A cut-set critical transmission section search method for power grid based on cut-set section tree

Abstract

The embodiment of the present invention discloses a method for searching for cut-set key transmission sections of a power grid based on a cut-set section tree, comprising: obtaining power grid network topology data, extracting and deleting bridge lines in the power grid network topology data, and obtaining the remaining multiple non-bridge lines; sequentially obtaining the branch disconnection distribution factors between any two non-bridge lines, determining the flow transfer correlation of the two non-bridge lines based on the branch disconnection distribution factors, and constructing a section composition relationship matrix according to the flow transfer correlation between the non-bridge lines; constructing a cut-set section search tree based on the section composition relationship matrix, and searching and verifying to obtain a set of cut-set key transmission sections. This method can obtain a transmission section that meets the cut-set characteristics of the power grid by constructing a section composition relationship matrix and generating a cut-set section tree according to the section composition relationship matrix; without repeated iteration, a cut-set type transmission section with a relatively close flow transfer correlation can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid static stability analysis and identification, and in particular to a power grid cut-set type key transmission section search method based on a cut-set section tree. Background Art

[0002] The key transmission section of the power grid is responsible for the power transmission between two areas of the power grid. When a line in a key transmission section fails, the power flow will be transferred to the line in the key transmission section in large quantities, causing heavy overloads on the remaining lines in the section. Therefore, in the dispatching and operation of the power grid, it is necessary to search and monitor the key transmission sections. With the construction of new power systems, the uncertainty of new energy will lead to frequent changes in power grid power flow, an increase in the number of key transmission sections, and the search results of key transmission sections are also greatly affected by the output of new energy. Therefore, realizing fast and accurate pre-search of key transmission sections is conducive to dispatching to take corresponding control measures in time to ensure the power supply reliability of the power grid.

[0003] The existing key transmission section search technology generally uses clustering methods to partition the nodes in the power grid, and then selects the transmission line cut sets with consistent flow direction in the partition interconnection lines to form candidate transmission sections. Finally, after heavy overload verification, the key transmission sections are screened. This type of method requires multiple iterations and matrix operations on a large amount of data during the partition process, which has a high time cost. At the same time, the partition quality has a great influence on the search effect. When the partition is small, there are more partition interconnection lines, and the search calculation amount of the key transmission section is large; when the partition is large, it is easy to miss the heavy overload lines inside the partition; therefore, this clustering method has problems such as low recognition accuracy and low efficiency. Summary of the invention

[0004] In view of this, the present invention proposes a power grid cut set type key transmission section search method based on a cut set section tree, which is used to solve the problem of low recognition accuracy and low efficiency of existing section identification methods. In order to achieve one or part or all of the above purposes or other purposes, the present invention proposes a power grid cut set type key transmission section search method based on a cut set section tree, comprising:

[0005] Acquire power grid network topology data, extract and delete bridge lines in the power grid network topology data, and obtain the remaining multiple non-bridge lines;

[0006] Sequentially obtain the branch breaking distribution factors between any two non-bridge lines, determine the power flow transfer correlation of the two non-bridge lines based on the branch breaking distribution factors, and construct a section composition relationship matrix according to the power flow transfer correlation between the non-bridge lines;

[0007] A cut set section search tree is established based on the section composition relationship matrix, a first cut set type critical transmission section set is obtained by searching, and a heavy overload check is performed on the first cut set type critical transmission section set to obtain a second cut set type critical transmission section set.

[0008] According to a specific implementation, in the above-mentioned power grid cut-set type key transmission section search method based on the cut-set section tree: the extracting and deleting the bridge line in the power grid topology data includes:

[0009] Describing the power grid network topology data as a topology structure graph;

[0010] Traversing each edge in the topology graph in turn, and determining whether the topology graph loses connectivity after deleting the edge; if so, the edge is a bridge line in the topology graph, and if not, the edge is not a bridge line in the topology graph;

[0011] The bridge lines in the topology diagram are extracted and deleted to obtain the remaining multiple non-bridge lines.

