Dual active bridge parameter estimation for control configuration

Abstract

The invention relates to dual active bridge parameter estimation for control configuration. Systems and methods for operating a dual active bridge (DAB) converter include a transformer flowing a current through the DAB converter; measuring the current; determining a leakage inductance of the transformer based on the measured current; and determining a control scheme for operating the DAB converter based on the leakage inductance of the transformer. In some embodiments, determining the leakage inductance includes determining a slot resistance of the transformer. In some embodiments, the control scheme includes a gain scheduling, zero voltage switching scheme, or both, where the control scheme is different from a nominal control scheme based on nominal leakage inductance and improves power conversion efficiency or accuracy of the output voltage compared to the nominal control scheme.

Description

[0001] introduction

[0002] This disclosure relates to systems and methods for determining parameters of a power converter. More specifically, this disclosure relates to control schemes for adjusting a power converter based on its characteristics. Summary of the Invention

[0003] A dual active bridge (DAB) converter is a power electronic device that can use a transformer as part of a DC-DC power conversion process. It can be useful to determine the transformer's leakage inductance or other electromagnetic characteristics and operate the DAB converter based on that determination.

[0004] In some implementations, the control circuitry of the DAB converter can determine the leakage inductance of the transformer based on measuring the current flowing through the transformer of the DAB converter. In some implementations, the control circuitry can operate the converter to determine the leakage inductance when no load is connected to the output of the DAB converter. In other implementations, the control circuitry can operate the DAB converter to transfer power to a load connected to the output of the converter, and simultaneously determine the leakage inductance. Based on the leakage inductance of the transformer, the control circuitry can determine and implement a corresponding control scheme. For example, the control circuitry can determine a specific zero-voltage switching scheme (e.g., to improve efficiency) or a specific gain dispatch (e.g., to improve dynamic performance, such as in response to changes in load characteristics) based on the leakage inductance.

[0005] According to an embodiment of this disclosure, a method for operating a dual active bridge (DAB) converter includes: allowing current to flow through a transformer of the DAB converter; measuring the current; determining the leakage inductance of the transformer based on the measured current; and determining a control scheme for operating the DAB converter based on the leakage inductance of the transformer.

[0006] In some implementations, determining the control scheme includes determining a zero-voltage switching scheme for the DAB converter, wherein the control scheme differs from a nominal control scheme based on the nominal leakage inductance of the transformer, and wherein the determined leakage inductance improves the power conversion efficiency of the DAB converter compared to the nominal control scheme when the determined leakage inductance deviates from the nominal leakage inductance.

[0007] In some implementations, determining the control scheme includes scheduling multiple gains of the DAB converter based on a determined leakage inductance, wherein the control scheme differs from a nominal control scheme based on the nominal leakage inductance of the transformer, and wherein the control scheme improves the accuracy of the multiple scheduled gains compared to the nominal control scheme when the determined leakage inductance deviates from the nominal leakage inductance.

[0008] In some implementations, the method also includes applying one of a plurality of gains based on the characteristics of the load receiving power from the DAB converter.

[0009] In some implementations, determining the control scheme includes determining multiple control schemes, each of which corresponds to a specific operating mode of the DAB converter.

[0010] In some implementations, determining the leakage inductance of a transformer includes: determining the tank resistance of the transformer based on measured current; and determining the leakage inductance based on the tank resistance.

[0011] In some implementations, the measured current includes a first measured waveform and a second measured waveform, wherein the first measured waveform is used to determine the tank circuit resistance and the second measured waveform is used to determine the leakage inductance.

[0012] In some embodiments, the transformer through which current flows through the DAB converter includes: a first branch controlling the bridge of the DAB converter based on a first triangular carrier waveform and a first DC modulation signal; a second branch controlling the bridge of the DAB converter based on a second triangular carrier waveform and a second DC modulation signal; and configuring a phase shift between the first and second triangular carrier waveforms such that the amplitude of the current flowing through the transformer is within a predetermined current range. In some embodiments, the predetermined current range is based on the transformer's saturation current range (e.g., to avoid transformer saturation).

[0013] In some embodiments, the method further includes configuring a first DC modulation signal and a second DC modulation signal such that the dead time of the first branch and the dead time of the second branch are within a predetermined range. In some embodiments, the predetermined range is based on achieving a ZVS condition. In other embodiments (e.g., operating outside of a ZVS condition, for example, to determine leakage inductance), the predetermined range is based on achieving desired losses across one or more switches.

[0014] In some embodiments, the transformer through which current flows through the DAB converter includes: a first branch controlling the bridge of the DAB converter based on a first triangular carrier waveform and a first sinusoidal modulation signal; a second branch controlling the bridge of the DAB converter based on a second triangular carrier waveform and a second sinusoidal modulation signal; and configuring the frequencies of the first and second triangular current waveforms such that the frequency of the current flowing through the transformer is within a predetermined range. In some embodiments, the predetermined range is based on the sampling rate of the control circuit, the saturation current range of the transformer, or a combination thereof.

[0015] In some embodiments, the method further includes configuring a first sinusoidal modulation signal and a second sinusoidal modulation signal such that the amplitude of the current flowing through the transformer is within a predetermined range. In some embodiments, the predetermined range is based on the transformer's saturation current range.

[0016] In some embodiments, the method further includes configuring a phase shift between the first triangular current waveform and the second triangular current waveform such that when the switches of the first branch and the second branch are switched, the amplitude of the current flowing through the transformer is within a predetermined current range. In some embodiments, the predetermined range is based on implementing ZVS in the switches to eliminate the effect of dead time on the bridge voltage.

[0017] In some implementations, the method includes configuring the secondary bridge of the DAB converter such that the voltage across the secondary bridge is zero when current flows through the transformer of the DAB converter.

[0018] In some implementations, measuring the current includes: low-pass filtering the current; and determining the root mean square value of the filtered current.

[0019] In some implementations, determining the leakage inductance of the transformer involves applying an expression that correlates the measured input power of the DAB converter with the measured output power of the DAB converter when current flows through the transformer of the DAB converter.

[0020] According to embodiments of this disclosure, a dual active bridge (DAB) converter includes processing circuitry configured to: allow current to flow through a transformer of the DAB converter; measure the current; determine the leakage inductance of the transformer based on the measured current; and determine a control scheme for operating the DAB converter based on the leakage inductance of the transformer. In some embodiments, a leakage inductance-based control scheme provides improved dynamic performance (e.g., reduced overshoot and undershoot of dynamic power output in response to changes in the load connected to the DAB converter) compared to a control scheme based on nominal leakage inductance (e.g., wider stability margin, or stricter compliance with operation within a constant stability margin).

[0021] In some implementations, the processing circuitry is configured to determine a control scheme for operating the DAB converter by determining a zero-voltage switching scheme for the DAB converter, wherein the control scheme differs from a nominal control scheme based on the nominal leakage inductance of the transformer, and the control scheme improves the power conversion efficiency of the DAB converter compared to the nominal control scheme when the determined leakage inductance deviates from the nominal leakage inductance.

[0022] In some implementations, the processing circuitry is configured to determine a control scheme for operating the DAB converter by scheduling multiple gains of the DAB converter based on a determined leakage inductance. This control scheme differs from a nominal control scheme based on the nominal leakage inductance of the transformer, and improves the accuracy of the multiple scheduled gains compared to the nominal control scheme when the determined leakage inductance deviates from the nominal leakage inductance. In some implementations, the improved dynamic performance is based on the increased accuracy of the multiple scheduled gains.

[0023] In some implementations, the processing circuitry is configured to determine the leakage inductance of the transformer by determining the tank circuit resistance of the transformer based on the measured current and by determining the leakage inductance based on the tank circuit resistance.

[0024] According to embodiments of this disclosure, a non-transitory computer-readable medium has non-transitory computer-readable instructions encoded thereon, which, when executed by a processor, cause the processor to: allow current to flow through a transformer of a dual active bridge (DAB) converter; measure the current; determine the leakage inductance of the transformer based on the measured current; and determine a control scheme for operating the DAB converter based on the leakage inductance of the transformer. Attached Figure Description

[0025] The above and other objects and advantages of this disclosure will become apparent from the following specific embodiments taken in conjunction with the accompanying drawings, wherein similar reference characters always refer to similar parts, and wherein:

[0026] Figure 1 An exemplary block diagram of an electric vehicle charging system according to some embodiments of the present disclosure is shown, the electric vehicle charging system including power electronics for providing power to a load and / or an energy storage system;

[0027] Figure 2 This is an illustrative block diagram showing additional details of some components of a power electronic device according to some embodiments of the present disclosure;

[0028] Figure 3 This is an exemplary circuit diagram of a first dual active bridge (DAB) converter according to some embodiments of the present disclosure;

[0029] Figure 4 This is an illustrative depiction of the current flowing through the transformer of a DAB converter according to some embodiments of this disclosure;

[0030] Figure 5 This is an illustrative depiction of signals during a first operating mode for determining the leakage inductance of the transformer of a DAB converter, according to some embodiments of this disclosure.

