General transient dc offset suppression method for dual active bridge converter under bidirectional power flow

Abstract

The application discloses a general transient DC bias suppression method of a dual active bridge converter under bidirectional power flow, and comprises the following steps: generating asynchronous carrier waves when the dual active bridge DC converter is stably operated; adopting a certain modulation and control strategy, performing closed-loop operation in each switching cycle, generating primary side inner phase ratio D1, secondary side inner phase ratio D2 and outer phase ratio D f ; according to the positive and negative relationship between the outer phase ratio of the current switching cycle and the previous switching cycle, selecting different working modes to generate asynchronously updated modulation waves; according to the selected working mode, determining the lead and lag relationship of the modulation wave, comparing the modulation wave with the carrier wave to generate the driving signal of the power switch of the dual active bridge converter. The application can solve the problem that the existing transient DC bias suppression method is only applicable to a specific power flow direction or a specific modulation strategy, realize the transient DC bias suppression under bidirectional power flow, and ensure the safe operation of the dual active bridge converter.

Description

Technical Field

[0001] The present invention belongs to the field of direct current conversion technology in the field of power electronics technology, and particularly relates to a universal transient direct current bias suppression method under bidirectional power flow of a dual active bridge converter. Background Art

[0002] Dual Active Bridge (DAB) converters have been widely used due to their symmetrical topology, wide voltage conversion gain range, high power density, electrical isolation, and easy implementation of zero-voltage switching (ZVS). DAB converters utilize various modulation strategies to improve efficiency, optimize return power, and reduce current stress, including single-phase-shift (SPS) modulation, extended-phase-shift (EPS) modulation, dual-phase-shift (DPS) modulation, and triple-phase-shift (TPS) modulation.

[0003] In DAB converters, sudden changes in load, power transfer direction, or voltage can cause a sudden change in the shift phase update. This can lead to unequal positive and negative volt-second products across the power transfer inductor, generating transient DC bias currents. This transient DC bias current increases current stress on the power switches and can easily lead to saturation of the inductor and transformer core, potentially damaging them. If no measures are taken to mitigate the DC bias, the line impedance will eventually cause the DC bias to decrease to zero, and the leakage current will stabilize. The duration of this process is related to the line impedance; higher line impedance shortens the transient. However, overcurrent issues persist, and the generation of DC bias cannot be eliminated at its source. To mitigate the various effects of DC bias on DAB converters, a modulation strategy must be implemented to adjust the power supply when it changes.

[0004] Existing methods for suppressing transient DC bias are only applicable to specific modulation schemes and are difficult to extend to TPS modulation, which features an optimal operating mode with ZVS and low conduction losses. Furthermore, traditional transient DC bias suppression strategies primarily focus on unidirectional power flow conditions and cannot guarantee rapid power reverse operation of DAB converters. For example, Chinese patent application publication number CN11663123A, "DC Bias Suppression Method, Apparatus, and Medium for Dual Active Bridge DC Converters," proposes distributing the drive signals for the switching tubes of a dual active bridge DC converter by comparing an asynchronous carrier with a modulated wave, thereby eliminating the inductive current bias and excitation current bias generated by transient processes. However, this method is only applicable to transient DC bias suppression during unidirectional power conversion; in the article “Novel Phase-Shift Method for Fast Power Reversal With TransientZero Voltage Switching in a Bidirectional Dual Active Bridge DC–DC Converter” published in IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS in 2021, a transient DC bias suppression method for bidirectional power conversion based on SPS modulation was proposed, which can achieve soft switching while realizing bidirectional power conversion. However, this method can only be used for specific SPS modulation and is not universal and portable. In the article “A Simple DC-Offset Eliminating Method of the Series-Inductance Current for the DAB DC–DC Converter” published in IEEE TRANSACTIONS ON POWER ELECTRONICS in 2023, a decoupling method between the modulation method and the DC bias suppression method was proposed, which is applicable to all phase-shift modulation methods. DC bias suppression method, but does not consider the DC bias problem during power reverse mutation. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide a universal transient DC bias suppression method under bidirectional power flow in a dual active bridge converter, so as to solve the problem that existing transient DC bias suppression methods are only applicable to specific power flow directions or specific modulation strategies. The present invention generates a driving signal for a power switch by comparing an asynchronous carrier with an asynchronously updated modulation wave, and achieves transient DC bias suppression under bidirectional power flow by changing the lead-lag relationship between the primary and secondary side modulation waves, thereby ensuring the safe operation of the dual active bridge converter.

