CN113640709B - H-bridge cascade PET test method based on black box test - Google Patents

Abstract

The invention discloses an H-bridge cascade type PET test method based on black box test, which comprises a plurality of power conversion sub-modules, wherein each power conversion sub-module is controlled by a sub-module controller through an IGBT driver; the testing method comprises the following steps: s1, carrying out black box test on each power conversion sub-module, and if all the power conversion sub-modules have no defects, turning to the step S2 and the step S3; s2, carrying out black box test on the continuous running stability of PET; s3, performing black box test on the fault isolation capability of the PET; and if the test results of the S2 and the S3 meet the preset requirements, the PET test is passed. According to the black box test principle, if the test result of the current test item meets the requirement, the next test is carried out, and if the test result does not meet the requirement, the test result can be immediately fed back to an operator and the operator is assisted in overhauling and maintenance. The invention can realize comprehensive test of PET, improve the test efficiency and ensure the stability of PET in practical application.

Description

A H-bridge cascaded PET testing method based on black box testing

technical field

The invention relates to the technical field of AC/DC hybrid power distribution, in particular to a black box test-based H-bridge cascaded PET power module and a fault isolation function test method

Background technique

As a new type of power electronic equipment, the power electronic transformer (PET) can not only provide high-quality power for AC and DC loads, but also connect various new energy power generation systems safely and reliably. It has environmental protection, fault isolation, and harmonic suppression. The advent of power electronic transformers provides reliable support for overcoming multiple problems in the operation and use of existing power systems. Clean energy power generation will lead the mainstream of future power grid development. In the near future, new energy power will be implemented on a large scale to effectively reduce power grid security risks. With the support of a series of advanced technologies such as information technology, the advantages of power electronic transformers will be more obvious.

In order to ensure that the power electronic transformer can operate stably and reliably after it is put into operation, it is necessary to test the power electronic switching device and power module, and determine whether the power module meets the design and development requirements through testing; it is necessary to test the function of the power electronic transformer, and determine through the test Whether the power electronic transformer meets the functional design requirements, and whether it can realize fault protection and self-protection. In this context, the power module and functional testing methods of power electronic transformers are particularly important.

Due to the large number of internal sub-modules of the H-bridge cascaded PET, individual differences may exist, and some sub-modules may have problems such as weak pressure resistance and current resistance. If the inverter is not fully functionally tested, in extreme cases It will seriously damage the stability of the converter and even the system operation.

Glossary

Black box testing, that is, functional testing, when testing, treat all test items as a black box that cannot be opened as a whole, and test whether each function can be used normally without considering its internal structure and internal characteristics. . Both the cause-and-effect diagram method and the decision table method are common black-box testing methods, which are generally used in combination to determine the judgment conditions by mapping multiple inputs that interact with each other at the same time.

Contents of the invention

The object of the present invention is to provide a kind of H-bridge cascade type PET test method based on black box test, utilize black box test technology to carry out comprehensive test such as power module and fault isolation function to H bridge cascade type PET, improve test efficiency, Ensure the stability of PET in practical application.

The technical scheme adopted in the present invention is: a kind of H-bridge cascaded PET testing method, the H-bridge cascaded PET includes a plurality of power conversion sub-modules, and each power conversion sub-module is controlled by a sub-module controller through an IGBT driver; the testing method include:

S1. Black-box testing of each power conversion sub-module, including: simulating the operating environment of the power conversion sub-module, using the sub-module controller to output drive signals to the power conversion sub-module through the IGBT driver, and obtaining the operating parameters of the power conversion sub-module in real time , judging whether there is a defect in the power conversion sub-module according to the operating parameters;

If there are no defects in all power conversion sub-modules, go to step S2 and/or step S3;

S2, black-box test for the continuous operation stability of PET, including: simulating the operating environment of PET, making PET run continuously for a set time, using the sub-module controller equipped with voltage stabilization control function to control the power conversion sub-module, real-time Monitor the parameters of the PET operation process, and judge whether the continuous operation stability of the PET meets the preset requirements according to the PET operation parameters;

S3, conduct a black-box test on the fault isolation capability of PET, including: simulate the operating environment of the joint operation of PET and relay protection device, use the sub-module controller equipped with voltage stabilization control function to control the power conversion sub-module, simulate the inter-pole Short-circuit fault, real-time monitoring of PET operating process parameters before and after the fault, and judging whether the fault isolation capability of PET meets the preset requirements;

If the test results of S2 and S3 meet the preset requirements, the PET test is passed.

