Superconducting fault current limiter and net rack cooperative suppression method for short-circuit current of receiving-end power grid

Abstract

The invention discloses a superconducting fault current limiter and net rack cooperative suppression method for short-circuit current of a receiving-end power grid. Comprising the following steps: firstly, quantifying and constructing a short-circuit current constraint model considering superconducting fault current limiter configuration and grid structure optimization; secondly, a collaborative planning model of superconducting fault current limiter configuration and grid structure optimization is established for solving the problem that short-circuit current exceeds the standard in new energy large-scale access, traditional power supply superposition and receiving end power grid coordinated development, the main problem is responsible for long-term planning decision, the target is to minimize the total investment cost, and the main problem is responsible for long-term planning decision making. The sub-problem is responsible for checking system safe operation constraints, and the target is to minimize the operation cost. And finally, solving the model by adopting an ADMM-based short-circuit current suppression model, and effectively suppressing the short-circuit current of the receiving-end power grid through loop iteration to minimize a relaxation error. The method provides technical support for solving the problem that the short-circuit current of the receiving-end power grid exceeds the standard, and is suitable for short-circuit current control of large-scale access of new energy to the receiving-end power grid.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system safety control, and particularly relates to a superconducting fault current limiter and grid frame collaborative suppression method for short-circuit current of a receiving end power grid, and a planning and operation of a receiving end power grid with large-scale new energy access. BACKGROUND

[0002] The short-circuit current of the receiving end power grid exceeds the breaking capacity of the circuit breaker due to the large-scale access of new energy and the superposition of traditional synchronous generator units and the expansion of installed capacity. The single grid structure optimization has limited suppression effect, and large-scale adjustment reduces system reliability, and the economic cost of the superconducting fault current limiter configuration is too high, and the single configuration has poor economy. SUMMARY

[0003] The present application provides a superconducting fault current limiter and grid frame collaborative suppression method for short-circuit current of a multi-receiving end power grid, which belongs to the technical field of power system safety control. First, a short-circuit current constraint model considering superconducting fault current limiter configuration and grid structure optimization is quantified and constructed; second, for the problem of short-circuit current exceeding the standard due to large-scale access of new energy and superposition of traditional generator units and coordinated development of the receiving end power grid, a collaborative planning model of superconducting fault current limiter configuration and grid structure optimization is established; finally, the short-circuit current suppression model based on ADMM is used to solve the model, and the relaxation error is minimized through cyclic iteration to effectively suppress the short-circuit current of the receiving end power grid. The method aims to provide technical support for solving the problem of short-circuit current exceeding the standard of the receiving end power grid. Specifically, the following steps are included:

[0004] Step 1) According to the topological structure of the power grid, the short-circuit current level of each node, and the operating state of the related equipment, a short-circuit current constraint considering superconducting fault current limiter configuration and grid structure optimization is constructed, and the specific steps are as follows:

[0005] Step 1-1: Establish a branch equivalent model of the superconducting fault current limiter. The superconducting fault current limiter and the line inherent impedance are connected in series in the circuit. When the system is in normal operating condition, the superconducting fault current limiter presents low impedance characteristics, and even tends to be zero impedance state. At this time, the impedance in the line only represents the line inherent impedance. When the system fails, the impedance of the superconducting fault current limiter increases rapidly, directly limiting the path of the short-circuit current. Through line transformation, the series connection of the line inherent impedance and the limiting impedance of the superconducting fault current limiter is equivalent to a single parallel impedance between nodes i and j. At this time, the equivalent impedance is:

[0006] In the formula, Z eq is the equivalent impedance, Z ij is the line inherent impedance, and Z FCL is the limiting impedance of the superconducting fault current limiter.

[0007] After the equivalence, the fault current path is reconfigured, and the node impedance matrix needs to be updated synchronously.

[0008] Step 1-2: Construct the node impedance matrix correction model. When the superconducting fault current limiter is put into operation, the node impedance matrix of the system needs to be recalculated, and the equivalent impedance Z eq is added between nodes i and j. According to the node admittance matrix superposition theorem, the node impedance matrix Z needs to be updated synchronously to Z'. The correction formula is shown in equation (2):

[0009] In the formula, u and v are arbitrary nodes, Z u,v , Z u,i , Z u,j , Z v,i , Z v,j , Z i,i , and Z j,j are mutual impedances between nodes.

