Batch testing method for closing times of bypass switches in sub-modules of converter chain, and storage medium

Abstract

A batch testing method for closing times of bypass switches in sub-modules of a converter chain, and a storage medium. The test objects in the method comprise a converter chain (3) and an auxiliary system, wherein the converter chain (3) comprises N sub-modules (4), a bypass switch (5) is connected in parallel to an alternating-current port of each sub-module (4), and each sub-module (4) comprises a control unit. The method comprises: pre-charging a direct-current capacitor of each sub-module by means of an auxiliary system, and using a control unit to send a bypass switch closing command; generating an electrical transient before and after a bypass switch is closed; the control unit detecting the electrical transient, so as to measure the difference between the moment when the electrical transient changes and the moment when the closing command is sent, and use the difference as a bypass switch closing time; and cyclically executing the steps of closing a bypass switch and calculating a closing time, so as to complete batch testing for closing times of bypass switches in N sub-modules.

Description

Batch test method and storage medium for the closing time of the bypass switch of the converter chain module

[0001] This application claims priority to Chinese Patent Application No. 202410926269.6, filed with the Chinese Patent Office on July 11, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of high voltage direct current transmission technology, and for example relates to a batch test method and storage medium for the closing time of the bypass switch of the converter chain submodule. Background Technology

[0003] With the application and development of power electronics technology in power systems, power electronic equipment is developing towards high voltage, large capacity, and modularization. It is widely used, especially in flexible DC transmission systems and chain static var generators. The converters of the above equipment are composed of several converter chains, and each converter chain has a large number of sub-modules cascaded together.

[0004] If a submodule of the converter valve malfunctions during operation, the bypass switch on the AC port of the submodule needs to be closed to put the faulty submodule into a bypass state, ensuring the normal operation of other submodules and guaranteeing the stable operation of the modular multilevel converter. Currently, the bypass switch of the flexible DC converter valve is a mechanical structure, and there is a certain closing time during the bypass switch closing process. During the bypass switch closing time, the capacitor of the faulty submodule will continue to charge under the influence of the bridge arm current, causing the faulty submodule to continue to rise in voltage, resulting in overvoltage breakdown of components within the faulty submodule and affecting the safety of surrounding submodules. Testing the closing time of the submodule bypass switch to ensure it meets the parameter requirements of the flexible DC converter valve design is crucial for improving the operational reliability of the flexible DC converter valve and preventing the converter valve malfunction from escalating due to unmet closing time requirements.

[0005] Currently, the testing methods for the closing of bypass switches in flexible DC converter valve submodules in related technologies are insufficient to meet the needs of engineering applications. For example, in "CN115372815A A Submodule Bypass Switch Closing and Bounce Time Testing Device, Method, and Medium," this method first connects the power supply module between the positive and negative terminals of the submodule's DC capacitor, outputting a power supply voltage U to charge the bypass switch's energy storage capacitor and activate the submodule's control board. Then, it uses a voltage detection module to measure the characteristic of the submodule's AC port voltage dropping from 0.5U to 0 after the bypass switch closes, calculating the closing time. The main problems with the proposed solution are: (1) the sampling of the AC voltage primary circuit adds an extra voltage sensor, which has an adverse effect on cost and reliability; (2) during testing, the power supply module needs to be connected to the positive and negative terminals of the DC capacitor of the sub-module, so a power supply module can only test the bypass switch of one sub-module at the same time. It is suitable for type testing of a single bypass switch. In actual engineering applications, a converter station may have thousands of bypass switches, and it is necessary to power on each switch, close the switch, test the AC voltage, and record the data. The workload is large and the testing efficiency needs to be improved.

[0006] In related technologies, the applicant has filed several patents in the engineering application field of testing sub-modules of flexible DC converter valves, including CN113922407A Low-pressure pressurization system and control method for flexible DC converter stations; CN113917251A Low-pressure pressurization test system and control method for converter valves; CN112924838A Modular converter chain, synthetic loop system, converter valve and control method; CN113285621A High-pressure operation circuit, field test system and control method for converter valves. The above-mentioned technologies all adopt the method of combining low-pressure pressurization with batch testing to improve testing efficiency. The above focuses on testing the performance of IGBTs and the closing function of bypass switches, and has achieved good application results. However, the above-mentioned technical solutions do not involve testing the closing time of the sub-module bypass switch, and fail to quantitatively judge the performance of the bypass switch. Summary of the Invention

[0007] This application develops a batch testing method and storage medium for the closing time of bypass switches in converter chain submodules, aiming to solve the technical problem in related technologies that can only test the closing time of a single bypass switch and cannot directly test the closing time of multiple bypass switches in batches.