Optionally, in step S1, simulating the operating environment of the power conversion sub-module includes connecting a DC power supply at the bus side of the power conversion sub-module;

Using the sub-module controller to output a drive signal to the power conversion sub-module through the IGBT driver, obtain the operating parameters of the power conversion sub-module in real time, and judge whether the power conversion sub-module has a defect according to the operating parameters, including:

S11, performing a drive pulse test to determine whether the control signal output by the sub-module controller conforms to the preset control program logic;

S12, performing an IGBT drive test to determine whether the coordination performance between the IGBT driver and the IGBT meets the preset requirements;

S13, performing a rated power test of the power conversion sub-module, and judging whether the overall electrical performance, long-term stable operation capability, and transient short-term overload capacity of the power conversion sub-module meet the preset requirements;

S14, performing a protection function test of the power conversion sub-module, and judging whether the overcurrent protection capability of the power conversion sub-module in a short circuit condition meets a preset requirement;

If the tests of S11-S14 all pass, the power conversion sub-module test passes.

Further optionally, step S11 includes: obtaining the control signal output by the sub-module controller to the IGBT driver, comparing it with the control pulse signal corresponding to the preset control program logic, and judging the consistency between the two; obtaining The drive signal received by the power conversion sub-module is compared with the drive pulse signal corresponding to the control program logic, and the consistency between the two is judged; if the consistency meets the preset requirements, the drive pulse test passes , the control signal output by the sub-module controller conforms to the preset control program logic.

Optionally, step S12 includes: detecting the driving signal output by the IGBT, the IGBT turn-off voltage peak, the real-time voltage of the IGBT, the reverse recovery current and di/dt of the diode when the IGBT is turned on, and the sub-module current, and calculating the current increase and decrease rate According to the parameters obtained by detection and calculation, it is judged whether the coordination performance of the IGBT driver and the IGBT meets the preset requirements. The specific judgment basis can refer to the prior art, which can be automatic judgment by computer or manual judgment.

Optionally, step S13 includes: adding a DC power supply corresponding to the rated DC current at both ends of the power conversion sub-module, and controlling the on-off of the IGBT in the power conversion sub-module through the sub-module controller, so that the long-term stable operation of the converter is set time; after the long-term stable operation is completed, according to the device parameter specifications, conduct a short-term overload test under the set temperature and cooling mode. If the device is not damaged, the test passes. The state short-term overload capacity meets the requirements.

Optionally, in step S14, the performing the protection function test of the power conversion sub-module includes: testing whether the bridge arm IGBT of the power conversion sub-module is blocked in time under short-circuit conditions, and if it is blocked, the overcurrent protection capability of the power conversion sub-module meets the requirements of Require;

Step S14 also includes: testing the minimum turn-on voltage of the protection bypass thyristor, the period and duration of the trigger turn-on pulse of the protection bypass thyristor, and the shunt capability of the protection thyristor.

Optionally, in S2, the simulating the operating environment of the PET includes: connecting the PET to the medium and high voltage system according to the topology, and configuring a filter and a load on the DC side;

The use of a sub-module controller configured with a voltage stabilization control function to perform power conversion sub-module control, real-time monitoring of PET operating process parameters, and judging whether the continuous operation stability of PET meets preset requirements according to PET operating parameters include:

S21, energize the medium and high voltage system, put the PET into operation under voltage stabilization control, monitor the AC voltage and current, DC voltage, load power and capacitor voltage of the power conversion sub-module after the steady-state operation of the PET, and judge whether the data fluctuation obtained by monitoring conforms to The preset range, if it meets, the test is passed;

S22, conduct the AC-DC dynamic conversion power transmission function test, including: under the control of voltage stabilization, suddenly increase or decrease the load on the DC side of the power conversion sub-module, monitor the output power and DC current of the PET in real time, and judge whether the change of the DC current conforms to Changes in output power; after a sudden increase or decrease in load and reaching a steady state, judge whether the DC voltage of the PET remains within the preset voltage range, and whether the increase in load power and the growth rate meet the preset requirements; Passed the DC dynamic conversion power transmission function test;

If both the tests of S21 and S22 are passed, the PET's continuous operation stability test is passed.

