DAB converter with double-transformer structure and single-tube fault tolerance method

Abstract

The invention provides a DAB converter with a double-transformer structure, which comprises an input side bridge arm group, a transformer group and an output side bridge arm group, and is characterized in that an auxiliary switch is additionally arranged in the input side bridge arm group, so that fault-tolerant operation of all switches when a fault occurs is realized, and the reliability of a system is remarkably improved. According to the single-tube fault-tolerant method realized by the DAB converter with the double-transformer structure, in a fault-tolerant mode, the inductance current stress is relatively small, additional conduction loss caused by overlarge current stress is avoided, and meanwhile, further damage to the semiconductor switch is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of power systems, and in particular to a dual-transformer structure DAB converter and a single-tube fault-tolerant method. Background Art

[0002] With the rapid development of renewable energy and electric vehicle systems, the importance of DC distribution systems in power transmission continues to increase. Dual active bridge (DAB) converters have become one of the most promising solutions due to their high power density, excellent transmission efficiency and wide soft switching range. In the DAB converter, the dual transformer structure can not only achieve a wider zero voltage switching (ZVS) range, but also effectively reduce the filter size. The reliability of the DAB converter is critical to the DC power transmission system, especially in the event of a fault. Common fault types include short circuit faults and open circuit faults, among which open circuit faults will cause current stress and DC bias current to increase, thereby reducing system efficiency and damaging other components. Therefore, open circuit fault tolerance control of the converter power switch is the key to ensure reliable system operation.

[0003] At present, although traditional fault-tolerant methods, such as module redundancy, can effectively deal with faults, they will significantly increase hardware costs and are not suitable for DAB converters. In recent years, fault-tolerant methods for DAB converters have continued to develop, among which the "primary side power reduction and secondary side bypass method" has become the mainstream solution. This method restores the circuit to symmetrical operation by cutting off the faulty switch bridge arm, but can only ensure that the converter transmits part of the power. Another method is to increase the neutral line, improve the power transmission capacity in the fault-tolerant mode by improving the control strategy and circuit design, and can handle a variety of fault conditions. However, this method is only applicable to DAB converters with symmetrical structures. For dual transformer structures, adding a neutral line will introduce additional neutral line current. Summary of the invention

[0004] In order to overcome the above technical defects, the present application provides a dual-transformer structure DAB converter and a single-tube fault-tolerant method. To achieve the above purpose, the present application is implemented according to the following technical solutions: In a first aspect, the present application provides a dual-transformer structure DAB converter, comprising: an input-side bridge arm group, a transformer group, and an output-side bridge arm group; The input side bridge arm group includes an input capacitor bridge arm, a main power bridge arm and an auxiliary power bridge arm. The input voltage V 1 The positive and negative electrodes are connected to the two ends of the input capacitor bridge arm and the auxiliary power bridge arm in sequence, wherein the input capacitor bridge arm includes a series-connected input split filter capacitor C 1 and input split filter capacitors C 2 , C1 The negative electrode and C 2 The node formed by connecting the positive electrodes is C, and the main power bridge arm includes a MOSFET connected in series S 7 and S 6， And in parallel S 7 The MOSFETs at both ends S 5， S 5 The source of S 6 The source and S 7 The source is connected, and S 5 , S 6 and S 7 Contains anti-parallel diodes, S 6 The drain of C 1 The negative electrode and C 2 The secondary power bridge arm includes a MOSFET in series. S 1 and S 2 , MOSFETs in series S 3 and S 4 ,and S 1 , S 2 , S 3 and S 4 They all contain anti-parallel diodes. S 1 The source of S 2 The drain and S 7 The node formed by connecting the drain of S 3 The source of S 4 The drain and S 5 The node formed by connecting the drain of is B; The transformer group includes the main power transformer , Auxiliary power transformer , AC inductance and DC blocking capacitors , Primary negative electrode and DC blocking capacitor One end of the capacitor is connected to the The other end of is connected to node B. Primary positive and The positive pole of the primary side is connected to node A respectively. The primary negative electrode is connected to node C. Secondary positive pole and AC inductor One end is connected to The secondary negative electrode and The secondary side positive pole is connected; The output side bridge arm group includes two MOSFETs connected in series Q 1 and Q 2 , two split filter capacitors in series C 3 and C 4 ,and Q 1 and Q 2 They all contain anti-parallel diodes. Q 1 The source and Q 2 The node formed by connecting the drain of L k The other end is connected to C 3 Negative electrode and C 4 The node formed by connecting the positive electrodes is G, and the node G is connected to T r2 The negative pole of the secondary side is connected, V 2 The positive electrode is Q 1 Drain and C 3 Positive pole connected, V 2 Respectively Q 2 The source and C 4 Negative pole connected.

