Reliability test method and device for bypass switch of submodule of flexible direct current converter valve

Abstract

The invention discloses a reliability test method and device for a bypass switch of a flexible DC converter valve submodule, and relates to the technical field of flexible DC power transmission, and the method comprises the steps: constructing a test loop of the bypass switch based on the working condition of the flexible DC converter valve submodule at an overvoltage fault point, the test loop comprises a first pre-charging loop and an isolation switch thereof, a first capacitor and a discharge resistor thereof, an IGBT, a diode, a second pre-charging loop and an isolation switch thereof, a second capacitor and a discharge resistor thereof, an air-core reactor and a bypass switch. The IGBT is switched on after the capacitors are pre-charged, and the IGBT is switched off when the voltage of the first capacitor is smaller than the discharge termination voltage; when the voltage of the second capacitor is larger than the voltage of the fault point, the bypass switch is closed, waveform data of voltage and current of each element in the test process are obtained and analyzed, and a reliability test result of the bypass switch is obtained. The problem that an existing test scheme is low in accuracy is solved, and the accuracy of the bypass switch reliability test is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible HVDC transmission, in particular to a reliability test method and device for a bypass switch of a flexible HVDC converter valve sub-module. BACKGROUND

[0002] The flexible HVDC transmission adopts a MMC (Modular Multilevel Converter) topology converter valve to realize high-quality and high-flexibility power conversion between high-voltage AC and high-voltage DC, and plays a key role in new power system applications such as clean energy ultra-long distance transmission, asynchronous grid interconnection, flexible multi-terminal interconnection and deep-sea new energy transmission. The EHV flexible HVDC converter valve is in the EHV DC line, which requires extremely high reliability and availability, and usually does not allow the line to stop running due to the tripping of the converter valve caused by a single fault. The MMC sub-module (SM) is the smallest functional unit of the MMC topology, which may cause sub-module overvoltage under some unknown cause faults or failure modes, and further risks the stable operation of the converter valve. The bypass switch, as a key first-level protection under the sub-module overvoltage fault mode, needs to act reliably when a fault occurs to ensure that the EHV flexible HVDC converter valve can continue to operate without tripping under a single sub-module fault. If the bypass switch is triggered in time when the sub-module fails, the fault point can be bypassed and the impact of the fault can be limited to the fault module itself. Since the bypass switch is in a long-term split maintenance state during the operation of the converter valve, the trigger circuit of the bypass switch is also in a long-term inaction state, and it is not easy to find its potential functional fault point. Therefore, it is necessary to fully verify the ability of the bypass switch to act reliably before the converter valve is put into operation.

[0003] However, the bypass switch reliability test scheme in the prior art usually does not have related fault simulation conditions, resulting in low accuracy. SUMMARY

[0004] To solve the above technical problems, the present application provides a reliability test method and device for a bypass switch of a flexible HVDC converter valve sub-module, which can accurately simulate the working condition of the bypass switch when the bypass switch acts as a first-level protection when the sub-module in the EHV flexible HVDC converter valve fails due to overvoltage, and improves the accuracy of the reliability test of the bypass switch.

[0005] The embodiment of the present application provides a reliability test method of a flexible direct current valve submodule bypass switch, comprising: constructing a test loop of the bypass switch based on the working condition of the flexible direct current valve submodule at an overvoltage fault point; the test loop comprises: a first pre-charging loop, a first isolation switch, a first capacitor, a first discharge resistor, an IGBT (Insulate-Gate Bipolar Transistor), a diode, a second pre-charging loop, a second isolation switch, a second capacitor, a second discharge resistor, an air-core reactor and a bypass switch; Pre-charging is performed on the first capacitor and the second capacitor; The IGBT is turned on until the voltage of the first capacitor is less than a preset termination discharge voltage, and the IGBT is turned off; when the voltage of the second capacitor is greater than a preset fault point voltage, the bypass switch is closed; When it is monitored that the test loop is discharged, waveform data of voltage and current of each element in the test loop in a test process is obtained, and the waveform data is analyzed to obtain a reliability test result of the bypass switch.

