Flexible DC short-circuit current suppression strategy starting threshold value setting method and system

Abstract

The invention discloses a flexible direct current short circuit current suppression strategy starting threshold value setting method and a flexible direct current short circuit current suppression strategy starting threshold value setting system, and belongs to the technical field of power system planning. According to the setting method, system operation stability and economical efficiency are considered in the power grid planning stage, and a threshold value capable of providing reasonable technical requirements for flexible direct current is determined. According to the setting method, the short-circuit current level of a system bus and the residual voltage of a flexible direct current conversion bus serve as judgment conditions, technical requirements are provided for flexible direct current short-circuit current suppression measures in the planning and design stage, reference can be provided for flexible direct current control protection configuration parameters, effective coordination and matching of flexible direct current fault supporting capacity and short-circuit control are achieved, and the reliability of the system is improved. And the economical efficiency and the safety of overall operation of the system are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power system planning, and particularly relates to a flexible direct short-circuit current suppression strategy starting threshold value setting method and system. BACKGROUND

[0002] With the large-scale construction of new energy bases and the increasing demand for long-distance power transmission, flexible direct current transmission technology is widely used in new power systems due to its good controllability and flexibility. The flexible direct current system based on modular multilevel converter (MMC) has the technical advantages of high output voltage waveform quality and no commutation failure, and becomes one of the main options for new direct current. However, the double-ended controlled structure composed of power electronic devices in the flexible direct current system fundamentally changes the fault mechanism, and the transient characteristics of the flexible direct current short-circuit current are highly dependent on the response process of the converter station control system, making it difficult for the flexible direct current short-circuit current suppression measures to meet the actual engineering needs.

[0003] At present, various flexible direct current system short-circuit current calculation methods have been proposed. Some studies establish an RLC series equivalent model, construct the full network differential state equation, and solve the short-circuit current by using numerical calculation method, but such method cannot accurately reflect the dynamic response process of the converter station control system. Some scholars also propose to parallel a current source in the equivalent model to consider the influence of the controller, which improves the calculation accuracy to some extent, but the model structure is still idealized and has limited applicability.

[0004] Therefore, it is necessary to provide a new flexible direct current short-circuit current suppression strategy starting threshold value setting method and system to solve the above technical problems. SUMMARY

[0005] The purpose of the present disclosure is to provide a flexible direct current short-circuit current suppression strategy starting threshold value setting method and system to solve the above problems.

[0006] The present disclosure achieves the above-mentioned purpose by the following technical solutions: A flexible direct current short-circuit current suppression strategy starting threshold value setting method, comprising the following steps: Based on the short-circuit capacity invariance principle, according to the short-circuit current feeding standard of the 500kV voltage grade flexible direct current converter station, the short-circuit current contribution value of each voltage grade is determined through the short-circuit current conversion formula; Based on the short-circuit current contribution value of each voltage grade, different voltage grade short-circuit current control intervals are divided; The short-circuit current level of each voltage grade bus is calculated; Based on the short-circuit current level of each voltage grade bus, the different voltage grade short-circuit current control intervals are matched and the starting threshold value is determined.

[0007] As a further optimization of this disclosure, based on the principle of constant short-circuit capacity and according to the short-circuit current feed-in standard of 500kV voltage level flexible DC converter stations, the contribution value of flexible DC short-circuit current at each voltage level is determined through the short-circuit current conversion formula, including: Based on the principle of constant short-circuit capacity, and according to the short-circuit current feed-in standard of 500kV voltage level flexible DC converter stations, the contribution value of flexible DC short-circuit current to each voltage level grid under the conditions of short-circuit current suppression strategy activation and non-activation is calculated using the short-circuit current conversion formula.

[0008] As a further optimization of this disclosure, based on the contribution value of the flexible DC short-circuit current at each voltage level, the short-circuit current control intervals for different voltage levels are divided, including: For each voltage level, based on the breaking capacity of the circuit breaker at the corresponding voltage level and the determined contribution value of the flexible DC short-circuit current at each voltage level, short-circuit current control interval one, short-circuit current control interval two, and short-circuit current control interval three are set. Wherein, the first short-circuit current control interval is the critical value where the short-circuit current is below which the suppression strategy does not need to be activated; the second short-circuit current control interval is the critical value where the short-circuit current is above which the suppression strategy alone cannot control it within the circuit breaker's breaking capacity; and the third short-circuit current control interval is the interval between the first and second short-circuit current control intervals where the suppression strategy needs to be activated.