[0010] The node impedance matrix correction model quantifies the influence of the superconducting fault current limiter on the node impedance, providing a mathematical basis for constructing the short-circuit current constraint considering the superconducting fault current limiter configuration and network structure optimization.

[0011] Step 1-3: Construct the short-circuit current constraint considering the superconducting fault current limiter configuration and network structure optimization. Introduce three types of 0-1 decision variables to optimize the network structure and superconducting fault current limiter configuration, respectively, ψ n , σ m , where represents the construction state of line m, when it is constructed, when it is not constructed; ψ n represents the installation state of the nth superconducting fault current limiter, ψ n = 1 when it is installed, and ψ n = 0 when it is not installed; σ m represents the structure optimization state of line m, σ m = 1 when it is disconnected, and σ m = 0 when it is closed. By jointly deciding ψ n , σ m , the node self-impedance increment ΔZ ii is calculated.

[0012] In the formula, Γ m is the line influence coefficient, Λ m is the superconducting fault current limiter influence coefficient, Γ m and Λ m are constants, 0-1 integer variable for line construction decision of the yth planning stage, = 1 for new line construction, = 0 for new line non-construction, σ y,m 0-1 integer variable for line structure optimization of the yth planning stage, σ y,m = 1 for new line opening, = 0 for new line closing, к + , к - = set of to-be-constructed / constructed lines, M = set of superconducting fault current limiter candidate points.

[0013] Based on the above analysis, the updated node self-impedance is:

[0014] In the formula, = updated node self-impedance, = initial value of node self-impedance, I lim = maximum short-circuit current allowed for the node.

[0015] If the derived is greater than or equal to 1 / I lim , it indicates that the scheme is valid, and if the derived is less than 1 / I lim , it indicates that the scheme needs to be adjusted ψ n , σ m , the value of is recalculated, and the comparison is made again until the scheme is valid.

[0016] Step 2) Establish a collaborative planning model of superconducting fault current limiter configuration and network structure optimization with the goal of minimizing total investment cost, and the specific steps are as follows:

[0017] Step 2-1: Design the framework of the collaborative planning model of superconducting fault current limiter configuration and network structure optimization. In the collaborative planning model of superconducting fault current limiter configuration and network structure optimization, the main problem is responsible for long-term planning decision, determines the opening or new construction of output lines and the installation scheme of superconducting fault current limiter, and the goal is to minimize the total investment cost. The sub-problem is based on the planning decision result of the main problem, checks the system safe operation constraints under the main problem scheme, including short-circuit current checking, AC power flow checking, unit output checking, DC line transmission power checking, equipment standby capacity checking and reactive power margin checking, and feeds back the safe checking result, forms a cyclic optimization, and the goal is to minimize the operation cost.

[0018] Step 2-2: Main problem modeling. The core objective of the main problem is to minimize the total cycle investment cost, covering both superconducting fault current limiter configuration and network structure optimization decisions. The investment cost consists of four parts: new line investment cost, line opening operation cost, superconducting fault current limiter installation cost, and superconducting fault current limiter investment cost. The main problem needs to satisfy the construction logic constraints and network structure constraints to ensure the feasibility of the planning scheme. The construction logic constraints ensure the timing of equipment construction, and the number of new lines is limited to avoid excessive investment. The specific constraints for existing and new equipment are as follows:

[0019] wherein, is the 0-1 integer variable of line construction decision in the y-1th planning stage, ψ y,n is the 0-1 integer variable of superconducting fault current limiter installation state in the yth planning stage, ψ y,n = 1 for installation, ψ y,n = 0 for non-installation, ψ y-1,n is the 0-1 integer variable of superconducting fault current limiter installation state in the y-1th planning stage, is the maximum number of line investments, is the maximum number of superconducting fault current limiter investments.

[0020] The constraints that the network structure optimization needs to satisfy are as follows:

[0021] wherein, ρ y,m is the 0-1 integer variable of line opening state in the yth planning stage, ρ y,m = 1 for line opening state, indicating line opening or non-construction, taking value ρ y,m = 0 for line closing state.

[0022] The maximum number of open lines is also limited to avoid the risk of system splitting.

