Fault detection method and system for SVF multi-stage full-bridge sub-module in SLCC

Abstract

The invention discloses a fault detection method and system for an SVF multi-stage full-bridge sub-module in an SLCC, and the method comprises the steps: constructing a converter valve test model which comprises a converter valve, a valve control unit and a low-pressure pressurization unit; wherein the converter valve comprises a full-bridge sub-module; based on a valve tower structure, wiring complexity and test voltage safety, performing number optimization on series connection and parallel connection of full-bridge sub-modules, and setting test power supply voltage; and based on the topological structure of the full-bridge sub-modules, performing low-voltage pressurization test on the full-bridge sub-modules by using a low-voltage pressurization unit to obtain the working states of the full-bridge sub-modules, judging faults of the full-bridge sub-modules connected in series, and positioning fault positions. According to the method, the detection efficiency of the multi-stage full-bridge sub-module is improved, all the full-bridge sub-modules of the valve tower can be rapidly and accurately detected and diagnosed only through one-time wiring, the field handover test time is shortened, and SLCC direct-current power transmission project construction is supported.

Description

Technical Field

[0001] The present invention relates to the technical field of converter valve detection, and in particular to a fault detection method and system for an SVF multi-stage full-bridge submodule in a SLCC. Background Art

[0002] DC technology based on SLCC (Self-adaption Statcom and Line Commutation Converter, multi-source adaptive commutation converter) has the advantage of being able to improve the inherent defects of traditional LCC (Line Commutation Converter, grid commutation converter) DC transmission technology and reduce the risk of commutation failure to a certain extent, becoming a research hotspot in the field of flexible DC transmission.

[0003] In SLCC technology, the SVF (Static Var Filter) valve uses a full-bridge MMC (Modular Multilevel Converter) chain structure, which takes into account both harmonic filtering and reactive power compensation functions. However, the SVF's chain cascade topology is complex and the number of full-bridge sub-modules is huge. Existing on-site sub-module inspection methods mostly target individual half-bridge sub-modules in sequence, and it takes several weeks to complete all inspections. This not only consumes a lot of human resources and time costs, but also seriously affects the commissioning efficiency of SLCC projects and threatens the stable operation of the power grid. Using random inspections to inspect sub-modules will lead to safety risks of missed inspections, which will bring huge time and labor costs to regular inspections and maintenance.

[0004] The Chinese patent application with publication number CN113917251A and invention name "A low-voltage pressurization test system and control method for converter valves" can test submodules in batches. Unfortunately, this technology can only be used for batch testing of half-bridge submodules and cannot be effectively applied to the full-bridge submodules of existing SLCCs. The Chinese patent application with publication number CN112924838B and invention name "Modular converter chain, synthetic loop system, converter valve and control method" proposes a system and method for batch testing of converter valve submodules. The converter valve submodules can be charged and powered by a low-voltage power supply, thereby improving the efficiency of converter valve testing. However, there are still deficiencies in actual operation: after the test, there is a manual disconnection of the submodule bypass switch, which may cause the disconnection to be inadequate. Summary of the Invention

[0005] The purpose of the present invention is to provide a fault detection method and system for SVF multi-level full-bridge submodules in SLCC, improve the detection efficiency of multi-level full-bridge submodules, realize rapid and accurate detection and diagnosis of multi-level full-bridge submodules, shorten the on-site handover test time, and support the construction of SLCC direct current transmission projects.

[0006] The present invention adopts the following technical solution: a fault detection method for an SVF multi-stage full-bridge submodule in an SLCC, comprising the following steps:

[0007] S1. Construct a converter valve test model, which includes a converter valve, a valve control unit, and a low-voltage pressurization unit; wherein the converter valve includes a full-bridge submodule.

[0008] S2. Based on the valve tower structure, wiring complexity, and test voltage safety, optimize the number of series and parallel connections of the full-bridge sub-modules and set the test power supply voltage.

