Method and device for analyzing stability of grid-connected system

Abstract

The invention relates to the technical field of power system analysis, and discloses a grid-connected system stability analysis method and device, and the method comprises the steps: obtaining a target power network corresponding to a grid-connected system; fitting the stability criterion corresponding to the target power network at different moments with the generalized short circuit ratio to construct a fitting curve graph; and determining the state of the grid-connected system according to the fitting curve graph. According to the invention, after the target power network corresponding to the grid-connected system is obtained, the corresponding stability criteria and generalized short-circuit ratios of the target power network at a plurality of moments are obtained, and the fitting curve graph corresponding to the grid-connected system is obtained according to the stability criteria and generalized short-circuit ratios; and then the state (steady state / transient state) of the grid-connected system at the target moment can be obtained through analysis according to the fitting curve graph, and the stability of the VSC grid-connected system can be effectively analyzed.

Description

Technical Field

[0001] The present application relates to the technical field of power system analysis, and in particular to a method and device for analyzing the stability of a grid-connected system. Background Art

[0002] With the access of large-scale renewable energy (such as wind power generation, photovoltaic power generation, etc.) based on voltage source converters (VSC), the energy structure of new power systems has changed.

[0003] Due to the addition of a large number of VSC devices, the voltage support capacity has decreased, the AC power grid has gradually weakened, and this has caused a series of power system stability problems.

[0004] However, the related art lacks a method for analyzing the stability of the VSC grid-connected system. Summary of the invention

[0005] The present application aims to solve at least one of the technical problems in the above-mentioned technology to a certain extent, and proposes a grid-connected system stability analysis method, including:

[0006] Obtaining a target power network corresponding to the grid-connected system;

[0007] Fitting the stability criterion and the generalized short-circuit ratio corresponding to the target power network at different times to construct a fitting curve graph;

[0008] The state of the grid-connected system is determined according to the fitting curve diagram.

[0009] Preferably, the method for acquiring the stability criterion corresponding to the target power network includes:

[0010] Constructing a first mathematical model of the target power network;

[0011] Determining an expression of a stability criterion of the grid-connected system based on the first mathematical model;

[0012] According to the expression of the stability criterion, the stability criterion corresponding to each of the target power network at a plurality of moments is obtained.

[0013] Preferably, constructing the first mathematical model of the target power network includes:

[0014] According to the network topology of the target power network, construct a directed connectivity graph and an association matrix corresponding to the target power network;

[0015] Constructing an electrical quantity matrix corresponding to the directed connected graph;

[0016] Based on Kirchhoff's law, according to the correlation matrix and the electrical quantity matrix, a dynamic equation of the target power network is obtained;

[0017] The dynamic equation is simplified according to the number of nodes of different node types in the target power network to obtain a first mathematical model of the grid-connected system, wherein the node types include: non-converter node types and converter node types.

[0018] Preferably, based on the first mathematical model, determining an expression of a stability criterion of the grid-connected system comprises:

[0019] Simplifying the first mathematical model according to the number of nodes corresponding to the converter node type in the target power network to obtain a second mathematical model;

[0020] An expression for a stability criterion of the grid-connected system is determined based on the differential equation of the phase-locked loop and the second mathematical model.

[0021] Preferably, determining the state of the grid-connected system according to the fitting curve graph includes:

[0022] Determining a target generalized short-circuit ratio of the grid-connected system in a steady state according to the fitting curve graph;

[0023] The first generalized short-circuit ratio of the grid-connected system at the target time is compared with the target generalized short-circuit ratio to determine the state of the grid-connected system at the target time.

[0024] Preferably, comparing the first generalized short-circuit ratio of the grid-connected system at the target time with the target generalized short-circuit ratio to determine the state of the grid-connected system at the target time includes at least one of the following:

[0025] When the first generalized short-circuit ratio is greater than or equal to the target generalized short-circuit ratio, determining that the grid-connected system is in a steady state at the target time;

[0026] When the first generalized short-circuit ratio is less than the target generalized short-circuit ratio, it is determined that the grid-connected system is in a transient state at the target moment.

[0027] The present application also proposes a grid-connected system stability analysis system, comprising:

[0028] An equivalent order reduction module is used to obtain the target power network corresponding to the grid-connected system;

[0029] A curve fitting module, used for fitting the stability criterion and the generalized short-circuit ratio corresponding to the target power network at different times, and constructing a fitting curve graph;

[0030] A state determination module is used to determine the state of the grid-connected system according to the fitting curve diagram.