[0012] According to a specific implementation, in the above-mentioned power grid cut-set type key transmission section search method based on the cut-set section tree: the number of rows and columns of the section constituting the relationship matrix is ​​equal to the total number of the remaining multiple non-bridge lines;

[0013] The step of constructing a section formation relationship matrix according to the power flow transfer correlation between the non-bridge lines includes:

[0014] It is determined in turn whether the power flow directions of any two non-bridge lines are consistent. If not, the elements corresponding to the two lines are recorded as the first value; if so, it is determined whether the power flow transfer correlation of the two non-bridge lines is correlated. If not, the elements corresponding to the two lines are recorded as the first value; if so, the elements corresponding to the two non-bridge lines are recorded as the second value;

[0015] The cross-section formation relationship matrix is ​​determined according to the corresponding element values ​​between the non-bridge lines.

[0016] According to a specific implementation, in the above-mentioned power grid cut-set type key transmission section search method based on the cut-set section tree: based on the shortest path search method, it is determined whether the power flow directions of any two non-bridge lines are consistent.

[0017] According to a specific implementation, in the above-mentioned power grid cut-set type key transmission section search method based on the cut-set section tree: the flow transfer correlation of two non-bridge lines is determined based on the branch disconnection distribution factor, including:

[0018] It is determined whether the branch disconnection distribution factor exceeds the correlation threshold. If so, it is considered that the power flow transfer correlation of the two non-bridge lines is related; if not, it is considered that the two non-bridge lines are unrelated.

[0019] According to a specific implementation, in the above-mentioned power grid cut-set type key transmission section search method based on the cut-set section tree: the branch disconnection distribution factor between the plurality of non-bridge lines is obtained by the following formula:

[0020]

[0021]

[0022]

[0023] Where D ij represents the branch disconnection distribution factor of line j after line i is disconnected, and its value range is [-1,1]; where X ij represents the mutual impedance between the node pair where the line i is located and the node pair where the line j is located; X ii represents the self-impedance between the port nodes where line i is located; x i and x j are the reactances of line i and line j respectively; M i and M j is a column vector, representing the node-line association vector of line i and line j, that is, the elements at the head node and the end node of the line are +1 and -1 respectively, and the elements at other positions are 0; X is the reactance matrix of the power grid, which is the inverse of the susceptance matrix B.

[0024] According to a specific implementation, in the above-mentioned power grid cut set type key transmission section search method based on the cut set section tree: the cut set section search tree is established based on the section composition relationship matrix, and the cut set type key transmission section set is searched, including:

[0025] S301, select any non-bridge line s as the root node, and the remaining non-bridge lines as leaf nodes; let the number of non-bridge lines be n, initialize the set of branches to be grown {s, e1}, {s, e2}, … {s, e n}; Set the maximum search depth h max , start searching for the cross section;

[0026] S302: any leaf node e of the growing branch set i , perform branch growth search: search for e in the cross-section composition relationship matrix i The corresponding row; the line corresponding to the column number of all the second numerical elements in the row is taken as the leaf node e i The next level leaf node, assuming that there are k leaf nodes in the next level, denoted by ei,1 ,e i,2 …,e i,k ; Add each candidate leaf node to the end of the current branch to form a new candidate branch, and then expand the set of branches to be grown into a new set of branches:

[0027] S303, screening the new branch set based on a preset screening method, constructing a new branch set based on the screened branches, performing a cut set detection on the branches in the new branch set, and if the branch passes the cut set detection, adding it to the cut set type key transmission section set; if not, adding the branch to the set of branches to be grown;

[0028] S304, repeating steps S302 to S303 for the updated set of branches to be grown, until the search of the search tree is stopped when the termination condition is met, and obtaining the cut-set type key transmission section set.

[0029] According to a specific implementation, in the above-mentioned power grid cut-set type key transmission section search method based on the cut-set section tree: the preset screening method includes: repeatability detection and power flow direction detection.

[0030] According to a specific implementation, in the above-mentioned power grid cut set type critical transmission section search method based on the cut set section tree: the heavy overload check of the first cut set type critical transmission section set includes: sequentially performing section risk checks on the lines in the section line set, and calculating the section risk coefficient of the line compared with the remaining lines; based on the obtained section risk coefficient, non-critical sections are screened and non-critical sections in the cut set type critical transmission section set are eliminated.

