high side power switching element coupled to the positive DC terminal of the power converter system and a low side power switching element coupled to the negative DC terminal of the power converter system, the high side power switching element and the low side power switching element being coupled together at a midpoint node. Additionally, the LC filter of LC filter 308 is connected to the midpoint node, the positive DC terminal, and the negative DC terminal. Further details of these connections relative to converter 304 and LC filter 308 are shown in FIG.

[0187] In block 2410, the local controller generates control signaling to drive the power switching element pair based on a control reference target using model predictive control (MPC) and variable frequency soft switching. The control signaling signal may include a PWM control signal (or signals) to be provided to one (or both) of the power switching elements of the power switching element pair (e.g., at the gate terminals of the switching elements), a reference duty cycle (d*) indicative of the duty cycle of the PWM control signal, and / or a reference switching frequency (f*) indicative of the switching frequency of the PWM control signal (e.g., in the case of a VFCSS). SW *) may also be used.

[0188] 12, a local MPC-VCSS controller 1260a generates control signaling to drive a pair of power switching elements of the converter 304. For example, the MPC controller 760a of the local MPC-VCSS controller 1260a generates a reference duty cycle (d*), and the frequency controller 1110a generates a reference switching frequency (f SW *), each of which is provided to the gate driver 1115a. The gate driver 1115a then drives an associated pair of power switching elements of the converter 304 with a respective PWM control signal having a switching frequency and duty cycle (or approximately one duty cycle) indicated by the received reference value. The MPC-based reference duty cycle (d*) and the VFCSS-based reference switching frequency (f SW Further details regarding one example of generation of *) are provided above with respect to MPC controller 760a and frequency controller 1110a.

[0189] In block 2415, an LC filter filters the power signal provided to or received from the midpoint node. For example, an LC filter (of LC filter 308) associated with the phase A power switching element pair and associated with local MPC-VCSS controller 1260a performs filtering of the power signal provided by the power switching element pair to the midpoint node (e.g., if the converter functions as a DC / AC inverter) and / or filtering of the power signal received by the power switching element pair from the midpoint node (e.g., if the converter functions as an AC / DC rectifier).

[0190] Although power converter 1200 shown in FIG. 12 is a three-phase converter with a cascaded control system, in some examples process 2400 is performed with a single-phase converter with a cascaded control system (e.g., with one central controller 150 and one local MPC-VCSS controller 1260), or process 2400 is performed with a single-phase converter without a cascaded control system (e.g., with one local MPC-VCSS controller 1260 and no central controller 150), and further, as noted in some examples, power converter system 400 (including any of local controllers 160a, 160b, 160c) performs process 2300, power converter system 700 (including local controllers 760a, 760b, 760c) performs process 2400, and power converter 1900 (including local MPC controllers 7601-760c) performs process 2400. 3m ) performs process 2400, and / or power converter 2000 (having one of local MPC controllers 760) performs process 2400. Further, in some examples of power converters having multiple phases with one or more local controllers per phase (see, e.g., power converter systems 400, 700, 1200, 1900, and 2000), each local controller (in combination with its associated LC filter) performs process 2400.

[0191] In Figure 25, a process 2500 is provided for converting power in a modular power converter having multiple parallel converters per phase. Process 2500 is described as being performed by power converter system 1900 implemented as power converter system 100 of Figure 4. However, in some embodiments, process 2500 may be implemented by another power converter system, or by power converter system 100 implementing another power converter system (e.g., converter systems 700, 1200, 1900, 2000, or another system provided herein). Additionally, although the blocks of process 2500 are shown in a particular order, in some embodiments one or more of the blocks may be performed partially or wholly in parallel, may be performed in a different order than that shown in Figure 25, or may be bypassed.

[0192] In block 2505, a central controller receives electrical operating characteristics of a power converter, the power converter including a DC voltage section and an N-phase AC voltage section. The central controller is part of a cascaded control system including a plurality of local model predictive control (MPC) controllers cascaded with the central controller. For example, referring to FIG. 19, the central controller 150 receives the electrical operating characteristics of the power converter. The electrical operating characteristics are transmitted to the local MPC controllers 7601-7605 in a manner similar to that received by the central controller 150 of the converter systems 400, 700, 1200 described above. 3m For example, the operating characteristics can be obtained by comparing the grid voltage (v g,abc ), the grid current of each phase of the inverter (i g,abc ), and the filter switch side inductor current of each phase of the inverter (i L,abc ).

[0193] Also, in a power converter (e.g., converter 1900) for process 2500, multiple local MPC controllers 7601-7603m comprises at least two local MPC controllers for each phase of the N-phase power converter. Further, each local MPC controller is associated with a respective converter block that includes a pair of power switching elements and an LC filter for the phase corresponding to the local MPC controller. For example, in the converter system 1900 of FIG. 19, each ACM module 1905 associated with a particular phase (e.g., phase A, B, or C) includes three converter blocks 262 as shown (and possibly more as indicated by ovals).

[0194] In block 2510, the central controller generates at least N control reference targets, including at least one control reference target for each of the N phases of the power converter. In some examples, the central controller 150 of FIG. 19 is shown in more detail in FIG. 7. Thus, referring to FIG. 7, the central controller 150, via the translator 410, generates a rotating reference frame target (e.g., v d *,v q Specifically, the translator 410 translates the control reference targets v c,a *,v c,b *, and v c,c Generate *.

[0195] At block 2515, each of the local MPC controllers receives a control reference target of the N control reference targets for the phase associated with the local MPC controller. For example, if local MPC controllers 760a, 760b, and 760c are each associated with a respective converter block of phase A, then each of these local MPC controllers 760a, 760b, and 760c receives a control reference target of phase A (e.g., v c,a *) can be received from the central controller 150.

[0196] In block 2520, each of the local MPC controllers uses the MPC to generate control signaling based on the received control reference target to drive the pair of power switching elements associated with the local MPC controller. For example, the local MPC controllers 7601- 3m Each of these is a specific local MPC controller 7601~ 3m (For example, V c,a *, v c,b * and vc,c *) (one of the local MPC controllers 7601~~) to drive associated pairs of power switching elements of the converter based on the control reference target received by the local MPC controller 7601~~. 3m generate control signaling using MPC, as described in more detail above with respect to the MPC controllers 760a-c and Figure 7. In some examples, the local MPC controllers 760a-c may further include variable frequency critical soft switching (see, e.g., Figures 11-16), similar to the local MPC-VFCSS controller 1260, and / or may use state estimation (see, e.g., state estimator 900 of Figure 9).

[0197] The control signal may be a PWM control signal (or signals) provided to one (or both) of the power switching elements 235, 240 (e.g., at a gate terminal of the switching element), a reference duty cycle (d*) indicative of the duty cycle of the PWM control signal, and / or a reference switching frequency f SW * (For example, in the case of VFCSS) may be possible.

[0198] Execution of the various techniques and operations described herein may be facilitated by an electronic controller (e.g., a processor-based computing device), such as the central controller 150, local controller 160, local MPC controller 760, local MPC VFCSS controller 1260 described herein. Such an electronic controller may include a processor-based device, such as a computing device that may include a central processing unit (CPU) or processing core. In addition to the CPU or processing core, the system includes main memory, cache memory, and bus interface circuitry. The electronic controller may include memory storage devices, such as a hard drive (solid state hard drive or other type of hard drive) or flash drive, associated with the computer system. The electronic controller may further include a keyboard, keypad, or some other user input interface, and a monitor, such as an LCD (liquid crystal display) monitor, and may be located where a user can access them.