[0006] As an improvement of the above scheme, the test loop specifically comprises: The first pre-charging loop is connected with the first capacitor through the first isolation switch, and is used for pre-charging the first capacitor; and the first capacitor is connected in parallel with the first discharge resistor; The second pre-charging loop is connected with the second capacitor through the second isolation switch, and is used for pre-charging the second capacitor; and the second capacitor is connected in parallel with the second discharge resistor; The collector of the IGBT is connected with the first capacitor, and the emitter of the IGBT is connected with the negative electrode of the diode; one end of the second capacitor is connected with the positive electrode of the diode, and the other end of the second capacitor is connected with one end of the bypass switch; the other end of the bypass switch is connected with the negative electrode of the diode; and the air-core reactor is connected in parallel with the bypass switch.

[0007] As an improvement of the above scheme, the test loop of the bypass switch is constructed based on the working condition of the flexible direct current valve submodule at the overvoltage fault point, and the test loop comprises: According to a preset fault point voltage and current, a preset test loop is calculated or simulated to obtain basic electrical parameters of each element in the test loop, initial voltages and initial currents of each element, action time points or action thresholds of the IGBT and the bypass switch, and the test loop of the bypass switch is built.

[0008] As an improvement of the above-mentioned scheme, the pre-charging of the first capacitor and the second capacitor comprises: closing the first disconnector to enable the first pre-charging circuit to charge the first capacitor; When the voltage of the first capacitor is greater than a preset initial voltage, the first disconnector is opened. The second disconnector is closed to enable the second pre-charging circuit to charge the second capacitor. When the voltage of the second capacitor is greater than a preset initial voltage, the second disconnector is opened.

[0009] As an improvement of the above-mentioned scheme, the IGBT has the ability to be turned off at any current point in a preset discharge condition of the first capacitor, and the static withstand voltage level of the IGBT is greater than the maximum voltage across the IGBT in the test process.

[0010] The embodiment of the present application also provides a reliability test device for a flexible direct current valve sub-module bypass switch, comprising: a test circuit building module, configured to build a test circuit of the bypass switch based on the working condition of the flexible direct current valve sub-module at an overvoltage fault point; the test circuit comprises: a first pre-charging circuit, a first disconnector, a first capacitor, a first discharge resistor, an insulated gate bipolar transistor (IGBT), a diode, a second pre-charging circuit, a second disconnector, a second capacitor, a second discharge resistor, an air-core reactor and a bypass switch. A capacitor pre-charging module is configured to pre-charge the first capacitor and the second capacitor. A capacitor discharge module is configured to turn on the IGBT until the voltage of the first capacitor is less than a preset termination discharge voltage, and turn off the IGBT. A bypass switch action module is configured to close the bypass switch when the voltage of the second capacitor is greater than a preset fault point voltage. A test result analysis module is configured to obtain waveform data of voltages and currents of each element in the test circuit in a test process when it is monitored that the test circuit is discharged, analyze the waveform data, and obtain the reliability test result of the bypass switch.

[0011] Further, the test circuit specifically comprises: The first pre-charging circuit is connected to the first capacitor through the first disconnector and is configured to pre-charge the first capacitor; and the first capacitor is connected in parallel with the first discharge resistor. The second pre-charging circuit is connected to the second capacitor through the second disconnector and is configured to pre-charge the second capacitor; and the second capacitor is connected in parallel with the second discharge resistor. The collector of the IGBT is connected with the first capacitor, and the emitter of the IGBT is connected with the negative electrode of the diode; one end of the second capacitor is connected with the positive electrode of the diode, and the other end of the second capacitor is connected with one end of the bypass switch; the other end of the bypass switch is connected with the negative electrode of the diode; and the air-core reactor is connected in parallel with the bypass switch.

[0012] Further, the test circuit building module is specifically used for: According to the preset fault point voltage and current, the preset test circuit is calculated or simulated to obtain basic electrical parameters of each element in the test circuit, initial voltages and initial currents of each element, action time points or action thresholds of the IGBT and the bypass switch, and a test circuit of the bypass switch is built.

[0013] Further, the capacitor pre-charging module is specifically used for: The first disconnecting switch is closed to enable the first pre-charging circuit to charge the first capacitor; When the voltage of the first capacitor is greater than a preset initial voltage, the first disconnecting switch is opened; The second disconnecting switch is closed to enable the second pre-charging circuit to charge the second capacitor; When the voltage of the second capacitor is greater than a preset initial voltage, the second disconnecting switch is opened.