[0005] Optionally, in the input side bridge arm, the input voltage V 1 The positive pole of the split filter capacitor is C 1 positive electrode, S 1 The drain and S 3 The drain is connected to the input voltage V 1The negative pole of the split filter capacitor C 2 The negative electrode, S 2 The source and S 4 The source is connected.

[0006] In a second aspect, the present application provides a single-tube fault-tolerant method for a dual-transformer DAB converter, using the dual-transformer DAB converter as described in the first aspect, characterized in that, in a fault condition, the fault mode of the dual-transformer structure includes a first fault-tolerant mode: In the first fault-tolerant mode: switch S 6 or S 5 When an open circuit fault occurs, the auxiliary bridge arm switch is disabled. S 5 and S 7 The gate signal or switch tube S 6 and S 7 The gate signal controls the switch tube S 1 ~ S 4 as well as Q 1 , Q 2 Realize power transmission of converter; In the first fault-tolerant mode, the inductor current expression of the converter is: , In the formula ， is the leakage inductance current in the first fault-tolerant mode, is the input voltage, is the output voltage, For transformer Turns ratio, For transformer Turns ratio, is the AC inductance; Based on the inductor current expression of the converter, the transmission power of the converter is determined as: , In the formula, is the output power of the converter in the first fault-tolerant mode, For two transformers and Secondary series voltage, as well as are the duty cycle corresponding to the on-time, , , .

[0007] Optionally, the failure mode of the dual transformer structure further includes a second fault-tolerant mode: In the second fault-tolerant mode: switch S 1 or S 2 When an open circuit fault occurs, the switch is disabled. S 2 and S 5 The gate signal or S 1 and S 5 The gate signal operates the switch tube S 6 , S 7 To implement the switch S 1 , S 2 The use of anti-parallel diodes and the control of the switch tube S 3 , S 4 as well as Q 1 , Q 2 Realize the power transmission control switch tube of the converter and S 1 ~ S 4 as well as Q 1 , Q 2 Realize power transmission of converter; In the second fault-tolerant mode, the current inductance expression of the converter is: , In the formula, is the leakage inductance current in the second fault-tolerant mode; Based on the inductor current expression of the converter, the transmission power of the converter is determined as: , In the formula, is the transmission power of the converter in the second fault-tolerant mode.

[0008] Optionally, the failure mode of the dual transformer structure further includes a third fault-tolerant mode: In the third fault-tolerant mode, the switchS 3 or S 4 When an open circuit fault occurs, the switch is disabled. S 4 and S 5 The gate signal or switch tube S 3 and S 5 The gate signal of the inductor current is switched to S 1 , S 2 , S 6 and S 7 , using only transformer T r2 Transmission power; In the third fault-tolerant mode, the inductor current expression of the converter is: , In the formula, is the leakage inductance current in the third fault-tolerant mode; Based on the inductor current expression of the converter, the transmission power of the converter is determined as: , In the formula, is the transmission power of the converter in the third fault-tolerant mode.

[0009] Optionally, the failure mode of the dual transformer structure further includes a fourth fault-tolerant mode: In the fourth fault-tolerant mode: if the switch Q 1 or Q 2 When an open circuit fault occurs, the secondary switch is disabled. Q 2 or Q 1 The gate signal controls the switch tube S 1 ~ S 6 Realize unidirectional power transmission of the converter; In the fourth fault-tolerant mode, the inductor current expression of the converter is: , In the formula, is the leakage inductance current in the fourth fault-tolerant mode; Based on the inductor current expression of the converter, the transmission power of the converter is determined as: , In the formula, is the transmission power of the converter in the fourth fault-tolerant mode.

