Coherent cluster division method and system based on slow coherence theory, terminal and medium

Abstract

The invention discloses a coherence cluster division method and system based on a slow coherence theory, a terminal and a medium, and relates to the technical field of power analysis, and the method is characterized in that a weak connection line of an AC / DC hybrid power grid is identified based on the slow coherence theory; classifying the grid-connected synchronous units according to the coupling degree of the off-line motor in the AC / DC hybrid power grid to obtain an off-line separation result; and taking the weak connection line as a splitting section pre-screening decision space, and providing a reference for splitting when the fault of the alternating current and direct current hybrid power grid occurs according to an off-line separation result of the grid-connected synchronous unit. According to the method, the applicability of the low-speed synchronization theory in the alternating-current and direct-current hybrid power grid is improved based on the time sequence characteristics of the power system.

Description

Technical Field

[0001] The present invention relates to the technical field of power analysis, and more specifically, to a method, system, terminal and medium for dividing a coherent machine group based on slow coherence theory. Background Art

[0002] AC / DC hybrid power grids are known for their high DC voltage ratio, large transmission capacity, and powerful operation control capabilities, which make the grid operation more flexible. However, this flexibility also means that it is more difficult to control the stability of the grid. Studies have shown that compared with pure AC power grids, AC / DC hybrid power grids are more vulnerable to collapse and are more likely to touch the stability boundary during operation. Even a small disturbance may cause instability in the entire system.

[0003] Regarding the grid stability margin, current research mainly focuses on the coupling effect between AC and DC systems. Some studies have shown that long-term uninterrupted commutation failures in DC systems will cause several commutation failures in the converter and DC line lockout. Therefore, the power difference generated in the AC systems on both sides will cause large-scale power flow transfer and fluctuations in the power system, which is specifically manifested as frequency instability and voltage instability in the power system. Some other studies have shown that the low local voltage caused by a certain fault in the AC system will cause the commutation device of the adjacent DC system to work abnormally, resulting in commutation failures and even DC lockout. The number and time of commutation failures in this type of DC system fault are related to the location and severity of the source fault in the AC system that caused the fault. Therefore, in order to cope with possible serious faults in the power system, when it is necessary to identify the synchronous group, special attention should be paid to the coupling effect between AC and DC systems on the basis of traditional identification methods.

[0004] When it comes to grid fault isolation, traditional isolation methods are mainly divided into active and passive methods. The research on these methods usually only considers pure AC systems, but does not take into account the particularity of AC / DC hybrid power grids. If DC lines are added to the existing AC grid, this will affect the structure of the grid, changing the system's oscillation mode, transient behavior, and the potential dynamics of the synchronous group of synchronous machines connected to the grid. Summary of the invention

[0005] In order to address the deficiencies in the prior art, the purpose of the present invention is to provide a method, system, terminal and medium for dividing a synchronous machine group based on the slow synchronous theory. The method relies on the time series characteristics of the power system to improve the applicability of the slow synchronization theory in the AC / DC hybrid power grid. By mathematically describing the power system with DC added, the slow synchronization theory of the AC / DC hybrid power grid is constructed, and the synchronous machine group division can be performed offline, thereby improving the identification accuracy of the offline synchronous machine group.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: In the first aspect, a method for partitioning a coherent cluster based on slow coherence theory is provided, comprising the following steps: Identify weakly connected lines in AC / DC hybrid power grids based on slow coherence theory; The grid-connected synchronous units are classified according to the coupling degree of offline motors in the AC / DC hybrid power grid, and the offline separation results are obtained; The weakly connected line is used as the pre-screening decision space for the disconnection section, and the offline separation results of the grid-connected synchronous units are used to provide a reference for disconnection when a fault occurs in the AC / DC hybrid power grid.

