A DBSRC-ISOP converter switch tube open circuit fault detection method

Abstract

This invention provides a method for detecting open-circuit faults in converter switching transistors, belonging to the field of power electronic converter fault diagnosis technology. The method employs a three-level diagnostic strategy: first, the fault module number is determined by the average value of the resonant capacitor voltage over a period of time; second, the diagonal group of the faulty transistor is preliminarily determined using the same average value; and finally, the specific switching transistor is precisely located by the difference between the voltage across the primary and secondary switches and the half-voltage of the input and output circuits. This invention requires no additional sensors, utilizing only the inherent electrical characteristics of the converter to complete fault detection and location. Simulation results show that this method can complete detection and location within one switching cycle after the fault occurs, accurately distinguishing open-circuit faults in all eight switching transistors on the primary and secondary sides, demonstrating significant engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of power electronic converter fault diagnosis technology, and in particular relates to a... A method for detecting open-circuit faults in a single transistor of a converter is proposed, which is based on the difference between the average value of the resonant voltage period and the voltage of the switching transistor. Background Technology

[0002] With the development of high-voltage, high-power applications such as rail transit and new energy power generation, bidirectional full-bridge series resonant (BLL) technology is increasingly being applied. Due to their excellent soft-switching characteristics and regulation performance, converters are often used as... The basic unit of a system.

[0003] Open-circuit faults in switching transistors are one of the main types of faults threatening the safe operation of converters. Unlike short-circuit faults, which can be quickly handled by hardware protection circuits, open-circuit faults are characterized by their high degree of concealment and small initial impact. However, if they cannot be detected and located in time, they will lead to decreased system efficiency, output voltage distortion, and even cascading faults. Therefore, it is of great significance to study a fast and accurate method for detecting and locating open-circuit faults in switching transistors.

[0004] Currently, for Numerous academic papers and patent documents have researched open-circuit fault detection in converter switching transistors, for example: Reference 1, “Chi Yuhang, Zhao Lu, Ge Qiongxuan, et al. Research on open circuit fault detection strategy of DBSRC converter switch tube [J]. Electrical Drive, 2025, 55(10): 81-87,” proposes a fault detection method based on the extreme deviation ratio of resonant capacitor voltage and bridge arm current, which can quickly locate the fault on the diagonal side. However, it has too many fault characteristics, complicated detection steps, and requires a large number of sensors, which is not conducive to engineering practice.

[0005] Document 2 "PEI A common fault detection strategy for converters requires adding a winding to the original circuit and comparing the voltage waveform of the added winding with the actual voltage. Fault detection is performed using the relationship between gate-level signals, but this method suffers from problems such as power derating, capacity loss, and hardware redundancy.

[0006] Reference 3, "Zhao Lu, Chi Yuhang, Cheng Shi, et al. Open-circuit fault location and detection system and method based on dual active bridge resonant converter [P]. Chinese Patent: CN202510505420.6, 2025," proposes a method for detecting open-circuit faults in dual active bridge resonant converters. The proposed open-circuit fault detection and location system and method analyzes the DC bias of the resonant capacitor voltage, the DC bias of the secondary resonant current, and the mean deviation of the voltages at the midpoints of the primary and secondary bridge arms to locate the fault. However, it uses too many sensors, increasing the hardware burden, and can only detect faults occurring in... Open circuit fault in the converter.

[0007] Reference 4, “W. Wang et al., 'A Fault-Tolerant Method of Submodule Fault Diagnosis and Redundant Cooperative Control for Subsea ISOP-Type DCConverters,' in IEEE Transactions on Power Electronics, vol. 41, no. 2, pp.2303-2316, Feb. 2026,” proposes a method for subsea... type A method for fault diagnosis and redundancy coordination control of converter submodules.