Optionally, in S3, the operating environment of simulating the joint operation of the PET and the relay protection device includes: connecting the PET to a low-voltage system configured with a DC circuit breaker according to the topology, and configuring a filter and a partial load on the DC side;

The power conversion sub-module is controlled by using the sub-module controller configured with a voltage stabilization control function, simulating a short-circuit fault between poles, monitoring the operating process parameters of the PET before and after the fault in real time, and judging whether the fault isolation capability of the PET meets the preset requirements, include:

S31, configure the voltage stabilization control logic in the sub-module controller, power on the low-voltage system connected to the PET to put the PET into operation, and monitor the AC voltage and current, DC voltage, load power and power conversion sub-module capacitor voltage of the PET after steady-state operation ;

S32, simulating a short-circuit fault between poles, switching the PET to locked operation, and monitoring the PET AC current, DC voltage current, and sub-module capacitor voltage in real time. The voltage of the module capacitor drops rapidly. At this time, the PET can be blocked in time, and the power transmission of the system stops. It is judged that the PET has fault isolation capability, and then go to step S33;

S33, simulating inter-electrode short-circuit fault recovery, so that the PET returns to voltage stabilization control, real-time monitoring of the PET DC side voltage and current, AC current and power conversion sub-module capacitor voltage, if the PET resumes operation, the DC voltage gradually returns to the set value, When the AC current and DC current return to the normal operating value, the capacitor voltage of the power conversion sub-module returns to the set value, and the PET and the connected system operate normally, the fault isolation capability test of the PET passes.

Beneficial effect

The present invention uses a black box test method to test various performance indicators of the H-bridge cascaded PET, and can complete the voltage and current resistance electrical test of each sub-module of the PET, as well as the long-term stable operation capability and fault isolation function test of the PET. The test efficiency can be greatly improved, and it can ensure the safe and stable operation of the PET itself and the connected system after the PET is put into operation.

Description of drawings

Figure 1 shows a schematic diagram of the H-bridge cascaded PET topology;

Fig. 2 shows a kind of H-bridge cascade type PET test flow schematic diagram of the inventive method;

FIG. 3 is a schematic diagram of the principle of the H-bridge cascaded PET test causal diagram method based on the black box test of the present invention.

Implementation

It will be further described below in conjunction with the accompanying drawings and specific embodiments.

The technical idea of the present invention is: for the large number of sub-modules in the H-bridge cascade type PET, there are individual differences, there may be problems such as some sub-modules are weak in pressure resistance and flow resistance, and if the converter is not comprehensively In extreme cases, the functional test will seriously damage the stability of the inverter and even the system operation. The black box test method with high efficiency is used to perform functional tests on the sub-modules and PET in turn. Only when the current test item passes can the Carry out the next test item, and each time the item fails to pass the test, the specific test failure item and the reason for the test failure can be fed back to the system. It can improve test efficiency and ensure the reliability of test results.

Example 1

As shown in Figure 1, the H-bridge cascaded PET includes multiple power conversion sub-modules, and each power conversion sub-module is controlled by a sub-module controller through an IGBT driver.

This embodiment introduces a kind of H-bridge cascaded PET testing method based on black box testing technology, as shown in Fig. 2, including:

S1. Black-box testing of each power conversion sub-module, including: simulating the operating environment of the power conversion sub-module, using the sub-module controller to output drive signals to the power conversion sub-module through the IGBT driver, and obtaining the operating parameters of the power conversion sub-module in real time , judging whether there is a defect in the power conversion sub-module according to the operating parameters;

If there are no defects in all power conversion sub-modules, go to step S2 and step S3. Here, it is preferred to choose one of step S2 and step S3 to test first, and then no follow-up test is performed if any test item fails, or both were tested at the same time;