[0007] Furthermore, the process of identifying the weakly connected lines of the AC / DC hybrid power grid based on the slow coherence theory is specifically as follows: The AC / DC hybrid power grid is simplified into a linearized power system model, and the state matrix of the power system model is solved based on the slow coherence theory; The slow motion modal eigenvalues ​​are screened out from the state matrix to obtain a slow motion modal eigenvalue group; The degree of synchronization between synchronous generators is analyzed based on the cosine distance coefficient to pre-divide the synchronization of the grid-connected synchronous generators. The sensitivity of the slow-motion modal eigenvalue group to each transmission path is calculated, and the total number of slow-motion modal regions is determined in combination with the degree of coherence between the synchronous units, with the lines between the slow-motion modal regions being weakly connected lines.

[0008] Furthermore, the process of selecting the slow motion modal eigenvalue from the state matrix is ​​specifically as follows: Arrange the eigenvalues ​​in the state matrix in ascending order according to their absolute values ​​to obtain a first sequence; The ratio of adjacent eigenvalues ​​is calculated by the ratio between the previous eigenvalue and the next eigenvalue in the first sequence; Select the interval corresponding to the smallest ratio among all adjacent eigenvalue ratios as the dividing point; The eigenvalues ​​arranged before the division point are selected from the first sequence as the slow motion mode eigenvalues.

[0009] Furthermore, the process of analyzing the degree of synchronization between synchronous generators based on the cosine distance coefficient to pre-divide the synchronization of the grid-connected synchronous generators is specifically as follows: The cosine of the angle between the eigenvectors corresponding to the eigenvalues ​​of each slow motion mode is used to characterize the degree of synchronization between the synchronous units. If the degree of synchronization between two synchronous units is greater than a set threshold, the corresponding two synchronous units belong to the same synchronous unit group.

[0010] Furthermore, the expression for calculating the sensitivity of the slow motion modal eigenvalue group to each transmission path is specifically: ; in, Represents the slow motion modal eigenvalue group pair line Sensitivity; Indicates The slow motion modal eigenvalues ​​for the line Sensitivity; represents the number of slow motion modal eigenvalues ​​in the slow motion modal eigenvalue group; Indicates Slow motion modal eigenvalues; Indicates line Resistance; Indicates line Reactance; Indicates line The conductivity of Indicates line The electrical conductivity.

[0011] Furthermore, the process of determining the total number of slow motion modal regions in combination with the degree of synchronization between the synchronous units is specifically as follows: Disconnect all the lines and select the grid-connected synchronous machine node with the strongest power generation capacity in each area as the starting point; Only one area is selected each time, and the nodes with the lowest sensitivity of adjacent lines in the corresponding area are selected for inclusion; The selection process is repeated continuously. If, during the selection process, a node is included so that two areas are adjacent, the node is included in the area with lower connection line sensitivity, and the connection line connecting the node to the other area is cut off.

[0012] Calculate the equivalent power angle of the equivalent grid-connected synchronous machine node in the AC / DC hybrid power grid; An adjacency graph is constructed with equivalent grid-connected synchronous machine nodes in AC / DC hybrid power grid, and weight values ​​are assigned to the weighted graph in the adjacency graph based on the ratio of transmission power to the corresponding power angle difference, thus obtaining an improved Laplace matrix of coupling degree of grid-connected synchronous machines. Calculate the Federer vector according to the generalized characteristic formula; The clustering method is used to group the vector coordinates of each row in the Federer vector to obtain the offline classification results of the grid-connected synchronous units.

[0013] Secondly, a coherent cluster partitioning system based on slow coherence theory is provided, including: Line identification module, used to identify weakly connected lines in AC / DC hybrid power grids based on slow coherence theory; A coupling separation module is used to classify the grid-connected synchronous units according to the coupling degree of the offline motors in the AC / DC hybrid power grid and obtain offline separation results; The decoupling processing module is used to use the weakly connected line as the decoupling section pre-screening decision space, and provide a reference for decoupling when a fault occurs in the AC / DC hybrid power grid based on the offline separation result of the grid-connected synchronous unit.

[0014] In a third aspect, a computer terminal is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for dividing a coherent machine cluster based on slow coherence theory as described in any one of the first aspects is implemented.

