Method and system for identifying critical load nodes considering the degree of reactive voltage coupling

Abstract

The application discloses a kind of considering reactive voltage coupling degree's key load node identification method and system, according to power system net frame topological structure and initial flow data, establish the weighted undirected graph of power system, then the minimum edge weight value accumulation of node is solved, the electrical connection degree between nodes is obtained, again based on flow matrix, the reactive voltage coupling degree between nodes is solved, the weighted summation of reactive voltage coupling degree between nodes and electrical connection degree between nodes is carried out, and the node importance degree evaluation result is obtained, and key load node is identified according to node importance degree evaluation result. Line impedance, active power and reactive voltage coupling degree are comprehensively considered, the existing evaluation node connection degree and the key load node technology of identifying it ignore the reactive voltage coupling degree between nodes, leading to the node connection degree evaluation and the identification result of key node do not conform to actual situation, and the technical problem of reliability is not high.

Description

Technical Field

[0001] This invention relates to the field of power system load node identification technology, and in particular to a method and system for identifying critical load nodes that takes into account the degree of reactive power-voltage coupling. Background Technology

[0002] In complex power systems, nodes have a certain degree of electrical distance and coupling. For a given node, assessing the degree of connection between it and multiple nodes below its voltage level, identifying key nodes among these nodes, and then selectively performing comprehensive load modeling is of great significance for reducing computational complexity and improving computational efficiency.

[0003] Traditional techniques for assessing inter-node connectivity typically use electrical distance as a metric, evaluating connectivity based on line impedance; lower impedance indicates closer proximity. However, relying solely on impedance ignores energy transfer along the tie lines. Even with the same tie line impedance, different energy transfer amounts result in varying degrees of connectivity between nodes. Therefore, existing techniques further measure coupling between adjacent nodes using the ratio of active power to impedance; lower impedance and higher active power transmission indicate closer electrical connectivity. However, this still neglects reactive and voltage coupling. In complex power systems, reactive and voltage interactions are often more crucial for stability analysis. Assessing and identifying connectivity and critical nodes solely based on line impedance and active power is unrealistic and unreliable. Therefore, providing a method for identifying critical load nodes that considers reactive and voltage coupling, enabling reasonable and accurate assessment of inter-node connectivity and identification of critical load nodes, is a pressing technical problem for those skilled in the art. Summary of the Invention

[0004] This invention provides a method and system for identifying critical load nodes that considers the degree of reactive power-voltage coupling. It addresses the technical problem that existing technologies for assessing the degree of connection between nodes and identifying critical load nodes neglect the degree of reactive power-voltage coupling between nodes, resulting in assessments of the degree of connection between nodes and identification of critical nodes that do not conform to reality and have low reliability.

[0005] In view of this, the first aspect of the present invention provides a method for identifying critical load nodes considering the degree of reactive power-voltage coupling, comprising:

[0006] Based on the power system network topology and initial power flow data, a weighted undirected graph of the power system is constructed, where the edge weights of the weighted undirected graph are:

[0007]

[0008] Among them, W ij Let x be the edge weight between node i and node j in a weighted undirected graph. ij p represents the per-unit value of the impedance of the tie line between node i and node j. ij The per-unit value represents the amount of active power transmitted through the link between node i and node j;

[0009] Calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system to obtain the degree of electrical connection between the nodes;

[0010] A power flow matrix is ​​established based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude at the nodes of the power system. The degree of reactive voltage coupling between nodes is then calculated based on the power flow matrix.

[0011] The reactive voltage coupling degree and the electrical connection degree between nodes are weighted and summed to obtain the node importance assessment result. Based on the node importance assessment result, critical load nodes are identified.

[0012] Optionally, the power flow matrix is:

[0013]

[0014] Where ΔP is the change in active power injection at the node, ΔQ is the change in reactive power injection at the node, Δθ is the change in the node voltage phase angle, ΔV is the change in the node voltage magnitude, K is the partial derivative matrix of the change in active power injection at the node with respect to the change in the node voltage phase angle, and J is the partial derivative matrix of the change in reactive power injection at the node with respect to the change in the node voltage magnitude.