[0023] Step 2-3: Sub-problem modeling. The core objective of the main problem is to minimize the operating cost, and under the premise of fixed planning scheme, to achieve economic dispatching by adjusting unit output and power flow distribution. The sub-problem model has six constraints, among which the short-circuit current check is the core protection to ensure that the system short-circuit current size is within a reasonable range. The specific constraints are as follows:

[0024] wherein Z 原 is the initial value of self-impedance in the yth planning stage, ΔZ 网架 is the network impedance increment, ΔZ SFCL is the superconducting fault current limiter impedance increment.

[0025] The AC power flow verification uses linearization technology to process complex power flow constraints, and constraints the voltage amplitude, phase angle cosine and phase angle sine to meet the double balance of active and reactive power; the unit output verification constrains the active technical output of thermal power units to be within the technical output range, and the reactive output of thermal power units and synchronous compensators needs to meet the upper and lower limits; the DC line transmission power verification constrains the active power of UHV DC lines to be within the allowed transmission range, and the reactive power of DC lines is coupled with the active power; the equipment standby capacity verification constrains the sum of the difference between the maximum technical output and the current output of all thermal power units to be not less than the total demand for period adjustment standby, and the sum of the difference between the current output and the minimum technical output of all thermal power units needs to be not less than the total demand for period adjustment standby; the reactive power margin verification constrains the weighted sum of the difference between the maximum reactive output and the current reactive output of each thermal power unit or synchronous compensator to meet the system dynamic reactive power demand.

[0026] Step 3) The short-circuit current suppression model based on the alternating direction multiplier method is used to solve the model, and the effective suppression of the short-circuit current of the receiving end power grid is realized, and the specific steps are as follows:

[0027] Step 3-1: Problem decomposition and initialization. The alternating direction multiplier method (ADMM) is used to solve the short-circuit current suppression model of the receiving end power grid coordinated with the superconducting fault current limiter configuration and the network structure optimization. First, input the parameters and initialize the parameters. For the main problem, input the investment variable x, wherein represents the limiting current capacity, that is, the limiting impedance value of the superconducting fault current limiter. For the sub-problem, input the operating variable y, wherein y,t,i , β y,t,i,j , γ y,t,i,j are equivalent variables introduced for the linearization of the AC power flow model, the active power of the i-th thermal power unit at the t-th period of the y-th planning stage, the reactive power of the i-th thermal power unit at the t-th period of the y-th planning stage. Auxiliary variables z and dual variables u are introduced. At the same time, the initial values x 0 , y 0 , u 0 =0 are set, the penalty parameter is set, and the convergence threshold ε=10 -4 .

[0028] Step 3-2: ADMM iteration. The ADMM iteration framework decomposes the optimization problem into two sub-problems: investment decision problem and operation optimization problem, and approximates the global optimal solution by iteratively solving the two sub-problems and updating the dual variables. The ADMM iteration steps are as follows:

[0029]

[0030] u k+1 =u k +(x k+1 +y k+1 -z k+1 ) (12)

[0031] wherein formula (9) is a main problem constraint, formula (10) is a sub-problem constraint, C IN is a fixed cost term, f 运行 is a sub-problem objective function, and ρ is a penalty parameter, which is initially set to 1 and dynamically adjusted according to the residual error.

[0032] Step 3-3: Relaxation error minimization loop. After solving the sub-problem, a relaxation error minimization module is embedded to fix the operating variables Solve the relaxation problem:

[0033]

[0034] If the relaxation error is greater than ε, update and re-solve the sub-problem until the relaxation error is less than ε.

[0035] S3.4, Convergence criterion. Calculate the primal residual r k =‖x k -y k ‖ and the dual residual s k =ρ‖y k -y k-1 ‖. When r k <ε and s k <ε, the iteration ends and the optimization scheme is output, otherwise the penalty parameter is updated.

[0036] BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a flow chart of a method for suppressing short-circuit current of a receiving-end power grid by a superconducting fault current limiter in cooperation with a grid structure;

[0038] Figure 2 is a flow chart of a short-circuit current constraint for configuration of a superconducting fault current limiter and optimization of a grid structure;

[0039] Figure 3 is a structural diagram of a collaborative planning model for configuration of a superconducting fault current limiter and optimization of a grid structure;

[0040] Figure 4 is a flow chart of an ADMM algorithm. DETAILED DESCRIPTION

[0041] The present invention will now be described in further detail with reference to the accompanying drawings.

