Stability verification method, system, device, controller, medium and program product

Abstract

The present application relates to a stability verification method, system, device, controller, medium and program product. The method includes: obtaining the type of the target DC transmission topology to be verified; according to the type of the target DC transmission topology, building a target equivalent subsystem corresponding to the target DC transmission topology through multiple converters in a DC equivalent system; the multiple converters in the DC equivalent system are combined and connected through switches for building equivalent subsystems corresponding to different types of DC transmission topologies; performing a simulated back-to-back test on each converter in the target equivalent subsystem to obtain a plurality of simulated electrical parameters; and determining a stability verification result of the target DC transmission topology according to the plurality of simulated electrical parameters. By using this method, it is possible to more simply verify the stability of various DC transmission topologies.

Description

Technical Field

[0001] This application relates to the technical field of HVDC transmission, and particularly to a stability verification method, system, device, controller, medium, and program product. Background Art

[0002] For scenarios such as desert, Gobi, and waste land new energy, and integrated water, wind, and light bases, HVDC transmission needs to comprehensively consider requirements such as grid constraints on the sending and inverting sides, grid support under multiple application scenarios, high and low voltage ride-through, and commutation failure resistance. The transmission topologies in such scenarios include various different types of HVDC transmission topologies.

[0003] In related technologies, for various HVDC transmission topologies, mainly the converters in each HVDC transmission topology are respectively subjected to reliability verification, and based on the verification results, the stability of each HVDC transmission topology is determined. However, this reliability verification method is relatively complex.

[0004] Therefore, there is an urgent need for a method that can more simply verify the stability of various HVDC transmission topologies. Summary of the Invention

[0005] Based on this, in view of the above technical problems, it is necessary to provide a stability verification method, system, device, controller, medium, and program product that can more simply verify the stability of various HVDC transmission topologies.

[0006] In a first aspect, this application provides a stability verification method, including:

[0007] Obtain the type of the target HVDC transmission topology to be verified;

[0008] According to the type of the target HVDC transmission topology, build a target equivalent subsystem corresponding to the target HVDC transmission topology through multiple converters in the DC equivalent system; the multiple converters in the DC equivalent system are combined and connected through switches for building equivalent subsystems corresponding to different types of HVDC transmission topologies;

[0009] Conduct simulated back-to-back tests on each converter in the target equivalent subsystem to obtain multiple simulated electrical parameters;

[0010] Determine the stability verification result of the target HVDC transmission topology according to the multiple simulated electrical parameters.

[0011] In one of the embodiments, obtaining the type of the target HVDC transmission topology to be verified includes:

[0012] According to the topological structure of the target HVDC transmission topology to be verified, determine at least one converter type on the rectifier side and at least one converter type on the inverter side in the target HVDC transmission topology.

[0013] In one embodiment, according to the type of the target DC power transmission topology, a target equivalent subsystem corresponding to the target DC power transmission topology is built by multiple converters in the DC equivalent system, including:

[0014] Screen out the target rectifier-side converters that match at least one converter type on the rectifier side from multiple converters in the DC equivalent system, and screen out the target inverter-side converters that match at least one converter type on the inverter side from multiple converters;

[0015] Control the switches between each target rectifier-side converter and each target inverter-side converter to conduct, and control the switches between other converters except the target rectifier-side converters and the target inverter-side converters to turn off, so as to obtain the target equivalent subsystem corresponding to the target DC power transmission topology.

[0016] In one embodiment, the multiple converters in the target equivalent subsystem include fixed converters and converters to be verified;

[0017] Conduct simulated back-to-back tests on each converter in the target equivalent subsystem to obtain multiple simulated electrical parameters, including:

[0018] Control the fixed converters in the target equivalent subsystem to conduct simulated back-to-back tests on the converters to be verified, and obtain multiple simulated electrical parameters of the converters to be verified under the test conditions.

[0019] In one embodiment, controlling the fixed converters in the target equivalent subsystem to conduct simulated back-to-back tests on the converters to be verified includes:

[0020] When the number of fixed converters is one, conduct simulated back-to-back tests on the converters to be verified in a two-terminal back-to-back manner through the fixed converter;

[0021] When the number of fixed converters is two, conduct simulated back-to-back tests on the converters to be verified in a three-terminal back-to-back manner through two mutually connected fixed converters in series; where, the two mutually connected fixed converters in series are two converters on the rectifier side or the inverter side.

[0022] In one embodiment, according to multiple simulated electrical parameters, determine the stability verification result of the target DC power transmission topology, including:

[0023] Determine the reliability verification result of the converters to be verified according to multiple simulated electrical parameters;

[0024] Based on the reliability verification result, obtain the stability verification result of the target DC power transmission topology.

[0025] In one embodiment, determining the reliability verification result of the converter to be verified according to multiple simulated electrical parameters includes:

[0026] Comparing the multiple simulated electrical parameters with a preset threshold range;

[0027] If all the multiple simulated electrical parameters are within the preset threshold range, it is determined that the reliability verification of the converter to be verified passes;

[0028] If any one of the simulated electrical parameters is not within the preset threshold range, it is determined that the reliability verification of the converter to be verified fails.

[0029] In one embodiment, the method further includes:

[0030] Inputting voltage disturbance signals of different levels to the target equivalent subsystem;

[0031] In the case of inputting voltage disturbance signals of each level, performing the step of simulating a back-to-back test on each converter in the target equivalent subsystem.

[0032] In a second aspect, the present application further provides a stability verification system, which includes a controller and a DC equivalent system. The DC equivalent system includes multiple converters, and the multiple converters are combined and connected through switches to build equivalent subsystems corresponding to different types of DC transmission topologies;

[0033] The controller is configured to obtain the type of the target DC transmission topology to be verified; according to the type of the target DC transmission topology, build a target equivalent subsystem corresponding to the target DC transmission topology through multiple converters in the DC equivalent system; perform a simulated back-to-back test on each converter in the target equivalent subsystem to obtain multiple simulated electrical parameters; and determine the stability verification result of the target DC transmission topology according to the multiple simulated electrical parameters.

[0034] In one embodiment, the multiple converters in the target equivalent subsystem include a fixed converter and a converter to be verified;

[0035] The controller is configured to control the switch between the fixed converters to conduct when the number of fixed converters is two.

[0036] In one embodiment, the multiple converters include at least one rectifier-side converter and at least one inverter-side converter;

[0037] Each converter in at least one rectifier-side converter is connected to each converter in at least one inverter-side converter through a first switch, and the converters in at least one rectifier-side converter are connected to each other through a second switch, and the converters in at least one inverter-side converter are connected to each other through a third switch.

[0038] In one embodiment, the DC equivalent system further includes a ripple suppression device, and each converter in at least one rectifier-side converter and each converter in at least one inverter-side converter are connected to the ripple suppression device through a first switch;

[0039] The ripple suppression device is used to suppress the ripple in the output rectified voltage of the rectifier-side converter.

[0040] In one embodiment, the DC equivalent system further includes a voltage disturbance device, and the voltage disturbance device is connected to the output end of the inverter-side converter;

[0041] The voltage disturbance device is used to introduce a voltage disturbance signal into the DC equivalent system;

[0042] The controller is used to verify the stability of the target equivalent subsystem when the inverter-side converter is under the interference of the voltage disturbance signal.

[0043] In one embodiment, the voltage disturbance device includes a voltage regulation device and a voltage regulation switch, and the voltage regulation device is connected to the inverter-side converter through the voltage regulation switch;

[0044] The voltage regulation device is used to adjust the amplitude and phase of the output voltage of the AC power supply;

[0045] The voltage regulation switch is used to adjust the magnitude of the adjusted AC voltage within a preset regulation range to form a voltage disturbance signal.

[0046] In one embodiment, the DC equivalent system further includes an AC filtering device, the AC filtering device is arranged on the AC bus, and the AC filtering device is respectively connected to the input end of the rectifier-side converter and the output end of the inverter-side converter;

[0047] The AC filtering device is used to filter out the harmonics generated during the test of the DC equivalent system.

[0048] In one embodiment, the AC filtering device includes at least two filters, and the at least two filters are respectively connected to the input end of the rectifier-side converter and the output end of the inverter-side converter;

[0049] The at least two filters are used to filter out harmonics with different frequencies in the DC equivalent system.

[0050] In one embodiment, the DC equivalent system further includes a voltage conversion device, and the voltage conversion device is respectively connected to the input end of the rectifier-side converter and the output end of the inverter-side converter;

[0051] A voltage conversion device is used to convert an AC voltage into a DC voltage and insulatively isolate the DC voltage from the AC voltage.

[0052] In one embodiment, the voltage conversion device includes a first commutation transformer and a second commutation transformer. The first commutation transformer is connected to the input end of the rectifier-side converter, and the second commutation transformer is connected to the output end of the inverter-side converter.

[0053] In a third aspect, the present application further provides a stability verification device, including:

[0054] An acquisition module for acquiring the type of the target DC power transmission topology to be verified;

[0055] A construction module for constructing a target equivalent subsystem corresponding to the target DC power transmission topology through multiple converters in a DC equivalent system according to the type of the target DC power transmission topology; the multiple converters in the DC equivalent system are combined and connected through switches to construct equivalent subsystems corresponding to different types of DC power transmission topologies;

[0056] A test module for performing a simulated back-to-back test on each converter in the target equivalent subsystem to obtain multiple simulated electrical parameters;

[0057] A determination module for determining the stability verification result of the target DC power transmission topology according to the multiple simulated electrical parameters.

