Short-circuit current control method and system for extra-high voltage direct current main grid

Abstract

The application discloses a short-circuit current control method of an extra-high voltage direct current main power grid, which comprises the following steps: obtaining data information; calculating a safety margin index and a short-circuit current reduction degree index after a scheme is adopted, a short-circuit current safety margin change amount of a future target year, a bus short-circuit current safety margin change amount of all 500-kilovolt transformer substations in a near area of a direct current converter station in the future target year, a 500-kilovolt line load rate in the near area of the direct current converter station, an average line load rate and a line load rate variance of all outgoing lines, a line load rate state amount and a 500-kilovolt line load rate variance change index of a key 500-kilovolt line in the near area of the direct current converter station under fault; calculating evaluation parameters of each scheme and selecting an optimal scheme to control the short-circuit current of the extra-high voltage direct current main power grid. The application further discloses a system for implementing the short-circuit current control method of the extra-high voltage direct current main power grid. The application has higher reliability, better accuracy and better comprehensive effect.

Description

Technical Field

[0001] This invention belongs to the field of electrical automation, specifically relating to a short-circuit current control method and system for an ultra-high voltage direct current main power grid. Background Technology

[0002] With economic and technological development and the improvement of people's living standards, electricity has become an indispensable secondary energy source in people's production and daily life, bringing endless convenience. Therefore, ensuring a stable and reliable supply of electricity has become one of the most important tasks of the power system.

[0003] With the rapid development of the power system, the scale of the power grid continues to expand, and the load on the power system continues to increase. The short-circuit current of the 500 kV power grid is increasing year by year, showing a rising trend, and the pressure on short-circuit current control of the power grid is increasing day by day. Therefore, in order to control the 500 kV short-circuit current in the vicinity of the UHVDC converter station and ensure the safe and stable operation of the system, it is necessary to propose short-circuit current control schemes and suggestions in combination with the future power grid structure.

[0004] Currently, short-circuit current control schemes for future UHVDC main grids are often proposed from one or more specific perspectives, based on the development trend of UHVDC main grids. The performance of these schemes cannot be verified or evaluated, thus failing to provide targeted short-circuit current control and potentially impacting the operation, planning, and construction of the power system. Summary of the Invention

[0005] One of the objectives of this invention is to provide a short-circuit current control method for an ultra-high voltage direct current (UHVDC) main power grid that is highly reliable, accurate, and has a good overall effect.

[0006] The second objective of this invention is to provide a system for implementing the short-circuit current control method of the ultra-high voltage direct current main grid.

[0007] The short-circuit current control method for ultra-high voltage direct current main grid provided by this invention includes the following steps:

[0008] S1. Obtain data information of the target high-voltage DC main grid and all short-circuit current control schemes to be evaluated;

[0009] S2. Based on the data obtained in step S1, calculate the safety margin index and the short-circuit current reduction index after adopting each scheme;

[0010] S3. Based on the data obtained in step S2, calculate the change in short-circuit current safety margin in the future target year after adopting each scheme;

[0011] S4. Based on the data obtained in step S3, calculate the change in the short-circuit current safety margin of all 500 kV substations near the DC converter station in the target year after each scheme is adopted.

[0012] S5. Calculate the load rate of the 500 kV lines in the vicinity of the DC converter station, the average load rate of all outgoing lines, and the variance of the line load rate after adopting each scheme;

[0013] S6. Based on the data obtained in step S5, calculate the line load rate status under fault conditions of the critical 500 kV line in the vicinity of the DC converter station after adopting each scheme.

[0014] S7. Based on the data obtained in step S6, calculate the variance change index of the 500 kV line load rate after adopting each scheme;

[0015] S8. Based on the data obtained in steps S2 to S7, calculate the evaluation parameters of the short-circuit current control scheme for each UHVDC main grid.

[0016] S9. Based on the evaluation parameters obtained in step S8, select the optimal scheme and perform short-circuit current control of the UHVDC main grid according to the optimal scheme.