[0009] S3. Based on the topological structure of the full-bridge sub-module, a low-voltage pressurization unit is used to perform a low-voltage pressurization test on the full-bridge sub-module to obtain the working status of the full-bridge sub-module, judge the fault of the series-connected full-bridge sub-module, and locate the fault position; among them, the low-voltage pressurization test includes two full-bridge sub-module diode on-off tests, full-bridge sub-module starting voltage test, full-bridge sub-module communication test, full-bridge sub-module central control board and valve control VBC communication test, full-bridge sub-module static equalizing pressure test, full-bridge sub-module program version number test, full-bridge sub-module IGBT on-off test, and bypass switch protection action test.

[0010] Furthermore, in step S1 , the full-bridge sub-module includes a DC capacitor, a power unit, a full-bridge sub-module control unit, and a bypass switch; and the power unit includes an IGBT and a diode.

[0011] The low-voltage boosting unit includes a forward and reverse power supply and an energy supply network; wherein the energy supply network includes a diode, and the forward and reverse power supply includes a DC power supply and four control switches.

[0012] The valve control unit is connected to the converter valve through the full-bridge submodule control unit; the low-voltage boosting unit is connected to the converter valve through a DC capacitor.

[0013] Furthermore, in the forward and reverse power supplies, the positive pole of the DC power supply is respectively connected to one end of the first control switch S1 and one end of the fourth control switch S4, the negative pole of the DC power supply is respectively connected to one end of the second control switch S2 and one end of the third control switch S3, the first output end of the DC power supply is respectively connected to the other end of the first control switch S1 and the other end of the third control switch S3, and the second output end of the DC power supply is respectively connected to the other end of the second control switch S2 and the other end of the fourth control switch S4.

[0014] The DC power supply switches the forward power supply and the reverse power supply through four control switches. The DC power supply range is 100V to 4000V, and the maximum DC power supply power is 4kW.

[0015] Furthermore, in step S2, the M full-bridge submodules in the valve tower are divided into n groups, each group having m full-bridge submodules, the m full-bridge submodules in each group are connected in series to obtain n series valve groups, and the n series valve groups are connected in parallel.

[0016] The IGBT in the full-bridge sub-module is represented by VTk-ij, the diode is represented by VDk-ij, and the DC capacitor is represented by Ck-i, where k represents the kth series valve group, i represents the i-th full-bridge sub-module in the kth series valve group, and j represents the j-th position of the upper and lower tubes of the semiconductor element in the full-bridge sub-module.

[0017] Set the test voltage U1 of each full-bridge submodule, then the test power supply voltage is nU1, and the starting voltage of the full-bridge submodule is U N , U1=1.5U N .

[0018] Furthermore, in step S3, in the low-voltage boosting unit, the first control switch S1 and the second control switch S2 are closed, and the power supply is switched to 4000V forward power supply, which is the first power supply state; the third control switch S3 and the fourth control switch S4 are closed, and the power supply is switched to 4000V reverse power supply, which is the second power supply state.

[0019] Before using the low-voltage pressurization unit to perform a low-voltage pressurization test on the full-bridge sub-module, a test safety voltage should be selected. The test safety voltage should be less than 20%-50% of the rated voltage of the full-bridge sub-module and less than 16 times the maximum withstand voltage of the semiconductor component.

[0020] Furthermore, in step S3, performing a low-pressure pressurization test includes the following:

[0021] When in the first power supply state, the first full-bridge sub-module diode continuity test is performed, and the diodes VDk-i2 and VDk-i3 of the full-bridge sub-module are subjected to continuity test.

[0022] Then carry out full-bridge sub-module startup voltage test, full-bridge sub-module communication test, full-bridge sub-module central control board and valve control VBC communication test, full-bridge sub-module static equalizing voltage test, full-bridge sub-module program version number test and full-bridge sub-module IGBT on-off test.

[0023] The voltage of the DC capacitor is discharged to 0V through the voltage balancing resistor. At this time, the power supply is switched to the second power supply state to perform the second full-bridge sub-module diode continuity test, and the full-bridge sub-module diodes VDk-i1 and VDk-i4 are tested for continuity.

[0024] Finally, perform the bypass switch protection action test.