[0031] Figure 6 This is an illustrative depiction of signals during a second operating mode used to determine the leakage inductance of the transformer of the DAB converter, according to some embodiments of this disclosure.

[0032] Figure 7 This is an exemplary signal processing flowchart for determining the leakage inductance of the transformer of a DAB converter according to some embodiments of this disclosure;

[0033] Figure 8This is an exemplary flowchart of a first method for determining the leakage inductance of a DAB converter according to some embodiments of the present disclosure;

[0034] Figure 9 This is an exemplary circuit diagram of a second dual active bridge (DAB) converter according to some embodiments of the present disclosure;

[0035] Figure 10 This is an exemplary flowchart of a second method for determining the leakage inductance of a DAB converter according to some embodiments of the present disclosure;

[0036] Figure 11 This is an illustrative depiction of signals used to determine the leakage inductance of the transformer of a DAB converter during power conversion operation, according to some embodiments of this disclosure; and

[0037] Figure 12 This is an exemplary flowchart of a method for determining a control scheme for operating a DAB converter based on a determined leakage inductance, according to some embodiments of this disclosure. Detailed Implementation

[0038] The performance of a power supply system can vary based on the dynamic characteristics of its electrical or electromagnetic components. These dynamic characteristics can be determined in real time (or near real time) to modify the operating procedures of the power supply system (e.g., a system that provides tightly controlled output voltage to dynamic loads) and to meet constraints surrounding output voltage or output power specifications.

[0039] Many power systems (e.g., DC-DC power converters, including DAB converters) include transformers with leakage inductance and other electromagnetic characteristics. Dynamically operating a power converter based on the transformer's leakage inductance can be challenging, at least because leakage inductance varies from device to device, changes over time in response to field usage, and depends on the characteristics of components (which may also change over time) coupled (directly or indirectly) to the transformer.

[0040] Potential inaccuracies in characterizing the leakage inductance of a transformer can degrade the performance of a DAB converter (or any other suitable power converter including a transformer) (e.g., power conversion efficiency, ability to compensate for transient load characteristics, any other suitable performance characteristics, or any combination thereof). This document provides systems and methods for determining the leakage inductance of a transformer and operating a DAB converter based on the determined leakage inductance. In some embodiments, these systems and methods are configured to determine the leakage inductance automatically (e.g., without manual intervention, e.g., on a schedule, in response to one or more predetermined conditions, or in response to a local or remote command) and / or rapidly (e.g., within less than 1 minute or less than 1 second). In some embodiments, the leakage inductance is determined during normal power conversion operation of the DAB converter.

[0041] Based on the determined leakage inductance, the control circuitry modifies the operation of the DAB converter. For example, the control circuitry may retrieve gain scheduling (e.g., a protocol for setting a range of controller parameters for a possible operating range) from the DAB converter's memory based on the leakage inductance. In another example, the control circuitry may retrieve zero-voltage switching schemes (e.g., switching timing protocols for reducing switching losses during power conversion) from the DAB converter's memory in other ways or additionally based on the leakage inductance. In some implementations, the modified operation of the DAB converter is based on a modified scheme that adjusts the nominal operating scheme corresponding to the nominal leakage inductance (e.g., measured during commissioning of the DAB converter, or estimated based on empirical data and / or physical models) to correspond to the determined leakage inductance (or the deviation between the nominal and determined leakage inductance).

[0042] Therefore, as described above and further described in detail below, methods, systems, and computer-readable media are provided for determining the leakage inductance of the transformer of a DAB converter and for modifying the operation of the DAB converter based on the determined leakage inductance.

[0043] Figure 1An exemplary block diagram 100 of an electric vehicle charging system according to some embodiments of the present disclosure is depicted, the electric vehicle charging system including a DAB converter for providing power to a load and / or an energy storage system (ESS). Power is input to the system via a power grid 102 coupled to a power cabinet 104. The power cabinet 104 is coupled to a DC fast charging (DCFC) distributor 106. The power cabinet 104 ultimately delivers power to at least one of an electric vehicle 108 (specifically, a battery 109 therein) and / or an energy storage system (ESS) 110 via direct connection or through the distributor 106. The power cabinet 104 includes one or more power electronic modules (PEMs) 105, each power electronic module (PEM) including a DAB converter 114, a memory 111, and control circuitry 112, wherein the memory 111 may include instructions for operating the control circuitry 112 to control the DAB converter 114 according to the operations described above and further as further described below. In some embodiments, DAB converter 114 is electrically isolated from other components of block diagram 100 and is configured for bidirectional flow (e.g., DAB converter 114 can send power to or receive power from DCFC distributor 106 or ESS 110). Embodiments of this disclosure can serve either direction of the power flow through DAB converter 114. Additionally, PEM 105 includes an AC-to-DC converter 116 that can convert incoming AC power from the grid into a first DC power, which can then be converted into a second DC power (e.g., via DAB converter 114) for powering connected loads. In some embodiments, AC-to-DC converter 116 can convert incoming DC power (e.g., from electric vehicle 108 or ESS 110, via DAB converter 114) into AC power that can be supplied to the grid (e.g., to provide grid support) or to AC loads (e.g., to provide backup power, grid islanding, supplemental power, any other suitable AC power source, or any combination thereof).

[0044] Figure 2This is an illustrative block diagram showing additional details of some components of a power electronic device according to some embodiments of the present disclosure. Memory 111 may be an electronic storage device. As mentioned herein, the phrase "electronic storage device" or "storage device" may refer to any device for storing electronic data, computer software, or firmware, such as random access memory, read-only memory, solid-state devices, or any other suitable fixed or removable storage device and / or any combination thereof. Memory 111 may be used to store various types of instructions, rules, and / or other types of data. For example, memory 111 may include instructions on how to determine the leakage inductance of a transformer (e.g., transformer 218). In some embodiments, the instructions of memory 111 may include operating DAB converter 114 in one or more ways such that control circuitry 112 can determine the leakage inductance of transformer 218 (e.g., in conjunction with...). Figures 3 to 11 (The subject of this document is missing). Furthermore, memory 111 may include rules for determining the leakage inductance of the transformer (e.g., reference values ​​for calculating the leakage inductance, waveforms to be applied across the transformer, reference formulas for determining the leakage inductance based on measured characteristics, signal processing techniques for determining the leakage inductance from measured characteristics, specific characteristics to be measured to determine the leakage inductance, constraints on various operating parameters including saturation current and sampling rate, or any combination thereof). In some embodiments, control circuitry 112 executes instructions related to the application stored in memory 111 (e.g., to apply one or more waveform, measurement, and / or signal processing schemes to determine the leakage inductance of the transformer of DAB converter 114). Specifically, the application may command control circuitry 112 to perform functions discussed herein, including sending control signals to switch individual switches and / or branches of switches. In some embodiments, any action performed by control circuitry 112 may be based on instructions received from the application. In some embodiments, the application may be implemented as software or a set of executable instructions that can be stored in memory 111 and executed by control circuitry 112.

[0045] Memory 111 may store settings 202, instructions 204, and rules 206. Example types of settings 202 may include PEM output settings, DAB control settings (e.g., DAB switch switching settings), DAB switching schemes (e.g., for measuring the health of a transformer), duty cycle settings (e.g., for keeping the DAB converter's switch below a threshold temperature limit), delay settings (e.g., as may be associated with the state of the DAB converter), other types of settings, or any combination thereof. In some embodiments, settings 202 may be configured to vary based on a measured or determined leakage inductance. For example, settings 202 or rules 206 may include details on how to modify the nominal operating procedure of the DAB converter 114 (e.g., including gain scheduling and zero-voltage switching schemes) to account for the deviation between the nominal leakage inductance and the measured leakage inductance. Example types of Rule 206 include mappings for applying DAB control settings based on measured leakage inductance, PEM output settings, calculated constants (e.g., any one or more electromagnetic characteristics of the inductor, transformer, switch, transistor, capacitor, or other electronic device of DAB converter 114), overvoltage conditions, overcurrent conditions, negative current conditions, switching sequences, DAB models, DAB controls, buffer capacitance, other possible transient load dynamics, other types of information or data, or any combination thereof. In some embodiments, instruction 204 is executed by control circuitry 112 to implement steps of the various methods described herein (e.g., based on applicable settings 202 and / or Rule 206). In some embodiments, control circuitry 112 uses data stored in memory 111 to perform combined... Figures 3 to 11 The described operation.