[0015] The formulas for calculating the elements of the partial derivative matrix K of the change in active power injection with respect to the change in node voltage phase angle and the partial derivative matrix J of the change in node reactive power injection with respect to the change in node voltage magnitude are as follows:

[0016]

[0017] Among them, K ij J is the element in the i-th row and j-th column of the partial derivative matrix K of the change in active power injection at the node with respect to the change in the phase angle of the node voltage. ij The element in the i-th row and j-th column of the partial derivative matrix J of the reactive power injection change with respect to the node voltage magnitude change is given by: h = number of active nodes, o = number of reactive nodes, V = ... i V is the voltage at the i-th node. j Let B be the voltage at the j-th node. ij Let be the imaginary part of the node impedance matrix of the branch with first node i and last node j.

[0018] Optionally, a power flow matrix is ​​established based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude at the power system nodes. The degree of reactive-voltage coupling between nodes is then calculated based on the power flow matrix, including:

[0019] Establish a power flow matrix based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude at the nodes of the power system.

[0020] For each power system node, determine whether it is a DC system feed-in node. If not, directly invert the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change to obtain the degree of reactive power-voltage coupling between nodes. If it is, correct the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change based on the DC system injected power, and then invert the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change to obtain the degree of reactive power-voltage coupling between nodes.

[0021] Optionally, the formula for weighted summation of the reactive voltage coupling degree between nodes and the electrical connection degree between nodes is:

[0022]

[0023] Among them, D i→k W represents the importance of node i to node k. i→k Let $\mathbf{i}$ be the sum of the minimum edge weights from node $i$ to node $k$, used to characterize the degree of electrical connection between nodes. Let J be the element in the i-th row and k-th column of the inverse matrix of the partial derivative matrix J of the node reactive power injection change with respect to the node voltage magnitude change, which is used to characterize the degree of reactive voltage coupling between nodes.

[0024] Optionally, the correction formula for correcting the partial derivative matrix J of the change in reactive power injection at the node with respect to the change in the magnitude of the node voltage, based on the injected power of the DC system, is as follows:

[0025]

[0026]

[0027] Among them, J′ kk The element in the k-th row and k-th column of the partial derivative matrix J of the nodal reactive power injection change with respect to the nodal voltage magnitude change at the corrected DC system feed-in node k is J. kk Q is the element in the k-th row and k-th column of the partial derivative matrix J of the nodal reactive power injection change with respect to the nodal voltage magnitude change. k The reactive power injected into node k, V kLet N be the voltage at node k, N be the number of converter bridges, T be the turns ratio of the inverter-side converter transformer, and X be the voltage at node k. c γ is the commutation reactance, γ is the turn-off angle, and β is the trigger lead angle.

[0028] Optionally, the path with the minimum sum of edge weights between any two nodes in the weighted undirected graph of the power system is calculated to obtain the degree of electrical connection between the nodes, including:

[0029] The Floyd algorithm is used to calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system, thereby obtaining the degree of electrical connection between the nodes.

[0030] A second aspect of the present invention provides a critical load node identification system considering the degree of reactive power-voltage coupling, comprising:

[0031] The undirected graph construction module is used to build a weighted undirected graph of the power system based on the power system network topology and initial power flow data. The edge weights of the weighted undirected graph of the power system are:

[0032]

[0033] Among them, W ij Let x be the edge weight between node i and node j in a weighted undirected graph. ij p represents the per-unit value of the impedance of the tie line between node i and node j. ij The per-unit value represents the amount of active power transmitted through the link between node i and node j;

[0034] The module for calculating the degree of electrical connectivity between nodes is used to calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system, thereby obtaining the degree of electrical connectivity between nodes.

[0035] The module for calculating the degree of reactive voltage coupling between nodes is used to establish a power flow matrix based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude of the nodes in the power system, and to calculate the degree of reactive voltage coupling between nodes based on the power flow matrix.

[0036] The critical load identification module is used to perform a weighted summation of the reactive voltage coupling degree and the electrical connection degree between nodes to obtain the node importance assessment result, and to identify critical load nodes based on the node importance assessment result.

[0037] Optionally, the power flow matrix is:

[0038]

[0039] Where ΔP is the change in active power injection at the node, ΔQ is the change in reactive power injection at the node, Δθ is the change in the node voltage phase angle, ΔV is the change in the node voltage magnitude, K is the partial derivative matrix of the change in active power injection at the node with respect to the change in the node voltage phase angle, and J is the partial derivative matrix of the change in reactive power injection at the node with respect to the change in the node voltage magnitude.