[0025] Furthermore, in the on-off test of the diodes of the full-bridge sub-module, the DC power supply is started and the control switch is closed. The DC capacitor is charged by the DC power supply, and a group of diodes of the full-bridge sub-module in the series valve group are tested for on-off. When the voltage of the DC capacitor can be charged to the preset voltage, it indicates that there is no fault in the diodes.

[0026] In the full-bridge submodule starting voltage test, the starting voltage of the full-bridge submodule is tested using valve control. When the voltage of the DC capacitor of the full-bridge submodule in the series valve group reaches 500V, the full-bridge submodule can start normally, indicating that there is no fault in the starting voltage of the full-bridge submodule.

[0027] In the communication test between the full-bridge sub-modules, when communication is established between the full-bridge sub-module and the valve control and there is no communication frame loss, it indicates that there is no fault in the communication between the full-bridge sub-modules.

[0028] In the communication test between the central control board of the full-bridge submodule and the valve control VBC, the valve control is used to test the communication function between the central control board of the full-bridge submodule and the valve control VBC. When no communication abnormality message appears, it indicates that there is no fault in the communication between the central control board of the full-bridge submodule and the valve control VBC.

[0029] In the static voltage balancing test of the full-bridge sub-module, valve control is used to test the static voltage balancing of the full-bridge sub-module. When the voltage of the DC capacitor of the full-bridge sub-module in the series valve group reaches 500V and the voltage of each full-bridge sub-module is within the range of 500V±30V, it indicates that the static voltage balancing of the full-bridge sub-module is fault-free.

[0030] In the full-bridge submodule program version number test, the valve control is used to test the program version number of the full-bridge submodule. When the program version number of the full-bridge submodule is correct, it indicates that the program version number of the full-bridge submodule is fault-free.

[0031] In the full-bridge sub-module IGBT turn-on and turn-off test, the DC capacitor is discharged by switching the control switch, and the valve control is used to send a turn-on signal to the IGBT. When the IGBT receives the turn-on signal, it indicates that there is no fault in the turn-on and turn-off of the full-bridge sub-module IGBT.

[0032] During the bypass switch protection action test, the valve control sends a bypass switch conduction signal. When the bypass switch is closed, it indicates that the bypass switch protection action is fault-free.

[0033] Furthermore, the present invention also proposes a fault detection system for the SVF multi-stage full-bridge submodule in the SLCC, comprising:

[0034] The model building module is used to build a converter valve test model, which includes a converter valve, a valve control unit and a low-pressure pressurizing unit; wherein the converter valve includes a full-bridge submodule.

[0035] The structure optimization module is used to optimize the number of series and parallel connections of full-bridge sub-modules based on the valve tower structure, wiring complexity and test voltage safety, and set the test power supply voltage.

[0036] The fault testing module is used to perform low-voltage pressurization testing on the full-bridge sub-module based on the topological structure of the full-bridge sub-module using a low-voltage pressurization unit to obtain the working status of the full-bridge sub-module, judge the fault of the series-connected full-bridge sub-module, and locate the fault position; among them, the low-voltage pressurization test includes two full-bridge sub-module diode on-off tests, full-bridge sub-module starting voltage test, full-bridge sub-module communication test, full-bridge sub-module central control board and valve control VBC communication test, full-bridge sub-module static equalizing pressure test, full-bridge sub-module program version number test, full-bridge sub-module IGBT on-off test, and bypass switch protection action test.

[0037] Furthermore, the present invention also proposes an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the fault detection method of the SVF multi-stage full-bridge sub-module in the SLCC are implemented.

[0038] Furthermore, the present invention also proposes a computer-readable storage medium, which stores a computer program. When the computer program is run by a processor, it executes the fault detection method of the SVF multi-level full-bridge sub-module in the SLCC.

[0039] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0040] Aiming at the complex structural characteristics of full-bridge submodules, the present invention can quickly and accurately detect and diagnose all full-bridge submodules of the valve tower through a single wiring after serial and parallel wiring, shortening the on-site handover test time and supporting the construction of SLCC DC transmission projects. In addition, through the design of test items and processes, faulty full-bridge submodules can be quickly screened and faulty components can be located. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is an overall implementation flow chart of the present invention.

[0042] Figure 2 It is a structural diagram of the converter valve test model of the present invention.