[0058] In a fourth aspect, the present application further provides a controller, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the content of any one of the stability verification methods in the first aspect above.

[0059] In a fifth aspect, the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the content of any one of the stability verification methods in the first aspect above.

[0060] In a sixth aspect, the present application further provides a computer program product, including a computer program. When the computer program is executed by a processor, it implements the content of any one of the stability verification methods in the first aspect above.

[0061] The above stability verification method, system, device, controller, medium and program product obtain the type of the target DC transmission topology to be verified; according to the type of the target DC transmission topology, build a target equivalent subsystem corresponding to the target DC transmission topology through multiple converters in the DC equivalent system; the multiple converters in the DC equivalent system are combined and connected through switches for building equivalent subsystems corresponding to different types of DC transmission topologies; conduct simulated back-to-back tests on each converter in the target equivalent subsystem to obtain multiple simulated electrical parameters; determine the stability verification result of the target DC transmission topology according to the multiple simulated electrical parameters. The multiple converters in the DC equivalent system of this method can be arbitrarily combined and connected through switches to build equivalent subsystems corresponding to different types of DC transmission topologies. That is to say, multiple equivalent subsystems of different types can be built through one DC equivalent system. Then, through this one DC equivalent system, simulated back-to-back tests can be conducted on the multiple converters of multiple different types of target equivalent subsystems, reducing the complexity of the reliability verification methods for multiple DC transmission topologies, so that the stability verification of the equivalent systems of multiple DC transmission topologies can be carried out more simply. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings required for describing the embodiments of the present application or related technologies. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0063] Figure 1 It is an application environment diagram of the stability verification method in an embodiment;

[0064] Figure 2 It is a first process schematic diagram of the stability verification method in an embodiment;

[0065] Figure 3 It is a second process schematic diagram of the stability verification method in an embodiment;

[0066] Figure 4a It is a first schematic diagram of the two-terminal back-to-back test in an embodiment;

[0067] Figure 4b It is a second schematic diagram of the two-terminal back-to-back test in an embodiment;

[0068] Figure 4c It is a third schematic diagram of the two-terminal back-to-back test in an embodiment;

[0069] Figure 4d It is a schematic diagram of the three-terminal back-to-back test in an embodiment;

[0070] Figure 5 Schematic diagram of the third process of the stability verification method in an embodiment;

[0071] Figure 6 Schematic diagram of the fourth process of the stability verification method in an embodiment;

[0072] Figure 7 Schematic diagram of the fifth process of the stability verification method in an embodiment;

[0073] Figure 8 Schematic diagram of the sixth process of the stability verification method in an embodiment;

[0074] Figure 9 Schematic diagram of the stability verification system in an embodiment;

[0075] Figure 10 Schematic diagram of the structure of IGBT-MMC in an embodiment;

[0076] Figure 11 Schematic diagram of the structure of 12-pulse LCC in an embodiment;

[0077] Figure 12 Schematic diagram of the structure of a 12-pulse converter based on IGCT in an embodiment;

[0078] Figure 13 Schematic diagram of the structure of CSC based on IGCT in an embodiment;

[0079] Figure 14 Schematic diagram of the first of the DC equivalent system in an embodiment;

[0080] Figure 15 Schematic diagram of the second of the DC equivalent system in an embodiment;

[0081] Figure 16 Block diagram of the structure of the stability verification device in an embodiment.

[0082] Description of reference numerals:

[0083] 10: Controller; 11: DC equivalent system; 12: Multiple converters; 121: Rectifier-side converter; 122: Inverter-side converter; 13: Switch; 131: First switch; 132: Second switch; 133: Third switch; 14: Target equivalent subsystem; 15: Ripple suppression device; 151: Smoothing reactor; 16: Voltage disturbance device; 161: Voltage regulation device; 162: Voltage regulating switch; 17: AC filtering device; 171: Filter; 18: Voltage conversion device; 181: First commutation transformer; 182: Second commutation transformer. Detailed implementation manners

[0084] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0085] Before introducing the technical solutions of the present application in detail, the background technology of the present application will be briefly introduced.

[0086] For scenarios such as desert, Gobi and waste land new energy, and integrated water, wind and solar bases, etc., in the process of DC power transmission, it is necessary to comprehensively consider the grid constraints on the rectifier side and the inverter side, grid support in multiple application scenarios, high and low voltage ride-through, and commutation failure resistance, etc. The power transmission topologies in such scenarios include various different types of DC power transmission topologies.

[0087] In the related art, for various DC power transmission topologies, mainly the converters in each DC power transmission topology are respectively verified for reliability, and based on the verification results, the stability of each DC power transmission topology is determined.

[0088] In the process of verifying the reliability of the converter in any DC power transmission topology, usually the converter is directly subjected to a back-to-back test to determine the reliability of the converter. For example, for a conventional DC converter, a full-power 6-pulse back-to-back test circuit can be used for reliability verification. For a flexible DC converter, usually a 48-hour power back-to-back test is required before the technology is finalized. Since a flexible DC converter is composed of multiple sub-modules connected in cascade, all sub-modules need to be subjected to a 3-6 hour power back-to-back test. For a converter based on Integrated Gate Commutated Thyristor (IGCT), compared with a conventional DC converter and a flexible DC converter, the devices, device-level protection circuits, valve assembly structures, valve assembly working modes, control and protection strategies, etc. in the IGCT-based converter adopt new technologies and designs, and an equivalent system is urgently needed for back-to-back tests to verify the reliability of the IGCT-based converter.

[0089] In addition, through research and analysis, the converters for back-to-back tests in domestic valve factories are mostly of the same type. For example, line-commuted converters (LCCs) are tested against LCCs, and modular multilevel converters (MMCs) are tested against MMCs. The power back-to-back test of the converter mainly evaluates the current conduction ability. The operating power of LCCs and MMCs is relatively small. The current of the back-to-back device with an MMC does not exceed 3000 A, and the current of the back-to-back device with an LCC can reach 5000 A. However, the voltage of each device in the converter is relatively low, usually only a few hundred volts, which does not reach the actual operating voltage of the corresponding device level.

[0090] The existing back-to-back test device has insufficient assessment of the control function of the DC transmission topology and the transient stress of the valve components. The reliability verification is mainly carried out through low-voltage dynamic simulation experiments. However, the existing low-voltage dynamic simulation platform only supports the research of converter equipment with specific topologies, and its applicable range is limited. Due to the large differences in IGCTs and the lack of low-voltage and low-power IGCT devices for equivalent tests, the existing dynamic simulation platform cannot support the reliability verification process of new converters (such as converters based on IGCTs).

[0091] Based on the analysis of the statistical data of converter failure cases, it is not difficult to see that the failures caused by power devices account for more than 33%, which is the component with the highest failure rate in the converter. The IGCT device is the core component of the new converter and is first applied to the hybrid commutation converter (HCC). The reliability of the IGCT device directly affects the function of the HCC. In order to fully evaluate the long-term operating function of the IGCT device and the valve components, referring to the reliability test standard of power devices, a continuous operation test of not less than 1000 hours is required. Moreover, the voltage and current of the devices in the test device should refer to the voltage and current in the actual operation process.

[0092] In view of the above problems, the present application provides a stability verification method, system, device, controller, medium and program product. Multiple converters in a DC equivalent system can be arbitrarily combined and connected through switches to build equivalent subsystems corresponding to different types of DC transmission topologies. In this way, the operation conditions of multiple DC transmission topologies can be simulated through a single DC equivalent system, and the reliability of the converters of each DC transmission topology can be obtained, thereby determining the stability of each DC transmission topology. That is, the DC equivalent system has the ability to verify the stability of multiple DC transmission topologies. Multiple DC transmission topologies include multiple types of converters, such as LCC, MMC, and HCC. Considering HCC as a new type of converter, then, the stability verification method can perform reliability verification of the new converter under full voltage and full current. That is to say, the stability verification method provided by the present application can more simply perform reliability verification on different types of converters, and thus, based on the reliability verification results, the stability of multiple DC transmission topologies can be verified.

[0093] Of course, the technical solutions provided in the embodiments of the present application are not limited to only solving the above problems, and there are other technical effects. For specific details, please refer to the following embodiments. Next, the technical solutions of the present application will be introduced in detail.

[0094] The stability verification method provided in the embodiments of the present application can be applied to an Figure 1 application environment as shown. The controller in this application environment can be a server, a personal computer, a laptop computer, a smart phone, a tablet computer, a smart mobile phone, etc. The controller may include a processor, a memory, and a network interface connected through a system bus or wirelessly. Among them, the processor of the controller is used to provide computing and control capabilities. The memory of the controller may include a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the controller is used to store data during the stability verification process. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, it realizes a stability verification method.

[0095] In an exemplary embodiment, as Figure 2 shown, a stability verification method is provided. Taking the method applied to the Figure 1 controller in it as an example, it includes the following steps 201 to step 204. Among them:

[0096] S201, obtain the type of the target DC transmission topology to be verified.

[0097] Among them, the type of the target DC transmission topology can be a high-voltage DC transmission topology, a flexible DC transmission topology, etc.

