Subsynchronous / supersynchronous oscillation stability evaluation method and system of multi-converter network

Abstract

The invention discloses a sub / super synchronous oscillation stability evaluation method and system for a multi-converter network, and the method comprises the steps: dividing a target multi-converter network grid-connected system into a to-be-researched network and a grid-connected point system according to the demands, respectively acquiring an aggregation frequency coupling admittance model of the network to be researched and an aggregation frequency coupling impedance model of the grid-connected point system side node network; based on the aggregation frequency coupling admittance model and the aggregation frequency coupling impedance model, calculating an equivalent single converter grid-connected system return rate matrix, and determining a characteristic value track of the equivalent single converter grid-connected system return rate matrix; and evaluating the subsynchronous / super-synchronous oscillation stability of the target multi-converter grid-connected system based on the characteristic value track. According to the method, for the multi-converter complex network, the frequency coupling characteristic under the control action of the converter is considered, and the efficiency and practicability of sub / super synchronous oscillation stability analysis of the multi-converter complex network grid-connected system are improved by applying the efficient aggregation method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power systems, and more particularly, to a method and system for sub / super-synchronous oscillation stability evaluation of a multi-converter network. BACKGROUND

[0002] Currently, renewable energy is gradually replacing traditional fossil energy, and in the future, new energy generation will become the main source of final energy demand. As the proportion of new energy generation gradually increases, the power system is gradually developing towards high proportions of new energy and high proportions of power electronic equipment. The internal multiple control links of new energy generation and power electronic equipment systems are coupled with each other, forming a complex multi-time scale high-order nonlinear system, which is easy to cause sub / super-synchronous oscillation problems when interacting with the power grid, becoming one of the important problems affecting the safe and stable operation of the power grid.

[0003] Currently, there have been many research results on the sub / super-synchronous oscillation characteristics of converter grid-connected systems. The research methods mainly include time-domain simulation of electromagnetic transient models, eigenvalue analysis of state space models, admittance / impedance model analysis, and Nyquist stability criterion. However, the research is mostly for single-converter grid-connected systems, and the above methods are difficult to apply to the oscillation characteristic analysis of new energy collection systems containing numerous grid-connected converters. Impedance / admittance network modeling is a feasible method for studying the oscillation characteristics of multi-converter networks, but in the sub / super-synchronous frequency range, there is a coupling frequency effect of the converter, and single-structure network modeling cannot reflect this coupling characteristic. Using a series-parallel connection method to aggregate the frequency-coupled impedance is difficult to apply to the sub / super-synchronous oscillation characteristic analysis of complex networks containing multiple converters using general programming. For example, in "Frequency-coupled impedance model of grid-connected converters and its stability analysis", the system broadband oscillation stability of a single-converter connected to a simplified power grid is analyzed based on the generalized Nyquist stability criterion, which is suitable for the oscillation stability analysis of a single-converter connected to a power grid, but does not consider the analysis method for multiple converters connected to a complex power grid. In "Small-signal impedance / admittance network modeling method for new energy generation grid-connected systems", the "oscillation path" is considered, and the frequency-coupled impedance is aggregated in a series-parallel manner. However, the "oscillation path" needs to be known, which is not suitable for early-stage engineering research and is not suitable for multiple-converter complex networks.

[0004] Therefore, there is a need for a method for evaluating the sub / super-synchronous oscillation stability of a multi-converter network. SUMMARY

[0005] The present application provides a method and system for evaluating the sub / super-synchronous oscillation stability of a multi-converter network to solve the problem of how to efficiently evaluate the sub / super-synchronous oscillation stability of a multi-converter network.

[0006] In order to solve the above problems, according to one aspect of the present application, a method for evaluating the sub / super-synchronous oscillation stability of a multi-converter network is provided, the method comprising:

[0007] splitting the target multi-converter grid-connected system into a network under study and a point of common coupling system according to a requirement, and obtaining an aggregated frequency-coupled admittance model of the network under study and an aggregated frequency-coupled impedance model of a network on the side of the point of common coupling system, respectively;

[0008] calculating an equivalent single-converter grid-connected system return ratio matrix based on the aggregated frequency-coupled admittance model and the aggregated frequency-coupled impedance model, and determining an eigenvalue trajectory of the equivalent single-converter grid-connected system return ratio matrix;

[0009] evaluating sub- / super-synchronous oscillation stability of the target multi-converter grid-connected system based on the eigenvalue trajectory.

