Power grid vulnerable line identification method and system based on power flow betweenness

Abstract

The application provides a power grid fragile line identification method and system based on power flow betweenness, relates to the technical field of fragile line identification, and the method comprises the following steps: calculating the branch branch coefficient of the power grid topology structure; the transmission power of the transmission line and the node branch coefficient are calculated according to the branch branch coefficient, the total injected power of the first end node is calculated according to the node branch coefficient; the power sequence distribution matrix of the topology structure and the inverse matrix of the power sequence distribution matrix are obtained according to the transmission power and the total injected power; the first sub-matrix, the second sub-matrix and the third sub-matrix are obtained according to the inverse matrix of the power sequence distribution matrix; the power flow betweenness of the transmission line is calculated according to the transmission power, the total injected power, the first sub-matrix, the second sub-matrix and the third sub-matrix, and the fragile line is identified according to the power flow betweenness. The method does not depend on the result of power flow calculation, when the operating state of the power system changes, the power flow calculation of repeated iteration is not needed, and the efficiency of fragile line identification can be improved.

Description

Technical Field

[0001] This application relates to the field of vulnerable line identification technology, and in particular to a method and system for identifying vulnerable power grid lines based on power flow betweenness. Background Technology

[0002] Vulnerable lines are those lines that, when disturbed or faulted, could trigger widespread cascading failures or even system collapse in the power system (grid). When identifying vulnerable lines, methods based on complex network theory analyze the tendency of the power grid to maintain its topological integrity and normal operation after physical units or cascaded disconnections occur when the power system is disturbed or faulted. These methods are only related to the power system's topology and impedance parameters and cannot reflect the impact of dynamic power flow changes on vulnerable lines. While indicators such as power flow betweenness coefficients used for vulnerable line identification can reflect changes in the power system state, calculating the power flow betweenness coefficient requires prior power flow calculations.

[0003] Power flow calculation requires iteration. Common algorithms such as the Newton-Raphson algorithm and the Gauss-Seidel iterative method require repeated iterations to obtain a converged power flow. Moreover, the larger the power system, the longer the iteration calculation time, resulting in low efficiency in calculating the power flow betweenness. Whether using power flow tracing or iterative methods to calculate power flow, both require considerable computation time, failing to meet the requirement of rapid identification of vulnerable lines and resulting in low identification efficiency. Summary of the Invention

[0004] This application provides a method and system for identifying vulnerable power grid lines based on power flow betweenness to solve the problem of low efficiency in identifying vulnerable lines.

[0005] The first aspect of this application provides a method for identifying vulnerable power grid lines based on power flow betweenness, including:

[0006] Calculate the branching coefficient of the power grid topology; the topology includes power generation nodes, load nodes, transmission nodes and at least one transmission line, the power generation nodes are connected to the load nodes through the transmission line, the transmission nodes are nodes on the transmission line, the transmission nodes include head nodes and tail nodes, and the branching coefficient is the amount of power change on any transmission line when the power of the transmission node changes.

[0007] The transmission power and node branch coefficient of the transmission line are calculated based on the branch branch coefficient, and the total injected power of the first node is calculated based on the node branch coefficient; the node branch coefficient is the amount of power change of one of the transmission nodes when the power of the other transmission node changes.

[0008] The power order allocation matrix of the topology and the inverse matrix of the power order allocation matrix are obtained based on the transmission power and the total injected power, and the elements in the power order allocation matrix are the allocation coefficients of the total injected power on the transmission line;

[0009] The first submatrix, the second submatrix, and the third submatrix are obtained by inverse matrix of the power order allocation matrix; the elements in the first submatrix are the power allocation coefficients for the total injected power allocated from the power node to the transmission line, the elements in the second submatrix are the power allocation coefficients for the total injected power allocated from the transmission line to the load node, and the elements in the third submatrix are the power allocation coefficients for the total injected power allocated from the power node to the load node.

[0010] The power flow betweenness of the transmission line is calculated based on the transmission power, the total injected power, the first submatrix, the second submatrix, and the third submatrix, in order to identify vulnerable lines based on the power flow betweenness, which is used to assess the vulnerability of the transmission line.