[0017] Step S2, which involves calculating the safety margin index and short-circuit current reduction index based on the data information obtained in step S1, specifically includes the following steps:

[0018] Using the breaking current that the circuit breaker can withstand and the relay protection operating current setting as threshold values, the safety margin index and the short-circuit current reduction index after adopting each scheme are calculated using the following formula:

[0019]

[0020]

[0021]

[0022] In the formula α i To determine the safety margin index of the impact of the short-circuit current of the i-th substation on the normal breaking capacity of the circuit breaker after adopting the short-circuit current control scheme; I i,max I represents the breaking capacity current of the i-th 500 kV substation circuit breaker; i δ represents the short-circuit current of the i-th 500 kV substation after adopting the short-circuit current control scheme. i I is an indicator of the reduction in short-circuit current on the i-th 500 kV substation busbar after implementing a short-circuit current control scheme. i,0 δ represents the short-circuit current of the i-th 500 kV substation in the target year before any measures were taken. aveThis represents the average reduction in short-circuit current across all substations after implementing the short-circuit current control scheme; m represents the number of 500 kV substations.

[0023] Step S3, which involves calculating the change in short-circuit current safety margin in the target year based on the data obtained in step S2, specifically includes the following steps:

[0024] The following formulas are used to calculate the short-circuit current safety margin and the average change in short-circuit current safety margin in the target year after adopting each scheme:

[0025]

[0026]

[0027] In the formula α i 'This represents the safety margin of the short-circuit current in the target year for the i-th 500 kV substation after adopting the short-circuit current control scheme;' i 'This is the short-circuit current of the i-th 500 kV substation in the future target year after adopting the short-circuit current control scheme;' ΔT represents the average change in the short-circuit current safety margin of the i-th 500 kV substation from the adoption of the short-circuit current control scheme to the target year in the future; ΔT is the time period in years.

[0028] Step S4, based on the data obtained in step S3, calculates the change in the short-circuit current safety margin of all 500 kV substations near the DC converter station in the target year after adopting each scheme. This specifically includes the following steps:

[0029] The following formula is used to calculate the change in the short-circuit current safety margin of all 500 kV substations near the DC converter station in the target year after adopting each scheme:

[0030]

[0031]

[0032] In the formula This represents the average change in the safety margin of 500 kV substations near the DC converter station in the coming years after the adoption of the short-circuit current control scheme, where the short-circuit current safety margin is greater than 0. This represents the average change in the safety margin of 500 kV substations near the DC converter station in future years after the implementation of the short-circuit current control scheme, where the short-circuit current safety margin is less than 0; m1 represents the target year α'. i The number of substations ≥ 0; m2 is the target year α' i The number of substations with a value less than 0.

[0033] Step S5, which involves calculating the load rate of the 500 kV lines near the DC converter station, the average load rate of all outgoing lines, and the variance of the line load rate after adopting various schemes, specifically includes the following steps:

[0034] The following formulas are used to calculate the load factor of the 500 kV lines near the DC converter station, the average load factor of all outgoing lines, and the variance of the line load factor after adopting each scheme:

[0035]

[0036]

[0037]

[0038] In the formula β j P represents the load factor of the j-th line after implementing a short-circuit current control scheme. j,line To determine the power flow of the j-th line after implementing a short-circuit current control scheme; P j,line,N The maximum transmission power of the j-th line after adopting the short-circuit current control scheme; σ represents the average load factor of all lines after the short-circuit current control scheme is adopted; n represents the number of 500 kV lines near the DC converter station after the short-circuit current control scheme is adopted; σ represents the variance of the line load factor after the short-circuit current control scheme is adopted.

[0039] Step S6, which involves calculating the line load rate status under fault conditions of the critical 500 kV line in the vicinity of the DC converter station after adopting various schemes, based on the data information obtained in step S5, specifically includes the following steps:

[0040] The following formula is used to calculate the line load rate status under fault conditions of the critical 500 kV line in the vicinity of the DC converter station after adopting various schemes:

[0041]

[0042]

[0043] In the formula σ represents the average load factor of the remaining 500 kV lines after a 500 kV line fault following the implementation of a short-circuit current control scheme; k represents the number of remaining 500 kV lines after removing the faulty line following the implementation of the short-circuit current control scheme; σ represents the number of remaining 500 kV lines. failure The variance of the load rate of a 500 kV line under the condition of a 500 kV line fault after adopting a short-circuit current control scheme.