[0010] This application has the following beneficial effects: A fault-tolerant dual-transformer structure DAB topology proposed in the present application realizes fault-tolerant operation of all switches when a fault occurs by adding an auxiliary switch, which significantly improves the reliability of the system. In different fault-tolerant modes, the inductor current stress is small, which avoids the additional conduction loss caused by excessive current stress and reduces further damage to the semiconductor switch. During the mode conversion process, the inductor current does not produce a large impact, ensuring a smooth switching process. The impact of transient impact on system performance is avoided, thereby showing good dynamic performance.

[0011] In addition to the above-described purposes, features and advantages, the present application has other purposes, features and advantages. The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 This is a schematic diagram of a dual-transformer DAB converter structure provided in an embodiment of the present application; Figure 2 This is a waveform diagram of a dual-transformer structure DAB converter provided in an embodiment of the present application in a normal working mode; Figure 3 A dual-transformer DAB converter is provided in an embodiment of the present application. Figure 3 (a) When the dual-transformer DAB converter is in the first fault-tolerant mode, the switch S 6 Equivalent circuit diagram of an open circuit fault. Figure 3 (b) is a waveform diagram of a dual-transformer DAB converter in the first fault-tolerant mode; Figure 4 A dual-transformer DAB converter is provided in an embodiment of the present application. Figure 4 (a) is a dual-transformer DAB converter. When in the second fault-tolerant mode, the switch S 1 Equivalent circuit diagram of an open circuit fault; Figure 4 (b) is a waveform diagram of a dual-transformer DAB converter in the second fault-tolerant mode; Figure 5 A dual-transformer DAB converter is provided in an embodiment of the present application. Figure 5 (a) is a dual-transformer DAB converter. When in the third fault-tolerant mode, the switch S 3 Equivalent circuit diagram of an open circuit fault; Figure 5 (b) is a waveform diagram of a dual-transformer DAB converter in the third fault-tolerant mode; Figure 6 A dual-transformer DAB converter is provided in an embodiment of the present application. Figure 6 (a) is a dual-transformer DAB converter. When in the fourth fault-tolerant mode, the switch Q 1 Equivalent circuit diagram of an open circuit fault; Figure 6 (b) is a waveform diagram of a dual-transformer DAB converter in the fourth fault-tolerant mode; Figure 7 It is an experimental simulation diagram provided in the embodiment of the present application. Figure 7 (a) is the experimental simulation, the switch tube S 6 After an open circuit fault occurs, when switching to the first fault tolerance mode, the output voltage V 2 Experimental waveform diagram of Figure 7 (b) is the experimental simulation, the switch tube S 6 After an open circuit fault occurs, when switching to the first fault-tolerant mode, the secondary series voltage of the two transformers and the secondary full-bridge voltage The experimental waveform diagram, Figure 7 (c) is the experimental simulation, the switch tube S 6 After an open circuit fault occurs, when switching to the first fault-tolerant mode, the inductor current Experimental waveform diagram. DETAILED DESCRIPTION

[0013] The embodiments of the present application are described in detail below with reference to the accompanying drawings; however, the present application can be implemented in many different ways as defined and covered by the claims.

[0014] In order to solve the problems raised in the background technology, such as Figure 1 As shown, the present application proposes a dual-transformer structure DAB converter, including: an input side bridge arm group, a transformer group and an output side bridge arm group; the input side bridge arm group includes an input capacitor bridge arm, a main power bridge arm and an auxiliary power bridge arm, and the input voltage V 1The positive and negative electrodes are connected to the two ends of the input capacitor bridge arm and the auxiliary power bridge arm in sequence, wherein the input capacitor bridge arm includes a series-connected input split filter capacitor C 1 and input split filter capacitors C 2 , C 1 The negative electrode and C 2 The node formed by connecting the positive electrodes is C, and the main power bridge arm includes a MOSFET connected in series S 7 and S 6， And in parallel S 7 The MOSFETs at both ends S 5， S 5 The source of S 6 The source and S 7 The source is connected, and S 5 , S 6 and S 7 Contains anti-parallel diodes, S 6 The drain of C 1 The negative electrode and C 2 The secondary power bridge arm includes a MOSFET in series. S 1 and S 2 , MOSFETs in series S 3 and S 4 ,and S 1 , S 2 , S 3 and S 4 They all contain anti-parallel diodes. S 1 The source of S 2 The drain and S 7 The node formed by connecting the drain of S 3 The source of S4 The drain and S 5 The node formed by connecting the drain of is B; The transformer group includes the main power transformer , Auxiliary power transformer , AC inductance and DC blocking capacitors , Primary negative electrode and DC blocking capacitor One end of the capacitor is connected to the The other end of is connected to node B. Primary positive and The positive pole of the primary side is connected to node A respectively. The primary negative electrode is connected to node C. Secondary positive pole and AC inductor One end is connected to The secondary negative electrode and The secondary side positive pole is connected; The output side bridge arm group includes two MOSFETs connected in series Q 1 and Q 2 , two split filter capacitors in series C 3 and C 4 , Q 1 The source and Q 2 The node formed by connecting the drain of The other end is connected to C 3 Negative electrode and C 4 The node formed by connecting the positive electrodes is G, and the node G is connected to The negative pole of the secondary side is connected, V 2 The positive electrode is Q 1 Drain and C 3 Positive pole connected, V 2 Respectively Q 2 The source and C 4 Negative pole connected.