[0008] However, the methods described in the above literature still have the following shortcomings: 1. Existing methods are basically applied to or Few methods are applicable ; 2. Existing methods based on the transient characteristics of the midpoint voltage of the bridge arm rely on the transient process of the fault, and the characteristics disappear after the steady state. The detection window is too short and it is easily affected by noise. 3. Existing methods that can achieve precise positioning require the addition of a current sensor, which increases system cost and complexity and is not conducive to engineering applications. Summary of the Invention

[0009] The technical problem to be solved by this invention is the problem existing in the prior art as pointed out in the background art. Specifically, this invention provides a method based on the average value of the resonant capacitor voltage period and the voltage difference between the primary and secondary switching transistors. A method for detecting open-circuit faults in converter switching transistors is proposed. This method does not require additional sensors; it estimates the fault location simply by detecting the voltage of the resonant capacitor and the voltage of the primary and secondary switching transistors. This method can then be used for inverter fault-tolerant control, improving the stability of the grid-connected system without increasing costs.

[0010] The technical solution of the present invention is as follows.

[0011] A sort of The method for detecting open-circuit faults in converter switching transistors, the The converter topology is composed of The same The system is composed of modules, and any one of them is denoted as a module. , The module The voltage divider input capacitors and the primary side are connected in sequence. Bridge circuit, resonant branch, high-frequency transformer, secondary side It consists of a bridge circuit and an output capacitor. Each module The module string formed by the series connection of the voltage divider input capacitors is connected in parallel with a DC-side voltage source. Each module The output capacitors are all connected in parallel with a single output-side load; the resonant branch is composed of a resonant inductor and a resonant capacitor connected in series; the primary side... Bridge circuit and secondary side The bridge circuits all include four diodes with anti-parallel connection. Switching transistors, respectively denoted as switching transistors -Switching transistor Among them, the switching transistor Switching transistor Switching transistor Switching transistor For the upper bridge arm switch transistor, switch transistor Switching transistor Switching transistor Switching transistor For the lower bridge arm switching transistor; specifically, the switching transistor With switching transistor Switching transistor With switching transistor Each constitutes the primary edge The two arms of the bridge circuit, the switching transistor With switching transistor Switching transistor With switching transistor Each constitutes a secondary edge The two arms of the bridge circuit include the following steps: Step 1, sample each module The voltage across the resonant capacitor is denoted as the resonant voltage. Sampling modules switching transistor Voltage V at both ends S2i Switching transistor Voltage V at both endsS6i ; Step 2, for N Resonant voltage In each switching cycle T s Calculate its periodic average value to obtain N Average value of one resonant voltage cycle Based on the average value of the resonant voltage period and given secondary side fault threshold ,right N indivual Each module in the module performs a first-level fault diagnosis to identify the module that has an open-circuit fault; Step 3: For the faulty modules detected in Step 2, extract the switching transistors of the faulty modules from the data collected in Step 1. Voltage across terminals and switching transistor The voltages at both ends are marked as follows: and The average value of the switching transistor in each switching cycle is calculated to obtain the fault module switching transistor. Voltage period average and fault module switching transistor Voltage period average The faulty module switching transistor was calculated. voltage difference and fault module switching transistor voltage difference ; Step 4, give the primary edge fault threshold From step 2 N Extract the average resonant voltage cycle of the faulty module from the average resonant voltage cycle and mark it as... Perform second-level fault diagnosis; given the switching transistor voltage difference threshold and switching transistor voltage difference threshold According to the faulty module switching transistor voltage difference and fault module switching transistor voltage difference Perform the third-level fault diagnosis to locate the faulty switching transistor.

[0012] Preferably, the average value of the resonant voltage period in step 2 is... The formula for calculation is:

[0013] Where t is the running time; Preferably, the step 2 described above... N indivual The rules for the module to perform the first-level fault diagnosis are as follows: When all modules satisfy hour, The converter is operating normally without any faults; this test is now complete. When any module satisfies If this occurs, the module is determined to have an open-circuit fault; Record the modules that experience open-circuit faults.

[0014] Preferably, the fault module switching transistor in step 3 voltage difference and fault module switching transistor voltage difference The calculation formulas are as follows: , , In the formula, This is the voltage at the voltage divider input capacitor of the faulty module. This is the voltage at the output voltage of the faulty module.