[0044] Step S7, which involves calculating the variance change index of the 500 kV line load rate after adopting each scheme based on the data information obtained in step S6, specifically includes the following steps:

[0045] The following formula is used to calculate the variance change index of the load rate of a 500 kV line after adopting the short-circuit current control scheme:

[0046] ε=σ failure -σ

[0047] In the formula ε i This refers to the variation index of the load rate variance of a 500 kV line after adopting a short-circuit current control scheme.

[0048] Step S8, which involves calculating the evaluation parameters of the short-circuit current control scheme for each UHVDC main grid based on the data obtained in steps S2 to S7, specifically includes the following steps:

[0049] The evaluation parameters for the short-circuit current control schemes of various UHVDC main grids are calculated using the following formula:

[0050]

[0051] In the formula, F is the evaluation parameter of the short-circuit current control scheme of the UHVDC main power grid.

[0052] Step S9, which involves selecting the optimal scheme based on the evaluation parameters obtained in step S8 and controlling the short-circuit current of the UHVDC main grid according to the optimal scheme, specifically includes the following steps:

[0053] The evaluation parameters of each short-circuit current control scheme to be evaluated are calculated using the above steps. The short-circuit current control scheme of the UHVDC main grid with the largest evaluation parameters is selected as the optimal scheme, and the short-circuit current control of the UHVDC main grid is carried out according to the optimal scheme.

[0054] This invention also provides a system for implementing the short-circuit current control method of the ultra-high voltage direct current (UHVDC) main power grid, comprising a data acquisition module, a margin and current calculation module, a margin change calculation module, a future margin change calculation module, a line load calculation module, a load rate status quantity calculation module, a load rate change quantity calculation module, an evaluation parameter calculation module, and a short-circuit current control module. The control modules are connected in series; the data acquisition module acquires data information from the target HVDC main grid and all short-circuit current control schemes to be evaluated, and uploads the data to the margin and current calculation module; the margin and current calculation module calculates the safety margin index and short-circuit current reduction index after adopting each scheme based on the received data, and uploads the data to the margin change calculation module; the margin change calculation module calculates the change in short-circuit current safety margin in the future target year after adopting each scheme based on the received data, and uploads the data to the future margin change calculation module; the future margin change calculation module calculates the change in short-circuit current safety margin in the future target year based on the received data, and uploads the data to the future margin change calculation module; the future margin change calculation module calculates the change in short-circuit current safety margin in the future target year based on the received data. The received data is used to calculate the change in the short-circuit current safety margin of all 500 kV substations near the DC converter station in the target year after implementing various schemes, and the data is uploaded to the line load calculation module. The line load calculation module is used to calculate the load rate of the 500 kV lines near the DC converter station, the average load rate of all outgoing lines, and the line load rate variance after implementing various schemes, and the data is uploaded to the load rate status calculation module. The load rate status calculation module is used to calculate the critical 500 kV lines near the DC converter station after implementing various schemes, based on the received data. The system calculates the line load rate status under fault conditions and uploads the data to the load rate change calculation module. The load rate change calculation module calculates the variance change index of the 500 kV line load rate after implementing various schemes based on the received data and uploads the data to the evaluation parameter calculation module. The evaluation parameter calculation module calculates the evaluation parameters of each short-circuit current control scheme for the UHVDC main grid based on the received data and uploads the data to the short-circuit current control module. The short-circuit current control module selects the optimal scheme based on the received data and performs short-circuit current control of the UHVDC main grid according to the optimal scheme.

[0055] The short-circuit current control method and system for the UHVDC main grid provided by this invention analyzes the most fundamental physical characteristics of the system, compares the short-circuit current control of different schemes, the long-term adaptability of different schemes and their impact on the power flow of the system, and finally achieves short-circuit current control of the UHVDC main grid. Therefore, this invention has higher reliability, better accuracy and better overall effect. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0057] Figure 2 This is a schematic diagram of the geographical wiring of a 500 kV power grid near a provincial power grid DC converter station, which is an embodiment of the method of the present invention.