[0098] In the embodiment of the present application, the controller can obtain the target DC transmission topology to be verified, and analyze the target DC transmission topology according to the classification rules of the DC transmission topology to determine the type of the target DC transmission topology. Alternatively, the corresponding type identifier can be carried in the target DC transmission topology in different ways. For example, it can be in the form of text, two-dimensional code, etc. The controller can identify the text or two-dimensional code of the target DC transmission topology to determine the type of the target DC transmission topology.

[0099] S202. According to the type of the target DC transmission topology, build a target equivalent subsystem corresponding to the target DC transmission topology through multiple converters in the DC equivalent system; the multiple converters in the DC equivalent system are combined and connected through switches, which are used to build equivalent subsystems corresponding to different types of DC transmission topologies.

[0100] Among them, the multiple converters in the DC equivalent system can include all converter types corresponding to different types of DC transmission topologies. For example, LCC, MMC, HCC, and current source converter (CSC), etc. Different types of converters can be combined into different types of DC transmission topologies. For example, when the converters on the rectifier side and the inverter side are both LCC, the built DC transmission topology is a high-voltage DC transmission topology; when the converters on the rectifier side and the inverter side are both MMC, the built DC transmission topology is a flexible DC transmission topology.

[0101] In the embodiment of the present application, there are switches between the multiple converters in the DC equivalent system, and each switch is connected to the controller. The controller realizes the conduction and cut-off between different converters by controlling the conduction and cut-off of the switches. The multiple converters in the conduction state can form a DC transmission topology. When it is necessary to verify the stability of the target DC transmission topology, the controller can determine the target converter corresponding to the target DC transmission topology according to the type of the target DC transmission topology. And select the target converter from the multiple converters in the DC equivalent system, control the switches between the target converters to conduct, and keep the switches between other converters in the cut-off state. In this way, the construction of the target equivalent subsystem corresponding to the target DC transmission topology can be completed.

[0102] S203. Conduct a simulated counter-rotation test on each converter in the target equivalent subsystem to obtain multiple simulated electrical parameters.

[0103] Among them, the simulated back-to-back test refers to the simulation process of the back-to-back test. The simulation process of the back-to-back test means placing two converters in the target equivalent subsystem back-to-back, where one converter simulates the power supply side and the other converter simulates the load side. By controlling signals and power flow, the converter on the load side is simulated to determine the actual operating conditions of the converter in the target DC transmission topology. The simulated electrical parameters refer to the relevant parameter information of the converter. For example, the relevant parameter information can be the highest operating voltage and the maximum conduction current of the converter.

[0104] In the embodiment of the present application, since the converters for the back-to-back test include a power supply side converter and a load side converter, the controller can divide multiple converters into multiple groups according to the back-to-back test requirements. For any group of converters, the controller can add test conditions in the target equivalent subsystem based on the test conditions of the back-to-back test. And output different control signals to simulate the group of converters to obtain multiple simulated electrical parameters of the converter on the load side of the group.

[0105] S204. Determine the stability verification result of the target DC transmission topology according to multiple simulated electrical parameters.

[0106] In the embodiment of the present application, since multiple simulated electrical parameters refer to the parameters of the converter, the controller can judge whether the actual operating conditions of the converter in the target DC transmission topology meet the operating conditions according to the multiple simulated electrical parameters of each converter. If the object of the simulated back-to-back test is only one converter and the actual operating conditions of the converter in the target DC transmission topology meet the operating conditions, it is determined that the stability verification of the target DC transmission topology passes; when the actual operating conditions of the converter in the target DC transmission topology do not meet the operating conditions, it is determined that the stability verification of the target DC transmission topology fails.

[0107] In the above stability verification method, the type of the target DC transmission topology to be verified is obtained; according to the type of the target DC transmission topology, a target equivalent subsystem corresponding to the target DC transmission topology is built through multiple converters in the DC equivalent system; the multiple converters in the DC equivalent system are combined and connected through switches, which is used to build equivalent subsystems corresponding to different types of DC transmission topologies; a simulated back-to-back test is performed on each converter in the target equivalent subsystem to obtain multiple simulated electrical parameters; according to the multiple simulated electrical parameters, the stability verification result of the target DC transmission topology is determined. The multiple converters in the DC equivalent system in this method can be arbitrarily combined and connected through switches to build equivalent subsystems corresponding to different types of DC transmission topologies. That is to say, multiple equivalent subsystems of different types can be built through one DC equivalent system. Then, through this one DC equivalent system, a simulated back-to-back test can be performed on the multiple converters of multiple different types of target equivalent subsystems, reducing the complexity of the reliability verification methods for multiple DC transmission topologies, so that the stability verification of the equivalent systems of multiple DC transmission topologies can be more simply performed.

[0108] Next, the specific content of obtaining the type of the target DC transmission topology to be verified is introduced above, and the specific content includes:

[0109] According to the topological structure of the target DC transmission topology to be verified, at least one converter type on the rectifier side and at least one converter type on the inverter side of the target DC transmission topology are determined.

[0110] In the embodiment of the present application, after determining that a certain DC transmission topology is the target DC transmission topology to be verified, the controller can obtain the topological structure of the target DC transmission topology. The topological structure includes the converters on the rectifier side, the converters on the inverter side, and smoothing reactors in the target DC transmission topology. Then, the controller can determine at least one converter type on the rectifier side and at least one converter type on the inverter side from the topological structure of the target DC transmission topology.

[0111] In the above stability verification method, according to the topological structure of the target DC transmission topology to be verified, at least one converter type on the rectifier side and at least one converter type on the inverter side of the target DC transmission topology are determined. The topological structure of the target DC transmission topology in this method includes each electrical device. Then, by analyzing the topological structure of the target DC transmission topology, at least one converter type on the rectifier side and at least one converter type on the inverter side can be accurately obtained from the topological structure.

[0112] In one embodiment, such as Figure 3As shown, the steps of building a target equivalent subsystem corresponding to the target DC transmission topology through multiple converters in the DC equivalent system according to the type of the target DC transmission topology are as follows:

[0113] S301, screen out the rectifier-side target converters that match at least one converter type on the rectifier side from multiple converters in the DC equivalent system, and screen out the inverter-side target converters that match at least one converter type on the inverter side from multiple converters.

[0114] In the embodiment of the present application, after obtaining at least one converter type on the rectifier side and at least one converter type on the inverter side in the target DC transmission topology, for the rectifier side, the controller can match at least one converter type on the rectifier side with the types of multiple converters in the DC equivalent system, and determine the rectifier-side target converters according to the matching result. For the inverter side, the controller can match at least one converter type on the inverter side with the types of multiple converters in the DC equivalent system, and determine the inverter-side target converters according to the matching result.

[0115] It should be noted that the rectifier-side target converters include at least one converter, and the inverter-side target converters also include at least one converter.

[0116] S302, control the switches between each rectifier-side target converter and each inverter-side target converter to conduct, and control the switches between other converters except the rectifier-side target converters and the inverter-side target converters to turn off, to obtain the target equivalent subsystem corresponding to the target DC transmission topology.

[0117] In the embodiment of the present application, there is a corresponding switch between each rectifier-side converter and each inverter-side converter in the DC equivalent system. Then, after determining the rectifier-side target converters and the inverter-side target converters, the controller can control the switches between each rectifier-side target converter and each inverter-side target converter to be in the on state. For other converters except the rectifier-side target converters and the inverter-side target converters, the controller can control the switches between other converters to turn off. In this way, the system composed of the converters that conduct with each other in the DC equivalent system is the target equivalent subsystem corresponding to the target DC transmission topology.

[0118] In the above stability verification method, a rectifier-side target converter that matches at least one converter type on the rectifier side is selected from multiple converters in the DC equivalent system, and an inverter-side target converter that matches at least one converter type on the inverter side is selected from multiple converters; the switches between each rectifier-side target converter and each inverter-side target converter are controlled to conduct, and the switches between other converters except the rectifier-side target converter and the inverter-side target converter are controlled to turn off, so as to obtain a target equivalent subsystem corresponding to the target DC transmission topology. According to at least one converter type on the rectifier side and at least one converter type on the inverter side, this method can accurately select the rectifier-side target converter and the inverter-side target converter from multiple converters in the DC equivalent system. By controlling the switches between the rectifier-side target converter and the inverter-side target converter to conduct, and controlling the switches between other converters to turn off, the target equivalent subsystem corresponding to the target DC transmission topology can be accurately built.

[0119] Assume that the multiple converters in the target equivalent subsystem include fixed converters and converters to be verified. Then, in one embodiment, the specific content of obtaining multiple simulated electrical parameters by performing a simulated back-to-back test on each converter in the target equivalent subsystem is as follows:

[0120] Control the fixed converter in the target equivalent subsystem to perform a simulated back-to-back test on the converter to be verified, and obtain multiple simulated electrical parameters of the converter to be verified under the test conditions.

[0121] Among them, the fixed converter can represent the converter on the side of the simulated power supply in the back-to-back test, and the converter to be verified represents the converter on the side of the simulated load in the back-to-back test. The fixed converter and the converter to be verified can be exchanged with each other in different simulated back-to-back tests. For example, if both the rectifier side and the inverter side in the HVDC transmission topology are LCCs, then when the rectifier-side LCC is the converter to be verified, the inverter-side LCC is the fixed converter; when the inverter-side LCC is the converter to be verified, the rectifier-side LCC is the fixed converter.

[0122] In the embodiment of the present application, for the simulated back-to-back test, after determining the fixed converter and the converter to be verified in the target equivalent subsystem, the controller can output different control signals to the fixed converter and the converter to be verified to perform the simulated back-to-back test. And during the simulated back-to-back test, multiple simulated electrical parameters of the converter to be verified under the test conditions are collected through sensors.