[0006] In order to achieve the above object, the application provides a general transient DC bias suppression method for bidirectional power flow of a dual active bridge converter, comprising the following steps:

[0007] S1, asynchronous carriers are generated when the dual active bridge converter is stably running, and the asynchronous carriers comprise sawtooth carrier T L1 of bridge arm L1, sawtooth carrier T L2 of bridge arm L2, sawtooth carrier T L3 of bridge arm L3, and sawtooth carrier T L4 of bridge arm L4.

[0008] S2, a certain modulation strategy and control strategy are adopted to generate phase-shifted ratios through closed-loop operation in each switching cycle, and the modulation strategy comprises single phase-shift modulation, extended phase-shift modulation, double phase-shift modulation and triple phase-shift modulation, and the phase-shifted ratios comprise primary side inner phase-shift ratio D1, secondary side inner phase-shift ratio D2 and outer phase-shift ratio D f .

[0009] S3, according to the positive and negative relationship between the outer phase-shift ratio of the current switching cycle and the outer phase-shift ratio of the previous switching cycle, different working modes are selected to generate asynchronously updated modulation waves, and the working modes comprise working mode 1 and working mode 2, and the modulation waves comprise modulation wave C A1 and C B1 of bridge arm L1, modulation wave C A2 and C B2 of bridge arm L2, modulation wave C A3 and C B3 of bridge arm L3, and modulation wave C A4 and C B4 of bridge arm L4.

[0010] S4, according to the selected working mode, the lead and lag relationship of the modulation wave is determined, the modulation wave is compared with the carrier wave to generate the driving signal of the power switch of the dual active bridge converter, and the suppression of the transient DC bias is realized.

[0011] Further preferably, in S1, the phases of carrier T L1 and carrier T L2 are the same, the phases of carrier T L3 and carrier T L4 are the same, and the phases of carrier T L3 , T L4 lag behind the phases of carrier T L1 , T L2 by 180°.

[0012] Further preferably, in S2, when the single phase-shift modulation is adopted, D1=D2=0; when the extended phase-shift modulation is adopted, D1=0, D2≠0 or D1≠0, D2=0; when the double phase-shift modulation is adopted, D1=D2; when the triple phase-shift modulation is adopted, D1≠0 and D2≠0.

[0013] Further preferably, in S3, the working mode selection specifically comprises:

[0014] When the phase shift ratio of the previous switching cycle is positive and the phase shift ratio of the current switching cycle is positive, no working mode switching is performed, and working mode 1 is selected;

[0015] When the phase shift ratio of the previous switching cycle is negative and the phase shift ratio of the current switching cycle is negative, no working mode switching is performed, and working mode 2 is selected;

[0016] When the phase shift ratio of the previous switching cycle is positive and the phase shift ratio of the current switching cycle is negative, the working mode is switched from working mode 1 to working mode 2;

[0017] When the phase shift ratio of the previous switching cycle is negative and the phase shift ratio of the current switching cycle is positive, the working mode is switched from working mode 2 to working mode 1.

[0018] Further preferably, the modulation wave calculation expression of each bridge arm is:

[0019]

[0020] wherein y and z are constants, and the values of y and z are both 0.5 after calculation, and the calculation formula of x is:

[0021] x=V1 / (V1+nV2) Formula (2)

[0022] wherein V1 is the primary side DC voltage of the dual active bridge converter, V2 is the secondary side DC voltage of the dual active bridge converter, and n is the ratio of the primary side and secondary side turns of the high-frequency transformer of the dual active bridge converter.