[0046] DAB converter 114 includes a transformer 218 having a primary bridge winding and a secondary bridge winding (which has a leakage inductance that can be measured and / or determined (e.g., calculated) by control circuitry 112), a primary-side bridge 220, and a secondary-side bridge 222. The primary-side bridge 220 is coupled to the primary side of transformer 218 via an inductor 216, which may be a physical winding of transformer 218, a leakage inductance, or a combination thereof. The secondary-side bridge 222 is coupled to the secondary side of transformer 218. As used herein, the term "primary side" or "primary bridge" of a DAB converter (e.g., DAB converter 114) may refer to the portion of the DAB converter that appears on the left side of the transformer (e.g., transformer 218), and the term "secondary side" or "secondary bridge" of DAB converter 114 may refer to the portion of the DAB converter that appears on the right side of the transformer. It should be noted that the designation of the "primary" and "secondary" sides or bridges of the DAB converter is based on the assumption that input power is supplied to the left side of transformer 218 and output power is supplied from the right side of transformer 218. In some embodiments, input power may be supplied to the right side of transformer 218 (e.g., via electric vehicle 108, energy storage system 110, or electric vehicle 332), and output power may be supplied from the left side of transformer 218 (e.g., to power grid 102 or instead of V). in (The load connected in 302), in this case, the right side of transformer 218 can be the "primary side" and the left side of transformer 218 can be the "secondary side". As used herein, Vp and Vs refer to the voltage on the primary side and the voltage on the secondary side of transformer 218, respectively. DAB converter 114 also includes primary-side switches S1, S2, S3 and S4 on the primary side of DAB converter 114 and secondary-side switches S5, S6, S7 and S8 on the secondary side of DAB converter 114. As used herein, a "branch" of the DAB converter bridge refers to a pair of switches coupled in series (e.g., switches S1 and S2, S3 and S4, S5 and S6, or S7 and S8). Switches S1, S2, S3, S4, S5, S6, S7, and S8 can be any suitable type of electronic switch, such as a field-effect transistor (FET) based switch, which can be enabled (e.g., turned on / off, during which current is allowed to conduct between its source and drain terminals) or disabled (e.g., turned off / off, during which current is effectively prevented from conducting between its source and drain terminals) by changing the logic level of the control signal provided to its gate terminal, for example, from a logic high level to a logic low level.

[0047] In some embodiments, branches of the DAB converter 114 may switch (e.g., periodically open and close) in response to control signals from control circuitry 112, wherein such signals may correspond to the desired power output of PEM 105 or a desired scheme for determining the leakage inductance of transformer 218. These signals may include specific time delays to configure how one or more current waveforms conduct across the transformer, control power output, achieve other desired control effects, or any combination thereof. In some embodiments, switches S1-S8 may be based on wide bandgap (WBG) power semiconductors, such as gallium nitride (GaN) or silicon carbide (SiC) based semiconductors. In some embodiments, switches S1-S8 may include other types of metal-oxide-semiconductor field-effect transistors (MOSFETs). As shown, each switch in switches S1-S8 includes an anti-parallel diode. (The last sentence appears to be incomplete and possibly refers to a different implementation.) Figure 3 and Figure 9 As described, switches Q1-Q8 can respectively correspond to, as follows: Figure 2 The switches S1-S8 shown include switches Q1-Q8 that have the same connections to the control circuit 112, temperature sensor 224, and PEM 105 as the switches S1-S8.

[0048] In some implementations, temperature sensors 224-1, 224-2, 224-3, 224-4, 224-5, 224-6, 224-7, and 224-8 (collectively referred to as temperature sensors 224) are coupled to switches S1, S2, S3, S4, S5, S6, S7, and S8, respectively, and are configured to measure the temperature of these switches. Temperature sensors 224-1, 224-2, 224-3, 224-4, 224-5, 224-6, 224-7, and 224-8 output signals (Si, S ... TEMP (1) to S TEMP (8), collectively referred to as S TEMP (1:8)). In some implementations, data from one or more temperature sensors 224-1, 224-2, 224-3, 224-4, 224-5, 224-6, 224-7, and 224-8 can indicate voltage level and / or temperature changes occurring across switches S1-S8. For clarity, Figure 2 The output ports S of temperature sensors 224-1, 224-2, 224-3, 224-4, 224-5, 224-6, 224-7 and 224-8 are omitted. TEMP (1) to S TEMP (8) Temperature input port 211(S) of control circuit 112 TEMP(1:8)) complete signal path. Nevertheless, the output ports S of temperature sensors 224-1, 224-2, 224-3, 224-4, 224-5, 224-6, 224-7, and 224-8 TEMP (1) to S TEMP (8) In practice, the temperature input port 211(S) of the control circuit 112 is coupled to the signal input port 211(S) via a signal bus or other suitable corresponding signal path. TEMP (1:8)). In some embodiments, one or more temperature sensors in temperature sensor 224 may be omitted. For example, in some embodiments, a single temperature sensor may be provided for each branch or side of DAB converter 114. In some embodiments, the temperature signal may be used as feedback information for control circuitry 112 to determine whether the control scheme of DAB converter 114 (e.g., based on measured leakage inductance) meets output requirements, and the control scheme may be modified based on feedback signals indicating that certain output requirements are not met.

[0049] In some implementations, current sensor 229 is configured to sense the output current (i_OUT) of PEM 105 and output a signal to control circuitry 112 indicating the output current delivered to output power 130. The signal from current sensor 229 can be used to determine the control scheme of DAB converter 114 (e.g., how to switch or switch branches therein). For example, current sensor 229 may indicate the output power 130 of PEM 105, where the output power may be associated with a specific switching scheme of DAB converter 114. Similarly, current sensor 219 is configured to sense the output current (i_OUT). DC_OUT Current sensor 219 may be configured identically to current sensor 229, including features used by control circuitry 112 to determine the switching scheme of DAB converter 114. In some embodiments, current sensor 229 may correspond to current sensor 925. In some embodiments, voltage sensor 221 may be coupled in parallel to current sensor 219 to measure the output voltage (V) of PEM 105. DC_OUT Furthermore, the signal from voltage sensor 221 can also be used to determine the leakage inductance of transformer 218 of DAB converter 114.

[0050] In some embodiments, current sensor 226 is configured to sense the current across the secondary side of transformer 218 and output a signal indicating the secondary-side transformer current to control circuitry 112. In some embodiments, the signal from current sensor 226 (with or without a signal from current sensor 219) can be used to determine the leakage inductance of transformer 218 or the corresponding control scheme for DAB converter 114. In some embodiments, a voltage sensor may be coupled in parallel to current sensor 226 or located in another suitable position to measure the transformer voltage. In some embodiments, the voltage sensor 221, with or without a signal from it, can be used to determine the leakage inductance of transformer 218 or the corresponding control scheme for DAB converter 114.

[0051] In some embodiments, current sensor 225 is configured to sense the current across the primary side of transformer 218 and output a signal indicating the primary current to control circuitry 112. In some embodiments, the signal from current sensor 225 (with or without a signal from current sensor 219) can be used to determine the leakage inductance of transformer 218 or the corresponding control scheme for DAB converter 114. In some embodiments, a voltage sensor may be coupled in parallel to current sensor 225 or in another suitable location and can be used to determine the leakage inductance of transformer 218 or the corresponding control scheme for DAB converter 114. In some embodiments, voltage sensor 221 or any other voltage or current sensor can be used to determine the leakage inductance of transformer 218 or the corresponding control scheme for DAB converter 114. In some embodiments, current sensor 225 may correspond to current sensor 315.

[0052] The control circuit 112 includes a memory interface port 208 and a first input port 210 (V IN Probe Temperature input port 211, second input port 212 (V) OUT Probe The control circuit 112 is configured to transmit and receive instructions, settings, rules, and / or other types of data to and from the memory 111 via the memory interface port 208. For example, the control circuit 112 may be configured to implement a specific control scheme or switching scheme based on instructions from the memory 111 (e.g., for measuring signals indicating the characteristics of the transformer 218, or for delivering a specific output voltage distribution from the DAB converter 114 based on the characteristics of the transformer 218). The control circuit 112 is configured to sense the temperature of one or more of the switches S1-S8. The control circuit 112 is configured to sense the secondary-side output voltage (e.g., V0) via the input port 212. OUTProbe In some embodiments, the voltage from voltage input port 212 is measured to determine the leakage inductance of transformer 218. In some embodiments, the instructions 208 provided to control circuitry 112 are based on a desired scheme for determining the leakage inductance of transformer 218, determining one or more voltage signals recorded in DAB converter 114, one or more temperature sensors for monitoring DAB converter 114, system status indicators, any other suitable information, or any combination thereof.