[0015] In a fourth aspect, a computer-readable medium is provided, on which a computer program is stored, and the computer program is executed by a processor to implement the method for dividing a coherent machine cluster based on slow coherence theory as described in any one of the first aspects.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The method for dividing synchronous machine groups based on slow synchronous theory recorded in the present invention relies on the time series characteristics of the power system, improves the applicability of slow synchronization theory in AC / DC hybrid power grids, and constructs the slow synchronization theory of AC / DC hybrid power grids through the mathematical description of the power system with DC added. The synchronous machine group division can be performed offline, thereby improving the identification accuracy of offline synchronous machine groups; 2. The present invention simulates the DC transmission network as an adjustable active power generator and constructs a simplified model of the AC and DC hybrid power grid by simplifying the admittance array; 3. The present invention achieves offline cluster division of synchronous motors by improving the Laplace array of interconnection density of grid-connected synchronous motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings: Figure 1 This is a wiring diagram of an IEEE39 node system with direct current added in Example 1 of the present invention; Figure 2 This is an example diagram of classification results of synchronous grid-connected synchronous machines in Embodiment 1 of the present invention; Figure 3 It is a three-phase short-circuit speed curve diagram of line 13-14 in embodiment 1 of the present invention; Figure 4 It is a system block diagram in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0019] Embodiment 1: A method for dividing a coherent cluster based on slow coherence theory is specifically implemented by the following steps.

[0020] Step 1: Identify the weakly connected lines of the AC / DC hybrid power grid based on the slow coherence theory.

[0021] (1) Simplify the AC / DC hybrid power grid into a linearized power system model and solve the state matrix of the power system model based on the slow coherence theory. .

[0022] The present invention uses a linearized power system model when using the slow synchronization theory for synchronization grouping. To this end, the classic second-order synchronous grid-connected synchronous machine model is used. This classic model ignores the influence of armature reaction reactance on motor performance and the transient characteristics of the excitation winding. The motion equation of the rotor of the grid-connected synchronous machine can be expressed as: ; In the formula, ; is the number of synchronous machines connected to the grid in the synchronization cluster; is the number of the coherent group The power angle of the grid-connected synchronous machine; Is numbered Angular frequency deviation of the grid-connected synchronous machine; is the rated frequency of the power system; Is numbered Inertia time constant of grid-connected synchronous machine; Is numbered Damping coefficient of the grid-connected synchronous machine; and They are numbered The mechanical power transmitted to the synchronous machine rotor by the grid-connected synchronous machine and the power converted into electrical energy; is the angular frequency of the grid-connected synchronous machine numbered; is the time; d is the differential symbol.

[0023] Based on the above classic grid-connected synchronous machine model, it is assumed that the mechanical power transmitted to the synchronous machine rotor by the grid-connected synchronous machine is is a constant, and it can be deduced that the electromagnetic power converted into electrical energy It can be expressed as: ; Where: and Consider the transient reactance The number after and number Voltage phasor module length of grid-connected synchronous machine; It is the equivalent admittance matrix of the synchronous motor grid-connected busbar, which is formed after the contraction load impedance and transient reactance, ignoring the load. and are the real and imaginary parts of the equivalent admittance matrix respectively; Is numbered and number The power angle difference between the grid-connected synchronous machines.

[0024] According to the definition of coherence in slow homology theory, for a linear system ,set up is the system state variable, if yes The eigenvalue of the second-order system is ,in: ; set up is the state matrix A set of eigenvalues ​​of the system state variables The two state variables in and , if satisfied and Does not contain the corresponding second-order system eigenvalues When any one of and For the eigenvalue group If the state matrix The state variables are divided into Group, any two state variables in the group have characteristic value groups Synchronous, and is a set of eigenvalues ​​with smaller absolute values, then the system is said to be Slowly synchronized, It is called the slow-mode eigenvalue of the system.

[0025] Without considering the effect of the damping coil of the synchronous machine connected to the grid, the electromagnetic output power of the synchronous machine is and power angle After linearization, we get the following expression: ; The complete expression is: ; In this example, there are 10 grid-connected synchronous machines in total. Is numbered Inertia time constant of grid-connected synchronous machine. is the rated frequency, The state variable represented by is the power angle. It should be noted that, except for the angle of attack, all the changing undetermined elements can be used as state variables. is the system state matrix, which is obtained from the linearized power flow equation. Its specific calculation formula is: .