[0009] As a further optimization of this disclosure, the bus short-circuit current level for each voltage level is calculated, including: Based on the PSD-SCCP short-circuit current calculation program, select and load the ".DAT" and ".SWI" data files in PSD format used for short-circuit current calculation, calculate the near-zone short-circuit current level of the flexible DC converter station, and obtain the calculation results of the bus short-circuit current level for each voltage level.

[0010] As a further optimization of this disclosure, based on the bus short-circuit current levels of each voltage level, the short-circuit current control ranges of different voltage levels are matched and the start-up threshold value is determined, including: If the bus short-circuit current level falls within the first short-circuit current control range, then there is no need to impose short-circuit current suppression technology requirements on flexible DC. If the bus short-circuit current level belongs to the second short-circuit current control range, then the flexible DC-DC transmission system scheme is adjusted without relying on the flexible DC-DC short-circuit current suppression strategy. If the bus short-circuit current level belongs to the third short-circuit current control interval, based on the PSD-SWNT time-domain simulation program, load the ".SWI" data file, perform metallic short-circuit fault simulation on all buses in the third short-circuit current control interval, record the residual voltage value of the flexible DC converter bus corresponding to each fault, select the maximum residual voltage value and reserve a preset margin as the start threshold value of the flexible DC short-circuit current suppression strategy.

[0011] As a further optimization of this disclosure, when conducting simulation of metallic short-circuit faults, the receiving end of the flexible direct transmission adopts a constant AC voltage control mode and performs quasi-stability calculations under full-power mode.

[0012] As a further optimization of this disclosure, if the voltage of the flexible DC converter bus is detected to be lower than the start-up threshold, a short-circuit current suppression strategy is activated.

[0013] A system for setting a startup threshold value for a flexible DC short-circuit current suppression strategy includes: The current contribution value calculation module is used to determine the short-circuit current contribution value of flexible DC converter stations at each voltage level based on the principle of constant short-circuit capacity and the short-circuit current feed-in standard of 500kV voltage level flexible DC converter stations, through the short-circuit current conversion formula. The control interval division module is used to divide the short-circuit current control intervals for different voltage levels based on the contribution value of the flexible DC short-circuit current at each voltage level. The current level calculation module is used to calculate the bus short-circuit current level for each voltage level. The threshold value determination module is used to match the short-circuit current control range of different voltage levels and determine the start-up threshold value based on the short-circuit current level of the bus at each voltage level.

[0014] As a further optimization of this disclosure, the current contribution value calculation module is based on the principle of constant short-circuit capacity. According to the short-circuit current feed-in standard of 500kV voltage level flexible DC converter stations, it determines the short-circuit current contribution value of flexible DC converters at each voltage level through a short-circuit current conversion formula, including: Based on the principle of constant short-circuit capacity, and according to the short-circuit current feed-in standard of 500kV voltage level flexible DC converter stations, the contribution value of flexible DC short-circuit current to each voltage level grid under the conditions of short-circuit current suppression strategy activation and non-activation is calculated using the short-circuit current conversion formula.

[0015] As a further optimization of this disclosure, the control interval division module divides the short-circuit current control intervals for different voltage levels based on the contribution values ​​of the flexible DC short-circuit current at each voltage level, including: For each voltage level, based on the breaking capacity of the circuit breaker at the corresponding voltage level and the determined contribution value of the flexible DC short-circuit current at each voltage level, short-circuit current control interval one, short-circuit current control interval two, and short-circuit current control interval three are set. Wherein, the first short-circuit current control interval is the critical value where the short-circuit current is below which the suppression strategy does not need to be activated; the second short-circuit current control interval is the critical value where the short-circuit current is above which the suppression strategy alone cannot control it within the circuit breaker's breaking capacity; and the third short-circuit current control interval is the interval between the first and second short-circuit current control intervals where the suppression strategy needs to be activated.