[0199] The electronic controller is configured to facilitate the implementation of, for example, a power converter (e.g., by controlling switching devices of a non-isolated three-phase DC / AC power converter system). Thus, the storage device may include a computer program product that, when executed on the electronic controller (which may be a processor-based device, as previously described), causes the processor-based device to perform operations that facilitate the implementation of the procedures and operations described herein. The electronic controller may further include peripheral devices for enabling input / output functions. Such peripheral devices may include, for example, a 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 relevant content to a connected system. Such peripheral devices may also be used to download software including computer instructions for enabling the general operation of the respective system / device. Alternatively and / or additionally, in some embodiments, dedicated logic circuits such as FPGAs (field programmable gate arrays), ASICs (application specific integrated circuits), DSP processors, graphics processing units (GPUs), application processing units (APUs), etc. may be used in the implementation of the electronic controller. Other modules that may be included in the electronic controller may include a user interface for providing or receiving input and output data. The electronic controller may include an operating system.

[0200] A computer program (also referred to as a program, software, software application or code) includes machine instructions for a programmable processor and may be implemented in a high-level procedural and / or object-oriented programming language and / or in an assembly / machine language. As used herein, the term "machine-readable medium" refers to any non-transitory computer program product, apparatus and / or device used to provide machine instructions and / or data to a programmable processor (e.g., magnetic disks, optical disks, memory, programmable logic devices (PLDs)), including non-transitory machine-readable media that receive machine instructions as machine-readable signals.

[0201] In some embodiments, any suitable computer-readable medium can be used to store instructions for performing the processes / operations / procedures described herein. For example, in some embodiments, a computer-readable medium can be transitory or non-transient. For example, a non-transient computer-readable medium can include media such as magnetic media (e.g., hard disks, floppy disks, etc.), optical media (e.g., compact disks, digital video disks, Blu-ray disks, etc.), semiconductor media (e.g., flash memory, electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.), any suitable media that is not transitory or lacks any representation of permanence in transmission, and / or any suitable tangible media. As another example, a transitory computer-readable medium can include signals, wires, conductors, optical fibers, circuits on a network, or any suitable media that is transitory and does not lack any representation of permanence in transmission, and / or any suitable intangible media.

[0202] Although certain embodiments have been disclosed in detail herein, this is done by way of example for illustrative purposes only and is not intended to be limiting with respect to the scope of the following appended claims. Features of the disclosed embodiments can be combined, rearranged, etc., within the scope of the invention to produce many more embodiments. Certain other aspects, advantages, and modifications are believed to be within the scope of the claims provided below. The presented claims represent at least some of the embodiments and features disclosed herein. Other unclaimed embodiments and features are also contemplated.

[0203] Further examples Example 1: A method, apparatus, and / or non-transitory computer-readable medium storing processor-executable instructions for a power converter system comprising a non-isolated n-phase power converter, where N≧1, having a DC voltage section and an N-phase AC voltage section, the power converter including power switching elements. A control system configured to control the power converter and also configured to determine a rotating reference frame target, the rotating reference frame target including a zero-sequence component target, the zero-sequence component target based on a multiple of the N-phase harmonic injection. The control system generates N control reference targets in a stationary reference frame, one for each of the n phases of the n-phase power converter, based on the rotating reference frame targets, and generates control signals for the power switching elements based on the n control reference targets and drives the power switching elements according to the control signals.

[0204] Example 2: The method, apparatus, and / or non-transitory computer-readable medium of Example 1, wherein the control system is a cascaded control system including a central controller including a processing unit and configured to determine a rotating reference coordinate system target and generate N control reference targets, and at least one local controller, each of the at least one local controller including a local processing unit and each of the at least one local controller configured to receive one of the N control reference targets and drive a portion of the power switching elements associated with the local controller in accordance with the control reference target.

[0205] Example 3: The method, apparatus, and / or non-transitory computer-readable medium of Example 1 or 2, wherein each of the at least one local controller is configured to implement model predictive control (MPC) to generate control signaling for the portion of the power switching elements to drive the portion of the power switching elements in accordance with a control reference target.

[0206] Example 4: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 1 to 3, wherein the central controller is further configured to receive at least one electrical operating characteristic from each of the at least one local controller, the electrical operating characteristic being in a stationary reference frame, transform the at least one electrical operating characteristic to a rotating reference frame, and determine direct axis (D-axis) and quadrature axis (Q-axis) components of the rotating reference frame target based on the at least one electrical operating characteristic in the rotating reference frame.

[0207] Example 5: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 1 to 4, wherein the central controller is further configured to determine a frequency of the alternating current power signal of the AC section of the power converter based on a first characteristic of the at least one electrical operating characteristic in the rotating reference frame.

[0208] Example 6: To determine direct axis (D-axis) and quadrature axis (Q-axis) components of the rotating reference frame target based on at least one electrical operating characteristic in the rotating reference frame, the central controller is configured to convert the current signal from the AC section of the power converter into direct axis (D-axis) and quadrature axis (Q-axis) current components in the rotating reference frame, generate a D-axis voltage component as the D-axis component of the rotating reference frame target based on a comparison of the D-axis current component to a desired D-axis current, and generate a Q-axis voltage component as the Q-axis component of the rotating reference frame target based on a comparison of the Q-axis current component to a desired Q-axis current, and to generate N control reference targets in the stationary reference frame based on the rotating reference frame targets, the central controller is further configured to convert the D-axis voltage component, the Q-axis voltage component, and the zero sequence component target to the stationary reference frame.

[0209] Example 7: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 1 to 6, wherein the zero sequence component target includes a DC offset plus a multiple of the Nth phase harmonic injection.

[0210] Example 8: The method, apparatus, and / or non-transitory computer-readable medium of Example 7, wherein at least one of the DC offsets is half the DC bus voltage of the DC voltage section of the power converter, or N is 3 and the multiple of the Nth phase harmonic injection is a third order of the fundamental frequency of the AC voltage section of the power converter.

[0211] Example 9: The method, apparatus, and / or non-transitory computer-readable medium of Examples 7 or 8, wherein the multiple of the Nth phase harmonic injection includes a sinusoidal signal derived based on the Nth order of the fundamental frequency of the AC voltage section of the power converter, or a triangular signal derived based on an average of the maximum and minimum values ​​of the fundamental frequency of the AC voltage section of the power converter.

[0212] Example 10: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 7-9, wherein the N-phase harmonic injection multiple is a feedback signal calculated from at least one selected from N previous control reference targets generated by the control system in a stationary reference frame based on previously received rotating reference frame targets, N voltage measurements provided by respective voltage sensors for each of the N phases of the power converter, or N voltage measurements communicated by at least one local controller indicative of a respective voltage at each of the N phases of the power converter.

[0213] Example 11: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 1 to 10, wherein the power switching elements include, for each of N phases of the power converter, a high side element and a low side element connected to a midpoint node, and the midpoint node of each of the N phases of the power converter is coupled to a respective LC filter including an inductor coupled between the midpoint node and a filter node, and one or more of a first capacitor coupled between the filter node and a positive DC bus of the power converter or a second capacitor coupled between the filter node and a negative DC bus of the power converter.

[0214] Example 12: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 1 to 11, wherein the power converter is one or more of an AC-DC rectifier and a DC-AC inverter.