[0023] Further preferably, in S4, each modulation wave is updated when the carrier is equal to zero, and the updating method specifically comprises:

[0024] When working mode 1 is selected, the modulation wave C A3 of bridge arm L3 is updated first, and then the modulation wave C B3 of bridge arm L4 is updated, and then the modulation wave C A4 of bridge arm L1 is updated, and then the modulation wave C B4 of bridge arm L2 is updated, and the updating time is different by half a switching cycle. A1 B1 A2 B2 ​​​​

[0025] When selecting working mode 2, first update the modulation wave C of bridge arm L1 at the same time A1 with C B1 , the modulation wave C of bridge arm L2 A2 with C B2 , and then update the modulation wave C of bridge arm L3 at the same time A3 with C B3 , the modulation wave C of bridge arm L4 A4 with C B4 , the update time differs by half a switching cycle.

[0026] Further preferably, generating a driving signal for a power switch of the dual active bridge converter includes:

[0027] When the sawtooth carrier T L1 Equal to the modulation wave C of bridge arm L1 A1 When , the upper switch tube driving signal of the bridge arm L1 is set to a high level, and the lower switch tube driving signal is set to a low level;

[0028] When the sawtooth carrier T L1 Equal to the modulation wave C of bridge arm L1 B1 When , the upper switch tube driving signal of the bridge arm L1 is set to a low level, and the lower switch tube driving signal is set to a high level;

[0029] When the sawtooth carrier T L2 Equal to the modulation wave C of bridge arm L2 A2 When , the lower switch tube driving signal of the bridge arm L2 is set to a high level, and the upper switch tube driving signal is set to a low level;

[0030] When the sawtooth carrier T L2 Equal to the modulation wave C of bridge arm L2 B2 When , the lower switch tube driving signal of the bridge arm L2 is set to a low level, and the upper switch tube driving signal is set to a high level;

[0031] When the sawtooth carrier T L3 Equal to the modulation wave C of bridge arm L3 A3 When , the upper switch tube driving signal of the bridge arm L3 is set to a high level, and the lower switch tube driving signal is set to a low level;

[0032] When the sawtooth carrier T L3 Equal to the modulation wave C of bridge arm L3 B3 When , the upper switch tube driving signal of the bridge arm L3 is set to a low level, and the lower switch tube driving signal is set to a high level;

[0033] When the sawtooth carrier T L4 Equal to the modulation wave C of bridge arm L4 A4 When , the lower switch tube driving signal of the bridge arm L4 is set to a high level, and the upper switch tube driving signal is set to a low level;

[0034] When the sawtooth wave T L4 is equal to the modulation wave C of the bridge arm L4 B4 , the lower switch tube driving signal of the bridge arm L4 is low, and the upper switch tube driving signal is high.

[0035] Compared with the prior art, the universal transient DC bias suppression method of the dual active bridge converter under bidirectional power flow has the following beneficial effects: (modulation strategy, power forward and reverse)

[0036] 1. The application is suitable for various modulation strategies, including single phase-shift modulation, extended phase-shift modulation, double phase-shift modulation and triple phase-shift modulation, and is suitable for the working condition of bidirectional power flow.

[0037] 2. In the steady-state operation and transient DC bias suppression process of the dual active bridge converter, the calculation expression used by each modulation wave does not change, realizing the unity of steady state and transient state, avoiding the discontinuity problem caused by expression switching and the disturbance caused thereby, and avoiding complex logic judgment and calculation steps in the transient process. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a circuit topology schematic diagram of the dual active bridge converter;

[0039] Figure 2 is an implementation flowchart of the application;

[0040] Figure 3 is a key waveform diagram of the method proposed in the application in working mode 1;

[0041] Figure 4 is a key waveform diagram of the method proposed in the application in working mode 2;