[0014] Further, the IGBT has the ability to be turned off at any current point in the preset discharge condition of the first capacitor, and the static withstand voltage level of the IGBT is greater than the maximum voltage across the IGBT in the test process.

[0015] The method and device for testing the reliability of a bypass switch of a flexible direct current valve submodule provided by the embodiment of the present application have the following advantages over the prior art: a test loop of the bypass switch is constructed based on the working condition of the flexible direct current valve submodule at an overvoltage fault point, the test loop comprises a first pre-charging loop and an isolating switch thereof, a first capacitor and a discharge resistor thereof, an insulated gate bipolar transistor (IGBT), a diode, a second pre-charging loop and an isolating switch thereof, a second capacitor and a discharge resistor thereof, an air-core reactor, and the bypass switch; the first capacitor and the second capacitor are pre-charged; the IGBT is turned on until the voltage of the first capacitor is less than a preset termination discharge voltage, and then the IGBT is turned off; when the voltage of the second capacitor is greater than a preset fault point voltage, the bypass switch is closed; when it is monitored that the test loop is discharged, the waveform data of the voltage and current of each element in the test loop during the test are obtained, and the waveform data are analyzed to obtain the reliability test result of the bypass switch; the embodiment of the present application can accurately simulate the working condition of the bypass switch of the first-stage protection when an overvoltage fault occurs in a submodule of an extra-high voltage flexible direct current valve, is beneficial to the test of the protection characteristics of the submodule before the project is put into operation and the reduction of similar overvoltage protection faults after the project is put into operation, and can improve the accuracy of the reliability test of the bypass switch of the extra-high voltage flexible direct current valve submodule. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a flowchart of a method for testing the reliability of a bypass switch of a flexible direct current valve submodule provided by the embodiment of the present application; Figure 2 is a structural diagram of a bypass switch test loop provided by the embodiment of the present application; Figure 3 is a loop diagram of the bypass switch test loop when the reactor is energized provided by the embodiment of the present application; Figure 4 is a loop diagram of the bypass switch test loop when a preset voltage and current test point is reached provided by the embodiment of the present application; Figure 5 is a loop diagram of the bypass switch test loop after the bypass switch is actuated provided by the embodiment of the present application; Figure 6 is a structural diagram of a device for testing the reliability of a bypass switch of a flexible direct current valve submodule provided by the embodiment of the present application; the following is a description of the reference numerals: 1, second pre-charging loop; 2, IGBT; 3, diode; 4, first capacitor; 5, second capacitor; 6, bypass switch; 7, first discharge resistor; 8, second discharge resistor; 9, air-core reactor; 10, first isolating switch; 11, first pre-charging loop; 12, second isolating switch. DETAILED DESCRIPTION

[0017] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0018] Please refer to Figure 1 , Figure 1 is a flowchart of a reliability test method of a flexible direct current valve submodule bypass switch provided by the embodiments of the present application. The reliability test method of the flexible direct current valve submodule bypass switch comprises: S1: based on the working condition of the flexible direct current valve submodule at an overvoltage fault point, a test loop of the bypass switch is constructed; the test loop comprises a first pre-charging loop 11, a first isolation switch 10, a first capacitor 4, a first discharge resistor 7, an insulated gate bipolar transistor IGBT 2, a diode 3, a second pre-charging loop 1, a second isolation switch 12, a second capacitor 5, a second discharge resistor 8, a hollow reactor 9, and a bypass switch 6; S2: the first capacitor 4 and the second capacitor 5 are pre-charged; S3: the IGBT 2 is turned on until the voltage of the first capacitor 4 is less than a preset termination discharge voltage, and the IGBT 2 is turned off; S4: when the voltage of the second capacitor 5 is greater than a preset fault point voltage, the bypass switch 6 is closed; S5: when it is monitored that the test loop is discharged, the waveform data of the voltage and current of each element in the test loop in the test process is obtained, and the waveform data is analyzed to obtain the reliability test result of the bypass switch.