[0040] The formulas for calculating the elements of the partial derivative matrix K of the change in active power injection with respect to the change in node voltage phase angle and the partial derivative matrix J of the change in node reactive power injection with respect to the change in node voltage magnitude are as follows:

[0041]

[0042] Among them, K ij J is the element in the i-th row and j-th column of the partial derivative matrix K of the change in active power injection at the node with respect to the change in the phase angle of the node voltage. ij The element in the i-th row and j-th column of the partial derivative matrix J of the reactive power injection change with respect to the node voltage magnitude change is given by: h = number of active nodes, o = number of reactive nodes, V = ... i V is the voltage at the i-th node. j Let B be the voltage at the j-th node. ij Let be the imaginary part of the node impedance matrix of the branch with first node i and last node j.

[0043] Optionally, the module for calculating the degree of reactive voltage coupling between nodes is specifically used for:

[0044] Establish a power flow matrix based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude at the nodes of the power system.

[0045] For each power system node, determine whether it is a DC system feed-in node. If not, directly invert the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change to obtain the degree of reactive power-voltage coupling between nodes. If it is, correct the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change based on the DC system injected power, and then invert the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change to obtain the degree of reactive power-voltage coupling between nodes.

[0046] Optionally, the formula for weighted summation of the reactive voltage coupling degree between nodes and the electrical connection degree between nodes is:

[0047]

[0048] Among them, D i→k W represents the importance of node i to node k. i→kLet $\mathbf{i}$ be the sum of the minimum edge weights from node $i$ to node $k$, used to characterize the degree of electrical connection between nodes. Let J be the element in the i-th row and k-th column of the inverse matrix of the partial derivative matrix J of the node reactive power injection change with respect to the node voltage magnitude change, which is used to characterize the degree of reactive voltage coupling between nodes.

[0049] Optionally, the correction formula for correcting the partial derivative matrix J of the change in reactive power injection at the node with respect to the change in the magnitude of the node voltage, based on the injected power of the DC system, is as follows:

[0050]

[0051]

[0052] Among them, J k ′ k The element in the k-th row and k-th column of the partial derivative matrix J of the nodal reactive power injection change with respect to the nodal voltage magnitude change at the corrected DC system feed-in node k is J. kk Q is the element in the k-th row and k-th column of the partial derivative matrix J of the nodal reactive power injection change with respect to the nodal voltage magnitude change. k The reactive power injected into node k, V k Let N be the voltage at node k, N be the number of converter bridges, T be the turns ratio of the inverter-side converter transformer, and X be the voltage at node k. c γ is the commutation reactance, γ is the turn-off angle, and β is the trigger lead angle.

[0053] Optionally, the undirected graph building module is specifically used for:

[0054] The Floyd algorithm is used to calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system, thereby obtaining the degree of electrical connection between the nodes.

[0055] As can be seen from the above technical solutions, the critical load node identification method and system considering the degree of reactive voltage coupling provided by the present invention have the following advantages:

[0056] This invention provides a method for identifying critical load nodes that considers reactive power-voltage coupling. Based on the power system network topology and initial power flow data, a weighted undirected graph of the power system is established. The minimum edge weights between nodes are then summed to obtain the electrical connectivity between nodes. Next, the reactive power-voltage coupling between nodes is calculated based on the power flow matrix. A weighted sum of the reactive power-voltage coupling and electrical connectivity between nodes is then performed to obtain a node importance assessment result. Critical load nodes are identified based on this assessment result. By comprehensively considering line impedance, active power, and reactive power-voltage coupling, this method can more accurately assess the connectivity between nodes and identify critical load nodes. It solves the problem that existing techniques for assessing connectivity between nodes and identifying critical load nodes neglect the reactive power-voltage coupling between nodes, leading to unrealistic assessments and unreliable identification results.

[0057] The critical load node identification system considering the degree of reactive power voltage coupling provided by this invention is used to execute the critical load node identification method considering the degree of reactive power voltage coupling provided by this invention. Its principle and the technical effect achieved are the same as the critical load node identification method considering the degree of reactive power voltage coupling provided by this invention, and will not be repeated here. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 This is a flowchart illustrating the critical load node identification method considering the degree of reactive voltage coupling provided in this invention.

[0060] Figure 2 This is a diagram of the IEEE-9 node system architecture provided in this invention;

[0061] Figure 3 In response to Figure 2 A schematic diagram showing the results of searching for the shortest path between node 9 and nodes 1 and 3 in the IEEE-9 node system architecture diagram.

