Power grid reactive power capacity configuration method and terminal for offshore wind power large-scale grid-connection

Abstract

Disclosed in the present application are a power grid reactive power capacity configuration method and terminal for offshore wind power large-scale grid-connection. The method comprises: calculating a static voltage stability indicator and an N-2 fault relative dynamic voltage drop area indicator for each transformer substation in a regional power grid having offshore wind power large-scale multi-point grid-connection, and positioning weak voltage stability nodes, so as to predict the voltage stability risk of the regional power grid; using the nodes as candidate nodes for reactive power compensation configuration, and establishing a multi-type reactive power optimization configuration model, wherein the model has an objective function achieving the minimum total cost of a reactive power compensation device configured by the candidate nodes for reactive power compensation configuration, and comprises a static voltage stability constraint, a fault state voltage stability constraint and other constraints; and solving the model, such that the configured static reactive power compensation meets voltage regulation requirements during normal operation of the power grid, and the dynamic reactive power compensation meets reactive power support requirements during serious faults in important power transmission channels. Meanwhile, the total cost of reactive power compensation configuration is minimum, thus ensuring the voltage stability and reactive power configuration economy of systems having a high proportion of offshore wind power.

Description

Grid reactive capacity configuration method and terminal for large-scale offshore wind power grid connection

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 4, 2023, with application number 202311652731.X. The entire contents of this application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of power system planning, and in particular to a method and terminal for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection. Background Art

[0003] Offshore wind power is an important renewable energy generation method for coastal provinces. The dense integration of offshore wind power may cause the power grid in some coastal areas to transform from a receiving grid to a hybrid transmission and receiving grid with large-scale wind power transmission. This will increase the burden on specific transmission lines and bring potential voltage stability risks. However, current research on reactive voltage associated with offshore wind power transmission is limited to offshore wind power transmission lines. It does not fully consider the voltage stability issues of onshore power grids with large-scale, multi-point integration of offshore wind power, nor does it fully consider the static and dynamic multi-type reactive power support requirements in various scenarios, including normal operation and severe faults. Summary of the Invention

[0004] The technical problem to be solved by this application is to provide a grid reactive capacity configuration method and terminal for large-scale offshore wind power grid connection, which can ensure the voltage stability and reactive capacity configuration economy of the system with a high proportion of offshore wind power.

[0005] In order to solve the above technical problems, the technical solutions adopted in this application are:

[0006] A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection comprises the following steps:

[0007] Calculate the static voltage stability index of each substation in the regional power grid where offshore wind power is connected to the grid at multiple points on a large scale, and screen for weak points in static voltage stability based on the static voltage stability index of each substation;

[0008] For the static voltage stability weak point, perform N-2 fault analysis on its outgoing line, calculate the relative dynamic voltage drop area index of the static voltage stability weak point, and select candidate nodes for reactive power compensation configuration from the static voltage stability weak point based on the relative dynamic voltage drop area index;

[0009] Taking the minimum total cost of the reactive compensation device configured at the candidate node for reactive compensation configuration as the objective function, and establishing static voltage stability constraints, fault state voltage stability constraints and other constraints, a multi-type reactive power optimization configuration model considering large-scale access to offshore wind power is constructed;

[0010] Solve the multi-type reactive power optimization configuration model to obtain the optimal reactive power capacity configuration result.

[0011] In order to solve the above technical problems, another technical solution adopted in this application is:

[0012] A grid reactive capacity configuration terminal for large-scale offshore wind power grid connection includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the following steps are implemented:

[0013] Calculate the static voltage stability index of each substation in the regional power grid where offshore wind power is connected to the grid at multiple points on a large scale, and screen for weak points in static voltage stability based on the static voltage stability index of each substation;

[0014] For the static voltage stability weak point, perform N-2 fault analysis on its outgoing line, calculate the relative dynamic voltage drop area index of the static voltage stability weak point, and select candidate nodes for reactive power compensation configuration from the static voltage stability weak point based on the relative dynamic voltage drop area index;

[0015] Taking the minimum total cost of the reactive compensation device configured at the candidate node for reactive compensation configuration as the objective function, and establishing static voltage stability constraints, fault state voltage stability constraints and other constraints, a multi-type reactive power optimization configuration model considering large-scale access to offshore wind power is constructed;

[0016] Solve the multi-type reactive power optimization configuration model to obtain the optimal reactive power capacity configuration result.