[0016] As a further optimization of this disclosure, the current level calculation module calculates the bus short-circuit current level for each voltage level, including: Based on the PSD-SCCP short-circuit current calculation program, select and load the ".DAT" and ".SWI" data files in PSD format used for short-circuit current calculation, calculate the near-zone short-circuit current level of the flexible DC converter station, and obtain the calculation results of the bus short-circuit current level for each voltage level.

[0017] As a further optimization of this disclosure, the threshold value determination module determines the start-up threshold value based on the short-circuit current level of each voltage level bus, matching the short-circuit current control range of different voltage levels, including: If the bus short-circuit current level falls within the first short-circuit current control range, then there is no need to impose short-circuit current suppression technology requirements on flexible DC. If the bus short-circuit current level belongs to the second short-circuit current control range, then the flexible DC-DC transmission system scheme is adjusted without relying on the flexible DC-DC short-circuit current suppression strategy. If the bus short-circuit current level belongs to the third short-circuit current control interval, based on the PSD-SWNT time-domain simulation program, load the ".SWI" data file, perform metallic short-circuit fault simulation on all buses in the third short-circuit current control interval, record the residual voltage value of the flexible DC converter bus corresponding to each fault, select the maximum residual voltage value and reserve a preset margin as the start threshold value of the flexible DC short-circuit current suppression strategy.

[0018] As a further optimization of this disclosure, when conducting simulation of metallic short-circuit faults, the receiving end of the flexible direct transmission adopts a constant AC voltage control mode and performs quasi-stability calculations under full-power mode.

[0019] As a further optimization of this disclosure, if the voltage of the flexible DC converter bus is detected to be lower than the start-up threshold, a short-circuit current suppression strategy is activated.

[0020] An electronic device includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; The processor is used to execute the program stored in the memory to implement the method for setting the start threshold value of the flexible DC short-circuit current suppression strategy.

[0021] A computer-readable storage medium storing a computer program, which, when executed by a processor, implements the method for setting the start-up threshold value of the flexible DC short-circuit current suppression strategy.

[0022] The beneficial effects of this disclosure are as follows: This disclosure innovatively links the bus short-circuit level with the flexible DC control characteristics, establishing a quantitative relationship between the control strategy and electrical parameters; This disclosure addresses the scenario of large-scale new energy transmission via flexible DC. During the power grid planning phase, it considers both system operational stability and economic efficiency, establishing a threshold value that allows for reasonable technical requirements to be set for flexible DC. It uses the system bus short-circuit current level and the residual voltage of the flexible DC converter bus as judgment conditions, proposing technical requirements for flexible DC short-circuit current suppression measures during the planning and design phase. This provides a reference for flexible DC control and protection configuration parameters, achieving effective coordination and matching between flexible DC fault support capability and short-circuit control, thereby improving the overall economic efficiency and safety of the system operation. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart of a method in an embodiment of this disclosure; Figure 2 This is a system structure block diagram of an embodiment of this disclosure; Figure 3 This is a block diagram of the device structure in an embodiment of this disclosure. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] like Figure 1 As shown, a method for setting the start-up threshold value of a flexible DC short-circuit current suppression strategy includes the following steps: S1. Based on the principle of constant short-circuit capacity, and according to the short-circuit current feed-in standard of 500kV flexible DC converter stations, the contribution value of flexible DC short-circuit current at each voltage level is determined through the short-circuit current conversion formula, specifically including: According to the "Reply on Short-Circuit Current Feedback in UHVDC Transmission Line Projects" provided by the DC Technology Consulting Center of the State Grid Economic Research Institute, when the converter station's short-circuit current suppression strategy is not activated, the short-circuit current fed into the AC system at each end shall not exceed 6kA. When the short-circuit current suppression strategy is activated, the short-circuit current fed into the AC system at each end shall not exceed 2kA.

[0027] Since the short-circuit capacity remains constant, the contribution value of the short-circuit current to the power grid at each voltage level can be calculated using the short-circuit current conversion formula, which is as follows: (1) In the formula, For short-circuit capacity, Bus voltage This is the short-circuit current.