[0031] According to a specific implementation, in the above-mentioned power grid cut-set type key transmission section search method based on the cut-set section tree: the section risk coefficient is calculated by the following formula:

[0032]

[0033] Among them, Rs is the cross-section risk coefficient, P i and P j are respectively the active current of line i and line j in the initial state, P j·max is the active transmission capacity of line j.

[0034] Implementing the embodiments of the present invention will have the following beneficial effects:

[0035] The critical transmission section search method based on the cut set section tree provided in the embodiment of the present invention defines a section composition relationship matrix, constructs the section composition relationship matrix based on the flow correlation, and generates a cut set section tree according to the section composition relationship matrix. The cut set type critical section can be obtained by searching the cut set section tree; each branch in the generated cut set section tree corresponds to a group of sections that meet the cut set characteristics of the power grid, and after the search, the section set obtained by the search is further corrected by heavy overload verification, so as to further ensure the search accuracy of the critical section. The method is based on the section composition relationship matrix, does not require matrix operations, and has high search efficiency; does not require repeated iterations, and the lines in the obtained cut set type transmission section have relatively close flow transfer correlations. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] in:

[0038] Figure 1 It is a schematic flow chart of a method for searching a cut-set key transmission section of a power grid based on a cut-set section tree in one embodiment;

[0039] Figure 2 It is a schematic flow chart of a method for searching a cut-set key transmission section of a power grid based on a cut-set section tree in one embodiment;

[0040] Figure 3 A topological structure diagram of an IEEE 9-node system in one embodiment;

[0041] Figure 4 A schematic diagram of a method for determining the consistency of power flow direction of a non-bridge line in one embodiment;

[0042] Figure 5 A flow chart of a cut set section tree search based on a section-construction relationship matrix in one embodiment;

[0043] Figure 6 Schematic diagram of a cut set section tree of an IEEE 9-node system in an embodiment. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] Figure 1 A method for searching for key transmission sections of a power grid based on a cut-set section tree according to an exemplary embodiment of the present invention is shown, comprising:

[0047] Acquire power grid network topology data, extract and delete bridge lines in the power grid network topology data, and obtain the remaining multiple non-bridge lines;

[0048] Sequentially obtain the branch breaking distribution factors between any two non-bridge lines, determine the power flow transfer correlation of the two non-bridge lines based on the branch breaking distribution factors, and construct a section composition relationship matrix according to the power flow transfer correlation between the non-bridge lines;

[0049] A cut set section search tree is established based on the section composition relationship matrix, a first cut set type critical transmission section set is obtained by searching, and a heavy overload check is performed on the first cut set type critical transmission section set to obtain a second cut set type critical transmission section set.

[0050] In this embodiment, by defining a section composition relationship matrix, constructing a section composition relationship matrix based on flow correlation, and generating a cut set section tree based on the section composition relationship matrix, the cut set type key section can be obtained by searching the cut set section tree; each branch in the generated cut set section tree corresponds to a group that meets the cut set characteristics of the power grid, and after the search, the section set obtained by the search is further corrected through a heavy overload check to further ensure the search accuracy of the key section. This method is based on the section composition relationship matrix, does not require matrix operations, and has high search efficiency; no repeated iteration is required, and the lines in the obtained cut set type transmission section have a relatively close flow transfer correlation.

[0051] Example 2

[0052] In a possible implementation, in the above-mentioned power grid cut-set type key transmission section search method based on the cut-set section tree, as Figure 2 As shown, the S1 specifically includes:

[0053] The topology of the power grid is described as a topology graph. In the topology graph G, if deleting an edge will cause the graph to lose connectivity, then the edge is called a bridge of the graph G.

[0054] The bridge search steps of the power grid topology diagram are as follows:

[0055] S101. Select an edge in the graph in turn.

[0056] S102: Delete the edge from the graph and perform connectivity check on the graph.