[0042] This invention proposes a method for the coordinated suppression of short-circuit current in multi-receiving-end power grids by superconducting fault current limiters and the grid structure. A detailed flowchart is attached. Figure 1 As shown.

[0043] The steps involved in a method for co-suppressing superconducting fault current limiters and grid structures for short-circuit current in multi-receiving-end power grids are as follows:

[0044] Step 1) Based on the power grid topology, the short-circuit current levels of each node, and the operating status of related equipment, construct short-circuit current constraints that take into account the configuration of superconducting fault current limiters and the optimization of the grid structure. The flowchart of the short-circuit current constraint is attached. Figure 2 As shown, the specific steps are as follows:

[0045] Step 1-1: Establish the branch equivalent model of the superconducting fault current limiter. The superconducting fault current limiter is connected in series with the inherent impedance of the line in the circuit. When the system is under normal operating conditions, the superconducting fault current limiter exhibits low impedance characteristics, even approaching zero impedance. At this time, the impedance in the line is only reflected as the inherent impedance of the line. When a system fault occurs, the impedance of the superconducting fault current limiter increases rapidly, directly limiting the path of the short-circuit current. Through line transformation, the series inherent impedance of the line and the current-limiting impedance of the superconducting fault current limiter are equivalent to a single parallel impedance between nodes i and j. The equivalent impedance is:

[0046] In the formula, Z eq For the equivalent impedance, Z ij Z is the inherent impedance of the line. FCL The current-limiting impedance is for the superconducting fault current limiter.

[0047] After the equivalent process, the fault current path is reconstructed, and the node impedance matrix needs to be updated synchronously.

[0048] Step 1-2: Construct the corrected nodal impedance matrix model. When the superconducting fault current limiter is activated, the system's nodal impedance matrix needs to be recalculated, with an equivalent impedance Z added between nodes i and j. eq At that time, according to the superposition theorem of nodal admittance matrices, the nodal impedance matrix Z needs to be updated to Z' synchronously. The corrected formula is shown in equation (2):

[0049] In the formula, u and v are arbitrary nodes, and Z u,v Z u,i Z u,j Z v,i Z v,j Z i,i Z j,j All of these are mutual impedances between nodes.

[0050] The node impedance matrix correction model quantifies the influence of superconducting fault current limiter on node impedance, and provides a mathematical basis for constructing short-circuit current constraints considering superconducting fault current limiter configuration and network structure optimization.

[0051] Step 1-3: Construct short-circuit current constraints considering superconducting fault current limiter configuration and network structure optimization. Introduce three types of 0-1 decision variables to optimize network structure and superconducting fault current limiter configuration, respectively ψ n 、σ m , where represents the construction state of line m, when it is constructed, when it is not constructed; ψ n represents the installation state of the nth superconducting fault current limiter, ψ n = 1 when installed, ψ n = 0 when not installed; σ m represents the structure optimization state of line m, σ m = 1 when disconnected, σ m = 0 when closed. Calculate the node self-impedance increment ΔZ ii by jointly deciding ψ n , σ m .

[0052] In the formula, Γ m is the line influence coefficient, Λ m is the superconducting fault current limiter influence coefficient, Γ m and Λ m are constants, is the 0-1 integer variable of line construction decision in the yth planning stage, is the new line construction, is the new line not constructed, σ y,m is the 0-1 integer variable of whether the line structure is optimized in the yth planning stage, σ y,m = 1 is the new line disconnected, is the new line closed, к + , к - is the set of to-be-built / already-built lines, and M is the set of superconducting fault current limiter candidate points.

[0053] Based on the above analysis, the updated node self-impedance is:

[0054] In the formula, is the updated node self-impedance, is the initial value of the node self-impedance, and I lim is the maximum short-circuit current allowed for the node.

[0055] If the derived is greater than or equal to 1 / I lim , it indicates that the scheme is effective, if the derived is less than 1 / I lim , it indicates that the scheme needs to be adjusted ψ n , σ m , the value is recalculated, and the comparison is made again until the scheme is effective.