[0019] Specifically, the test method is independent of the converter valve submodule topology, and mainly simulates the reliable action of the submodule bypass switch when the fault point occurs in the approximate real working condition. First, the parameters and initial values of each component in the bypass switch test circuit according to the expected fault point voltage and current calculation are obtained, and the required parameters of the components and the parameters required for control are obtained. Then, according to the calculation results, appropriate capacitors and their discharge resistors, IGBTs, capacitor pre-charge circuits and their disconnectors, diodes, and air-core reactors are selected. Before the test, the test circuit is connected to the bypass switch to be tested according to the test circuit. Before the formal test, the test control program parameters are configured according to the calculated initial setting values. The local control program needs to configure the FPGA (Field Programmable Gate Array) on the local control board card, and the remote control program needs to program the DSP (Digital Signal Processor) on the remote control board card. During the formal test, the pre-charge operation of the first capacitor and the second capacitor is performed, and after the operation is completed, the pre-charge circuit disconnector is turned off. After the pre-charge operation is completed, the test is formally carried out, and finally the test waveform is recorded and the test result is checked, and the test is finally completed.

[0020] Wherein, reaching the expected fault point voltage and current conditions involves timely control of multiple switches in the test circuit, and each component of the selected test circuit should ensure that the voltage and current of each part are basically consistent with the expected value when each switch is actuated. After the IGBT is turned on, the first capacitor begins to discharge to the air-core reactor, and the current forms a path through the first capacitor, IGBT, and air-core reactor. The path current rises and is always positive, and the voltage of the first capacitor decreases from the initial voltage and is always positive. After the IGBT is turned off, the air-core reactor begins to discharge to the second capacitor, and the current forms a path through the air-core reactor, the second capacitor, and the diode. The path current decreases and is always positive, and the voltage of the second capacitor rises from the initial voltage and is always positive. The bypass switch is closed, and the voltage across the bypass switch and the current of the air-core reactor at the moment of closing are the expected simulation fault point voltage and current. Thereafter, the current forms a path through the air-core reactor and the bypass switch until the energy of the reactor is exhausted. The first capacitor and the second capacitor continue to discharge through their respective discharge resistors until the energy of the capacitors is exhausted.

[0021] Further, the test circuit of the bypass switch is constructed, as shown in Figure 2 The test circuit is used to generate the expected fault point voltage and current working condition and to verify the reliability of the bypass switch when the bypass switch is closed at the simulated fault point.

[0022] As one of the optional embodiments, the test circuit specifically includes: The first pre-charging circuit 11 is connected with the first capacitor 4 through the first isolating switch 10, and is used for pre-charging the first capacitor 4; the first capacitor 4 is connected in parallel with the first discharging resistor 7; The second pre-charging circuit 1 is connected with the second capacitor 5 through the second isolating switch 12, and is used for pre-charging the second capacitor 5; the second capacitor 5 is connected in parallel with the second discharging resistor 8; The collector of the IGBT 2 is connected with one end of the first capacitor 4, and the emitter of the IGBT 2 is connected with the negative electrode of the diode 3; the other end of the first capacitor 4 is connected with one end of the bypass switch 6; one end of the second capacitor 5 is connected with the positive electrode of the diode 3, and the other end of the second capacitor 5 is connected with one end of the bypass switch 6; the other end of the bypass switch 6 is connected with the negative electrode of the diode 3; the air-core reactor 9 is connected in parallel with the bypass switch 6.

[0023] As one of the optional embodiments, the test circuit of the bypass switch is constructed under the working condition of the overvoltage fault point of the flexible direct current converter valve sub-module, and the test circuit comprises: According to the preset fault point voltage and current, the preset test circuit is calculated or simulated to obtain basic electrical parameters of each element in the test circuit, initial voltages and currents of each element, action time points or action thresholds of the IGBT and the bypass switch, and the test circuit of the bypass switch is constructed.

[0024] Specifically, according to the voltage and current of the expected fault point of the sub-module reliability test, the voltage and current of each component in the test circuit are calculated or simulated, and the calculation or simulation results should include basic electrical parameters of each component in the test circuit, initial voltages and currents of each component, and switch action time points or action thresholds of the IGBT 2 and the bypass switch 6; according to the calculation or simulation results, each component of the test circuit is preselected and connected according to the selected components, and the selected components are connected according to the selected components. Figure 2 The circuit shown in the figure connects each component to construct a complete reliability test circuit of the bypass switch of the flexible direct current converter valve sub-module.