[0015] Preferably, the rule for determining the second-level fault in step 4 is as follows: when If so, it is determined that the fault is caused by switch S2 or switch S3. when If so, it is determined that the fault is caused by switch S1 or switch S4. when If so, it is determined that the fault is caused by switch S5 or switch S8. when If so, it is determined that the fault is caused by switch S6 or switch S7. in, .

[0016] Preferably, the implementation rule for the third-level fault judgment in step 4 is as follows: When the second-level fault is determined to be a fault in switching transistor S1 or switching transistor S4: like If so, the fault is identified as an open circuit fault in switch S1; like If so, the fault is identified as an open circuit fault in switch S4; When the second-level fault is determined to be a fault in switching transistor S2 or switching transistor S3: like If so, the fault is identified as an open circuit fault in switch S2; like If so, the fault is identified as an open circuit fault in switch S3; When the second-level fault is determined to be a fault in switching transistor S5 or switching transistor S8: like If so, the fault is identified as an open circuit fault in switch S5; like If so, the fault is identified as an open circuit fault in the switching transistor S8. When the second-level fault is determined to be a fault in switching transistor S6 or switching transistor S7: like If so, the fault is identified as an open circuit fault in switch S6; like If so, the fault is identified as an open circuit fault in the switching transistor S7.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) No additional sensors are needed; fault detection and location can be completed based solely on the inherent electrical characteristics of the converter (resonant capacitor voltage and primary and secondary switch voltages), thus reducing system costs. (2) A two-level diagnostic strategy of “grading first and then locating” is adopted. The first level determines the fault module number by the average value of the resonant voltage cycle. The second level locates the fault module side and diagonal transistor by the average value of the resonant voltage cycle. The third level accurately locates the specific switching transistor by the voltage difference between the primary and secondary switching transistors. This solves the problem that the existing methods cannot distinguish the specific switching transistors in the same diagonal side. (3) The average value of the resonant voltage period is a steady-state characteristic quantity, which can continuously provide fault information during the steady-state stage of the fault, overcoming the shortcomings of the method that relies on transient processes, such as short detection window and susceptibility to noise interference. (4) Taking into account the characteristic differences between primary-side faults and secondary-side faults, different detection thresholds were set for each, which improved the reliability and accuracy of diagnosis. Attached Figure Description

[0018] Figure 1 As described in the embodiments of the present invention Topology diagram of the converter.

[0019] Figure 2 This is a flowchart illustrating the implementation process of the method of the present invention.

[0020] Figure 3 The switching transistor in module one of the embodiments of the present invention When an open-circuit fault occurs, the resonant voltage period of module one Waveform diagram.

[0021] Figure 4 The switching transistor in module one of the embodiments of the present invention When an open-circuit fault occurs, the resonant voltage period of module two is... Waveform diagram.

[0022] Figure 5 The switching transistor in module one of the embodiments of the present invention When an open circuit fault occurs, the faulty module switching transistor voltage difference Waveform of periodic average value.

[0023] Figure 6 The switching transistor in module one of the embodiments of the present invention When an open circuit fault occurs, the faulty module switching transistor voltage difference Waveform of periodic average value.

[0024] Figure 7 The switching transistor in module one of the embodiments of the present invention Location signal diagram when an open circuit fault occurs.

[0025] Figure 8 The switching transistor in module one of the embodiments of the present invention When an open-circuit fault occurs, the resonant voltage period of module one Waveform diagram.

[0026] Figure 9 The switching transistor in module one of the embodiments of the present invention When an open-circuit fault occurs, the period value of the resonant capacitor of module two Waveform diagram.

[0027] Figure 10 The switching transistor in module one of the embodiments of the present invention When an open circuit fault occurs, the faulty module switching transistor voltage difference Waveform of periodic average value.

[0028] Figure 11 The switching transistor in module one of the embodiments of the present invention When an open circuit fault occurs, the faulty module switching transistor voltage difference Waveform of periodic average value.