[0058] Figure 3 This is a schematic diagram of short-circuit current control scheme 1 in an embodiment of the method of the present invention.

[0059] Figure 4 This is a schematic diagram of short-circuit current control scheme 2 in an embodiment of the method of the present invention.

[0060] Figure 5 This is a schematic diagram of the functional modules of the system of the present invention. Detailed Implementation

[0061] The short-circuit current control method for ultra-high voltage direct current main grid provided by this invention includes the following steps:

[0062] S1. Obtain data information of the target high-voltage DC main grid and all short-circuit current control schemes to be evaluated;

[0063] S2. Based on the data obtained in step S1, calculate the safety margin index and short-circuit current reduction index after adopting each scheme; specifically including the following steps:

[0064] Using the breaking current that the circuit breaker can withstand and the relay protection operating current setting as threshold values, the safety margin index and the short-circuit current reduction index after adopting each scheme are calculated using the following formula:

[0065]

[0066]

[0067]

[0068] In the formula α i To determine the safety margin index of the impact of the short-circuit current of the i-th substation on the normal breaking capacity of the circuit breaker after adopting the short-circuit current control scheme; I i,max I represents the breaking capacity current of the i-th 500 kV substation circuit breaker; i δ represents the short-circuit current of the i-th 500 kV substation after adopting the short-circuit current control scheme. i This value represents the degree of reduction in the short-circuit current of the i-th 500 kV substation busbar after implementing a short-circuit current control scheme. A larger value indicates a better control effect on the short-circuit current after the scheme is implemented. i,0δ represents the short-circuit current of the i-th 500 kV substation in the target year before any measures were taken. ave This represents the average reduction in short-circuit current across all substations after implementing the short-circuit current control scheme; m represents the number of 500 kV substations.

[0069] S3. Based on the data obtained in step S2, calculate the change in short-circuit current safety margin in the target year after adopting each scheme; specifically including the following steps:

[0070] The following formulas are used to calculate the short-circuit current safety margin and the average change in short-circuit current safety margin in the target year after adopting each scheme:

[0071]

[0072]

[0073] In the formula α i 'This represents the safety margin of the short-circuit current in the target year for the i-th 500 kV substation after adopting the short-circuit current control scheme;' i 'This is the short-circuit current of the i-th 500 kV substation in the future target year after adopting the short-circuit current control scheme;' ΔT represents the average change in the short-circuit current safety margin of the i-th 500 kV substation from the adoption of the short-circuit current control scheme to the target year in the future; ΔT is the time period, and the change in the short-circuit current at the DC landing point is usually checked over the next 10 years after the addition of DC.

[0074] S4. Based on the data obtained in step S3, calculate the change in the short-circuit current safety margin of all 500 kV substations near the DC converter station in the target year after adopting each scheme; specifically including the following steps:

[0075] The following formula is used to calculate the change in the short-circuit current safety margin of all 500 kV substations near the DC converter station in the target year after adopting each scheme:

[0076]

[0077]

[0078] In the formula This represents the average change in the safety margin of 500 kV substations near the DC converter station in the coming years after the adoption of the short-circuit current control scheme, where the short-circuit current safety margin is greater than 0. This represents the average change in the safety margin of 500 kV substations near the DC converter station in future years after the implementation of the short-circuit current control scheme, where the short-circuit current safety margin is less than 0; m1 represents the target year α'. iThe number of substations ≥ 0; m2 is the target year α' i The number of substations is less than 0;

[0079] S5. Calculate the load rate of the 500 kV lines near the DC converter station, the average load rate of all outgoing lines, and the variance of the line load rate after adopting each scheme; specifically including the following steps:

[0080] The following formulas are used to calculate the load factor of the 500 kV lines near the DC converter station, the average load factor of all outgoing lines, and the variance of the line load factor after adopting each scheme:

[0081]

[0082]

[0083]

[0084] In the formula β j P represents the load factor of the j-th line after implementing a short-circuit current control scheme. j,line To determine the power flow of the j-th line after implementing a short-circuit current control scheme; P j,line,N The maximum transmission power of the j-th line after adopting the short-circuit current control scheme; σ represents the average load factor of all lines after the short-circuit current control scheme is adopted; n represents the number of 500 kV lines near the DC converter station after the short-circuit current control scheme is adopted; σ represents the variance of the line load factor after the short-circuit current control scheme is adopted. The larger the value, the greater the overall fluctuation of the line load factor, and the smaller the value, the smaller the overall fluctuation of the line load factor.

[0085] S6. Based on the data obtained in step S5, calculate the line load rate status under fault conditions of the critical 500 kV line in the vicinity of the DC converter station after adopting each scheme; specifically including the following steps:

[0086] The following formula is used to calculate the line load rate status under fault conditions of the critical 500 kV line in the vicinity of the DC converter station after adopting various schemes:

[0087]

[0088]

[0089] In the formula σ represents the average load factor of the remaining 500 kV lines after a 500 kV line fault following the implementation of a short-circuit current control scheme; k represents the number of remaining 500 kV lines after removing the faulty line following the implementation of the short-circuit current control scheme; σ represents the number of remaining 500 kV lines. failure The variance of the load rate of a 500 kV line under the condition of a 500 kV line fault after adopting a short-circuit current control scheme;

[0090] S7. Based on the data obtained in step S6, calculate the variance change index of the 500 kV line load rate after adopting each scheme; specifically including the following steps:

[0091] The following formula is used to calculate the variance change index of the load rate of a 500 kV line after adopting the short-circuit current control scheme:

[0092] ε=σ failure -σ

[0093] In the formula ε i The variation index of load rate variance of a 500 kV line after adopting a short-circuit current control scheme;

[0094] S8. Based on the data obtained in steps S2 to S7, calculate the evaluation parameters of the short-circuit current control scheme for each UHVDC main grid; specifically including the following steps:

[0095] The evaluation parameters for the short-circuit current control schemes of various UHVDC main grids are calculated using the following formula:

[0096]

[0097] In the formula, F represents the evaluation parameter of the short-circuit current control scheme for the UHVDC main power grid; where, This means that for a 500 kV substation whose 500 kV bus short-circuit current does not exceed the standard in the future target year, the short-circuit current should be reduced to the greatest extent possible after adopting the short-circuit current control scheme, the 500 kV line load rate variance change index should be minimized, and the average value of the average change value of the short-circuit current safety margin should be minimized. This means that for 500 kV substations whose 500 kV bus short-circuit current does not exceed the standard in the future target year, the short-circuit current should be reduced to the greatest extent possible after adopting the short-circuit current control scheme, the 500 kV line load rate variance change index should be minimized, and the short-circuit current exceeding the standard in the target year should be minimized.

[0098] S9. Based on the evaluation parameters obtained in step S8, select the optimal scheme and perform short-circuit current control of the UHVDC main grid according to the optimal scheme; specifically including the following steps:

[0099] The evaluation parameters of each short-circuit current control scheme to be evaluated are calculated using the above steps. The short-circuit current control scheme of the UHVDC main grid with the largest evaluation parameters is selected as the optimal scheme, and the short-circuit current control of the UHVDC main grid is carried out according to the optimal scheme.

[0100] The method of the present invention will be further described below with reference to an embodiment:

[0101] Taking a short-circuit current control project in a certain province as an example, the geographical wiring diagram of the area near the DC converter station in that province is as follows: Figure 2 As shown; under normal circumstances, the maximum allowable short-circuit current of existing 500 kV substation circuit breakers, i.e., the short-circuit current breaking capacity of the circuit breaker, is 63 kA.