[0011] Optionally, the calculation of the branch branch coefficients of the power grid topology includes:

[0012] Obtain the node impedance matrix of the topology, and calculate the branch coefficient based on the elements in the node impedance matrix; the value of the element in the node impedance matrix is ​​equal to the voltage value of another transmission node when unit power is injected at any transmission node.

[0013] Optionally, the branch coefficient can be calculated using the following formula:

[0014] ;

[0015] Where d represents the transmission line, and n represents any transmission node on any transmission line other than transmission line d. Let be the branching coefficient of transmission line d. Let n be the voltage at the first node of transmission line d when unit power is injected at transmission node n. Let n be the voltage at the terminal node of transmission line d when unit power is injected at transmission node n. and The voltage values ​​are equal to the values ​​of the elements in the node impedance matrix. Let d be the impedance of the transmission line.

[0016] Optionally, the transmission power can be calculated using the following formula:

[0017] ;

[0018] in, For transmission power, Let be the row vector of branch coefficients. This is the power column vector of the power nodes. This is the column vector of load node power;

[0019] The node branch coefficient is calculated using the following formula:

[0020] ;

[0021] in, Let be the node branching coefficient of transmission node k when the power of transmission node n changes, and C be the set of transmission lines. The branching coefficients of the c transmission lines connected to transmission node k;

[0022] The total injected power is calculated using the following formula:

[0023] ;

[0024] in, For total injected power, The row vector represents the branch coefficients of the nodes.

[0025] Optionally, the elements in the power order allocation matrix can be calculated using the following formula:

[0026] ;

[0027] in, The elements in the power order assignment matrix are used, where s is the first node of the transmission line and t is the last node of the transmission line. .

[0028] Optionally, the first submatrix, the second submatrix, and the third submatrix are submatrices of the inverse of the power order allocation matrix.

[0029] Optionally, the power flow betweenness of the transmission line can be calculated using the following formula:

[0030] ;

[0031] in, Let G be the power flow betweenness, L be the set of power supply nodes, and i be the set of load nodes; j be the power supply node and j be the load node. This refers to the power capacity of the power node. For the load capacity of the load node, This represents the minimum value of both the power supply capacity and the load capacity. Let be the element in the s-th row and i-th column of the first submatrix. Let be the element in the s-th row and j-th column of the second submatrix. Let be the element in the i-th row and j-th column of the third submatrix.

[0032] Optionally, identifying vulnerable lines based on the power flow betweenness includes:

[0033] The power flow betweenness is normalized to obtain normalized data;

[0034] The normalized data is sorted, and a predetermined number of transmission lines that rank highest are identified as vulnerable lines.

[0035] Optionally, the power flow betweenness factor can be normalized using the following formula:

[0036] ;

[0037] in, To normalize the data, This represents the maximum vulnerability of the transmission line. This represents the minimum vulnerability of the transmission line.

[0038] A second aspect of this application provides a power grid vulnerable line identification system based on power flow betweenness factor, applied to the power grid vulnerable line identification method based on power flow betweenness factor provided in the first aspect. The system includes:

[0039] First calculation module: used to calculate the branching coefficient of the power grid topology; the topology includes power generation nodes, load nodes, transmission nodes and at least one transmission line, the power generation nodes are connected to the load nodes through the transmission lines, the transmission nodes are nodes on the transmission lines, the transmission nodes include head nodes and tail nodes, and the branching coefficient is the amount of power change on any transmission line when the power of the transmission node changes.

[0040] The second calculation module is used to calculate the transmission power and node branch coefficient of the transmission line based on the branch branch coefficient, so as to calculate the total injected power of the first node based on the node branch coefficient; the node branch coefficient is the power change of the other transmission node when the power of one of the transmission nodes changes.

[0041] The third calculation module is used to obtain the power order allocation matrix of the topology and the inverse matrix of the power order allocation matrix based on the transmission power and the total injected power, wherein the elements in the power order allocation matrix are the allocation coefficients of the total injected power on the transmission line;

[0042] The fourth calculation module is used to obtain a first submatrix, a second submatrix, and a third submatrix based on the inverse of the power order allocation matrix; the elements in the first submatrix are the power allocation coefficients for the total injected power allocated from the power supply node to the transmission line, the elements in the second submatrix are the power allocation coefficients for the total injected power allocated from the transmission line to the load node, and the elements in the third submatrix are the power allocation coefficients for the total injected power allocated from the power supply node to the load node.