[0010] Preferably, wherein the aggregated frequency-coupled admittance model of the network under study and the aggregated frequency-coupled impedance model of the network on the side of the point of common coupling system are obtained respectively, comprising:

[0011] obtaining the aggregated frequency-coupled admittance model of the network under study based on a frequency-coupled admittance aggregation method of a network expansion node admittance matrix, comprising:

[0012]

[0013] wherein Y eq_J is the aggregated frequency-coupled admittance model of the network under study; I J is a flow vector injected into aggregated nodes J of the network under study, V J is a voltage vector of the aggregated nodes J of the network under study; is a transpose of V J .

[0014] obtaining the aggregated frequency-coupled impedance model of the network on the side of the point of common coupling system based on a frequency-coupled impedance aggregation method of a network expansion node admittance matrix, comprising:

[0015]

[0016] wherein Z eq_J is the frequency-coupled impedance model of the network on the side of the point of common coupling system; Y eq_Jsys is the frequency-coupled admittance model of the network on the side of the point of common coupling system; I Jsys is a flow vector injected into nodes J on the side of the point of common coupling system, V Jsys is a voltage vector injected into the nodes J on the side of the point of common coupling system; is a transpose of V Jsys .

[0017] Preferably, wherein the equivalent single-converter grid-connected system return ratio matrix is calculated based on the aggregated frequency-coupled admittance model and the aggregated frequency-coupled impedance model, comprising:

[0018] L(s) = Y eq_J (s)Z eq_J (s),

[0019] wherein L(s) is an equivalent single converter grid-connection system return ratio matrix; Y eq_J (s) is an aggregated frequency-coupled admittance model; Z eq_J (s) is an aggregated frequency-coupled impedance model; s is a Laplace operator.

[0020] Preferably, wherein the sub / super-synchronous oscillation stability of the target multi-converter grid-connection system is evaluated based on the eigenvalue trajectory, comprising:

[0021] if the eigenvalue trajectory does not enclose (-1, 0) on the s-plane, it is determined that the sub / super-synchronous oscillation stability of the target multi-converter grid-connection system is stable; otherwise, if the eigenvalue trajectory encloses (-1, 0) on the s-plane, it is determined that the sub / super-synchronous oscillation stability of the target multi-converter grid-connection system is unstable.

[0022] According to another aspect of the present application, a sub / super-synchronous oscillation stability evaluation system of a multi-converter network is provided, the system comprising:

[0023] an equivalent unit for dividing a target multi-converter grid-connection system into a network under study and a grid-connection point system according to requirements, and respectively obtaining an aggregated frequency-coupled admittance model of the network under study and an aggregated frequency-coupled impedance model of a network on the side of the grid-connection point system;

[0024] an eigenvalue trajectory determination unit for calculating an equivalent single converter grid-connection system return ratio matrix based on the aggregated frequency-coupled admittance model and the aggregated frequency-coupled impedance model, and determining an eigenvalue trajectory of the equivalent single converter grid-connection system return ratio matrix;

[0025] a stability evaluation unit for evaluating the sub / super-synchronous oscillation stability of the target multi-converter grid-connection system based on the eigenvalue trajectory.

[0026] Preferably, wherein the equivalent unit respectively obtains the aggregated frequency-coupled admittance model of the network under study and the aggregated frequency-coupled impedance model of the network on the side of the grid-connection point system, comprising:

[0027] an aggregated frequency-coupled admittance model obtaining method based on a network expansion node admittance matrix, for obtaining the aggregated frequency-coupled admittance model of the network under study, comprising:

[0028]

[0029] wherein Y eq_J is the aggregated frequency-coupled admittance model of the network under study; I Ja flow vector injected into the network aggregation node J, V J a voltage vector injected into the network aggregation node J, V a transpose of V J

[0030] The frequency coupling impedance aggregation method based on the admittance matrix of the network expansion node obtains an aggregated frequency coupling impedance model of the grid-connected point system side network, and comprises the following steps:

[0031]

[0032] wherein, Z eq_J is the frequency coupling impedance model of the grid-connected point system side network; Y eq_Jsys is the frequency coupling admittance model of the grid-connected point system side network; I Jsys a flow vector injected into the network aggregation node J, V Jsys a voltage vector injected into the network aggregation node J, V a transpose of V Jsys

[0033] Preferably, wherein the eigenvalue trajectory determination unit, based on the aggregated frequency coupling admittance model and the aggregated frequency coupling impedance model, calculates an equivalent single converter grid-connected system return rate matrix, comprising:

[0034]

[0035] wherein, L(s) is the equivalent single converter grid-connected system return rate matrix; Y eq_J (s) is the aggregated frequency coupling admittance model; Z eq_J (s) is the aggregated frequency coupling impedance model; s is the Laplace operator.