[0025] Further, according to the obtained calculation or simulation test circuit control parameters, the test control program related parameters are configured, and the logic configuration of the FPGA on the local control board card and the program burning of the DSP on the remote control board card are completed. Further, according to the initial voltages of the first capacitor 4 and the second capacitor 5 calculated or simulated, the pre-charging operation of the first capacitor 4 and the second capacitor 5 is carried out, and immediately after the preset voltage value is reached, the test is carried out; the test operation is completed, and after the voltage and current in the test circuit are discharged to below the safety value, further complete discharge operation is carried out to end the test, and the test related waveforms are recorded and the test result analysis and checking are carried out.

[0026] Further, the IGBT has the ability to turn off at any current point in the preset discharge condition of the first capacitor, and the static withstand voltage level of the IGBT is greater than the maximum voltage across the IGBT during the test.

[0027] Further, in addition to the specifications of the above components meeting the calculation and analysis of the electrical stress of each component, the other connection parts of the circuit should select appropriate cables or busbars according to the size of the current, and take appropriate insulation and voltage resistance measures according to the possible overvoltage level.

[0028] Specifically, the diode has the same current and voltage level as the IGBT; the first capacitor and the second capacitor both meet the voltage and current levels and capacitance values required by the initial discharge voltage, the termination discharge voltage, and the termination discharge current of the capacitor in the above calculation or simulation results; the bypass switch, i.e. the test bypass switch, is selected according to the bypass switch product to be verified in the test; the first discharge resistor and the second discharge resistor are both flexible direct current engineering discharge resistors, which adopt natural heat dissipation mode and meet the temperature rise requirement in the discharge process; the air-core reactor meets the voltage and current levels, I2t (ampere square second), and inductance value required by the initial discharge voltage, the termination discharge voltage, and the termination discharge current of the first capacitor and the second capacitor; the disconnector meets the requirement of performing no-load closing / opening action in the first capacitor pre-charging process; the pre-charging circuit meets the requirement of charging the capacitor and reaching the expected initial voltage.

[0029] As one of the optional embodiments, the pre-charging of the first capacitor and the second capacitor includes: closing the first disconnector 10 to charge the first capacitor 4 by the first pre-charging circuit 11; When the voltage of the first capacitor 4 is greater than the preset initial voltage, the first disconnector 10 is opened; The second disconnector 12 is closed to charge the second capacitor 5 by the second pre-charging circuit 1; When the voltage of the second capacitor 5 is greater than the preset initial voltage, the second disconnector 12 is opened.

[0030] Specifically, the disconnector 10 of the first pre-charging circuit 11 is closed, and then the charging of the first capacitor 4 is started; the charging state is maintained before the preset initial voltage of the first capacitor 4 is reached, until the preset initial voltage is reached, the disconnector 10 of the first pre-charging circuit 11 is opened, and the first pre-charging circuit 11 is obviously disconnected from the first capacitor 4. The disconnector 12 of the second pre-charging circuit 1 is closed and the charging is started; the charging state is maintained before the preset initial voltage of the second capacitor 5 is reached, until the preset initial voltage is reached, the disconnector 12 of the second pre-charging circuit 1 is opened, and the second pre-charging circuit 1 is obviously disconnected from the second capacitor 5. The pre-charging action is ended.

[0031] Further, the control turns on the controllable turn-off device IGBT 2, the first capacitor 4 forms a path through the IGBT 2 and the air-core reactor 9, and the first capacitor 4 discharges to the air-core reactor 9, as shown in FIG. 2. Figure 3

[0032] When the first capacitor 4 discharges to a voltage lower than a set termination voltage, the control turns off the IGBT 2, and then the first capacitor 4 is disconnected from the path and discharges by itself through the discharge resistor 7 connected across the first capacitor 4. After the above action is performed, the air-core reactor 9 forms a path through the second capacitor 5 and the diode 3, and the air-core reactor 9 discharges to the second capacitor 5, as shown in FIG. 3. Figure 4

[0033] After the bypass switch 6 performs the closing action, the air-core reactor 9 forms a path with the bypass switch 6, and the air-core reactor 9 starts to discharge by itself through the bypass switch 6, and the second capacitor 5 discharges by itself through the discharge resistor 8 connected across the second capacitor 5, as shown in FIG. 4. Figure 5