[0029] Figure 12 The switching transistor in module one of the embodiments of the present invention Location signal diagram when an open circuit fault occurs. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings.

[0031] Figure 1 As described in the embodiments of the present invention Topology diagram of the converter. Figure 1 It can be seen that the above The converter topology is composed of The same The system is composed of modules, and any one of them is denoted as a module. , The module The voltage divider input capacitors and the primary side are connected in sequence. Bridge circuit, resonant branch, high-frequency transformer, secondary side It consists of a bridge circuit and an output capacitor. Each module The module string formed by the series connection of the voltage divider input capacitors is connected in parallel with a DC-side voltage source. Each module The output capacitors are all connected in parallel with an output-side load. The resonant branch is composed of a resonant inductor and a resonant capacitor connected in series.

[0032] The original edge Bridge circuit and secondary side The bridge circuits all include four diodes with anti-parallel connection. Switching transistors, respectively denoted as switching transistors -Switching transistor Among them, the switching transistor Switching transistor Switching transistor Switching transistor These are the upper bridge arm switching transistors; the rest are the lower bridge arm switching transistors. Specifically, the switching transistors... With switching transistor Switching transistor With switching transistor Each constitutes the primary edge The two arms of the bridge circuit, the switching transistor With switching transistor Switching transistor With switching transistor Each constitutes a secondary edge The two arms of a bridge circuit.

[0033] Depend on Figure 1 As can be seen, the specific connection method of the 8 switching transistors is as follows: Switching transistors Source and switch The drains are connected to form the primary side. Bridge arm 1 of the bridge circuit, switching transistor Source and switch The drains are connected to form the primary side. Bridge arm 2 of the bridge circuit; switching transistor Source and switch The drains are connected to form the secondary side. Bridge arm 1 of the bridge circuit, switching transistor The source and primary side switching transistor The drains are connected to form the secondary side. Bridge arm 2 of the bridge circuit. Module i is connected as follows: voltage divider input capacitor and primary side. Bridge circuits in parallel, secondary side The bridge circuit and the output capacitor are connected in parallel, primary side The output of the bridge circuit is connected to the primary side of the high-frequency transformer via a resonant branch, and the secondary side of the high-frequency transformer is connected to the secondary side. The input terminal of the bridge circuit.

[0034] In addition, by Figure 1 As can be seen, in this embodiment, N=4. C1, C2, C3, and C4 are the voltage divider input capacitors of the four modules, and V1, V2, V3, and V4 are the voltages at the four voltage divider input capacitors, respectively. 01 C 02 C 03 C 04 These are the output capacitors of the four modules, and Vin is the DC-side voltage. It is a resonant inductor. T1 is the resonant capacitor, T2 is the high-frequency transformer, and R0 is the output-side load.

[0035] Figure 2 The flowchart illustrates the implementation of this invention. The converter switching transistor open-circuit fault detection method involves sampling the resonant voltage and the primary and secondary switching transistor voltage signals, calculating the periodic average value of characteristic quantities, calculating the voltage difference between the primary and secondary switching transistors, performing a third-level fault judgment and location, and finally outputting the fault transistor number.

[0036] Specifically, it includes the following steps: Step 1, sample each module The voltage across the resonant capacitor is denoted as the resonant voltage. Sampling modules switching transistor Voltage V at both ends S2i Switching transistor Voltage V at both ends S6i .

[0037] Step 2, for N Resonant voltage In each switching cycle T s Calculate its periodic average value to obtain N Average value of one resonant voltage cycle Based on the average value of the resonant voltage period and given secondary side fault threshold ,right N indivual Each module in the module performs a first-level fault diagnosis to identify the module that has an open-circuit fault; In this embodiment, the average value of the resonant voltage period is... The formula for calculation is:

[0038] Where t is the running time.

[0039] In this embodiment, the... N indivual The rules for the module to perform the first-level fault diagnosis are as follows: When all modules satisfy hour, The converter is operating normally without any faults; this test is now complete. When any module satisfies If this occurs, the module is determined to have an open-circuit fault; Record the modules that experience open-circuit faults.