[0008] Technical Solution: Embodiments of this application provide a batch testing method for the closing time of bypass switches in converter chain submodules. The test objects include the converter chain and auxiliary systems. The converter chain includes N submodules, each submodule being a half-bridge or full-bridge circuit structure composed of power semiconductors and DC capacitors. A bypass switch is connected in parallel to the AC port of each submodule. Each submodule includes a control unit, where N is an integer greater than or equal to 2. The testing method includes:

[0009] The auxiliary system precharges the DC capacitor of the submodule, and the control unit sends the bypass switch closing command.

[0010] The bypass switch generates an electrical abrupt change before and after closing; the control unit detects the electrical abrupt change and uses the difference between the time when the electrical abrupt change occurs and the time when the closing command is issued as the closing time of the bypass switch;

[0011] The steps of closing the bypass switch and calculating the closing time are executed repeatedly to complete the batch test of the closing time of the bypass switch for N sub-modules.

[0012] In some embodiments, the testing method specifically includes the following steps:

[0013] S101: The submodule is precharged by controlling all the bypass switches to be in the open state through the auxiliary system;

[0014] S102: Select the sub-module under test, and select the observable electrical change criterion for closing the bypass switch as the voltage across the lower transistor of the sub-module, or the DC capacitor voltage, or the voltage across the upper transistor of the sub-module; the lower transistor of the sub-module is defined as a power semiconductor device connected in parallel with the bypass switch of the sub-module, and the upper transistor of the sub-module is connected in series with the lower transistor of the sub-module in the same bridge arm;

[0015] S103: The control unit of the tested submodule actively or by receiving external instructions issues the bypass switch closing command and records the time as the first closing time t1;

[0016] S104: Determine that the observable electrical transient quantity of the tested submodule has changed, and the control unit of the submodule records the time as the second closing time t2;

[0017] S105: The difference between the second closing time t2 and the first closing time t1 is determined as the closing time of the bypass switch of the tested submodule;

[0018] S106: Repeat steps S102 to S105 to obtain the closing time of the bypass switch when all the sub-modules are the tested sub-modules.

[0019] In some embodiments, the auxiliary system includes an auxiliary power supply system and an auxiliary distribution system, the control unit includes a DC capacitor voltage sampling module, and the submodule further includes a drive unit, wherein:

[0020] The auxiliary power supply system includes a first adjustable DC voltage source, and the auxiliary distribution system connects the auxiliary power supply system and the DC capacitor of the submodule;

[0021] The DC capacitor voltage sampling module is configured to sample the DC capacitor voltage of the sub-module under test to obtain the sampled value V1;

[0022] The driving unit is configured to control the power semiconductor device to turn on and off, and the driving unit includes a power semiconductor device collector-emitter potential difference detection module.

[0023] In some embodiments, the external command in step S103 comes from a host computer; the host computer receives the DC capacitor voltage of the submodule through an optical fiber, and sends the bypass switch closing command to the submodule under test through an optical fiber; the control unit is configured to send the bypass switch closing time information to the host computer for data processing and storage.

[0024] In some embodiments, when the observable electrical abrupt change criterion for closing the bypass switch in step S102 is the voltage across the lower tube of the submodule, the steps for determining the change in electrical abrupt change in step S104 are as follows:

[0025] After the bypass switch closing command is issued, the potential difference between the collector and emitter of the power semiconductor device in the drive unit is monitored by the potential difference detection module between the collector and emitter of the lower transistor of the submodule, and the potential difference is sent to the control unit.

[0026] The control unit detects that the potential difference changes from 0 to a negative value and records this moment as the second closing time t2.