[0031] Preferably, the method executed by the state determination module includes:

[0032] Determining a target generalized short-circuit ratio of the grid-connected system in a steady state according to the fitting curve graph;

[0033] The first generalized short-circuit ratio of the grid-connected system at the target time is compared with the target generalized short-circuit ratio to determine the state of the grid-connected system at the target time.

[0034] The present application also proposes an electronic device, comprising a memory and a processor, wherein the memory stores a computer program or instruction, and when the computer program or instruction is executed by the processor, it is at least used to implement the above method.

[0035] The present application also proposes a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program or instruction, and when the computer program or instruction is executed by a processor, it is at least used to implement the above method.

[0036] Compared with the prior art, the beneficial effects of this application are:

[0037] After obtaining the target power network corresponding to the grid-connected system, the present application obtains the stability criterion and generalized short-circuit ratio corresponding to the target power network at several moments, and obtains the fitting curve graph corresponding to the grid-connected system based on the stability criterion and the generalized short circuit. Then, the state (steady state / transient) of the grid-connected system at the target moment can be obtained based on the analysis of the fitting curve graph, which can effectively analyze the stability of the VSC grid-connected system.

[0038] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures particularly pointed out in the written description and the drawings.

[0039] The technical solution of the present application is further described in detail below through the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings:

[0041] Figure 1 A schematic diagram of the grid-connected system stability analysis method provided in this application;

[0042] Figure 2The VSC grid-connected system stability analysis model and its simplified model diagram of the embodiment;

[0043] Figure 3 This is the block diagram of the traditional VSC grid-connected system;

[0044] Figure 4 A phase-locked loop block diagram provided for an embodiment;

[0045] Figure 5 The figure is a fitting curve diagram of the generalized short circuit ratio and the stability criterion provided in the embodiment;

[0046] Figure 6 It is a frequency waveform diagram of the grid-connected system in the embodiment when the generalized short-circuit ratio is 0.42;

[0047] Figure 7 is a phase plane waveform diagram of the grid-connected system in the embodiment when the generalized short-circuit ratio is 0.6;

[0048] Figure 8 is a response waveform diagram of the grid-connected system in the embodiment when the generalized short-circuit ratio is 0.6;

[0049] Fig. 9 is a phase plane waveform diagram of the grid-connected system in the embodiment when the generalized short-circuit ratio is 0.3;

[0050] Fig.10 is a response waveform diagram of the grid-connected system in the embodiment when the generalized short-circuit ratio is 0.3;

[0051] Fig.11 A schematic diagram of a grid-connected system stability analysis system provided in this application;

[0052] Fig.12 A schematic diagram of an electronic device provided for this application;

[0053] Fig.13 A schematic diagram of a computer-readable storage medium provided in the present application. DETAILED DESCRIPTION

[0054] The present application is described below in conjunction with the accompanying drawings. The preferred embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0055] Figure 1 The grid-connected system stability analysis method provided in this application includes:

[0056] S11. Obtain the target power network corresponding to the grid-connected system;

[0057] S12. Fitting the stability criterion and the generalized short-circuit ratio corresponding to the target power network at different times to construct a fitting curve graph;

[0058] S13. Determine the state of the grid-connected system according to the fitting curve diagram.

[0059] It should be noted that when the distribution feeder parameters (i.e., line parameters) in the target power network change, the generalized short-circuit ratio and the stability criterion will change accordingly, so there is a certain relationship between them. Therefore, the generalized short-circuit ratio and the stability criterion obtained at different times can be fitted to obtain a fitting curve, and the generalized short-circuit ratio of the grid-connected system at the stable moment (that is, the moment when the grid-connected system is in a steady state) can be obtained according to the fitting curve. Then, the generalized short-circuit ratio at the stable moment can be used as a threshold to analyze and judge the state of the grid-connected system at the target moment, that is, to analyze whether the grid-connected system is in a steady state or transient state at the target moment, and to analyze the stability of the grid-connected system in combination with the fitting curve.

[0060] According to the embodiments of the present application, Figure 2 As shown, the grid-connected system may specifically be a VSC grid-connected system including a main grid, at least one VSC connected to the main grid (taking the number of VSCs as 2 as an example) and connecting lines (including cables, transformers, etc.).