[0034] If the initial setting, the pre-charge voltage and the action performance are correct, the voltage and current changes in the test loop switching and the final voltage and current across the bypass switch can meet the expected parameter values required to be reached in the simulation of the fault, so that the closing action verification test of the bypass switch under the simulation test of the fault point is completed, and then according to the test result, the reliability of the sub-module of the HVDC converter valve under the fault can be evaluated. Specifically, the collected waveform data is compared with the expected parameters (such as the expected discharge termination voltage of the capacitor, the voltage threshold when the bypass switch is closed, etc.), and if the waveform data is within the set tolerance range, it indicates that the bypass switch of the sub-module can work normally under the set fault condition and has high reliability.

[0035] The embodiment of the present application can accurately simulate the working condition of the bypass switch when the first-level protection bypass switch acts in the case of overvoltage fault of the sub-module in the UHV HVDC converter valve, can adjust the expected voltage and current of the fault point through calculation, is helpful for the test of the protection characteristics of the sub-module before the engineering is put into operation and the reduction of similar overvoltage protection faults after the engineering is put into operation, and is also helpful for the reliability research of the bypass switch body.

[0036] Correspondingly, the present application also provides a reliability test device of the bypass switch of the sub-module of the HVDC converter valve, which can realize all processes of the reliability test method of the bypass switch of the sub-module of the HVDC converter valve in the above embodiment.

[0037] Please refer to Figure 6 , Figure 6 ​​​is a structural schematic diagram of a reliability test device of a flexible direct current valve submodule bypass switch provided by an embodiment of the present application. The reliability test device of the flexible direct current valve submodule bypass switch comprises: A test loop building module 601 is configured to build a test loop of the bypass switch based on the working condition of the flexible direct current valve submodule at an overvoltage fault point. The test loop comprises a first pre-charging loop, a first isolation switch, a first capacitor, a first discharge resistor, an insulated gate bipolar transistor (IGBT), a diode, a second pre-charging loop, a second isolation switch, a second capacitor, a second discharge resistor, an air-core reactor and a bypass switch. A capacitor pre-charging module 602 is configured to pre-charge the first capacitor and the second capacitor. A capacitor discharging module 603 is configured to turn on the IGBT until the voltage of the first capacitor is less than a preset termination discharge voltage, and turn off the IGBT. A bypass switch action module 604 is configured to close the bypass switch when the voltage of the second capacitor is greater than a preset fault point voltage. A test result analysis module 605 is configured to obtain waveform data of the voltage and current of each element in the test loop during the test process when it is monitored that the test loop is discharged, analyze the waveform data, and obtain the reliability test result of the bypass switch.

[0038] Preferably, the test loop specifically comprises: The first pre-charging loop is connected with the first capacitor through the first isolation switch, and is configured to pre-charge the first capacitor. The first capacitor is connected in parallel with the first discharge resistor. The second pre-charging loop is connected with the second capacitor through the second isolation switch, and is configured to pre-charge the second capacitor. The second capacitor is connected in parallel with the second discharge resistor. The collector of the IGBT is connected with the first capacitor, and the emitter of the IGBT is connected with the negative electrode of the diode. One end of the second capacitor is connected with the positive electrode of the diode, and the other end of the second capacitor is connected with one end of the bypass switch. The other end of the bypass switch is connected with the negative electrode of the diode. The air-core reactor is connected in parallel with the bypass switch.

[0039] Preferably, the test loop building module 601 is specifically configured to: According to the preset fault point voltage and current, the preset test loop is calculated or simulated to obtain the basic electrical parameters of each element in the test loop, the initial voltage and initial current of each element, the action time point or action threshold of the IGBT and the bypass switch, and the test loop of the bypass switch is built.

[0040] Preferably, the capacitor pre-charging module 602 is specifically used for: closing the first disconnector to enable the first pre-charging circuit to charge the first capacitor; when the voltage of the first capacitor is greater than a preset initial voltage, disconnecting the first disconnector; closing the second disconnector to enable the second pre-charging circuit to charge the second capacitor; when the voltage of the second capacitor is greater than a preset initial voltage, disconnecting the second disconnector.