[0028] set up For each voltage level, the bus voltage is specified. The short-circuit current fed into the AC system from each terminal when the short-circuit current suppression strategy is not activated; The short-circuit current fed into the AC system from each terminal when the short-circuit current suppression strategy is activated.

[0029] (2) S1.1 Determine the contribution value of the short-circuit current of the flexible direct-connected 220kV power grid: For a 220kV power grid, when the converter station's short-circuit current suppression strategy is not activated, the short-circuit current fed into the AC system from each terminal shall not exceed: (3) When the short-circuit current suppression strategy is activated, the short-circuit current fed into the AC system from each terminal shall not exceed: (4) S1.2 Determine the contribution value of short-circuit current when the flexible direct-connected 1000kV power grid is: Since the short-circuit capacity remains constant, for a 1000kV power grid, when the converter station's short-circuit current suppression strategy is not activated, the short-circuit current fed into the AC system from each end shall not exceed: (5) When the short-circuit current suppression strategy is activated, the short-circuit current fed into the AC system from each terminal shall not exceed: (6) S2. Based on the short-circuit current contribution values ​​of each voltage level, divide the short-circuit current control intervals for different voltage levels, specifically including: S2.1 sets the short-circuit current control range for a 500kV voltage level: According to the "Reply from the DC Technology Consulting Center of State Grid Economic Research Institute regarding the short-circuit current feed into UHVDC transmission line projects", when the short-circuit current suppression strategy is activated, the short-circuit current fed into the AC system at each end shall not exceed 2kA; when the short-circuit current suppression strategy of the converter station is not activated, the short-circuit current fed into the AC system at each end shall not exceed 6kA.

[0030] When both ends of the flexible direct current are connected to the power grid and the short-circuit current suppression strategy is not activated, the short-circuit current fed into the AC system by the flexible direct current at both ends does not exceed To ensure that the short-circuit current does not exceed the circuit breaker's breaking capacity of 63kA, a lower limit for short-circuit current control "interval three" is set. for: (7) When the short-circuit current suppression strategy is activated, the short-circuit current fed into the AC system at both ends of the flexible DC circuit does not exceed kA, to ensure that the short-circuit current does not exceed the circuit breaker's breaking capacity, an upper limit for short-circuit current control "interval three" is set. for: (8) As shown in equation (7), when the two flexible direct currents are connected to the power grid and the short-circuit current suppression strategy is not activated, the short-circuit current fed into the AC system by the two flexible direct currents does not exceed 12kA. In order to ensure that the short-circuit current does not exceed the circuit breaker's breaking capacity of 63kA, the lower limit of the short-circuit current control "interval three" is set as follows: (9) As can be seen from equation (8), when the short-circuit current suppression strategy is activated, the short-circuit current fed into the AC system at both ends of the flexible DC system does not exceed 4kA. In order to ensure that the short-circuit current does not exceed the breaking capacity of the circuit breaker, the upper limit of the short-circuit current control "interval three" is set as follows: (10) For the 500kV bus short-circuit current control range: "Range 1" is less than 51kA, "Range 2" is greater than 59kA, and "Range 3" is 51~59kA.

[0031] S2.2 Set the short-circuit current control range for the 220kV voltage level: According to the aforementioned method for determining the contribution of flexible DC short-circuit current, it can be seen from equation (7) that when both flexible DC terminals are connected to the 220kV power grid and the short-circuit current suppression strategy is not activated, the short-circuit current fed into the AC system by the flexible DC terminals does not exceed 27.2kA. In order to ensure that the short-circuit current does not exceed the circuit breaker breaking capacity of 50kA, the lower limit of the short-circuit current control "interval three" is set as follows: (11) As shown in equation (8), when the short-circuit current suppression strategy is activated, the short-circuit current fed into the AC system at both ends of the flexible DC line does not exceed 9kA. In order to ensure that the short-circuit current does not exceed the breaking capacity of the circuit breaker, the upper limit of the short-circuit current control "interval three" is set as follows: (12) For the 220kV bus short-circuit current control range: "Range 1" is less than 22.8kA, "Range 2" is greater than 41kA, and "Range 3" is 22.8~41kA.