[0215] Example 13: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 1 to 12, wherein the AC section of the power converter is coupled to an AC power grid or an AC motor.

[0216] Example 14: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 1 to 13, comprising an LC filter including a switch-side inductor and a capacitor, and a sensor configured to sense a first electrical characteristic of a first component of the LC filter selected from the group of the switch-side inductor and the capacitor and generate sensor data indicative of the first electrical characteristic, wherein each of the at least one local controller is further configured to receive the sensor data from the sensor, perform state estimation based on the sensor data to estimate a second electrical characteristic of a second component of the LC filter, different from the first component, and drive a portion of the power switching elements further based on the second electrical characteristic.

[0217] Example 15: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 1 to 14, wherein each of the at least one local controller is further configured to drive a portion of the power switching elements with a variable frequency critical soft switching control signal to drive the portion of the power switching elements.

[0218] Example 16: A power converter module further comprising: N power converter modules, N>1, each power converter module including: a power switching element pair including a positive direct current (DC) terminal and a negative DC terminal; a high side power switching element coupled to the positive DC terminal; and a low side power switching element coupled to the negative DC terminal, the high side power switching element and the low side power switching element being coupled to each other at a midpoint node; an LC filter including a capacitor and an inductor, the inductor being coupled between the midpoint node and the capacitor, and the capacitor being coupled between the inductor and the negative DC terminal; and a power converter module for driving the power switching element pair. 16. The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 1-15, wherein the central controller includes a local controller of the at least one local controller configured in a first order, the power switching element pair being part of a power switching element associated with the local controller, and a circuit board on which the local controller is located, the positive and negative DC terminals, the power switching element pair, the LC filter, and the local controller, wherein the positive DC terminals of each of the N power converter modules are coupled to each other and the negative DC terminals of each of the one or more power converters are coupled to each other, and the central controller is located on a circuit board separate from the circuit board having the local controller.

[0219] Example 17: A method, apparatus, and / or non-transitory computer readable medium storing processor executable instructions for converting a voltage, the method, apparatus, and / or non-transitory computer readable medium including a first step of determining a rotating reference frame target, the rotating reference frame target including a zero sequence component target, the zero sequence component target based on a multiple of an N-phase harmonic injection. The method includes a second step of generating N control reference targets in a stationary reference frame based on the rotating reference frame target, one control reference target generated for each of N phases of a non-isolated N-phase power converter, where N≧1. The power converter includes a dc voltage section, an N-phase AC voltage section, and power switching elements. The method includes a third step of driving the power switching elements of the power converter according to the N control reference targets.

[0220] Example 18: The method, apparatus, and / or non-transitory computer-readable medium of Example 17, including the steps of: determining a rotating reference coordinate system target by a central controller via a cascaded control system; generating N control reference targets by the central controller; receiving a control reference target from the N control reference targets by each of the at least one local controller; and driving a portion of the power switching elements in accordance with the control reference target by each of the at least one local controller.

[0221] Example 19: The method, apparatus, and / or non-transitory computer-readable medium of Example 17 or 18, wherein the step of driving, by each of the at least one local controller, a portion of the power switching elements in accordance with the control reference target includes a step of implementing model predictive control (MPC) by each of the at least one local controller to generate control signaling for the portion of the power switching elements.

[0222] Example 20: Rectifying, by a power converter, AC power into DC power based on driving power switching elements of the power converter according to N control reference targets; or 20. The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 17-19, further comprising one or more of the steps of: inverting, by the power converter, the DC power to AC power based on driving power switching elements of the power converter in accordance with the N control reference targets.

[0223] Example 21: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 17 to 20, further comprising one or more of: receiving AC power from an AC power grid by the AC section of the power converter; supplying AC power to an AC power grid by the AC section of the power converter; or supplying AC power to an AC motor by the AC section of the power converter.

[0224] Example 22: A method, apparatus, and / or non-transitory computer-readable medium storing processor-executable instructions for a power converter system comprising a non-isolated N-phase power converter having N≧1 DC voltage section and N-phase AC voltage section. The power converter includes, for each of the N phases, an LC filter, a power switching element, and a cascade control system for controlling the power converter. The cascade control system may include a central controller including a processing unit, the central controller configured to receive electrical operating characteristics of the power converter and generate at least n control reference targets including at least one control reference target for each of the N phases of the power converter. The cascade control system includes at least one local model predictive control (MPC) controller, each of the at least one local MPC controller including a local processing unit and configured to receive the control reference targets of the n control reference targets and generate control signaling based on the control reference target to operate at least one switching element of the power switching elements corresponding to a phase of the local MPC controller using model predictive control (MPC).

[0225] Example 23: The method, apparatus, and / or non-transitory computer-readable medium of Example 22, wherein to generate the control signaling using the MPC, for each control period, each local MPC controller of the at least one local MPC controller is further configured to: determine a local electrical characteristic for one of the N phases associated with the local MPC controller; solve a cost function using the local electrical characteristic and a control reference target received by the local MPC controller; predict a future step of a control signal for controlling the phase of the N phases toward the control reference target; and generate the control signaling based on a first future step of the control signal.

[0226] Example 24: The method, apparatus, and / or non-transitory computer-readable medium of Example 22 or 23, wherein each local MPC controller is associated with a respective state estimator, and for each local MPC controller, the respective state estimator is configured to estimate a first local electrical characteristic of the local electrical characteristics in a phase associated with the local controller, the estimate being based on sampling of other local electrical characteristics of the local electrical characteristics in the phase associated with the local MPC controller, and each local MPC controller receives the first local electrical characteristic estimated by the state estimator associated with the local MPC controller to determine a local electrical characteristic in the N phases associated with the local MPC controller.

[0227] Example 25: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 22-24, wherein the at least one local MPC controller includes N local MPC controllers, each local MPC controller corresponding to a different phase of the N phases.

[0228] Example 26: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 22 to 25, wherein the central controller is configured to determine a rotating reference frame target, the rotating reference frame target including a zero sequence component target, the zero sequence component target based on a multiple of the N phase harmonic injection, and at least N control reference targets are generated based on the rotating reference frame target.

[0229] Example 27: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 22 to 26, wherein the central controller is further configured to determine direct axis (D-axis) and quadrature axis (Q-axis) components of the rotating reference frame target based on electrical operating characteristics in the rotating reference frame.

[0230] Example 28: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 22 to 27, wherein the central controller is further configured to determine a frequency of the AC power signal of the AC voltage section of the power converter based on a first characteristic of the electrical operating characteristics in the rotating reference coordinate system.

[0231] Example 29: To determine the direct axis (D-axis) component and the quadrature axis (Q-axis) component of the rotating reference frame target based on the electrical operating characteristics in the rotating reference frame, the central controller is configured to convert the current signal from the AC voltage section of the power converter into a direct axis (D-axis) current component and a quadrature axis (Q-axis) current component in the rotating reference frame, generate a D-axis voltage component as the D-axis component of the rotating reference frame target based on a comparison of the D-axis current component to a desired D-axis current, and generate a Q-axis voltage component as the Q-axis component of the rotating reference frame target based on a comparison of the Q-axis current component to a desired Q-axis current, and to generate N control reference targets in the stationary reference frame based on the rotating reference frame targets, the central controller is further configured to convert the D-axis voltage component, the Q-axis voltage component, and the zero sequence component target to the stationary reference frame.