S2, black-box test for the continuous operation stability of PET, including: simulating the operating environment of PET, making PET run continuously for a set time, using the sub-module controller equipped with voltage stabilization control function to control the power conversion sub-module, real-time Monitor the parameters of the PET operation process, and judge whether the continuous operation stability of the PET meets the preset requirements according to the PET operation parameters;

S3, conduct a black-box test on the fault isolation capability of PET, including: simulate the operating environment of the joint operation of PET and relay protection device, use the sub-module controller equipped with voltage stabilization control function to control the power conversion sub-module, simulate the inter-pole Short-circuit fault, real-time monitoring of PET operating process parameters before and after the fault, and judging whether the fault isolation capability of PET meets the preset requirements;

If the test results of S2 and S3 meet the preset requirements, the PET test is passed.

Example 2

On the basis of Embodiment 1, this embodiment specifically introduces a kind of H-bridge cascaded PET test method based on black-box test technology. Map multiple inputs that interact with each other at the same time to determine the judgment conditions, further improving test efficiency.

Figure 3 shows the test causality diagram of this embodiment, in the diagram, cause-result is the direction from left to right in the diagram. The symbol ~ means illogical, if the cause is true, the result will not be true; the symbol ^ means and logic, if both the reasons are true, the result will be true; the symbol ∨ means or logic, if one of the reasons is true, then the result will be true. The reason-effect description is as follows:

Reason 1: 11-submodule function test;

Intermediate node 1: 21-indicates that the PET basic test has passed; 22-indicates that the PET basic test has failed, and specific sub-modules need to be overhauled;

Reason 2: 31-PET continuous operation test; 32-PET fault isolation capability test;

Intermediate node 2: 41-indicates that the functional test is passed; 42-indicates that the functional test fails, and informs the specific test failure items and reasons;

Results: 51-PET can work normally; 52-PET can't work normally.

When PET needs to be tested, the power conversion sub-module is given priority to functional and electrical tests. After the test is completed, the overall function test of the converter is carried out, including AC-DC conversion power transmission function and low voltage ride-through function. A black box with high efficiency is used. Test method, every time a project fails to pass the test, the specific test failure items and the reasons for the test failure can be fed back to the system, assisting the maintenance staff to troubleshoot and repair each fault item.

Specifically, this embodiment is executed according to the following steps.

1. Corresponding step S1: In order to ensure that the many internal sub-modules of the converter PET can meet the high power transmitted by medium and high-voltage power conversion and DC transmission, and various short-term electrical shocks during control strategy switching, it is proposed for the power conversion sub-module Functional and electrical test methods. The following power conversion sub-modules are briefly described as sub-modules.

First prepare the test equipment, including the main controller of the PET sub-module, test power supply and real-time monitoring equipment, connect the signal line of the main controller to the signal receiving port of the sub-module, connect the DC power supply to the electrical interface of the sub-module, and monitor the voltage of the sub-module with the real-time monitoring equipment current and other parameters. According to the principle of black-box testing, other test items are not considered when performing sub-module functional testing, and the test results are fed back to the operator to assist them in maintenance or next-step testing. Specifically include the following steps:

Step S11, conduct a drive pulse test to test whether the control signal meets the actual control requirements. After the main controller sends the IGBT on-off signal, verify whether the signal waveform sent by it is consistent with the program logic, and then check whether the signal received by the sub-module is consistent with the program logic.

Step S12, carry out the IGBT drive test, test the coordination performance of the IGBT driver and the IGBT, such as the test method of step 2, test the IGBT turn-off voltage peak, detect the real-time voltage of the IGBT, and detect the voltage peak when the IGBT is turned off; test the diode when the IGBT is turned on Reverse recovery current and di/dt, real-time monitoring of sub-module current and current increase and decrease rate.

Step S13: Perform a rated power test of the sub-module, test the overall electrical performance of the sub-module, test the long-term stable operation capability of the sub-module and the short-term overload capacity of the sub-module. According to the rated parameters of the sub-module, conduct a long-term operation test; after a long period of stable operation, perform a short-term overload test under the specified temperature and cooling method according to the device parameter specifications.