[0057] S103. If the graph loses connectivity, then the edge is a bridge of the graph; otherwise, it is not a bridge.

[0058] S104, the bridge line can be directly added to the key section set KS of the power grid, forming a key transmission section in KS.

[0059] S105, delete all bridge branches to form mutually disconnected subgraphs GS j . Subsequently, the key sections consisting of non-bridge lines are searched in each subgraph.

[0060] by Figure 3 Take the 9-node power grid as an example, edges 7, 8, and 9 are all bridges in the graph. After deleting the bridge, lines 1-6 form the sub-non-bridge line graph of the power grid.

[0061] In a possible implementation, in the above-mentioned power grid cut-set type key transmission section search method based on the cut-set section tree, S2 specifically includes:

[0062] S21. Construct a line correlation matrix based on the branch disconnection distribution factors between the lines.

[0063] The line correlation matrix S is a square matrix composed of 0 / 1 elements, and the number of rows and columns is equal to the total number of lines in the diagram. The element value calculation formula is as follows:

[0064] Calculate the branch disconnection distribution factor D between lines ij . Set the correlation threshold S0, then the element S in the correlation matrix S ij The calculation is shown below.

[0065]

[0066] In the formula, S ij It indicates the correlation of power flow transfer of line i to line j. Zero indicates no correlation. S0 is the correlation threshold, which is usually taken as 0.2-0.3. ij It is a commonly used indicator, and the calculation formula is as follows:

[0067]

[0068]

[0069]

[0070] In the formula, D ij represents the branch outage distribution factor of line j after line i is disconnected, and its value range is [-1, 1]; in the formula, X ij represents the mutual impedance between the port where line i is located and the node pair of the port where line j is located; X ii represents the self-impedance between the port nodes where line i is located; x i and x j are the reactances of line i and line j respectively; M i and M j are column vectors, representing the node-line incidence vectors of line i and line j respectively, that is, the elements at the head node and tail node positions of the line are +1 and -1 respectively, and the elements at the remaining positions are 0; X is the reactance matrix of the power grid, which is the inverse of the susceptance matrix B.

[0071] S22. Generate the line section composition relationship matrix TS according to the S matrix.

[0072] TS is a square matrix composed of the first numerical element or the second numerical element, and its number of rows and columns is also equal to the total number of lines in the figure. In this implementation, to maximize the simplification of the matrix, the first numerical value is taken as 0 and the second numerical value is taken as 1.

[0073] Among them, the assignment method of each element in TS is as follows.

[0074]

[0075] That is, for each element in S that is 1, if the power flow directions of the two lines represented by its row and column numbers are the same, it is considered that the two lines have the same power flow direction, that is, the corresponding element in TS is 1.

[0076] Among them, the method for judging whether the power flow directions of any two lines l1 and l2 are the same is as follows:

[0077] As Figure 4 shown, denote the two end nodes of line l1 as a and b, and the two end nodes of line l2 as u and v. The current active power flow directions of line l1 and l2 are known. Without loss of generality, assume it is from node a → b and node u → v.

[0078] Perform the shortest path search: Take the line reactance as the edge weight, and use the Dijkstra algorithm to search for the shortest electrical distances d1 between (a, u), d2 between (b, v), d3 between (a, v), and d4 between (b, u) respectively.

[0079] If d1 + d2 < d3 + d4, the power flow directions of line l1 and l2 are the same; otherwise, the power flow directions are different.

[0080] Still taking Figure 3 For example, in the subgraph consisting of lines 1-6, the element S of the line correlation matrix under a certain power flow distribution is 13 =1, that is, the branch disconnection distribution factor of line 1 to line 3 is greater than the correlation threshold. After the flow direction check, the flow directions of the two lines are consistent, so the section constitutes the TS in the relationship matrix 1,3 =1. The following is the TS matrix under this power flow mode:

[0081]

[0082] In a possible implementation, in the above-mentioned power grid cut-set key transmission section search method based on the cut-set section tree, the above-mentioned S3 constructs a cut-set section tree according to the section composition relationship matrix TS to search for the cut-set transmission section. Figure 5 As shown in the figure, the construction method of the cut set section tree is as follows:

[0083] S301, set a virtual node s as the root node, and set all the lines as the first-level leaf nodes. Let the number of lines be n, and initialize the current branch set {s, e1}, {s, e2}, … {s, e n}. Set the maximum search depth h max , start searching for the section.