[0232] Example 30: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 22-29, wherein the power switching element includes a high-side element and a low-side element connected to a node for each of the N phases of the power converter, and the node for each of the N phases of the power converter is coupled to a respective LC filter including an inductor coupled between the node and a filter node, and one or more of a first capacitor coupled between the filter node and a positive DC bus of the power converter or a second capacitor coupled between the filter node and a negative DC bus of the power converter.

[0233] Example 31: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 22 to 30, wherein the power converter is one or more of an AC-DC rectifier and a DC-AC inverter.

[0234] Example 32: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 22-31, wherein the AC voltage section of the power converter is coupled to an AC power grid or an AC motor.

[0235] Example 33: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 22 to 32, wherein to generate the control signaling for operating the at least one power switching element, each of the at least one local MPC controller is further configured to generate the control signaling using a variable frequency critical soft switching control signal.

[0236] Example 34: A power converter module further comprising: N power converter modules, N>1, each power converter module including: a positive direct current (DC) terminal and a negative DC terminal; a power switching element pair of power switching elements, the power switching element pair including a high side power switching element coupled to the positive DC terminal and a low side power switching element coupled to the negative DC terminal, the high side power switching element and the low side power switching element being coupled to each other at a midpoint node; an LC filter including a capacitor and an inductor, the inductor being coupled between the midpoint node and the capacitor, and the capacitor being coupled between the inductor and the negative DC terminal; and a filter for filtering the power switching element pair. 34. The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 22-33, comprising: a local MPC controller configured to drive one of the at least one local MPC controllers, wherein the power switching element pair is part of a power switching element associated with the local controller; a circuit board on which the positive and negative DC terminals, the power switching element pair, the LC filter, and the local MPC controller are located; the positive DC terminals of each of the N power converter modules are coupled to each other and the negative DC terminals of each of the one or more power converters are coupled to each other; and the central controller is located on a circuit board separate from the circuit board having the local controller.

[0237] Example 35: A method, apparatus, and / or non-transitory computer-readable medium comprising: receiving, by a central controller of a cascaded control system including at least one local model predictive control (MPC) controller cascaded with the central controller, electrical operating characteristics of a power converter, the electrical operating characteristics being characteristics of a non-isolated N-phase power converter, N≧1, having a DC voltage section and an N-phase AC voltage section, the power converter including power switching elements; generating, by the central controller, at least N control reference targets including at least one control reference target for each of the N phases of the power converter; receiving, by each of the at least one local MPC controller, a control reference target among the N control reference targets; and generating, by each of the at least one local MPC controller using model predictive control (MPC), control signaling based on the received control reference target to operate at least one switching element of the power switching elements corresponding to a phase of the local MPC controller.

[0238] Example 36: The method, apparatus, and / or non-transitory computer-readable medium of Example 35, further comprising one or more of the steps of rectifying, by the power converter, the AC power to DC power based on the control signaling, or converting, by the power converter, the DC power back to AC power based on the control signaling.

[0239] Example 37: The method, apparatus, and / or non-transitory computer-readable medium of Example 35 or 36, further comprising one or more of the steps of receiving AC power from an AC power grid by the AC section of the power converter, supplying AC power to an AC power grid by the AC section of the power converter, or supplying AC power to an AC motor by the AC section of the power converter.

[0240] Example 38: A method, apparatus, and / or non-transitory computer-readable medium for a non-isolated N-phase power converter system, where N>1, comprising a DC voltage section and an N-phase AC voltage section, and comprising, for each of the N phases, an LC filter including a switch-side inductor, a capacitor, or an output-side inductor, a power switching element, a sensor configured to sense a first electrical characteristic of a first component of the LC filter selected from the group of the switch-side inductor, the capacitor, or the output-side inductor and generate sensor data indicative of the first electrical characteristic, and a controller including an electronic processor, configured to receive the sensor data from the sensor, perform state estimation based on the sensor data to estimate a second electrical characteristic of a second component of the LC filter, different from the first component, and generate control signaling based on the second electrical characteristic to drive the power switching element.

[0241] Example 39: The method, apparatus, and / or non-transitory computer-readable medium of Example 38, wherein for each of the N phases, the sensor is further configured to sense a third electrical characteristic of a third component different from the first component and the second component of the LC filter, and the sensor data generated by the sensor further indicates the third electrical characteristic, and the state estimation for estimating the second electrical characteristic is based on the sensor data indicative of both the first electrical characteristic and the third electrical characteristic.

[0242] Example 40: The method, apparatus, and / or non-transitory computer-readable medium of Example 38 or 39, wherein for each of the N phases, the first electrical characteristic is a capacitor voltage, the second electrical characteristic is a switch-side inductor current, and the third electrical characteristic is an output-side inductor current.

[0243] Example 41: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 38 to 40, wherein for each of the N phases, the controller includes a model predictive control (MPC) controller configured to generate a duty cycle of the control signaling based on the second electrical characteristic using model predictive control (MPC).

[0244] Example 42: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 38 to 41, wherein for each of the N phases, the local controller is further configured to generate a switching frequency of the control signaling based on the second electrical characteristic to drive the power switching elements with a variable frequency critical soft-switching control signal.

[0245] Example 43: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 38 to 42, further comprising a cascade control system, the cascade control system comprising a central controller including a central electronic processor, the central controller configured to generate at least N control reference targets including at least one control reference target for each of the N phases, and a local controller for each of the N phases, the local controller for each of the N phases further configured to generate control signaling based on one control reference target of the N control reference targets received from the central controller.

[0246] Example 44: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 38 to 43, wherein the power converter system is a multi-phase power converter system with N=3.

[0247] Example 45: A method, apparatus, and / or non-transitory computer-readable medium using a non-isolated N-phase power converter, where N>=, comprising: sensing, by a sensor, a first electrical characteristic of a first component of an LC filter of the power converter to generate sensor data indicative of the first electrical characteristic, where the first component of the LC filter is selected from the group of a switch-side inductor, a capacitor, or an output-side inductor; receiving, by a local controller, the sensor data from the sensor; performing state estimation by the local controller based on the sensor data to estimate a second electrical characteristic of a second component of the LC filter, different from the first component; and generating, by the local controller, control signaling to drive a power switching element associated with the LC filter based on the second electrical characteristic.

[0248] Example 46: The method, apparatus, and / or non-transitory computer-readable medium of Example 45, further comprising sensing a third electrical characteristic of a third component, different from the first component and the second component of the LC filter, by a sensor, wherein sensor data generated by the sensor further indicates the third electrical characteristic, and wherein the state estimation for estimating the second electrical characteristic is based on the sensor data indicative of both the first electrical characteristic and the third electrical characteristic.

[0249] Example 47: The method, apparatus, and / or non-transitory computer-readable medium of Example 45 or 46, wherein the sensor includes a voltage sensor and a current sensor, the step of sensing the first electrical characteristic includes the step of sensing a voltage of a capacitor, the second electrical characteristic is a current of a switch-side inductor, and the step of sensing the third electrical characteristic includes the step of sensing a current of an output-side inductor.

[0250] Example 48: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 45 to 47, wherein generating the control signaling includes generating a duty cycle based on the second electrical characteristic using model predictive control.

[0251] Example 49: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 45 to 48, wherein generating the control signaling includes generating a switching frequency based on the second electrical characteristic to drive the power switching element with a variable frequency critical soft-switching control signal.