[0017] The beneficial effects of the present application are: calculating the static voltage stability index and N-2 fault relative dynamic voltage drop area index of each substation (node) in the regional power grid with large-scale multi-point grid connection of offshore wind power, locating the voltage stability weak nodes in the system, realizing the prediction of the voltage stability risk of the regional power grid, and screening the reactive compensation configuration candidate nodes of the reactive power optimization configuration model, establishing and solving a multi-type reactive power optimization configuration model with the objective function of the reactive compensation device having the lowest total cost for the reactive compensation configuration candidate nodes, and including static voltage stability constraints, fault state voltage stability constraints and other constraints, so that the configured static reactive power compensation meets the voltage regulation requirements during normal operation of the power grid, and the dynamic reactive power compensation meets the reactive power support requirements during serious faults of important transmission channels. At the same time, the total cost of the reactive power compensation configuration is minimized, thereby ensuring the voltage stability and reactive power configuration economy of the offshore wind power high-proportion system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a flowchart of a method for configuring reactive capacity of a power grid for large-scale grid connection of offshore wind power according to an embodiment of the present application;

[0019] FIG2 is a schematic structural diagram of a grid reactive capacity configuration terminal for large-scale offshore wind power grid connection according to an embodiment of the present application;

[0020] FIG3 is a flow chart of a particle swarm optimization algorithm in a method for configuring reactive capacity of a power grid for large-scale grid connection of offshore wind power according to an embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to explain the technical content, achieved objectives and effects of this application in detail, the following is an explanation in conjunction with the implementation methods and the accompanying drawings.

[0022] Referring to FIG1 , a method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection includes the following steps:

[0023] Calculate the static voltage stability index of each substation in the regional power grid where offshore wind power is connected to the grid at multiple points on a large scale, and screen for weak points in static voltage stability based on the static voltage stability index of each substation;

[0024] For the static voltage stability weak point, perform N-2 fault analysis on its outgoing line, calculate the relative dynamic voltage drop area index of the static voltage stability weak point, and select candidate nodes for reactive power compensation configuration from the static voltage stability weak point based on the relative dynamic voltage drop area index;

[0025] Taking the minimum total cost of the reactive compensation device configured at the candidate node for reactive compensation configuration as the objective function, and establishing static voltage stability constraints, fault state voltage stability constraints and other constraints, a multi-type reactive power optimization configuration model considering large-scale access to offshore wind power is constructed;

[0026] Solve the multi-type reactive power optimization configuration model to obtain the optimal reactive power capacity configuration result.

[0027] From the above description, it can be seen that the beneficial effects of the present application are: calculating the static voltage stability index and N-2 fault relative dynamic voltage drop area index of each substation (node) in the regional power grid for large-scale multi-point grid connection of offshore wind power, locating the voltage stability weak nodes in the system, realizing the prediction of the voltage stability risk of the regional power grid, and screening the reactive compensation configuration candidate nodes of the reactive power optimization configuration model, establishing a multi-type reactive power optimization configuration model with the lowest total cost of the reactive compensation device for the reactive compensation configuration candidate node as the objective function, and including static voltage stability constraints, fault state voltage stability constraints and other constraints, and solving them, so that the configured static reactive compensation meets the voltage regulation requirements during normal operation of the power grid, and the dynamic reactive compensation meets the reactive support requirements during serious faults of important transmission channels. At the same time, the total cost of the reactive compensation configuration is minimized, thereby ensuring the voltage stability and reactive configuration economy of the offshore wind power high-proportion system.

[0028] Furthermore, the calculation of the static voltage stability index of each substation in the regional power grid for large-scale multi-point grid connection of offshore wind power includes:

[0029] Count the transmission nodes corresponding to each substation in the regional power grid for large-scale multi-point offshore wind power integration, and determine the typical operating conditions of the offshore wind farm;

[0030] Constructing a node admittance matrix according to the sending node, and generating a state equation under a typical operating condition of the offshore wind farm according to the node admittance matrix;

[0031] Establishing a system power flow equation under the typical working condition of the offshore wind farm based on the state equation under the typical working condition of the offshore wind farm;

[0032] Solving the system power flow equation under typical operating conditions of the offshore wind farm to obtain the apparent power output of each substation;

[0033] The static voltage stability index of each substation is calculated according to the apparent power output of each substation.

[0034] Furthermore, the calculating of the static voltage stability index of each substation according to the apparent power output of each substation includes:

[0035] Where, L j represents the static voltage stability index of substation j, represents the mutual impedance conjugate between substation j and its adjacent substation i, is the apparent power output of substation i adjacent to substation j, U i represents the bus voltage vector of substation i adjacent to substation j, |U j | represents the voltage amplitude of substation j, α Lrepresents the set of substations adjacent to substation j.