[0043] Figure 3 This is a wiring diagram of the full-bridge submodule of the present invention.

[0044] Figure 4 Schematic diagram of the charging circuit of the full-bridge submodule of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0046] To achieve the above objectives, the present invention proposes a fault detection method for SVF multi-stage full-bridge submodule in SLCC, such as Figure 1 The specific steps are as follows:

[0047] S1. Construct a converter valve test model, such as Figure 2 As shown, the model includes a converter valve, a valve control unit and a low-voltage boosting unit; wherein the converter valve includes a full-bridge submodule; specifically:

[0048] The full-bridge submodule includes a DC capacitor, a power unit, a full-bridge submodule control unit and a bypass switch; the power unit includes an IGBT and a diode.

[0049] The low-voltage boosting unit includes a forward and reverse power supply and an energy supply network; wherein, the energy supply network includes at least two diodes, and the forward and reverse power supply includes a DC power supply and four control switches to control the flow direction of the DC power supply, and the power supply function is divided into a forward test power supply and a reverse test power supply through the control switch.

[0050] The valve control unit is connected to the converter valve through the full-bridge submodule control unit; the low-voltage boosting unit is connected to the converter valve through a DC capacitor.

[0051] In the forward and reverse power supplies, the positive pole of the DC power supply is respectively connected to one end of the first control switch S1 and one end of the fourth control switch S4, the negative pole of the DC power supply is respectively connected to one end of the second control switch S2 and one end of the third control switch S3, the first output end of the DC power supply is respectively connected to the other end of the first control switch S1 and the other end of the third control switch S3, and the second output end of the DC power supply is respectively connected to the other end of the second control switch S2 and the other end of the fourth control switch S4.

[0052] The output of the forward and reverse power supply is connected to the emitter of the second IGBT of the first full-bridge submodule of the first series valve group via the first control switch S1. The collector of the third IGBT of the first full-bridge submodule of the first series valve group is connected to the emitter of the second IGBT of the second full-bridge submodule of the first series valve group. This connection is repeated until the collector of the third IGBT of the last full-bridge submodule of the first series valve group is connected to the negative electrode of the forward and reverse power supply. This connection is repeated for the remaining series valve groups and connected to the power supply.

[0053] The DC power supply switches the forward power supply and the reverse power supply through four control switches. The DC power supply range is 100V to 4000V, and the maximum DC power supply power is 4kW.

[0054] S2, such as Figure 3 As shown in the figure, based on the valve tower structure, wiring complexity and test voltage safety, the number of series and parallel connections of the full-bridge submodules is optimized, and the test power supply voltage is set; specifically:

[0055] The SVF valve tower at a certain station is installed using floor-standing support. A single valve tower has 5 floors and a total of 72 full-bridge sub-modules, with 16 full-bridge sub-modules on each floor from the 1st to the 4th floor and 8 full-bridge sub-modules on the 5th floor.

[0056] If all connections are made in series, the test wiring will be less and the test time will be saved, but the test voltage will increase, which will pose a safety risk. If all connections are made in parallel, the test voltage will be lower, but the test wiring will be more and the test time will be increased. Therefore, a combination of series and parallel connections is selected.

[0057] Based on the valve tower structure, 4, 8, or 16 full-bridge submodules can be selected and connected in series to form a series valve group.

[0058] The wiring method for connecting four full-bridge submodules to a series valve group is more complex, with a lower test voltage of 2000V, which is safe, but the test time is longer. The wiring method for connecting eight full-bridge submodules to a series valve group is more complex, with a moderate test voltage of 4000V, which is safe, and the test time is shorter. The wiring method for connecting 16 full-bridge submodules to a series valve group is simpler, with a higher test voltage of 8000V, which is unsafe due to excessively high test voltage, but the test time is shorter.

[0059] In summary, the eight full-bridge submodules on each layer of the valve tower are connected in series to form a series valve group, and then the nine series valve groups are connected in parallel.

[0060] The IGBT in the full-bridge sub-module is represented by VTk-ij, the diode is represented by VDk-ij, and the DC capacitor is represented by Ck-i, where k represents the kth series valve group, i represents the i-th full-bridge sub-module in the kth series valve group, and j represents the j-th position of the upper and lower tubes of the semiconductor element in the full-bridge sub-module.