[0252] Example 50: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 45 to 49, further comprising: generating, by a central controller, at least N control reference targets, including at least one control reference target for each of the N phases; and receiving, by a local controller, a first control reference target of the N control reference targets, wherein generation of the control signaling is further based on the first control reference target.

[0253] Example 51: The power converter is a multi-phase power converter where N=3, the multi-phase power converter including N local converters including a local controller, a second local controller, and a third local controller, N sensors including a sensor, a second sensor corresponding to the second local controller, and a third sensor corresponding to the third local controller, and N LC filters including an LC filter, a second LC filter corresponding to a second phase of the N phases, and a third LC filter corresponding to a third phase of the N phases, the method including performing, by the second local controller, state estimation based on second sensor data from the second sensor to estimate electrical characteristics of components of the second LC filter. 51. The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 45-50, further comprising: generating, by the second local controller, a second control signaling for driving a power switching element corresponding to a second of the N phases based on the electrical characteristics of the components of the second LC filter; performing, by the third local controller, state estimation based on third sensor data from the third sensor to estimate the electrical characteristics of the components of the third LC filter; and generating, by the third local controller, a third control signaling for driving a power switching element corresponding to a third of the N phases based on the electrical characteristics of the components of the third LC filter.

[0254] Example 52: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 45 to 51, further comprising: generating, by a central controller, at least N control reference targets including at least one control reference target for each of the N phases; receiving, by a local controller, a first control reference target of the N control reference targets, where the generation of the control signaling is further based on the first control reference target; receiving, by a second local controller, a second control reference target of the N control reference targets, where the generation of the second control signaling is further based on the second control reference target; and receiving, by a third local controller, a third control reference target of the N control reference targets, where the generation of the third control signaling is further based on the third control reference target.

[0255] Example 53: One or more power converter modules, each power converter module comprising: 1. A method, apparatus, and / or non-transitory computer-readable medium comprising: a power switching element pair including a positive direct current (DC) terminal and a negative DC terminal, a high side power switching element coupled to the positive DC terminal, and a low side power switching element coupled to the negative DC terminal, wherein the high side power switching element and the low side power switching element are coupled to each other at a midpoint node; an LC filter coupled to the midpoint node, the positive DC terminal, and the negative DC terminal; and a local controller configured to receive a control reference target and generate control signaling to drive the power switching element pair based on the control reference target using model predictive control (MPC) and variable frequency soft switching.

[0256] Example 54: The method, apparatus, and / or non-transitory computer-readable medium of Example 53, wherein the local controller of each power converter module is further configured to use the MPC to generate duty cycle values ​​for the power switching element pairs and to generate switching frequencies for the power switching element pairs.

[0257] Example 55: The method, apparatus, and / or non-transitory computer-readable medium of Example 53 or 54, wherein to generate a duty cycle value using the MPC, the local controller is configured to: determine, at each control period, a local electrical characteristic in a phase of the AC associated with the local controller, solve a cost function using the local electrical characteristic and a control reference target received by the local controller, predict future steps of a control signal for controlling the N phases toward the control reference target, and generate control signaling based on a first of the future steps of the control signal.

[0258] Example 56: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 53 to 55, wherein to generate the switching frequency, the local controller is configured to calculate, in each control period, the switching frequency based on a duty cycle value and a local electrical characteristic of a phase of the AC associated with the local controller.

[0259] Example 57: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 53 to 56, wherein to generate the switching frequency, the local controller is configured to calculate the switching frequency using a continuous switching frequency function or a discrete switching frequency function in each control period.

[0260] Example 58: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 53 to 57, wherein the local controller of each power converter module is further configured to estimate, using a state estimator, a first local electrical characteristic of the local electrical characteristics in the AC phase associated with the local controller, the estimate being based on sampling of other local electrical characteristics of the local electrical characteristics in the AC phase associated with the local controller, generate, using an MPC, a duty cycle value for the pair of power switching elements based on the first local electrical characteristic and a control reference target, and generate a switching frequency for the pair of power switching elements based on the duty cycle value and the first local electrical characteristic.

[0261] Example 59: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 53 to 58, wherein the LC filter of each power converter module includes a switch-side inductor, an upper capacitor, and a lower capacitor, the switch-side inductor coupled between a midpoint node and a filter node, the upper capacitor coupled between the filter node and the positive DC terminal, and the lower capacitor coupled between the filter node and the negative DC terminal.

[0262] Example 60: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 53 to 59, further comprising a central controller including a processing unit, the central controller forming a cascade control system together with the local controllers, the central controller being configured to determine a rotating reference coordinate system target and generate a control reference target based on the rotating reference coordinate system target.

[0263] Example 61: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 53 to 60, wherein the one or more power converter modules include at least three power converter modules, and the central controller is further configured to generate control reference targets for each local controller of the at least three power converter modules based on the rotating reference coordinate system target.

[0264] Example 62: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 53 to 61, wherein the at least one power converter module is one or more of an AC-DC rectifier and a DC-AC inverter.

[0265] Example 63: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 53 to 62, wherein the at least one power converter module further includes an AC interface terminal coupled to an AC power grid or an AC motor.

[0266] Example 64. A method, apparatus, and / or non-transitory computer-readable medium comprising: receiving a control reference target by a local controller of a power converter module, the local controller being coupled to a power switching element pair including a high side power switching element coupled to a positive DC terminal of the power converter module and a low side power switching element coupled to a negative DC terminal of the power converter module, the high side power switching element and the low side power switching element being coupled to each other at a midpoint node, and an LC filter being coupled to the midpoint node, the positive DC terminal, and the negative DC terminal; generating, by the local controller, control signaling to drive the power switching element pair based on the control reference target using model predictive control (MPC) and variable frequency soft switching; and filtering, by the LC filter, a power signal provided to or received from the midpoint node.

[0267] Example 65: The method, apparatus, and / or non-transitory computer-readable medium of Example 64, further comprising: generating, by the local controller, a duty cycle value at the pair of power switching elements using the MPC; and generating, by the local controller, a switching frequency at the pair of power switching elements.

[0268] Example 66: The method, apparatus, and / or non-transitory computer-readable medium of Example 64 or 65, wherein the step of generating a duty cycle value using the MPC by the local controller includes the steps of: determining, at each control period, a local electrical characteristic in a phase of the AC associated with the local controller; solving a cost function using the local electrical characteristic and a control reference target received by the local controller to predict future steps of a control signal for controlling the N phases toward the control reference target; and generating control signaling based on a first of the future steps of the control signal.

[0269] Example 67: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 64 to 66, wherein generating a switching frequency by the local controller includes calculating, at each control period, the switching frequency based on a duty cycle value and a local electrical characteristic for a phase of the AC associated with the local controller.

[0270] Example 68: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 64 to 67, wherein generating the switching frequency by the local controller includes calculating the switching frequency using a continuous switching frequency function or a discrete switching frequency function in each control period.

[0271] Example 69: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 64 to 68, further comprising: estimating, by the local controller using a state estimator, a first local electrical characteristic of the local electrical characteristics in an AC phase associated with the local controller, the estimate being based on sampling of other local electrical characteristics of the local electrical characteristics in the AC phase associated with the local controller; generating, by the local controller using an MPC, a duty cycle value for the pair of power switching elements based on the first local electrical characteristic and a control reference target; and generating, by the local controller, a switching frequency for the pair of power switching elements based on the duty cycle value and the first local electrical characteristic.

