Method and device for processing VFTO (Very Fast Transient Overvoltage) invasion of flexible direct-current converter valve

Abstract

The invention relates to a method and a device for processing VFTO invasion of a flexible direct current converter valve, and the method comprises the steps: building a flexible direct current converter valve tower model which comprises an alternating current side power module, a GIS pipeline module, a converter valve module and a wire module, and enabling the alternating current side power module to be connected with the converter valve module through the GIS pipeline module and the wire module which are connected in sequence; building an experimental circuit loop matched with the flexible direct-current converter valve tower model so as to test overvoltage characteristics of sub-module ports in the converter valve; establishing a simulation model equivalent to the flexible direct current converter valve tower model; obtaining a measurement result of a specified position in the experimental circuit loop, and comparing the measurement result with a simulation result of a corresponding position in the simulation model; and if the comparison result is consistent, determining that the flexible direct-current converter valve tower model is effective, and analyzing and processing the interference of the VFTO on the converter valve in the actual working condition based on the flexible direct-current converter valve tower model. According to the method, the interference of the VFTO on the converter valve in the actual working condition can be accurately and effectively analyzed and processed.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore wind power generation, and in particular to a method and a device for processing a flexible direct current converter valve disturbed by a VFTO. Background Art

[0002] Offshore wind resources are abundant and have a high annual utilization hours. Therefore, the development of offshore wind power generation has become a general trend. From 2015 to 2021, the average annual growth rate of installed capacity was close to 30%. By the end of 2021, the cumulative installed capacity of offshore wind power in operation worldwide reached 57GW, of which the newly installed capacity in 2021 was 21.1GW, maintaining a high growth trend.

[0003] In the process of developing renewable energy, flexible direct current transmission is an important technical means for large-scale wind power and photovoltaic renewable energy consumption, centralized offshore wind power transmission, grid interconnection, and urban power supply. After more than ten years of development in my country and the support of multiple flexible direct current projects, the development of flexible direct current conversion technology has basically matured. However, the current flexible direct current converter station equipment uses a large number of switchgear and overhead line connections, which occupy a large area and are difficult to integrate, which is not conducive to its application in tight land use scenarios such as offshore platforms, urban power supply, and Gobi hilly areas. Previously, there was an offshore project in China where all flexible direct current equipment was installed on an offshore converter platform and a large number of GIS equipment were used. During operation, a VFTO breakdown and damage to the converter valve submodule occurred due to the operation of the GIS equipment. The damage mechanism is still unclear, which greatly affected the operational reliability of my country's offshore wind power flexible direct current transmission project. At the end of 2021, when the GIS isolation switch on the AC side of the Rudong wind power flexible direct current transmission project was opened, a large number of submodules in the flexible direct current converter valve tower near the interference source had power electronic devices damaged.

[0004] However, in the existing research on VFTO, there is only research on measuring the VFTO waveform of the GIS outlet port to the ground, but there is a lack of research on the impact of VFTO on the subsequent converter valve. Therefore, a solution for the treatment of semiconductor devices in the converter valve under VFTO conditions is urgently needed. Summary of the invention

[0005] The object of the present invention is to provide a method and device for processing a flexible DC converter valve disturbed by VFTO, aiming to effectively analyze and process the interference of VFTO on the converter valve in actual working conditions.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for processing a flexible DC converter valve being disturbed by VFTO, the method for processing a flexible DC converter valve being disturbed by VFTO comprising:

[0007] Establishing a flexible DC converter valve tower model, the flexible DC converter valve tower model includes an AC side power supply module, a GIS pipeline module, a converter valve module and a wire module, wherein the AC side power supply module is connected to the converter valve module via the GIS pipeline module and the wire module which are connected in sequence;

[0008] Building an experimental circuit loop matching the flexible DC converter valve tower model to test the overvoltage characteristics of the submodule port of the converter valve; and establishing a simulation model equivalent to the flexible DC converter valve tower model;

[0009] Obtaining a measurement result of a specified position in the experimental circuit loop, and comparing the measurement result with a simulation result of a corresponding position in the simulation model;

[0010] If the comparison results are consistent, it is determined that the flexible DC converter valve tower model is valid, and the interference of VFTO on the converter valve in actual working conditions is analyzed and processed based on the flexible DC converter valve tower model.