[0061] Each layer of valve modules is connected in a "port" pattern, with each layer connected in a "Z" pattern. The valve sections are connected by busbars. ①-⑩ in the diagram indicate the numbering of the two shared wooden signs and the valve module wiring ports. Only five positive power supply wires (1, 3, 5, 7, 9) and five negative power supply wires (2, 4, 6, 8, 10) are required to complete the wiring of nine series valve groups. Each positive and negative power supply wire has a switch in the test device. When performing the above test, the switches are closed in the following order: 1, 2-2, 3-3, 4-4, 5-5, 6-6, 7-7, 8-8, 9-9, 10.

[0062] At the same time, only one switch on the positive and negative poles of the busbar is closed, and only the single-channel sub-module is tested.

[0063] The test voltage of each full-bridge submodule is set to 500V, and the test power supply voltage is 4kV.

[0064] S3. Based on the topological structure of the full-bridge submodule, a low-voltage pressurization unit is used to perform a low-voltage pressurization test on the series valve group to obtain the working status of the full-bridge submodule, determine the fault of the series valve group, and locate the fault location. The low-voltage pressurization test includes two full-bridge submodule diode on-off tests, a full-bridge submodule starting voltage test, a full-bridge submodule inter-module communication test, a full-bridge submodule central control board and valve control VBC communication test, a full-bridge submodule static equalizing pressure test, a full-bridge submodule program version number test, a full-bridge submodule IGBT on-off test, and a bypass switch protection action test.

[0065] If any one of the low-pressure pressurization tests fails, it indicates that there is a problem with one or more full-bridge sub-modules in the series valve group. Except for the full-bridge sub-module diode continuity test, all other tests can use valve control to find out how many full-bridge sub-modules in the series valve group are faulty. Specifically:

[0066] In the low-voltage boosting unit, the first control switch S1 and the second control switch S2 are closed, and the power supply is switched to 4000V forward power supply, which is the first power supply state; the third control switch S3 and the fourth control switch S4 are closed, and the power supply is switched to 4000V reverse power supply, which is the second power supply state.

[0067] Before using the low-voltage pressurization unit to perform a low-voltage pressurization test on the full-bridge sub-module, a test safety voltage should be selected. The test safety voltage should be less than 20%-50% of the rated voltage of the full-bridge sub-module and less than 16 times the maximum withstand voltage of the semiconductor component.

[0068] In the full-bridge submodule diode continuity test, the DC power supply is started and the control switch is closed. The DC power supply is used to charge the DC capacitor. The continuity test of a pair of diodes in the full-bridge submodule in the series valve group is performed. When the voltage of the DC capacitor can be charged to the preset voltage, it indicates that the diodes are not faulty. Among them, a pair of diodes is defined as the full-bridge submodule VT i1 VT i4 or VT i2 VT i3 .

[0069] In the full-bridge submodule starting voltage test, the starting voltage of the full-bridge submodule is tested using valve control. When the voltage of the DC capacitor of the full-bridge submodule in the series valve group reaches 500V, the full-bridge submodule can start normally, indicating that there is no fault in the starting voltage of the full-bridge submodule.

[0070] In the communication test between full-bridge sub-modules, when the voltage of the DC capacitor of the full-bridge sub-module in the series valve group reaches 500V, when communication is established between the full-bridge sub-module and the valve control without communication frame loss, it indicates that there is no fault in the communication between the full-bridge sub-modules.

[0071] During the communication test between the central control board of the full-bridge submodule and the valve-controlled VBC, when the voltage of the DC capacitor of the full-bridge submodule in the series valve group reaches 500V, the valve control is used to test the communication function between the central control board of the full-bridge submodule and the valve-controlled VBC. When no abnormal communication message appears, it indicates that there is no fault in the communication between the central control board of the full-bridge submodule and the valve-controlled VBC.