[0036] Preferably, wherein the stability evaluation unit evaluates the sub- / super-synchronous oscillation stability of the target multi-converter grid-connected system based on the eigenvalue trajectory, comprising:

[0037] If the eigenvalue trajectory does not enclose (-1, 0) in the s plane, it is determined that the sub- / super-synchronous oscillation stability of the target multi-converter grid-connected system is stable; otherwise, if the eigenvalue trajectory encloses (-1, 0) in the s plane, it is determined that the sub- / super-synchronous oscillation stability of the target multi-converter grid-connected system is unstable.

[0038] According to another aspect of the present application, the present application provides a computer readable storage medium having a computer program stored thereon, wherein the program is executed by a processor to implement the steps of any one of the sub- / super-synchronous oscillation stability evaluation methods of the multi-converter network.

[0039] ​​Based on another aspect of the present application, the present application provides an electronic device comprising:

[0040] The computer readable storage medium described above; and

[0041] One or more processors for executing the program in the computer readable storage medium.

[0042] The present application provides a method and system for sub / super synchronous oscillation stability evaluation of a multi-converter network, comprising: according to requirements, dividing a target multi-converter network grid-connected system into a network to be researched and a grid-connected point system, and respectively acquiring an aggregated frequency coupling admittance model of the network to be researched and an aggregated frequency coupling impedance model of a section network on the side of the grid-connected point system; based on the aggregated frequency coupling admittance model and the aggregated frequency coupling impedance model, calculating an equivalent single-converter grid-connected system return rate matrix, and determining an eigenvalue trajectory of the equivalent single-converter grid-connected system return rate matrix; based on the eigenvalue trajectory, evaluating sub / super synchronous oscillation stability of the target multi-converter grid-connected system. The present application considers frequency coupling characteristics under the action of converter control for a multi-converter complex network, applies an efficient aggregation method to improve efficiency and practicability of sub / super synchronous oscillation stability analysis of the multi-converter complex network grid-connected system, and makes stability judgment based on a generalized Nyquist stability criterion, thereby solving the problem of wide-frequency oscillation stability analysis of the multi-converter complex network. BRIEF DESCRIPTION OF DRAWINGS

[0043] The exemplary embodiments of the present application can be more completely understood in reference to the following drawings:

[0044] Figure 1 A flowchart of a method for sub / super synchronous oscillation stability evaluation of a multi-converter network according to an embodiment of the present application;

[0045] Figure 2 A schematic diagram of a coupled frequency companion network according to an embodiment of the present application;

[0046] Figure 3 A schematic diagram of a typical four-converter grid-connected system according to an embodiment of the present application;

[0047] Figure 4 A flowchart of a method for sub / super synchronous oscillation stability evaluation of a multi-converter complex network according to an embodiment of the present application;

[0048] Figure 5 A schematic diagram of a system Nyquist curve according to an embodiment of the present application;

[0049] Figure 6 (a) and (b) of FIG. 10 are respectively a schematic diagram of a time-domain simulation waveform and a frequency spectrum analysis according to an embodiment of the present application;

[0050] Figure 7 This is a schematic diagram of the structure of a sub / supersynchronous oscillation stability evaluation system 700 for a multi-converter network according to an embodiment of the present invention. Detailed Implementation

[0051] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0052] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0053] Figure 1 This is a flowchart of a method 100 for evaluating the subsynchronous / supersynchronous oscillation stability of a multi-converter network according to an embodiment of the present invention. Figure 1 As shown, the subsynchronous / supersynchronous oscillation stability assessment method for multi-converter networks provided by this invention, targeting complex multi-converter networks, considers the frequency coupling characteristics under converter control. It applies an efficient aggregation method to improve the efficiency and practicality of subsynchronous / supersynchronous oscillation stability analysis of grid-connected systems with complex multi-converter networks. Furthermore, it uses the generalized Nyquist stability criterion for stability judgment, solving the problem of broadband oscillation stability analysis in complex multi-converter networks. The subsynchronous / supersynchronous oscillation stability assessment method 100 for multi-converter networks provided by this invention begins at step 101. In step 101, the target multi-converter network grid-connected system is divided into the network under study and the grid connection point system according to requirements. The aggregated frequency coupling admittance model of the network under study and the aggregated frequency coupling impedance model of the side-node network of the grid connection point system are obtained respectively.