[0036] From the above description, it can be seen that the static voltage stability index characterizes the voltage stability of the substation under normal operation. Based on this index, it is helpful to accurately locate the weak points of static voltage stability in the future.

[0037] Furthermore, screening static voltage stability weaknesses based on the static voltage stability index of each substation includes:

[0038] Obtaining an average value of a static voltage stability index according to the static voltage stability index of each substation;

[0039] A target substation whose static voltage stability index is greater than the average value of the static voltage stability index is selected from the substations, and the target substation is determined as a static voltage stability weak point.

[0040] From the above description, it can be seen that the target substations whose static voltage stability index is greater than the average static voltage stability index are selected from each substation and identified as static voltage stability weak points, thereby achieving a more reasonable and reliable prediction of voltage stability risks.

[0041] Furthermore, for the static voltage stability weak point, performing N-2 fault analysis on its outgoing lines, calculating the relative dynamic voltage drop area index of the static voltage stability weak point, and screening the final reactive power compensation configuration candidate node from the static voltage stability weak point based on the relative dynamic voltage drop area index includes:

[0042] For each of the static voltage stability weak points, determine its adjacent nodes and N-2 fault disturbance conditions, and calculate the relative dynamic voltage drop area index of each of the static voltage stability weak points under the fault disturbance;

[0043] The relative dynamic voltage drop area index of each of the static voltage stability weak points is sorted in descending order, and a preset percentage of static voltage stability weak points are selected as candidate nodes for reactive power compensation configuration according to the sorted relative dynamic voltage drop area index.

[0044] As can be seen from the above description, a larger relative dynamic voltage drop area indicator indicates lower voltage stability at that node under severe fault conditions, and a greater impact on the voltage stability of adjacent nodes. The above steps can locate weak points in voltage stability during normal operation (static) and severe fault conditions. Because reactive power requires local balancing, configuring reactive power compensation at weak points in voltage stability is most effective. This also reduces the size of the subsequent optimization model and improves solution efficiency.

[0045] Furthermore, the objective function of minimizing the total cost of the reactive compensation device configured at the reactive compensation configuration candidate node includes:

[0046] Where, OF represents the total cost of the reactive compensation device configured at the candidate node for reactive compensation configuration, N k represents the total number of nodes to be selected for reactive power compensation configuration, C1 represents the unit capacity construction cost of static reactive power compensation device, Q c1_k represents the capacity of the static reactive compensation device of the kth reactive compensation configuration candidate node, C2 represents the unit capacity construction cost of the dynamic reactive compensation device, Q c2_k It represents the capacity of the dynamic reactive compensation device of the kth reactive compensation configuration candidate node.

[0047] From the above description, it can be seen that taking the lowest total cost of the reactive compensation device configured at the reactive compensation configuration candidate node as the objective function can minimize the reactive configuration cost and improve economic efficiency.

[0048] Furthermore, the static voltage stability constraints include power flow constraints and node voltage constraints under typical operating conditions of offshore wind farms;

[0049] The tidal constraints under the typical operating conditions of the offshore wind farm are:

[0050] Where, P p represents the net active power injection of node p, P qp Indicates the active power on branch qp, U q represents the voltage at node q, Q qp Represents the reactive power on branch qp, R qp Represents the equivalent resistance of branch qp, P pt represents the active power on branch pt, Ψ represents the set of system AC nodes, Φ (p,:) represents the branch set starting at node p, Φ (:,p) represents the set of branches with node p as the end, Q p represents the net reactive power injection amount of node p, X qp Indicates the equivalent reactance of branch qp, Q pt Indicates the reactive power on branch pt.

[0051] The node voltage constraint is:

[0052] Where U qN Indicates the operating voltage rating of node q.

[0053] From the above description, it can be seen that the static reactive power compensation configuration requirements during normal operation can be calculated through the power flow constraints and node voltage constraints under typical operating conditions of offshore wind farms, thereby improving the stability of the grid voltage.