[0072] In the static voltage balancing test of the full-bridge sub-module, when the voltage of the DC capacitor of the full-bridge sub-module in the series valve group reaches 500V, the static voltage balancing of the full-bridge sub-module is tested using valve control. When the voltage of the DC capacitor of the full-bridge sub-module in the series valve group reaches 500V and the voltage of each full-bridge sub-module is within the range of 500V±30V, it indicates that the static voltage balancing of the full-bridge sub-module is fault-free.

[0073] During the full-bridge sub-module program version number test, when the voltage of the DC capacitor of the full-bridge sub-module in the series valve group reaches 500V, the valve control is used to test the program version number of the full-bridge sub-module. When the program version number of the full-bridge sub-module is correct, it indicates that there is no fault in the program version number of the full-bridge sub-module.

[0074] During the full-bridge sub-module IGBT on-off test, when the voltage of the DC capacitor of the full-bridge sub-module in the series valve group reaches 500V, the DC capacitor is discharged by switching the control switch, and the valve control is used to send a conduction signal to the IGBT. When the IGBT receives the conduction signal, it indicates that there is no fault in the on-off of the full-bridge sub-module IGBT.

[0075] During the bypass switch protection action test, when the voltage of the DC capacitor of the full-bridge sub-module in the series valve group reaches 500V, the valve control sends a bypass switch conduction signal. Manual inspection is performed to see whether the bypass switch is closed. When the bypass switch is closed, it indicates that the bypass switch protection action is normal.

[0076] When in the first power state, the first full-bridge submodule diode continuity test is performed, and the diodes VDk-i2 and VDk-i3 of the full-bridge submodule are tested for continuity, where k = 1, 2, 3, 4, 5, 6, 7, 8, 9; i = 1, 2, 3, 4, 5, 6, 7, 8. Figure 4 As shown, the forward DC power flows through the first control switch S1 into the series valve group composed of 8 full-bridge submodules in series, and passes through VDk-12, C1, VDk-13 of the series submodule No. 1 and VDk-22, C2, VDk-23 of the series submodule No. 2 in the series valve group in sequence, until it passes through the 8 full-bridge submodules and then passes through the second control switch S2 and the third control switch S3, and the diodes VDk-i2 and VDk-i3 in the control switches and full-bridge submodules are tested for current flow (where k = 1, 2, 3, 4, 5, 6, 7, 8, 9; i = 1, 2, 3, 4, 5, 6, 7, 8).

[0077] If the above full-bridge sub-module diode on-off test does not detect a fault, after one power-on, the full-bridge sub-module startup voltage test, the full-bridge sub-module communication test, the full-bridge sub-module central control board and valve control VBC communication test, the full-bridge sub-module static equalizing voltage test, the full-bridge sub-module program version number test and the full-bridge sub-module IGBT on-off test are performed.

[0078] If the above full-bridge sub-module test does not detect a fault, after the above test, the voltage of the DC capacitor is discharged to 0V through the voltage balancing resistor. At this time, the power supply is switched to the second power supply state to perform a second full-bridge sub-module diode continuity test, and the full-bridge sub-module diodes VDk-i1 and VDk-i4 are tested for continuity.

[0079] Finally, perform the bypass switch protection action test.

[0080] The present invention also provides a fault detection system for SVF multi-stage full-bridge submodules in SLCC, comprising a model building module, a structural optimization module, a fault testing module, and a computer program executable on a processor. It should be noted that each module in the above system corresponds to the specific steps of the method provided in the present invention, and has the corresponding functional modules and beneficial effects of the method. For technical details not fully described in this embodiment, please refer to the method provided in the present invention.

[0081] An embodiment of the present invention further provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable by the processor. It should be noted that when the processor executes the computer program, it corresponds to the specific steps of the method provided in the embodiment of the present invention and has the corresponding functional modules and beneficial effects of the method. For technical details not fully described in this embodiment, please refer to the method provided in the embodiment of the present invention.