[0054] Preferably, obtaining the aggregated frequency-coupled admittance model of the network under study and the aggregated frequency-coupled impedance model of the grid connection point system side-node network respectively includes:

[0055] A frequency-coupled admittance aggregation method based on the network extended node admittance matrix is ​​used to obtain the aggregated frequency-coupled admittance model of the network under study, including:

[0056]

[0057] Among them, Yeq_J is the aggregated frequency-coupled admittance model of the network under study; J is the flow vector injected into the aggregated node J of the network under study, V J is the voltage vector of the aggregated node J of the network under study; is the transpose of V J ;

[0058] The frequency-coupled impedance aggregation method based on the network expansion node admittance matrix obtains the aggregated frequency-coupled impedance model of the grid-connected point system side network, comprising:

[0059]

[0060] wherein Z eq_J is the frequency-coupled impedance model of the grid-connected point system side network; Y eq_Jsys is the frequency-coupled admittance model of the grid-connected point system side network; I Jsys is the flow vector injected into the grid-connected point system side node J, V Jsys is the voltage vector injected into the grid-connected point system side node J; is the transpose of V Jsys .

[0061] First, the frequency-coupled admittance / impedance aggregation method based on the network expansion node admittance matrix is described.

[0062] (1) Expansion network node admittance matrix

[0063] In the study of sub- / super-synchronous oscillation characteristics of the grid-connected converter under study in a network containing multiple converters, the aggregated frequency-coupled admittance (impedance) of the grid-connected converter access point and the system side needs to take into account the influence of other grid-connected converters. In the frequency-coupled admittance model of the converter, there are both port voltage quantities and current quantities of complementary frequencies (f d and f c ), while the non-converter elements such as transmission lines and transformers in the network hardly have frequency-coupled effects. Therefore, all nodes in the network can be split into two nodes to form two networks with the same topology as the original network, and the admittances of the transmission lines, transformers and other elements in the network correspond to frequencies f d and f c . For node k of the network, the node KCL equations corresponding to frequencies f d and f c are written as

[0064]

[0065] In the formula: is the disturbance voltage phasor of node k, node i, y gki is the admittance of L non-converter elements grounded at node k, y kiYk, i, f is the i-th element of the frequency coupling admittance model of the k-th non-convertor element between node k and other nodes, Ik, f is the k-th convertor current of the k-th node, Ik, f is the k-th convertor current of the k-th node,

[0066] The second equation of the above formula is transformed into

[0067]

[0068] where is the i-th element of the frequency coupling admittance model of the k-th node.

[0069] From the above formula, the first equation is the KCL of the original network node k corresponding to the frequency f d , denoted as network(f d ), and the second equation is the conjugate equation of the KCL of the original network node k corresponding to the frequency f c , denoted as adjoint network(f c ). As shown in Figure 2 , the voltage and of the non-convertor access node in network(f d ) and adjoint network(f c ) are independent of each other, and the voltage and of the grid-connected convertor access node are the coupling variables between the two networks.

[0070] The node admittance matrix of network(f d ) and adjoint network(f c ) is merged into an extended admittance matrix. For an N-node network, the dimension of the corresponding extended admittance matrix is 2N×2N, and the node voltage vector is

[0071]

[0072] The 2k-1 (k=1, 2,..., N) row of the extended node admittance matrix corresponds to the KCL of the k-th node of network(f d ), and the 2k (k=1, 2,..., N) row of the extended admittance matrix corresponds to the KCL of the k-th node of adjoint network(f c ). Suppose that the k-th node of the original network is accessed by a grid-connected convertor, and the coupling frequency admittance model is

[0073]

[0074] The contribution of this grid-connected convertor to the extended node admittance matrix is: the [2k-1, 2k-1] element of the extended admittance matrix plus the [2k-1, 2k] element plus [2k,2k-1] elements plus [2k,2k] elements plus the branch of transmission line, transformer, etc. between the connected nodes k, m in the original network, in the network (f d ) and the accompanied network (f c ) without coupling terms, the admittance model is

[0075]

[0076] The branch of transmission line / transformer, etc. contributes to the extended node admittance matrix as follows: the [2k-1,2k-1], [2m-1,2m-1] elements of the extended admittance matrix plus [2k-1,2m-1], [2m-1,2k-1] elements minus [2k,2k], [2m,2m] elements plus [2k,2m], [2m,2k] elements minus

[0077] (2) Node frequency coupling admittance aggregation

[0078] As shown in Figure 2 , the to-be-researched node J of the network is injected with two groups of The KCL equation of the network extended node admittance matrix is calculated to obtain the voltages of the two groups of aggregated nodes J

[0079]

[0080]

[0081] Let the aggregated frequency coupling admittance of node J be

[0082]

[0083] Substitute the two groups of voltages and currents into The aggregated frequency coupling admittance of node J is:

[0084]

[0085] From the above analysis process, it can be seen that the aggregation calculation based on the extended node admittance matrix does not simplify the network element model. The aggregated frequency coupling admittance model of the to-be-researched node retains the sub- / ultra-synchronous frequency range dynamic characteristics of all grid-connected converters and network branches, and can accurately analyze the sub- / ultra-synchronous oscillation characteristics of the converter connected to the to-be-researched node.

