Dynamic simplification and simulation method for multi-source access power grid equivalent network model

Abstract

The invention relates to a dynamic simplification and simulation method for a multi-source access power grid equivalent network model, and the method comprises the following steps: S1, building an original network model based on time domain Kron simplification, carrying out the simplification to obtain an equivalent network connection relation and connection parameters, and obtaining an equivalent network model; s2, performing differential modeling on elements according to the equivalent network model, adding power electronic switch device branches into an equivalent network, and establishing a full-equivalent network historical current source matrix and a full-equivalent network admittance matrix; s3, performing parallel calculation on the state of the power electronic switch device, and refreshing the full-equivalent network admittance matrix according to a calculation result; and S4, calculating an equivalent network state quantity according to the full-equivalent network historical current source matrix, the full-equivalent network admittance matrix and the equivalent network boundary conditions. The method has the beneficial effects of reducing distribution network model scale and improving calculation and analysis speed.

Description

Technical field

[0001] The present invention relates to the technical field of power system computer simulation, and in particular to a method for dynamically simplifying and simulating a multi-source access power grid equivalent network model. [Background Technology]

[0002] With the advancement of power transmission and distribution technology, power grids have evolved from their initial "small-scale balancing" to today's multi-regional interconnected systems. Multi-regional interconnection offers advantages such as improved power supply reliability and a higher proportion of clean energy consumption. However, the large number of nodes in these interconnected large-scale grids is prohibitive. Analyzing these large-scale grids using a comprehensive, detailed model would require enormous storage and computational resources, making the computational time prohibitively expensive. Therefore, network equivalence technology is a crucial topic in the development of modern large-scale interconnected systems.

[0003] However, traditional network topology simplification methods typically rely on static simplification, achieving high simplification and equivalent accuracy only under single-frequency, steady-state sinusoidal excitation. With the development of new energy and the dual-carbon goals, an increasing number of renewable energy sources are being connected to the grid as distributed power sources. These renewable energy sources are typically connected to the grid via power electronic converters, introducing higher harmonic content into the distribution network. High-frequency harmonics account for a higher proportion in new power systems than in traditional grids, and the equivalent errors caused by these high-frequency components in static simplification are not negligible.

[0004] The existing time-domain Kron simplification method is a dynamic simplification. However, this type of method does not limit the selection of zero-space basis vectors during the simplification process, resulting in an unclear physical model obtained by simplification. Therefore, it is difficult to apply the existing electromagnetic transient simulation algorithm to solve the equivalent network.

[0005] Among existing network topology simplification methods, classic Kron simplification is only applicable to static scenarios, instantaneous Kron simplification is only applicable to homogeneous networks, and time-domain Kron simplification is applicable to dynamic, heterogeneous networks. However, these methods are difficult to apply without corresponding physical models. In the case of multi-source access distribution networks, model equivalence must preserve the model's dynamic characteristics. However, due to the complexity of multi-source access, models are often analyzed using simulation algorithms. Therefore, no existing network topology simplification methods are applicable to multi-source access distribution network models. Therefore, finding a dynamic network simplification method with a clear physical model and applicable to dynamic situations is of great practical significance.

[0006] The present invention aims to solve the technical problem that the physical model obtained by the time domain Kron simplification method is not clear enough and it is difficult to use the existing electromagnetic transient simulation algorithm to solve the equivalent network. The invention makes technical improvements to the dynamic simplification and simulation method of the equivalent model of multi-source access to the power grid transmission and distribution. [Summary of the invention]

[0007] The purpose of the present invention is to provide a method for dynamically simplifying and simulating a multi-source access power grid transmission and distribution equivalent model, which can reduce the scale of the distribution network model and improve the calculation and analysis speed.

[0008] To achieve the above-mentioned object, the technical solution adopted by the present invention is a method for dynamically simplifying and simulating a network model equivalent to a multi-source access grid, wherein the multi-source access grid includes a plurality of renewable energy sources connected in the form of distributed power sources, and the renewable energy sources are connected to the grid via power electronic switching devices; the method comprises the following steps:

[0009] S1. Based on the time-domain Kron simplification, the original network model of multi-source access to the power grid is established, and the equivalent network connection relationship and connection parameters are obtained by simplification, thereby obtaining the equivalent network model of multi-source access to the power grid;

[0010] S2. Based on the multi-source access grid equivalent network model, perform differential modeling on the components, add the power electronic switch device branch to the multi-source access grid equivalent network, and establish the full multi-source access grid equivalent network historical current source matrix and full multi-source access grid equivalent network admittance matrix;

[0011] S3, parallel calculation of the states of power electronic switching devices, and updating the equivalent network admittance matrix of the full multi-source access grid according to the calculation results;

[0012] S4. Calculate the state quantity of the multi-source access grid equivalent network according to the historical current source matrix of the full multi-source access grid equivalent network, the admittance matrix of the full multi-source access grid equivalent network and the boundary conditions of the multi-source access grid equivalent network.