[0084] S302: For the last leaf node e in each branch i , start the branch growth search:

[0085] S3021, search for e in the cross-section composition relationship matrix TS i The corresponding row. The line corresponding to the column number of all non-zero elements in the row is taken as node e i The next level candidate leaf node, assuming that there are k candidate leaf nodes, denoted by e i,1 ,e i,2 …,e i,k .

[0086] S3022, adding each candidate leaf node to the end of the current branch to form a new candidate branch, that is, the original branch {s,…,e i} is expanded into k new candidate branches: s,…,e i ,e i,1}{s,…,e i ,e i,2}…{s,…,e i ,e i,k}strip.

[0087] S3023, screening the candidate branches based on a preset screening method to determine whether to add the candidate branches to the search tree; wherein the preset screening method includes:

[0088] a. Repeatability detection. To avoid duplication of branches, determine whether the line set of the candidate branch is the same as the branch that has been searched. If not, record the detection result F a =1, otherwise 0.

[0089] b. Flow direction detection. Check whether all lines in the candidate branches have flow direction consistency. If so, record the judgment result F b =1, otherwise 0.

[0090] c. When F a and F b When the results are all 1, the candidate branch is added to the branch set and marked as a newly grown branch, and the original branch is deleted from the branch set accordingly. Otherwise, the candidate branch fails the screening.

[0091] d. If all candidate branches fail to pass the screening, the branch is considered to have finished growing.

[0092] S303, perform cut set detection on the newly grown branches. The detection method is: delete all lines in the branches in the power grid topology diagram. If the power grid loses connectivity, it means that the branch constitutes a cut set of the power grid, add it to the cut set type transmission section, and stop the growth of the branch.

[0093] S304: Repeat steps S302 to S303 for the newly grown branches until any one of the following two termination criteria is met, and stop searching the search tree. The termination criteria are: 1) there is no candidate node that meets the requirements; 2) all leaf nodes have reached the maximum search depth to depth h.

[0094] Further, Figure 3 As an example of the 9-node power grid topology shown in the figure, the cut set section tree result under a given power flow is as follows Figure 6 The construction process of the cut set section tree is as follows:

[0095] For the branch {s,1}, according to the TS matrix obtained by S2 above, the corresponding position elements of lines 2, 3, and 6 are 1, and they are used as candidate leaf nodes. At this time, the candidate branches {s,1,2}, {s,1,3}, and {s,1,6} have all passed the screening, and b is added to the cut set section tree. It is determined that the three groups of branches constitute the cut set of the power grid, and they are added as the cut set type transmission section set.

[0096] For the branch {s,2}, according to the TS matrix, the corresponding position elements of lines 1, 4, and 5 are 1, and they are selected as candidate leaf nodes. Among the candidate branches {s,2,1}, {s,2,4}, and {s,2,5}, the branch {s,2,1} fails the repeatability test. The other two groups of branches meet the judgment requirements and are added to the cut set section tree. After the cut set test, they are all cut sets of the power grid. They are added as a cut set type transmission section set.

[0097] Repeat the above operations for branches {s,3}, {s,4}, {s,5}, {s,6} to finally obtain the cut set section tree result.

[0098] In a possible implementation, in the above-mentioned power grid cut-set type critical transmission section search method based on the cut-set section tree, the heavy overload check is performed on the first cut-set type critical transmission section set.

[0099] The heavy overload check includes:

[0100] The section risk of the lines in the section line set is checked in turn, and the section risk coefficient of the line compared with the other lines is calculated; non-critical sections are screened based on the obtained section risk coefficient, and the non-critical sections in the cut set type critical transmission section set are eliminated.

[0101] In this embodiment, non-critical sections in the cut-set critical transmission section set obtained by searching are eliminated through heavy overload verification, thereby further improving the accuracy of the identification result.