[0086] Therefore, in the present application, the complexity of the actual power grid topology is first considered, the frequency coupling admittance / impedance aggregation method based on the network extended node admittance matrix is used to obtain the frequency coupling admittance / impedance of the multi-converter aggregation network and the system side network of the point of common coupling, form a single converter grid-connected system, simplify the multi-converter complex network, and then analyze the sub- / super-synchronous oscillation stability of the network.

[0087] Specifically, in combination with Figure 3 , the present application is described. Figure 3 The part outside the dashed line represents the multi-converter aggregation network, and the part inside the dashed line represents the converter and the grid-connected system. The aggregated frequency coupling admittance model Y eq_J (s) of the multi-converter aggregation network and the aggregated frequency coupling impedance model Z eq_J (s) of the system side network of the point of common coupling can be obtained by the frequency coupling admittance / impedance aggregation method based on the network extended node admittance matrix, both of which are 2×2 matrices, and are equivalent to a single converter grid-connected system.

[0088] The above method simplifies the multi-converter aggregation sending-out system into a single converter grid-connected system, which lays a foundation for improving the sub- / super-synchronous analysis efficiency of the grid-connected system. Moreover, the method does not reduce the order of the network element model, and retains the sub- / super-synchronous frequency range dynamic characteristics of all grid-connected converters and network branches.

[0089] The specific process is shown in Figure 4 , which starts by reading in the frequency coupling admittance 2×2 matrix model parameters of each grid-connected converter, each element being a frequency-admittance curve data, which is stored in the memory. Then, the model parameters of the network topology and the conventional elements such as transmission lines and transformers in the network are read in. According to the number of network nodes N, the order of the extended node admittance matrix is determined to be 2N×2N. The network to be studied and the grid-connected system are determined according to the actual requirements. The aggregated frequency coupling admittance model of the network to be studied and the aggregated frequency coupling impedance model of the system side network of the point of common coupling are obtained by the frequency coupling admittance / impedance aggregation method based on the network extended node admittance matrix, both of which are 2×2 matrices, and are equivalent to a single converter grid-connected system.

[0090] In step 102, the admittance matrix of the equivalent single converter grid-connected system is calculated based on the aggregated frequency coupling admittance model and the aggregated frequency coupling impedance model, and the eigenvalue trajectory of the admittance matrix of the equivalent single converter grid-connected system is determined.

[0091] Preferably, the calculation of the admittance matrix of the equivalent single converter grid-connected system based on the aggregated frequency coupling admittance model and the aggregated frequency coupling impedance model comprises:

[0092] L(s)=Y eq_J (s)Zeq_J (s),

[0093] wherein L(s) is an equivalent single converter grid-connection return ratio matrix; Y eq_J (s) is an aggregated frequency-coupled admittance model; Z eq_J (s) is an aggregated frequency-coupled impedance model; s is a Laplace operator.

[0094] In step 103, the sub / super-synchronous oscillation stability of the target multi-converter grid-connection system is evaluated based on the eigenvalue trajectory.

[0095] Preferably, wherein the sub / super-synchronous oscillation stability of the target multi-converter grid-connection system is evaluated based on the eigenvalue trajectory, comprising:

[0096] If the eigenvalue trajectory does not enclose (-1, 0) on the s-plane, it is determined that the sub / super-synchronous oscillation stability of the target multi-converter grid-connection system is stable; otherwise, if the eigenvalue trajectory encloses (-1, 0) on the s-plane, it is determined that the sub / super-synchronous oscillation stability of the target multi-converter grid-connection system is unstable.

[0097] In the present application, a wide-frequency oscillation stability analysis method based on the generalized Nyquist stability criterion is proposed for the equivalent single converter grid-connection system, to solve the problem of wide-frequency oscillation stability analysis of multi-converter complex network.