[0043] Identification Calculation Module: Used to calculate the power flow betweenness of the transmission line based on the transmission power, the total injected power, the first sub-matrix, the second sub-matrix, and the third sub-matrix, so as to identify vulnerable lines based on the power flow betweenness, which is used to evaluate the vulnerability of the transmission line.

[0044] This application provides a method and system for identifying vulnerable power grid lines based on power flow betweenness. The method includes: calculating branch branch coefficients of the power grid topology; calculating the transmission power and node branch coefficients of the transmission lines based on the branch branch coefficients, and calculating the total injected power of the head node based on the node branch coefficients; obtaining the power order allocation matrix and its inverse matrix of the topology based on the transmission power and total injected power; obtaining a first submatrix, a second submatrix, and a third submatrix based on the inverse matrix of the power order allocation matrix; and calculating the power flow betweenness of the transmission lines based on the transmission power, total injected power, the first submatrix, the second submatrix, and the third submatrix, to identify vulnerable lines based on the power flow betweenness. This method does not rely on the results of power flow calculations. When the operating state of the power system changes, only the power of the source nodes and the power of the load nodes need to be updated, eliminating the need for iterative power flow calculations and improving the efficiency of vulnerable line identification. Attached Figure Description

[0045] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram illustrating an example of a power grid topology node and transmission line provided in an embodiment of this application.

[0047] Figure 2 A flowchart of a power grid vulnerable line identification method based on power flow betweenness provided in this application embodiment;

[0048] Figure 3 This is a schematic diagram of a 5-node power grid topology provided in an embodiment of this application;

[0049] Figure 4A schematic diagram of the structure of a power grid vulnerable line identification system based on power flow betweenness provided in this application embodiment. Detailed Implementation

[0050] The embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described below do not represent all embodiments consistent with this application. They are merely examples of systems and methods consistent with some aspects of this application as detailed in the claims.

[0051] Power flow betweenness factors and other metrics reflect changes in the state of a power system and are commonly used for identifying vulnerable lines. However, calculating power flow betweenness factors requires prior power flow calculations. Power flow calculations involve iterations; common algorithms like the Newton-Raphson algorithm and the Gauss-Seidel iterative method require repeated iterations to achieve convergence. Furthermore, the larger the power system, the longer the iteration time, resulting in low computational efficiency for power flow betweenness factors. Whether using power flow tracing or iterative methods, the computation time is considerable, failing to meet the requirement for rapid identification of vulnerable lines and leading to low identification efficiency.

[0052] To address the problem of low efficiency in identifying vulnerable power lines, some embodiments of this application provide a method for identifying vulnerable power lines in a power grid based on power flow betweenness. Before describing the identification method of this application, a brief explanation of power flow betweenness is provided. In a power system, when power flow (i.e., power, in the case of power flow in the power grid, active power) is transmitted from power source nodes to load nodes, it needs to pass through some transmission lines in the power grid. The larger the proportion of the power flow transmitted by any transmission line in the total power flow, the more important it is in the power flow transmission, and the more vulnerable it is in the power system. By summing up the importance of all power flow transmission lines in the power grid when transmitting power between all power source and load nodes, the vulnerability index of the transmission line in the entire network, i.e., the power flow betweenness, can be obtained.

[0053] A power grid topology includes power generation nodes, load nodes, transmission nodes, and at least one transmission line. Power generation nodes are connected to load nodes via transmission lines. It can be understood that transmission nodes are nodes on a transmission line, and transmission nodes include starting nodes and ending nodes. (See [link to relevant documentation]). Figure 1 , Figure 1 In this diagram, G5 and G6 are power supply nodes, L5 and L6 are load nodes, p7, p8, and p9 are transmission nodes, and lx and ly are transmission lines. Figure 1Taking transmission line lx as an example, p7 is the starting node of transmission line lx, and p8 is the ending node of transmission line lx. For transmission line ly, p8 is the starting node of transmission line ly, and p9 is the ending node of transmission line ly. For a combined transmission line of lx and ly, p7 is the starting node, p9 is the ending node, and p8 is a transmission node on the transmission line. Let the transmission line be st, s be the starting node of the transmission line, and t be the ending node of the transmission line. Then the power flow betweenness of transmission line st can be expressed as:

[0054] (1)

[0055] in, Let G be the power flow betweenness, G be the set of power supply nodes, L be the set of load nodes, i be a power supply node, and j be a load node. This refers to the power capacity of the power node. For the load capacity of the load node, This represents the minimum value of both the power supply capacity and the load capacity. Power flow (power) is the flow of electricity from the power source node to the load node. Let be the component of the power flow transmitted between source-load node pairs on the transmission line st, where the source-load node pair is a power supply-load node pair (i, j). The values ​​of i and j can be 1, 2, 3, ..., N.