[0054] Furthermore, the fault state voltage stability constraint includes:

[0055] Carry out N-2 fault verification on any important transmission channel in the system, which should meet the following requirements:

[0056] Where A i,set represents the critical transient voltage drop area threshold value of node i, Indicates the time when the voltage drops to 0.8 pu for the xth time under a certain fault; Indicates the time when the voltage recovers to above 0.8 pu for the xth time under a certain fault; represents the voltage trajectory curve of node i when the voltage is lower than 0.8 pu for the xth time under a certain fault, m represents the total number of curves with voltage lower than 0.8 pu under a certain fault, and x represents the number of times the voltage trajectory curve is lower than 0.8 pu under a certain fault;

[0057] The other constraints include capacity constraints of reactive compensation devices;

[0058] The capacity constraint of the reactive compensation device is: Q c1_k_min <Q c1_k <Q c1_k__max ; Q c2_k_min <Q c2_k <Q c2_k__max ;

[0059] Where Q c1_k_min represents the lower limit of the capacity of the static reactive power compensation device of the kth reactive power compensation configuration candidate node, Q c1_k_max represents the upper limit of the capacity of the static reactive power compensation device of the kth reactive power compensation configuration candidate node, Q c2_k_min represents the lower limit of the capacity of the dynamic reactive compensation device of the kth reactive compensation configuration candidate node, Q c2_k_max Indicates the upper limit of the capacity configured by the dynamic reactive power compensation device of the kth reactive power compensation configuration candidate node.

[0060] From the above description, it can be seen that the dynamic reactive power support capacity requirement during severe faults calculated under the dynamic voltage stability constraint under large disturbances and the reactive power compensation device capacity constraint improves the grid voltage stability.

[0061] Furthermore, solving the multi-type reactive power optimization configuration model to obtain the optimal reactive power capacity configuration result includes:

[0062] Under the static voltage stability constraint, the fault state voltage stability constraint and the other constraints, the multi-type reactive power optimization configuration model is solved using a particle swarm optimization algorithm based on the objective function to obtain the optimal capacity of the static reactive power compensation device and the optimal capacity of the dynamic reactive power compensation device configured at each reactive power compensation configuration candidate node.

[0063] From the above description, it can be seen that the reactive power compensation demand under normal operation and the dynamic voltage support demand under severe grid faults are taken into account, ensuring the voltage stability and reactive power configuration economy of the system with a high proportion of offshore wind power.

[0064] Please refer to Figure 2. Another embodiment of the present application provides a grid reactive capacity configuration terminal for large-scale offshore wind power grid connection, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, each step in the above-mentioned grid reactive capacity configuration method for large-scale offshore wind power grid connection is implemented.

[0065] The above-mentioned method and terminal for configuring reactive capacity of a grid for large-scale offshore wind power grid connection in this application can be applied to the planning scenario of a regional power grid for large-scale multi-point offshore wind power grid connection, and the following is an explanation through specific implementation methods:

[0066] Please refer to Figures 1 and 3, the first embodiment of the present application is:

[0067] A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection comprises the following steps:

[0068] S1. Calculate the static voltage stability index of each substation in the regional power grid where offshore wind power is connected to the grid on a large scale and at multiple points, and screen for weak points in static voltage stability based on the static voltage stability index of each substation, specifically including S11-S17:

[0069] S11. Count the transmission nodes corresponding to each substation in the regional power grid where offshore wind power is connected to the grid on a large scale and at multiple points, and determine the typical operating conditions of the offshore wind farm.

[0070] S12. Constructing a node admittance matrix according to the sending node, and generating a state equation under a typical operating condition of the offshore wind farm according to the node admittance matrix.

[0071] The state equation under the typical operating conditions of the offshore wind farm is specifically:

[0072] Where, I L It represents the current vector injected into the transmission node under the typical working conditions of the offshore wind farm, I G represents the current vector injected into the power node under typical operating conditions of an offshore wind farm, Y LLrepresents the self-admittance of the sending node under typical working conditions of the offshore wind farm, Y LG represents the mutual admittance from the sending node to the power node under typical working conditions of an offshore wind farm, Y GL represents the mutual admittance from the power source node to the output node under typical working conditions of an offshore wind farm, Y GG represents the self-admittance of the power node under typical working conditions of offshore wind farms, U L represents the voltage vector of the output node under typical working conditions of offshore wind farm, U G Represents the voltage vector of the power node under typical operating conditions of an offshore wind farm.

[0073] S13. Establishing a system power flow equation under the typical operating conditions of the offshore wind farm based on the state equation under the typical operating conditions of the offshore wind farm, specifically:

[0074] Among them, for offshore wind power grid-connected nodes:

[0075] Where, P wp represents the active power injection of offshore wind power grid connection node under the typical working conditions of offshore wind farm, Q wp represents the reactive power injection of offshore wind power grid connection node under the typical working conditions of offshore wind farm, P w_max represents the output data of offshore wind farm under typical working conditions, θ w Indicates the power factor of the offshore wind farm output.