Step S14: Carry out the self-protection function test of the sub-module, test the over-current protection capability of the IGBT in the case of short circuit, whether the bridge arm IGBT is blocked in time in the case of short circuit, and if it is blocked, the over-current protection capability of the sub-module meets the actual operation requirements; test the bypass The minimum turn-on voltage of the thyristor; test the period and duration of the trigger turn-on pulse of the bypass thyristor and test the shunt capability of the protection thyristor.

According to the schematic diagram of the black box test, if the performance test of the sub-module passes, the next test will be carried out; if the performance test of the sub-module fails, it will be immediately fed back to the operator and assisted in its maintenance.

2. Corresponding step S2: In order to ensure the continuous, safe and stable power transmission of the PET, it is necessary to test the long-term stable operation of the proposed PET.

Prepare test equipment, including sub-module main controller, AC power supply, test monitoring system, load, etc. The controller is equipped with voltage stabilization control, AC voltage and current monitoring, DC voltage monitoring, load power monitoring and converter power unit voltage monitoring, and PET is connected to the medium and high voltage system. According to the principle of black-box testing, when performing PET long-term stable operation tests, other test items are not considered, and the test results are fed back to the operator to assist them in maintenance or next-step testing. Specifically include the following steps:

Step S21, the PET is connected to the medium and high voltage system, and the AC voltage and current output, the DC voltage output, the load power and the module capacitor voltage are monitored in real time after a steady state. Continuous operation for a long time, if the DC voltage and current is a stable DC waveform, the load power is stable, and the capacitor voltage of the sub-module fluctuates around the set value, it means that the converter is running normally in a steady state;

Step S22, sudden increase or decrease of load on the DC side. Under the voltage stabilization control, the output power of PET increases or decreases accordingly. The increase or decrease of the DC current is monitored in real time and conforms to the increase or decrease of the power. After reaching a steady state, the DC voltage remains at the set value. value, the load power increases and the increase meets the control design, and the AC-DC dynamic conversion power transmission function test of the converter is passed.

According to the schematic diagram of the black box test, if the PET long-term stable operation test meets the requirements, the next test will be carried out; if the PET long-term stable operation test fails, it will be immediately fed back to the operator and assisted in its maintenance.

3. Corresponding to step S3: considering that PET needs to have the ability to isolate AC and DC faults, a DC fault isolation test method is designed based on this.

First prepare the test device, including sub-module main controller, AC power supply, controllable DC power supply, real-time monitoring equipment, relay protection device, filter and load. Configure voltage stabilization control, AC voltage and current monitoring, DC voltage monitoring, load power monitoring, and converter power unit voltage monitoring in the main controller. In the test phase, the converter can be connected to the low-voltage system according to the topology for testing, and the DC side is equipped with a filter and a partial load. Since the short-circuit fault between poles is more serious, the test should be performed under a low-voltage system and equipped with a DC circuit breaker. According to the principle of black box testing, when testing the isolation ability of PET to faults, other test items are not considered, and the test results are fed back to the operator to assist them in maintenance or next test. Specifically include the following steps:

S31, configure the voltage stabilization control logic in the sub-module controller, power on the low-voltage system connected to the PET to put the PET into operation, and monitor the AC voltage and current, DC voltage, load power and power conversion sub-module capacitor voltage of the PET after steady-state operation ;

S32, simulating a short-circuit fault between poles, and switching the PET converter to a blocking operation. The main controller monitors the AC current, DC voltage and current, and the capacitor voltage of the sub-module in real time. If the AC and DC currents have a short-term impact when a fault occurs, the DC voltage and the capacitor voltage of the sub-module will drop rapidly. At this time, if the PET can be blocked in time , the system power transmission stops, indicating that the PET has fault isolation capability;

S33, simulating the recovery of short-circuit fault between poles, the PET returns to voltage stabilization control, the main controller monitors the DC side voltage and current, AC current and sub-module capacitor voltage in real time; after the PET resumes operation, the DC voltage gradually returns to the set value, and the AC current And the DC current returns to the normal operating value, the capacitor voltage of the sub-module returns to the set value, the PET and the system operate normally, and the fault isolation test is completed.