[0027] In some embodiments, when the observable electrical abrupt change criterion for selecting the bypass switch to close in step S102 is the voltage across the upper tube of the submodule, the steps for determining the change in electrical abrupt change in step S104 are as follows:

[0028] The upper transistor of the tested submodule is turned on, and the upper transistor of the submodule and the lower transistor of the submodule are connected in series in the same bridge arm. The DC capacitor voltage is discharged, and when the voltage drops to the threshold value V3, the bypass switch closing command is issued.

[0029] The potential difference between the collector and emitter of the power semiconductor device in the driving unit is monitored by the potential difference detection module, and the potential difference is sent to the control unit.

[0030] The control unit detects that the potential difference changes from 0 to a positive value and records this moment as the second closing time t2.

[0031] In some embodiments, when the observable electrical abrupt change criterion for closing the bypass switch is the DC capacitor voltage in step S102, the steps for determining the change in electrical quantity in step S104 are as follows:

[0032] The output voltage of the first adjustable DC voltage source in the auxiliary power system is increased, and after the voltage increases to the threshold value V2, the bypass switch closing command is issued.

[0033] The rate of change of the DC capacitor voltage is monitored by the control unit of the submodule under test;

[0034] The control unit records the moment when the rate of change of the DC capacitor voltage changes from a positive value to a zero or negative value as the second closing time t2.

[0035] In some embodiments, the testing method further includes active reset and / or passive reset:

[0036] Active reset: After executing multiple rounds of test steps S102 to S105, automatically enter S101 to recharge the sub-modules that have not completed the test steps;

[0037] Passive reset: In step S103, it is determined that the DC capacitor voltage of the tested submodule has not changed with the adjustment of the auxiliary power supply system, and the process returns to S101 to recharge.

[0038] In some embodiments, the negative terminal of the DC capacitor of the first submodule in the converter chain is defined as the third port, and the midpoint of the half-bridge of the Nth submodule is defined as the first port; the auxiliary distribution system includes M common-anode diodes, the cathodes of all the diodes are connected to the positive terminal of the DC capacitor of the submodule under test, the anodes of the M diodes are defined as the second port, and M is a positive integer less than or equal to N.

[0039] In some embodiments, the auxiliary power system further includes a charging and discharging resistor, wherein the positive terminal of the first adjustable DC voltage source is connected to the second port and the negative terminal is connected to the third port, and one end of the charging and discharging resistor is connected to the first port and the other end is connected to the third port.

[0040] In some embodiments, when the observable electrical transient criterion for selecting the bypass switch to close is the DC capacitor voltage, the auxiliary power supply system further includes a voltage regulating unit, which is connected in series on the branch where the charging and discharging resistor is located, and the voltage regulating unit includes a bypass branch and a power supply branch connected in parallel.

[0041] The bypass branch includes a first switch, and the power supply branch includes a second adjustable DC voltage source and a second switch connected in series.

[0042] The output voltage of the second adjustable DC voltage source is higher than that of the first adjustable DC voltage source;

[0043] During the pre-charging process in S101, the first switch is closed and the second switch is opened.

[0044] When executing S104, the switch state is switched, the first switch is opened, and the second switch is closed.

[0045] Accordingly, the computer-readable storage medium described in the embodiments of this application stores a computer program thereon, which, when executed by a processor, implements the steps of the batch testing method for the closing time of the bypass switch of the converter chain submodule as described above.

[0046] Beneficial Effects: Compared with related technologies, the batch testing method and storage medium for the closing time of the bypass switch of the converter chain submodule provided in this application embodiment can be performed in batches. The testing system includes an auxiliary power supply system and an auxiliary distribution system. The auxiliary power supply system is configured with various switch combination schemes, and the auxiliary distribution system provides a one-to-many connection path between the power supply and the submodule. The auxiliary power supply system and the auxiliary distribution system work together to realize various batch charging and discharging modes. The batch charging and discharging mode, combined with the cyclical "determine the submodule under test - submodule closing - record time" testing method, can simultaneously test the closing time of the bypass switches of multiple submodules. The cyclical testing process in the testing method is automatically executed by the submodule control unit program, which greatly improves the testing efficiency.