[0041] Preferably, the IGBT has the capability of turning off at any current point in the preset discharging condition of the first capacitor, and the static withstand voltage level of the IGBT is greater than the maximum voltage across the IGBT during the test process.

[0042] In specific implementations, the working principle, control flow and technical effects of the reliability test device of the HVDC valve submodule bypass switch provided by the embodiments of the present application correspond to the reliability test method of the HVDC valve submodule bypass switch in the above embodiments, and will not be described here.

[0043] The embodiments of the present application provide a reliability test method and device of a HVDC valve submodule bypass switch, which has the beneficial effect that: based on the working condition of the HVDC valve submodule at the overvoltage fault point, a test circuit of the bypass switch is constructed, the test circuit includes: a first pre-charging circuit and a disconnector thereof, a first capacitor and a discharging resistor thereof, an insulated gate bipolar transistor (IGBT), a diode, a second pre-charging circuit and a disconnector thereof, a second capacitor and a discharging resistor thereof, an air-core reactor and a bypass switch; the first capacitor and the second capacitor are pre-charged; the IGBT is turned on until the voltage of the first capacitor is less than a preset termination discharging voltage, and the IGBT is turned off; when the voltage of the second capacitor is greater than a preset fault point voltage, the bypass switch is closed; when it is monitored that the test circuit is discharged, the waveform data of the voltage and current of each element in the test circuit during the test process is obtained, and the waveform data is analyzed to obtain the reliability test result of the bypass switch; the embodiments of the present application can accurately simulate the working condition of the first-level protection bypass switch when the overvoltage fault occurs in the submodule of the EHV HVDC valve, which is beneficial to the test of the protection characteristics of the submodule before the project is put into operation and the reduction of similar overvoltage protection faults after the project is put into operation, and improves the accuracy of the reliability test of the EHV HVDC valve submodule bypass switch.

[0044] The above is the preferred embodiment of the present application, and it should be noted that for ordinary skilled persons in the technical field, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements are also considered within the protection scope of the present application.

Claims

1. A reliability test method for a flexible HVDC valve sub-module bypass switch, characterized in that, The application relates to a reliability test method for a bypass switch of a flexible direct-current converter valve sub-module. The test loop of the bypass switch is constructed based on the working condition of the flexible direct-current converter valve sub-module at an overvoltage fault point, and the test loop comprises a first pre-charging loop, a first isolating switch, a first capacitor, a first discharge resistor, an insulated gate bipolar transistor (IGBT), a diode, a second pre-charging loop, a second isolating switch, a second capacitor, a second discharge resistor, an air-core reactor and a bypass switch; the first capacitor and the second capacitor are pre-charged; The IGBT is turned on until the voltage of the first capacitor is less than a preset termination discharge voltage, and then the IGBT is turned off; When the voltage of the second capacitor is greater than a preset fault point voltage, the bypass switch is closed; When it is monitored that the test loop is discharged, the waveform data of the voltage and current of each element in the test loop during the test process is obtained, and the waveform data is analyzed to obtain the reliability test result of the bypass switch.

2. The reliability test method of a LCC sub-module bypass switch according to claim 1, characterized in that, The test loop specifically comprises: The first pre-charging loop is connected with the first capacitor through the first isolating switch and is used for pre-charging the first capacitor; and the first capacitor is connected in parallel with the first discharge resistor; The second pre-charging loop is connected with the second capacitor through the second isolating switch and is used for pre-charging the second capacitor; and the second capacitor is connected in parallel with the second discharge resistor; The collector of the IGBT is connected with the first capacitor, the emitter of the IGBT is connected with the negative electrode of the diode, one end of the second capacitor is connected with the positive electrode of the diode, the other end of the second capacitor is connected with one end of the bypass switch, the other end of the bypass switch is connected with the negative electrode of the diode, and the air-core reactor is connected in parallel with the bypass switch.

3. The reliability test method of a LCC sub-module bypass switch according to claim 1, characterized in that, The test loop of the bypass switch is constructed based on the working condition of the flexible direct-current converter valve sub-module at an overvoltage fault point, and the test loop comprises a first pre-charging loop, a first isolating switch, a first capacitor, a first discharge resistor, an insulated gate bipolar transistor (IGBT), a diode, a second pre-charging loop, a second isolating switch, a second capacitor, a second discharge resistor, an air-core reactor and a bypass switch; the first capacitor and the second capacitor are pre-charged; The basic electrical parameters of each element, the initial voltage and initial current of each element, the action time point or action threshold value of the IGBT and the bypass switch are obtained by calculating or simulating the preset test loop according to the preset fault point voltage and current, and the test loop of the bypass switch is built.