[0056] According to the definition of power flow betweenness, power flow calculation is required first. Based on the power flow tracing method, the components of the power flow transmitted between source-load node pairs on the transmission line st can be calculated using the following formula. :

[0057] (2)

[0058] in, Allocate power to the transmission line for power node i. Assign power to the transmission line to load node j. Let be the transmission power of any transmission line st. In formula (2), the power allocated to the transmission line by power node i and the power allocated to the transmission line by load node j can be calculated by the following formulas respectively:

[0059] (3)

[0060] in, For power node power, For load node power, The total injected power of the first node s. This is the first submatrix. This is the element in the s-th row and i-th column of the first submatrix; For the second submatrix, This is the element in the s-th row and j-th column of the second submatrix.

[0061] The power transferred from the power source node to the load node can be calculated using the following formula. :

[0062] (4)

[0063] in, For the third submatrix, The element in the i-th row and j-th column of the third submatrix. In the above formulas (3)-(4), A is the power order allocation matrix. The power order allocation matrix A is used to reflect the distribution relationship of the total injected power of the first node s on each transmission line, that is, the proportion of the transmission power on the transmission line st to the total injected power of the first node s. Therefore, it can be understood that the elements in the power order allocation matrix A are the distribution coefficients of the total injected power on the transmission lines. The power order allocation matrix A is an N×N matrix, where N is the total number of nodes in the power grid.

[0064] , , The inverse matrix A of the power order allocation matrix A is respectively -1 If the submatrix is ​​, then the third submatrix It is an M×N matrix, where M is the total number of power supply nodes. The elements in the matrix only include the inverse matrix A. -1 The columns corresponding to the power supply nodes. First submatrix. Let be a D×M matrix, where D is the number of the first and last nodes of the transmission line st. The elements in the matrix only include the inverse matrix A. -1 The row corresponding to the first node s and the column corresponding to the power node i. Second submatrix It is a D×N matrix. The elements in the matrix only include the inverse matrix A. -1 The column corresponding to the first node s in the middle. The elements in the equation represent the power allocation coefficients from the power supply nodes to the transmission lines. The elements in the equation represent the power distribution coefficients from transmission lines to load nodes. The elements in the equation are the power allocation coefficients from the power supply node to the load node.

[0065] The elements in the power order allocation matrix A can be calculated using the following formula:

[0066] (5)

[0067] in, , Assign elements in matrix A to power order.

[0068] According to formulas (1)-(5), the power flow betweenness can be expressed as:

[0069] (6)

[0070] Simplifying formula (6), we can obtain a simplified expression for the power flow betweenness:

[0071] (7)

[0072] Calculation using the trend tracking method and hour, , And A -1 The power flow betweenness factor changes with the operating state of the power system, i.e., the power of the power source nodes and the power of the load nodes change. If the power flow betweenness factor is calculated according to formula (7), a new value needs to be obtained through power flow calculation and power flow tracing calculation every time the operating state of the power system changes. , And A -1 Then, substitute the result into formula (7) to update the power flow betweenness. Repeated iterative power flow calculations and complex power flow tracking calculations limit the efficiency of power flow betweenness calculation. To improve the efficiency of power flow betweenness calculation, see [reference needed]. Figure 2 The identification method provided in some embodiments of this application includes:

[0073] S100: Calculates the branching coefficients of the power grid topology.

[0074] The branch branch coefficient is the power change on any transmission line st when the power of a transmission node changes. Calculating the branch branch coefficient of a power grid topology includes obtaining the node impedance matrix of the topology and calculating the branch branch coefficient based on the elements in the node impedance matrix. This application's embodiments, starting from the physical meaning of the power system node impedance matrix, define a correlation matrix between the power of transmission nodes and the power of transmission lines to improve the power flow betweenness coefficient. This avoids complex power flow tracing calculations, thereby improving the computational efficiency of the power flow betweenness coefficient.