According to the schematic diagram of the black box test, if the fault isolation capability test of the PET meets the requirements, the next test will be carried out; if the fault isolation capability test of the PET fails, it will be immediately fed back to the operator and assisted in its maintenance.

In the above embodiments, by utilizing the black-box testing technology, it is possible to realize comprehensive testing of PET, improve testing efficiency, and ensure the stability of PET in practical applications.

Embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementations, and the above-mentioned specific implementations are only illustrative, rather than restrictive. Under the enlightenment of the present invention, many forms can also be made without departing from the gist of the present invention and the protection scope of the claims, and these all belong to the protection of the present invention.

Claims (7)

1. An H-bridge cascade PET test method comprises the steps that the H-bridge cascade PET comprises a plurality of power conversion submodules, and each power conversion submodule is controlled by a submodule controller through an IGBT driver; the testing method is characterized by comprising the following steps:

s1, performing black box testing on each power conversion sub-module, wherein the black box testing comprises the following steps: simulating the operation environment of the power conversion submodule, outputting a driving signal to the power conversion submodule by using a submodule controller through an IGBT driver, acquiring the operation parameters of the power conversion submodule in real time, and judging whether the power conversion submodule has defects according to the operation parameters; the operation environment of the analog power conversion sub-module comprises that a direct current power supply is connected to a bus side of the power conversion sub-module;

the method for judging whether the power conversion sub-module has defects or not according to the operation parameters by utilizing the sub-module controller to output a driving signal to the power conversion sub-module through the IGBT driver comprises the following steps:

s11, performing a driving pulse test, and judging whether a control signal output by the submodule controller accords with preset control program logic or not;

s12, performing IGBT driving test, and judging whether the matching performance of the IGBT driver and the IGBT meets the preset requirement;

s13, performing rated power test of the power conversion submodule, and judging whether the overall electrical performance, long-term stable operation capability and transient short-time overload capability of the power conversion submodule meet preset requirements or not;

s14, performing protection function test of the power conversion sub-module, and judging whether the overcurrent protection capability of the power conversion sub-module under the condition of short circuit meets the preset requirement;

if the tests of S11-S14 are all passed, the test of the power conversion submodule is passed;

if all the power conversion sub-modules have no defects, the step S2 and/or the step S3 is/are carried out;

s2, carrying out black box test on continuous running stability of PET, wherein the black box test comprises the following steps: simulating the running environment of the PET, enabling the PET to continuously run for a set time, performing power conversion submodule voltage stabilization control and alternating current-direct current dynamic conversion power transmission function test by using a submodule controller with a voltage stabilization control function, monitoring PET running process parameters in real time, and judging whether the continuous running stability of the PET meets preset requirements according to the PET running parameters; wherein the simulated PET operating environment comprises: the PET is connected into a medium-high voltage system according to a topological structure, and a filter and a load are configured on a direct current side;

s3, performing black box testing on the fault isolation capability of the PET, wherein the black box testing comprises the following steps: simulating the operation environment of the joint operation of the PET and the relay protection device, performing power conversion submodule control by using a submodule controller with a voltage stabilizing control function, simulating inter-electrode short circuit faults and fault recovery, monitoring the operation process parameters of the PET before and after the faults are recovered in real time, and judging whether the fault isolation capability of the PET meets preset requirements or not; the operation environment for simulating the joint operation of the PET and the relay protection device comprises the following steps: the PET is connected into a low-voltage system provided with a direct-current breaker according to a topological structure, and a filter and partial load are arranged on the direct-current side;

and if the test results of the S2 and the S3 meet the preset requirements, the PET test is passed.

2. The method according to claim 1, wherein step S11 comprises: the method comprises the steps of obtaining a control signal output by a sub-module controller to an IGBT driver, comparing the control signal with a control pulse signal corresponding to preset control program logic, and judging the consistency between the control signal and the control pulse signal; the driving signals received by the power conversion sub-module are obtained and compared with the driving pulse signals corresponding to the control program logic, and the consistency between the driving signals and the driving pulse signals is judged; if the consistency meets the preset requirement, the driving pulse test is passed, and the control signal output by the submodule controller accords with the preset control program logic.