[0053] Output port 214 includes primary switch control port S1 CTL S2 CTL S3 CTL and S4 CTL The control circuit 112 provides the corresponding switch control signals to the corresponding switch control ports S1, S2, S3 and S4 of the primary side switches. CTL S2 CTL S3 CTL and S4 CTL Output port 214 also includes secondary switch control port S5. CTL S6 CTL S7 CTL and S8 CTL The control circuit 112 provides the corresponding switch control signals to the corresponding switch control ports S5, S6, S7 and S8 of the secondary side switches, respectively. CTL S6 CTL S7 CTL and S8 CTL For clarity, Figure 2 The switch control port S1 of the control circuit 112 is omitted. CTL S2 CTL S3 CTL S4 CTL S5 CTL S6 CTL S7 CTL and S8 CTL S1 to DAB 114 CTL S2 CTL S3 CTL S4 CTL S5 CTL S6 CTL S7 CTL and S8 CTL The complete signal path. However, the switch control port S1 of control circuit 112 CTL S2 CTL S3 CTL S4 CTL S5 CTL S6CTL S7 CTL and S8 CTL In fact, it is coupled to S1 of DAB 114 via the corresponding signal path. CTL S2 CTL S3 CTL S4 CTL S5 CTL S6 CTL S7 CTL and S8 CTL In some implementations, the control circuit 112 is configured to transmit a control signal (e.g., the switching control signal S1 of the primary side bridge 220). CTL S2 CTL S3 CTL S4 CTL and / or the switching control signal S5 of the secondary side bridge 222 CTL S6 CTL S7 CTL and S8 CTL Control signals are provided according to a switching sequence to induce switching, causing current to flow through transformer 218 (e.g., to determine the leakage inductance of the transformer, to provide output power to the load, or both). In some embodiments, control circuitry 112 is configured to induce switching based on sending control signals (e.g., including holding the switch in the off state) provided according to one or more modified power operating modes (e.g., where a modified mode of DAB converter operation corresponds to the leakage inductance of transformer 218).

[0054] The output of DAB converter 114 is coupled to a load configured to receive output power 130. For example, the output power 130 can be used to charge either electric vehicle 108 or ESS 110. In response to the dynamic power requirements of the output power 130, control circuitry 112 can adjust the control or switching scheme of DAB converter 114 (e.g., gain scheduling and / or zero-voltage switching schemes) to deliver specific levels of dynamic power. For example, when the state of charge of electric vehicle 108 or ESS 110 is low (e.g., less than 5%, 10%, 20%, or any other suitable low state of charge), DAB converter 114 can provide more power (e.g., faster charging), and when the state of charge of electric vehicle 108 or ESS 110 is high (e.g., greater than 80%, 90%, 95%, or any other suitable high state of charge), DAB can provide less power (e.g., slower charging).

[0055] In some implementation schemes, different methods can be used. Figure 2 The types of switches and / or switch configurations shown (e.g., those with a location relative to...) Figure 2The switches shown herein are examples of switches with source and drain terminals at opposite locations, active-high switches enabled by a logic high gate voltage, active-low switches enabled by a logic low gate voltage, etc. The specific switches, configurations, and logic levels shown and described herein are provided as illustrative examples. The principles of this document apply similarly to other types of switches and / or switch configurations. The switches associated with the examples described herein are active-high switches that are closed (e.g., turned on) by a logic high gate voltage and opened (e.g., turned off) by a logic low gate voltage.

[0056] In some implementations, control circuitry 112 is configured to send a status signal 230 (e.g., indicating the leakage inductance of transformer 218). For example, control circuitry 112 may send a command to one or more recipients of communication circuitry (e.g., PEM 105) and status signal 230, indicating the leakage inductance of transformer 218.

[0057] Although PEM 105 is illustrated and described, it should be understood that DAB converter 114 can be used in any power system that processes direct current (DC) as input, output or intermediate power, such as to charge electric vehicle 108 or ESS110.

[0058] Figure 3 This is an exemplary depiction 300 of a dual active bridge (DAB) converter according to some embodiments of the present disclosure. In some embodiments, depiction 300 captures elements for determining the leakage inductance of transformer 317. In some embodiments, elements 304, 306, 308, 310, 320, 322, 324, and 326 may respectively correspond to ( Figure 2 The components S1, S2, S3, S4, S5, S6, S7, and S8. In some embodiments, windings 316 and 318 may correspond to the primary bridge winding and secondary bridge winding of transformer 218, respectively. In some embodiments, V IN 302 can correspond to the DC provided to DAB 114 IN Power. In some embodiments, the electric vehicle load 332 may correspond to battery 109, ESS110, or a combination thereof. In some embodiments, leakage inductance 314 may correspond to inductance 216, leakage resistance 312 may correspond to the resistance of winding 316 (and / or circuit path coupled to at least the top side of winding 316), current sensor 315 may correspond to current sensor 225, current sensor 325 may correspond to current sensor 219, and capacitor 328 and resistor 330 may respectively correspond to ( Figure 2 The components ESR and C2 are shown in the figure. on,pThis can refer to the resistance of the primary-side current path as current flows from source 302 to primary winding 316, the primary-side current path including one or more switches and wires coupled to one or more switches; R on,s It can refer to the resistance of the secondary-side current path when current flows from the secondary winding 318 to the electric vehicle load 332, the secondary-side current path including one or more switches and wires coupled to one or more switches.

[0059] A DAB converter (e.g., DAB converter 114) can transfer DC power from source 302 to electric vehicle load 332. In some embodiments, any one or more primary-side switches of primary-side switches 304, 306, 308, or 310 can be controlled (e.g., via control circuitry 112) to allow a specific current waveform to flow across primary winding 316. Control circuitry 112 can determine leakage inductance 314 based on the measured current waveform. Although leakage inductance 314 is shown as a discrete element, it should be noted that this inductance may not represent a winding-based inductor, but rather it may represent the non-zero leakage inductance of a transformer and / or other components of the circuit. Therefore, leakage inductance 314 may be based on one or more characteristics of transformer 317. Furthermore, leakage inductance may be attributable to the non-zero inductance of wires, capacitors, transformers, other discrete electronic devices, lumped circuit components, or any combination thereof.

[0060] In some implementations, when the leakage inductance 314 is measured and / or determined, the control circuit 112 may hold secondary-side switches 322 and 326 in the ON or OFF position (e.g., shorting the two terminals of the secondary-side bridge 318 together, shorting these terminals to ground, and / or making the voltage across the secondary-side bridge 318 equal to zero), and may hold secondary-side switches 320 and 324 in the OFF or OFF position (e.g., isolating the load 332 from the transformer 317).

[0061] Figure 4 This is an illustrative depiction of the current flowing through the transformer of a DAB converter according to some embodiments of this disclosure. As shown, discrete current distributions (e.g., time-dependent current signals associated with duty cycles and / or specific waveforms) may be driven through the DAB converter (e.g., DAB converters 114, 300, or 900) based on specific operating modes. Current distributions 402, 404, and 406 respectively illustrate current waveforms that may occur during low-power (e.g., less than 30% of maximum output power), medium-power (e.g., between 30% and 70% of maximum output power), and high-power (e.g., greater than 70% of maximum output power) operation. It should be noted that these current distributions and these operating modes may depend on the leakage inductance of the transformer.

[0062] In some embodiments, current distributions 402, 404, and 406 may differ from each other due to the gain scheduling and / or zero-voltage switching scheme of the DAB converter 114, which may depend on the expected output power or other transient characteristics (e.g., impedance or state of charge) of the load connected to the DAB converter 114. In some embodiments, the memory 111 includes multiple gain scheduling and / or zero-voltage switching schemes based on or derived from the leakage inductance (e.g., based on the deviation between the measured leakage inductance and the nominal leakage inductance).

[0063] As used herein, gain scheduling can refer to a timing scheme used to switch the DAB converter to deliver a desired power output. In some implementations, control circuitry 112 can improve the accuracy of DAB converter gain scheduling by implementing a modified control scheme based on a determined leakage inductance, compared to a control scheme based on the nominal transformer leakage inductance. Therefore, DAB converter 114 can deliver power to the load and improve the dynamic output voltage distribution in response to transient changes in the power delivered to the load while maintaining a target level of power conversion efficiency. Control circuitry 112 can incorporate instructions from memory 111 to deliver accurate gain scheduling across a target operating region (e.g., a range based on one or more input voltage levels and possible output voltage levels) and a range of possible leakage inductance values.

[0064] As used herein, zero-voltage switching (ZVS) scheduling refers to a timing scheme for switching the DAB converter when the voltage across the switch is zero (or close to zero). ZVS operation improves the power conversion efficiency of the DAB converter because less energy is lost during switching. ZVS operation similarly improves the thermal management of the DAB converter because less energy is dissipated as heat. In some embodiments, compared to a ZVS scheme based on nominal transformer leakage inductance, control circuitry 112 can improve the accuracy of a leakage inductance-based ZVS scheme by implementing a modified control scheme based on a determined leakage inductance. Therefore, DAB converter 114 is able to deliver power to the load with less power loss and equipment heat generation. Instructions incorporated into memory 111 of control circuitry 112 can deliver an accurate ZVS scheme across a range of target output power conditions and possible leakage inductance values.