[0015] Among them, in the input side bridge arm, the input voltage V 1 The positive pole of the split filter capacitor is C 1 positive electrode, S 1 The drain andS 3 The drain is connected to the input voltage V 1 The negative pole of the split filter capacitor C 2 The negative electrode, S 2 The source and S 4 The source is connected.

[0016] Simple Figure 1 The topological structure is summarized as follows: C 1 , C 2 is the input split filter capacitor, C 3 , C 4 is the output filter capacitor. V 1 and V 2 Indicates the voltage switch tubes on both sides of the converter S 1 ~ S 6 and Q 1 ~ Q 2 It forms the active switch branches on both sides, and the AC inductor represents the sum of the transformer leakage inductance and external AC inductance reflected to the secondary side, It is a DC blocking capacitor. The two sides are connected in parallel by the primary side and in series by the secondary side. and The turns ratios of the two are , ,in They are and The number of turns on the primary and secondary sides. The positive direction of current flow is already in Figure 1 Winning bid.

[0017] based on Figure 1 A dual-transformer structure DAB converter is shown. The present application also proposes a single-transistor fault-tolerant method for the dual-transformer structure DAB converter.

[0018] In addition, before the specific analysis, the following assumptions are made: 1) All switches, inductors, capacitors and transformers are ideal.

[0019] 2) Filter capacitor Large enough so that the input voltage and output voltage are considered constant.

[0020] 3) The impact of dead time can be ignored.

[0021] like Figure 2 As shown, the key waveform of the DAB converter in normal working mode at this time, in this figure, T s represents the switching cycle, T 1 Indicates switch S 1 , S 4 as well as S 5 The common conduction time, T 2 Indicates switch S 1 , S 5 as well as S 6 The common conduction time, It means switch S 1 and Q 1 The phase shift time, D 1 , D 2 as well as are the duty ratios of the corresponding on-times. is the secondary series voltage of the two transformers, is the voltage generated by the secondary full bridge. is the leakage inductance current.

[0022] Normally, the converter switches S 7 Shutdown, by controlling the switch S 1 ~ S 6 and Q 1 ~ Q 2 Work. Analysis Figure 2 It can be seen that the inductor current expression of the converter is: (1) Then, based on the converter inductor current expression and its waveform symmetry and the characteristics of zero steady-state average value, the converter transmission power under normal working conditions is obtained as: (2) in, , , .

[0023] In case of failure, four fault tolerance modes are proposed: The first fault tolerance mode A, for example, with a switch S 6 or S 5 When an open circuit fault occurs, the auxiliary bridge arm switch is disabled. S 5 and S 7 The gate signal or switch tube S 6 and S 7 The gate signal controls the switch tube S 1 ~ S 4 as well as Q 1 , Q 2 To achieve power transmission of the converter; Figure 3 (a) shows that when S6 fails, the auxiliary bridge arm switch is disabled. S 5 and S 7 The gate signal, in this mode, Figure 3 (b) By controlling the switch S 1 ~ S 4 as well as Q 1 , Q 2 Realize the power transmission of the converter.