[0272] Example 70: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 64 to 69, wherein the LC filter of each power converter module includes a switch-side inductor, an upper capacitor, and a lower capacitor, the switch-side inductor coupled between a midpoint node and a filter node, the upper capacitor coupled between the filter node and the positive DC terminal, and the lower capacitor coupled between the filter node and the negative DC terminal.

[0273] Example 71: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 64 to 70, further comprising: determining, by a central controller, a rotating reference coordinate system target, the central controller forming a cascade control system with the local controllers; and generating, by the central controller, a control reference target in the local controller based on the rotating reference coordinate system target.

[0274] Example 72: A first power converter module of a three-phase power converter, wherein the local controller is a first local controller, and the power converter module further includes a central controller, a second power converter module having a second local controller, and a third power converter module having a third local controller, the method including the steps of: determining, by the central controller, a rotating reference frame target, the central controller forming a cascaded control system with the first local controller, the second local controller, and the third local controller; generating, by the central controller, a control reference target in the first local controller based on the rotating reference frame target; 72. The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 64-71, further comprising: generating, by the central controller, a second control reference target in the second local controller based on the rotating reference frame target; generating, by the central controller, a third control reference target in the third local controller based on the rotating reference frame target; generating, by the second local controller, control signaling for driving the second pair of power switching elements based on the second control reference target using model predictive control (MPC) and variable frequency soft switching; and generating, by the third local controller, control signaling for driving the third pair of power switching elements based on the third control reference target using model predictive control (MPC) and variable frequency soft switching.

[0275] Example 73: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 64 to 72, further comprising one or more of: rectifying, by at least one power converter, the AC power to DC power based on the control signaling; or converting, by at least one power converter, the DC power back to AC power based on the control signaling.

[0276] Example 74: A method, apparatus, and / or non-transitory computer-readable medium comprising: a non-isolated N-phase power converter, where N>1 and having a DC voltage section, an N-phase AC voltage section; and a cascade control system for controlling the power converter, the cascade control system comprising: a central controller including a processing unit, the central controller configured to receive electrical operating characteristics of the power converter and generate at least N control reference targets including at least one control reference target for each of the N phases of the power converter; and a plurality of local model predictive control (MPC) controllers including at least two local MPC controllers for each phase of the N-phase power converter, each local MPC controller associated with a respective converter block including a pair of power switching elements and an LC filter in a phase corresponding to the local MPC controller, each of the local MPC controllers configured to receive one of the control reference targets for a phase associated with the local MPC controller and to generate control signaling based on a control reference signal for driving the pair of power switching elements associated with the local MPC controller using model predictive control (MPC).

[0277] Example 75: The method, apparatus, and / or non-transitory computer-readable medium of Example 74, wherein each LC filter includes a switch-side inductor and a lower-side capacitor, and each converter block associated with one of the local MPC controllers further includes a midpoint node connecting high-side and low-side elements of the power switching elements of the converter block, and a filter node, the switch-side inductor of the LC filter of the converter block is coupled between the midpoint node and the filter node, and the lower-side capacitor of the converter block is coupled between the filter node and a negative DC bus of the DC voltage section of the power converter.

[0278] Example 76: The method, apparatus, and / or non-transitory computer-readable medium of Example 74 or 75, wherein each LC filter further includes an upper capacitor, and each converter block associated with one of the local MPC controllers further includes an upper capacitor of the LC filter of the converter block coupled between a filter node of the converter block and a negative DC bus of the DC voltage section of the power converter.

[0279] Example 77: To generate the control signaling using MPC, at each control period, each local MPC controller of the plurality of local MPC controllers is configured to: determine a local electrical characteristic at a converter block associated with the local MPC controller; solve a cost function using the local electrical characteristic and a control reference target received by the local MPC controller; predict future steps of a control signal for controlling the N phases toward the control reference target; and generate the control signaling based on a first future step of the control signal.

[0280] Example 78: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 74 to 77, wherein each local MPC controller is associated with a respective state estimator, and for each local MPC controller, the respective state estimator is configured to estimate a first local electrical characteristic of the local electrical characteristics in a converter block associated with the local MPC controller, the estimate being based on sampling of other local electrical characteristics of the local electrical characteristics in the converter block associated with the local MPC controller, and each local MPC controller receives the first local electrical characteristic estimated by the state estimator associated with the local MPC controller to determine the local electrical characteristic in the converter block associated with the local MPC controller.

[0281] Example 79: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 74 to 78, wherein the central controller is configured to determine a rotating reference frame target, the rotating reference frame target including a zero sequence component target, the zero sequence component target based on a multiple of the Nth phase harmonic injection, and the at least N control reference targets are generated based on the rotating reference frame target.

[0282] Example 80: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 74 to 79, wherein the central controller is further configured to determine direct axis (D-axis) and quadrature axis (Q-axis) components of the rotating reference frame target based on electrical operating characteristics in the rotating reference frame.

[0283] Example 81: To determine the direct axis (D-axis) component and the quadrature axis (Q-axis) component of the rotating reference frame target based on the electrical operating characteristics in the rotating reference frame, the central controller is configured to convert the current signal from the AC voltage section of the power converter into a direct axis (D-axis) current component and a quadrature axis (Q-axis) current component in the rotating reference frame, generate a D-axis voltage component as the D-axis component of the rotating reference frame target based on a comparison of the D-axis current component to a desired D-axis current, and generate a Q-axis voltage component as the Q-axis component of the rotating reference frame target based on a comparison of the Q-axis current component to a desired Q-axis current, and to generate N control reference targets in the stationary reference frame based on the rotating reference frame targets, the central controller is further configured to convert the D-axis voltage component, the Q-axis voltage component, and the zero sequence component target to the stationary reference frame.

[0284] Example 82: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 74 to 81, wherein the power converter is one or more of an AC-DC rectifier and a DC-AC inverter.

[0285] Example 83: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 74 to 82, wherein the AC voltage section of the power converter is coupled to an AC power grid or an AC motor.

[0286] Example 84: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 74 to 83, wherein each local MPC controller is configured to generate the control signaling using a variable frequency critical soft switching control signal to generate control signaling for driving a pair of power switching elements associated with the local MPC controller.

[0287] Example 85: A power converter further comprising a plurality of power converter modules, each power converter module comprising: 85. The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 74 to 84, comprising: a positive direct current (DC) terminal and a negative DC terminal; a local MPC controller of the plurality of local MPC controllers; a converter block associated with the local MPC controller; and a circuit board having disposed thereon the positive and negative DC terminals, the local MPC controller, and the converter block associated with the local converter, wherein the positive DC terminals of each of the plurality of power converter modules are coupled to each other, and the negative DC terminals of the plurality of power converter modules are coupled to each other, and the central controller is disposed on a circuit board separate from the circuit board having the local MPC controller.

[0288] Example 86: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 74 to 85, wherein N=3 and the non-isolated N-phase power converter is a three-phase power converter.

[0289] Example 87: A method, apparatus, and / or non-transitory computer readable medium for voltage conversion using a non-isolated N-phase power converter, for N≧1, comprising receiving, by a central controller of a cascaded control system including a plurality of local model predictive control (MPC) controllers cascaded with the central controller, electrical operating characteristics of the power converter, the power converter including a DC voltage section and an N-phase AC voltage section, the plurality of local MPC controllers including at least two local MPC controllers for each phase of the N-phase power converter, each local MPC controller controlling a respective converter block including a pair of power switching elements and an LC filter in a phase corresponding to the local MPC controller. a step of generating, by a central controller, at least N control reference targets including at least one control reference target for each of N phases of the power converter, by each of the local MPC controllers receiving, by each of the local MPC controllers, a control reference target among the N control reference targets for a phase associated with the local MPC controller, and generating, by each of the local MPC controllers, control signaling based on the received control reference targets to drive a pair of power switching elements associated with the local MPC controller using model predictive control (MPC).