[0065] It should be noted that, Figure 4 And other places (e.g., including) Figures 5 to 6All waveforms are merely illustrative of specific operating conditions. Without departing from the scope of this disclosure, control circuitry 112 may allow similar waveforms to flow through any part of the DAB converter. For example, these waveforms may be modified to have one or more parameters (e.g., frequency, amplitude, dead time, or other suitable parameters) within a predetermined range. As another example, these waveforms may be modified based on the leakage inductance of the transformer (e.g., where the leakage inductance can be determined according to the methods and systems described herein).

[0066] Figure 5 This is an illustrative depiction of DAB converter signals during a first operating mode used to determine the leakage inductance of the transformer of a DAB converter (e.g., DAB converter 300) according to some embodiments of the present disclosure. In some embodiments, control circuitry 112 controls a first branch (e.g., switches 304 and 306) of the bridge (e.g., the primary bridge) of the DAB converter based on a first triangular carrier waveform 502 and a first DC modulation signal 504. As used herein, the modulation signal may refer to a signal used as a reference, against which another signal is compared to determine the state of the switch, as further described below. In some embodiments, control circuitry 112 controls a second branch (e.g., switches 308 and 310) of the bridge of the DAB converter based on a second triangular carrier waveform 512 and a second DC modulation signal 514. In some embodiments, control circuitry 112 implements switch switching at least in part based on DC modulation signals 504 and 514 to drive a switch having a specific DC magnitude (e.g., I0). dc The current (e.g., the filtered transformer current 530) flows through the transformer (e.g., where I...) dc This is the average value of the filtered transformer current, 530. Figure 5 As shown in the diagram (between waveforms 502 and 512), control circuitry 112 can configure a specific phase shift (e.g., α) between these two waveforms. p This allows the switch to be switched according to a specific phase shift, and when switching the switch of the first branch and the switch of the second branch, the amplitude of the current flowing through the transformer (e.g., transformer current 520 or filtered transformer current 530) is within a predetermined current range. In some embodiments, the control circuit 112 configures modulation signals 504 and 514 such that the dead time of the first branch (e.g., the period during which no switch is turned on) and the dead time of the second branch are within a predetermined time range.

[0067] In some embodiments, control circuit 112 switches the switches of the first branch and the second branch according to the following scheme: When the level of the first DC modulation signal 504 exceeds the level of the first triangular carrier waveform 502, the top switch of the first branch (e.g., switch 304) can be turned on or closed. The top switch of the first branch can be otherwise turned off or open. When the level of the second DC modulation signal 514 exceeds the level of the second triangular carrier waveform 502, the top switch of the second branch (e.g., switch 306) can be turned on or closed. The top switch of the second branch can be otherwise turned off or open. Control circuit 112 holds the bottom switch of the first branch (e.g., switch 306) and the bottom switch of the second branch (e.g., switch 310) in positions complementary to the top switches of the first and second branches, respectively (e.g., when one switch is on, the other is off).

[0068] In response to control circuitry 112 controlling the primary-side branch of the DAB converter based on waveforms 502, 504, 512, and 514, current 520 flows through a transformer (e.g., transformer 218 or 317). Control circuitry 112 may apply a filter (e.g., a low-pass filter) to current 520 to record a filtered transformer current 530. In some embodiments, the filtered transformer current is a DC signal with a certain magnitude that control circuitry 112 uses to estimate transformer resistance 312 (e.g., by combining at least some of the formulas (1)-(21) and (A1)-(A2), as described below). In some embodiments, applying voltage waveform 540 across the bridge of the DAB converter (e.g., primary bridge 316) causes transformer current 520 to flow through the transformer of the DAB converter.

[0069] In some implementations, the filtered transformer current is 530 (and / or Figure 5 Any other waveform shown may represent the first waveform. The first waveform may correspond to a first control scheme for measuring the leakage inductance of the DAB converter. The first waveform and the first control scheme may be used to determine the tank circuit resistance of the transformer (e.g., represented by transformer resistance 312). In some embodiments, the tank circuit resistance is applied in a subsequent process for determining the leakage inductance of the transformer (e.g., in combination with at least some of the formulas (1)-(21) and (A1)-(A2), as described below).

[0070] Figure 6This is an illustrative depiction of DAB converter signals during a second operating mode (e.g., corresponding to a second waveform) used to determine the leakage inductance of the transformer of the DAB converter, according to some embodiments of this disclosure. In some embodiments, control circuitry 112 controls a first branch (e.g., switches 304 and 306) of the bridge (e.g., the primary bridge) of the DAB converter based on a first triangular carrier waveform 602 and a first sinusoidal modulation signal 604. In some embodiments, control circuitry 112 controls a second branch (e.g., switches 308 and 310) of the bridge of the DAB converter based on a second triangular carrier waveform 612 and a second sinusoidal modulation signal 614. Control circuitry 112 can be configured with frequencies of the first triangular carrier waveform 602 and the second triangular carrier waveform 604 such that the frequency of the current flowing through the transformer (e.g., transformer current 620 or filtered transformer current 630) is within a predetermined range (e.g., below the Nyquist sampling rate). Control circuit 112 can be configured with a first sinusoidal modulation signal 604 and a second sinusoidal modulation signal 614, such that the amplitude of the current flowing through the transformer (e.g., transformer current 620 or filtered transformer current 630) is within a predetermined range (e.g., below the saturation current limit, while still being measurable with a suitable signal-to-noise ratio (SNR)). As shown, control circuit 112 can be configured with a phase shift (e.g., α) between the first triangular current waveform 602 and the second triangular current waveform 612. p This ensures that when switching the first branch switch and the second branch switch, the amplitude of the current flowing through the transformer (e.g., transformer current 620 or filtered transformer current 630) is within a predetermined current range. In some embodiments, the control circuit 112 implements the switch switching at least in part based on sinusoidal modulation signals 604 and 614 to drive a circuit with a specific frequency (e.g., f). inj ) and specific AC amplitude (e.g., I inj The current (e.g., the filtered transformer current 630) flows through the transformer (e.g., where I...) inj This is the peak amplitude of the filtered transformer current 630 (e.g., the peak amplitude measured relative to the average or zero value of the current), such as... Figure 6 (As shown).

[0071] In some embodiments, control circuit 112 causes the switches of the first branch and the second branch to switch according to the following scheme: When the level of the first sinusoidal modulation signal 604 exceeds the level of the first triangular carrier waveform 602, the top switch of the first branch (e.g., switch 304) can be turned on or closed. The top switch of the first branch can be otherwise turned off or open. When the level of the second sinusoidal modulation signal 614 exceeds the level of the second triangular carrier waveform 612, the top switch of the second branch (e.g., switch 306) can be turned on or closed. The top switch of the second branch can be otherwise turned off or open. Control circuit 112 holds the bottom switches of the first branch (e.g., switch 306) and the second branch (e.g., switch 310) in positions complementary to the top switches of the first and second branches, respectively (e.g., when one switch is on, the other is off).

[0072] In response to control circuitry 112 controlling the primary-side branch of the DAB converter based on waveforms 602, 604, 612, and 614, current 620 flows through a transformer (e.g., transformer 218 or 317). Control circuitry 112 may apply a filter (e.g., a low-pass filter) to current 620 to record a filtered transformer current 630. In some embodiments, the filtered transformer current is an AC signal with a certain magnitude that control circuitry 112 uses to estimate transformer leakage inductance 314 (e.g., by combining at least some of the formulas (1)-(21) and (A1)-(A2), as described below). In some embodiments, applying voltage waveform 640 across the bridge of the DAB converter (e.g., primary bridge 316) causes transformer current 620 to flow through the transformer of the DAB converter.

[0073] In some implementations, the filtered transformer current is 630 (and / or Figure 6 Any other waveform shown can represent the second waveform (e.g., referring to the first waveform is...). Figure 5 (One of those waveforms shown). The second waveform may correspond to a second control scheme used to measure the leakage inductance of the DAB converter. The second waveform and the second control scheme can be used to determine the leakage inductance of the transformer (e.g., based at least on the tank circuit resistance, for example, as determined using the first waveform and the first control scheme).

[0074] In some implementations, after a control scheme for determining the tank circuit resistance (e.g., a first mode), control circuit 112 applies a control scheme for determining the leakage inductance (e.g., a second mode). Therefore, triangular carrier waveforms 602 and 612 can be the third and fourth triangular carrier waveforms, respectively (referencing triangular carrier waveforms 502 and 512, which are the first and second triangular carrier waveforms). For example, control circuit 112 can be driven in conjunction with determining the transformer cross-line resistance (e.g., in conjunction with operations 821 and 831, or the first mode). Figure 5 The first and second waveforms, and the control circuit 112 can then be combined with determining the transformer inductance (e.g., combining operations 822 and 832, or a second mode) to drive Figure 6 The third and fourth waveforms.