[0047] This application also provides specific test steps and offers multiple detection criteria: the observable electrical abrupt change criterion for bypass switch closing can be the voltage across the lower tube of the submodule, the DC capacitor voltage, or the voltage across the upper tube of the submodule. All of the above detection methods are based on electrical abrupt changes, which can quickly and accurately reflect the changing characteristics of the electrical quantity of the bypass switch closing, thereby achieving zero-delay calculation of the closing time. The calculation of the above detection and criteria is performed in the control unit built into the submodule, and the original drive unit of the submodule is utilized, without the need for additional test equipment. The method is simple, reliable, and low in cost. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 is an overall flowchart of the submodule bypass switch closing time test method provided in the embodiment of this application;

[0050] Figure 2 is a structural diagram of the collector-emitter potential difference detection module of the power semiconductor device provided in the embodiment of this application;

[0051] Figure 3 is a flowchart of the submodule bypass switch closing time test method provided in the embodiment of this application;

[0052] Figure 4 is an overall structural diagram of the submodule bypass switch closing time test system provided in the embodiment of this application;

[0053] Figure 5 is a first connection structure diagram of the auxiliary power supply system according to an embodiment of this application;

[0054] Figure 6 is a second connection structure diagram of the auxiliary power supply system according to an embodiment of this application;

[0055] Figure 7 is an overall structural diagram of the charging circuit of the first adjustable DC voltage source of the auxiliary power system according to an embodiment of this application;

[0056] Figure 8 is an overall structural diagram of the charging circuit of the second adjustable DC voltage source of the auxiliary power system according to an embodiment of this application.

[0057] Reference numerals in the attached diagram: 1. Auxiliary power supply system; 2. Auxiliary distribution system; 3. Converter chain; 4. Submodule; 5. Bypass switch; D1. First port; D2. Second port; D3. Third port; Q1. First switch; Q2. Second switch. Detailed Implementation

[0058] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0059] It should be understood that although the terms first, second, etc., may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this application. As used herein, the term "and / or" includes all combinations of any and more of the associated listed items.

[0060] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments and may not be to scale. The modules or processes shown in the drawings are not necessarily essential for implementing this application and therefore should not be used to limit the scope of protection of this application.

[0061] Currently, with the application and development of power electronics technology in power systems, power electronic equipment is developing towards high voltage, large capacity, and modularization. It is widely used, especially in flexible DC transmission systems and chain static var generators. The converters of these devices are composed of several converter chains, and each converter chain has a large number of sub-modules cascaded together.

[0062] If a submodule of the converter valve malfunctions during operation, the bypass switch on the AC port of the submodule needs to be closed to put the faulty submodule into a bypass state, ensuring the normal operation of other submodules and guaranteeing the stable operation of the modular multilevel converter. Currently, the bypass switch of the flexible DC converter valve is a mechanical structure, and there is a certain closing time during the bypass switch closing process. During the bypass switch closing time, the capacitor of the faulty submodule will continue to charge under the influence of the bridge arm current, causing the faulty submodule to continue to rise in voltage, resulting in overvoltage breakdown of components within the faulty submodule and affecting the safety of surrounding submodules. Testing the closing time of the submodule bypass switch to ensure it meets the parameter requirements of the flexible DC converter valve design is crucial for improving the operational reliability of the flexible DC converter valve and preventing the converter valve malfunction from escalating due to unmet closing time requirements.

[0063] In related technologies, the bypass switch closing test method for flexible DC converter valve submodules involves testing individual bypass switches during factory or incoming inspection. The main testing methods include installing position sensors to measure the switch's travel or using an oscilloscope to capture changes in the main contact voltage. While the efficiency is acceptable due to the design of test fixtures, once the submodules are assembled into the converter valve in the field, testing the main contact closing time requires placing the test fixture on the valve tower and energizing, closing, testing the main contact voltage, and recording the data for each switch individually. This process is labor-intensive, time-consuming, and unreliable. In practical engineering applications, a converter station may have thousands of bypass switches. Given this large number, the above testing methods are inefficient, costly, and impractical.