[0024] based on Figure 3 (a) and Figure 3 (b) In the first fault-tolerant mode, the inductor current expression of the converter is: (3) In the formula ， is the leakage inductance current in the first fault-tolerant mode, is the input voltage, is the output voltage, For transformer Turns ratio, For transformer Turns ratio, is the AC inductance; Based on the expression of the converter inductor current and the characteristics of its waveform symmetry and zero steady-state average value, the transmission power of the converter is determined as: (4) In the formula, is the output power of the converter in the first fault-tolerant mode, For two transformers and Secondary series voltage.

[0025] It should be noted that the switch S 5 When an open circuit fault occurs, the corresponding converter inductor current expression and converter transmission power expression are the same as the above switch S 5 When an open circuit fault occurs, the corresponding converter inductor current expression is the same as the converter transmission power expression.

[0026] The second fault tolerance mode B, for example, the switch S 1 or S 2 When an open circuit fault occurs, the switch is disabled. S 2 and S 5 The gate signal or S 1 and S 5 The gate signal operates the switch tube S 6 , S 7 To implement the switch S 1 , S 2 The use of anti-parallel diodes and the control of the switch tube S 3 , S 4 as well as Q 1 , Q 2 Realize the power transmission control switch tube of the converter and S 1 ~ S 4 as well as Q 1 , Q 2 To achieve power transmission of the converter; Figure 4 As shown in (a), S 1 After an open circuit fault occurs, the switch is disabled. S 2 and S 5 The gate signal, such as Figure 4 (b) By operating the switch S 6 , S 7 To implement the switch S 1 , S 2 The use of anti-parallel diodes and the control of the switch tube S 3 , S 4 as well as Q 1 , Q 2 Realize the power transmission of the converter.

[0027] based on Figure 4 (a) and Figure 4 (b) In the second fault-tolerant mode, the inductor current expression of the converter is obtained as follows: (5) In the formula, is the leakage inductance current in the second fault-tolerant mode; Furthermore, based on the inductor current expression of the converter and the characteristics of its waveform symmetry and zero steady-state average value, the transmission power of the converter in the second fault-tolerant mode B is obtained as follows: (6) In the formula, is the transmission power of the converter in the second fault-tolerant mode.

[0028] It should be noted that the switch S 2 When an open circuit fault occurs, the corresponding converter inductor current expression and converter transmission power expression are the same as the above switch S 1 When an open circuit fault occurs, the corresponding converter inductor current expression is the same as the converter transmission power expression.

[0029] The third fault-tolerant mode C: After an open circuit fault occurs, the switch S 3 or S 4 When an open circuit fault occurs, the switch is disabled. S 4 and S 5 The gate signal or switch S 3 and S 5 In this mode, the conduction path of the inductor current is switched toS 1 , S 2 , S 6 and S 7 , using only transformer Transmission power. Figure 5 (a) shows the switch S 3 The open circuit fault is taken as an example for analysis. After the open circuit fault occurs, the switch tube is disabled. S 4 In this mode, if Figure 5 (b) shows that the conduction path of the inductor current is switched to S 1 , S 2 , S 6 and S 7 , using only transformer Transmit power, that is, by controlling the switch S 1 , S 2 , S 6 and S 7 and Q 1 ~ Q 2 Work.

[0030] based on Figure 5 (a) and Figure 5 (b) It is obtained that in the third fault-tolerant mode, the inductor current expression of the converter is: (7) In the formula, is the leakage inductance current in the third fault-tolerant mode; Based on the inductor current expression of the converter and the characteristics of its waveform symmetry and zero steady-state average value, the transmission power of the converter is determined as: (8) In the formula, is the transmission power of the converter in the second fault-tolerant mode.

[0031] It should be noted that the switch S 4 When an open circuit fault occurs, the corresponding converter inductor current expression and converter transmission power expression are the same as the above switch S3 When an open circuit fault occurs, the corresponding converter inductor current expression is the same as the converter transmission power expression.

[0032] The fourth fault-tolerant mode D: If the switch Q 1 or Q 2 When an open circuit fault occurs, the secondary switch is disabled. Q or Q 1 The gate signal controls the switch tube S 1 ~ S 6 Realize the unidirectional power transmission of the converter. Q 1 When an open circuit fault occurs, the equivalent circuit diagram is as follows: Figure 6 (a). In this mode, Figure 6 (b) By controlling the switch S 1 ~ S 6 Realize unidirectional power transmission of the converter.