[0042] Figure 5 is an experimental waveform diagram when switching from forward power flow to reverse power flow under traditional TPS modulation;

[0043] Figure 6 is an experimental waveform diagram when switching from reverse power flow to forward power flow under traditional TPS modulation;

[0044] Figure 7 is an experimental waveform diagram when switching from forward light load to forward heavy load under TPS modulation using the method proposed in the application;

[0045] Figure 8 is an experimental waveform diagram when switching from reverse light load to reverse heavy load under TPS modulation using the method proposed in the application;

[0046] Figure 9is an experimental waveform diagram when switching from forward light load to reverse heavy load under TPS modulation by using the method proposed in the application;

[0047] Figure 10 is an experimental waveform diagram when switching from reverse light load to forward heavy load under TPS modulation by using the method proposed in the application. DETAILED DESCRIPTION

[0048] In order for those skilled in the art to better understand the application scheme, the application is further described in detail below through the drawings and specific embodiments.

[0049] The circuit topology of the dual active bridge converter is as shown in Figure 1 Bridge arms L1 and L2 form the primary H-bridge, including power switches S1-S4 and their corresponding body diodes D1-D4; bridge arms L3 and L4 form the secondary H-bridge, including power switches S5-S8 and their corresponding body diodes D5-D8; v ab and v cd are the midpoint voltages of the primary H-bridge and the secondary H-bridge, respectively; V1 and V2 are the primary and secondary DC voltages, respectively; C1 and C2 are the primary and secondary DC side filter capacitors, respectively; n:1 is the turns ratio of the high-frequency transformer T; L is the leakage inductance; L m is the magnetizing inductance; i L is the leakage inductance current; i o is the output current.

[0050] As shown in Figure 2 , the universal transient DC bias suppression method for bidirectional power flow of the dual active bridge converter provided by the embodiment of the application comprises the following steps:

[0051] S1, when the dual active bridge converter is stably running, an asynchronous carrier is generated, as shown in Figure 3 The asynchronous carrier comprises: sawtooth carrier T L1 of bridge arm L1, sawtooth carrier T L2 of bridge arm L2, sawtooth carrier T L3 of bridge arm L3, and sawtooth carrier T L4 of bridge arm L4.

[0052] As shown in Figure 3 and Figure 4 , the phases of carrier T L1 and carrier T L2 are the same, the phases of carrier T L3 and carrier T L4 are the same, and the phases of carrier T L3 , T L4 lag behind the phases of carrier T L1 , T L2 by 180°.

[0053] S2, using triple phase-shift modulation and PI control method, closed-loop operation is performed in each switching period to generate a phase-shift ratio, the phase-shift ratio includes: a primary side inner phase-shift ratio D1, a secondary side inner phase-shift ratio D2 and an outer phase-shift ratio D f .

[0054] When single phase-shift modulation is used, D1=D2=0, when extended phase-shift modulation is used, D1=0, D2≠0 or D1≠0, D2=0, when double phase-shift modulation is used, D1=D2, when triple phase-shift modulation is used, D1≠0 and D2≠0.

[0055] S3, according to the positive and negative relationship between the outer phase-shift ratio of the current switching period and the outer phase-shift ratio of the last switching period, different working modes are selected to generate an asynchronous updated modulation wave, the working modes include: working mode 1 ( Figure 3 ) and working mode 2( Figure 4 ), the modulation wave includes: the modulation wave C A1 and C B1 of the bridge arm L1, the modulation wave C A2 and C B2 of the bridge arm L2, the modulation wave C A3 and C B3 of the bridge arm L3, and the modulation wave C A4 and C B4 .