[0075] Figure 7 This is an exemplary signal processing flowchart for determining the leakage inductance of the transformer of a DAB converter according to some embodiments of this disclosure. t 701, as shown in signal processing flow 700.

[0076] At 702, control circuit 112 configures the DAB converter to transfer the measured current i t 701 is coupled to a low-pass filter (LPF) (e.g., a digital or analog low-pass filter). In some implementations, the LPF 702 is based on an attenuation factor F. g (For example, it can be based on frequency f in the calculation performed by control circuit 112) inj The frequency-dependent attenuation applied is used to attenuate the measured current i. t The value of 701. In some implementations, the LPF at 702 modifies the transformer current 520 to the filtered transformer current 530, or the LPF at 702 modifies the transformer current 620 to the filtered transformer current 630.

[0077] At 704, control circuitry 112 couples the output of LPF 702 to zero-order hold (ZOH) 704. In some embodiments, ZOH 704 includes sampling the signal using a digital-to-analog (DAC) converter. In some embodiments, the DAC converter samples the signal at a rate less than 2*f. inj The signal is sampled at a time interval equal to the reciprocal of the Nyquist frequency (e.g., at a frequency higher than the Nyquist frequency).

[0078] At 706, control circuitry 112 couples the output of ZOH 704 to the root mean square (RMS) 706 calculator. In some implementations, the RMS 706 provides the measured RMS current it,rms meas 708. The control circuit 112 can use the measured RMS current i t,rms meas 708. To determine or calculate tank circuit resistance, for example, use the following formula:

[0079]

[0080] Where R est It is the tank circuit resistance, m dc T is the length of the duty cycle of the bridge voltage waveform (e.g., voltage waveform 540) applied during resistance estimation mode 821. d It is the dead time of the controlled switch, f sw It is the switching frequency of the bridge switch (e.g., controlled by control circuit 112 based on a triangular carrier and a corresponding modulation signal), V in It is the input voltage (e.g., source voltage 302), and i t,rms meas As described above. In some implementations, as determining R est As part of the control circuit 112, non-zero dead time is induced in one or more switches of the DAB converter. For example, this dead time may be used to reduce the effective duty cycle of the bridge voltage based on non-ZVS operation and the corresponding non-zero DC component of the transformer current.

[0081] In some implementations, the control circuit 112 may use the following formula to determine the leakage inductance based on the tank resistance:

[0082]

[0083] Where L est It is leakage inductance, ω inj It is 2*π*f inj And the other terms of formula A2 are as described above.

[0084] Figure 8 This is an exemplary flowchart of a first method for determining the leakage inductance of a DAB converter (e.g., DAB converter 114 or 300) according to some embodiments of this disclosure. It should be noted that this method can provide greater than 99% accuracy in determining the leakage inductance of the DAB converter across a wide range of possible variations associated with leakage inductance and tank circuit resistance. In some embodiments, this accuracy is maintained across a wide tolerance range (e.g., at or above 20%) relative to the accuracy used to determine the leakage inductance value and relative to values ​​associated with various parameters of the DAB converter 114 (or values ​​associated with its components).

[0085] In some implementations, a control circuit (e.g., control circuit 112, for example, when executing...)Figure 8 When using the method, the following formulas (1)-(20) are used (for example, together with formulas (A1) and (A2) listed above) to determine the leakage inductance of the transformer of the DAB converter:

[0086]

[0087] I soft =I hf -I inj (4)

[0088]

[0089] I max2 =I hf +I inj (6)

[0090] I max2 <0.9I sat (7)

[0091] I soft ≥I ZVS (8)

[0092]

[0093] I inj >20 I sense,min (10)

[0094] m res >m pwm,min ,m ac = (# of the quantization step in the sine curve) * m res (11)

[0095]

[0096] I dc +I hf =I max1 (13)

[0097] m dc >T d f sw (14)

[0098] I dc >I sense,min (15)

[0099] I max1 <0.9I sat (16)

[0100]

[0101] Where I inj It is the magnitude of the AC current injected during the leakage inductance estimation mode (e.g., in f). inj The transformer current (630) is scaled by the factor of the low-pass filter attenuation gain. hf It is the peak value of the transformer current without low-frequency injection (e.g., transformer current 520 or 620), D p It is the duty cycle of the primary bridge voltage, I ZVS I is the minimum current required for ZVS (or soft switching, e.g., a switch close to ZVS condition) operation of the bridge switch. sat It is the saturation current of the transformer (e.g., transformer 218 or 317), I sense,min It is the minimum current resolution of the transformer current sensor (e.g., current sensor 315), L nom It is the nominal leakage inductance of the transformer, m ac It is the peak amplitude (e.g., measured relative to the average or zero value) of the bridge voltage waveform (e.g., voltage waveform 640) applied during inductance estimation mode 822. pwm,min It is the minimum duty cycle that can be implemented on a microprocessor based on the PWM clock frequency specification, I soft It is the minimum current available to discharge the FET capacitor under the combined effect of the injected AC current and the carrier frequency current, and the other terms of equations (1)-(20) are as described above (e.g., in combination with equations (A1) or (A2) and / or Figure 7 In the leakage inductance estimation mode, formula (8) can be applied (e.g., by control circuitry) to eliminate the effect of dead time on the applied bridge voltage by achieving ZVS at the moment of switching.

[0102] In some embodiments, control circuit 112 may perform method 800 by accessing at least some of the formulas (1)-(20) and formulas (A1) and (A2) and by calculating the outputs of these formulas. In some embodiments, control circuit 112 may perform method 800 by accessing values ​​in memory 111 (or any component thereof) that can be used to apply or determine parameter values ​​used in or calculated from formulas (1)-(20). Control circuit 112 may otherwise or additionally perform method 800 by accessing values ​​in memory 111 (or any component thereof) that can be used to retrieve or determine a control scheme (e.g., a switching scheme, e.g., for the primary bridge of the DAB converter) that causes a desired current (e.g., a value used for measuring the current in formulas (1)-(20)) to flow through the transformer of the DAB converter.

[0103] Measurement design 810 may include control circuitry 112 configured to operate the DAB converter to determine the leakage inductance of the DAB converter's transformer. Measurement design 810 may include parameters for configuring the current (e.g., before allowing the current to flow) through the transformer of the DAB converter.

[0104] At 811, control circuit 112 selects (e.g., determines, for example, retrieves from memory and / or calculates) m ac and ω inj The value satisfies formulas (9)-(11). Based on 811, at 812, control circuit 112 selects D. p To satisfy formulas (7)-(8). Based on 812, at 813, control circuit 112 selects m dc To satisfy formulas (14)-(16). Note that formulas (1)-(6) may be used by control circuit 112 in operation at 811, 812, 813 or any combination thereof. Note that satisfying these formulas may be based on characteristics of the DAB converter (e.g., transformer saturation current, low-pass filter attenuation, sampling rate, SNR associated with the sensor, any other suitable characteristic of PEM 105 or any combination thereof).

[0105] Measurement record 820 may include control circuitry 112 measuring (e.g., in conjunction with measurement design 810, e.g., via control circuitry 112) the current that causes the transformer to flow through the DAB converter. For example, control circuitry 112 may cause current to flow (e.g., according to a first scheme or tank resistance estimation mode, or according to a second scheme or leakage inductance estimation mode), and then measure the current.

[0106] At 821, prior to 822, control circuitry 112 operates the DAB converter in a high-frequency (HF) cross-line resistance estimation mode (e.g., a mode corresponding to the first scheme or tank circuit resistance estimation mode). As indicated by the arrows in flowchart 800, operation at 821 may be based on a value selected at 813. In some embodiments, the resistance estimation mode at 821 may include… Figure 5 Current distribution and / or Figure 7 The signal processing flow.

[0107] At 822, control circuitry 112 operates the DAB converter in an inductance estimation mode (e.g., a mode corresponding to the second scheme or leakage inductance estimation mode). As indicated by the arrows in flowchart 800, operation at 822 may be based on a value selected at 812. In some embodiments, the inductance estimation mode at 822 may include… Figure 6 Current distribution and / or Figure 7 The signal processing flow.

[0108] Measurement evaluation 830 may include control circuitry 112 to determine the transformer's leakage inductance based on measured current (e.g., as measured during measurement recording 820). Measurement evaluation 830 may include evaluation Figure 5 and Figure 6 One or more current distributions are shown (e.g., to calculate the resistance and leakage inductance of a transformer).