[0076] S14. Solve the system power flow equation under the typical operating conditions of the offshore wind farm to obtain the apparent power delivered by each substation, that is, the power flow distribution of each substation (node), specifically:

[0077] Where, represents the apparent power sent by node j to its adjacent nodes, A represents the set of nodes adjacent to node j, and P a represents the active power sent from node j to node a, Q a Represents the reactive power sent from node j to node a.

[0078] S15. Calculate the static voltage stability index of each substation based on the apparent power output of each substation, specifically:

[0079] Where, L j represents the static voltage stability index of substation j, represents the mutual impedance conjugate between substation j and its adjacent substation i, is the apparent power output of substation i adjacent to substation j, U irepresents the bus voltage vector of substation i adjacent to substation j, |U j | represents the voltage amplitude of substation j, α L represents the set of substations adjacent to substation j.

[0080] S16. Obtaining an average value of a static voltage stability index according to the static voltage stability indexes of the respective substations.

[0081] S17. Select a target substation from the substations whose static voltage stability index is greater than the average value of the static voltage stability index, and determine the target substation as a static voltage stability weak point.

[0082] S2. For the weak point in static voltage stability, perform N-2 fault analysis on its outgoing line, calculate the relative dynamic voltage drop area index of the weak point in static voltage stability, and select candidate nodes for reactive power compensation configuration from the weak point in static voltage stability based on the relative dynamic voltage drop area index, specifically including S21-S23:

[0083] S21. For each of the static voltage stability weak points, determine its adjacent nodes and N-2 fault disturbance conditions.

[0084] S22. Calculate the relative dynamic voltage drop area index of each of the static voltage stability weak points under fault disturbance, specifically including S221-S222:

[0085] S221. Calculate the dynamic voltage drop area of ​​each of the adjacent nodes under each of the N-2 fault disturbance conditions, specifically:

[0086] Where S RTVDAI,i represents the dynamic voltage drop area of ​​each adjacent node i under each of the N-2 fault disturbance conditions, t′ start represents the time when the voltage of the adjacent node i drops to 80% of its rated value for the first time, t′ end Indicates the moment when the voltage of the adjacent node i drops to 80% or less of its rated value and then recovers and maintains above 80% of its rated value. i_N represents the voltage rating of the adjacent node i, u i (t) is the voltage trajectory curve of node i under fault.

[0087] S222. Calculate the relative dynamic voltage drop area index of each static voltage stability weak point, specifically: I RTVDAI,j =max{S RTVDAI (1),S RTVDAI (2),…,S RTVDAI(F)};

[0088] Where S RTVDAI,j (f) represents the dynamic voltage drop area of ​​all adjacent nodes of the static voltage stability weak point j under fault f, M represents the number of adjacent nodes of the static voltage stability weak point j, F represents the number of verified faults of the static voltage stability weak point j, I RTVDAI,j It represents the relative dynamic voltage drop area index of the static voltage stability weak point j, and takes S under each check fault RTVDAI,j The maximum value of (f).

[0089] S23. Sort the relative dynamic voltage drop area index of each of the static voltage stability weak points in descending order, and select a preset percentage of static voltage stability weak points as candidate nodes for reactive power compensation configuration according to the sorted relative dynamic voltage drop area index.

[0090] In an optional implementation, the preset percentage is 10%.

[0091] Specifically, the static voltage stability weak points corresponding to the top 10% relative dynamic voltage drop area indicators are selected from the sorted relative dynamic voltage drop area indicators as candidate nodes for reactive power compensation configuration.

[0092] It can locate weak points of voltage stability under normal operation (static) and under severe fault conditions. Since reactive power needs to be balanced locally, configuring reactive power compensation at weak points of static voltage stability is most effective. It can also reduce the scale of the optimization model and improve solution efficiency.

[0093] S3. Taking the minimum total cost of the reactive compensation device configured at the candidate node of the reactive compensation configuration as the objective function, and establishing static voltage stability constraints, fault state voltage stability constraints and other constraints, a multi-type reactive power optimization configuration model considering large-scale access of offshore wind power is constructed.

[0094] For local grids integrating large-scale offshore wind power, they must not only meet the requirements for reactive power compensation during normal operation of large-scale wind power transmission, but also possess the ability to provide reactive power support in the event of severe faults along key transmission channels. Static voltage stability constraints are used to calculate the static reactive power compensation configuration requirements during normal operation, while fault-state voltage stability constraints are used to calculate the dynamic reactive power support capacity requirements in the event of severe faults. This improves grid voltage stability while minimizing reactive power configuration costs.