[0026] In the formula, is the system state matrix The physical meaning of the element in the i-th row and j-th column is the power transmitted from node i to node j. is the power transmitted by node i to other nodes.

[0027] like Figure 1 As shown in the figure, a simulation verification is carried out by taking the IEEE39 node system with DC as an example. In this example, the AC transmission line connecting nodes 21 and 22 is replaced by a DC transmission line, and a fixed 600MVA power is transmitted from node 22 to node 21, thus becoming an AC / DC hybrid system.

[0028] (2) Filter out the slow motion modal eigenvalues ​​from the state matrix to obtain the slow motion modal eigenvalue group.

[0029] The eigenvector corresponding to each eigenvalue of the system state matrix represents the response direction of the system in the mode described by the eigenvalue, and each eigenvalue corresponds to a mode of the system.

[0030] Solving the state matrix The eigenvalues ​​of are arranged in order from small to large according to the absolute value of the eigenvalue: From the slow coherence theory, we know that The larger the value, the more vague the regionality of the system is, and the smaller the ratio, the more obvious and clear the regionality is. is the eigenvalue group composed of all slow motion modal eigenvalues, where is the total number of all slow motion modal eigenvalues, and its division expression is as follows: .

[0031] For example, taking the case of 10 eigenvalues: 1) Set ; 2) ; 3) Therefore, the first three eigenvalues ​​are selected as the slow motion mode eigenvalues .

[0032] (3) The degree of synchronization between synchronous generators is analyzed based on the cosine distance coefficient to pre-divide the synchronization of the grid-connected synchronous generators.

[0033] The traditional clustering matrix is ​​not accurate enough when clustering grid-connected synchronous machines. To solve this problem, the optimized cosine distance coefficient is used for clustering analysis. The core idea of ​​this method is to use the cosine of the angle between the eigenvectors corresponding to the eigenvalues ​​of each slow-motion mode to characterize the similarity between synchronous units. The matrix of eigenvectors corresponding to eigenvalues In the Average value over rows To adjust the vector matrix The numerical differences in different dimensions can be mapped into three-dimensional space to more vividly show the synchronization characteristics between units. The specific calculation formula is as follows: ; In the formula, express and The closeness between the two eigenvectors, that is, the synchronization With synchronous machine The degree of coherence between The matrix of eigenvectors The element at row i and column n in ; The matrix of eigenvectors The above two variables represent the closeness of the connection between generator i and generator j relative to the nth motion mode. In general, When the value is greater than 0.7, it is considered that the synchronous machine With synchronous machine Belong to the same synchronous group.

[0034] (4) Calculate the sensitivity of the slow-motion modal eigenvalue group to each transmission path, and determine the total number of slow-motion modal regions based on the degree of coherence between the synchronous units. The lines between the slow-motion modal regions are considered weakly connected lines.

[0035] Step (3) performs synchronization grouping on the synchronous generators in the system, which is the basis for the synchronization grouping of the entire system. The next step is to perform synchronization grouping on the remaining nodes based on the generator node grouping results, so as to divide the entire system into multiple synchronization groups.

[0036] The strength of the transmission path can be determined by calculating the eigenvalue of each slow motion mode in the state matrix. l Sensitivity The specific calculation formula is: ; Slow motion modal eigenvalue group For a certain line The sensitivity can be expressed as follows: ; in, Represents the slow motion modal eigenvalue group pair line l Sensitivity; Indicates The slow motion modal eigenvalues ​​for the line Sensitivity; represents the number of slow motion modal eigenvalues ​​in the slow motion modal eigenvalue group; Indicates Slow motion modal eigenvalues; Indicates line Resistance; Indicates line Reactance; Indicates line The conductivity of Indicates line The electrical conductivity.

[0037] The sensitivity of a line in the power system is high, which means that the line is more vulnerable than other lines. Therefore, the sensitivity of the line can be used to determine whether the line is included in the pre-screening space for the disconnection section. The specific inclusion is related to the actual power system structure. For ease of comparison, the line sensitivity value calculated based on the line with the highest sensitivity in the current system needs to be standardized.