[0102] In a possible implementation, the heavy overload check includes:

[0103] The overload risk assessment is performed on each section line set in the cut-set type transmission section set. The method is to perform N-1 verification on each line in the section line set. The following risk coefficient is calculated:

[0104]

[0105] Where Rs is the cross-section risk coefficient, P i and P j are respectively the active current of line i and line j in the initial state, P j·max is the active transmission capacity of line j.

[0106] When Rs>1, it is considered that there is line overload in the section, and the section constitutes a critical transmission section with overload risk.

[0107] When Rs0≤Rs≤1, it is considered that there is line overload in the section, and the section constitutes a critical transmission section with overload risk, where Rs0 is the overload threshold, which is usually set to 0.8.

[0108] Otherwise, the section is not a critical transmission section.

[0109] Further, Figure 3 The IEEE9-node system illustrates the application process of the key transmission section search method based on the cut set section tree. The power flow distribution of each line under a certain operation mode is shown in Table 1.

[0110] Table 1 IEEE 9-node system power flow distribution

[0111]

[0112] (1) Determine the consistency of power flow direction between lines

[0113] According to the power flow direction of the line, the node electrical distance between the lines is calculated, and the power flow direction consistency detection result between the lines is obtained: the line pairs in Table 2 have power flow direction consistency, and other line pairs do not meet it.

[0114] Table 2 Line combinations with consistent flow direction

[0115]

[0116] (2) Generate line section composition relationship matrix

[0117] A search for bridges was conducted on the IEEE 9-node system, and lines 7, 8, and 9 were found to be bridges in the system. The bridges were directly added to the set of key transmission sections.

[0118] Set the correlation threshold to 0.2, calculate the power flow transfer correlation matrix S between lines, and the obtained S matrix result is shown in the following formula:

[0119]

[0120] Combined with the consistency judgment results of tidal flow direction in Table 2, the line section composition relationship matrix TS is constructed, as shown in the following formula.

[0121]

[0122] (3) Cut-set cross-section search

[0123] According to the line section relationship matrix TS, the cut set type section is searched based on the cut set search tree. The final cut set search tree is as follows Figure 6 shown.

[0124] From the cut set search tree, 9 cut set sections of the power grid can be obtained as shown in Table 3.

[0125] Table 3 Cut-set sections of power grid

[0126]

[0127] (4) Heavy overload verification of the section

[0128] The 9 groups of cut-set sections in Table 3 were subjected to heavy overload verification, and 4 groups of critical transmission sections were obtained, including 3 groups of critical sections with overload risk and 1 group of critical section with heavy load risk.

[0129] Table 4 Section heavy overload verification results

[0130]

[0131] After merging with the bridge section extracted by S1, the final results of the key sections of the power grid are shown in Table 5.

[0132] Table 5 Key section list

[0133]