[0098] As shown in Figure 4 , for the equivalent single converter grid-connection system, the return ratio matrix eigenvalue root trajectory graph is calculated, and then the network stability characteristics are analyzed according to the generalized Nyquist stability criterion. Wherein, the return ratio matrix L(s) of the equivalent single converter grid-connection system of the multi-converter grid-connection system is Y eq_J (s)Z eq_J (s), if the two eigenvalues λ1(s), λ2(s) of L(s) do not enclose (-1, 0) on the s-plane, it is determined that the sub / super-synchronous oscillation of the grid-connection system presents stable characteristics; otherwise, if the trajectory encloses (-1, 0), it is determined that the sub / super-synchronous oscillation of the grid-connection system presents unstable characteristics.

[0099] The method provided by the present application is suitable for sub / super-synchronous oscillation characteristic analysis of multi-converter network, and has wide application prospect.

[0100] The following specific examples illustrate the embodiments of the present application

[0101] In the embodiments of the present application, the topological structure of Figure 3 is adopted, the converter and system element parameters are valued, and a 4-converter 4-node 35kV network is obtained. Figure 3In the circuit, the component parameters of branches 1-4 are L1=L2=L3=0.015H, R1=R2=R3=0.47Ω, L4=0.025H, and R4=0.78Ω, respectively. The VSC parameters are shown in Table 1. The parameters of VSC4 are the same as those of VSC1.

[0102] Table 1 VSC Parameter Table in the System

[0103]

[0104] The VSC1-3 connected to node 4 are aggregated, and the VSC4 connected to node 4 and the system Vs are aggregated to form an equivalent single-converter grid-connected system.

[0105] When SCR = 1.25 at node 3, as Figure 5 As shown, Figure 5 (a) is the root locus diagram of the system. Figure 5 (b) is a magnified view of the near region of point (-1,0). According to... Figure 5 It can be seen that the eigenvalue curves of the hysteresis matrix formed by the aggregation frequency coupling admittance of VSC1-3 on node 4 and the aggregation frequency coupling impedance of VSC4 and Zs on the system side are enclosed at (-1,0), exhibiting subsynchronous / supersynchronous oscillation instability characteristics.

[0106] In the electromagnetic transient model of the system, changing the system-side power supply impedance (SCR = 1.25) produces the following time-domain simulation waveform: Figure 6 As shown in (a), a subsynchronous / supersynchronous oscillation component appears in the branch current between nodes 3 and 4, such as Figure 6 As shown in (b), the frequencies of the oscillation components are 20.8 Hz and 79.2 Hz.

[0107] Figure 7 This is a schematic diagram of the subsynchronous / supersynchronous oscillation stability evaluation system 700 for a multi-converter network according to an embodiment of the present invention. Figure 7 As shown, the subsynchronous / supersynchronous oscillation stability evaluation system 700 for multi-converter networks provided in this embodiment of the invention includes: an equivalent unit 701, an eigenvalue trajectory determination unit 702, and a stability evaluation unit 703.

[0108] Preferably, the equivalent unit 701 is used to divide the target multi-converter network grid-connected system into a network under study and a grid connection point system according to requirements, and to obtain the aggregated frequency coupling admittance model of the network under study and the aggregated frequency coupling impedance model of the side network of the grid connection point system, respectively.

[0109] Preferably, the equivalent unit 701 obtains the aggregated frequency-coupled admittance model of the network under study and the aggregated frequency-coupled impedance model of the grid connection point system side node network, respectively, including:

[0110] The frequency coupling admittance aggregation method based on the network extended node admittance matrix obtains an aggregated frequency coupling admittance model of a network to be researched, and comprises the following steps:

[0111]

[0112] Y = I V eq_J is the aggregated frequency coupling admittance model of the network to be researched; I J is a flow vector injected into aggregated node J of the network to be researched; V J is a voltage vector of the aggregated node J of the network to be researched; is a transpose of V J .

[0113] The frequency coupling impedance aggregation method based on the network extended node admittance matrix obtains an aggregated frequency coupling impedance model of a system side network of a grid connection point, and comprises the following steps:

[0114]

[0115] Z = Y eq_J is the frequency coupling impedance model of the system side network of the grid connection point; Y eq_Jsys is the frequency coupling admittance model of the system side network of the grid connection point; I Jsys is a flow vector injected into node J of the system side network of the grid connection point; V Jsys is a voltage vector injected into node J of the system side network of the grid connection point; is a transpose of V Jsys .