[0102] To control the short-circuit current of the 500 kV substation near the SSH DC converter station in the future target year, the following two control schemes are proposed. Scheme 1 is as follows: Figure 3 As shown, Scheme 2 is as follows Figure 4 As shown;

[0103] The short-circuit current under different schemes is shown in Table 1 below. Based on the short-circuit current in Table 1, the short-circuit current index of the 500 kV bus is calculated under different short-circuit current control schemes. The specific index is shown in Table 2.

[0104] Table 1. Schematic diagram of short-circuit current of 500 kV busbar under different schemes.

[0105]

[0106] Table 2. Schematic diagram of short-circuit current indicators for 500 kV busbars under different schemes.

[0107]

[0108] Based on the results in Tables 1 and 2 above, and combined with the analysis results of power flow calculations, the objective function values ​​and corresponding key indicator values ​​for different schemes can be calculated, as shown in Table 3 below:

[0109] Table 3. Schematic diagram of objective function values ​​under different schemes

[0110]

[0111] Therefore, as shown in Table 3, the objective function corresponding to Scheme 1 is greater than that of Scheme 2. Thus, Scheme 1 is the preferred short-circuit current control scheme for the UHVDC main power grid. The method proposed in this patent allows for analysis and comparison of different schemes' impact on short-circuit current control, long-term adaptability, and power flow from the system's fundamental physical characteristics. This enables short-circuit current control of the UHVDC main power grid and provides a reasonable theoretical basis and support for power grid planning and operation, which is of great significance for the safe and stable operation of the power system and power grid planning.

[0112] like Figure 5The diagram shows the functional modules of the system of this invention: The system disclosed in this invention for implementing the short-circuit current control method of the UHVDC main grid includes a data acquisition module, a margin and current calculation module, a margin change calculation module, a future margin change calculation module, a line load calculation module, a load rate status quantity calculation module, a load rate change quantity calculation module, an evaluation parameter calculation module, and a short-circuit current control module; the data acquisition module, margin and current calculation module, margin change calculation module, future margin change calculation module, line load calculation module, load rate status quantity calculation module, load rate change quantity calculation module, and evaluation parameter calculation module... The parameter calculation module and the short-circuit current control module are connected in series. The data acquisition module acquires data information from the target HVDC main grid and all short-circuit current control schemes to be evaluated, and uploads the data to the margin and current calculation module. The margin and current calculation module calculates the safety margin index and short-circuit current reduction index after adopting each scheme based on the received data, and uploads the data to the margin change calculation module. The margin change calculation module calculates the change in short-circuit current safety margin in the target year after adopting each scheme based on the received data, and uploads the data to the future margin change calculation module. The calculation module is used to calculate, based on the received data, the change in the short-circuit current safety margin of the bus short-circuit current of all 500 kV substations near the DC converter station in the target year after implementing various schemes, and uploads the data to the line load calculation module; the line load calculation module is used to calculate, based on the received data, the 500 kV line load rate, the average load rate of all outgoing lines, and the line load rate variance of the DC converter station in the target year after implementing various schemes, and uploads the data to the load rate status calculation module; the load rate status calculation module is used to calculate, based on the received data, the critical 500 kV substations near the DC converter station in the target year after implementing various schemes. The system calculates the line load rate status under a 500 kV line fault and uploads the data to the load rate change calculation module. The load rate change calculation module calculates the variance change index of the 500 kV line load rate after implementing various schemes based on the received data and uploads the data to the evaluation parameter calculation module. The evaluation parameter calculation module calculates the evaluation parameters of each short-circuit current control scheme for the UHVDC main grid based on the received data and uploads the data to the short-circuit current control module. The short-circuit current control module selects the optimal scheme based on the received data and performs short-circuit current control of the UHVDC main grid according to the optimal scheme.