[0095] The objective function of minimizing the total cost of the reactive compensation device configured at the reactive compensation configuration candidate node includes:

[0096] Where, OF represents the total cost of the reactive compensation device configured at the candidate node for reactive compensation configuration, N k represents the total number of nodes to be selected for reactive power compensation configuration, C1 represents the unit capacity construction cost of static reactive power compensation device, Q c1_k represents the capacity of the static reactive compensation device of the kth reactive compensation configuration candidate node, C2 represents the unit capacity construction cost of the dynamic reactive compensation device, Q c2_k It represents the capacity of the dynamic reactive compensation device of the kth reactive compensation configuration candidate node.

[0097] The static voltage stability constraints include power flow constraints and node voltage constraints under typical operating conditions of offshore wind farms;

[0098] The tidal constraints under the typical operating conditions of the offshore wind farm are:

[0099] Where, P p represents the net active power injection of node p, P qp Indicates the active power on branch qp, U q represents the voltage at node q, Q qp Represents the reactive power on branch qp, R qp Represents the equivalent resistance of branch qp, P pt represents the active power on branch pt, Ψ represents the set of system AC nodes, Φ (p,:) represents the branch set starting at node p, Φ (:,p) represents the set of branches with node p as the end, Q p represents the net reactive power injection amount of node p, X qp Indicates the equivalent reactance of branch qp, Q pt Indicates the reactive power on branch pt.

[0100] Among them, the power expression of each node is:

[0101] Where, P p1 Represents the active power output of node p, P p2 represents the active load of node p, Q p1 represents the reactive power output of node p, Q p2 Represents the reactive load of node p.

[0102] The reactive power expression of the node k to be selected for reactive compensation configuration is: Q p =Q k +Q c1_k ;

[0103] Where Q k It represents the reactive power originally injected by the candidate node k for reactive compensation configuration.

[0104] The node voltage constraint is:

[0105] Where U qN Indicates the operating voltage rating of node q.

[0106] The fault-state voltage stability constraint includes:

[0107] Carry out N-2 fault verification on any important transmission channel in the system, which should meet the following requirements:

[0108] Where A i,set represents the critical transient voltage drop area threshold value of node i, Indicates the time when the voltage drops to 0.8 pu for the xth time under a certain fault. Indicates the time when the voltage recovers to above 0.8pu for the xth time under a certain fault. represents the voltage trajectory curve of node i when the voltage is lower than 0.8 pu for the xth time under a certain fault, m represents the total number of curves with voltage lower than 0.8 pu under a certain fault, and x represents the number of times the voltage trajectory curve is lower than 0.8 pu under a certain fault.

[0109] Among them, A i,set The specific calculation method is:

[0110] Perform multi-type fault simulation on node i in advance and select the maximum voltage drop area critical value without voltage instability, specifically: A i,set =max{A 1,i,set ,A 2,i,set ,…,A z,i,set};

[0111] Where A z,i,set It represents the integral value of the voltage drop area under the zth fault.

[0112] The maximum output constraint of the dynamic reactive power compensation device configured at the kth reactive power compensation configuration candidate node in the dynamic process is: Q c2_k =max{Q′ ck(t) ,t∈[t start1 ,t end1 ]};

[0113] in,

[0114] Where Q′ ck(t) represents the reactive power output of the dynamic reactive power compensation device of the kth reactive power compensation configuration candidate node during the disturbance process, t start1 Indicates the start time of the dynamic process, t end1Indicates the end time of the dynamic process, U′ ck(t) It represents the output voltage of the dynamic reactive power compensation device configured at the kth reactive power compensation configuration candidate node during the disturbance process, U k(t) represents the voltage of the kth reactive compensation configuration candidate node during the disturbance process, ω represents the system angular velocity, and L represents the inductance of the connected reactor.

[0115] The other constraints include the capacity constraint of the reactive power compensation device, specifically: Q c1_k_min <Q c1_k <Q c1_k__max ; Q c2_k_min <Q c2_k <Q c2_k__max ;

[0116] Where Q c1_k_min represents the lower limit of the capacity of the static reactive power compensation device of the kth reactive power compensation configuration candidate node, Q c1_k_max represents the upper limit of the capacity of the static reactive power compensation device of the kth reactive power compensation configuration candidate node, Q c2_k_min represents the lower limit of the capacity of the dynamic reactive compensation device of the kth reactive compensation configuration candidate node, Q c2_k_max Indicates the upper limit of the capacity configured by the dynamic reactive power compensation device of the kth reactive power compensation configuration candidate node.

[0117] S4. Solve the multi-type reactive power optimization configuration model to obtain the optimal reactive power capacity configuration result.