[0075] The values ​​of the elements in the node impedance matrix are equal to the voltage values ​​of another transmission node when unit power is injected into any transmission node. The node impedance matrix can be obtained by taking the inverse of the node admittance matrix; this process is prior art and will not be described in detail here. The reactance of transmission lines in a power grid is much greater than their resistance. When the resistance of the transmission lines is ignored (this is a commonly accepted assumption in power systems), and assuming any transmission node n is a transmission node on transmission line st, then when unit power is injected into transmission node n, the voltage difference between the beginning and end of any transmission line st is: ,in, To transmit the voltage at the first node of the line, For the voltage at the end node on the transmission line, then and The voltage value is equal to the value of the element in the node impedance matrix.

[0076] The impedance of transmission line st is At that time, the current flowing through the transmission line st is Assuming that the voltages at all nodes in the power grid are near their rated values ​​(this is a commonly accepted assumption in power systems), the current on transmission line st is directly proportional to the power transmitted by transmission line st. That is, when the power at transmission node n changes by a unit power, the power change on transmission line st is... Based on this, a first correlation matrix between transmission node power and transmission line power is defined. First correlation matrix The element in the d-th row and n-th column is , The branching coefficient is defined as the power change on the d-th transmission line when the power of transmission node n changes. In some embodiments, the branching coefficient can be calculated using the following formula:

[0077] (8)

[0078] Where d represents the transmission line, and n represents any transmission node on any transmission line other than transmission line d. Let be the branching coefficient of transmission line d. Let n be the voltage at the first node of transmission line d when unit power is injected at transmission node n. Let n be the voltage at the terminal node of transmission line d when unit power is injected at transmission node n. Let be the impedance of transmission line d. First correlation matrix. The first correlation matrix reflects the impact of power changes at transmission nodes on power changes in transmission lines. It is an N×N matrix.

[0079] S200: Calculate the transmission power of the transmission line and the node branch coefficient based on the branch branch coefficient, and calculate the total injected power of the head node based on the node branch coefficient.

[0080] The node branching coefficient is the power change of one transmission node when the power of another transmission node changes. Considering only the power changes of power node i and load node j, the transmission power of transmission line st can be obtained by superimposing the effects of the power changes of power node i and load node j:

[0081] (9)

[0082] definition and These are the power column vectors for the power supply nodes and the power column vectors for the load nodes, respectively. This can be understood as... and Both are N-dimensional column vectors. In China and Africa, the power node element is 0, and the power node element represents the power node power. Each node element represents the load node power. By superimposing the effects of power changes at both the power supply and load nodes on the power change of transmission line st, we can obtain the transmission power of transmission line st under the influence of power and load node changes. The transmission power can be expressed as:

[0083] (10)

[0084] in, Let be the row vector of the branch coefficients, which is also the first incidence matrix. The element in the d-th row corresponds to the d-th transmission line st. This is the power column vector of the power nodes. This is the column vector of load node power.

[0085] For ease of calculation, in the first correlation matrix Based on this, a second correlation matrix Q is defined to represent the degree of power change of the c transmission lines connected to transmission node k when the power of transmission node n changes. The element Q(k,n) in the second correlation matrix Q represents the degree of power change of transmission node k when the power of transmission node n changes, i.e., the node branch coefficient. According to Kirchhoff's laws, the power of transmission node k is the sum of the power of the c transmission lines connected to transmission node k. In some embodiments, the node branch coefficient can be calculated using the following formula:

[0086] (11)

[0087] in, Let be the node branching coefficient of transmission node k when the power of transmission node n changes, and C be the set of transmission lines. The branch coefficients of the c transmission lines connected to transmission node k are given by the element The resulting matrix is ​​a submatrix of the first incidence matrix T, and is a c×1 matrix. The second incidence matrix Q is a D×N matrix.

[0088] Given that the power supply and load power are known. When the second correlation matrix Q is in its s-th row, The power injected into the transmission line at the starting node s is thus the total injected power at the starting node s (the sum of the power injected into the transmission line and the power supplied by the power source) can be expressed as:

[0089] (12)

[0090] in, For total injected power, The row vector represents the branch coefficients of the nodes.