[0040] Step 3: For the faulty modules detected in Step 2, extract the switching transistors of the faulty modules from the data collected in Step 1. Voltage across terminals and switching transistor The voltages at both ends are marked as follows: and The average value of the switching transistor in each switching cycle is calculated to obtain the fault module switching transistor. Average voltage period and fault module switching transistor Voltage period average The faulty module switching transistor was calculated. voltage difference and fault module switching transistor voltage difference .

[0041] In this embodiment, the fault module switching transistor voltage difference and fault module switching transistor voltage difference The calculation formulas are as follows:

[0042] , In the formula, This is the voltage at the voltage divider input capacitor of the faulty module. This is the voltage at the output voltage of the faulty module.

[0043] Step 4, give the primary edge fault threshold From step 2 NExtract the average resonant voltage cycle of the faulty module from the average resonant voltage cycle and mark it as... Perform second-level fault diagnosis; given the switching transistor voltage difference threshold and switching transistor voltage difference threshold According to the fault module switching transistor voltage difference and fault module switching transistor voltage difference Perform the third-level fault diagnosis to locate the faulty switching transistor.

[0044] In this embodiment, the rule for determining the second-level fault is: when If so, it is determined that the fault is caused by switch S2 or switch S3. when If so, it is determined that the fault is caused by switch S1 or switch S4. when If so, it is determined that the fault is caused by switch S5 or switch S8. when If so, it is determined that the fault is caused by switch S6 or switch S7.

[0045] in, .

[0046] In this embodiment, the implementation rule for the third-level fault judgment is as follows: When the second-level fault is determined to be a fault in switching transistor S1 or switching transistor S4: like If so, the fault is identified as an open circuit fault in switch S1; like If so, the fault is identified as an open circuit fault in switch S4; When the second-level fault is determined to be a fault in switching transistor S2 or switching transistor S3: like If so, the fault is identified as an open circuit fault in switch S2; like If so, the fault is identified as an open circuit fault in switch S3; When the second-level fault is determined to be a fault in switching transistor S5 or switching transistor S8: like If so, the fault is identified as an open circuit fault in switch S5; like If so, the fault is identified as an open circuit fault in switch S8; When the second-level fault is determined to be a fault in switching transistor S6 or switching transistor S7: like If so, the fault is identified as an open circuit fault in switch S6; like If so, the fault is identified as an open circuit fault in the switching transistor S7.

[0047] To demonstrate the beneficial effects of the present invention, simulations were performed.

[0048] Some parameters in the simulation are as follows: , , Switching frequency Transformer turns ratio , Set to 8V. Set to 1.6V. Set to 5V, threshold Set to 2V. At that time, the switching transistors of module one are set respectively. and switching transistor An open-circuit fault occurred in the switching transistor.

[0049] Figure 3 For module one switching transistor When an open-circuit fault occurs, the resonant voltage period of module one Waveform diagram. The diagram shows the waveform when no fault occurs. Keep it at 0, in the event of a fault After one switching cycle, the average resonant voltage periodically drops significantly negatively and exceeds the threshold. It can be preliminarily determined that the fault occurs in the switching transistor of module one. or .

[0050] Figure 4 The switching transistor in module one of the embodiments of the present invention When an open-circuit fault occurs, the resonant voltage period of module two is... Waveform diagram. The diagram shows the waveform when no fault occurs. It remains at 0, exhibits slight fluctuations after a fault occurs, but still stays near 0, with extreme values ​​not exceeding 0.15, and never exceeds the threshold. Simulations also show that the resonant voltage period values ​​of modules three and four are... , It also fluctuates around 0, and... Similarly, and it will never exceed the threshold. The attached diagrams will not be repeated here, therefore it can be determined that modules two, three, and four did not experience open circuit faults.