[0011] Preferably, the AC side power supply module includes a capacitor with an initial voltage; the GIS pipeline module adopts a frequency-dependent phase domain transmission line model; and the wire module adopts a resistance and / or capacitance model equivalent for connecting the GIS to the valve.

[0012] Preferably, the nine submodules in the converter valve module form a valve section.

[0013] Preferably, the experimental circuit loop includes: a converter valve, an isolating switch, a control switch, a discharge resistor, a circuit breaker and a DC power supply, wherein one end of the converter valve is connected to one end of the isolating switch, and the other end of the isolating switch is grounded via the control switch and the discharge resistor, and the DC power supply is connected to the circuit breaker and then connected in parallel to both ends of the converter valve, and the other end of the converter valve is grounded.

[0014] Preferably, the converter valves in the experimental circuit loop are sourced from one and a half layers of the entire converter valve tower, and the converter valve tower is configured to be able to withstand an insulation level of a specified steady-state voltage and enable each submodule of each valve tower to be stably charged simultaneously and reach a rated voltage.

[0015] Preferably, the step of testing the overvoltage characteristics of the submodule port in the converter valve by using the experimental circuit loop includes:

[0016] Ensure that the capacitors of each submodule in the converter valve tower are not charged, and the control switch, circuit breaker and isolating switch in the GIS are all in the disconnected state;

[0017] The control switch is closed to ensure that the potential on the left side of the GIS is close to zero potential, so that the isolating switch in the GIS has a larger voltage difference;

[0018] The circuit breaker is closed, and the DC power supply charges the converter valve tower;

[0019] Disconnect the control switch and the circuit breaker setting trigger, close the isolating switch in the GIS, complete a single test, and record the data;

[0020] Closing the control switch to release the voltage in the capacitor in the converter valve tower;

[0021] After the discharge is completed, disconnect the isolating switch in the GIS to complete the single test.

[0022] Preferably, the step of testing the overvoltage characteristics of the submodule port in the converter valve by the experimental circuit loop further includes:

[0023] Before starting the test, the initial capacitor voltage of the converter valve submodule is set to a specified rated voltage.

[0024] Preferably, the step of obtaining the measurement result of a specified position in the experimental circuit loop includes:

[0025] In the experimental circuit loop, at least three measurement systems are respectively arranged at ports of the sub-modules in the valve, and measurement results of at least three measurement systems are obtained.

[0026] Preferably, the overvoltage characteristics of the submodule port in the converter valve include the voltage amplitude, wavefront steepness and / or frequency of the submodule port.

[0027] In a second aspect, the present invention provides a device comprising the flexible DC converter valve tower model as described above.

[0028] The beneficial effects of adopting the above embodiment are:

[0029] By establishing a flexible DC converter valve tower model and verifying its accuracy through the corresponding experimental circuit loop and simulation model, we can explore the port voltage of VFTO acting on the converter valve submodule under the most extreme actual working conditions, provide a theoretical basis for engineering practice, and then accurately and effectively analyze and deal with the interference of VFTO on the converter valve under actual working conditions. Build an equivalent experimental platform to restore the actual working conditions to the greatest extent, and use the simulation results to guide the actual commissioning system to improve the system stability and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Circuit diagram for generating VFTO for opening GIS disconnector;

[0031] Figure 2 A method flow chart of an embodiment of a method for processing a flexible DC converter valve disturbed by VFTO provided in the present application;

[0032] Figure 3A schematic structural diagram of a flexible DC converter valve tower model in an embodiment of a method for treating a flexible DC converter valve disturbed by VFTO provided in the present application;

[0033] Figure 4 A circuit diagram of an experimental circuit loop in an embodiment of a method for processing a flexible DC converter valve disturbed by VFTO provided in the present application;

[0034] Figure 5 A schematic structural diagram of a converter valve in an embodiment of a method for treating a flexible DC converter valve disturbed by VFTO provided in the present application;

[0035] Figure 6 A flowchart of an experimental circuit loop test of overvoltage characteristics of a submodule port in a converter valve in an embodiment of a method for processing a flexible DC converter valve disturbed by VFTO provided in the present application;