[0091] S300: Obtain the power order allocation matrix and the inverse of the power order allocation matrix of the topology based on the transmission power and the total injected power.

[0092] Based on the above formulas (10), (12), and (5), the redefined power order allocation matrix A can be obtained. The elements in the power order allocation matrix A can be represented as:

[0093] (13)

[0094] in, The inverse matrix of the power order allocation matrix A can be calculated based on the elements in the power order allocation matrix A redefined in formula (13). This calculation process is available through existing technology and will not be described in detail in this application.

[0095] S400: Obtain the first, second, and third submatrices based on the inverse of the power order allocation matrix.

[0096] As described in the above embodiments, the elements in the first submatrix are the power allocation coefficients for the total injected power distributed from the power supply node to the transmission line, the elements in the second submatrix are the power allocation coefficients for the total injected power distributed from the transmission line to the load node, and the elements in the third submatrix are the power allocation coefficients for the total injected power distributed from the power supply node to the load node. The first, second, and third submatrixes obtained from the inverse of the power order allocation matrix are respectively... , , ,in, It is a D×M order matrix. It is a D×N matrix. The matrix is ​​of order M×N. The elements of the first, second, and third submatrices have been described in the above embodiments and will not be repeated in this step.

[0097] S500: Calculates the power flow betweenness of the transmission line based on the transmitted power, total injected power, first submatrix, second submatrix, and third submatrix, in order to identify vulnerable lines based on the power flow betweenness. The power flow betweenness is used to assess the vulnerability of the transmission line.

[0098] Substituting formulas (10), (12), and (13) into formula (7), we can obtain the improved form of the power flow betweenness. The expression for the improved power flow betweenness is:

[0099] (14)

[0100] in, Let be the element in the s-th row and i-th column of the first submatrix. Let be the element in the s-th row and j-th column of the second submatrix. Let be the element in the i-th row and j-th column of the third submatrix.

[0101] In the improved expression for the power flow betweenness of formula (14), only the column vectors... and Power of power nodes in and load node power One is a variable, and the other parameters are constants. and When the power changes, it can be directly substituted into formula (14) for calculation, and the power of the power node can be calculated. and load node power No power flow calculation is required. The identification method provided in this application overcomes the weakness of existing methods based on power flow betweenness and other vulnerable line identification methods, which rely on the results of power grid power flow calculation. When the operating state of the power system changes, only the power of the power nodes needs to be updated. and load node power This eliminates the need for iterative power flow calculations and improves the efficiency of vulnerable line identification.

[0102] To improve the stability and interpretability of the evaluation results, the power flow betweenness number can be normalized. In some embodiments, identifying vulnerable lines based on the power flow betweenness number includes:

[0103] The power flow betweenness is normalized to obtain normalized data; the normalized data is sorted, and a predetermined number of transmission lines at the top of the sort are identified as vulnerable lines.

[0104] The power flow betweenness can be normalized using the following formula:

[0105] ;

[0106] in, To normalize the data, This represents the maximum vulnerability of the transmission line. This represents the minimum vulnerability of the transmission line.

[0107] See Figure 3 , Figure 3 In the diagram, l1-l6 are transmission lines, p1-p5 are transmission nodes, and G1-G4 are power supply nodes. Figure 3 Taking the power grid system as an example, the identification method of this application is used to identify vulnerable lines. The parameters of the power grid system are shown in Tables 1-2:

[0108] Table 1: Transmission Line Parameters of a 5-Node Power Grid System

[0109]

[0110] Table 2: Transmission Node Parameters of a 5-Node Power Grid System

[0111]

[0112] Table 3: Vulnerability of Transmission Lines in 5-Node Power Grid Systems

[0113]

[0114] The vulnerability of the transmission lines identified by the identification method of this application is shown in Table 3. According to the vulnerability ranking in Table 3, transmission line l5 is a vulnerable line.

[0115] Based on the above method, some embodiments of this application also provide a power grid vulnerable line identification system based on power flow betweenness, applied to the method provided in the above embodiments, see [link to relevant documentation]. Figure 4 The system includes:

[0116] First calculation module: used to calculate the branch coefficients of the power grid topology.

[0117] The topology includes power nodes, load nodes, transmission nodes, and at least one transmission line. Power nodes are connected to load nodes through transmission lines. Transmission nodes are nodes on the transmission lines and include head nodes and tail nodes. The branch coefficient is the amount of power change on any transmission line when the power of the transmission node changes.