Claims

1. A short-circuit current control method for an ultra-high voltage direct current (UHVDC) main power grid, comprising the following steps: S1. Obtain data information from the target high-voltage DC main grid and all short-circuit current control schemes to be evaluated; S2. Based on the data obtained in step S1, calculate the safety margin index and short-circuit current reduction index after adopting each scheme; specifically including the following steps: Using the breaking current that the circuit breaker can withstand and the relay protection operating current setting as threshold values, the safety margin index and the short-circuit current reduction index after adopting each scheme are calculated using the following formula: In the formula The safety margin index for the impact of the short-circuit current of the i-th substation on the normal breaking of the circuit breaker after adopting the short-circuit current control scheme. The interrupting capacity current of the i-th 500 kV substation circuit breaker; The short-circuit current of the i-th 500 kV substation after adopting the short-circuit current control scheme; This is an indicator of the reduction in short-circuit current of the i-th 500 kV substation busbar after adopting a short-circuit current control scheme. The short-circuit current of the i-th 500 kV substation in the target year before any measures were taken; This represents the average reduction in short-circuit current across all substations after implementing a short-circuit current control scheme. This refers to the number of 500 kV substations. S3. Based on the data obtained in step S2, calculate the change in short-circuit current safety margin in the future target year after adopting each scheme; S4. Based on the data obtained in step S3, calculate the change in the short-circuit current safety margin of all 500 kV substations near the DC converter station in the target year after adopting each scheme; specifically including the following steps: The following formula is used to calculate the change in the short-circuit current safety margin of all 500 kV substations near the DC converter station in the target year after adopting each scheme: In the formula This represents the average change in the safety margin of 500 kV substations near the DC converter station in the coming years after the adoption of the short-circuit current control scheme, where the short-circuit current safety margin is greater than 0. This is the average value of the average change in safety margin of 500 kV substations near DC converter stations in the future years after adopting the short-circuit current control scheme. For the target year The number of substations; For the target year The number of substations; S5. Calculate the load rate of the 500 kV lines in the vicinity of the DC converter station, the average load rate of all outgoing lines, and the variance of the line load rate after adopting each scheme; S6. Based on the data obtained in step S5, calculate the line load rate status under fault conditions of the critical 500 kV line in the vicinity of the DC converter station after adopting each scheme. S7. Based on the data obtained in step S6, calculate the variance change index of the 500 kV line load rate after adopting each scheme; S8. Based on the data obtained in steps S2 to S7, calculate the evaluation parameters of the short-circuit current control scheme for each UHVDC main grid. S9. Based on the evaluation parameters obtained in step S8, select the optimal scheme and perform short-circuit current control of the UHVDC main grid according to the optimal scheme.

2. The short-circuit current control method for ultra-high voltage direct current main grid according to claim 1, characterized in that... Step S3, which involves calculating the change in short-circuit current safety margin in the target year based on the data obtained in step S2, specifically includes the following steps: The following formulas are used to calculate the short-circuit current safety margin and the average change in short-circuit current safety margin in the target year after adopting each scheme: In the formula The safety margin of the short-circuit current in the future target year for the i-th 500 kV substation after adopting the short-circuit current control scheme; The short-circuit current of the i-th 500 kV substation in the future target year after adopting the short-circuit current control scheme; This represents the average change in the short-circuit current safety margin of the i-th 500 kV substation from the adoption of the short-circuit current control scheme to the target year in the future. The time period is in years.

3. The short-circuit current control method for ultra-high voltage direct current main grid according to claim 2, characterized in that... Step S5, which involves calculating the load rate of the 500 kV lines near the DC converter station, the average load rate of all outgoing lines, and the variance of the line load rate after adopting various schemes, specifically includes the following steps: The following formulas are used to calculate the load factor of the 500 kV lines near the DC converter station, the average load factor of all outgoing lines, and the variance of the line load factor after adopting each scheme: In the formula The load rate of the j-th line after adopting the short-circuit current control scheme; To determine the power flow of the j-th line after adopting a short-circuit current control scheme; The maximum transmission power of the j-th line after adopting the short-circuit current control scheme; The average load factor of all lines after the short-circuit current control scheme is adopted; n is the number of 500 kV lines near the DC converter station after the short-circuit current control scheme is adopted. The variance of line load rate after adopting a short-circuit current control scheme.