[0038] Generally speaking, after standardization, a line with a sensitivity greater than 0.6 is considered to be a fragile line, and the connecting nodes on both sides of it can be considered to belong to different coherence zones.

[0039] The clustering matrix obtained by analysis To evaluate the group coordination of the synchronous machines connected to the grid, the total number of clear slow-motion modal areas is determined. First, disconnect all the lines, and then select the grid-connected synchronous machine node with the strongest generating capacity in each area as the starting point. Only one area can be selected at a time, and the node with the lowest sensitivity to the adjacent line in the area is selected for inclusion. The selection process is repeated continuously. If during the selection process, a node is included so that two areas are adjacent, the node is included in the area with the lower sensitivity of the connecting line, and the connecting line connecting the node to the other area is cut off.

[0040] After completing the area pre-division, the lines between the slow-motion modal areas in the system are weakly connected lines.

[0041] Step 2: Classify the grid-connected synchronous units according to the coupling degree of the offline motors in the AC / DC hybrid power grid and obtain the offline separation results.

[0042] (1) Calculate the equivalent power angle of the equivalent grid-connected synchronous machine node in the AC / DC hybrid power grid. Considering that graph theory has many important conclusions and can be used to perform power system isomorphism, the mathematical model of the power system is converted into a graph theory model for analysis.

[0043] (2) Constructing an adjacency graph based on equivalent grid-connected synchronous machine nodes in an AC / DC hybrid power grid , the weight value of the weighted graph is , the weighted graph is a subset of the adjacency graph, thus obtaining the Laplace matrix of the improved grid-connected synchronous machine coupling degree , is the power transmitted between the grid-connected synchronous machines i and j. The improved Laplace matrix in the present invention is a matrix that takes the influence of direct current into consideration, and describes the power system containing direct current based on the traditional Laplace matrix.

[0044] By constructing an undirected graph G K (V,V G, E,W) To represent the degree of coupling of the synchronous group in the power system. The Laplace matrix of the degree of coupling of the synchronous group is The definition is as follows: ; In the formula, and are the transient potentials of the i-th and j-th grid-connected synchronous machines respectively; is the imaginary part of the corresponding element of the contraction admittance matrix of the grid-connected synchronous machine node; Represents the power angle difference between grid-connected synchronous machines i and j.

[0045] (3) Calculate the Federer vector according to the generalized characteristic formula ; The generalized characteristic formula is: ; Where: is the Laplace matrix, is the generalized eigenvalue, is the desired Federer vector; , is the identity matrix, m is the number of synchronous motor nodes, matrix M is a matrix with g rows and g columns, and g is the number of system nodes.

[0046] (4) Using the clustering method, based on the Federer vector The components of each row in are grouped, and the components are the coordinates of the vectors, so as to obtain the offline classification results of the grid-connected synchronous units. For the convenience of analysis, it is assumed that a system has four synchronous machines, two of which have eigenvalues ​​that are slow motion mode eigenvalues, which are specifically expressed as follows: ; The offline grouping result calculated according to the clustering algorithm is that the synchronous machine represented by the first row of the matrix and the synchronous machine represented by the second row are divided into the same machine group for the slow motion modal eigenvalue represented by the second column. Similarly, the synchronous machine represented by the third row of the matrix and the synchronous machine represented by the fourth row are divided into the same machine group for the slow motion modal eigenvalue represented by the first column.

[0047] Step 3: Use the weakly connected line as the pre-screening decision space for the disconnection section, and provide a reference for disconnection when a fault occurs in the AC / DC hybrid power grid based on the offline separation results of the grid-connected synchronous units.

[0048] In the theoretical analysis of the AC and DC hybrid power grid, the optimized Laplace matrix of the interconnection density of the grid-connected synchronous machines is constructed by simplifying the admittance matrix, and the eigenvalues ​​and eigenvectors are analyzed in depth. The first three smallest eigenvalues ​​are selected as the slow dynamic characteristic mode, and the corresponding eigenvectors are obtained based on this, as listed in Table 1. When the eigenvectors are close, it indicates that they have similar dynamic behaviors and can be divided into different groups of synchronous units. Obviously, the structure of the AC and DC hybrid power grid is quite complex, and there are many possible grouping methods. If a fault occurs in the power grid, depending on the nature and location of the fault, it may cause changes in the synchronization grouping between different units.