[0118] Specifically, under the static voltage stability constraint, the fault state voltage stability constraint, and the other constraints, the multi-type reactive power optimization configuration model is solved using a particle swarm optimization algorithm based on the objective function to obtain the optimal capacity of the static reactive power compensation device and the optimal capacity of the dynamic reactive power compensation device configured at each reactive power compensation configuration candidate node. The process of the particle swarm optimization algorithm is shown in FIG3 .

[0119] Please refer to Figure 2, the second embodiment of this application is:

[0120] A grid reactive capacity configuration terminal for large-scale offshore wind power grid connection includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, each step of the grid reactive capacity configuration method for large-scale offshore wind power grid connection in embodiment 1 is implemented.

[0121] In summary, the present application provides a method and terminal for configuring the reactive capacity of a power grid for large-scale grid connection of offshore wind power, which calculates the static voltage stability index and the N-2 fault relative dynamic voltage drop area index of each substation (node) in the regional power grid for large-scale multi-point grid connection of offshore wind power, locates the voltage stability weak nodes in the system, realizes the prediction of the voltage stability risk of the regional power grid, and screens the reactive compensation configuration candidate nodes of the reactive optimization configuration model, establishes a multi-type reactive optimization configuration model with the objective function of minimizing the total cost of the reactive compensation device of the reactive compensation configuration candidate node, and includes static voltage stability constraints, fault state voltage stability constraints and other constraints, and solves them so that the configured Static reactive power compensation meets the voltage regulation requirements during normal operation of the power grid, and dynamic reactive power compensation meets the reactive power support requirements during serious faults in important transmission channels. At the same time, the total cost of reactive power compensation configuration is minimized, thereby ensuring the voltage stability and economic efficiency of reactive power configuration in systems with a high proportion of offshore wind power. In addition, the larger the value of the relative dynamic voltage drop area index, the lower the voltage stability level of the node under serious faults. It can locate the weak points of voltage stability under normal operation (static) and under serious faults. Since reactive power needs to be balanced on site, configuring reactive power compensation at the weak points of voltage stability is the most effective. At the same time, it can also reduce the scale of subsequent optimization models and improve solution efficiency.

[0122] The above description is merely an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent transformations made using the contents of the present application specification and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection, comprising the steps of: Calculate the static voltage stability index of each substation in the regional power grid where offshore wind power is connected to the grid on a large scale and at multiple points, and screen the weak points of static voltage stability based on the static voltage stability index of each substation; For the static voltage stability weak point, perform N-2 fault analysis on its outgoing line, calculate the relative dynamic voltage drop area index of the static voltage stability weak point, and select reactive power compensation configuration candidate nodes from the static voltage stability weak point based on the relative dynamic voltage drop area index; Taking the minimum total cost of the reactive compensation device configured at the candidate node of the reactive compensation configuration as the objective function, establishing static voltage stability constraints, fault voltage stability constraints and other constraints, and constructing a multi-type reactive power optimization configuration model considering large-scale access of offshore wind power; Solve the multi-type reactive power optimization configuration model to obtain the optimal reactive power capacity configuration result.

2. A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection according to claim 1, wherein: The calculation of the static voltage stability index of each substation in the regional power grid for large-scale multi-point grid connection of offshore wind power includes: Count the transmission nodes corresponding to each substation in the regional power grid where offshore wind power is connected to the grid on a large scale and at multiple points, and determine the typical operating conditions of offshore wind farms; Constructing a node admittance matrix according to the sending node, and generating a state equation under a typical working condition of the offshore wind farm according to the node admittance matrix; Establishing a system power flow equation under the typical working condition of the offshore wind farm based on the state equation under the typical working condition of the offshore wind farm; Solving the system power flow equation under the typical working condition of the offshore wind farm to obtain the apparent power delivered by each substation; The static voltage stability index of each substation is calculated according to the apparent power sent by each substation.

3. A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection according to claim 2, wherein: The step of calculating the static voltage stability index of each substation according to the apparent power output of each substation comprises: Where, L j represents the static voltage stability index of substation j, represents the mutual impedance conjugate between substation j and its adjacent substation i, is the apparent power delivered by substation i adjacent to substation j, U i represents the bus voltage vector of substation i adjacent to substation j, |U j | represents the voltage amplitude of substation j, α L represents the set of substations adjacent to substation j.

4. A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection according to claim 1, wherein: The screening of static voltage stability weak points based on the static voltage stability index of each substation includes: Obtaining a static voltage stability index average value according to the static voltage stability index of each substation; A target substation whose static voltage stability index is greater than the average value of the static voltage stability index is selected from the substations, and the target substation is determined as a weak point of static voltage stability.