[0061] According to an embodiment of the present application, in S11, the target power network corresponding to the grid-connected system can be obtained by performing equivalent reduction on the grid-connected system, and the total number of nodes in the target power network is less than the total number of nodes in the grid-connected system.

[0062] According to an embodiment of the present application, a method for obtaining a stability criterion corresponding to a target power network includes: constructing a first mathematical model of the target power network; determining an expression of a stability criterion of a grid-connected system based on the first mathematical model; and obtaining a stability criterion corresponding to the target power network at each of a number of moments according to the expression of the stability criterion. In this embodiment, a first mathematical model of the target power network is constructed, and then an expression of a stability criterion of a grid-connected system is derived based on the first mathematical model, and then, according to the expression of the stability criterion, a stability criterion corresponding to the target power network at each of the several moments is obtained, providing a data source for fitting to obtain a fitting curve graph.

[0063] According to an embodiment of the present application, constructing a first mathematical model of a target power network includes:

[0064] S1111. According to the network topology of the target power network, construct a directed connectivity graph and an association matrix corresponding to the target power network; it should be noted that the directed connectivity graph includes at least one node and at least one directed edge.

[0065] It is assumed here that there are p nodes and q edges (p and q are positive integers) in the target power network, and the direction of each edge is given. The network topology of the target power network can be represented by a directed connected graph: G = {P, Q}, where P represents the set of nodes in the directed connected graph, P = {1, 2, ..., p}, and Q represents the set of directed edges in the directed connected graph, Q = {1, 2, ..., q}.

[0066] Furthermore, the correlation matrix of the target power network can be defined as: D∈R p×q , the elements of the correlation matrix can be expressed as: D ij ={-1,0,1}. When branch j (i.e. directed edge j) is associated with node i, and the direction of the directed edge is away from node i, D ij =1; when branch j is associated with node i and the direction of the directed edge is pointing to node i, D ij = -1; when branch j is not associated with node i, D ij =0.

[0067] S1112. Construct an electrical quantity matrix corresponding to the directed connected graph, wherein the electrical quantity matrix includes at least one of a current matrix, a voltage matrix, and an inductance matrix. The elements in the current matrix are a matrix composed of the currents of each node, the voltage matrix is ​​a matrix composed of the voltages of each node, and the inductance matrix is ​​a diagonal matrix composed of the inductances on each directed edge. Here, the voltage of node i is represented as v dqi , the injected current of node i is represented as i dqi , then the current matrix (I dq ), voltage matrix (v dq ) and the inductance matrix (L) can be expressed as follows:

[0068]

[0069] Where l represents the line inductance (that is, the inductance on the branch), for example, l q Represents the inductance of branch q. For details, see Figure 3 The l shown 1 , l s , l q .

[0070] S1113. Based on Kirchhoff's law, according to the correlation matrix and the electrical quantity matrix, the dynamic equation of the target power network is obtained. Here, based on Kirchhoff's law, the dynamic equation of the target power network can be further obtained:

[0071]

[0072] Where I represents the identity matrix, i dq represents the injected current, ω n is the angular frequency, k is the resistance-to-inductance ratio, (l q represents the impedance on branch j, l q represents the inductance on branch j, Q represents the set of directed edges), L -1 represents the inverse matrix of the incidence matrix L, D T Represents the transposed matrix of the incidence matrix D.

[0073] S1114. Simplify the dynamic equations according to the number of nodes of different node types in the target power network to obtain the first mathematical model of the grid-connected system; wherein the node types include: non-converter node types and converter node types. Here, it is assumed that there are m non-converter nodes and n converter nodes in the target power network, then the correlation matrix D and the current matrix I dq 、voltage matrix v dq Then they can be split according to the node type as follows: I dq =[I ndq ,I mdq ],v dq =[v ndq ,v mdq ] Among them, i dq D n ∈R n×q ,D m ∈R m×q , I ndq ,V ndq ∈R 2×n , I mdq ,V mdq ∈R 2×m It should be noted that since the current of the non-converter node is 0, that is, I mdq =0, so I dq =[I ndq ,I mdq ],V dq =[V ndq ,V mdq ]After substituting into the above dynamic equation, the dynamic equation of the grid-connected system (that is, the first mathematical model of the grid-connected system) can be obtained, namely:

[0074]