[0064] In view of this, this application provides a batch testing method for the closing time of bypass switches in converter chain submodules. The test objects of this method include converter chain 3 and auxiliary system. Converter chain 3 includes N submodules 4. Submodule 4 is a half-bridge or full-bridge circuit structure composed of power semiconductors and DC capacitors. A bypass switch 5 is connected in parallel to the AC port of submodule 4. Submodule includes control unit, where N is an integer greater than or equal to 2. The testing method precharges the DC capacitor of submodule 4 through auxiliary system, and sends a closing command to bypass switch 5 through control unit. An electrical change occurs before and after bypass switch 5 closes. Control unit detects the electrical change and uses the difference between the time of detection of the electrical change and the time of issuance of the closing command as the bypass switch closing time. The steps of bypass switch 5 closing and closing time calculation are executed cyclically to complete the batch testing of the closing time of bypass switch 5 for N submodules 4.

[0065] As shown in Figure 1, the specific steps of this test method in this embodiment are as follows:

[0066] S101: Submodule 4 is precharged by controlling all bypass switches 5 to be in the open state through the auxiliary system;

[0067] S102: Select the submodule under test. The observable electrical change criterion for closing the bypass switch 5 is the voltage across the lower transistor of the submodule, or the DC capacitor voltage, or the voltage across the upper transistor of the submodule. The lower transistor of the submodule is defined as a power semiconductor device connected in parallel with the bypass switch 5 of the submodule 4. The upper transistor of the submodule is connected in series with the lower transistor of the submodule in the same bridge arm.

[0068] When selecting the submodule to be tested, the submodule to be tested can be a single submodule 4 or A submodules 4 together, where A is an integer greater than or equal to 2 and A < N.

[0069] S103: The control unit of the tested submodule actively or by receiving external commands issues a command to close the bypass switch 5, and records the time as the first closing time t1;

[0070] S104: Determine that the observable electrical transients of the tested submodule have changed, and the control unit of submodule 4 records the time as the second closing time t2.

[0071] S105: The difference between the second closing time t2 and the first closing time t1 is determined as the closing time of the bypass switch 5 of the tested submodule.

[0072] S106: Repeat steps S102 to S105 to obtain the closing time of the corresponding bypass switch 5 when all submodules 4 are used as the tested submodules.

[0073] The auxiliary system includes an auxiliary power supply system 1 and an auxiliary distribution system 2. The auxiliary power supply system 1 includes a first adjustable DC voltage source, and the auxiliary distribution system 2 connects the auxiliary power supply system 1 and the DC capacitor of the submodule 4. The control unit also includes a DC capacitor voltage sampling module, which is configured to sample the DC capacitor voltage of the submodule under test to obtain a sampled value V1. The submodule 4 also includes a drive unit, which is configured to control the power semiconductor device to turn on and off. The drive unit includes a power semiconductor device collector-emitter potential difference detection module.

[0074] It should be noted that the power semiconductor device collector-emitter potential difference detection module of the driving unit is shown in Figure 2, including the driving power supply Vcc, voltage divider resistors R1 and R2, and diode D1; by detecting the midpoint voltage Vi of the voltage divider resistors, the collector-emitter potential difference of the power semiconductor device can be detected.

[0075] In some embodiments, the external command in step S103 comes from the host computer; the host computer receives the DC capacitor voltage of the submodule 4 through the optical fiber, and sends the bypass switch 5 closing command to the submodule under test through the optical fiber; the control unit is configured to send the bypass switch 5 closing time information to the host computer for data processing and storage.

[0076] In some embodiments, the observable electrical abrupt change criterion for selecting the closing of bypass switch 5 in step S102 is the voltage across the lower tube of the submodule, and the steps for determining the change in electrical abrupt change in step S104 are as follows:

[0077] After the bypass switch 5 is closed, the potential difference between the collector and emitter of the lower tube in the submodule is monitored by the collector-emitter potential difference detection module of the power semiconductor device in the drive unit, and the potential difference is sent to the control unit. The control unit detects the sudden change in the potential difference from 0 to a negative value and records this moment as the second closing moment t2.

[0078] Taking Figure 2 as an example, the drive power supply Vcc = +15V, R1 = 1KΩ, R2 = 2KΩ. When the down transistor is turned off and the bypass switch 5 is open, Vi = Vcc × R1 / (R1 + R2) = +10V. When the bypass switch 5 is closed, the potential of Vi becomes ground potential, close to 0V. The detection module will detect a significant drop in the potential of Vi and use the sudden change in this potential as the detection criterion.