[0033] based on Figure 6 (a) and Figure 6 (b) In the fourth fault-tolerant mode, the inductor current expression of the converter is: (9) In the formula, is the transmission power of the converter in the fourth fault-tolerant mode.

[0034] Based on the inductor current expression of the converter and the characteristics of its waveform symmetry and zero steady-state average value, the transmission power of the converter is determined as: (10) In the formula, is the transmission power of the converter in the fourth fault-tolerant mode.

[0035] It should be noted that the switch Q 1 When an open circuit fault occurs, the corresponding converter inductor current expression and converter transmission power expression are the same as the above switch Q 2 When an open circuit fault occurs, the corresponding converter inductor current expression is the same as the converter transmission power expression.

[0036] Experimental simulation stage The proposed fault-tolerant DAB converter topology is built in MATLAB / Simulink, and the power device switching signal is stopped at a certain moment to simulate the open-circuit fault of the power device, so as to perform fault-tolerant simulation of the open-circuit fault of the relevant fully controlled device. The specific circuit simulation parameters are shown in Table 1.

[0037] Table 1 Main circuit simulation parameters , Figure 7 (a)- Figure 7 (c) shows the switch tube S 6 The experimental waveform of switching to fault-tolerant mode A after an open circuit fault occurs. Figure 7 (b), and They represent the secondary series voltage and the secondary full-bridge voltage of the two transformers respectively. Leakage Inductance The current, is the secondary output voltage. In normal operation mode, the converter power switch operates in the zero voltage conduction state. At about 0.01 seconds, the switch tube S 6 An open circuit fault occurs, causing the circuit to operate asymmetrically, which in turn causes the output voltage A drop occurs, and the inductor current After the fault occurs, the converter switches to fault-tolerant mode A, and the output voltage It will gradually return to normal value, and the inductor current will gradually return to the symmetrical state, and the recovery time is about 0.005 seconds. It can be seen from the figure that the converter still maintains the zero voltage conduction state in fault-tolerant mode A. Although the inductor current stress is slightly increased compared with the normal mode, the output voltage and current remain stable. This shows that the proposed fault-tolerant DC converter topology and its fault-tolerant mode have good working performance.

[0038] As described above, the proposed fault-tolerant dual-transformer structure DAB topology proposed in the present application realizes fault-tolerant operation of all switches when a fault occurs by adding an auxiliary switch, which significantly improves the reliability of the system. In different fault-tolerant modes, the inductor current stress is small, which avoids the additional conduction loss caused by excessive current stress and reduces further damage to the semiconductor switch. During the mode conversion process, the inductor current does not produce a large impact, ensuring a smooth switching process. The impact of transient impact on system performance is avoided, thereby showing good dynamic performance.

[0039] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A dual-transformer DAB converter, characterized in that: include: Input side bridge arm group, transformer group and output side bridge arm group; The input side bridge arm group includes an input capacitor bridge arm, a main power bridge arm and an auxiliary power bridge arm, and the positive and negative electrodes of the input voltage V1 are connected to the two ends of the input capacitor bridge arm and the auxiliary power bridge arm in sequence, wherein the input capacitor bridge arm includes an input split filter capacitor connected in series C 1 and input split filter capacitor C 2. C 1 negative electrode and C 2 is connected to form a node C, and the main power bridge arm includes a MOSFET connected in series S 7 and S 6， And in parallel S 7 MOSFET across both ends S 5， S 5 source, S 6 source and S 7 sources are connected, and S 5. S 6 and S 7 contains an anti-parallel diode, S The drain of 6 is connected to C 1 negative electrode and C 2, the secondary power bridge arm includes a MOSFET in series S 1 and S 2. MOSFETs in series S 3 and S 4, and S 1. S 2. S 3 and S 4 all contain anti-parallel diodes. S 1 source, S 2 drain and S The node formed by connecting the drain of 7 is A. S 3 source, S 4 drain and S The node formed by connecting the drains of 5 is B; The transformer group includes the main power transformer , Auxiliary power transformer , AC inductance and DC blocking capacitors , Primary negative electrode and DC blocking capacitor One end of the capacitor is connected to the The other end of is connected to node B. Primary positive and The positive pole of the primary side is connected to node A respectively. The primary negative electrode is connected to node C. Secondary positive pole and AC inductor One end is connected to The secondary negative electrode and The secondary side positive pole is connected; The output side bridge arm group includes two MOSFETs connected in series Q 1 and Q 2. Two split filter capacitors in series C 3 and C 4, and Q 1 and Q 2 both contain anti-parallel diodes. Q 1 source and Q The node formed by connecting the drain of 2 is F, and the node F and the AC inductor L k The other end is connected to C 3 negative electrode and C 4 The positive poles are connected to form a node called G. T r2 The negative pole of the secondary side is connected to the positive pole of V2. Q 1 drain and C 3 positive pole connected, V2 and Q 2 source and C 4 Negative poles connected.