[0051] Figure 5 The switching transistor in module one of the embodiments of the present invention When an open circuit fault occurs, the faulty module switching transistor voltage difference Waveform of periodic average value. The graph shows that during normal operation... Approximately equal to 0, it plummeted rapidly after the malfunction occurred, and... The threshold is reached after one cycle. Therefore, it can be determined that the fault lies in the switching tube. .

[0052] Figure 6 The switching transistor in module one of the embodiments of the present invention When an open circuit fault occurs, the faulty module switching transistor voltage difference Waveform of periodic average value. The graph shows that for a considerable period after the fault occurred... All values ​​remain near 0, with extreme values ​​not exceeding 0.15, and never exceed the threshold. .

[0053] Figure 7 The switching transistor in module one of the embodiments of the present invention Location signal diagram when an open circuit fault occurs. The diagram shows that the fault occurs within 4 switching cycles (switching cycle is...). After that, the system integrates the three fault characteristic quantities, processes them, and outputs the fault tube number as 1.

[0054] Figure 8 The switching transistor in module one of the embodiments of the present invention When an open-circuit fault occurs, the resonant voltage period of module one Waveform diagram. The diagram shows the waveform when no fault occurs. Keep it at 0 after the fault occurs. After one switching cycle, the average value of the resonant voltage periodically increases rapidly and exceeds the threshold set by the secondary side. However, it never reaches the original edge threshold. Therefore, it can be preliminarily determined that the fault occurred in the diagonal tube of a secondary side of the module. or .

[0055] Figure 9 The switching transistor in module one of the embodiments of the present invention When an open-circuit fault occurs, the resonant voltage period of module two is... Waveform diagram. The diagram shows the waveform when no fault occurs. It remains at 0, exhibits slight fluctuations after a fault occurs, but still stays near 0, with extreme values ​​not exceeding 0.40, and never exceeds the threshold. Simulations also show that the resonant voltage period values ​​of modules three and four are... , It also fluctuates around 0, and... Similarly, and it will never exceed the threshold. The attached diagrams will not be repeated here, therefore it can be determined that modules two, three, and four did not experience open circuit faults.

[0056] Figure 10 The switching transistor in module one of the embodiments of the present invention When an open-circuit fault occurs, the primary-side switch of the faulty module... voltage difference Periodic average waveform diagram. The graph shows the switching transistor... voltage difference The value remained small for 10 switching cycles following the fault, with an extreme value of approximately 0.14, and never reached the threshold. .

[0057] Figure 11 The switching transistor in module one of the embodiments of the present invention When an open circuit fault occurs, the faulty module switching transistor voltage difference Periodic average waveform diagram. The graph shows the switching transistor... voltage difference The voltage drop rapidly exceeded the threshold γ within one switching cycle following the fault, indicating that the fault occurred in a secondary switch of the module. .

[0058] Figure 12 The switching transistor in module one of the embodiments of the present invention Location signal diagram when an open circuit fault occurs. The diagram shows that the fault occurs within 4 switching cycles (switching cycle is...). After that, the system integrates the three fault characteristic quantities, processes them, and outputs the fault tube number as 5.