[0079] In some embodiments, the observable electrical abrupt change criterion for selecting the closing of bypass switch 5 in step S102 is the voltage across the upper tube of the submodule, and the steps for determining the change in electrical abrupt change in step S104 are as follows:

[0080] The upper transistor of the tested submodule is turned on, and the upper and lower transistors of the submodule are connected in series in the same bridge arm. The DC capacitor voltage is discharged. When the voltage drops to the threshold value V3, a bypass switch closing command is issued. The potential difference between the collector and emitter of the upper transistor of the submodule is monitored by the collector-emitter potential difference detection module of the power semiconductor device in the drive unit, and the potential difference is sent to the control unit. The control unit detects the sudden change of the potential difference from 0 to a positive value and records this moment as the second closing moment t2.

[0081] It should be noted that after the upper transistor of the tested submodule is turned on, the potential difference between the collector and emitter of the lower transistor of the submodule is 0. When the bypass switch 5 is closed, the potential difference is close to the DC capacitor voltage. The detection module will detect a significant increase in the potential of Vi, and use the sudden change in this potential as the detection criterion.

[0082] In some embodiments, the observable electrical abrupt change criterion for selecting the closing of bypass switch 5 in step S102 is the DC capacitor voltage, and the steps for determining the change in electrical quantity in step S104 are as follows:

[0083] The output voltage of the first adjustable DC voltage source in the auxiliary power supply system 1 is increased. After the voltage increases to the threshold value V2, the bypass switch 5 is given a closing command. The control unit of the tested submodule monitors the rate of change of the DC capacitor voltage. The moment when the rate of change of the DC capacitor voltage changes from a positive value to a zero or negative value is recorded as the second closing time t2.

[0084] In some embodiments, the testing method further includes active reset and / or passive reset:

[0085] Active reset: After executing multiple rounds of test steps S102 to S105, it automatically enters S101 to recharge the submodule 4 that has not completed the test steps.

[0086] Passive reset: In step S103, it is determined that the DC capacitor voltage of the tested submodule has not changed with the adjustment of the auxiliary power supply system 1, and then returns to S101 to recharge.

[0087] It should be noted that setting active reset and / or passive reset is to prevent other submodules from being in bypass state while the tested submodule is being tested. The DC capacitor will discharge, and if the DC capacitor voltage is lower than the voltage required for the normal operation of the control system, the lower transistor of other submodules will be turned off due to the loss of drive power, thus disconnecting the charging circuit of the tested submodule. Active reset means that after each round of testing, the submodules that have not completed the test will be recharged. Passive reset means that when it is found that the tested submodule cannot be charged, the charging operation will be restarted.

[0088] Figure 3 shows a specific implementation plan considering the three criteria; Figure 4 shows the overall structure of the submodule bypass switch closing time test system.

[0089] In some embodiments, the negative terminal of the DC capacitor of the first submodule 4 in the converter chain 3 is defined as the third port D3, and the midpoint of the half-bridge of the Nth submodule 4 is defined as the first port D1. The auxiliary distribution system 2 includes M common-anode diodes, the cathodes of all diodes are connected to the positive terminal of the DC capacitor of the submodule under test, and the anodes of the M diodes are defined as the second port D2, where M is a positive integer less than or equal to N.

[0090] Figure 5 shows a first embodiment of the auxiliary power supply system: The auxiliary power supply system 1 includes a first adjustable DC voltage source DC1 and a charging and discharging resistor R. The positive terminal of the first adjustable DC voltage source is connected to the second port D2, and the negative terminal is connected to the third port D3. One end of the charging and discharging resistor is connected to the first port D1, and the other end is connected to the third port D3. The auxiliary power supply system 1 is used to complete the pre-charging step of step S101.

[0091] Figure 6 shows a second embodiment of the auxiliary power supply system: When the observable electrical change criterion for closing the bypass switch 5 is the DC capacitor voltage, if step S104 needs to be completed, an additional voltage regulating unit containing a second adjustable DC voltage source DC2, a first switch Q1, and a second switch Q2 needs to be added to the auxiliary power supply system. The voltage regulating unit is connected in series in the branch where the charging and discharging resistor is located. The voltage regulating unit includes a bypass branch and a power supply branch connected in parallel. The bypass branch has a first switch Q1, and the power supply branch has a second adjustable DC voltage source DC2 and a second switch Q2 connected in series.