[0116] Preferably, the eigenvalue trajectory determination unit 702 is configured to calculate an equivalent single converter grid-connected system return rate matrix based on the aggregated frequency coupling admittance model and the aggregated frequency coupling impedance model, and determine an eigenvalue trajectory of the equivalent single converter grid-connected system return rate matrix.

[0117] Preferably, the eigenvalue trajectory determination unit 702 is configured to calculate the equivalent single converter grid-connected system return rate matrix based on the aggregated frequency coupling admittance model and the aggregated frequency coupling impedance model, and determine an eigenvalue trajectory of the equivalent single converter grid-connected system return rate matrix.

[0118] L(s) = Y eq_J (s)Z eq_J (s),

[0119] L(s) = Y eq_J (s)Z eq_J (s) is the aggregated frequency coupling admittance model; Z eq_J (s) is the aggregated frequency coupling impedance model; and s is a Laplace operator.

[0120] Preferably, the stability evaluation unit 703 is configured to evaluate sub / super-synchronous oscillation stability of the target multi-inverter grid-connected system based on the eigenvalue trajectory.

[0121] Preferably, the stability evaluation unit 703 is configured to evaluate sub / super-synchronous oscillation stability of the target multi-inverter grid-connected system based on the eigenvalue trajectory, including:

[0122] If the eigenvalue trajectory does not enclose (-1, 0) in the s-plane, it is determined that the sub / super-synchronous oscillation stability of the target multi-inverter grid-connected system is stable; otherwise, if the eigenvalue trajectory encloses (-1, 0) in the s-plane, it is determined that the sub / super-synchronous oscillation stability of the target multi-inverter grid-connected system is unstable.

[0123] The multi-inverter network sub / super-synchronous oscillation stability evaluation system 700 of the embodiment of the present application corresponds to the multi-inverter network sub / super-synchronous oscillation stability evaluation method 100 of another embodiment of the present application, which will not be described here again.

[0124] Based on another aspect of the present application, the present application provides a computer readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any one of the multi-inverter network sub / super-synchronous oscillation stability evaluation methods.

[0125] Based on another aspect of the present application, the present application provides an electronic device, comprising:

[0126] The computer readable storage medium described above; and

[0127] One or more processors configured to execute the program in the computer readable storage medium.

[0128] The present application has been described by referring to a few embodiments. However, it is well understood by those skilled in the art that other embodiments, besides those disclosed above, are equivalent to the present application.

[0129] Generally, all terms used in the present application are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the [device, component, etc]" are to be interpreted openly as referring to one or more instances of the device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0130] Those skilled in the art will appreciate that embodiments of the application can be devised for a method, a system, or a computer program product. Accordingly, the present application can be embodied in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0131] The present application is described in reference to the flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams.

[0132] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams.

[0133] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams.

[0134] Finally, it should be noted that the above-mentioned embodiments are merely intended for describing the technical solutions of the present application, but not for limiting it. Although the present application has been described in detail with reference to the above-mentioned embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or equivalent replaced without departing from the spirit and scope of the present application, and any modification or equivalent replacement should be covered in the protection scope of the present application.

Claims

1. A method of sub / super synchronous oscillation stability assessment for a multi-converter network, characterized in that, The method comprises: According to the demand, the target multi-converter grid-connected system is divided into a network to be studied and a grid-connected point system, and an aggregated frequency-coupled admittance model of the network to be studied and an aggregated frequency-coupled impedance model of a section network of the grid-connected point system are obtained respectively; Based on the aggregated frequency-coupled admittance model and the aggregated frequency-coupled impedance model, an equivalent single-converter grid-connected system return rate matrix is calculated, and an eigenvalue locus of the equivalent single-converter grid-connected system return rate matrix is determined; Based on the eigenvalue locus, sub / super-synchronous oscillation stability of the target multi-converter grid-connected system is evaluated.

2. The method of claim 1, wherein, The aggregated frequency-coupled admittance model of the network to be studied and the aggregated frequency-coupled impedance model of the section network of the grid-connected point system are obtained respectively, comprising: Based on a frequency-coupled admittance aggregation method of a network extended node admittance matrix, the aggregated frequency-coupled admittance model of the network to be studied is obtained, comprising: where Y eq_J is the aggregated frequency-domain admittance model of the network under study; I J is the flow vector injected into the aggregated node J of the network under study, V J is the voltage vector of the aggregated node J of the network under study; is the transpose of V J . Based on a frequency-coupled impedance aggregation method of a network extended node admittance matrix, the aggregated frequency-coupled impedance model of the section network of the grid-connected point system is obtained, comprising: wherein Z eq_J is the frequency-coupled impedance model of the grid point system side network; Y eq_Jsys is the frequency-coupled admittance model of the grid point system side network; I Jsys is the flow vector injected into the grid point system side node J, V Jsys is the voltage vector injected into the grid point system side node J. is the transpose of V Jsys .