[0123] In the above stability verification method, the fixed converter in the control target equivalent subsystem performs a simulated back-to-back test on the converter to be verified, and multiple simulated electrical parameters of the converter to be verified under test conditions are obtained. During the simulated back-to-back test, multiple converters in the target equivalent subsystem are divided into a fixed converter and a converter to be verified, and the fixed converter in the target equivalent subsystem performs a simulated back-to-back test on the converter to be verified, so that multiple simulated electrical parameters under test conditions can be accurately obtained.

[0124] For the equivalent subsystems corresponding to different types of DC transmission topologies, the types and quantities of converters included therein are different. Then, under different equivalent subsystems, different types of simulated back-to-back tests can be selected to obtain the simulated electrical parameters of the converter to be verified. Next, a specific example is used to introduce the specific content of the fixed converter in the control target equivalent subsystem performing a simulated back-to-back test on the converter to be verified. The specific content includes:

[0125] When the number of fixed converters is one, the fixed converter performs a simulated back-to-back test on the converter to be verified in a two-terminal back-to-back manner; when the number of fixed converters is two, two mutually connected-in-series fixed converters perform a simulated back-to-back test on the converter to be verified in a three-terminal back-to-back manner; where, the two mutually connected-in-series fixed converters are two converters on the rectifier side or the inverter side.

[0126] In the embodiment of the present application, the simulated back-to-back test includes a two-terminal back-to-back method and a three-terminal back-to-back method. During the simulated back-to-back test, the controller can select the two-terminal back-to-back method or the three-terminal back-to-back method to perform a simulated back-to-back test on the converter to be verified based on the number of fixed converters in the target equivalent subsystem. For example, if the number of fixed converters is one, one fixed converter can be selected to complete the simulated back-to-back test in a two-terminal back-to-back manner; if the number of fixed converters is two, two fixed converters can be selected to complete the simulated back-to-back test in a three-terminal back-to-back manner. It should be noted that the two fixed converters can be two converters on the rectifier side, or two converters on the inverter side. Two fixed converters composed of one rectifier-side converter and one inverter-side converter cannot achieve a three-terminal back-to-back.

[0127] The back-to-back test includes a two-terminal back-to-back method and a three-terminal back-to-back method, where Figure 4a The first schematic diagram showing a two-terminal back-to-back test, A represents an LCC, B represents an HCC, and in the figure, the LCC and the HCC perform a two-terminal simulated back-to-back test. Figure 4b The second schematic diagram showing a two-terminal back-to-back test, C represents an MMC, and in the figure, the MMC and the HCC perform a two-terminal simulated back-to-back test. Figure 4c The third schematic diagram showing a two-terminal back-to-back test, and in the figure, the LCC and the MMC perform a two-terminal back-to-back test.Figure 4d Schematic diagram showing a three-terminal back-to-back test. The MMC is used for reactive power compensation. After the MMC and the LCC are connected in series, a three-terminal simulated back-to-back test is carried out with the HCC.

[0128] In the above stability verification method, when the number of converters is fixed at one, a simulated back-to-back test is carried out on the converter to be verified by fixing the converter in a two-terminal back-to-back manner; when the number of converters is fixed at two, a simulated back-to-back test is carried out on the converter to be verified by two fixed converters connected in series in a three-terminal back-to-back manner; among them, the two fixed converters connected in series are two converters on the rectifier side or the inverter side. This method can flexibly select the two-terminal back-to-back or three-terminal back-to-back method to carry out the simulated back-to-back test according to the number of fixed converters, making the reliability verification process of the converter to be verified more flexible.

[0129] The stability verification result of the target DC transmission topology mainly depends on the reliability verification result of the converter in the target equivalent subsystem. Therefore, in one embodiment, as Figure 5 shown, the specific content of determining the stability verification result of the target DC transmission topology according to multiple simulated electrical parameters includes the following steps:

[0130] S401, determine the reliability verification result of the converter to be verified according to multiple simulated electrical parameters.

[0131] In the embodiment of the present application, for any one simulated electrical parameter, the controller can compare the simulated electrical parameter with a preset threshold range. If the simulated electrical parameter is within the preset threshold range, it is determined that the simulated electrical parameter meets the preset conditions. When all simulated electrical parameters meet the preset conditions, it can be determined that the reliability verification of the converter to be verified passes. If any one simulated electrical parameter does not meet the preset conditions, it can be determined that the reliability verification result of the converter to be verified fails.

[0132] Alternatively, the controller can also calculate the proportion of simulated electrical parameters that meet the preset conditions. If the proportion is greater than or equal to a preset proportion threshold, it is determined that the reliability verification of the converter to be verified passes. If the proportion is less than the preset proportion threshold, it is determined that the reliability verification of the converter to be verified fails.

[0133] S402, based on the reliability verification result, obtain the stability verification result of the target DC transmission topology.

[0134] In an embodiment of the present application, after obtaining the reliability verification result of the converter to be verified, if the number of converters to be verified is one and the reliability verification of the converter to be verified passes, it is determined that the stability verification of the target DC transmission topology passes; if the reliability verification of the converter to be verified fails, it is determined that the stability verification of the target DC transmission topology fails.

[0135] If the number of converters to be verified is multiple and the reliability verifications of all the multiple converters to be verified pass, it is determined that the stability verification of the target DC transmission topology passes; if the reliability verification of any one of the multiple converters to be verified fails, it is determined that the stability verification of the target DC transmission topology fails.

[0136] In the above stability verification method, according to multiple simulated electrical parameters, the reliability verification result of the converter to be verified is determined; based on the reliability verification result, the stability verification result of the target DC transmission topology is obtained. Through multiple simulated electrical parameters, this method can accurately verify the reliability of the converter to be verified, and then accurately obtain the stability verification result of the target DC transmission topology based on the reliability verification result.

[0137] In one embodiment, as Figure 6 shown, the specific content of determining the reliability verification result of the converter to be verified according to multiple simulated electrical parameters includes:

[0138] S501, Compare multiple simulated electrical parameters with a preset threshold range.

[0139] Among them, the preset threshold range can be determined according to the actual operation situation, that is, the range without abnormalities during the actual operation process can be used as the preset threshold range. Alternatively, the preset threshold range can also be determined based on historical experience.

[0140] In an embodiment of the present application, for different simulated electrical parameters, the safe operating range is different. Therefore, the preset threshold range can include multiple threshold ranges corresponding to different simulated electrical parameters. Based on this, for any one simulated electrical parameter, the controller can compare the simulated electrical parameter with the preset threshold range to determine whether the simulated electrical parameter is within the preset threshold range.

[0141] S502, If all the multiple simulated electrical parameters are within the preset threshold range, it is determined that the reliability verification of the converter to be verified passes.

[0142] In an embodiment of the present application, after obtaining the comparison result, if the comparison result is that all the multiple simulated electrical parameters are within the preset threshold range, it is determined that the converter to be verified is within the safe range, that is, the reliability verification of the converter to be verified passes.

[0143] S503. If any one of the analog electrical parameters is not within the preset threshold range, it is determined that the reliability verification of the converter to be verified fails.

[0144] In the embodiment of the present application, after obtaining the comparison result, if the comparison result is that any one of the multiple analog electrical parameters is not within the preset threshold range, it is determined that the converter to be verified is not within the safe range, that is, the reliability verification of the converter to be verified fails.

[0145] In the above stability verification method, multiple analog electrical parameters are compared with the preset threshold range; if all the analog electrical parameters are within the preset threshold range, it is determined that the reliability verification of the converter to be verified passes; if any one of the analog electrical parameters is not within the preset threshold range, it is determined that the reliability verification of the converter to be verified fails. This method can accurately determine whether the reliability verification process of the converter to be verified passes by comparing the analog electrical parameters with the preset threshold range and based on the comparison result.

[0146] To ensure that the converter can still operate normally under various fault conditions, stability verification must be carried out under various conditions. Then, in one embodiment, as Figure 7 shown, the stability verification method further includes the following steps:

[0147] S601. Input voltage disturbance signals of different levels to the target equivalent subsystem.

[0148] Among them, the voltage disturbance signals of different levels represent fault signals of different severity levels. For example, the voltage disturbance signal can include three levels of disturbance, namely, the voltage disturbance signal of severe level, the voltage disturbance signal of normal level, and the voltage disturbance signal of mild level.

[0149] In the embodiment of the present application, the controller can output different control signals to the voltage disturbance device so that the voltage disturbance device can input voltage disturbance signals of different levels to the target equivalent subsystem. Or, the controller can also obtain voltage disturbance signals of different levels and input voltage disturbance signals of different levels to the target equivalent subsystem.

[0150] S602. Under the condition of inputting each level of voltage disturbance signal, execute the step of performing a simulated back-to-back test on each converter in the target equivalent subsystem.

[0151] In the embodiments of the present application, in order to more accurately verify the stability of the target equivalent subsystem, it is necessary to perform stability verification under the input of voltage disturbance signals at each level. Then, according to the stability verification results corresponding to the voltage disturbance signals at different levels, the stability verification result of the target DC transmission topology is determined. Then, for any level of voltage disturbance signal, the controller needs to perform a simulation drag test on each converter in the target equivalent subsystem to obtain a plurality of simulated electrical parameters. Then, according to the plurality of simulated electrical parameters, the stability verification result corresponding to the voltage disturbance signal at this level is determined.