3. The method according to claim 1, wherein step S12 comprises: detecting a driving signal output by the IGBT, an IGBT turn-off voltage peak, an IGBT real-time voltage, a reverse recovery current and di/dt of a diode when the IGBT is turned on, and a submodule current, calculating a current increase and decrease rate, and judging whether the coordination performance of the IGBT driver and the IGBT meets preset requirements according to parameters obtained by detection and calculation.

4. The method according to claim 1, wherein step S13 comprises: the direct current power supplies corresponding to rated direct current are added at the two ends of the power conversion submodule, and the on-off of the IGBT in the power conversion submodule is controlled by the submodule controller, so that the converter stably operates for a set time for a long time; after the long-term stable operation is finished, short-time overload test is carried out under the set temperature and the cooling mode according to the parameter specification of the device, if the device is not damaged, the test is passed, and the overall electrical performance, the long-term stable operation capability and the transient short-time overload capability of the power conversion sub-module meet the requirements.

5. The method according to claim 1, wherein in step S14, the performing a protection function test of the power conversion sub-module includes: testing whether a bridge arm IGBT of the power conversion sub-module is locked in time under the condition of short circuit, and if so, conforming to the requirement on the overcurrent protection capability of the power conversion sub-module;

step S14 further includes: and testing the minimum opening voltage of the protection bypass thyristor, the period and the duration of the triggering opening pulse of the protection bypass thyristor, and the shunt capacity of the protection thyristor.

6. The method according to claim 1, wherein in S2, the performing power conversion submodule control by using a submodule controller configured with a voltage-stabilizing control function, monitoring PET operation process parameters in real time, and determining whether continuous operation stability of the PET meets a preset requirement according to the PET operation parameters includes:

s21, electrifying a medium-high voltage system to enable the PET to be put into operation under voltage stabilization control, monitoring alternating voltage and current, direct current and load power after the PET runs stably and capacitor voltage of a power conversion submodule, judging whether the fluctuation of data obtained through monitoring accords with a preset range, and if so, passing the test;

s22, performing an AC/DC dynamic conversion power transmission function test, including: under voltage stabilizing control, the load on the direct current side of the sudden increase or sudden decrease power conversion submodule monitors the output power and direct current of the PET in real time, and judges whether the change of the direct current accords with the change of the output power; after the sudden increase or the sudden decrease of the load reaches a steady state, judging whether the direct current voltage of the PET is kept within a preset voltage range and whether the increase and increase amplitude of the load power meets preset requirements; if all the power signals accord with the power transmission function test, the AC/DC dynamic conversion power transmission function test is passed;

if both the tests of S21 and S22 are passed, the continuous operation stabilization capability test of PET is passed.

7. The method according to claim 1, wherein in S3, the performing power conversion sub-module control by using the sub-module controller with the voltage stabilizing control function, simulating an inter-electrode short circuit fault, monitoring operation process parameters of the PET before and after the fault in real time, and determining whether fault isolation capability of the PET meets a preset requirement includes:

s31, configuring voltage stabilizing control logic in a submodule controller, electrifying a low-voltage system connected with the PET to enable the PET to be put into operation, and monitoring alternating current voltage and current, direct current voltage, load power and power conversion submodule capacitor voltage after the PET is in steady-state operation;

s32, simulating an interelectrode short circuit fault, switching PET to a blocking operation, monitoring PET alternating current, direct current voltage and current and submodule capacitor voltage in real time, if short-time current impact occurs in alternating current and direct current during faults, the direct current voltage and the capacitor voltage of the power conversion submodule rapidly drop, at the moment, the PET can be blocked in time, and system power transmission is stopped, and judging that the PET has fault isolation capability, and then, turning to the step S33;

s33, simulating interelectrode short circuit fault recovery, enabling the PET to be recovered to voltage stabilizing control, monitoring voltage and current at the direct current side of the PET, alternating current and capacitor voltage of the power conversion submodule in real time, if the PET is recovered to run, the direct current voltage is gradually recovered to a set value, the alternating current and the direct current are recovered to normal running values, the capacitor voltage of the power conversion submodule is recovered to the set value, and the PET and an accessed system run normally, and then the fault isolation capability test of the PET is passed.