[0062] Figure 4 This is a schematic diagram of the critical load node identification system that considers the degree of reactive voltage coupling provided in this invention. Detailed Implementation

[0063] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] For easier understanding, please refer to Figure 1 This invention provides an embodiment of a critical load node identification method considering the degree of reactive power voltage coupling, comprising:

[0065] Step 101: Based on the power system network topology and initial power flow data, establish a weighted undirected graph of the power system.

[0066] It should be noted that the edge weights of the weighted undirected graph of the power system, constructed based on the power system network topology and initial power flow data, are as follows:

[0067]

[0068] Among them, W ij Let x be the edge weight between node i and node j in a weighted undirected graph. ij p represents the per-unit value of the impedance of the tie line between node i and node j. ij This represents the per-unit value of the active power transmitted through the link between node i and node j.

[0069] Step 102: Calculate the path with the minimum sum of edge weights between any two nodes in the weighted undirected graph of the power system to obtain the degree of electrical connection between the nodes.

[0070] It should be noted that the Floyd algorithm, used in graph theory to find the shortest path between two points, can be used to calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system. The Floyd algorithm, also known as the insertion method, is an algorithm that uses dynamic programming to find the shortest path between nodes in a given weighted graph. Specifically, the steps for calculating the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system based on the Floyd algorithm are as follows:

[0071] 1) Input the node numbers and edge weights of each link in the weighted undirected graph of the system;

[0072] 2) Select the node k to be examined and any node i. Select any path from node i to node k as the initial path, and sum the edge weights as the initial electrical connection size between node i and node k.

[0073] 3) Start the iteration, and replace the nodes on the initial path by inserting each other node in turn. If the sum of the edge weights of the path from node i to node k after the node replacement is less than the sum of the edge weights of the initial path, then update the path and perform the next iteration replacement.

[0074] 4) Repeat step 3) until all nodes have been traversed. If no path with a smaller sum of edge weights than the current path is found, then the current path is taken as the shortest path from node i to node k, and its sum of edge weights is output. This is the minimum sum of edge weights from node i to node k, and the formula is:

[0075]

[0076] Among them, W i→k W is the minimum cumulative edge weight from node i to node k, used to characterize the degree of electrical connection between nodes. m Let n be the sum of the minimum edge weights from node i to node k, and let n be the sum of the edge weights on the m-th node connection line on the path.

[0077] The calculation result of the above formula reflects the minimum cumulative edge weight between node i and node k, characterized by line impedance and active power. The smaller the value, the closer the electrical connection between the nodes.

[0078] Step 103: Establish a power flow matrix based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude of the power system nodes, and calculate the degree of reactive voltage coupling between nodes based on the power flow matrix.

[0079] It should be noted that the power flow matrix is ​​established based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude at the power system nodes. The power flow matrix is ​​as follows:

[0080]

[0081] Where ΔP is the change in active power injection at the node, ΔQ is the change in reactive power injection at the node, Δθ is the change in the node voltage phase angle, ΔV is the change in the node voltage magnitude, K is the partial derivative matrix of the change in active power injection at the node with respect to the change in the node voltage phase angle, and J is the partial derivative matrix of the change in reactive power injection at the node with respect to the change in the node voltage magnitude.

[0082] The formulas for calculating the elements of the partial derivative matrix K of the change in active power injection with respect to the change in node voltage phase angle and the partial derivative matrix J of the change in node reactive power injection with respect to the change in node voltage magnitude are as follows:

[0083]

[0084] Among them, K ij J is the element in the i-th row and j-th column of the partial derivative matrix K of the change in active power injection at the node with respect to the change in the phase angle of the node voltage. ij The element in the i-th row and j-th column of the partial derivative matrix J of the reactive power injection change with respect to the node voltage magnitude change is given by: h = number of active nodes, o = number of reactive nodes, V = ... i V is the voltage at the i-th node. j Let B be the voltage at the j-th node. ij Let be the imaginary part of the node impedance matrix of the branch with first node i and last node j.

[0085] Inverse matrix J of the partial derivative matrix J of the change in reactive power injection at the node with respect to the change in the magnitude of the node voltage. -1 The degree of reactive voltage coupling between nodes can be obtained.