[0290] Example 88: The method, apparatus, and / or non-transitory computer-readable medium of Example 87, further comprising a step of filtering with each LC filter, each LC filter including a switch-side inductor and a lower-side capacitor, and each converter block associated with one of the local MPC controllers further including a midpoint node connecting high-side and low-side elements of the power switching elements of the converter block, and a filter node, the switch-side inductor of the LC filter of the converter block is coupled between the midpoint node and the filter node, and the lower-side capacitor of the converter block is coupled between the filter node and a negative DC bus of the DC voltage section of the power converter.

[0291] Example 89: The method, apparatus, and / or non-transitory computer-readable medium of Example 87 or 88, wherein each LC filter further includes an upper capacitor, and each converter block associated with one of the local MPC controllers further includes an upper capacitor of the LC filter of the converter block coupled between a filter node of the converter block and a negative DC bus of the DC voltage section of the power converter.

[0292] Example 90: To generate the control signaling using MPC, at each control period, each local MPC controller of the plurality of local MPC controllers is configured to: determine a local electrical characteristic at a converter block associated with the local MPC controller; solve a cost function using the local electrical characteristic and a control reference target received by the local MPC controller; predict future steps of a control signal for controlling the N phases toward the control reference target; and generate the control signaling based on a first future step of the control signal.

[0293] Example 91: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 87 to 90, wherein each local MPC controller is associated with a respective state estimator, and the method further includes estimating, by each state estimator, a first local electrical characteristic of the local electrical characteristics in the converter block associated with the local MPC controller associated with the state estimator, the estimate being based on sampling of other local electrical characteristics of the local electrical characteristics in the converter block associated with the local MPC controller, and the step of determining the local electrical characteristics in the converter block associated with each local MPC controller further includes receiving, by each local MPC controller, the first local electrical characteristic estimated by the state estimator associated with the local MPC controller.

[0294] Example 92: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 87 to 91, further comprising a step of determining, by a central controller, a rotating reference frame target, the rotating reference frame target including a zero sequence component target, the zero sequence component target being based on a multiple of an N phase harmonic injection, and wherein at least N control reference targets are generated based on the rotating reference frame target.

[0295] Example 93: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 87 to 82, wherein the central controller is further configured to determine direct axis (D-axis) and quadrature axis (Q-axis) components of the rotating reference frame target based on electrical operating characteristics in the rotating reference frame.

[0296] Example 94: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 87 to 93, wherein determining direct axis (D-axis) and quadrature axis (Q-axis) current components of the rotating reference frame target includes converting a current signal from the AC voltage section of the power converter into direct axis (D-axis) and quadrature axis (Q-axis) current components in the rotating reference frame, generating a D-axis voltage component as the D-axis component of the rotating reference frame target based on a comparison of the D-axis current component to a desired D-axis current, and generating a Q-axis voltage component as the Q-axis component of the rotating reference frame target based on a comparison of the Q-axis current component to the desired Q-axis current, and generating N control reference targets in the stationary reference frame based on the rotating reference frame targets includes converting the D-axis voltage component, the Q-axis voltage component, and the zero sequence component target to the stationary reference frame.

[0297] Example 95: The method, apparatus, and / or non-transitory computer-readable medium of any of Examples 87 to 94, wherein generating, by each local MPC controller, control signaling for driving a pair of power switching elements associated with the local MPC controller includes generating, by each local MPC controller, the control signaling using a variable frequency critical soft switching control signal.

Claims

1. An uninsulated N-phase power converter, where N≥1, having a DC voltage section and an N-phase AC voltage section and including power switching elements, and an uninsulated N-phase power converter; A control system configured to control the power converter, determining a rotating reference coordinate system target, the rotating reference coordinate system target including a zero-sequence component target, the zero-sequence component target being based on a multiple of the Nth-phase harmonic injection, generating N control reference targets in a stationary reference coordinate system, one for each of the N phases of the N-phase power converter, based on the rotating reference coordinate system target, generating a control signal for the power switching elements based on the N control reference targets, driving the power switching elements according to the control signal, A control system configured as such; A power converter system comprising the same.

2. The control system is a central controller including a processing unit, configured to determine the rotating reference coordinate system target and generate the N control reference targets, a central controller configured as such; at least one local controller, each of the at least one local controller including a local processing unit, and each of the at least one local controller receiving one of the N control reference targets, driving a part of the power switching elements associated with the local controller according to the control reference target, at least one local controller configured as such; The power converter system according to claim 1, which is a cascade control system comprising the same.

3. In order to drive a part of the power switching elements according to the control reference target, each of the at least one local controller performs model predictive control (MPC) to generate control signaling for a part of the power switching elements, The power converter system according to claim 2, configured as such.

4. The central controller receives at least one electrical operating characteristic from each of the at least one local controller, the electrical operating characteristic being in the stationary reference coordinate system, converts the at least one electrical operating characteristic to the rotating reference coordinate system, Based on the at least one electrical operating characteristic in the rotational reference coordinate system, determining a direct axis (D-axis) component and a quadrature axis (Q-axis) component of the rotational reference coordinate system target The power converter system according to claim 2, further configured as such. **Claim 5** The central controller Based on a first characteristic of the at least one electrical operating characteristic in the rotational reference coordinate system, determining the frequency of the AC power signal of the AC section of the power converter The power converter system according to claim 4, further configured as such. **Claim 6** To determine the direct axis (D-axis) component and the quadrature axis (Q-axis) component of the rotational reference coordinate system target based on the at least one electrical operating characteristic in the rotational reference coordinate system, the central controller Converts the current signal from the AC section of the power converter into a direct axis (D-axis) current component and a quadrature axis (Q-axis) current component in the rotational reference coordinate system Generates a D-axis voltage component as the D-axis component of the rotational reference coordinate system target based on a comparison between the D-axis current component and a desired D-axis current Generates a Q-axis voltage component as the Q-axis component of the rotational reference coordinate system target based on a comparison between the Q-axis current component and a desired Q-axis current Is configured as such To generate the N control reference targets in the stationary reference coordinate system based on the rotational reference coordinate system target, the central controller Converts the D-axis voltage component, the Q-axis voltage component, and the zero sequence component target into the stationary reference coordinate system The power converter system according to claim 4, further configured as such. **Claim 7** The power converter system according to claim 1, wherein the zero sequence component target includes the sum of a DC offset and a multiple of the Nth phase harmonic injection. **Claim 8** At least one of the DC offsets is half of the DC bus voltage of the DC voltage section of the power converter, or N is 3, and the multiple of the Nth phase harmonic injection is the third order of the fundamental frequency of the AC voltage section of the power converter The power converter system according to claim 7. **Claim 9** The multiple of the Nth phase harmonic injection A sine wave signal derived based on the Nth order of the fundamental frequency of the AC voltage section of the power converter, and A triangular signal derived based on an average value of a maximum value and a minimum value of the fundamental frequency of the AC voltage section of the power converter, and The power converter system according to claim 8, comprising:

10. The multiple of the Nth harmonic injection is N previous control reference targets generated by the control system in the stationary reference coordinate system based on a previously received rotating reference coordinate target, N voltage measurement values given by respective voltage sensors for each of the N phases of the power converter, or N voltage measurement values communicated by at least one local controller indicating respective voltages in each of the N phases of the power converter, The power converter system according to claim 8, which is a feedback signal calculated from at least one selected from the group of:

11. The power switching element includes a high-side element and a low-side element connected to an intermediate point node for each of the N phases of the power converter, The intermediate point node of each of the N phases of the power converter is coupled to a respective LC filter including an inductor coupled between the intermediate point node and a filter node, and a first capacitor coupled between the filter node and the positive DC bus of the power converter, or one or more of a second capacitor coupled between the filter node and the negative DC bus of the power converter, The power converter system according to claim 1.