2. The DAB converter according to claim 1, characterized in that: In the input side bridge arm, the positive electrode of the input voltage V1 is connected to the split filter capacitor C 1 positive electrode, S 1 drain and S 3, the negative electrode of the input voltage V1, and the split filter capacitor C 2 negative electrode, S 2 source and S 4 are connected to the source.

3. A single-transistor fault-tolerant method for a dual-transformer DAB converter, using the dual-transformer DAB converter as claimed in claim 1, characterized in that: In the event of a fault, the fault mode of the dual transformer structure includes a first fault-tolerant mode; In the first fault-tolerant mode: switch S 6 or S 5. When an open circuit fault occurs, the auxiliary bridge arm switch is disabled. S 5 and S 7 gate signal or switch tube S 6 and S 7 gate signal, controls the switch tube S 1~ S 4 and Q 1. Q 2. Realize power transmission of converter; In the first fault-tolerant mode, the inductor current expression of the converter is: ， In the formula ， is the leakage inductance current in the first fault-tolerant mode, is the input voltage, is the output voltage, For transformer Turns ratio, For transformer Turns ratio, is the AC inductance; Based on the inductor current expression of the converter, the transmission power of the converter is determined as: ， In the formula, is the output power of the converter in the first fault-tolerant mode, For two transformers and Secondary series voltage, as well as are the duty cycle corresponding to the on-time, , , .

4. The method according to claim 3, characterized in that: The failure mode of the dual transformer structure also includes a second fault-tolerant mode: In the second fault-tolerant mode: switch S 1 or S 2 When an open circuit fault occurs, the switch is disabled. S 2 and S The gate signal of 5 or the gate signal of , operates the switch tube S 6. S 7 to realize the switch S 1. S 2. The use of anti-parallel diodes and the control of the switch tube S 3. S 4 and Q 1. Q 2. Realize the power transmission control switch tube and S 1~ S 4 and Q 1. Q 2. Realize power transmission of converter; In the second fault-tolerant mode, the inductor current expression of the converter is: ， In the formula, is the leakage inductance current in the second fault-tolerant mode; Based on the inductor current expression of the converter, the transmission power of the converter is determined as: ， In the formula, is the transmission power of the converter in the second fault-tolerant mode.

5. The method according to claim 3, characterized in that: The failure mode of the dual transformer structure also includes a third fault-tolerant mode: In the third fault-tolerant mode, the switch S 3 or S 4 When an open circuit fault occurs, the switch is disabled. S 4 and S 5 gate signal or switch tube S 3 and S 5 gate signal; the conduction path of the inductor current is switched to S 1. S 2. S 6 and S 7. Use only transformer Transmission power; In the third fault-tolerant mode, the inductor current expression of the converter is: ， In the formula, is the leakage inductance current in the third fault-tolerant mode; Based on the inductor current expression of the converter, the transmission power of the converter is determined as: ， In the formula, is the transmission power of the converter in the third fault-tolerant mode.

6. The method according to claim 3, characterized in that: The failure mode of the dual transformer structure also includes a fourth fault-tolerant mode: In the fourth fault-tolerant mode: if the switch Q 1 or Q 2 When an open circuit fault occurs, the secondary switch is disabled. Q or Q 1 gate signal, through the control switch S 1~ S 6. Realize unidirectional power transmission of the converter; In the fourth fault-tolerant mode, the inductor current expression of the converter is: ， In the formula, is the leakage inductance current in the fourth fault-tolerant mode; Based on the inductor current expression of the converter, the transmission power of the converter is determined as: ， In the formula, is the transmission power of the converter in the fourth fault-tolerant mode.

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