[0109] At point 831, control circuit 112 can determine the measured current i. t,rms meas (for example, i) t,rms meas 708, for example, based on such Figure 7 The signal processing method shown is used, and the leakage resistance R is calculated using formula (A1) based on the measured current. lkg est (For example, it can correspond to the tank circuit resistance, such as R) t 312 or R est At 832, the control circuit 112 can utilize a leakage resistor R. lkg est (As determined at 831) to evaluate formula (A2). At 833, control circuit 112 can determine the leakage inductance L. lkg est (For example, it can correspond to leakage inductance, such as L) t 314 or L est ) equals the output calculated from formula (A2).

[0110] Power conversion 840 may include control circuitry 112 to operate the DAB converter in one or more power conversion modes (e.g., to power the load of electric vehicle 332 based on an input from source voltage 302). At 841, control circuitry 112 may be based on leakage inductance (e.g., based on L...). lkg est To determine the control scheme used to operate the DAB converter.

[0111] In some implementations, determining the control scheme at 841 includes determining a ZVS scheme for the DAB converter (e.g., a mapping of switching times based on a possible range of transformer leakage inductance values). In some implementations, the ZVS scheme at 841 differs from a nominal ZVS scheme based on the transformer's nominal leakage inductance, and the scheme at 841 improves the power conversion efficiency of the DAB converter compared to the nominal ZVS scheme when the determined leakage inductance deviates from the nominal leakage inductance.

[0112] In some implementations, determining the control scheme at 841 includes scheduling one or more controller gains of the DAB converter based on a determined leakage inductance (e.g., a mapping of gains based on a possible range of transformer leakage inductance values). In some implementations, the gain scheduling scheme at 841 differs from a nominal gain scheduling scheme based on the nominal leakage inductance of the transformer, and the scheme at 841 improves the accuracy of multiple scheduled gains to improve transient response compared to the nominal gain scheduling scheme when the determined leakage inductance deviates from the nominal leakage inductance.

[0113] In some embodiments, determining the control scheme at 841 includes applying one of one or more gains (e.g., selecting mapped cells, rows, columns, or sub-regions) based on the characteristics of the load (e.g., electric vehicle 108 or energy storage system 110) receiving power from the DAB converter. In some embodiments, the load characteristic is impedance (which may be a dynamic impedance that can be recorded in real time). In some embodiments, the load characteristic is state of charge.

[0114] In some implementations, determining the control scheme at 841 includes determining a plurality of control schemes, each of which corresponds to a specific operating mode of the DAB converter (e.g., Figure 4 One of the power modes, or any other suitable power delivery mode of the DAB converter.

[0115] Figure 9 This is an exemplary circuit diagram of a second dual active bridge (DAB) converter according to some embodiments of the present disclosure. In some embodiments, the second DAB converter 900 corresponds to the first DAB converter 300. In some embodiments, Figure 9 All numbered elements that begin with "9" and end with two digits correspond to Figure 3 The corresponding numbered elements begin with "3" and end with the same two digits. Note that... Figure 3 In comparison, Figure 9 Some components were added or omitted because some components only exist when combined. Figure 9 The method described or in combination Figure 3 The methods described use this information. It should be noted that including or omitting such elements in only one DAB converter does not imply the presence or absence of these elements in another DAB converter.

[0116] like Figure 9 As shown, the output current (I0) can be recorded based on the power delivered to the load (e.g., the load selectively connected to the DAB converter using relay 934) (e.g., using current sensor 925). Also as Figure 9As shown, the output voltage (V0) across capacitor 928 can be recorded (e.g., using voltage sensor 221), and this output voltage is coupled to the load when relay 934 is closed. Note that the electric vehicle load 332 may correspond to internal resistance 935 and battery voltage 936.

[0117] Figure 10 This is an exemplary flowchart of a second method (e.g., performed by control circuitry 112) for determining the leakage inductance of a DAB converter according to some embodiments of this disclosure. In some embodiments, determining the leakage inductance of the transformer includes applying an expression that correlates the measured input power of the DAB converter with the measured output power of the DAB converter when current flows through the transformer of the DAB converter. In some embodiments, reference is made to... Figure 9 The annotation elements and signals are used to execute the second method 1000 (including the expression used at 1002).

[0118] At 1002, control circuit 112 determines an expression relating the measured input power output of the DAB converter to the measured output power of the DAB converter based on the leakage inductance of the transformer of the DAB converter. In some embodiments, this expression relates to a specific power conversion mode of the DAB converter (e.g., Figure 4 The input and output power (one of the modes shown, or any other suitable power conversion mode). For example, many possible expressions at 1002 can correspond to many possible operating conditions of the DAB converter, including operation in single-phase shift (SPS), dual-phase shift (DPS), three-phase shift (TPS), or extended phase shift (EPS) modes.

[0119] An exemplary expression is given in formula (21) (for example, it will be used in conjunction with 1002):

[0120]

[0121] Where L t It is the leakage inductance of the DAB transformer, V o It is the output voltage (e.g., such as...) Figure 9 As indicated (defined), φ is the phase shift between the primary and secondary bridge voltages (e.g., the voltages appearing across windings 916 and 918, respectively), N is the turns ratio between the primary and secondary bridges (e.g., the turns ratio between windings 916 and 918), and P... meas It is the measured input or output power of the DAB converter (e.g., V). o *I o or V in *I in ), and f * swIt is the switching frequency (e.g., associated with at least one switch of the primary or secondary bridge of the DAB converter).

[0122] In some implementations, solving formula (21) depends on measuring terms of formula (21) by the duty cycle of the primary bridge and the duty cycle of the secondary bridge of the DAB converter. For example, solving formula (21) may include integrating the power driven by one or more bridges across the bridges of the DAB converter during one or more corresponding duty cycles.

[0123] It should be noted that method 1000 can be implemented using all items that can be measured during normal power conversion operation of the DAB converter. Therefore, control circuitry 112 can execute method 1000, dynamically determine the leakage inductance of the DAB converter's transformer, and optionally modify the DAB converter's control scheme based on the leakage inductance, all while simultaneously providing output power.

[0124] At 1006, control circuit 112 measures the input power or output power (or both) of the DAB converter during power conversion operation. As mentioned above, the input and / or output power can be used in conjunction with the calculation of leakage inductance using formula (21).

[0125] At 1008, control circuit 112 applies an expression (e.g., formula (21)) and determines the leakage inductance of the transformer by evaluating the expression. In some embodiments, method 1000 further includes (e.g., in the process corresponding to power conversion 840) control circuit 112 determining and implementing a control scheme for the DAB converter based on the leakage inductance.

[0126] Figure 11 This is an illustrative depiction of a DAB converter signal used to determine the leakage inductance of the transformer of the DAB converter during power conversion operation, according to some embodiments of the present disclosure. Figure 11 The primary bridge voltage 1101, secondary bridge voltage 1102, and transformer current 1103 are shown. In some embodiments, the output current I01104 is recorded at an exemplary moment 1104 (e.g., when the primary bridge voltage transitions from low to high). meas In some implementation schemes, such as Figure 11 As shown, the switching time T * sw / 2 (for example, f) * sw Half of the reciprocal (for example, as used to determine L) t The time interval 1105 is given by the time interval between the primary bridge voltage transitioning from low to high. In some implementations, such as... Figure 11 As shown, the phase shift φ (e.g., as used to determine L)t The time interval 1106 is given by the time interval between the primary bridge voltage changing from low to high and the primary bridge voltage changing from high to low.

[0127] Figure 12 This is an exemplary flowchart of a method 1200 for determining a control scheme for operating a DAB converter based on a determined leakage inductance, according to some embodiments of this disclosure. In some embodiments, Figure 12 The operation of the DAB converter 114 is performed by the control circuit 112 (e.g., based on data stored in the memory 111).

[0128] At 1202, control circuitry 112 allows current to flow through a transformer (e.g., transformer 218 or 317) or a DAB converter. In some embodiments, operation at 1202 may correspond to at least a portion of measurement design 810 (e.g., to select parameters for the current) and measurement recording 820 (e.g., allowing current to flow through the transformer may occur in HF cross-line resistance estimation mode 821 and inductance estimation mode 822). In some embodiments, allowing current flow may include... Figure 5 and Figure 6 The waveform is generated. In some embodiments, the operation at 1202 may correspond to the operation at 1004 (e.g., control circuit 112 may perform method 1200 during power conversion operation).

[0129] At 1204, control circuit 112 measures current (e.g., i t,rms meas In some embodiments, measuring the current includes measuring one or both of the filtered transformer currents 530 and 630. In some embodiments, measuring the current includes implementing... Figure 7 The signal processing flowchart is shown. In some implementations, measuring current includes recording... Figure 11 The waveform and / or parameters (e.g., at least recording time intervals 1105 and / or 1106). In some embodiments, the operation at 1204 may correspond to at least a portion of the measurement recording 820 (e.g., measuring the current flowing through the transformer may occur in HF cross-line resistance estimation mode 821 and inductance estimation mode 822). In some embodiments, the operation at 1204 may correspond to at least a portion of the operation at 1006 (e.g., measuring input power or output power may include measuring current).