Claims

1. A kind The method for detecting open-circuit faults in converter switching transistors, the The converter topology is composed of The same The system is composed of modules, and any one of them is denoted as a module. , The module The voltage divider input capacitors and the primary side are connected in sequence. Bridge circuit, resonant branch, high-frequency transformer, secondary side It consists of a bridge circuit and an output capacitor. Each module The module string formed by the series connection of the voltage divider input capacitors is connected in parallel with a DC-side voltage source. Each module The output capacitors are all connected in parallel with a single output-side load; the resonant branch is composed of a resonant inductor and a resonant capacitor connected in series; the primary side... Bridge circuit and secondary side The bridge circuits all include four diodes with anti-parallel connection. Switching transistors, respectively denoted as switching transistors -Switching transistor ,in, Switching transistor Switching transistor Switching transistor Switching transistor For the upper bridge arm switch transistor, switch transistor Switching transistor Switching transistor Switching transistor For the lower bridge arm switching transistor; specifically, the switching transistor With switching transistor Switching transistor With switching transistor Each constitutes the primary edge The two arms of the bridge circuit, the switching transistor With switching transistor Switching transistor With switching transistor Each constitutes a secondary edge The two arms of a bridge circuit; characterized by comprising the following steps: Step 1, sample each module The voltage across the resonant capacitor is denoted as the resonant voltage. Sampling modules switching transistor Voltage V at both ends S2i Switching transistor Voltage V at both ends S6i ; Step 2, for N Resonant voltage In each switching cycle T s Calculate its periodic average value to obtain N Average value of one resonant voltage cycle Based on the average value of the resonant voltage period and given secondary side fault threshold ,right N indivual Each module in the module performs a first-level fault diagnosis to identify the module that has an open-circuit fault; Step 3: For the faulty modules detected in Step 2, extract the switching transistors of the faulty modules from the data collected in Step 1. Voltage across terminals and switching transistor The voltages at both ends are marked as follows: and The average value of the switching transistor in each switching cycle is calculated to obtain the fault module switching transistor. Voltage period average and fault module switching transistor Average voltage period The faulty module switching transistor was calculated. voltage difference and fault module switching transistor voltage difference ; Step 4, give the primary edge fault threshold From step 2 N Extract the average resonant voltage cycle of the faulty module from the average resonant voltage cycle and mark it as... Perform second-level fault diagnosis; given the switching transistor voltage difference threshold and switching transistor voltage difference threshold According to the faulty module switching transistor voltage difference and fault module switching transistor voltage difference Perform the third-level fault diagnosis to locate the faulty switching transistor.

2. The one according to claim 1 A method for detecting open-circuit faults in converter switching transistors, characterized in that, The average value of the resonant voltage period in step 2 The formula for calculation is: Where t is the running time.

3. The one according to claim 1 A method for detecting open-circuit faults in converter switching transistors, characterized in that, Step 2 describes the following: N indivual The rules for the module to perform the first-level fault diagnosis are as follows: When all modules satisfy hour, The converter is operating normally without any faults; this test is now complete. When any module satisfies If this occurs, the module is determined to have an open-circuit fault; Record the modules that experience open-circuit faults.

4. The one according to claim 1 A method for detecting open-circuit faults in converter switching transistors, characterized in that, Step 3 describes the fault module switching transistor voltage difference and fault module switching transistor voltage difference The calculation formulas are as follows: ， ， In the formula, This is the voltage at the voltage divider input capacitor of the faulty module. This is the voltage at the output voltage of the faulty module.

5. The method according to claim 1 A method for detecting open-circuit faults in converter switching transistors, characterized in that, Step 4, the rules for the second-level fault diagnosis are: when If so, it is determined that the fault is caused by switch S2 or switch S3. when If so, it is determined that the fault is caused by switch S1 or switch S4. when If so, it is determined that the fault is caused by switch S5 or switch S8. when If so, it is determined that the fault is caused by switch S6 or switch S7. in, .

6. The method according to claim 5 A method for detecting open-circuit faults in converter switching transistors, characterized in that, The implementation rules for the third-level fault judgment described in step 4 are as follows: When the second-level fault is determined to be a fault in switching transistor S1 or switching transistor S4: like If so, the fault is identified as an open circuit fault in switch S1; like If so, the fault is identified as an open circuit fault in switch S4; When the second-level fault is determined to be a fault in switching transistor S2 or switching transistor S3: like If so, the fault is identified as an open circuit fault in switch S2; like If so, the fault is identified as an open circuit fault in switch S3; When the second-level fault is determined to be a fault in switching transistor S5 or switching transistor S8: like If so, the fault is identified as an open circuit fault in switch S5; like If so, the fault is identified as an open circuit fault in the switching transistor S8. When the second-level fault is determined to be a fault in switching transistor S6 or switching transistor S7: like If so, the fault is identified as an open circuit fault in switch S6; like If so, the fault is identified as an open circuit fault in the switching transistor S7.

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