[0075] in,

[0076] According to an embodiment of the present application, based on the first mathematical model, determining the expression of the stability criterion of the grid-connected system includes: simplifying the first mathematical model according to the number of nodes corresponding to the converter node type in the target power network to obtain the second mathematical model; determining the expression of the stability criterion of the grid-connected system according to the differential equation of the phase-locked loop and the second mathematical model. In this embodiment, the first mathematical model of the grid-connected system can be simplified to derive the stability criterion of the grid-connected system, and the detailed process is described as follows:

[0077] First, the first mathematical model is decomposed, and n converter nodes are retained (that is, non-converter nodes are eliminated and complex distribution lines are simplified). Then, the first mathematical model can be rewritten as a second mathematical model. The expression of the second mathematical model is:

[0078]

[0079] Among them, V pdq It represents the voltage matrix of the converter PCC point in the dq coordinate system, I pdq is the current matrix of the converter injected into the PCC point in the dq coordinate system, B and C are the electrical quantity matrices, and their expressions are:

[0080]

[0081] Furthermore, the output angle difference between the i-th converter phase-locked loop (PLL) and the external grid angle is defined as δ i =θ PLLi -θ g , the current injected into each converter is in is the injection current amplitude, α i is the injected current phase angle, the subscript i represents the i-th converter, and the superscript i is the value at the i-th PLL output angle. Similarly, the voltage of each converter in the dq coordinate system can be expressed as and

[0082] According to the above definition, the expression of the second mathematical model can be written as follows:

[0083]

[0084] in,

[0085] Further deduction of the second mathematical model can obtain the following first formula:

[0086]

[0087]

[0088] like Figure 4 As shown in the figure, it is a phase-locked loop control block diagram. The differential equation of the phase-locked loop is expressed as:

[0089]

[0090] Substituting the first formula into the differential equation of the phase-locked loop yields:

[0091]

[0092]

[0093] The angular perturbation of the equilibrium point is δ di Defined as δ di =δ i -δ 0 , where δ 0 For the balance point.

[0094] Using Taylor expansion in δ di Expand the above differential equation to obtain the following second formula:

[0095]

[0096] Then, the solution to the second formula is in the form of the following third formula:

[0097]

[0098] Substituting the third formula into the second formula yields the following fourth formula:

[0099]

[0100] Assumption variables Among them, λ 1,2 It is the characteristic root of the grid-connected system.

[0101] To make the grid-connected system stable, λ must be satisfied 1,2 >0. Therefore, the fourth formula above can be rewritten as the fifth formula below:

[0102]

[0103] Where c = a 2 +b 2 .

[0104] Therefore, the characteristic equation of the fifth formula above can be written as the sixth formula below:

[0105] (ω o λ+a 1i ω o +ca 1i ω o) 2 -3ca 6i 2 =0

[0106] Therefore, the stability criterion of the VSC system can be set as λ sta , then the expression of the stability criterion is:

[0107] λ sta =(a 1i +ca 3i )ω 0 -|3ca 6i |>0

[0108] According to an embodiment of the present application, determining the state of the grid-connected system according to the fitting curve graph includes:

[0109] S141. Determine the target generalized short-circuit ratio of the grid-connected system in a steady state according to the fitting curve diagram; Figure 5 As shown, it is a fitting curve diagram obtained by fitting in an optional embodiment provided by the present application, wherein the abscissa represents the generalized short circuit ratio, and the ordinate represents the stability criterion, wherein when the stability criterion is greater than 0, it indicates that the grid-connected system is in a steady state, therefore, Figure 5 For the corresponding grid-connected system, when the generalized short-circuit ratio is greater than 0.42, the grid-connected system is in a steady state, and 0.42 can be used as the target generalized short-circuit ratio of the grid-connected system.

[0110] S1042. Compare the first generalized short-circuit ratio of the grid-connected system at the target time with the target generalized short-circuit ratio to determine the state of the grid-connected system at the target time.

[0111] It should be noted that, when studying a multi-machine system, the traditional short-circuit ratio is not applicable. The embodiment of the present application introduces a generalized short-circuit ratio to perform grid-connected system stability analysis. The specific expression of the generalized short-circuit ratio is: Among them, gSCR represents the generalized short-circuit ratio, min(·) represents the minimum value of the vector element, eig(·) represents the characteristic root of the matrix, Im(·) represents the imaginary part of the matrix, SB represents the diagonal matrix with VSC capacity as elements, and Y represents the reduced-order admittance matrix. From the above expression of the generalized short-circuit ratio, it can be seen that the factors affecting the generalized short-circuit ratio are reflected in the line parameters. It should also be noted that the smaller the generalized short-circuit ratio, the weaker the AC system, and the more likely the entire grid-connected system will become unstable.