[0032] S2.3 sets the short-circuit current control range for a 1000kV voltage level: According to the aforementioned method for determining the contribution of flexible DC short-circuit current, it can be seen from equation (7) that when both flexible DC terminals are connected to a 1000kV power grid and the short-circuit current suppression strategy is not activated, the short-circuit current fed into the AC system by the flexible DC terminals does not exceed 6kA. In order to ensure that the short-circuit current does not exceed the circuit breaker breaking capacity of 63kA, the lower limit of the short-circuit current control "interval three" is set as follows: (13) As shown in equation (8), when the short-circuit current suppression strategy is activated, the short-circuit current fed into the AC system by the two flexible DC terminals does not exceed 2kA. In order to ensure that the short-circuit current does not exceed the breaking capacity of the circuit breaker, the upper limit of the short-circuit current control "interval three" is set as follows: (14) For the 1000kV bus short-circuit current control range: "Range 1" is less than 57kA, "Range 2" is greater than 61kA, and "Range 3" is 57~61kA.

[0033] S3. Calculate the short-circuit current level of the busbars at each voltage level, specifically including: Based on the PSD-SCCP short-circuit current calculation program, select and load the ".DAT" and ".SWI" data files in PSD format used for short-circuit current calculation, calculate the short-circuit current level in the near zone of the flexible DC converter station, and obtain the short-circuit current calculation results of all AC buses in the system, so as to prepare data for step 4 to determine the short-circuit current control interval.

[0034] S4. Based on the bus short-circuit current levels of each voltage level, match the short-circuit current control ranges of different voltage levels and determine the start-up threshold value, specifically including: S4.1 defines the technical requirements for suppressing flexible DC short-circuit current in "Interval 1": When the short-circuit current levels of all buses in the system are within the range of "Interval 1", that is, "the short-circuit current level of the 500kV bus is less than 51kA, the short-circuit current level of the 220kV bus is less than 22.8kA, and the short-circuit current level of the 1000kV bus is less than 57kA", even if the flexible DC short-circuit current suppression strategy is not activated, the short-circuit current levels of each bus in the system after taking into account the contribution of the flexible DC short-circuit current will not exceed the breaking capacity of the circuit breaker (63kA for 1000kV / 500kV and 50kA for 220kV), and there is no need to impose short-circuit current suppression technical requirements on the flexible DC.

[0035] S4.2 defines the technical requirements for suppressing flexible DC short-circuit current in "Interval Two": When the short-circuit current level of the busbars in the system is within the range of "Interval Two", that is, "the short-circuit current level of the 500kV busbar is greater than 59kA, the short-circuit current level of the 220kV busbar is greater than 41kA, and the short-circuit current level of the 1000kV busbar is greater than 61kA", even if the flexible DC short-circuit current suppression strategy is activated, the short-circuit current level of each busbar in the system will still exceed the breaking capacity of the circuit breaker by limiting the contribution of the short-circuit current injected by the flexible DC. At this time, it is not possible to put forward short-circuit current suppression technical requirements for the flexible DC, and the flexible DC system input scheme needs to be adjusted.

[0036] S4.3 Determine the threshold value for the "Interval Three" flexible DC short-circuit current suppression measures: When the short-circuit current level of the busbars in the system is within the range of "Interval Three", namely "the short-circuit current level of 500kV busbar is 51~59kA, the short-circuit current level of 220kV busbar is 22.8~41kA, and the short-circuit current level of 1000kV busbar is 57~61kA", short-circuit current suppression technology requirements need to be put forward for flexible DC. By setting the activation threshold value of the flexible DC short-circuit current suppression strategy, it is ensured that the short-circuit current of each busbar in the system does not exceed the breaking capacity of the circuit breaker.

[0037] (1) Boundary conditions The flexible direct transmission receiving end adopts a constant AC voltage control mode and performs quasi-stability calculations under full-start mode.