[0056] The working mode selection specifically includes:

[0057] When the outer phase-shift ratio of the last switching period is positive and the outer phase-shift ratio of the current switching period is positive, no working mode switching is performed, and working mode 1 is selected;

[0058] When the outer phase-shift ratio of the last switching period is negative and the outer phase-shift ratio of the current switching period is negative, no working mode switching is performed, and working mode 2 is selected;

[0059] When the outer phase-shift ratio of the last switching period is positive and the outer phase-shift ratio of the current switching period is negative, the working mode is switched from working mode 1 to working mode 2;

[0060] When the outer phase-shift ratio of the last switching period is negative and the outer phase-shift ratio of the current switching period is positive, the working mode is switched from working mode 2 to working mode 1.

[0061] The calculation expression of the modulation wave of each bridge arm is:

[0062]

[0063] Wherein, y and z are constants, in the preferred embodiment of the present application, y and z are both 0.5, and the calculation formula of x is:

[0064] x=V1 / (V1+nV2) Formula (2)

[0065] Wherein, V1 is the primary DC side voltage of the dual active bridge converter, V2 is the secondary DC side voltage of the dual active bridge converter, and n is the ratio of the primary to secondary turns of the high-frequency transformer of the dual active bridge converter.

[0066] S4. According to the selected working mode, the leading and lagging relationship of the modulation wave is determined, the modulation wave is compared with the carrier wave, and a driving signal for the power switch of the dual active bridge converter is generated to achieve the suppression of transient DC bias.

[0067] Each modulated wave is updated when the carrier is equal to zero. The specific update methods include:

[0068] When selecting working mode 1, if Figure 3 As shown, the modulation wave C of the bridge arm L3 is updated at the same time. A3 with C B3 , the modulation wave C of bridge arm L4 A4 with C B4 , and then update the modulation wave C of bridge arm L1 at the same time A1 with C B1 , the modulation wave C of bridge arm L2 A2 with C B2 , the update time differs by half a switching cycle;

[0069] When selecting working mode 2, if Figure 4 As shown, the modulation wave C of the bridge arm L1 is updated simultaneously. A1 with C B1 , the modulation wave C of bridge arm L2 A2 with C B2 , and then update the modulation wave C of bridge arm L3 at the same time A3 with C B3 , the modulation wave C of bridge arm L4 A4 with C B4 , the update time differs by half a switching cycle.

[0070] In a preferred embodiment of the present invention, Figure 3 and Figure 4 As shown, the generating of the driving signal of the power switch of the dual active bridge converter includes:

[0071] When the sawtooth carrier T L1 Equal to the modulation wave C of bridge arm L1 A1 When , the upper switch tube driving signal of the bridge arm L1 is set to a high level, and the lower switch tube driving signal is set to a low level;

[0072] When the sawtooth carrier T L1 Equal to the modulation wave C of bridge arm L1 B1 When , the upper switch tube driving signal of the bridge arm L1 is set to a low level, and the lower switch tube driving signal is set to a high level;

[0073] When the sawtooth carrier T L2 is equal to the modulation wave C A2 of the bridge arm L2, the lower switch driving signal of the bridge arm L2 is set to high level, and the upper switch driving signal is set to low level.

[0074] When the sawtooth carrier T L2 is equal to the modulation wave C B2 of the bridge arm L2, the lower switch driving signal of the bridge arm L2 is set to low level, and the upper switch driving signal is set to high level.

[0075] When the sawtooth carrier T L3 is equal to the modulation wave C A3 of the bridge arm L3, the upper switch driving signal of the bridge arm L3 is set to high level, and the lower switch driving signal is set to low level.

[0076] When the sawtooth carrier T L3 is equal to the modulation wave C B3 of the bridge arm L3, the upper switch driving signal of the bridge arm L3 is set to low level, and the lower switch driving signal is set to high level.

[0077] When the sawtooth carrier T L4 is equal to the modulation wave C A4 of the bridge arm L4, the lower switch driving signal of the bridge arm L4 is set to high level, and the upper switch driving signal is set to low level.

[0078] When the sawtooth carrier T L4 is equal to the modulation wave C B4 of the bridge arm L4, the lower switch driving signal of the bridge arm L4 is set to low level, and the upper switch driving signal is set to high level.