[0056] Step 2) Establish a collaborative planning model of superconducting fault current limiter configuration and network structure optimization with the goal of minimizing total investment cost, the structure diagram is shown in FIG. 1, and the specific steps are as follows: Figure 3

[0057] Step 2-1: Design the collaborative planning model framework of superconducting fault current limiter configuration and network structure optimization. In the collaborative planning model of superconducting fault current limiter configuration and network structure optimization, the main problem is responsible for long-term planning decision, determines the opening or new construction of output line and the installation scheme of superconducting fault current limiter, and the target is to minimize the total investment cost. The sub-problem is based on the planning decision result of the main problem, checks the system safe operation constraints under the main problem scheme, including short-circuit current checking, AC power flow checking, unit output checking, DC line transmission power checking, equipment standby capacity checking and reactive power margin checking, and feeds back the safe checking result, forms a cyclic optimization, and the target is to minimize the operation cost.

[0058] Step 2-2: Main problem modeling. The core target of the main problem is to minimize the total investment cost in the whole cycle, which includes two types of decisions: superconducting fault current limiter configuration and network structure optimization. The investment cost is composed of four parts: new line investment cost, line opening operation cost, superconducting fault current limiter installation cost and superconducting fault current limiter investment cost. The main problem needs to meet the construction logic constraints and network structure constraints to ensure the feasibility of the planning scheme, wherein the construction logic constraints need to ensure the time sequence of equipment construction, and the number of new lines has an upper limit to avoid excessive investment. The specific constraints of the existing equipment and the new equipment are as follows:

[0059] In the formula, is the 0-1 integer variable of line construction decision in the y-1th planning stage, ψ y,n represents the 0-1 integer variable of superconducting fault current limiter installation state in the yth planning stage, ψ y,n = 1 is installed, ψ y,n = 0 is not installed, ψ y-1,n represents the 0-1 integer variable of superconducting fault current limiter installation state in the y-1th planning stage, is the maximum investment number of line,​​ Maximize the number of superconducting fault current limiters.

[0060] The constraints that need to be met for the optimization of the grid structure are:

[0061] where ρ y,m is a 0-1 integer variable of the line opening state in the yth planning stage, ρ y,m = 1 indicates that the line is in an open state, representing a line that is open or not built, and ρ y,m = 0 indicates that the line is in a closed state.

[0062] The maximum number of open lines is also limited to avoid the risk of system splitting.

[0063] Step 2-3: Sub-problem modeling. The core objective of the main problem is to minimize the operation cost. Under the premise of fixed planning scheme, economic dispatch is achieved by adjusting the unit output and power flow distribution. The sub-problem model has six constraints, among which the short-circuit current check is the core protection to ensure that the system short-circuit current is within a reasonable range. The specific constraints are:

[0064] where Z 原 is the initial value of the self-impedance in the yth planning stage, ΔZ 网架 is the grid impedance increment, and ΔZ SFCL is the superconducting fault current limiter impedance increment.

[0065] The AC power flow check uses linearization techniques to handle complex power flow constraints, including voltage amplitude, phase angle cosine, and phase angle sine constraints to satisfy both active and reactive power balance. The unit output check constrains the active technical output of thermal power units within the technical output range, and the reactive output of thermal power units and synchronous compensators within the upper and lower limits. The DC line transmission power check constrains the active power of UHVDC lines within the allowed transmission range, and the coupling of DC line reactive power and active power. The device backup capacity check constrains the sum of the difference between the maximum technical output and the current output of all thermal power units to be greater than the total demand for period adjustment, and the sum of the difference between the current output and the minimum technical output of all thermal power units to be greater than the total demand for period adjustment. The reactive power margin check constrains the weighted sum of the difference between the maximum reactive power output and the current reactive power output of each thermal power unit or synchronous compensator to meet the system dynamic reactive power demand.