[0038] (2) Simulation calculation For all bus sets within the system whose short-circuit current levels are within the range of "Interval Three" Based on the PSD-SWNT time-domain simulation program, the ".SWI" data file in PSD format for short-circuit current calculation was selected and loaded. Metallic short-circuit fault calculations are performed on each busbar, and the residual voltage value of the flexible DC converter bus corresponding to each short-circuit fault is recorded. Through residual pressure value It can calculate the short-circuit current boosted by the flexible DC converter bus to the short-circuit fault point under various short-circuit fault conditions. As shown in the following formula: (15) Where XM is the equivalent impedance between the short-circuit fault point and the flexible DC converter bus.

[0039] This allows the formation of a corresponding busbar set. Set of residual voltage values ​​for flexible DC converter bus This is used to further determine the start-up threshold value of the flexible DC short-circuit current suppression strategy.

[0040] (3) Set the start-up threshold value for the flexible DC short-circuit current suppression strategy. The set of residual voltage values ​​for the flexible DC converter bus generated by the above calculations. The maximum residual voltage value is selected, and a residual voltage margin of 0.02 pu is considered as the starting threshold value for the flexible DC short-circuit current suppression strategy. .

[0041] (16) This value can provide a reference for the configuration parameters of flexible DC control and protection during the planning stage. In actual power grid operation, if the system detects that the voltage of the flexible DC converter bus is lower than the start-up threshold value... This involves initiating a short-circuit current suppression strategy to achieve effective coordination and matching between flexible DC fault support capability and short-circuit control.

[0042] like Figure 2 As shown, embodiments of this disclosure provide a system for setting a startup threshold value for a flexible DC short-circuit current suppression strategy, including: The current contribution value calculation module is used to determine the short-circuit current contribution value of flexible DC converter stations at each voltage level based on the principle of constant short-circuit capacity and the short-circuit current feed-in standard of 500kV voltage level flexible DC converter stations, through the short-circuit current conversion formula. The control interval division module is used to divide the short-circuit current control intervals for different voltage levels based on the contribution value of the flexible DC short-circuit current at each voltage level. The current level calculation module is used to calculate the bus short-circuit current level for each voltage level. The threshold value determination module is used to match the short-circuit current control range of different voltage levels and determine the start-up threshold value based on the short-circuit current level of the bus at each voltage level.

[0043] The implementation process of the functions and roles of each module in the above system is detailed in the implementation process of the corresponding steps in the above method, and will not be repeated here.

[0044] For the system embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The system embodiments described above are merely illustrative. The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this disclosure according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0045] See Figure 3 The electronic device provided in the embodiments of this disclosure includes a processor 1110, a communication interface 1120, a memory 1130 and a communication bus 1140, wherein the processor 1110, the communication interface 1120 and the memory 1130 communicate with each other through the communication bus 1140. Memory 1130 is used to store computer programs; When the processor 1110 executes the program stored in the memory 1130, it implements the above-mentioned method for setting the start threshold value of the flexible DC short-circuit current suppression strategy. The aforementioned communication bus 1140 can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus 1140 can be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, it is represented by only one thick line in the figure, but this does not indicate that there is only one bus or one type of bus.

[0046] The communication interface 1120 is used for communication between the above-mentioned electronic device and other devices.

[0047] The memory 1130 may include random access memory (RAM) or non-volatile memory, such as at least one disk storage device. Optionally, the memory 1130 may also be at least one storage device located remotely from the aforementioned processor 1110.

[0048] Embodiments of this disclosure also provide a computer-readable storage medium. The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method for setting the start-up threshold value of the flexible DC short-circuit current suppression strategy as described above.

[0049] The embodiments described above are merely examples of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these modifications and improvements all fall within the protection scope of this disclosure.

Claims

1. A method for setting the start-up threshold value of a flexible DC short-circuit current suppression strategy, characterized in that, Includes the following steps: Based on the principle of constant short-circuit capacity, and according to the short-circuit current feed-in standard of 500kV voltage level flexible DC converter station, the contribution value of flexible DC short-circuit current at each voltage level is determined by the short-circuit current conversion formula. Based on the short-circuit current contribution values ​​of each voltage level, the short-circuit current control intervals for different voltage levels are divided. Calculate the bus short-circuit current level for each voltage level; Based on the bus short-circuit current levels of each voltage level, the short-circuit current control ranges of different voltage levels are matched and the start-up threshold value is determined.