[0152] In the above stability verification method, voltage disturbance signals at different levels are input to the target equivalent subsystem; in the case of input of voltage disturbance signals at each level, the step of performing a simulation drag test on each converter in the target equivalent subsystem is executed. By inputting voltage disturbance signals at different levels to the target equivalent subsystem and performing a simulation drag test on each converter in the target equivalent subsystem when inputting voltage disturbance signals at each level, in this way, the stability verification result corresponding to the voltage disturbance signal at this level can be accurately obtained, so that stability verification can be realized under various working conditions, and the accuracy of the stability verification result of the target DC transmission topology can be improved.

[0153] As a specific embodiment of the present application, as Figure 8 shown, the stability verification method includes:

[0154] S701, according to the topological structure of the target DC transmission topology to be verified, determine at least one converter type on the rectifier side and at least one converter type on the inverter side in the target DC transmission topology;

[0155] S702, screen out the rectifier-side target converters matching at least one converter type on the rectifier side from the multiple converters in the DC equivalent system, and screen out the inverter-side target converters matching at least one converter type on the inverter side from the multiple converters;

[0156] S703, control the switches between each rectifier-side target converter and each inverter-side target converter to be turned on, and control the switches between other converters except the rectifier-side target converter and the inverter-side target converter to be turned off, to obtain the target equivalent subsystem corresponding to the target DC transmission topology;

[0157] S704, control the fixed converter in the target equivalent subsystem to perform a simulation drag test on the converter to be verified, and obtain a plurality of simulated electrical parameters of the converter to be verified under the test conditions;

[0158] S705, compare the plurality of simulated electrical parameters with a preset threshold range;

[0159] S706, if multiple simulated electrical parameters are all within a preset threshold range, it is determined that the reliability verification of the converter to be verified passes;

[0160] S707, it is determined that the stability verification of the target DC transmission topology passes;

[0161] S708, if any one of the simulated electrical parameters is not within the preset threshold range, it is determined that the reliability verification of the converter to be verified fails;

[0162] S709, it is determined that the stability verification of the target DC transmission topology fails.

[0163] It should be understood that although each step in the flowcharts involved in the above embodiments is shown in sequence according to the indication of the arrows, these steps do not necessarily need to be executed in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps has no strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages. These steps or stages do not necessarily need to be executed at the same moment, but can be executed at different moments. The execution order of these steps or stages does not necessarily need to be sequential, but can be executed alternately or in turn with at least a part of other steps or steps or stages in other steps.

[0164] Based on the same inventive concept, an embodiment of the present application also provides a stability verification system for implementing the above-mentioned stability verification method. Next, the stability verification system will be introduced in detail.

[0165] In one embodiment, as Figure 9 shown, the above-mentioned stability verification system includes a controller 10 and a DC equivalent system 11. The DC equivalent system 11 includes multiple converters 12; the multiple converters 12 are combined and connected through switches 13 to build equivalent subsystems corresponding to different types of DC transmission topologies;

[0166] The controller 10 is used to obtain the type of the target DC transmission topology to be verified; according to the type of the target DC transmission topology, build a target equivalent subsystem 14 corresponding to the target DC transmission topology through the multiple converters 12 in the DC equivalent system 11; perform a simulated back-to-back test on each converter in the target equivalent subsystem 14 to obtain multiple simulated electrical parameters; and determine the stability verification result of the target DC transmission topology according to the multiple simulated electrical parameters.

[0167] In the embodiments of the present application, the multiple converters 12 in the DC equivalent system 11 include converter 1, converter 2... converter N. The types of the multiple converters 12 can be hybrid commutation converters, flexible DC converters, thyristor controlled converters, etc. The current of the multiple converters 12 needs to be less than a preset voltage threshold. For example, the preset voltage threshold can be 5000 amperes (A). Different types of converters can be combined into different types of DC transmission topologies. For example, when both the rectifier side and the inverter side are LCCs, the built DC transmission topology is a high-voltage DC transmission topology; when both the rectifier side and the inverter side are MMCs, the built DC transmission topology is a flexible DC transmission topology.

[0168] Figure 9 The target equivalent subsystem 14 therein includes converter 1 and converter 2, which is just an example. The target equivalent subsystem 14 can be composed of at least two converters among the multiple converters 12. Then, in one embodiment, the multiple converters in the target equivalent subsystem 14 include a fixed converter and a converter to be verified; a controller 10, configured to control the switch conduction between the fixed converters when the number of the fixed converters is two.

[0169] The number of the fixed converters in the target equivalent subsystem 14 is two, that is, the case of three-terminal back-to-back. Referring to Figure 4d the schematic diagram of the three-terminal back-to-back test in, then, these two fixed converters are two converters on the rectifier side or the inverter side. In this case, the controller 10 needs to control the switch conduction between the two fixed converters to meet the requirements of the three-terminal back-to-back test.

[0170] Figure 10 is the structural schematic diagram of an IGBT-MMC. An Insulate-Gate Bipolar Transistor (IGBT)-MMC includes six bridge arms, and the six bridge arms are used to realize the conversion between AC and DC. Each bridge arm is composed of a plurality of modular multilevel converter sub-modules in cascade. It can be seen from the figure that each bridge arm includes n multilevel converter sub-modules, namely SM1, SM2... SMn, and the n multilevel converter sub-modules are all composed in a cascaded manner. In the figure, U d represents the DC side voltage of the IGBT-MMC.

[0171] Figure 11 represents the structural schematic diagram of a 12-pulse LCC. The 12-pulse LCC is composed of two 6-pulse LCCs connected in series, with a 30° phase difference between them. A 6-pulse LCC is composed of 6 bridge arms, and each bridge arm includes a plurality of thyristors connected in series. In the figure, U d represents the DC side voltage of the 12-pulse LCC.

[0172] Figure 12 Figure 1 is a schematic structural diagram of an IGCT-based HCC. The IGCT-based HCC is a 12-pulse converter. The 12-pulse HCC is composed of two 6-pulse HCCs connected in series, with a 30° phase difference between them. A 6-pulse HCC is composed of 6 bridge arms, and each bridge arm includes multiple IGCTs connected in series. In the figure, U d represents the DC-side voltage of the IGCT-based HCC.

[0173] Figure 13 Figure 2 is a schematic structural diagram of an IGCT-based CSC. The topological structure of the CSC converter is as shown in the figure. The converter includes 6 bridge arms, and each bridge arm is composed of several IGCTs connected in series. The AC side of the CSC is an L-C low-pass filter, which can effectively filter out the high-order current harmonics generated by the converter. In the figure, U d represents the DC-side voltage of the CSC.

[0174] The controller 10 can be, but is not limited to, a microcontroller unit (MCU), a central processing unit (CPU), a digital signal processor (DSP), a field programmable gate array (FPGA), a single-chip microcomputer, or other control devices.

[0175] The above stability verification system includes a controller 10 and a DC equivalent system 11. The DC equivalent system 11 includes multiple converters 12. The multiple converters 12 are combined and connected through switches 13 to build equivalent subsystems corresponding to different types of DC transmission topologies. The controller 10 is used to obtain the type of the target DC transmission topology to be verified; according to the type of the target DC transmission topology, build a target equivalent subsystem 14 corresponding to the target DC transmission topology through the multiple converters 12 in the DC equivalent system 11; conduct a simulated back-to-back test on each converter in the target equivalent subsystem 14 to obtain multiple simulated electrical parameters; and determine the stability verification result of the target DC transmission topology according to the multiple simulated electrical parameters. The multiple converters 12 in the DC equivalent system 11 can be arbitrarily combined and connected through switches 13 to build equivalent subsystems corresponding to different types of DC transmission topologies. That is to say, multiple different types of equivalent subsystems can be built through one DC equivalent system 11. Then, through this one DC equivalent system 11, simulated back-to-back tests can be conducted on the multiple converters of multiple different types of target equivalent subsystems, reducing the complexity of the reliability verification methods for multiple DC transmission topologies, and thus the stability of the equivalent systems of multiple DC transmission topologies can be verified more simply.

[0176] In one embodiment, Figure 14 is the first schematic diagram of the DC equivalent system. The multiple converters 12 include at least one rectifier-side converter 121 and at least one inverter-side converter 122;

[0177] Each converter in at least one rectifier-side converter 121 is connected to each converter in at least one inverter-side converter 122 through a first switch 131, and the converters in at least one rectifier-side converter 121 are connected through a second switch 132, and the converters in at least one inverter-side converter 122 are connected through a third switch 133.

[0178] Among them, the rectifier side in the DC transmission topology mainly utilizes the conduction characteristics of semiconductor devices (such as diodes and thyristors) to perform peak clipping and rectification on the input alternating current, and outputs direct current of a certain level. The main function of the rectifier-side converter is to convert the electrical energy in the power supply into direct current electrical energy for use by DC loads. The inverter side mainly utilizes the switching actions of semiconductor switching devices to perform segmented opening and closing on the direct current, and converts the direct current into alternating current of a certain frequency, amplitude, and phase.

[0179] In the embodiments of the present application, the multiple converters 12 can be divided into at least one rectifier-side converter 121 and at least one inverter-side converter 122. Refer to Figure 14 , at least one rectifier-side converter 121 includes two converters, and at least one inverter-side converter 122 also includes two converters. During the construction of the target equivalent subsystem 14, by connecting some of the converters on the rectifier side to some of the converters on the inverter side through switches, the target equivalent subsystem 14 can be constructed.