[0130] At 1206, control circuit 112 determines the leakage inductance of the transformer (e.g., L) based on the measured current. estOr leakage inductance 314). In some embodiments, determining the leakage inductance includes applying formulas (A1) and (A2) and at least a portion of formulas (1)-(20). In some embodiments, the operation at 1206 may correspond to the measurement evaluation 830 (e.g., the operation at 831, 832, and 833). In some embodiments, determining the leakage inductance is based on determining the leakage resistance (e.g., R). est In some implementations, the operation at position 1206 may correspond to the operation at position 1008.

[0131] At 1208, control circuitry 112 determines a control scheme for operating the DAB converter based on the transformer's leakage inductance. In some embodiments, operation at 1208 may correspond to power conversion 840 (e.g., operation at 841). In some embodiments, the control scheme includes at least one of gain scheduling or ZVS scheme. In some embodiments, the control scheme is based on a nominal control scheme (e.g., modified relative to a nominal control scheme), wherein the nominal control scheme is based on a nominal leakage inductance, and the amount of modification between the control scheme and the nominal control scheme is based on the deviation between the leakage inductance determined at 1206 and the nominal leakage inductance.

[0132] Therefore, it has been shown that systems and methods for determining the leakage inductance of the transformer of a DAB converter and for operating the DAB converter based on the determined leakage inductance have been provided.

[0133] It should be noted that control circuit 112 can allow current with DC offset (e.g., as in Equations (1)-(20)) to flow across the bridge of the DAB converter, and can cause switching of the bridge switches under non-ZVS conditions (e.g., in tank resistance estimation mode). The corresponding losses occurring across one or more of these switches can be evaluated by control circuit 112 to calculate the DC voltage across the transformer (e.g., in Equations (12) and (A1)).

[0134] It should be noted that control circuit 112 allows sinusoidal current to flow across the transformer at a frequency that does not saturate the transformer. However, low frequencies may introduce SNR limitations or other challenges when calculating the magnitude of the applied voltage. Therefore, control circuit 112 may introduce a specific phase shift (e.g., between the first and second triangular carrier waveforms, as mentioned above) that enables ZVS switching (e.g., when operating in leakage inductance estimation mode) while driving a sufficiently small current amplitude to prevent peak current from flowing across the transformer (e.g., because such peaks could saturate the transformer).

[0135] The above process is intended to be illustrative and not restrictive. Those skilled in the art will appreciate that the steps of the process described herein can be omitted, modified, combined, and / or rearranged, and any additional steps can be performed without departing from the scope of the invention.

[0136] The foregoing description is merely illustrative of the principles of this disclosure, and various modifications can be made by those skilled in the art without departing from the scope of this disclosure. The above embodiments are presented for illustrative purposes and not for limitation. This disclosure may also take many forms other than those expressly described herein. Therefore, it should be emphasized that this disclosure is not limited to the methods, systems, and apparatus expressly disclosed, but is intended to include variations and modifications thereof within the spirit of the appended claims.

Claims

1. A method for operating a dual active bridge (DAB) converter, the method comprising: The transformer that allows current to flow through the DAB converter; Measure the current; The leakage inductance of the transformer is determined based on the measured current; as well as The control scheme for operating the DAB converter is determined based on the leakage inductance of the transformer.

2. The method according to claim 1, wherein: Determining the control scheme includes determining a zero-voltage switching scheme for the DAB converter; and The control scheme: Unlike the nominal control scheme based on the nominal leakage inductance of the transformer; and When the determined leakage inductance deviates from the nominal leakage inductance, the power conversion efficiency of the DAB converter is improved compared to the nominal control scheme.

3. The method according to claim 1, wherein: The control scheme is determined by scheduling multiple gains of the DAB converter based on the determined leakage inductance; and The control scheme: Unlike the nominal control scheme based on the nominal leakage inductance of the transformer; and when the determined leakage inductance deviates from the nominal leakage inductance, the accuracy of multiple scheduled gains is improved compared to the nominal control scheme.

4. The method according to claim 3, further comprising: One of the plurality of gains is applied based on the characteristics of the load receiving power from the DAB converter.

5. The method of claim 1, wherein determining the control scheme comprises determining a plurality of control schemes, each of the plurality of control schemes corresponding to a corresponding operating mode of the DAB converter.

6. The method of claim 1, wherein determining the leakage inductance of the transformer includes based on the measured current: Determine the tank circuit resistance of the transformer; and The leakage inductance is determined based on the tank circuit resistance.

7. The method according to claim 6, wherein: The measured current includes the waveform of the first measurement and the waveform of the second measurement; The waveform measured in the first measurement is used to determine the tank circuit resistance; and The waveform of the second measurement is used to determine the leakage inductance.

8. The method of claim 7, wherein causing the current to flow through the transformer of the DAB converter comprises: The first branch of the bridge of the DAB converter is controlled based on the first triangular carrier waveform and the first DC modulation signal. The second branch of the bridge of the DAB converter is controlled based on the second triangular carrier waveform and the second DC modulation signal; and Configure the phase shift between the first triangular carrier waveform and the second triangular carrier waveform such that when the switch of the first branch and the switch of the second branch are switched, the amplitude of the current flowing through the transformer is within a predetermined current range.

9. The method according to claim 8, further comprising: Configure the first DC modulation signal and the second DC modulation signal such that the dead time of the first branch and the dead time of the second branch are within a predetermined range.

10. The method of claim 7, wherein causing the current to flow through the transformer of the DAB converter comprises: The first branch of the bridge of the DAB converter is controlled based on the first triangular carrier waveform and the first sinusoidal modulation signal. The second branch of the bridge of the DAB converter is controlled based on the second triangular carrier waveform and the second sine modulation signal. as well as Configure the frequencies of the first triangular current waveform and the second triangular current waveform such that the frequency of the current flowing through the transformer is within a predetermined range.

11. The method according to claim 10, further comprising: Configure the first sinusoidal modulation signal and the second sinusoidal modulation signal such that the amplitude of the current flowing through the transformer is within a predetermined range.

12. The method according to claim 10, further comprising: Configure the phase shift between the first triangular current waveform and the second triangular current waveform so that when the switch of the first branch and the switch of the second branch are switched, the amplitude of the current flowing through the transformer is within a predetermined current range.

13. The method of claim 1, further comprising configuring the secondary bridge of the DAB converter such that when the current flows through the transformer of the DAB converter, the voltage across the secondary bridge is zero.

14. The method of claim 1, wherein measuring the current comprises: The current is low-pass filtered; as well as Determine the root mean square value of the filtered current.

15. The method of claim 1, wherein determining the leakage inductance of the transformer comprises applying an expression that correlates a measured input power of the DAB converter with a measured output power of the DAB converter when the current flows through the transformer of the DAB converter.

16. A dual active bridge (DAB) converter, the dual active bridge (DAB) converter including processing circuitry configured to: The transformer that allows current to flow through the DAB converter; Measure the current; The leakage inductance of the transformer is determined based on the measured current; and The control scheme for operating the DAB converter is determined based on the leakage inductance of the transformer.

17. The DAB converter of claim 16, wherein the processing circuitry is configured to determine the control scheme for operating the DAB converter by determining a zero-voltage switching scheme for the DAB converter, wherein the control scheme: Unlike the nominal control scheme based on the nominal leakage inductance of the transformer; and When the determined leakage inductance deviates from the nominal leakage inductance, the power conversion efficiency of the DAB converter is improved compared with the nominal control scheme.

18. The DAB converter of claim 16, wherein the processing circuitry is configured to determine the control scheme for operating the DAB converter by scheduling a plurality of gains of the DAB converter based on the determined leakage inductance, wherein the control scheme: Unlike the nominal control scheme based on the nominal leakage inductance of the transformer; and When the determined leakage inductance deviates from the nominal leakage inductance, the accuracy of the plurality of scheduled gains is improved compared to the nominal control scheme.

19. The DAB converter of claim 17, wherein the processing circuitry is configured to determine the leakage inductance of the transformer based on the measured current: Determine the tank circuit resistance of the transformer; and The leakage inductance is determined based on the tank circuit resistance.

20. A non-transitory computer-readable medium having non-transitory computer-readable instructions encoded thereon, the non-transitory computer-readable instructions causing the processor, when executed by a processor, to: The transformer that allows current to flow through the dual active bridge (DAB) converter; Measure the current; The leakage inductance of the transformer is determined based on the measured current; and The control scheme for operating the DAB converter is determined based on the leakage inductance of the transformer.

Images