[0049] like Figure 2 As shown in the figure, the corresponding feature vectors of the three modes are mapped into three-dimensional space vectors. Different modes can be obtained from different perspectives, which also reflect different synchronization grouping trends. G9 and G10 show similar synchronization trends despite their geographical differences. The same is true for other groups of units. Therefore, if there is no failure between these units, they will tend to be synchronized; otherwise, they will lose synchronization.

[0050] Table 1 Characteristic vector table of each unit in AC / DC hybrid system

[0051] Further research was conducted, and a three-phase short circuit fault was introduced at the midpoint of the transmission line 13-14. The speed change curve of the grid-connected synchronous machine was obtained by simulation calculation using the DIgSILENT software. Figure 3Observation results show that when a fault causes G2 and G3 to be disconnected from other units, G2 and G3 will be separated from the original synchronous units to form a new independent operation group.

[0052] Embodiment 2: A coherent cluster partitioning system based on slow coherence theory, the system is used to implement the coherent cluster partitioning method based on slow coherence theory as described in Embodiment 1, such as Figure 4 As shown, it includes a line identification module, a coupling separation module and a decoupling processing module.

[0053] Among them, the line identification module is used to identify the weakly connected lines of the AC / DC hybrid power grid based on the slow coherence theory; the coupling separation module is used to classify the grid-connected synchronous units according to the coupling degree of the offline motors in the AC / DC hybrid power grid to obtain the offline separation results; the decoupling processing module is used to use the weakly connected lines as the decoupling section to pre-screen the decision space, and provide a reference for the decoupling of the AC / DC hybrid power grid when a fault occurs based on the offline separation results of the grid-connected synchronous units.

[0054] The present invention also records a computer terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the method for dividing a coherent machine cluster based on slow coherence theory as described in Example 1 is implemented.

[0055] The present invention also records a computer-readable medium on which a computer program is stored. The computer program is executed by a processor to implement the method for dividing a coherent machine group based on slow coherence theory as described in Example 1.

[0056] Working principle: The present invention relies on the time series characteristics of the power system to improve the applicability of the slow synchronization theory in the AC-DC hybrid power grid; the present invention simulates the DC transmission network as an adjustable active power generator, and constructs a simplified model of the AC-DC hybrid power grid through a simplified admittance array.

[0057] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0058] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0059] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0060] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0061] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. The method of dividing the coherent cluster based on the slow coherence theory is characterized by: The following steps are involved: Identify weakly connected lines in AC / DC hybrid power grids based on slow coherence theory; The grid-connected synchronous units are classified according to the coupling degree of offline motors in the AC / DC hybrid power grid, and the offline separation results are obtained; The weakly connected line is used as the pre-screening decision space for the disconnection section, and the offline separation results of the grid-connected synchronous units are used to provide a reference for disconnection when a fault occurs in the AC / DC hybrid power grid.

2. The method for dividing a coherent cluster based on slow coherence theory according to claim 1, characterized in that: The process of identifying weakly connected lines of the AC / DC hybrid power grid based on the slow coherence theory is specifically as follows: The AC / DC hybrid power grid is simplified into a linearized power system model, and the state matrix of the power system model is solved based on the slow coherence theory; The slow motion modal eigenvalues ​​are screened out from the state matrix to obtain a slow motion modal eigenvalue group; The degree of synchronization between synchronous generators is analyzed based on the cosine distance coefficient to pre-divide the synchronization of the grid-connected synchronous generators. The sensitivity of the slow-motion modal eigenvalue group to each transmission path is calculated, and the total number of slow-motion modal regions is determined in combination with the degree of coherence between the synchronous units, with the lines between the slow-motion modal regions being weakly connected lines.