[0036] Figure 7 A structural schematic diagram of a simulation model in an embodiment of a method for processing a flexible DC converter valve disturbed by VFTO provided in the present application;

[0037] Figure 8 A schematic diagram of the arrangement of measurement points in an embodiment of a method for treating a flexible DC converter valve disturbed by VFTO provided in the present application;

[0038] Fig. 9 A waveform comparison diagram of experimental results and simulation results at five measurement points in an embodiment of a method for treating a flexible DC converter valve disturbed by VFTO provided in the present application;

[0039] Fig.10 This is a waveform comparison diagram of the engineering results and experimental results of the first nine submodules in an embodiment of a method for processing a flexible DC converter valve disturbed by VFTO provided in the present application. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] It should be noted that the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0042] With regard to the VFTO breakdown and damage to the converter valve submodule caused by the operation of GIS equipment during operation, the inventors of this application have found through research that the operation of the isolation switch is the main cause of the very fast transient overvoltage (VFTO). Figure 1 As shown, VFTO has the characteristics of steep wavefront, high amplitude and frequency. The maximum amplitude is close to 2.0pu~3.0pu, the maximum wavefront steepness can reach tens of kV / ns, and the maximum frequency is up to hundreds of MHz.

[0043] Based on this, the present application provides a method, system, electronic device and storage medium for processing a flexible DC converter valve disturbed by VFTO, which are described in detail below.

[0044] Reference Figure 2 A method flow chart of an embodiment of a method for processing a flexible DC converter valve disturbed by VFTO provided in the present application, the method comprising the following steps:

[0045] S1. Establishing a flexible DC converter valve tower model, wherein the flexible DC converter valve tower model comprises an AC side power supply module, a GIS pipeline module, a converter valve module and a wire module, wherein the AC side power supply module is connected to the converter valve module via the GIS pipeline module and the wire module which are connected in sequence;

[0046] S2. Building an experimental circuit loop matching the flexible DC converter valve tower model to test the overvoltage characteristics of the submodule port of the converter valve; and establishing a simulation model equivalent to the flexible DC converter valve tower model;

[0047] S3, obtaining a measurement result of a specified position in the experimental circuit loop, and comparing the measurement result with a simulation result of a corresponding position in the simulation model;

[0048] S4. If the comparison results are consistent, it is determined that the flexible DC converter valve tower model is valid, and the interference of VFTO on the converter valve in actual working conditions is analyzed and processed based on the flexible DC converter valve tower model.

[0049] This embodiment establishes a flexible DC converter valve tower model, and after verifying its accuracy through the corresponding experimental circuit loop and simulation model, it can explore the port voltage of the VFTO acting on the converter valve submodule under the most extreme actual working conditions, provide a theoretical basis for engineering practice, and then accurately and effectively analyze and deal with the interference of VFTO on the converter valve under actual working conditions. Build an equivalent experimental platform to restore the actual working conditions to the greatest extent, and guide the actual commissioning system through the simulation results to improve the system stability and economy.

[0050] Specifically, this embodiment firstly establishes an equivalent model of the offshore converter platform in the project, namely, the flexible DC converter valve tower model. In order to verify the accuracy of the model and combine the existing GIS equipment in the laboratory, an experimental circuit loop and an experimental simulation model are designed. The accuracy of the offshore converter platform model is verified by comparing the experimental results with the laboratory simulation model. Finally, the submodule port overvoltage characteristics (voltage amplitude, du / dt) of the experimental simulation model and the engineering simulation model are analyzed, and a valve-level equivalent test method for the flexible DC converter valve affected by VFTO is proposed. The key to the experiment lies in the accuracy of the submodule parameters, that is, whether the experimental results are consistent with the simulation results.

[0051] This embodiment proposes a valve-level equivalent test method for flexible DC converter valves subject to VFTO interference, and builds a VFTO equivalent test platform for converter valves. This is conducive to improving the development and testing capabilities of converter valves, providing a valve-level equivalent test method for converter valves subject to VFTO interference, and providing a verification scheme and inspection standard for the future VFTO interference resistance capability of offshore converter valves.