2. The method for setting the start-up threshold value of a flexible DC short-circuit current suppression strategy according to claim 1, characterized in that, Based on the principle of constant short-circuit capacity, and according to the short-circuit current feed-in standard of 500kV flexible DC converter stations, the contribution value of flexible DC short-circuit current at each voltage level is determined through the short-circuit current conversion formula, including: Based on the principle of constant short-circuit capacity, and according to the short-circuit current feed-in standard of 500kV voltage level flexible DC converter stations, the contribution value of flexible DC short-circuit current to each voltage level grid under the conditions of short-circuit current suppression strategy activation and non-activation is calculated using the short-circuit current conversion formula.

3. The method for setting the start-up threshold value of a flexible DC short-circuit current suppression strategy according to claim 1, characterized in that, Based on the short-circuit current contribution values ​​of each voltage level, short-circuit current control intervals for different voltage levels are divided, including: For each voltage level, based on the breaking capacity of the circuit breaker at the corresponding voltage level and the determined contribution value of the flexible DC short-circuit current at each voltage level, short-circuit current control interval one, short-circuit current control interval two, and short-circuit current control interval three are set. Wherein, the first short-circuit current control interval is the critical value where the short-circuit current is below which the suppression strategy does not need to be activated; the second short-circuit current control interval is the critical value where the short-circuit current is above which the suppression strategy alone cannot control it within the circuit breaker's breaking capacity; and the third short-circuit current control interval is the interval between the first and second short-circuit current control intervals where the suppression strategy needs to be activated.

4. The method for setting the start-up threshold value of a flexible DC short-circuit current suppression strategy according to claim 1, characterized in that, Calculate the bus short-circuit current level for each voltage level, including: Based on the PSD-SCCP short-circuit current calculation program, select and load the ".DAT" and ".SWI" data files in PSD format for short-circuit current calculation, calculate the near-zone short-circuit current level of the flexible DC converter station, and obtain the calculation results of the bus short-circuit current level for each voltage level.

5. The method for setting the start-up threshold value of a flexible DC short-circuit current suppression strategy according to claim 3, characterized in that, Based on the bus short-circuit current levels of each voltage level, the short-circuit current control ranges for different voltage levels are matched and the start-up threshold value is determined, including: If the bus short-circuit current level falls within the first short-circuit current control range, then there is no need to impose short-circuit current suppression technology requirements on flexible DC. If the bus short-circuit current level belongs to the second short-circuit current control range, then the flexible DC-DC transmission system scheme is adjusted without relying on the flexible DC-DC short-circuit current suppression strategy. If the bus short-circuit current level belongs to the third short-circuit current control interval, based on the PSD-SWNT time-domain simulation program, load the ".SWI" data file, perform metallic short-circuit fault simulation on all buses in the third short-circuit current control interval, record the residual voltage value of the flexible DC converter bus corresponding to each fault, select the maximum residual voltage value and reserve a preset margin as the start-up threshold value of the flexible DC short-circuit current suppression strategy.

6. The method for setting the start-up threshold value of a flexible DC short-circuit current suppression strategy according to claim 5, characterized in that, When conducting simulations of metallic short-circuit faults, the receiving end of the flexible direct transmission uses a constant AC voltage control mode, and metastability calculations are performed under full-start conditions.

7. The method for setting the start-up threshold value of a flexible DC short-circuit current suppression strategy according to claim 5, characterized in that, If the voltage of the flexible DC converter bus is detected to be lower than the start-up threshold, the short-circuit current suppression strategy will be activated.

8. A system for setting a start-up threshold value for a flexible DC short-circuit current suppression strategy, characterized in that, include: The current contribution value calculation module is used to determine the short-circuit current contribution value of flexible DC converter stations at each voltage level based on the principle of constant short-circuit capacity and the short-circuit current feed-in standard of 500kV voltage level flexible DC converter stations, through the short-circuit current conversion formula. The control interval division module is used to divide the short-circuit current control intervals for different voltage levels based on the contribution value of the flexible DC short-circuit current at each voltage level. The current level calculation module is used to calculate the bus short-circuit current level for each voltage level. The threshold value determination module is used to match the short-circuit current control range of different voltage levels and determine the start-up threshold value based on the short-circuit current level of the bus at each voltage level.