[0180] It can be understood that at least one rectifier-side converter 121 is responsible for AC rectification. If the rectifier-side converter is a 6-pulse converter, then the 6-pulse converter can be composed of 6 converters in a 3-phase full-bridge connection mode, and each converter is alternately triggered at the same interval to convert the alternating current into direct current. Any one of the at least one inverter-side converters 122 can also be composed of 6 converters in a 3-phase full-bridge connection mode, responsible for inverting the direct current into alternating current and connecting it to the power supply system. At least one inverter-side converter 122 and at least one rectifier-side converter 121 form a loop to reduce the capacity requirement of the DC equivalent system 11. It should be noted that the converter to be verified can be used as both the rectifier side and the inverter side, and can be flexibly adjusted according to the test requirements.

[0181] The above-mentioned multiple converters 12 include at least one rectifier-side converter 121 and at least one inverter-side converter 122; each converter in at least one rectifier-side converter 121 is connected to each converter in at least one inverter-side converter 122 through a first switch 131, and the converters in at least one rectifier-side converter 121 are connected through a second switch 132, and the converters in at least one inverter-side converter 122 are connected through a third switch 133. By dividing the multiple converters into the rectifier side and the inverter side, the functions of each converter can be clarified, and different switches are set in the converters on the rectifier side and the inverter side. During the subsequent construction of the equivalent subsystem, by controlling the conduction and cutoff of different switches, the construction of the target equivalent subsystem 14 can be accurately completed.

[0182] In order to suppress the ripple in the output DC voltage of the rectifier-side converter 121, a ripple suppression device 15 is introduced into the DC equivalent system 11. Next, a detailed introduction to the ripple suppression device 15 will be given through an embodiment. Please continue to refer to Figure 14 As shown, the DC equivalent system 11 further includes a ripple suppression device 15, and each converter in at least one rectifier-side converter 121 and each converter in at least one inverter-side converter 122 are connected to the ripple suppression device 15 through a first switch 131;

[0183] The ripple suppression device 15 is used to suppress the ripple in the output rectified voltage of the rectifier-side converter 121.

[0184] In the embodiment of the present application, since the number of pulses of the rectifier-side converter 121 is limited, the output DC voltage of the rectifier-side converter 121 always carries ripple, which needs to be suppressed by the ripple suppression device 15. Among them, the ripple suppression device 15 may include a storage inductor, a filter capacitor, a smoothing reactor, and the like.

[0185] Taking the ripple suppression device 15 as a smoothing reactor 151 as an example, in one embodiment, please continue to refer to Figure 14 As shown, the ripple suppression device 15 includes a smoothing reactor 151, and the smoothing reactor 151 is connected in series between the DC output terminals of each converter in at least one rectifier-side converter 121 and at least one inverter-side converter 122 and the DC line.

[0186] Among them, the smoothing reactor 151 is a device used to filter DC harmonics in a DC power transmission topology. The smoothing reactor 151 is composed of elements such as inductors and capacitors, and the attenuation and filtering of specific frequency harmonics are achieved by adjusting the parameters of the inductor and capacitor.

[0187] In the embodiments of the present application, smoothing reactors 151 are installed in the converters of the DC transmission topology, making the output DC current close to the ideal DC current. The smoothing reactor 151 is generally connected in series between the DC output terminal of each converter and the DC line. It can smooth the ripple in the DC current, avoid the discontinuity of the current during low DC power transmission, and reduce the probability of commutation failure by limiting the rate of change of the current caused by rapid voltage changes. The selection of the smoothing reactor 151 mainly considers the rate of rise of the fault current, and its inductance value can be calculated from the rated DC voltage of the target equivalent subsystem 14.

[0188] It should be noted that the number of converters in the rectifier-side converter 121 and the inverter-side converter 122 is one or more, and the number of smoothing reactors 151 is one. All the converters on the rectifier side are connected to the input terminal of the smoothing reactor 151, and all the converters on the inverter side are connected to the output terminal of the smoothing reactor 151.

[0189] The above-mentioned DC equivalent system 11 further includes a ripple suppression device 15. Each converter in at least one rectifier-side converter 121 and each converter in at least one inverter-side converter 122 are connected to the ripple suppression device 15 through a first switch 131. The ripple suppression device 15 is used to suppress the ripple in the output rectified voltage of the rectifier-side converter 121. The ripple suppression device 15 includes a smoothing reactor 151, and the smoothing reactor 151 is connected in series between the DC output terminal of each converter in at least one rectifier-side converter 121 and at least one inverter-side converter 122 and the DC line. By introducing the smoothing reactor 151 between at least one rectifier-side converter 121 and at least one inverter-side converter 122, the ripple in the output rectified voltage of the rectifier-side converter 121 can be suppressed through the smoothing reactor 151, making the environment of the simulated back-to-back test closer to the environment of the actual target DC transmission topology.

[0190] To ensure that the converter can still operate normally under various fault conditions, stability verification must be carried out under various conditions. Therefore, a voltage disturbance device 16 can be connected in series in the DC equivalent system 11 to simulate fault conditions and verify the stability of the DC equivalent system 11. Then, in one embodiment, continue to refer to Figure 14 As shown, the DC equivalent system 11 further includes a voltage disturbance device 16, and the voltage disturbance device 16 is connected to the output terminal of the inverter-side converter 122;

[0191] The voltage disturbance device 16 is used to introduce a voltage disturbance signal into the DC equivalent system 11;

[0192] A controller 10 is used to verify the stability of the target equivalent subsystem 14 when the inverter-side converter 122 is under the interference of a voltage disturbance signal.

[0193] Among them, the voltage disturbance device 16 is used to simulate various fault conditions to verify the ability of the converter and the DC transmission topology to resist commutation failure. Commutation failure is a common fault, which is caused by various faults. For example, converter short circuit, loss of trigger pulse, AC system fault on the inverter side, etc. will all cause commutation failure.

[0194] In the embodiment of the present application, after the voltage disturbance device 16 is connected to the DC equivalent system 11 and generates a voltage disturbance signal, the inverter-side converter 122 will generate a fault response to the voltage disturbance signal. The controller 10 can compare the fault response with a preset fault response, and determine whether the fault response action and the protection strategy pass the verification according to the comparison result.

[0195] In one embodiment, the voltage disturbance device 16 includes a voltage regulation device 161 and a voltage regulating switch 162. The voltage regulation device 161 is connected to the inverter-side converter 122 through the voltage regulating switch 162;

[0196] The voltage regulation device 161 is used to adjust the amplitude and phase of the output voltage of the AC power supply;

[0197] The voltage regulating switch 162 is used to adjust the magnitude of the adjusted AC voltage within a preset adjustment range to form a voltage disturbance signal.

[0198] The voltage disturbance device 16 is composed of a voltage regulation device 161 based on fully controlled devices and a wide-range voltage regulating switch 162. The voltage regulation device 161 based on fully controlled devices is used to rectify the power frequency periodic AC power supply, and then invert the DC into power frequency periodic AC through the inverter-side converter. Cooperating with the voltage regulating switch 162 to achieve 10% - 100% adjustment of the output voltage, so that the magnitude of the voltage disturbance signal can be adjusted flexibly. Among them, the voltage regulation device 161 can be composed of one or more current conversion devices, commutation transformers, filters, and main switches. The voltage regulating switch 162 can include types such as a pressure controller, a no-load voltage regulating switch of a transformer, or a voltage regulator, etc.

[0199] The above-mentioned DC equivalent system 11 further includes a voltage disturbance device 16, which is connected to the output end of the inverter-side converter 122; the voltage disturbance device 16 is used to introduce a voltage disturbance signal into the DC equivalent system 11; the controller 10 is used to verify the fault response actions and protection strategies of the inverter-side converter 122 under voltage disturbance interference. The voltage disturbance device 16 includes a voltage regulation device 161 and a voltage regulating switch 162, and the voltage regulation device 161 is connected to the inverter-side converter 122 through the voltage regulating switch 162; the voltage regulation device 161 is used to adjust the amplitude and phase of the output voltage of the AC power supply; the voltage regulating switch 162 is used to adjust the magnitude of the adjusted AC voltage within a preset adjustment range to form a voltage disturbance signal. By introducing the voltage disturbance device 16 with the voltage regulating switch 162 into the DC equivalent system 11, different magnitudes of disturbances can be introduced during the simulation of the equivalent system. In this way, the DC equivalent system 11 can simulate the operation conditions of multiple DC transmission topologies under different disturbances, making the simulation process of the DC equivalent system 11 closer to the actual process, and thus making the stability verification result of the DC equivalent system 11 more accurate.

[0200] Harmonics are likely to be generated during the test process of the DC equivalent system 11. In order to avoid adverse effects on AC power transmission and at the same time compensate for the reactive power consumed by the DC transmission topology, an AC filtering device 17 needs to be introduced during the simulation process of the DC equivalent system 11. Next, an embodiment is used to introduce the AC filtering device 17. Please continue to refer to Figure 14 As shown, the DC equivalent system 11 further includes an AC filtering device 17, which is arranged on the AC bus, and the AC filtering device 17 is respectively connected to the input end of the rectifier-side converter 121 and the output end of the inverter-side converter 122;

[0201] The AC filtering device 17 is used to filter out the harmonics generated during the test process of the DC equivalent system 11.