[0052] Further, in some embodiments, first, based on the Borwin6 offshore converter platform, an equivalent model is built in pscad, such as Figure 3 As shown, the model takes into account the AC power supply, GIS pipeline, converter valve, and wires connecting GIS to the valve. The AC power supply is equivalent to a capacitor with an initial voltage, the GIS pipeline adopts a frequency-dependent phase domain transmission line model (divided into seven sections according to the actual physical structure diagram), the 9 submodules in the converter valve tower are one valve section, and there are 16 valve sections in total (considering the stray capacitance between valve layers), and the wires connecting GIS to the valve are equivalent to resistance and capacitance models. Since the voltage value of VFTO can take any value, the overvoltage characteristics (voltage amplitude, du / dt) of the submodules in the converter valve under the most severe working conditions of VFTO (when taking the maximum reverse voltage) are simulated, and the accuracy of the equivalent model needs to be verified.

[0053] Furthermore, an experimental circuit loop that meets laboratory conditions is designed, which includes: a converter valve, an isolating switch, a control switch, a discharge resistor, a circuit breaker, and a DC power supply, wherein one end of the converter valve is connected to one end of the isolating switch, and the other end of the isolating switch is grounded through the control switch and the discharge resistor, and the DC power supply is connected to the circuit breaker and then connected in parallel to the two ends of the converter valve, and the other end of the converter valve is grounded. Figure 4 As shown, in the experimental circuit loop, the converter valve and the isolating switch are directly connected, one side of the isolating switch is connected to the control switch, i.e., switch S1, and is connected to the discharge resistor R; a DC power supply is connected in parallel on both sides of the converter valve, and the DC power supply is connected to the converter valve tower through a circuit breaker S2.

[0054] like Figure 5 The figure shows the structure of the converter valve, and one and a half layers of the converter valve tower are used as the test object. During the test, the converter valve tower in the project needs to be supported to the actual height of the project (with an insulation level that can withstand a steady-state voltage of 400kV), and each submodule of each valve tower needs to be stably charged at the same time and reach the rated voltage of 2.4kV.

[0055] like Figure 6 As shown, the initial capacitor voltage of the converter valve submodule is taken as the rated voltage 2.4kV for testing. The steps of testing the overvoltage characteristics of the submodule port in the converter valve by the experimental circuit loop include:

[0056] (1) Ensure that the capacitors of each submodule in the converter valve tower are not charged, and that the switch S1, circuit breaker S2 and the isolating switch in the GIS are all in the disconnected state;

[0057] (2) Close switch S1 to ensure that the potential on the left side of the GIS is close to zero potential so that the isolating switch in the GIS has a larger voltage difference;

[0058] (3) Close circuit breaker S2, and the DC power supply charges the converter valve tower;

[0059] (4) Disconnect switch S1 and circuit breaker S2 to set the trigger, close the isolating switch in the GIS, complete the single test, and record the data;

[0060] (5) Close switch S1 to release the voltage in the capacitor in the converter valve tower;

[0061] (6) After the discharge is completed, disconnect the isolating switch in the GIS to complete the single test.

[0062] Then, an equivalent simulation model in the laboratory was built in pscad, such as Figure 7As shown in the figure, the parameters of the AC side power supply model and submodules of the simulation model are consistent with the flexible DC converter valve tower model selected in the project. The GIS pipeline also adopts the phase domain transmission model (selected according to the existing GIS). During the experiment, there are 5 measurement systems arranged at the ports of the submodules in the valve, as shown in the figure. Figure 8 As shown in the figure, the results of these five measurement points are compared with the simulation results of the corresponding positions of the simulation model to ensure that the parameters of the sub-modules in the simulation model are accurate, thereby verifying the accuracy of the offshore converter platform model, namely the flexible DC converter valve tower model.

[0063] Finally, an experimental method for the equivalent of the flexible DC converter valve level VFTO is proposed. The submodule overvoltage characteristics obtained in the laboratory are equivalent to the submodule overvoltage characteristics obtained in the offshore converter platform simulation, that is, whether the voltage amplitude and du / dt of the submodule port in the laboratory are consistent with the voltage amplitude and du / dt of the module port in the project, if they are consistent, the validity of the experiment can be verified.