[0134] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for searching key transmission sections of a power grid based on a cut-set section tree, characterized in that: include: Acquire power grid network topology data, extract and delete bridge lines in the power grid network topology data, and obtain the remaining multiple non-bridge lines; Sequentially obtain the branch breaking distribution factors between any two non-bridge lines, determine the power flow transfer correlation of the two non-bridge lines based on the branch breaking distribution factors, and construct a section composition relationship matrix according to the power flow transfer correlation between the non-bridge lines; A cut-set section search tree is established based on the section composition relationship matrix, a first cut-set type critical transmission section set is obtained by searching, and a heavy overload check is performed on the first cut-set type critical transmission section set to obtain a second cut-set type critical transmission section set; The number of rows and columns of the cross-section constituting relationship matrix is ​​equal to the total number of lines of the remaining plurality of non-bridge lines; The section formation relationship matrix is ​​constructed according to the correlation of power flow transfer between non-bridge lines, including: It is determined in turn whether the power flow directions of any two non-bridge lines are consistent. If not, the elements corresponding to the two lines are recorded as the first value; if so, it is determined whether the power flow transfer correlation of the two non-bridge lines is correlated. If not, the elements corresponding to the two lines are recorded as the first value; if so, the elements corresponding to the two non-bridge lines are recorded as the second value; Determine the cross-section composition relationship matrix according to the corresponding element values ​​between the non-bridge lines; The step of establishing a cut set section search tree based on the section composition relationship matrix, and searching to obtain a first cut set type key transmission section set, includes: S301, select any non-bridge line s as the root node, and the remaining non-bridge lines as leaf nodes; let the number of non-bridge lines be n, and initialize the set of branches to be grown ; Set the maximum search depth , start searching for the cross section; S302: any leaf node of the growing branch set , perform branch growth search: search in the cross-section relationship matrix The corresponding row; the line corresponding to the column number of all the second numerical elements in the row is taken as a leaf node The next level leaf node, assuming that the next level leaf nodes have , recorded as ; Add each candidate leaf node to the end of the current branch to form a new candidate branch, and then expand the set of branches to be grown into a new set of branches: S303, screening the new branch set based on a preset screening method, constructing a new branch set based on the screened branches, performing a cut set detection on the branches in the new branch set, and if the branch passes the cut set detection, adding it to the cut set type key transmission section set; if not, adding the branch to the set of branches to be grown; S304, repeating steps S302 to S303 for the updated set of branches to be grown, and stopping the search of the search tree when the termination condition is met, to obtain the first cut set type key transmission section set.

2. The method for searching for key transmission sections of a power grid based on a cut-set section tree according to claim 1, characterized in that: The extracting and deleting the bridge lines in the power grid network topology data includes: Describing the power grid network topology data as a topology structure graph; Traversing each edge in the topology graph in turn, and determining whether the topology graph loses connectivity after deleting the edge; if so, the edge is a bridge line in the topology graph, and if not, the edge is not a bridge line in the topology graph; The bridge lines in the topology diagram are extracted and deleted to obtain the remaining multiple non-bridge lines.

3. The method for searching for key transmission sections of a power grid based on a cut-set section tree according to claim 2, characterized in that: Based on the shortest path search method, it is determined whether the flow directions of any two non-bridge lines are consistent.

4. The cut-set type critical transmission section search method based on the cut-set section tree according to claim 3, characterized in that: The determining of the power flow transfer correlation of two non-bridge lines based on the branch disconnection distribution factor includes: It is determined whether the branch disconnection distribution factor exceeds the correlation threshold. If so, it is considered that the power flow transfer correlation of the two non-bridge lines is related; if not, it is considered that the two non-bridge lines are unrelated.

5. The method for searching for key transmission sections of a power grid based on a cut-set section tree according to claim 4, characterized in that: The branch disconnection distribution factor between the plurality of non-bridge lines is obtained by the following formula: In the formula, Indicates line After disconnection, The branch breaking distribution factor has a value range of ; In the formula Indicates line Port and line The mutual impedance between the port node pairs; Indicates line The self-impedance between the port nodes; and Line and lines Reactance; and are column vectors, representing the lines and lines The node-line association vector is a vector where the position elements at the beginning and end nodes of the line are +1 and -1 respectively, and the other position elements are 0; is the reactance matrix of the power grid, is the susceptance matrix The inverse of.

6. The method for searching for key transmission sections of a power grid based on a cut-set section tree according to claim 1, characterized in that: The preset screening method includes: repeatability detection and tidal flow direction detection.

7. The method for searching for key transmission sections of a power grid based on a cut-set section tree according to any one of claims 1 to 6, characterized in that: The heavy overload check on the first cut-set type critical transmission section set includes: performing section risk check on the lines in the section line set in turn, and calculating the section risk coefficient of the line compared with the remaining lines; screening out non-critical sections based on the obtained section risk coefficient, and eliminating the non-critical sections in the cut-set type critical transmission section set.

8. The method for searching for key transmission sections of a power grid based on a cut-set section tree according to claim 7, characterized in that: The cross-section risk factor is calculated by the following formula: in, is the cross-sectional risk factor, and Line and lines The active current in the initial state is For line Active transmission capacity, Indicates line After disconnection, The branch breaking distribution factor.

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