[0118] The second calculation module is used to calculate the transmission power of the transmission line and the node branch coefficient based on the branch branch coefficient, so as to calculate the total injected power of the head node based on the node branch coefficient.

[0119] The node branch coefficient is the power change of one transmission node when the power of another transmission node changes.

[0120] The third calculation module is used to obtain the power order allocation matrix and the inverse of the power order allocation matrix of the topology based on the transmission power and the total injected power.

[0121] The elements in the power order allocation matrix are the allocation coefficients of the total injected power on the transmission line.

[0122] The fourth calculation module is used to obtain the first, second, and third sub-matrices based on the inverse of the power order allocation matrix.

[0123] The elements in the first submatrix are the power allocation coefficients for the total injected power distributed from the power supply node to the transmission line, the elements in the second submatrix are the power allocation coefficients for the total injected power distributed from the transmission line to the load node, and the elements in the third submatrix are the power allocation coefficients for the total injected power distributed from the power supply node to the load node.

[0124] The identification calculation module is used to calculate the power flow betweenness of the transmission line based on the transmitted power, total injected power, first submatrix, second submatrix, and third submatrix, in order to identify vulnerable lines based on the power flow betweenness. The power flow betweenness is used to assess the vulnerability of the transmission line.

[0125] As can be seen from the above technical solutions, the embodiments of this application provide a method and system for identifying vulnerable power grid lines based on power flow betweenness. The method includes: calculating the branch branch coefficients of the power grid topology; calculating the transmission power and node branch coefficients of the transmission lines based on the branch branch coefficients, and calculating the total injected power of the head node based on the node branch coefficients; obtaining the power order allocation matrix and the inverse matrix of the power order allocation matrix of the topology based on the transmission power and the total injected power; obtaining the first sub-matrix, the second sub-matrix, and the third sub-matrix based on the inverse matrix of the power order allocation matrix; calculating the power flow betweenness of the transmission lines based on the transmission power, the total injected power, the first sub-matrix, the second sub-matrix, and the third sub-matrix, and identifying vulnerable lines based on the power flow betweenness. The method does not rely on the results of power flow calculation. When the operating state of the power system changes, it is only necessary to update the power of the power source nodes and the power of the load nodes, without the need for repeated iterative power flow calculations, which can improve the efficiency of vulnerable line identification.

[0126] Similar parts between the embodiments provided in this application can be referred to mutually. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods extended from the solution of this application without creative effort shall fall within the scope of protection of this application.