[0064] Specifically, a high-voltage probe was used during the experiment to measure the port voltage of the submodule. A total of 5 measurement points were arranged in the laboratory. The waveforms obtained were compared with the simulation results of the submodules at the corresponding positions. The results are as follows: Fig. 9 As shown, it can be found that the simulation results can better reflect the actual experimental results in the laboratory, thereby verifying the accuracy of the laboratory simulation model and the offshore converter platform model.

[0065] In order to make the overvoltage characteristics of the submodules under laboratory conditions equivalent to the overvoltage characteristics of the submodules under the most extreme working conditions in engineering, the engineering results of the first nine submodules were compared with the experimental results. It was found that the voltage peak and du / dt of the submodules in the laboratory model were consistent with those in engineering. The voltage amplitude was 4.8kV and the du / dt was 180kV / us. Fig.10 As shown, the experimental method of valve-level VFTO equivalence of flexible DC converter valve is verified.

[0066] This embodiment establishes a flexible DC converter valve tower model based on the Borwin6 project standard, which can explore the port voltage of the VFTO acting on the submodule under the most extreme actual working conditions, and provide a theoretical basis for engineering practice. Build an equivalent experimental platform to restore the actual working conditions to the greatest extent, and guide the actual commissioning system through the simulation results, thereby improving the system stability and economy. Furthermore, this embodiment can intuitively observe the peak voltage of each submodule through the obtained waveform diagram, and more intuitively observe the overvoltage characteristics of the submodule in each valve section, providing theoretical support for the characteristics of the converter valve for the offshore converter platform.

[0067] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0068] This embodiment also provides a device, which includes the flexible DC converter valve tower model as described above. For the specific definitions of each module in the flexible DC converter valve tower model, please refer to the definitions of the above embodiments, which will not be repeated here. Each module in the above flexible DC converter valve tower model can be implemented in whole or in part by software, hardware and a combination thereof. The above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0069] The device may be a device that can automatically perform numerical calculations and / or information processing according to pre-set or stored instructions. The device may be a computer, or a single network server, a server group consisting of multiple network servers, or a cloud based on cloud computing consisting of a large number of hosts or network servers, wherein cloud computing is a type of distributed computing, a super virtual computer consisting of a group of loosely coupled computers. (The device may be a terminal device with storage and computing functions, such as a server, a smart phone, a tablet computer, a portable computer, a desktop computer, etc. In one embodiment, when the device is a server, the server may be one or more of a rack server, a blade server, a tower server, a cabinet server, etc.)

[0070] In this embodiment, the device may also include, but not limited to, a memory, a processor, and a network interface that can be interconnected through a system bus, wherein the memory includes an internal memory and at least one type of readable storage medium. The internal memory provides a cache for the operation of the device; the readable storage medium may be a non-volatile storage medium such as a flash memory, a hard disk, a multimedia card, a card-type memory (e.g., SD or DX memory, etc.), a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM), a magnetic memory, a magnetic disk, an optical disk, etc. In some embodiments, the readable storage medium may be an internal storage unit of the device, such as a hard disk of the device; in other embodiments, the non-volatile storage medium may also be an external storage device of the device, such as a plug-in hard disk equipped on the device, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. In this embodiment, the readable storage medium of the memory is generally used to store an operating system and various application software installed on the device. In addition, the memory may also be used to temporarily store various types of data that have been output or are to be output.

[0071] The processor may be a central processing unit (CPU), a controller, a microcontroller, a microprocessor, or other data processing chip in some embodiments. The processor is generally used to control the overall operation of the device, such as performing control and processing related to data interaction or communication with the other devices. In this embodiment, the processor is used to run the program code stored in the memory or process data.

[0072] The network interface may include a wireless network interface or a wired network interface, which is generally used to establish a communication connection between the device and other electronic devices.

[0073] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0074] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for enabling a terminal device (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present invention.

[0075] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but the scope of the present invention is not limited thereto. The serial numbers of the embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments. In addition, although the logical order is shown in the flow chart, in some cases, the steps shown or described can be performed in a different order than that shown here.

[0076] Those skilled in the art may implement the present invention in a variety of variations without departing from the scope and essence of the present invention, such as using a feature of one embodiment to obtain another embodiment. Any modification, equivalent substitution and improvement made within the technical concept of the present invention shall be within the scope of the present invention.