[0079] Figures 5 to 10 In the formula, v ab is the midpoint voltage of the primary H-bridge, v cd is the midpoint voltage of the secondary H-bridge, i L is the inductance current.

[0080] Figure 5 The experimental waveform diagram when switching from forward power flow to reverse power flow under traditional TPS modulation is exemplarily shown, Figure 6 The experimental waveform diagram when switching from reverse power flow to forward power flow under traditional TPS modulation is exemplarily shown. It can be seen that, under traditional TPS modulation, when the power flow direction changes suddenly, serious transient DC bias will be generated, which will increase the current stress of the power switch and easily saturate the magnetic core of the magnetic element.

[0081] Figures 7 to 10 The experimental waveform diagram of transient DC bias suppression under typical working conditions of TPS modulation by using the method proposed in the present application is exemplarily shown.Figure 7 for a switching process from forward light load to forward heavy load, Figure 8 for a switching process from reverse light load to reverse heavy load, Figure 9 for a switching process from forward light load to reverse heavy load, Figure 10 for a switching process from reverse light load to forward heavy load, it can be seen that the transient DC bias is effectively suppressed by using the method proposed by the present application.

[0082] Obviously, the above-mentioned embodiments are only examples for clearly illustrating the present application, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and also impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A general transient DC offset suppression method for dual active bridge converter under bidirectional power flow, characterized in that, The method comprises the following steps: S1, the double active bridge converter generates asynchronous carrier wave when stably running, the asynchronous carrier wave includes: sawtooth carrier wave T of original side bridge arm L1 L1 , sawtooth carrier wave T of original side bridge arm L2 L2 , sawtooth carrier wave T of auxiliary side bridge arm L3 L3 , sawtooth carrier wave T of auxiliary side bridge arm L4 L4 ; S2, adopt certain modulation strategy and control strategy, each switch cycle closed loop operation generates phase shift ratio, the modulation strategy includes: single phase shift modulation, extended phase shift modulation, double phase shift modulation and triple phase shift modulation, the phase shift ratio includes: the original side inner phase shift ratio D1, the auxiliary side inner phase shift ratio D2 and the outer phase shift ratio D f ; S3, according to the positive and negative relationship between the phase shift compared with the previous switching cycle and the phase shift compared with the previous switching cycle, select different working modes to generate asynchronous update modulation waves, the working modes include: working mode 1 and working mode 2, and the modulation waves include: the modulation wave C of the bridge arm L1 A1 With C B1 , the modulation wave C of the bridge arm L2 A2 With C B2 , the modulation wave C of the bridge arm L3 A3 With C B3 , the modulation wave C of the bridge arm L4 A4 With C B4 ; S4, according to the selected working mode, determining the lead and lag relationship of the modulation wave, comparing the modulation wave with the carrier wave, generating the drive signal of the dual active bridge converter power switch, realizing the transition from one steady state to another steady state in a switching cycle, eliminating the transient peak of the leakage inductance current, and realizing the suppression of the transient DC bias.

2. The general transient DC offset rejection method for bidirectional power flow of a dual active bridge converter according to claim 1, wherein, In S1, the carrier T L1 and the carrier T L2 have the same phase, the carrier T L3 and the carrier T L4 have the same phase, the carrier T L3 , T L4 lags the carrier T L1 , T L2 by 180°.

3. The general transient DC offset rejection method for dual active bridge converter under bidirectional power flow of claim 1, wherein, In S2, when the single phase-shift modulation is adopted, D1=D2=0; when the extended phase-shift modulation is adopted, D1=0, D2≠0 or D1≠0, D2=0; when the double phase-shift modulation is adopted, D1=D2; and when the triple phase-shift modulation is adopted, D1≠0 and D2≠0.