9. The flexible DC short-circuit current suppression strategy start-up threshold setting system according to claim 1, characterized in that, The current contribution calculation module is based on the principle of constant short-circuit capacity. According to the short-circuit current feed-in standard of 500kV voltage level flexible DC converter stations, it determines the short-circuit current contribution value of flexible DC at each voltage level through the short-circuit current conversion formula, including: Based on the principle of constant short-circuit capacity, and according to the short-circuit current feed-in standard of 500kV voltage level flexible DC converter stations, the contribution value of flexible DC short-circuit current to each voltage level grid under the conditions of short-circuit current suppression strategy activation and non-activation is calculated using the short-circuit current conversion formula.

10. The flexible DC short-circuit current suppression strategy start-up threshold setting system according to claim 1, characterized in that, The control interval division module divides the short-circuit current control intervals for different voltage levels based on the contribution values ​​of the flexible DC short-circuit current at each voltage level, including: For each voltage level, based on the breaking capacity of the circuit breaker at the corresponding voltage level and the determined contribution value of the flexible DC short-circuit current at each voltage level, short-circuit current control interval one, short-circuit current control interval two, and short-circuit current control interval three are set. Wherein, the first short-circuit current control interval is the critical value where the short-circuit current is below which the suppression strategy does not need to be activated; the second short-circuit current control interval is the critical value where the short-circuit current is above which the suppression strategy alone cannot control it within the circuit breaker's breaking capacity; and the third short-circuit current control interval is the interval between the first and second short-circuit current control intervals where the suppression strategy needs to be activated.

11. The flexible DC short-circuit current suppression strategy start-up threshold setting system according to claim 1, characterized in that, The current level calculation module calculates the bus short-circuit current level for each voltage level, including: Based on the PSD-SCCP short-circuit current calculation program, select and load the ".DAT" and ".SWI" data files in PSD format for short-circuit current calculation, calculate the near-zone short-circuit current level of the flexible DC converter station, and obtain the calculation results of the bus short-circuit current level for each voltage level.

12. The flexible DC short-circuit current suppression strategy start-up threshold setting system according to claim 1, characterized in that, The threshold value determination module determines the start-up threshold value based on the bus short-circuit current level of each voltage level, matching the short-circuit current control range of different voltage levels, including: If the bus short-circuit current level falls within the first short-circuit current control range, then there is no need to impose short-circuit current suppression technology requirements on flexible DC. If the bus short-circuit current level belongs to the second short-circuit current control range, then the flexible DC-DC transmission system scheme is adjusted without relying on the flexible DC-DC short-circuit current suppression strategy. If the bus short-circuit current level belongs to the third short-circuit current control interval, based on the PSD-SWNT time-domain simulation program, load the ".SWI" data file, perform metallic short-circuit fault simulation on all buses in the third short-circuit current control interval, record the residual voltage value of the flexible DC converter bus corresponding to each fault, select the maximum residual voltage value and reserve a preset margin as the start-up threshold value of the flexible DC short-circuit current suppression strategy.

13. The flexible DC short-circuit current suppression strategy start-up threshold setting system according to claim 1, characterized in that, When conducting simulations of metallic short-circuit faults, the receiving end of the flexible direct transmission uses a constant AC voltage control mode, and metastability calculations are performed under full-start conditions.

14. The flexible DC short-circuit current suppression strategy start-up threshold setting system according to claim 1, characterized in that, If the voltage of the flexible DC converter bus is detected to be lower than the start-up threshold, the short-circuit current suppression strategy will be activated.

15. An electronic device, characterized in that, It includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; A processor is configured to execute a program stored in a memory to implement the method for setting the start-up threshold value of the flexible DC short-circuit current suppression strategy as described in any one of claims 1-7.

16. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the method for setting the start threshold value of the flexible DC short-circuit current suppression strategy as described in any one of claims 1-7.

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