[0082] The present invention also provides a computer-readable storage medium storing a computer program. It should be noted that when executed by a processor, the computer program corresponds to the specific steps of the method provided in the present invention and has the corresponding functional modules and beneficial effects. For technical details not fully described in this embodiment, please refer to the method provided in the present invention.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fault detection method for SVF multi-stage full-bridge submodule in SLCC, characterized in that: include: S1. Construct a converter valve test model, which includes a converter valve, a valve control unit, and a low-pressure pressurizing unit; The converter valve includes a full-bridge submodule; S2. Based on the valve tower structure, wiring complexity, and test voltage safety, optimize the number of series and parallel connections of the full-bridge submodules and set the test power supply voltage. S3. Based on the topological structure of the full-bridge sub-module, a low-voltage pressurization unit is used to perform a low-voltage pressurization test on the full-bridge sub-module to obtain the working status of the full-bridge sub-module, judge the fault of the series-connected full-bridge sub-module, and locate the fault position; among them, the low-voltage pressurization test includes two full-bridge sub-module diode on-off tests, full-bridge sub-module starting voltage test, full-bridge sub-module communication test, full-bridge sub-module central control board and valve control VBC communication test, full-bridge sub-module static equalizing pressure test, full-bridge sub-module program version number test, full-bridge sub-module IGBT on-off test, and bypass switch protection action test.

2. The fault detection method for the SVF multi-stage full-bridge submodule in the SLCC according to claim 1 is characterized in that: In step S1, the full-bridge submodule includes a DC capacitor, a power unit, a full-bridge submodule control unit, and a bypass switch; the power unit includes an IGBT and a diode; The low-voltage boosting unit includes a forward and reverse power supply and an energy supply network; wherein the energy supply network includes a diode, and the forward and reverse power supply includes a DC power supply and four control switches; The valve control unit is connected to the converter valve through the full-bridge submodule control unit; the low-voltage boosting unit is connected to the converter valve through a DC capacitor.

3. The fault detection method for the SVF multi-stage full-bridge submodule in the SLCC according to claim 2, characterized in that: In the forward and reverse power supplies, the positive electrode of the DC power supply is connected to one end of the first control switch S1 and one end of the fourth control switch S4, respectively; the negative electrode of the DC power supply is connected to one end of the second control switch S2 and one end of the third control switch S3, respectively; the first output end of the DC power supply is connected to the other end of the first control switch S1 and the other end of the third control switch S3, respectively; and the second output end of the DC power supply is connected to the other end of the second control switch S2 and the other end of the fourth control switch S4, respectively; The DC power supply switches the forward power supply and the reverse power supply through four control switches. The DC power supply range is 100V to 4000V, and the maximum DC power supply power is 4kW.

4. The fault detection method for the SVF multi-stage full-bridge submodule in the SLCC according to claim 3 is characterized in that: In step S2, the M full-bridge submodules in the valve tower are divided into n groups, each group having m full-bridge submodules, the m full-bridge submodules in each group are connected in series to obtain n series valve groups, and the n series valve groups are connected in parallel; In the full-bridge submodule, the IGBT is represented by VTk-ij, the diode is represented by VDk-ij, and the DC capacitor is represented by Ck-i, where k represents the kth series valve group, i represents the i-th full-bridge submodule in the kth series valve group, and j represents the j-th position of the upper and lower tubes of the semiconductor components in the full-bridge submodule; Set the test voltage U1 of each full-bridge submodule, then the test power supply voltage is nU1, and the starting voltage of the full-bridge submodule is U N , U1=1.5U N .

5. The fault detection method for the SVF multi-stage full-bridge submodule in the SLCC according to claim 4 is characterized in that: In step S3, in the low-voltage pressurizing unit, the first control switch S1 and the second control switch S2 are closed, switching to a 4000V forward power supply, which is the first power supply state; the third control switch S3 and the fourth control switch S4 are closed, switching to a 4000V reverse power supply, which is the second power supply state; Before using the low-voltage pressurization unit to perform a low-voltage pressurization test on the full-bridge sub-module, a test safety voltage should be selected. The test safety voltage should be less than 20%-50% of the rated voltage of the full-bridge sub-module and less than 16 times the maximum withstand voltage of the semiconductor component.