4. The general transient DC offset rejection method for dual active bridge converter under bidirectional power flow of claim 1, wherein, In S3, the working mode selection specifically comprises: When the phase-shift ratio of the previous switching cycle is positive and the phase-shift ratio of the current switching cycle is positive, no working mode switching is performed, and the working mode 1 is selected; When the phase-shift ratio of the previous switching cycle is negative and the phase-shift ratio of the current switching cycle is negative, no working mode switching is performed, and the working mode 2 is selected; When the phase-shift ratio of the previous switching cycle is positive and the phase-shift ratio of the current switching cycle is negative, the working mode 1 is switched to the working mode 2; When the phase-shift ratio of the previous switching cycle is negative and the phase-shift ratio of the current switching cycle is positive, the working mode 2 is switched to the working mode 1.

5. The general transient DC offset mitigation method for dual active bridge converter under bidirectional power flow of claim 1, wherein, In S3, the calculation expression of the modulation wave of each bridge arm is: where x, y and z are the coefficients of the phase shift of the modulated wave when calculating the time shift of D f , D1 and D2, y and z are both 0.5, and the calculation formula of x is: x=V1 / (V1+nV2) Formula (2) Wherein, V1 is the primary side DC voltage of the dual active bridge converter, V2 is the secondary side DC voltage of the dual active bridge converter, and n is the ratio of the primary and secondary side turns of the high-frequency transformer of the dual active bridge converter.

6. The general transient DC offset rejection method for dual active bridge converter under bidirectional power flow of claim 1, wherein, In S4, each modulation wave is updated when the carrier wave is equal to zero, and the updating mode specifically comprises: When the working mode 1 is selected, the modulation wave C of the bridge arm L3 is updated first A3 with C B3 , the modulation wave C of the bridge arm L4 is updated simultaneously A4 with C B4 , the modulation wave C of the bridge arm L1 is updated simultaneously A1 with C B1 , the modulation wave C of the bridge arm L2 is updated simultaneously A2 with C B2 , and the update time is half a switching period apart When the working mode 2 is selected, the modulation wave C A1 with C B1 , the modulation wave C A2 with C B2 , the modulation wave C A3 with C B3 , the modulation wave C A4 with C B4 of the bridge arm L4 are updated at the same time, and the update time is half a switching period apart.

7. The general transient DC offset rejection method for dual active bridge converter under bidirectional power flow of claim 1, wherein, In S4, the generation of the drive signal of the dual active bridge converter power switch comprises: When the sawtooth carrier T L1 is equal to the modulation wave C of the bridge arm L1 A1 , the upper switch driving signal of the bridge arm L1 is set to high level, and the lower switch driving signal is set to low level; When the sawtooth carrier T L1 is equal to the modulation wave C B1 of the bridge arm L1, the upper switch driving signal of the bridge arm L1 is set to low level, and the lower switch driving signal is set to high level; When the sawtooth carrier T L2 is equal to the modulation wave C A2 of the bridge arm L2, the lower switch driving signal of the bridge arm L2 is set to high level, and the upper switch driving signal is set to low level; When the sawtooth carrier T L2 is equal to the modulation wave C B2 of the bridge arm L2, the lower switch driving signal of the bridge arm L2 is set to low level, and the upper switch driving signal is set to high level; When the sawtooth carrier T L3 is equal to the modulation wave C A3 of the bridge arm L3, the upper switch driving signal of the bridge arm L3 is set to high level, and the lower switch driving signal is set to low level; When the sawtooth carrier T L3 is equal to the modulation wave C of the bridge arm L3 B3 , the upper switch driving signal of the bridge arm L3 is set to low level, and the lower switch driving signal is set to high level; When the sawtooth carrier T L4 is equal to the modulation wave C A4 of the bridge arm L4, the lower switch driving signal of the bridge arm L4 is set to high level, and the upper switch driving signal is set to low level; When the sawtooth carrier T L4 is equal to the modulation wave C B4 of the bridge arm L4, the lower switch drive signal of the bridge arm L4 is set to low level, and the upper switch drive signal is set to high level.

Images