[0066] Step 3) Use the short-circuit current suppression model based on the alternating direction multiplier method to solve the model and effectively suppress the short-circuit current of the receiving end grid. The ADMM algorithm flowchart is shown in FIG. 1, and the specific steps are as follows: Figure 4

[0067] ​Step 3-1: Problem decomposition and initialization. The Alternating Direction Method of Multipliers (ADMM) is used to solve the short-circuit current suppression model of the receiving-end power grid with superconducting fault current limiter configuration and grid structure optimization coordination. First, input the parameters and initialize the parameters. For the main problem, input the investment variables x, where represents the limiting current capacity, i.e., the limiting impedance value of the superconducting fault current limiter. For the sub-problem, input the operating variables y, where α y,t,i , β y,t,i,j , and γ y,t,i,j are equivalent variables introduced for linearization of the alternating current flow model, the active power output of the i-th thermal power unit at the t-th time period of the y-th planning stage, the reactive power output of the i-th thermal power unit at the t-th time period of the y-th planning stage. The auxiliary variables z and the dual variables u are introduced. The initial values x 0 , y 0 , and u 0 are set to 0, the penalty parameter is set to 1, and the convergence threshold ε is set to 10 -4 .

[0068] Step 3-2: ADMM iteration. The ADMM iteration framework decomposes the optimization problem into two sub-problems: the investment decision problem and the operation optimization problem, and approximates the global optimal solution by iteratively solving these two sub-problems and updating the dual variables. The ADMM iteration steps are as follows:

[0069]

[0070] u k+1 = u k + (x k+1 + y k+1 - z k+1 ) (12)

[0071] In the above equations, equation (9) is the constraint of the main problem, equation (10) is the constraint of the sub-problem, C IN is the fixed cost term, f 运行 is the objective function of the sub-problem, and ρ is the penalty parameter, which is initially set to 1 and dynamically adjusted according to the residual error.

[0072] Step 3-3: Relaxation error minimization loop. After solving the sub-problem, a relaxation error minimization module is embedded to fix the operating variables and solve the relaxation problem:

[0073]

[0074] If the relaxation error is greater than ε, update and re-solve the sub-problem until the relaxation error is less than ε.

[0075] S3.4, Convergence criterion. Compute the primal residual r k =‖x k -y k ‖ and the dual residual s k =ρ‖y k -y k-1 ‖. When r k <ε and s k <ε, the iteration is terminated and the optimal solution is output, otherwise the penalty parameter is updated.

[0076]

Claims

1. A method for co-suppressing superconducting fault current limiter and grid structure in response to short-circuit current in the receiving-end power grid, the main technical feature of the claims being: comprising the following steps: S1. Based on the topology of the power grid, the short-circuit current level of each node and the operating status of related equipment, construct a short-circuit current constraint that takes into account the configuration of superconducting fault current limiters and the optimization of the grid structure. S2. Establish a collaborative planning model for superconducting fault current limiter configuration and grid structure optimization with the goal of minimizing total investment cost; S3. The model is solved using the ADMM-based short-circuit current suppression model to achieve effective suppression of short-circuit current in the receiving-end power grid.