[0086] In one embodiment, for each power system node, it is determined whether it is a DC system feed-in node. If not, the inverse matrix J of the partial derivative matrix of the node's reactive power injection change with respect to the node's voltage amplitude change is directly obtained to determine the reactive power-voltage coupling degree between nodes. If it is, the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change is corrected based on the DC system injected power, and then the inverse matrix J of the partial derivative matrix of the node's reactive power injection change with respect to the node's voltage amplitude change is obtained to determine the reactive power-voltage coupling degree between nodes. For example, for node k, if it is a DC system feed-in node, the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change is corrected based on the DC system injected power. The correction formula is:

[0087]

[0088]

[0089] Among them, J′ kk The element in the k-th row and k-th column of the partial derivative matrix J of the nodal reactive power injection change with respect to the nodal voltage magnitude change at the corrected DC system feed-in node k is J. kk Q is the element in the k-th row and k-th column of the partial derivative matrix J of the nodal reactive power injection change with respect to the nodal voltage magnitude change. k The reactive power injected into node k, V k Let N be the voltage at node k, N be the number of converter bridges, T be the turns ratio of the inverter-side converter transformer, and X be the voltage at node k. c γ is the commutation reactance, β is the turn-off angle, and β is the trigger lead angle.

[0090] Then find the inverse matrix J of J. -1 Read J -1 The element in the i-th row and k-th column It characterizes the degree of reactive voltage coupling between node i and node k; the larger the value, the higher the degree of reactive voltage coupling.

[0091] Step 104: Perform a weighted summation of the reactive voltage coupling degree and the electrical connection degree between nodes to obtain the node importance assessment result, and identify the critical load nodes based on the node importance assessment result.

[0092] It should be noted that a weighted sum is applied to the reactive voltage coupling degree and the electrical interconnection degree between nodes to evaluate the importance of node i to node k. The formula for this weighted summation is as follows:

[0093]

[0094] Among them, D i→k W represents the importance of node i to node k. i→k Let $\mathbf{i}$ be the sum of the minimum edge weights from node $i$ to node $k$, used to characterize the degree of electrical connection between nodes. Let J be the element in the i-th row and k-th column of the inverse matrix of the partial derivative matrix J of the node reactive power injection change with respect to the node voltage magnitude change, which is used to characterize the degree of reactive voltage coupling between nodes.

[0095] D i→k The smaller the value, the greater the importance of node i, which means it is a more critical load node when the load model is equivalent.

[0096] To facilitate understanding, this invention provides an application example of a critical load node identification method considering the degree of reactive power-voltage coupling, with a case analysis conducted in the IEEE-9 node system, such as... Figure 2 As shown, taking node 9 as the examined node, the importance of nodes 1 and 3 relative to node 9 is evaluated and compared. First, according to step 101, the edge weights of the system's weighted undirected graph are established. The Floyd algorithm is then used to search for the shortest paths between node 9 and nodes 1 and 3, respectively. The results are as follows: Figure 3 As shown in the formula. The minimum cumulative edge weights between node 9 and nodes 1 and 3 are calculated to be W. 1→9 =0.4086 and W 3→9 =0.3620. The reactive voltage coupling degree between nodes is calculated and read according to step 103, where the reactive voltage coupling degree index between node 9 and node 1 is... Reactive voltage coupling index between node 9 and node 3 Calculate the importance of nodes 1 and 3 relative to node 9 according to step 104, where D 1→9 =0.3585, D 3→9=0.3781. Therefore, after comprehensively considering the reactive power and voltage interaction and coupling degree between nodes, node 1 is more important to node 9 than node 3. That is, node 1 should be considered a critical node, and load node 1 should receive higher attention when constructing the comprehensive load model. It is worth noting that if only line impedance and active power are considered to evaluate the node connectivity, since W 1→9 >W 3→9 Therefore, node 3 is more important to node 9 than node 1. This shows that considering the degree of reactive voltage coupling between nodes can more accurately identify the critical load nodes.

[0097] This invention provides a method for identifying critical load nodes that considers reactive power-voltage coupling. Based on the power system network topology and initial power flow data, a weighted undirected graph of the power system is established. The minimum edge weights between nodes are then summed to obtain the electrical connectivity between nodes. Next, the reactive power-voltage coupling between nodes is calculated based on the power flow matrix. A weighted sum of the reactive power-voltage coupling and electrical connectivity between nodes is then performed to obtain a node importance assessment result. Critical load nodes are identified based on this assessment result. By comprehensively considering line impedance, active power, and reactive power-voltage coupling, this method can more accurately assess the connectivity between nodes and identify critical load nodes. It solves the problem that existing techniques for assessing connectivity between nodes and identifying critical load nodes neglect the reactive power-voltage coupling between nodes, leading to unrealistic assessments and unreliable identification results.