6. The fault detection method for SVF multi-stage full-bridge submodule in SLCC according to claim 5, characterized in that: In step S3, the low-pressure pressurization test includes the following: When in the first power supply state, the first full-bridge submodule diode continuity test is performed, and the diodes VDk-i2 and VDk-i3 of the full-bridge submodule are subjected to continuity test; Then perform full-bridge submodule startup voltage test, full-bridge submodule communication test, full-bridge submodule central control board and valve control VBC communication test, full-bridge submodule static equalizing voltage test, full-bridge submodule program version number test and full-bridge submodule IGBT turn-on and turn-off test; Discharge the voltage of the DC capacitor to 0V through the voltage balancing resistor. Then switch to the second power supply state to perform the second full-bridge sub-module diode continuity test, and perform the continuity test on the full-bridge sub-module diodes VDk-i1 and VDk-i4. Finally, perform the bypass switch protection action test.

7. The fault detection method for SVF multi-stage full-bridge submodule in SLCC according to claim 4, characterized in that: In the full-bridge submodule diode continuity test, the DC power supply is started and the control switch is closed. The DC power supply is used to charge the DC capacitor. The continuity test of a group of diodes in the full-bridge submodule in the series valve group is performed. When the voltage of the DC capacitor can be charged to the preset voltage, it indicates that the diode is not faulty. In the full-bridge submodule starting voltage test, the starting voltage of the full-bridge submodule is tested using valve control. When the voltage of the DC capacitor of the full-bridge submodule in the series valve group reaches 500V, the full-bridge submodule can start normally, indicating that the starting voltage of the full-bridge submodule is normal. In the communication test between full-bridge submodules, when communication is established between the full-bridge submodule and the valve control and there is no communication frame loss, it indicates that there is no fault in the communication between the full-bridge submodules; In the communication test between the central control board of the full-bridge submodule and the valve control VBC, the valve control is used to test the communication function between the central control board of the full-bridge submodule and the valve control VBC. If no abnormal communication message appears, it indicates that there is no fault in the communication between the central control board of the full-bridge submodule and the valve control VBC. In the static voltage balancing test of the full-bridge submodule, valve control is used to test the static voltage balancing of the full-bridge submodule. When the voltage of the DC capacitor of the full-bridge submodule in the series valve group reaches 500V and the voltage of each full-bridge submodule is within the range of 500V±30V, it indicates that the static voltage balancing of the full-bridge submodule is normal. In the full-bridge submodule program version number test, the valve control is used to test the program version number of the full-bridge submodule. When the program version number of the full-bridge submodule is correct, it indicates that there is no fault in the program version number of the full-bridge submodule; In the full-bridge submodule IGBT on-off test, the DC capacitor is discharged by switching the control switch, and the valve control is used to send a conduction signal to the IGBT. When the IGBT receives the conduction signal, it indicates that there is no fault in the full-bridge submodule IGBT on-off. During the bypass switch protection action test, the valve control sends a bypass switch conduction signal. When the bypass switch is closed, it indicates that the bypass switch protection action is fault-free.

8. A system for the fault detection method of the SVF multi-stage full-bridge submodule in the SLCC according to claim 1, characterized in that: include: A model building module is used to build a converter valve test model, which includes a converter valve, a valve control unit and a low-pressure pressurizing unit; The converter valve includes a full-bridge submodule; The structure optimization module is used to optimize the number of series and parallel connections of full-bridge submodules based on the valve tower structure, wiring complexity, and test voltage safety, and to set the test power supply voltage; The fault testing module is used to perform low-voltage pressurization testing on the full-bridge sub-module based on the topological structure of the full-bridge sub-module using a low-voltage pressurization unit to obtain the working status of the full-bridge sub-module, judge the fault of the series-connected full-bridge sub-module, and locate the fault position; among them, the low-voltage pressurization test includes two full-bridge sub-module diode on-off tests, full-bridge sub-module starting voltage test, full-bridge sub-module communication test, full-bridge sub-module central control board and valve control VBC communication test, full-bridge sub-module static equalizing pressure test, full-bridge sub-module program version number test, full-bridge sub-module IGBT on-off test, and bypass switch protection action test.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method for detecting a fault of an SVF multi-stage full-bridge submodule in an SLCC according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the fault detection method for the SVF multi-level full-bridge sub-module in the SLCC according to any one of claims 1 to 7 is executed.

Images