[0202] In the embodiment of the present application, the AC filtering device 17 is arranged between the AC power supply and the input end of the rectifier-side converter 121, and between the input power supply and the output end of the inverter-side converter 122.

[0203] In one embodiment, the AC filtering device 17 includes at least two filters 171, and the at least two filters 171 are respectively connected to the input end of the rectifier-side converter 121 and the output end of the inverter-side converter 122;

[0204] The at least two filters 171 are used to filter out harmonics with different frequencies in the DC equivalent system 11.

[0205] In the embodiments of the present application, each filter 171 can be composed of capacitors, reactances, and resistors connected in series and parallel. Different types of converters correspond to harmonics of different frequencies. In order to achieve the purpose of filtering harmonics, multiple filters 171 can be set to filter different-frequency harmonics respectively. During the process of setting the filter 171, it can be set based on the type of the converter. For example, the DC equivalent system 11 includes a 6-pulse converter, a 12-pulse converter, and a 24-pulse converter, and 3 filters can be set to filter different-frequency harmonics respectively. Among them, for the 6-pulse converter, the frequency of the harmonics can be the characteristic harmonics of 6K±1 times or 6K times. For the 12-pulse converter, the frequency of the harmonics can be the commutation sub-harmonics of 12K times. For the 24-pulse converter, the frequency of the harmonics can be the commutation sub-harmonics of 24K times.

[0206] The AC filter can be a ceramic chip capacitor, a metal foil capacitor, or an organic electrolytic capacitor, etc. Different types of AC filters have differences in aspects such as filtering effect, operating temperature range, and voltage withstand capacity. When selecting, it is necessary to select according to the types of multiple converters 12 in the DC equivalent system 11.

[0207] The above-mentioned DC equivalent system 11 further includes an AC filtering device 17. The AC filtering device 17 is arranged on the AC bus, and the AC filtering device 17 is respectively connected to the input end of the rectifier-side converter 121 and the output end of the inverter-side converter 122; the AC filtering device 17 is used to filter the harmonics generated during the test process of the DC equivalent system 11. The AC filtering device 17 includes at least two filters 171, and the at least two filters 171 are respectively connected to the input end of the rectifier-side converter 121 and the output end of the inverter-side converter 122; the at least two filters 171 are used to filter different-frequency harmonics in the DC equivalent system 11. By setting multiple filters 171 between the AC voltage and the converter, it is possible to filter the harmonics of each component and avoid the influence of harmonics on the test process of the DC equivalent system 11.

[0208] A voltage conversion device 18 also needs to be set between the multiple filters 171 and the input end of the rectifier-side converter 121 and the output end of the inverter-side converter 122 to convert the AC voltage into the commutation voltage required by the converter, so as to insulate and isolate the DC part and the AC part from each other, so as to avoid the mutual influence between the grounding of the neutral point of the AC part and the grounding of the neutral point of the DC part, making the commutation process impossible to proceed. Then, in one embodiment, continue to refer to Figure 14 As shown, the DC equivalent system 11 further includes a voltage conversion device 18, and the voltage conversion device 18 is respectively connected to the input end of the rectifier-side converter 121 and the output end of the inverter-side converter 122;

[0209] A voltage conversion device 18 is used to convert an AC voltage into a DC voltage and insulate and isolate the DC voltage from the AC voltage.

[0210] In an embodiment of the present application, the voltage conversion device 18 is mainly used for the mutual conversion between the AC voltage and the DC voltage, so that the DC power transmission system can complete the power transmission process with the DC voltage.

[0211] In one embodiment, the voltage conversion device 18 includes a first commutation transformer 181 and a second commutation transformer 182. The first commutation transformer 181 is connected to the input end of the rectifier-side converter 121, and the second commutation transformer 182 is connected to the output end of the inverter-side converter 122.

[0212] In an embodiment of the present application, the first commutation transformer 181 is used to connect the AC power supply to the rectifier-side converter 121 and convert the input AC voltage into a DC voltage. The second commutation transformer 182 is used to connect the AC power supply to the inverter-side converter 122 and convert the DC voltage output by the inverter-side converter 122 into an AC voltage.

[0213] It can be understood that different connection methods of the transformer windings can also be used to provide two sets of three-phase symmetric commutation voltages with equal amplitudes and a phase difference of 30° for the series-connected rectifier-side converter 121 and inverter-side converter 122 to achieve twelve-pulse commutation. At the same time, the leakage reactance of the converter can play a role in limiting the fault current and buffer and suppress the lightning impulse overvoltage wave invading the converter station along the AC line.

[0214] The above DC equivalent system 11 further includes a voltage conversion device 18. The voltage conversion device 18 is respectively connected to the input end of the rectifier-side converter 121 and the output end of the inverter-side converter 122. The voltage conversion device 18 is used to convert an AC voltage into a DC voltage and insulate and isolate the DC voltage from the AC voltage. The voltage conversion device 18 includes a first commutation transformer 181 and a second commutation transformer 182. The first commutation transformer 181 is connected to the input end of the rectifier-side converter 121, and the second commutation transformer 182 is connected to the output end of the inverter-side converter 122. By connecting commutation transformers between the AC power supply and the input end of the rectifier-side converter 121 and between the input power supply and the output end of the inverter-side converter 122 respectively, the conversion between the AC and DC voltages is realized.

[0215] Figure 15It is the second schematic diagram of the DC equivalent system. The DC equivalent system 11 includes a rectifier-side converter 121 and an inverter-side converter 122. The input end of the rectifier-side converter 121 is connected to the first commutation transformer 181, and the output end of the inverter-side converter 122 is connected to the second commutation transformer 182. The rectifier-side converter 121, the inverter-side converter 122 and the smoothing reactor 151 are connected by a switch 13. The input power supply in the figure represents the input of AC voltage. The AC filtering device 17 includes three filters: 6th-order filtering, 12th-order filtering and 24th-order filtering. And a voltage disturbance device 16 is also introduced in the DC equivalent system 11 to make the simulation process of the DC equivalent system 11 closer to the actual operation process, so that the stability verification result of the DC equivalent system 11 is more accurate.

[0216] Based on the same inventive concept, an embodiment of the present application also provides a stability verification device for implementing the stability verification method involved above. The solution provided by this device to solve the problem is similar to the solution described in the above method. Therefore, the specific limitations in one or more embodiments of the stability verification device provided below can refer to the limitations on the stability verification method in the above text, and will not be repeated here.

[0217] In an exemplary embodiment, as Figure 16 shown, a stability verification device is provided, including: an acquisition module 21, a construction module 22, a test module 23 and a determination module 24, where:

[0218] The acquisition module 21 is configured to acquire the type of the target DC transmission topology to be verified;

[0219] The construction module 22 is configured to construct a target equivalent subsystem corresponding to the target DC transmission topology through multiple converters in the DC equivalent system; the multiple converters in the DC equivalent system are combined and connected through switches to construct equivalent subsystems corresponding to different types of DC transmission topologies;

[0220] The test module 23 is configured to test each converter in the target equivalent subsystem to obtain multiple simulated electrical parameters;

[0221] The determination module 24 is configured to determine the stability verification result of the target DC transmission topology according to the multiple simulated electrical parameters.

[0222] In an embodiment, the above acquisition module includes a type determination unit, where:

[0223] The type determination unit is configured to determine at least one converter type on the rectifier side and at least one converter type on the inverter side in the target DC transmission topology according to the topological structure of the target DC transmission topology to be verified.

[0224] In one embodiment, the above-mentioned building module includes: a screening unit and a control unit, where:

[0225] The screening unit is used to screen out the rectifier-side target converters that match at least one converter type on the rectifier side from multiple converters in the DC equivalent system, and screen out the inverter-side target converters that match at least one converter type on the inverter side from multiple converters;

[0226] The control unit is used to control the switch conduction between each rectifier-side target converter and each inverter-side target converter, and control the switch off between other converters except the rectifier-side target converter and the inverter-side target converter, so as to obtain the target equivalent subsystem corresponding to the target DC transmission topology.

[0227] In one embodiment, the above-mentioned test module includes an acquisition unit, where:

[0228] The acquisition unit is used to control the fixed converter in the target equivalent subsystem to conduct a simulated back-to-back test on the converter to be verified, and acquire multiple simulated electrical parameters of the converter to be verified under test conditions.

[0229] In one embodiment, the above-mentioned acquisition unit is further used to conduct a simulated back-to-back test on the converter to be verified in a two-terminal back-to-back manner by the fixed converter when the number of fixed converters is one; when the number of fixed converters is two, conduct a simulated back-to-back test on the converter to be verified in a three-terminal back-to-back manner by two fixed converters connected in series; where the two fixed converters connected in series are two converters on the rectifier side or the inverter side.

[0230] In one embodiment, the above-mentioned determination module includes: a result determination unit and a result acquisition unit, where:

[0231] The result determination unit is used to determine the reliability verification result of the converter to be verified according to multiple simulated electrical parameters;

[0232] The result acquisition unit is used to obtain the stability verification result of the target DC transmission topology based on the reliability verification result.

[0233] In one embodiment, the above-mentioned result determination unit is further used to compare multiple simulated electrical parameters with a preset threshold range; if multiple simulated electrical parameters are all within the preset threshold range, it is determined that the reliability verification of the converter to be verified passes; if any one of the simulated electrical parameters is not within the preset threshold range, it is determined that the reliability verification of the converter to be verified fails.