[0098] For easier understanding, please refer to Figure 4 This invention provides an embodiment of a critical load node identification system that considers the degree of reactive power-voltage coupling, comprising:

[0099] The undirected graph construction module is used to build a weighted undirected graph of the power system based on the power system network topology and initial power flow data. The edge weights of the weighted undirected graph of the power system are:

[0100]

[0101] Among them, W ij Let x be the edge weight between node i and node j in a weighted undirected graph. ij p represents the per-unit value of the impedance of the tie line between node i and node j. ij The per-unit value represents the amount of active power transmitted through the link between node i and node j;

[0102] The module for calculating the degree of electrical connectivity between nodes is used to calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system, thereby obtaining the degree of electrical connectivity between nodes.

[0103] The module for calculating the degree of reactive voltage coupling between nodes is used to establish a power flow matrix based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude of the nodes in the power system, and to calculate the degree of reactive voltage coupling between nodes based on the power flow matrix.

[0104] The critical load identification module is used to perform a weighted summation of the reactive voltage coupling degree and the electrical connection degree between nodes to obtain the node importance assessment result, and to identify critical load nodes based on the node importance assessment result.

[0105] Optionally, the power flow matrix is:

[0106]

[0107] Where ΔP is the change in active power injection at the node, ΔQ is the change in reactive power injection at the node, Δθ is the change in the node voltage phase angle, ΔV is the change in the node voltage magnitude, K is the partial derivative matrix of the change in active power injection at the node with respect to the change in the node voltage phase angle, and J is the partial derivative matrix of the change in reactive power injection at the node with respect to the change in the node voltage magnitude.

[0108] The formulas for calculating the elements of the partial derivative matrix K of the change in active power injection with respect to the change in node voltage phase angle and the partial derivative matrix J of the change in node reactive power injection with respect to the change in node voltage magnitude are as follows:

[0109]

[0110] Among them, K ij J is the element in the i-th row and j-th column of the partial derivative matrix K of the change in active power injection at the node with respect to the change in the phase angle of the node voltage. ij The element in the i-th row and j-th column of the partial derivative matrix J of the reactive power injection change with respect to the node voltage magnitude change is given by: h = number of active nodes, o = number of reactive nodes, V = ... i V is the voltage at the i-th node. j Let B be the voltage at the j-th node. ij Let be the imaginary part of the node impedance matrix of the branch with first node i and last node j.

[0111] Optionally, the module for calculating the degree of reactive voltage coupling between nodes is specifically used for:

[0112] Establish a power flow matrix based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude at the nodes of the power system.

[0113] For each power system node, determine whether it is a DC system feed-in node. If not, directly invert the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change to obtain the degree of reactive power-voltage coupling between nodes. If it is, correct the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change based on the DC system injected power, and then invert the partial derivative matrix J of the node's reactive power injection change with respect to the node's voltage amplitude change to obtain the degree of reactive power-voltage coupling between nodes.

[0114] Optionally, the formula for weighted summation of the reactive voltage coupling degree between nodes and the electrical connection degree between nodes is:

[0115]

[0116] Among them, D i→k W represents the importance of node i to node k. i→k Let $\mathbf{i}$ be the sum of the minimum edge weights from node $i$ to node $k$, used to characterize the degree of electrical connection between nodes. Let J be the element in the i-th row and k-th column of the inverse matrix of the partial derivative matrix J of the node reactive power injection change with respect to the node voltage magnitude change, which is used to characterize the degree of reactive voltage coupling between nodes.

[0117] Optionally, the correction formula for correcting the partial derivative matrix J of the change in reactive power injection at the node with respect to the change in the magnitude of the node voltage, based on the injected power of the DC system, is as follows:

[0118]

[0119]

[0120] Among them, J′ kk The element in the k-th row and k-th column of the partial derivative matrix J of the nodal reactive power injection change with respect to the nodal voltage magnitude change at the corrected DC system feed-in node k is J. kk Q is the element in the k-th row and k-th column of the partial derivative matrix J of the nodal reactive power injection change with respect to the nodal voltage magnitude change. k The reactive power injected into node k, V k Let N be the voltage at node k, N be the number of converter bridges, T be the turns ratio of the inverter-side converter transformer, and X be the voltage at node k. c γ is the commutation reactance, β is the turn-off angle, and β is the trigger lead angle.