[0112] According to an embodiment of the present application, the first generalized short-circuit ratio of the grid-connected system at the target time is compared with the target generalized short-circuit ratio to determine the state of the grid-connected system at the target time, including at least one of the following: when the first generalized short-circuit ratio is greater than or equal to the target generalized short-circuit ratio, it is determined that the grid-connected system is in a steady state at the target time; when the first generalized short-circuit ratio is less than the target generalized short-circuit ratio, it is determined that the grid-connected system is in a transient state at the target time. The transient state here refers to the instantaneous state when the grid-connected system has not yet reached a stable state, which can be understood as an unstable state.

[0113] In the above embodiment, for a VSC grid-connected system with complex feeders, a stability criterion of the VSC grid-connected system and a generalized short-circuit ratio of the VSC grid-connected system in a steady state (i.e., a target generalized short-circuit ratio) can be given. The generalized short-circuit ratio can be changed by changing the line parameters. For example, at the target time, the changed generalized short-circuit ratio (taking the first generalized short-circuit ratio as an example) is obtained, and then the relationship between the first generalized short-circuit ratio and the target generalized short-circuit ratio is further analyzed to determine whether the VSC grid-connected system tends to be stable. Among them, if the first generalized short-circuit ratio is higher than the target generalized short-circuit ratio, it means that the VSC grid-connected system is stable at the target time; if the first generalized short-circuit ratio is lower than the target generalized short-circuit ratio, it means that the VSC grid-connected system is unstable at the target time.

[0114] It should be noted that the grid-connected system stability analysis method of the embodiment given in the present application can be applicable to the inverter grid-connected system. Therefore, the analysis method given in the present application can be applied to the stability analysis of various VSC-based new energy grid-connected systems such as wind power generation, photovoltaic power generation, energy storage, hydrogen production, etc., and does not limit the number of VSCs.

[0115] Still Figure 2 For example, the grid-connected system (VSC grid-connected system) may specifically include: main grid, 2 VSCs, cables and transformers. Among them, the line of the grid-connected system is RL type line, and has the same resistance-inductance ratio The control circuit of VSC mainly includes phase-locked loop and double closed-loop control. Figure 3 As shown, Figure 2 The detailed parameters of the grid-connected system are given in Table 1 below.

[0116] Table 1

[0117]

[0118] like Figure 5 As shown, in the embodiment of the present application, by continuously changing the line parameters, different generalized short circuit ratios and different stability criteria are obtained, and then the two are continuously fitted to obtain the following Figure 5 The fitting curve is shown in Figure 2. Figure 5It can be seen that the generalized short circuit ratio (that is, the target generalized short circuit ratio) in the steady state of the embodiment of the present application is 0.42. Figure 6-7 , we can see that the system is stable at this time; Figure 8-9 Therefore, the feasibility of the grid-connected system stability analysis method of the embodiment of the present application can be verified.

[0119] In the above embodiment, by fitting the generalized short-circuit ratio and stability criterion of the VSC grid-connected system at different times, a fitting curve graph can be obtained, and then the generalized short-circuit ratio of the VSC grid-connected system at the stable moment (i.e., the target generalized short-circuit ratio) can be obtained from the fitting curve graph; further, in combination with the fitting curve graph, the influence of line parameters on the stability of the VSC grid-connected system can be analyzed, so that the influence of line parameters on system stability can be effectively analyzed, providing a basis for stability analysis for the actual power network.

[0120] In an embodiment of the present application, the grid-connected system can be equivalently reduced in order to obtain a target power network corresponding to the grid-connected system. Thereafter, by changing line parameters, the stability criterion and generalized short-circuit ratio corresponding to the target power network at different times can be obtained. Then, a fitting curve graph corresponding to the grid-connected system is obtained based on the stability criterion and the generalized short circuit. Finally, the state (steady state / transient) of the grid-connected system at the target time is obtained based on the analysis of the fitting curve graph. In this way, the problem of how to analyze the stability of the VSC grid-connected system can be solved.