12. The power converter is one or more of an AC-DC rectifier and a DC-AC inverter, the power converter system according to claim 1.

13. The AC section of the power converter is coupled to an AC power grid or an AC motor, the power converter system according to claim 1.

14. An LC filter including a switch-side inductor and a capacitor, and A sensor configured to detect a first electrical characteristic of a first component of the LC filter selected from the group of the switch-side inductor and the capacitor, and generate sensor data indicating the first electrical characteristic, Comprising: Each of the at least one local controller Receives sensor data from the sensor, Performs a state estimation based on the sensor data to estimate a second electrical characteristic of a second component different from the first component of the LC filter, further driving a part of the power switching element based on the second electrical characteristic; The power converter system according to claim 2, further configured as such.

15. In order to drive a part of the power switching element, each of the at least one local controller drives a part of the power switching element with a variable frequency critical soft switching control signal; The power converter system according to claim 2, further configured as such.

16. further comprising N power converter modules, where N>1, and each power converter module a positive DC terminal and a negative DC terminal; a pair of power switching elements including a high-side power switching element coupled to the positive DC terminal and a low-side power switching element coupled to the negative DC terminal, wherein the high-side power switching element and the low-side power switching element are coupled to each other at an intermediate point node; a pair of power switching elements; an LC filter including a capacitor and an inductor, wherein the inductor is coupled between the intermediate point node and the capacitor, and the capacitor is coupled between the inductor and the negative DC terminal; an LC filter; one of the at least one local controller configured to drive the pair of power switching elements, wherein the pair of power switching elements is a part of the power switching elements associated with the local controller; a local controller; a circuit board on which the positive and negative DC terminals, the pair of power switching elements, the LC filter, and the local controller are located; including; the positive DC terminals of each of the N power converter modules are coupled to each other, and the negative DC terminals of each of one or more of the power converters are coupled to each other; the central controller is located on a circuit board different from the circuit board having the local controller; The power converter system according to claim 2.

17. A method for converting a voltage, comprising: determining a rotating reference coordinate system target, wherein the rotating reference coordinate system target includes a zero-sequence component target, and the zero-sequence component target is the Nth phase based on a multiple of harmonic injection; a step; A step of generating N control reference targets in a stationary reference coordinate system based on the rotation reference coordinate system target, wherein one of the control reference targets is generated for each of the N phases of the non-insulated N-phase power converter, N≧1, and the power converter includes a DC voltage section, an N-phase AC voltage section, and power switching elements, the step; A step of driving the power switching elements of the power converter according to the N control reference targets; A method including the above.

18. By a cascade control system, A step of determining the rotation reference coordinate system target by a central controller; A step of generating the N control reference targets by the central controller; A step of receiving, by each of at least one local controller, one of the N control reference targets; A step of driving, by each of the at least one local controller, a part of the power switching elements according to the control reference target; The method according to claim 17, further including the above.

19. The step of driving, by each of the at least one local controller, a part of the power switching elements according to the control reference target is A step of implementing model predictive control (MPC) by each of the at least one local controller to generate control signaling for a part of the power switching elements, The method according to claim 18, including the above.

20. A step of receiving, by the central controller, at least one electrical operating characteristic from each of the at least one local controller, wherein the at least one electrical operating characteristic is within the stationary reference coordinate system, the step; A step of converting, by the central controller, the at least one electrical operating characteristic to the rotation reference coordinate system; A step of determining, by the central controller, a direct axis (D-axis) component and a quadrature axis (Q-axis) component of the rotation reference coordinate system target based on the at least one electrical operating characteristic in the rotation reference coordinate system; The method according to claim 18, further including the above.

21. The method according to claim 20, wherein the central controller is further configured to determine a frequency of an AC power signal in the AC section of the power converter based on a first characteristic of the at least one electrical operating characteristic in the rotational reference coordinate system by the central controller.

22. The step of determining the direct axis (D-axis) component and the quadrature axis (Q-axis) component of the rotational reference coordinate system target based on the at least one electrical operating characteristic in the rotational reference coordinate system includes: converting a current signal from the AC section of the power converter into a direct axis (D-axis) current component and a quadrature axis (Q-axis) current component in the rotational reference coordinate system; generating a D-axis voltage component as the D-axis component of the rotational reference coordinate system target based on a comparison between the D-axis current component and a desired D-axis current; generating a Q-axis voltage component as the Q-axis component of the rotational reference coordinate system target based on a comparison between the Q-axis current component and a desired Q-axis current; and The step of generating the N control reference targets in the stationary reference coordinate system based on the rotational reference coordinate system target includes: converting the D-axis voltage component, the Q-axis voltage component, and the zero sequence component target into the stationary reference coordinate system. The method according to claim 20.

23. The method according to claim 22, wherein the zero sequence component target includes a sum of a DC offset and a multiple of the Nth phase harmonic injection.

24. At least one of the DC offsets is half of a DC bus voltage of the DC voltage section of the power converter, or N is 3, and the multiple of the Nth phase harmonic injection is the third order of a fundamental frequency of the AC voltage section of the power converter. The method according to claim 23.

25. The multiple of the Nth phase harmonic injection is a sine wave signal derived based on the Nth order of a fundamental frequency of the AC voltage section of the power converter, or a triangular signal derived based on an average value of a maximum value and a minimum value of the fundamental frequency of the AC voltage section of the power converter. The method according to claim 24.

26. The multiple of the Nth phase harmonic injection is N previous control reference targets generated by the control system in the stationary reference coordinate system based on a previously received rotational reference coordinate system target. N voltage measurement values provided by respective voltage sensors for each of the N phases of the power converter, and N voltage measurement values communicated by at least one local controller indicating the respective voltages in each of the N phases of the power converter, The method according to claim 24, which is a feedback signal calculated from at least one selected from the group of **Claim 27** The power switching element includes a high-side element and a low-side element connected to a node for each of the N phases of the power converter, The node of each phase of the N phases of the power converter is coupled to a respective LC filter including an inductor coupled between the node and a filter node, and one or more of a first capacitor coupled between the filter node and the positive DC bus of the power converter or a second capacitor coupled between the filter node and the negative DC bus of the power converter. The method according to claim 17. **Claim 28** Rectifying AC power to DC power based on driving of the power switching elements of the power converter according to the N control reference targets by the power converter, or Inverting DC power to AC power based on driving of the power switching elements of the power converter according to the N control reference targets by the power converter, The method according to claim 17, further including one or more of **Claim 29** Receiving AC power from an AC power grid by the AC section of the power converter, Supplying AC power to the AC power grid by the AC section of the power converter, or Supplying AC power to an AC motor by the AC section of the power converter, The method according to claim 17, further including one or more of

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