[0121] Optionally, the undirected graph building module is specifically used for:

[0122] The Floyd algorithm is used to calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system, thereby obtaining the degree of electrical connection between the nodes.

[0123] The critical load node identification system considering the degree of reactive power voltage coupling provided by this invention is used to execute the critical load node identification method considering the degree of reactive power voltage coupling provided by this invention. Its principle and the technical effect achieved are the same as the critical load node identification method considering the degree of reactive power voltage coupling provided by this invention, and will not be repeated here.

[0124] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for identifying critical load nodes considering the degree of reactive power-voltage coupling, characterized in that, include: Based on the power system network topology and initial power flow data, a weighted undirected graph of the power system is constructed, where the edge weights of the weighted undirected graph are: in, For nodes in a weighted undirected graph i and nodes j The edge weights between them For nodes i and nodes j The per-unit impedance of the connecting lines between them. For nodes i and nodes j The per-unit value of the active power transmitted by the connecting lines between them; Calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system to obtain the degree of electrical connection between the nodes; A power flow matrix is ​​established based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude at the nodes of the power system. The degree of reactive voltage coupling between nodes is then calculated based on the power flow matrix. The reactive voltage coupling degree and the electrical connection degree between nodes are weighted and summed to obtain the node importance assessment result. Based on the node importance assessment result, critical load nodes are identified. The trend matrix is ​​as follows: in, Inject changes into the active power of the nodes. Injecting changes into the reactive power of nodes. This represents the change in the phase angle of the node voltage. This represents the change in the magnitude of the node voltage. K The partial derivative matrix of the change in active power injection at the node with respect to the change in the phase angle of the node voltage. J The partial derivative matrix of the change in reactive power injection at the node with respect to the change in the magnitude of the node voltage; The partial derivative matrix of the change in active power injection at the node with respect to the change in the phase angle of the node voltage. K The partial derivative matrix of the change in reactive power injection at nodes with respect to the change in the magnitude of node voltage. J The formulas for calculating the elements are as follows: in, The partial derivative matrix of the change in active power injection at the node with respect to the change in the phase angle of the node voltage. K The i Line 1 j Column elements, The partial derivative matrix of the reactive power injection change at the node with respect to the change in the node voltage magnitude. J The i Line 1 j Column elements, h This represents the number of active nodes. o This represents the number of reactive power nodes. Let be the voltage of the i-th node. For the first j Node voltage, For the first node i End node is j The imaginary part of the nodal impedance matrix of the branch.

2. The critical load node identification method considering reactive power-voltage coupling as described in claim 1, comprising establishing a power flow matrix based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude of power system nodes, and calculating the degree of reactive power-voltage coupling between nodes based on the power flow matrix, including: Establish a power flow matrix based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude at the nodes of the power system. For each power system node, determine whether it is a DC system feed-in node. If not, directly calculate the partial derivative matrix of the node's reactive power injection change with respect to the node's voltage amplitude change. J Find the inverse matrix to obtain the degree of reactive voltage coupling between nodes. If so, then use the partial derivative matrix of the DC system injected power with respect to the change in reactive power injection at the nodes and the change in the magnitude of the node voltage. J After making corrections, the partial derivative matrix of the change in reactive power injection at the node with respect to the change in the node voltage amplitude is then calculated. J Find the inverse matrix to obtain the degree of reactive voltage coupling between nodes.

3. The critical load node identification method considering reactive power-voltage coupling as described in claim 2, characterized in that, The formula for weighted summation of the reactive voltage coupling degree and the electrical interconnection degree between nodes is as follows: in, For nodes i For nodes k The importance of A node is used to characterize the degree of electrical connection between nodes. i To the node k The minimum sum of edge weights, This is the partial derivative matrix of the node reactive power injection change with respect to the node voltage magnitude change, used to characterize the degree of reactive power-voltage coupling between nodes. J The inverse matrix i Line 1 k The elements of the column.