[0092] It should be noted that the output voltage of the second adjustable DC voltage source is higher than that of the first adjustable DC voltage source, so that the auxiliary power supply system 1 can adjust the DC voltage of the submodule under test. When performing S101 pre-charging, the first switch Q1 is closed and the second switch Q2 is opened, and the charging circuit diagram of the submodule using the first adjustable DC voltage source is shown in Figure 7; when performing S104, the switch states are switched, the first switch Q1 is opened and the second switch Q2 is closed, and the charging circuit diagram of the submodule using the second adjustable DC voltage source is shown in Figure 8.

[0093] Accordingly, this application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the above-described submodule bypass switch closing time test method. Since the submodule bypass switch closing time test method has been described in detail above, it will not be repeated here.

[0094] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

Claims

1. A batch testing method for the closing time of bypass switches in a converter chain submodule, the test objects including a converter chain (3) and an auxiliary system, the converter chain (3) including N submodules (4), the submodules (4) being a half-bridge or full-bridge circuit structure composed of power semiconductors and DC capacitors, the AC ports of the submodules (4) being connected in parallel with bypass switches (5), the submodules (4) including control units, N being an integer greater than or equal to 2, the testing method including: The auxiliary system precharges the DC capacitor of the submodule (4) and sends a closing command to the bypass switch (5) using the control unit. The bypass switch (5) generates electrical abrupt changes before and after closing; The control unit detects the electrical sudden change and uses the difference between the time when the electrical sudden change occurs and the time when the closing command is issued as the closing time of the bypass switch (5). The steps of closing the bypass switch (5) and calculating the closing time are executed repeatedly to complete the batch test of the closing time of the bypass switch (5) of N sub-modules (4).

2. The batch testing method for the closing time of the bypass switch of the converter chain submodule as described in claim 1, wherein, The testing method specifically includes the following steps: S101: The submodule (4) that controls all the bypass switches (5) to be in the open state through the auxiliary system is precharged; S102: Select the submodule under test, and select the observable electrical change criterion for closing the bypass switch (5) as the voltage across the lower tube of the submodule, or the DC capacitor voltage, or the voltage across the upper tube of the submodule; the lower tube of the submodule is defined as a power semiconductor device connected in parallel with the bypass switch (5) of the submodule (4), and the upper tube of the submodule is connected in series with the lower tube of the submodule in the same bridge arm; S103: The control unit of the tested submodule actively or by receiving external instructions issues a closing command to the bypass switch (5) and records the time as the first closing time t1. S104: Determine that the observable electrical mutation of the tested submodule changes, and the control unit of the submodule (4) records the time as the second closing time t2; S105: The difference between the second closing time t2 and the first closing time t1 is determined as the closing time of the bypass switch (5) of the tested submodule; S106: Repeat steps S102 to S105 to obtain the closing time of the bypass switch (5) corresponding to all the sub-modules (4) when they are the tested sub-modules.

3. A batch testing method for the closing time of a bypass switch in a converter chain submodule as described in claim 2, wherein, The auxiliary system includes an auxiliary power supply system (1) and an auxiliary distribution system (2). The control unit includes a DC capacitor voltage sampling module. The submodule (4) further includes a drive unit, wherein: The auxiliary power system (1) includes a first adjustable DC voltage source, and the auxiliary distribution system (2) connects the auxiliary power system (1) and the DC capacitor of the submodule (4); The DC capacitor voltage sampling module is configured to sample the DC capacitor voltage of the sub-module under test to obtain the sampled value V1; The driving unit is configured to control the power semiconductor device to turn on and off, and the driving unit includes a power semiconductor device collector-emitter potential difference detection module.

4. A batch testing method for the closing time of a bypass switch in a converter chain submodule as described in claim 2, wherein, In step S103, the external command comes from the host computer; the host computer receives the DC capacitor voltage of the sub-module (4) through optical fiber, and sends the bypass switch (5) closing command to the sub-module under test through optical fiber; the control unit is set to send the bypass switch (5) closing time information to the host computer for data processing and storage.