[0121] Based on the same concept, Fig.11 As shown, the present application also proposes a grid-connected system stability analysis system, including: an equivalent order reduction module 21, used to obtain a target power network corresponding to the grid-connected system; a curve fitting module 22, used to fit the stability criterion and the generalized short-circuit ratio corresponding to the target power network at different times to construct a fitting curve graph; a state determination module 23, used to determine the state of the grid-connected system according to the fitting curve graph.

[0122] like Fig.12 As shown, the present application provides an electronic device 1000, which includes a memory 1002 and a processor 1001. The memory 1002 stores a computer program or instruction. When the computer program or instruction is executed by the processor 1001, it is at least used to implement the above method. Fig.13 As shown, the present application provides a computer-readable storage medium 1100, in which a computer program or instruction is stored. When the computer program or instruction is executed by a processor, it is at least used to implement the above method.

[0123] It is obvious that a person skilled in the art may make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A grid-connected system stability analysis method, It is characterized in that include: Obtaining a target power network corresponding to the grid-connected system; Fitting the stability criterion and the generalized short-circuit ratio corresponding to the target power network at different times to construct a fitting curve graph; The state of the grid-connected system is determined according to the fitting curve diagram.

2. The method according to claim 1, It is characterized in that The method for acquiring the stability criterion corresponding to the target power network includes: Constructing a first mathematical model of the target power network; Determining an expression of a stability criterion of the grid-connected system based on the first mathematical model; According to the expression of the stability criterion, the stability criterion corresponding to each of the target power network at a plurality of moments is obtained.

3. The method according to claim 2, It is characterized in that Constructing a first mathematical model of the target power network, comprising: According to the network topology of the target power network, construct a directed connectivity graph and an association matrix corresponding to the target power network; Constructing an electrical quantity matrix corresponding to the directed connected graph; Based on Kirchhoff's law, according to the correlation matrix and the electrical quantity matrix, a dynamic equation of the target power network is obtained; The dynamic equation is simplified according to the number of nodes of different node types in the target power network to obtain a first mathematical model of the grid-connected system, wherein the node types include: non-converter node types and converter node types.

4. The method according to claim 3, It is characterized in that Based on the first mathematical model, determining an expression of a stability criterion of the grid-connected system includes: Simplifying the first mathematical model according to the number of nodes corresponding to the converter node type in the target power network to obtain a second mathematical model; An expression for a stability criterion of the grid-connected system is determined based on the differential equation of the phase-locked loop and the second mathematical model.

5. The method according to claim 1, It is characterized in that Determining the state of the grid-connected system according to the fitting curve graph includes: Determining a target generalized short-circuit ratio of the grid-connected system in a steady state according to the fitting curve graph; The first generalized short-circuit ratio of the grid-connected system at the target time is compared with the target generalized short-circuit ratio to determine the state of the grid-connected system at the target time.

6. The method according to claim 5, It is characterized in that Comparing the first generalized short-circuit ratio of the grid-connected system at the target time with the target generalized short-circuit ratio to determine the state of the grid-connected system at the target time includes at least one of the following: When the first generalized short-circuit ratio is greater than or equal to the target generalized short-circuit ratio, determining that the grid-connected system is in a steady state at the target time; When the first generalized short-circuit ratio is less than the target generalized short-circuit ratio, it is determined that the grid-connected system is in a transient state at the target moment.

7. A grid-connected system stability analysis system, It is characterized in that include: An equivalent order reduction module is used to obtain the target power network corresponding to the grid-connected system; A curve fitting module, used for fitting the stability criterion and the generalized short-circuit ratio corresponding to the target power network at different times, and constructing a fitting curve graph; A state determination module is used to determine the state of the grid-connected system according to the fitting curve diagram.

8. The system of claim 7, It is characterized in that The method executed by the state determination module includes: Determining a target generalized short-circuit ratio of the grid-connected system in a steady state according to the fitting curve graph; The first generalized short-circuit ratio of the grid-connected system at the target time is compared with the target generalized short-circuit ratio to determine the state of the grid-connected system at the target time.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program or instruction. It is characterized in that When the computer program or instruction is executed by the processor, it is used to implement at least the method according to any one of claims 1 to 6.

10. A computer-readable storage medium, It is characterized in that The computer-readable storage medium stores a computer program or instruction, and when the computer program or instruction is executed by a processor, it is used to implement at least the method according to any one of claims 1 to 6.

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