3. The method for dividing a coherent cluster based on slow coherence theory according to claim 2, characterized in that: The process of selecting the slow motion modal eigenvalue from the state matrix is ​​specifically as follows: Arrange the eigenvalues ​​in the state matrix in ascending order according to their absolute values ​​to obtain a first sequence; The ratio of adjacent eigenvalues ​​is calculated by the ratio between the previous eigenvalue and the next eigenvalue in the first sequence; Select the interval corresponding to the smallest ratio among all adjacent eigenvalue ratios as the dividing point; The eigenvalues ​​arranged before the division point are selected from the first sequence as the slow motion mode eigenvalues.

4. The method for dividing a coherent cluster based on slow coherence theory according to claim 2, characterized in that: The process of analyzing the synchronization degree between synchronous generators based on the cosine distance coefficient to pre-divide the synchronization of the grid-connected synchronous generators is specifically as follows: The cosine of the angle between the eigenvectors corresponding to the eigenvalues ​​of each slow motion mode is used to characterize the degree of synchronization between the synchronous units. If the degree of synchronization between two synchronous units is greater than a set threshold, the corresponding two synchronous units belong to the same synchronous unit group.

5. The method for dividing a coherent cluster based on slow coherence theory according to claim 2, characterized in that: The expression for calculating the sensitivity of the slow motion modal eigenvalue group to each transmission path is specifically: ； in, Represents the slow motion modal eigenvalue group pair line Sensitivity; Indicates The slow motion modal eigenvalues ​​for the line Sensitivity; represents the number of slow motion modal eigenvalues ​​in the slow motion modal eigenvalue group; Indicates Slow motion modal eigenvalues; Indicates line The resistance of Indicates line Reactance; Indicates line The conductivity; Indicates line The electrical conductivity.

6. The method for dividing a coherent cluster based on slow coherence theory according to claim 2, characterized in that: The process of determining the total number of slow motion modal regions in combination with the degree of coherence between the synchronous units is specifically as follows: Disconnect all the lines and select the grid-connected synchronous machine node with the strongest power generation capacity in each area as the starting point; Only one area is selected each time, and the nodes with the lowest sensitivity of adjacent lines in the corresponding area are selected for inclusion; The selection process is repeated continuously. If, during the selection process, a node is included so that two areas are adjacent, the node is included in the area with lower connection line sensitivity, and the connection line connecting the node to the other area is cut off.

7. The method for dividing a coherent cluster based on slow coherence theory according to claim 1, characterized in that: The process of classifying the grid-connected synchronous units according to the coupling degree of the offline motors in the AC / DC hybrid power grid is specifically as follows: Calculate the equivalent power angle of the equivalent grid-connected synchronous machine node in the AC / DC hybrid power grid; An adjacency graph is constructed with equivalent grid-connected synchronous machine nodes in AC / DC hybrid power grid, and weight values ​​are assigned to the weighted graph in the adjacency graph based on the ratio of transmission power to the corresponding power angle difference, thus obtaining an improved Laplace matrix of coupling degree of grid-connected synchronous machines. Calculate the Federer vector according to the generalized characteristic formula; The clustering method is used to group the vector coordinates of each row in the Federer vector to obtain the offline classification results of the grid-connected synchronous units.

8. A coherent cluster partitioning system based on slow coherence theory is characterized by: include: Line identification module, used to identify weakly connected lines in AC / DC hybrid power grids based on slow coherence theory; A coupling separation module is used to classify the grid-connected synchronous units according to the coupling degree of the offline motors in the AC / DC hybrid power grid and obtain offline separation results; The decoupling processing module is used to use the weakly connected line as the decoupling section pre-screening decision space, and provide a reference for decoupling when a fault occurs in the AC / DC hybrid power grid based on the offline separation result of the grid-connected synchronous unit.

9. A computer terminal comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the coherent machine cluster partitioning method based on slow coherence theory as described in any one of claims 1 to 7 is implemented.

10. A computer readable medium having a computer program stored thereon, characterized in that: The computer program is executed by a processor to implement the method for partitioning a coherent machine cluster based on slow coherence theory as described in any one of claims 1 to 7.

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