Claims

1. A method for treating a flexible DC converter valve disturbed by VFTO, characterized in that: The method for processing the flexible DC converter valve being disturbed by VFTO includes: Establishing a flexible DC converter valve tower model, the flexible DC converter valve tower model includes an AC side power supply module, a GIS pipeline module, a converter valve module and a wire module, wherein the AC side power supply module is connected to the converter valve module via the GIS pipeline module and the wire module which are connected in sequence; Building an experimental circuit loop matching the flexible DC converter valve tower model to test the overvoltage characteristics of the submodule port of the converter valve; and establishing a simulation model equivalent to the flexible DC converter valve tower model; Obtaining a measurement result of a specified position in the experimental circuit loop, and comparing the measurement result with a simulation result of a corresponding position in the simulation model; If the comparison results are consistent, it is determined that the flexible DC converter valve tower model is valid, and the interference of VFTO on the converter valve in actual working conditions is analyzed and processed based on the flexible DC converter valve tower model.

2. The method for treating a flexible DC converter valve disturbed by VFTO according to claim 1, characterized in that: The AC side power supply module includes a capacitor with an initial voltage; the GIS pipeline module adopts a frequency-dependent phase domain transmission line model; the wire module adopts a resistance and / or capacitance model equivalent, which is used to connect the GIS to the valve.

3. The method for treating a flexible DC converter valve disturbed by VFTO according to claim 2, characterized in that: The nine submodules in the converter valve module form a valve section.

4. The method for treating a flexible DC converter valve disturbed by VFTO according to claim 1, characterized in that: The experimental circuit loop includes: a converter valve, an isolating switch, a control switch, a discharge resistor, a circuit breaker and a DC power supply, wherein one end of the converter valve is connected to one end of the isolating switch, and the other end of the isolating switch is grounded via the control switch and the discharge resistor. The DC power supply is connected to the circuit breaker and then connected in parallel to the two ends of the converter valve, and the other end of the converter valve is grounded.

5. The method for treating a flexible DC converter valve disturbed by VFTO according to claim 4, characterized in that: The converter valves in the experimental circuit loop are from one and a half layers of the converter valve tower. The converter valve tower is configured to be able to withstand the insulation level of a specified steady-state voltage and enable each submodule of each valve tower to be stably charged simultaneously and reach the rated voltage.

6. The method for treating a flexible DC converter valve disturbed by VFTO according to claim 4 or 5, characterized in that: The steps of testing the overvoltage characteristics of the submodule port of the converter valve by the experimental circuit loop include: Ensure that the capacitors of each submodule in the converter valve tower are not charged, and the control switch, circuit breaker and isolating switch in the GIS are all in the disconnected state; The control switch is closed to ensure that the potential on the left side of the GIS is close to zero potential, so that the isolating switch in the GIS has a larger voltage difference; The circuit breaker is closed, and the DC power supply charges the converter valve tower; Disconnect the control switch and the circuit breaker setting trigger, close the isolating switch in the GIS, complete a single test, and record the data; Closing the control switch to release the voltage in the capacitor in the converter valve tower; After the discharge is completed, disconnect the isolating switch in the GIS to complete the single test.

7. The method for treating a flexible DC converter valve disturbed by VFTO according to claim 6, characterized in that: The step of testing the overvoltage characteristics of the submodule port of the converter valve by the experimental circuit loop also includes: Before starting the test, the initial capacitor voltage of the converter valve submodule is set to a specified rated voltage.

8. The method for treating a flexible DC converter valve disturbed by VFTO according to any one of claims 1 to 5, characterized in that: The obtaining of the measurement result of the specified position in the experimental circuit loop includes: In the experimental circuit loop, at least three measurement systems are respectively arranged at ports of the sub-modules in the valve, and measurement results of at least three measurement systems are obtained.

9. The method for treating a flexible DC converter valve disturbed by VFTO according to any one of claims 1 to 5, characterized in that: The overvoltage characteristics of the submodule port in the converter valve include the voltage amplitude, wavefront steepness and / or frequency of the submodule port.

10. A device, characterized in that: The method comprises a flexible DC converter valve tower model in the method for treating a flexible DC converter valve disturbed by VFTO as described in any one of claims 1 to 9.

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