Claims

1. A method for identifying vulnerable power grid lines based on power flow betweenness, characterized in that, include: Calculate the branching coefficients of the power grid topology; The topology includes a power node, a load node, a transmission node, and at least one transmission line. The power node is connected to the load node through the transmission line. The transmission node is a node on the transmission line and includes a head node and an end node. The branch coefficient is the amount of power change on any transmission line when the power of the transmission node changes. The transmission power and node branch coefficient of the transmission line are calculated based on the branch branch coefficient, and the total injected power of the first node is calculated based on the node branch coefficient. The node branch coefficient is the amount of power change of one of the transmission nodes when the power of one of the transmission nodes changes; The power order allocation matrix of the topology and the inverse matrix of the power order allocation matrix are obtained based on the transmission power and the total injected power, and the elements in the power order allocation matrix are the allocation coefficients of the total injected power on the transmission line; The first submatrix, the second submatrix, and the third submatrix are obtained by inverse matrix of the power order allocation matrix; the elements in the first submatrix are the power allocation coefficients for the total injected power allocated from the power node to the transmission line, the elements in the second submatrix are the power allocation coefficients for the total injected power allocated from the transmission line to the load node, and the elements in the third submatrix are the power allocation coefficients for the total injected power allocated from the power node to the load node. The power flow betweenness of the transmission line is calculated based on the transmission power, the total injected power, the first submatrix, the second submatrix, and the third submatrix, in order to identify vulnerable lines based on the power flow betweenness, which is used to assess the vulnerability of the transmission line. The branch branch coefficients for calculating the power grid topology include: Obtain the node impedance matrix of the topology, and calculate the branch coefficient based on the elements in the node impedance matrix; the value of each element in the node impedance matrix is ​​equal to the voltage value of another transmission node when unit power is injected into any transmission node. The branch coefficient is calculated using the following formula: ； Where d represents the transmission line, and n represents any transmission node on any transmission line other than transmission line d. Let be the branching coefficient of transmission line d. Let n be the voltage at the first node of transmission line d when unit power is injected at transmission node n. Let n be the voltage at the terminal node of transmission line d when unit power is injected at transmission node n. and The voltage values ​​are equal to the values ​​of the elements in the node impedance matrix. Let d be the impedance of the transmission line; The transmission power is calculated using the following formula: ； in, For transmission power, Let be the row vector of branch coefficients. This is the power column vector of the power nodes. This is the column vector of load node power; The node branch coefficient is calculated using the following formula: ； in, Let be the node branching coefficient of transmission node k when the power of transmission node n changes, and C be the set of transmission lines. The branching coefficients of the c transmission lines connected to transmission node k; The total injected power is calculated using the following formula: ； in, For total injected power, The row vector represents the branch coefficients of the nodes; The elements in the power order allocation matrix are calculated using the following formula: ； in, The elements in the power order assignment matrix are used, where s is the first node of the transmission line and t is the last node of the transmission line. The first submatrix, the second submatrix, and the third submatrix are submatrices of the inverse matrix of the power order allocation matrix; The power flow betweenness of the transmission line is calculated using the following formula: ； in, Let G be the power flow betweenness, L be the set of power supply nodes, and i be the set of load nodes; j be the power supply node and j be the load node. This refers to the power capacity of the power node. For the load capacity of the load node, This represents the minimum value of both the power supply capacity and the load capacity. Let be the element in the s-th row and i-th column of the first submatrix. Let be the element in the s-th row and j-th column of the second submatrix. Let be the element in the i-th row and j-th column of the third submatrix.

2. The method for identifying vulnerable power grid lines based on power flow betweenness as described in claim 1, characterized in that, The step of identifying vulnerable lines based on the power flow betweenness includes: The power flow betweenness is normalized to obtain normalized data; The normalized data is sorted, and a predetermined number of transmission lines that rank highest are identified as vulnerable lines.

3. The method for identifying vulnerable power grid lines based on power flow betweenness as described in claim 2, characterized in that, The power flow betweenness is normalized using the following formula: ； in, To normalize the data, This represents the maximum vulnerability of the transmission line. This represents the minimum vulnerability of the transmission line.

4. A power grid vulnerable line identification system based on power flow betweenness, characterized in that, The system applied to the power grid vulnerable line identification method based on power flow betweenness factor as described in any one of claims 1-3, the system comprising: First calculation module: used to calculate the branching coefficient of the power grid topology; the topology includes power generation nodes, load nodes, transmission nodes and at least one transmission line, the power generation nodes are connected to the load nodes through the transmission lines, the transmission nodes are nodes on the transmission lines, the transmission nodes include head nodes and tail nodes, and the branching coefficient is the amount of power change on any transmission line when the power of the transmission node changes. The second calculation module is used to calculate the transmission power and node branch coefficient of the transmission line based on the branch branch coefficient, so as to calculate the total injected power of the first node based on the node branch coefficient; the node branch coefficient is the power change of the other transmission node when the power of one of the transmission nodes changes. The third calculation module is used to obtain the power order allocation matrix of the topology and the inverse matrix of the power order allocation matrix based on the transmission power and the total injected power, wherein the elements in the power order allocation matrix are the allocation coefficients of the total injected power on the transmission line; The fourth calculation module is used to obtain a first submatrix, a second submatrix, and a third submatrix based on the inverse of the power order allocation matrix; the elements in the first submatrix are the power allocation coefficients for the total injected power allocated from the power supply node to the transmission line, the elements in the second submatrix are the power allocation coefficients for the total injected power allocated from the transmission line to the load node, and the elements in the third submatrix are the power allocation coefficients for the total injected power allocated from the power supply node to the load node. Identification Calculation Module: Used to calculate the power flow betweenness of the transmission line based on the transmission power, the total injected power, the first sub-matrix, the second sub-matrix, and the third sub-matrix, so as to identify vulnerable lines based on the power flow betweenness, which is used to evaluate the vulnerability of the transmission line.

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