2. The method for coordinated suppression of short-circuit current in a receiving-end power grid by a superconducting fault current limiter and the grid structure, as described in claim 1, is characterized in that: Step S1 describes the specific steps for constructing short-circuit current constraints that take into account the configuration of superconducting fault current limiters and the optimization of the grid structure, based on the topology of the power grid, the short-circuit current levels of each node, and the operating status of related equipment. S1.1 Establish the branch equivalent model of the superconducting fault current limiter. The superconducting fault current limiter is connected in series with the inherent impedance of the line in the circuit. When the system is in normal operating condition, the superconducting fault current limiter exhibits low impedance characteristics, or even approaches zero impedance. At this time, the impedance in the line is only reflected as the inherent impedance of the line. During a system fault, the impedance of the superconducting fault current limiter increases rapidly, directly restricting the path of the short-circuit current. Through line transformation, the inherent impedance of the series-connected line and the current-limiting impedance of the superconducting fault current limiter are equivalent to a single parallel impedance between nodes i and j. The equivalent impedance is then: In the formula, Z eq For the equivalent impedance, Z ij Z is the inherent impedance of the line. FCL The current-limiting impedance of the superconducting fault current limiter; After the equivalent process, the fault current path is reconstructed, and the node impedance matrix needs to be updated synchronously. S1.2 Construct a corrected nodal impedance matrix model. When the superconducting fault current limiter is activated, the nodal impedance matrix of the system needs to be recalculated, and an equivalent impedance Z is added between nodes i and j. eq At that time, according to the superposition theorem of nodal admittance matrices, the nodal impedance matrix Z needs to be updated to Z' synchronously, and the correction formula is shown in equation (2): In the formula, u and v are arbitrary nodes, and Z u,v Z u,i Z u,j Z v,i Z v,j Z i,i Z j,j All of these are mutual impedances between nodes; The node impedance matrix correction model quantifies the impact of superconducting fault current limiters on node impedance, providing a mathematical basis for constructing short-circuit current constraints that take into account the configuration of superconducting fault current limiters and the optimization of grid structure. S1.3, Constructing short-circuit current constraints for superconducting fault current limiter configuration and grid structure optimization. Three types of 0-1 decision variables are introduced to collaboratively optimize the grid structure and superconducting fault current limiter configuration, namely... ψ n σ m ,in This indicates the construction status of line m. At the time of construction, At that time, no construction was undertaken; ψ n ψ represents the installation status of the nth superconducting fault current limiter. n =1 indicates installation, ψ n =0 means no installation; σ m σ represents the structural optimization state of line m. m When σ = 1, it is in the off state. m When the value is 0, the system is in a closed loop. This is achieved through joint decision-making. ψ n σ m Calculate the node self-impedance increment ΔZ ii ; In the formula, Γ m Λ is the line influence coefficient. m Γ represents the influence coefficient of the superconducting fault current limiter. m and Λ m All are constants. Let y be an integer variable (0-1) representing the decision on the construction of the line in the y-th planning stage. For the construction of the new line, No new lines will be built, σ y,m Let σ be a 0-1 integer variable indicating whether the route structure is optimized in the y-th planning stage. y,m =1 indicates that the new line is disconnected. For the new line to be closed, к + , к - For the set of lines to be built / built, M is the set of alternative points for superconducting fault current limiters; Based on the above analysis, the updated node self-impedance is: In the formula, The updated node self-impedance, Let I be the initial value of the node self-impedance. lim This is the maximum short-circuit current allowed at the node; If the result is... Greater than or equal to 1 / I lim If the result is... Less than 1 / I lim This indicates that the plan needs to be adjusted. ψ n σ m Recalculate The values ​​are then compared until the solution is valid.

3. The method for coordinated suppression of short-circuit current in a receiving-end power grid by a superconducting fault current limiter and the grid structure, as described in claim 1, is characterized in that: The specific steps for establishing the collaborative planning model for superconducting fault current limiter configuration and grid structure optimization with the goal of minimizing total investment cost, as described in step S2, are as follows: S2.1, Design a collaborative planning model framework for the configuration and grid structure optimization of superconducting fault current limiters. In the collaborative planning model for the configuration and grid structure optimization of superconducting fault current limiters, the main problem is responsible for long-term planning decisions, determining whether to disconnect or rebuild the output line and the installation scheme of the superconducting fault current limiter, with the objective of minimizing the total investment cost; The sub-problems, based on the planning and decision-making results of the main problem, verify the system's safe operation constraints under the main problem's scheme, including short-circuit current verification, AC power flow verification, unit output verification, DC line transmission power verification, equipment reserve capacity verification, and reactive power margin verification. The safety verification results are then fed back to form a cyclical optimization, with the goal of minimizing operating costs. S2.2, Main Problem Modeling. The core objective of the main problem is to minimize the total lifecycle investment cost, encompassing two types of decisions: superconducting fault current limiter configuration and grid structure optimization. The investment cost consists of four parts: investment cost of new lines, cost of line disconnection operations, installation cost of superconducting fault current limiters, and investment cost of superconducting fault current limiters. The main issue requires meeting both the construction logic constraints and the grid structure constraints to ensure the feasibility of the planning scheme. The construction logic constraints must guarantee the timing of equipment construction, and there is an upper limit to the number of new lines to avoid over-investment. Specific constraints on existing and new equipment are as follows: In the formula, Let ψ be an integer variable (0-1) for the line construction decision in the (y-1)th planning stage. y,n ψ is a 0-1 integer variable representing the installation status of the superconducting fault current limiter in the y-th planning stage. y,n =1 indicates installation, ψ y,n =0 means not to install, ψ y-1,n This represents a 0-1 integer variable indicating the installation status of the superconducting fault current limiter in the (y-1)th planning stage. This represents the maximum investment amount for the line. This represents the maximum investment quantity for superconducting fault current limiters; The constraints that need to be satisfied for the optimization of the space frame structure are: In the formula, ρ y,m Let ρ be a 0-1 integer variable representing the line opening / closing state in the y-th planning stage. y,m When ρ = 1, the line is in an open state, indicating that the line is disconnected or has not been constructed. y,m When = 0, the circuit is in a closed state; At the same time, the maximum number of lines to be disconnected should be limited to avoid the risk of system failure; S2.3 Sub-problem Modeling; The core objective of the main problem is to minimize operating costs. Under the premise of a fixed planning scheme, economic dispatch is achieved by adjusting unit output and power flow distribution. The sub-problem model has six constraints, among which short-circuit current verification is the core protection, ensuring that the system's short-circuit current is within a reasonable range. The specific constraints are as follows: In the formula Z 原 Let ΔZ be the initial value of the self-impedance in the y-th planning stage. 网架 The impedance increment of the network structure, ΔZ SFCL For the impedance increment of the superconducting fault current limiter; The AC power flow verification employs linearization techniques to handle complex power flow constraints, imposing constraints on voltage amplitude, phase angle cosine, and phase angle sine to ensure a dual balance between active and reactive power. The unit output verification constrains the active power output of thermal power units to be within their technical output range, and the reactive power output of thermal power units and synchronous condensers to meet upper and lower limits. The DC line transmission power verification constrains the active power of UHVDC lines to be within the allowable transmission range, and ensures that reactive power and active power are coupled. The equipment reserve capacity verification constrains the sum of the differences between the maximum technical output and current output of all thermal power units to be no less than the total reserve demand adjusted upwards during the time period, and the sum of the differences between the current output and minimum technical output of all thermal power units to be no less than the total reserve demand adjusted downwards during the time period. The reactive power margin verification constrains the weighted sum of the differences between the maximum reactive power output and current reactive power output of each thermal power unit or synchronous condenser to meet the system's dynamic reactive power demand.