3. The method of claim 1, wherein, Based on the aggregated frequency-coupled admittance model and the aggregated frequency-coupled impedance model, the equivalent single-converter grid-connected system return rate matrix is calculated, comprising: L(s) = Y eq_J (s) Z eq_J (s), where L(s) is the equivalent single converter grid-connection admittance matrix; Y eq_J (s) is the aggregated frequency-coupled admittance model; Z eq_J (s) is the aggregated frequency-coupled impedance model; s is the Laplace operator.

4. The method of claim 1, wherein, Based on the eigenvalue locus, the sub / super-synchronous oscillation stability of the target multi-converter grid-connected system is evaluated, comprising: If the eigenvalue locus does not surround (-1, 0) on the s plane, it is determined that the sub / super-synchronous oscillation stability of the target multi-converter grid-connected system is stable; otherwise, if the eigenvalue locus surrounds (-1, 0) on the s plane, it is determined that the sub / super-synchronous oscillation stability of the target multi-converter grid-connected system is unstable.

5. A sub / super synchronous oscillation stability evaluation system for a multi-converter network, characterized by, The system comprises: An equivalent unit is configured to divide, according to the demand, a target multi-converter grid-connected system into a network to be studied and a grid-connected point system, and obtain an aggregated frequency-coupled admittance model of the network to be studied and an aggregated frequency-coupled impedance model of a section network of the grid-connected point system respectively; An eigenvalue locus determination unit is configured to calculate, based on the aggregated frequency-coupled admittance model and the aggregated frequency-coupled impedance model, an equivalent single-converter grid-connected system return rate matrix, and determine an eigenvalue locus of the equivalent single-converter grid-connected system return rate matrix; A stability evaluation unit is configured to evaluate, based on the eigenvalue locus, sub / super-synchronous oscillation stability of the target multi-converter grid-connected system.

6. The system of claim 5, wherein, The equivalent unit is configured to obtain the aggregated frequency-coupled admittance model of the network to be studied and the aggregated frequency-coupled impedance model of the section network of the grid-connected point system respectively, comprising: The equivalent unit is configured to obtain the aggregated frequency-coupled admittance model of the network to be studied based on a frequency-coupled admittance aggregation method of a network extended node admittance matrix, comprising: where Y eq_J is the aggregated frequency-domain admittance model of the network under study; I J is the flow vector injected into the aggregated node J of the network under study, V J is the voltage vector of the aggregated node J of the network under study; is the transpose of V J ; The equivalent unit is configured to obtain the aggregated frequency-coupled impedance model of the section network of the grid-connected point system based on a frequency-coupled impedance aggregation method of a network extended node admittance matrix, comprising: wherein Z eq_J is the frequency-coupled impedance model of the grid point system side network; Y eq_Jsys is the frequency-coupled admittance model of the grid point system side network; I Jsys is the current vector injected into the grid point system side node J, V Jsys is the voltage vector injected into the grid point system side node J. is the transpose of V Jsys .

7. The system of claim 5, wherein, The eigenvalue locus determination unit is configured to calculate, based on the aggregated frequency-coupled admittance model and the aggregated frequency-coupled impedance model, the equivalent single-converter grid-connected system return rate matrix, comprising: L(s) = Y eq_J (s) Z eq_J (s), where L(s) is the equivalent single converter grid-connection admittance matrix; Y eq_J (s) is the aggregated frequency-coupled admittance model; Z eq_J (s) is the aggregated frequency-coupled impedance model; s is the Laplace operator.

8. The system of claim 5, wherein, The stability evaluation unit is configured to evaluate, based on the eigenvalue locus, the sub / super-synchronous oscillation stability of the target multi-converter grid-connected system, comprising: If the eigenvalue trajectory does not enclose (-1, 0) on the s-plane, it is determined that the sub / super-synchronous oscillation stability of the target multi-converter grid-connected system is stable; otherwise, if the eigenvalue trajectory encloses (-1, 0) on the s-plane, it is determined that the sub / super-synchronous oscillation stability of the target multi-converter grid-connected system is unstable.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program, when executed by the processor, implements the steps of the method of any one of claims 1-4.

10. An electronic device, comprising: comprising: the computer readable storage medium of claim 9; and one or more processors for executing the program in the computer readable storage medium.

Images