4. The reliability test method of a LCC sub-module bypass switch according to claim 1, wherein The first capacitor and the second capacitor are pre-charged, and the pre-charging comprises: The first isolating switch is closed to enable the first pre-charging loop to charge the first capacitor; When the voltage of the first capacitor is greater than a preset initial voltage, the first isolating switch is disconnected; The second isolating switch is closed to enable the second pre-charging loop to charge the second capacitor; When the voltage of the second capacitor is greater than a preset initial voltage, the second isolating switch is disconnected.

5. The reliability test method of a LCC sub-module bypass switch according to claim 1, wherein The IGBT has the capability of being turned off at any current point in the preset discharge condition of the first capacitor, and the static withstand voltage level of the IGBT is greater than the maximum voltage between the two ends of the IGBT during the test process.

6. A reliability test device for a flexible HVDC valve sub-module bypass switch, characterized in that The application relates to a reliability test method for a bypass switch of a flexible direct-current converter valve sub-module. The test circuit building module is configured to build a test circuit of the bypass switch based on the working condition of the flexible direct current valve sub-module at an overvoltage fault point; the test circuit comprises: a first pre-charging circuit, a first isolating switch, a first capacitor, a first discharging resistor, an insulated gate bipolar transistor (IGBT), a diode, a second pre-charging circuit, a second isolating switch, a second capacitor, a second discharging resistor, an air-core reactor and a bypass switch; The capacitor pre-charging module is configured to pre-charge the first capacitor and the second capacitor. The capacitor discharging module is configured to turn on the IGBT until the voltage of the first capacitor is less than a preset termination discharging voltage, and turn off the IGBT. The bypass switch action module is configured to close the bypass switch when the voltage of the second capacitor is greater than a preset fault point voltage. The test result analysis module is configured to obtain waveform data of voltages and currents of each element in the test circuit in a test process when it is monitored that the test circuit is discharged, analyze the waveform data, and obtain a reliability test result of the bypass switch.

7. The reliability test device of a LCC sub-module bypass switch according to claim 6, characterized in that, The test circuit specifically comprises: The first pre-charging circuit is connected with the first capacitor through the first isolating switch, and is configured to pre-charge the first capacitor; the first capacitor is connected in parallel with the first discharging resistor; The second pre-charging circuit is connected with the second capacitor through the second isolating switch, and is configured to pre-charge the second capacitor; the second capacitor is connected in parallel with the second discharging resistor; The collector of the IGBT is connected with the first capacitor, and the emitter of the IGBT is connected with the negative electrode of the diode; one end of the second capacitor is connected with the positive electrode of the diode, and the other end of the second capacitor is connected with one end of the bypass switch; the other end of the bypass switch is connected with the negative electrode of the diode; the air-core reactor is connected in parallel with the bypass switch.

8. The reliability test device of a LCC sub-module bypass switch according to claim 6, characterized in that, The test circuit building module is specifically configured to: According to a preset fault point voltage and current, a preset test circuit is calculated or simulated to obtain basic electrical parameters of each element in the test circuit, initial voltages and currents of each element, action time points or action thresholds of the IGBT and the bypass switch, and the test circuit of the bypass switch is built.

9. The reliability test device of a LCC sub-module bypass switch according to claim 6, characterized in that, The capacitor pre-charging module is specifically configured to: The first isolating switch is closed to enable the first pre-charging circuit to charge the first capacitor; When the voltage of the first capacitor is greater than a preset initial voltage, the first isolating switch is opened; The second isolating switch is closed to enable the second pre-charging circuit to charge the second capacitor; When the voltage of the second capacitor is greater than a preset initial voltage, the second isolating switch is opened.

10. The reliability test device of a LCC sub-module bypass switch according to claim 6, characterized in that, The IGBT has the ability to be turned off at any current point in a preset discharging condition of the first capacitor, and the static withstand voltage level of the IGBT is greater than the maximum voltage across the IGBT in the test process.

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