5. A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection according to claim 1, wherein: For the static voltage stability weak point, performing N-2 fault analysis on its outgoing line, calculating the relative dynamic voltage drop area index of the static voltage stability weak point, and selecting the final reactive power compensation configuration candidate node from the static voltage stability weak point based on the relative dynamic voltage drop area index includes: For each of the static voltage stability weak points, determine its adjacent nodes and N-2 fault disturbance conditions, and calculate the relative dynamic voltage drop area index of each of the static voltage stability weak points under the fault disturbance; The relative dynamic voltage drop area index of each of the static voltage stability weak points is sorted in descending order, and a preset percentage of static voltage stability weak points are selected as candidate nodes for reactive power compensation configuration according to the sorted relative dynamic voltage drop area index.

6. A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection according to claim 1, wherein: The objective function of taking the total cost of the reactive power compensation device configured by the reactive power compensation configuration candidate node as the lowest includes: Where, OF represents the total cost of the reactive power compensation device configured at the candidate node of the reactive power compensation configuration, N k represents the total number of nodes to be selected for reactive power compensation configuration, C1 represents the unit capacity construction cost of static reactive power compensation device, Q c1_k represents the capacity of the static reactive compensation device of the kth reactive compensation configuration candidate node, C2 represents the unit capacity construction cost of the dynamic reactive compensation device, Q c2_k Represents the capacity of the dynamic reactive power compensation device of the kth reactive power compensation configuration candidate node.

7. A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection according to claim 1, wherein: The static voltage stability constraints include power flow constraints and node voltage constraints under typical operating conditions of offshore wind farms; The power flow constraints under the typical working conditions of the offshore wind farm are: Where P p represents the net active power injection amount of node p, P qp represents the active power on branch qp, U q represents the voltage at node q, Q qp Represents the reactive power on branch qp, R qp Represents the equivalent resistance of branch qp, P pt represents the active power on branch pt, Ψ represents the set of system AC nodes, Φ (p,:) represents the set of branches starting from node p, Φ (:,p) represents the set of branches with node p as the end, Q p represents the net reactive power injection amount of node p, X qp represents the equivalent reactance of branch qp, Q pt Indicates the reactive power on branch pt. The node voltage constraint is: Where U qN Represents the operating voltage rating of node q.

8. A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection according to claim 6, wherein: The fault state voltage stability constraint includes: Carry out N-2 fault verification on any important transmission channel in the system, which should meet the following requirements: In the formula, A i,set represents the critical transient voltage drop area threshold value of node i, It indicates the time when the voltage drops to 0.8pu for the xth time under a certain fault. It indicates the time when the voltage recovers to above 0.8pu for the xth time under a certain fault. represents the voltage trajectory curve of node i when the voltage is lower than 0.8pu for the xth time under a certain fault, m represents the total number of curves with voltage lower than 0.8pu under a certain fault, and x represents the number of times the voltage trajectory curve is lower than 0.8pu under a certain fault; The other constraints include capacity constraints of reactive power compensation devices; The capacity constraint of the reactive power compensation device is: Q c1_k_min <Q c1_k <Q c1_k__max ; Q c2_k_min <Q c2_k <Q c2_k__max ; In the formula, Q c1_k_min represents the lower limit of the capacity of the static reactive power compensation device of the kth reactive power compensation configuration candidate node, Q c1_k_max represents the upper limit of the capacity of the static reactive power compensation device of the kth reactive power compensation configuration candidate node, Q c2_k_min represents the lower limit of the capacity of the dynamic reactive power compensation device of the kth reactive power compensation configuration candidate node, Q c2_k_max Represents the upper limit of the capacity configured by the dynamic reactive power compensation device of the kth reactive power compensation configuration candidate node.

9. A method for configuring reactive capacity of a power grid for large-scale offshore wind power grid connection according to claim 1, wherein: The step of solving the multi-type reactive power optimization configuration model to obtain the optimal reactive power capacity configuration result includes: Under the static voltage stability constraint, the fault state voltage stability constraint and the other constraints, the multi-type reactive power optimization configuration model is solved using a particle swarm optimization algorithm based on the objective function to obtain the optimal capacity of the static reactive power compensation device and the optimal capacity of the dynamic reactive power compensation device configured at each reactive power compensation configuration candidate node.

10. A reactive capacity configuration terminal for large-scale offshore wind power grid connection, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, each step of the method for configuring reactive capacity of a power grid for large-scale grid connection of offshore wind power as described in any one of claims 1 to 9 is implemented.

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