4. The method for co-suppressing superconducting fault current limiter and grid structure in response to short-circuit current in the receiving-end power grid as described in claim 1, characterized in that: The specific steps for effectively suppressing the short-circuit current in the receiving-end power grid are as follows: The model is solved using a short-circuit current suppression model based on the alternating direction multiplier method. S3. Problem Decomposition and Initialization: The Alternating Direction Method of Multipliers (ADMM) is used to solve the receiving-end power grid short-circuit current suppression model that coordinates superconducting fault current limiter configuration and grid structure optimization. First, the parameters are input and initialized. For the main problem, the investment variable x is input. in This represents the current-limiting capacity, i.e., the current-limiting impedance value of the superconducting fault current limiter. For the subproblem input variable y, Where α y,t,i β y,t,i,j γ y,t,i,j Equivalent variables introduced to facilitate the linearization of the power flow model. The active power output of the i-th thermal power unit during time period t in the y-th planning phase. The reactive power output of the i-th thermal power unit in the y-th planning phase t-time is calculated by introducing auxiliary variable z and dual variable u. An initial value x is also set. 0 ,y 0 ,u 0 =0, set the penalty parameter, convergence threshold ε=10 -4 ; S3. ADMM Iteration: The ADMM iterative framework decomposes the optimization problem into two sub-problems: the investment decision problem and the operational optimization problem. It approximates the global optimum by alternately solving these two sub-problems and updating the dual variable. The ADMM iterative steps are as follows: u k+1 =u k +(x k+1 +y k+1 -z k+1 ) (12) In the formula, equation (9) represents the main problem constraint, and equation (10) represents the subproblem constraint. IN For fixed cost items, f 运行 Let ρ be the objective function of the subproblem, and let ρ be the penalty parameter, which is initially set to 1 and dynamically adjusted according to the residual. S3. Relaxation error minimization loop: After solving the subproblems, the relaxation error minimization module is embedded, and the running variables are fixed. Solving the relaxation problem: If the relaxation error is greater than ε, update Then resolve the subproblem until the relaxation error is less than ε; S3. Convergence determination, calculation of the original residual r k =‖x k -y k ‖ and dual residual s k =ρ‖y k -y k-1 ||. When r k <ε and s k When the value is less than ε, the iteration ends and the optimized solution is output; otherwise, the penalty parameter is updated.

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