[0234] In one embodiment, the above-mentioned stability verification device further includes: an input module and an execution module, where:

[0235] An input module for inputting voltage disturbance signals of different levels to a target equivalent subsystem;

[0236] An execution module for performing steps of simulating a counter-rotating test on each converter in the target equivalent subsystem when a voltage disturbance signal of each level is input.

[0237] Each module in the above stability verification device can be implemented in whole or in part by software, hardware, and their combination. Each of the above modules can be embedded in the processor of a computer device in hardware form or be independent of it, or can be stored in the memory of a computer device in software form so that the processor can call and execute the operations corresponding to each of the above modules.

[0238] In an exemplary embodiment, a controller is provided, including a memory and a processor. A computer program is stored in the memory, and when the processor executes the computer program, the content of any one of the above stability verification methods is implemented.

[0239] In an embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the content of any one of the above stability verification methods is implemented.

[0240] In an embodiment, a computer program product is provided, including a computer program. When the computer program is executed by a processor, the content of any one of the above stability verification methods is implemented.

[0241] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use, and processing of relevant data need to comply with relevant regulations.

[0242] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The databases involved in the embodiments provided in this application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., without limitation. The processors involved in the embodiments provided in this application can be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, data processing logics based on quantum computing, artificial intelligence (AI) processors, etc., without limitation.

[0243] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope recorded in this application.

[0244] The above embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

Claims

1. A stability verification method, characterized in that: The method comprises: Obtain the type of target DC transmission topology to be verified; According to the type of the target DC transmission topology, a target equivalent subsystem corresponding to the target DC transmission topology is built through multiple converters in the DC equivalent system; multiple converters in the DC equivalent system are combined and connected through switches to build equivalent subsystems corresponding to different types of DC transmission topologies; Inputting voltage disturbance signals of different levels into the target equivalent subsystem; When a voltage disturbance signal of each level is input, a simulated pair-drag test is performed on each converter in the target equivalent subsystem to obtain a plurality of simulated electrical parameters; According to the multiple simulated electrical parameters corresponding to the voltage disturbance signal of each level, a stability verification result of the target direct current transmission topology is determined.

2. The method according to claim 1, characterized in that The obtaining the type of the target DC transmission topology to be verified includes: According to the topological structure of the target DC power transmission topology to be verified, at least one converter type on the rectifier side and at least one converter type on the inverter side in the target DC power transmission topology are determined.

3. The method according to claim 2, characterized in that The method of building a target equivalent subsystem corresponding to the target DC transmission topology by using a plurality of converters in a DC equivalent system according to the type of the target DC transmission topology includes: Screening out a rectifier-side target converter that matches the type of at least one converter on the rectifier side from a plurality of converters in the DC equivalent system, and screening out an inverter-side target converter that matches the type of at least one converter on the inverter side from the plurality of converters; The switches between each of the rectifier-side target converters and each of the inverter-side target converters are controlled to be turned on, and the switches between other converters except the rectifier-side target converter and the inverter-side target converter are controlled to be turned off, so as to obtain a target equivalent subsystem corresponding to the target DC transmission topology.

4. The method according to any one of claims 1 to 3, characterized in that: The multiple converters in the target equivalent subsystem include fixed converters and converters to be verified; The simulated pair-drag test is performed on each converter in the target equivalent subsystem to obtain multiple simulated electrical parameters, including: The fixed converter in the target equivalent subsystem is controlled to perform a simulated towing test on the converter to be verified, and a plurality of simulated electrical parameters of the converter to be verified under the test conditions are obtained.

5. The method according to claim 4, characterized in that The controlling the fixed converter in the target equivalent subsystem to perform a simulated towing test on the converter to be verified includes: In the case where the number of the fixed converter is one, a simulated towing test is performed on the converter to be verified in a two-end towing manner by the fixed converter; When the number of the fixed converters is two, a simulated pair-drag test is performed on the converter to be verified in a three-terminal pair-drag manner by two fixed converters connected in series; wherein the two fixed converters connected in series are two converters on the rectifier side or the inverter side.

6. The method according to claim 4, characterized in that Determining the stability verification result of the target DC power transmission topology according to the multiple simulated electrical parameters corresponding to the voltage disturbance signal of each level includes: Determining a reliability verification result of the converter to be verified according to a plurality of simulated electrical parameters corresponding to each level of the voltage disturbance signal; Based on the reliability verification result, a stability verification result of the target direct current transmission topology is obtained.

7. The method according to claim 6, characterized in that The step of determining the reliability verification result of the converter to be verified according to the plurality of simulated electrical parameters corresponding to each level of the voltage disturbance signal comprises: Comparing the plurality of analog electrical parameters corresponding to each level of the voltage disturbance signal with a preset threshold range; If the multiple simulated electrical parameters corresponding to the voltage disturbance signal of each level are all within the preset threshold range, it is determined that the reliability verification of the converter to be verified has passed; If any simulated electrical parameter corresponding to any level of the voltage disturbance signal is not within the preset threshold range, it is determined that the reliability verification of the converter to be verified has failed.

8. A stability verification system, characterized in that: The stability verification system includes a controller and a DC equivalent system, wherein the DC equivalent system includes a plurality of converters, wherein the plurality of converters are combined and connected through switches to build equivalent subsystems corresponding to different types of DC transmission topologies; The controller is used to obtain the type of the target DC transmission topology to be verified; according to the type of the target DC transmission topology, build a target equivalent subsystem corresponding to the target DC transmission topology through multiple converters in the DC equivalent system; input different levels of voltage disturbance signals to the target equivalent subsystem; when each level of voltage disturbance signal is input, perform a simulated pair-drag test on each converter in the target equivalent subsystem to obtain multiple simulated electrical parameters; and determine the stability verification result of the target DC transmission topology according to the multiple simulated electrical parameters corresponding to each level of voltage disturbance signal.

9. The system according to claim 8, characterized in that The multiple converters in the target equivalent subsystem include fixed converters and converters to be verified; The controller is used to control the conduction of switches between the fixed converters when the number of the fixed converters is two.

10. The system according to claim 8, characterized in that The plurality of converters include at least one rectifier-side converter and at least one inverter-side converter; Each converter in the at least one rectifier-side converter is connected to each converter in the at least one inverter-side converter via a first switch, and the converters in the at least one rectifier-side converter are connected to each other via a second switch, and the converters in the at least one inverter-side converter are connected to each other via a third switch.

11. The system according to claim 10, characterized in that The DC equivalent system further includes a ripple suppression device, and each of the at least one rectifier-side converter and each of the at least one inverter-side converter are connected to the ripple suppression device via a first switch; The ripple suppression device is used to suppress the ripple in the output rectified voltage of the rectifier-side converter.

12. The system according to claim 8, characterized in that The DC equivalent system further includes a voltage disturbance device, which is connected to the output end of the inverter-side converter; The voltage disturbance device is used to introduce a voltage disturbance signal into the DC equivalent system; The controller is used to verify the stability of the target equivalent subsystem when the inverter-side converter is disturbed by a voltage disturbance signal.

13. The system according to claim 12, characterized in that The voltage disturbance device comprises a voltage regulating device and a voltage regulating switch, wherein the voltage regulating device is connected to the inverter-side converter via the voltage regulating switch; The voltage regulating device is used to adjust the amplitude and phase of the output voltage of the AC power supply; The voltage regulating switch is used to adjust the magnitude of the adjusted AC voltage within a preset regulating range to form the voltage disturbance signal.

14. The system according to claim 8, characterized in that The DC equivalent system further includes an AC filter device, which is arranged on the AC bus and is respectively connected to the input end of the rectifier-side converter and the output end of the inverter-side converter; The AC filtering device is used to filter out harmonics generated by the DC equivalent system during the test process.

15. The system according to claim 14, characterized in that The AC filter device comprises at least two filters, and the at least two filters are respectively connected to the input end of the rectifier-side converter and the output end of the inverter-side converter; The at least two filters are used to filter out harmonics of different frequencies in the DC equivalent system.

16. The system according to claim 8, characterized in that The DC equivalent system further includes a voltage conversion device, which is respectively connected to the input end of the rectifier-side converter and the output end of the inverter-side converter; The voltage conversion device is used to convert AC voltage into DC voltage and to insulate and isolate the DC voltage from the AC voltage.

17. The system according to claim 16, characterized in that The voltage conversion device includes a first converter transformer and a second converter transformer, the first converter transformer is connected to the input end of the rectifier-side converter, and the second converter transformer is connected to the output end of the inverter-side converter.

18. A stability verification device, characterized in that: The device comprises: An acquisition module, used for acquiring the type of target DC transmission topology to be verified; A building module, used to build a target equivalent subsystem corresponding to the target DC transmission topology through multiple converters in a DC equivalent system according to the type of the target DC transmission topology; multiple converters in the DC equivalent system are combined and connected through switches to build equivalent subsystems corresponding to different types of DC transmission topologies; A test module is used to input voltage disturbance signals of different levels to the target equivalent subsystem; when each level of voltage disturbance signal is input, a simulated pair-drag test is performed on each converter in the target equivalent subsystem to obtain a plurality of simulated electrical parameters; The determination module is used to determine the stability verification result of the target direct current transmission topology according to the multiple simulated electrical parameters corresponding to the voltage disturbance signal of each level.

19. A controller comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

20. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

21. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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