5. A batch testing method for the closing time of a bypass switch in a converter chain submodule as described in claim 3, wherein, When the observable electrical mutation criterion for closing the bypass switch (5) in step S102 is the voltage across the lower tube of the submodule, the steps for determining the change in electrical mutation in step S104 are as follows: After issuing the closing command of the bypass switch (5), the potential difference between the collector and emitter of the power semiconductor device in the drive unit is monitored by the potential difference detection module between the collector and emitter of the lower tube of the submodule, and the potential difference is sent to the control unit. The control unit detects that the potential difference changes from 0 to a negative value and records this moment as the second closing time t2.

6. A batch testing method for the closing time of a bypass switch in a converter chain submodule as described in claim 3, wherein, When the observable electrical abrupt change criterion for closing the bypass switch (5) in step S102 is the voltage across the upper tube of the submodule, the steps for determining the change in electrical abrupt change in step S104 are as follows: The DC capacitor voltage is discharged when the test submodule is turned on. When the voltage drops to the threshold value V3, the bypass switch (5) is given a closing command. The potential difference between the collector and emitter of the power semiconductor device in the driving unit is monitored by the potential difference detection module, and the potential difference is sent to the control unit. The control unit detects that the potential difference changes from 0 to a positive value and records this moment as the second closing time t2.

7. A batch testing method for the closing time of a bypass switch in a converter chain submodule as described in claim 3, wherein, When the observable electrical change criterion for closing the bypass switch (5) in step S102 is the DC capacitor voltage, the steps for determining the change in electrical quantity in step S104 are as follows: Adjust the output voltage of the first adjustable DC voltage source in the auxiliary power system (1) to increase. After the voltage increases to the threshold value V2, issue a closing command to the bypass switch (5). The rate of change of the DC capacitor voltage is monitored by the control unit of the submodule under test; The control unit records the moment when the rate of change of the DC capacitor voltage changes from a positive value to a zero or negative value as the second closing time t2.

8. A batch testing method for the closing time of a bypass switch in a converter chain submodule as described in claim 7, wherein the testing method further includes active reset and / or passive reset: Active reset: After executing multiple rounds of test steps S102 to S105, it automatically enters S101 to recharge the submodule (4) that has not completed the test steps; Passive reset: In step S103, it is determined that the DC capacitor voltage of the tested submodule has not changed with the adjustment of the auxiliary power system (1), and the process returns to S101 to recharge.

9. A batch testing method for the closing time of a bypass switch in a converter chain submodule as described in claim 3, wherein, The negative terminal of the DC capacitor of the first sub-module (4) in the converter chain (3) is defined as the third port (D3), and the midpoint of the half-bridge of the Nth sub-module (4) is defined as the first port (D1); the auxiliary distribution system (2) includes M common anode diodes, the cathodes of all the diodes are connected to the positive terminal of the DC capacitor of the sub-module under test, the anodes of the M diodes are defined as the second port (D2), and M is a positive integer less than or equal to N.

10. A batch testing method for the closing time of a bypass switch in a converter chain submodule as described in claim 9, wherein, The auxiliary power system (1) further includes a charging and discharging resistor. The positive terminal of the first adjustable DC voltage source is connected to the second port (D2), and the negative terminal is connected to the third port (D3). One end of the charging and discharging resistor is connected to the first port (D1), and the other end is connected to the third port (D3).

11. A batch test method for the closing time of the bypass switch of the converter chain submodule as described in claim 10, when the observable electrical change criterion for closing the bypass switch (5) is selected as the DC capacitor voltage, the auxiliary power supply system (1) further includes a voltage regulating unit, which is connected in series on the branch where the charging and discharging resistor is located, and the voltage regulating unit includes a bypass branch and a power supply branch connected in parallel. The bypass branch includes a first switch (Q1), and the power supply branch includes a second adjustable DC voltage source and a second switch (Q2) connected in series. The output voltage of the second adjustable DC voltage source is higher than that of the first adjustable DC voltage source; When performing S101 pre-charging, the first switch (Q1) is closed and the second switch (Q2) is opened; When executing S104, the switch state is switched, the first switch (Q1) is opened, and the second switch (Q2) is closed.

12. A computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the submodule bypass switch closing time test method according to any one of claims 1-11.

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