4. The critical load node identification method considering reactive power-voltage coupling as described in claim 2, characterized in that, The partial derivative matrix of DC system injected power with respect to the change in reactive power injection at nodes and the change in node voltage amplitude. J The correction formula is as follows: in, The partial derivative matrix of the change in reactive power injection at node k corresponding to the corrected DC system feed-in node with respect to the change in node voltage magnitude. J The k Line number k Column elements, The partial derivative matrix of the reactive power injection change at the node with respect to the change in the node voltage magnitude. J The k Line number k Column elements, For nodes k Injected reactive power, For nodes k voltage, N The number of converter bridges, T For the inverter-side converter transformer turns ratio, For commutation reactance, For the shut-off angle, To trigger the leading angle.

5. The critical load node identification method considering reactive power-voltage coupling as described in claim 1, characterized in that, Calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system to obtain the degree of electrical connectivity between the nodes, including: The Floyd algorithm is used to calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system, thereby obtaining the degree of electrical connection between the nodes.

6. A critical load node identification system considering the degree of reactive power-voltage coupling, characterized in that, include: The undirected graph construction module is used to build a weighted undirected graph of the power system based on the power system network topology and initial power flow data. The edge weights of the weighted undirected graph of the power system are: in, For nodes in a weighted undirected graph i and nodes j The edge weights between them For nodes i and nodes j The per-unit impedance of the connecting lines between them. For nodes i and nodes j The per-unit value of the active power transmitted by the connecting lines between them; The module for calculating the degree of electrical connectivity between nodes is used to calculate the path with the minimum sum of edge weights between any two nodes in a weighted undirected graph of a power system, thereby obtaining the degree of electrical connectivity between nodes. The module for calculating the degree of reactive voltage coupling between nodes is used to establish a power flow matrix based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude of the nodes in the power system, and to calculate the degree of reactive voltage coupling between nodes based on the power flow matrix. The critical load identification module is used to perform a weighted summation of the reactive voltage coupling degree and the electrical connection degree between nodes to obtain the node importance assessment result, and to identify critical load nodes based on the node importance assessment result; The trend matrix is ​​as follows: in, Inject changes into the active power of the nodes. Injecting changes into the reactive power of nodes. This represents the change in the phase angle of the node voltage. This represents the change in the magnitude of the node voltage. K The partial derivative matrix of the change in active power injection at the node with respect to the change in the phase angle of the node voltage. J The partial derivative matrix of the change in reactive power injection at the node with respect to the change in the magnitude of the node voltage; The partial derivative matrix of the change in active power injection at the node with respect to the change in the phase angle of the node voltage. K The partial derivative matrix of the change in reactive power injection at nodes with respect to the change in the magnitude of node voltage. J The formulas for calculating the elements are as follows: in, The partial derivative matrix of the change in active power injection at the node with respect to the change in the phase angle of the node voltage. K The i Line number j Column elements, The partial derivative matrix of the reactive power injection change at the node with respect to the change in the node voltage magnitude. J The i Line number j Column elements, h This represents the number of active nodes. o This represents the number of reactive power nodes. Let be the voltage of the i-th node. For the first j Node voltage, For the first node i End node is j The imaginary part of the nodal impedance matrix of the branch.

7. The critical load node identification system considering reactive power-voltage coupling as described in claim 6, characterized in that, The module for calculating the degree of reactive voltage coupling between nodes is specifically used for: Establish a power flow matrix based on the changes in active power injection, reactive power injection, voltage phase angle, and voltage amplitude at the nodes of the power system. For each power system node, determine whether it is a DC system feed-in node. If not, directly calculate the partial derivative matrix of the node's reactive power injection change with respect to the node's voltage amplitude change. J Find the inverse matrix to obtain the degree of reactive voltage coupling between nodes. If so, then use the partial derivative matrix of the DC system injected power with respect to the change in reactive power injection at the nodes and the change in the node voltage amplitude. J After making corrections, the partial derivative matrix of the change in reactive power injection at the node with respect to the change in the node voltage amplitude is then calculated. J Find the inverse matrix to obtain the degree of reactive voltage coupling between nodes.

8. The critical load node identification system considering reactive power-voltage coupling as described in claim 7, characterized in that, The formula for weighted summation of the reactive voltage coupling degree and the electrical interconnection degree between nodes is as follows: in, For nodes i For nodes k The importance of A node is used to characterize the degree of electrical connection between nodes. i To the node k The minimum sum of edge weights, This is the partial derivative matrix of the node reactive power injection change with respect to the node voltage magnitude change, used to characterize the degree of reactive power-voltage coupling between nodes. J The inverse matrix i Line 1 k The elements of the column.

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