4. The short-circuit current control method for ultra-high voltage direct current main grid according to claim 3, characterized in that... Step S6, which involves calculating the line load rate status under fault conditions of the critical 500 kV line in the vicinity of the DC converter station after adopting various schemes, based on the data information obtained in step S5, specifically includes the following steps: The following formula is used to calculate the line load rate status under fault conditions of the critical 500 kV line in the vicinity of the DC converter station after adopting various schemes: In the formula The average load factor of the remaining 500 kV line in the event of a 500 kV line fault after the implementation of a short-circuit current control scheme. The number of 500 kV lines remaining after removing the faulty line following the implementation of a short-circuit current control scheme. The variance of the load rate of a 500 kV line under the condition of a 500 kV line fault after adopting a short-circuit current control scheme.

5. The short-circuit current control method for ultra-high voltage direct current main grid according to claim 4, characterized in that... Step S7, which involves calculating the variance change index of the 500 kV line load rate after adopting each scheme based on the data information obtained in step S6, specifically includes the following steps: The following formula is used to calculate the variance change index of the load rate of a 500 kV line after adopting the short-circuit current control scheme: In the formula This refers to the variation index of the load rate variance of a 500 kV line after adopting a short-circuit current control scheme.

6. The short-circuit current control method for ultra-high voltage direct current main grid according to claim 5, characterized in that... Step S8, which involves calculating the evaluation parameters of the short-circuit current control scheme for each UHVDC main grid based on the data obtained in steps S2 to S7, specifically includes the following steps: The evaluation parameters for the short-circuit current control schemes of various UHVDC main grids are calculated using the following formula: In the formula These are the evaluation parameters for the short-circuit current control scheme of the UHVDC main power grid.

7. The short-circuit current control method for ultra-high voltage direct current main grid according to claim 6, characterized in that... Step S9, which involves selecting the optimal scheme based on the evaluation parameters obtained in step S8 and controlling the short-circuit current of the UHVDC main grid according to the optimal scheme, specifically includes the following steps: The evaluation parameters of each short-circuit current control scheme to be evaluated are calculated using the above steps. The short-circuit current control scheme of the UHVDC main grid with the largest evaluation parameters is selected as the optimal scheme, and the short-circuit current control of the UHVDC main grid is carried out according to the optimal scheme.

8. A system for implementing the short-circuit current control method for an ultra-high voltage direct current main grid as described in any one of claims 1 to 7, characterized in that... It includes a data acquisition module, a margin and current calculation module, a margin change calculation module, a future margin change calculation module, a line load calculation module, a load rate status quantity calculation module, a load rate change quantity calculation module, an evaluation parameter calculation module, and a short-circuit current control module; these modules are connected in series. The data acquisition module acquires data information from the target HVDC main grid and all short-circuit current control schemes to be evaluated, and uploads the data to the margin and current calculation module. The margin and current calculation module calculates the safety margin index and short-circuit current reduction index after adopting each scheme based on the received data, and uploads the data to the margin change calculation module. The margin change calculation module is used to calculate the change in short-circuit current safety margin in the future target year after adopting each scheme based on the received data, and upload the data to the future margin change calculation module; the future margin change calculation module is used to calculate the change in short-circuit current safety margin of the bus short-circuit current of all 500 kV substations in the vicinity of the DC converter station in the future target year after adopting each scheme based on the received data, and upload the data to the line load calculation module. The line load calculation module is used to calculate the load rate of the 500 kV line in the vicinity of the DC converter station, the average load rate of all outgoing lines, and the variance of the line load rate after adopting various schemes based on the received data, and upload the data to the load rate status calculation module. The load rate status calculation module is used to calculate the line load rate status under fault conditions of the critical 500 kV line in the vicinity of the DC converter station after taking various schemes based on the received data, and upload the data to the load rate change calculation module. The load rate change calculation module is used to calculate the variance change index of the 500 kV line load rate after taking various schemes based on the received data, and upload the data to the evaluation parameter calculation module. The evaluation parameter calculation module is used to calculate the evaluation parameters of the short-circuit current control scheme for each UHVDC main grid based on the received data, and upload the data to the short-circuit current control module. The short-circuit current control module is used to select the optimal scheme based on the received data and to control the short-circuit current of the UHVDC main grid according to the optimal scheme.

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