[0013] Preferably, step S1: the branch of the equivalent network model of the multi-source access power grid ignores the line-to-ground conductance and the line-to-ground susceptance, and is simplified to a series circuit of resistance and inductance.

[0014] Preferably, step S1 specifically includes the following sub-steps:

[0015] S11, establishing a node-branch association matrix B, an inductance matrix L, and a resistance matrix R of the original network model of the multi-source access power grid according to the input topology and network parameters of the original network model of the multi-source access power grid;

[0016] S12, divide the nodes of the original network model of multi-source access to the power grid into reducible nodes and irreducible nodes, and convert the node-branch association matrix of the original network model of multi-source access to the power grid into a matrix of nodes and branches. . It is divided into reducible node-branch correlation matrix B0 and irreducible node-branch correlation matrix B1.

[0017] S13, simplify the multi-source access grid network and calculate the simplified node-branch correlation matrix B of the multi-source access grid equivalent network model red , simplified inductance matrix Lred , simplified resistance matrix R red .

[0018] Preferably, step S11:

[0019] Elements in the node-branch association matrix B Where b ib is the element in the i-th row and b-th column of the node-branch association matrix B;

[0020] The inductance matrix L is a diagonal matrix, and its diagonal elements l bb =L b , where l bb is the element in the bth row and bth column of the inductance matrix L, L b is the inductance of branch b;

[0021] The resistance matrix R is a diagonal matrix with diagonal elements r bb =R b , where r bb is the element in the bth row and bth column of the resistance matrix R, R b is the resistance value of branch b.

[0022] Preferably, step S12:

[0023] The reducible node is a zero-input node. In addition to being connected to the network line, it is no longer connected to other voltage sources or current sources, and has no injected current or output current.

[0024] The irreducible node is connected to at least one voltage source or current source, and has injected current or output current;

[0025] The reducible node-branch association matrix B0 is the reducible node-related rows in the node-branch association matrix B, and the irreducible node-branch association matrix B1 is the irreducible node-related rows in the node-branch association matrix B.

[0026] Preferably, step S13:

[0027] The injected current of the reducible node is 0, B0f=0, where B0 is the reducible node-branch correlation matrix, and f is the branch current column vector;

[0028] Let f be expressed as follows Where f is the branch current column vector, P is the B0 null space basis vector, is the column vector of reducible branch current;

[0029] Reduced node-branch association matrix B red =B1P, where B1 is the irreducible node-branch incidence matrix and P is the null space basis vector of B0;

[0030] Simplified inductance matrix L red =P T LP, where L is the inductance matrix, P is the B0 null space basis vector, and P T is the transposed matrix of P;

[0031] Simplified resistance matrix R red =P T RP, where R is the resistance matrix; P is the B0 null space basis vector, P T is the transposed matrix of P.

[0032] Preferably, step S2:

[0033] Equivalent network equations of multi-source access to power grid in differential form Where B red is the reduced node-branch correlation matrix, v1 is the irreducible node voltage column vector, R red is the simplified resistance matrix, L red is the simplified inductance matrix, is the column vector of reducible branch current;

[0034] Differentiate the derivatives of the reducible branch current column vectors Where dt is the simulation calculation time interval, and are the reducible branch current column vectors at time t and time (t-dt) respectively;

[0035] Substitute the differential formula of the reducible branch current column vector derivative into the equivalent network equation of the multi-source access power grid Where I1(t) is the column vector of the irreducible node injection current at time t, B red is the reduced node-branch correlation matrix, v1(t) is the irreducible node voltage column vector at time t, R red is the simplified resistance matrix, L red is the simplified inductance matrix, is the reducible branch current column vector at time (t-dt);

[0036] The equivalent network equation of multi-source access to the power grid after differentiation is expressed as: Where H his is the historical current matrix, Y eq is the network admittance matrix;

[0037] Historical current matrix

[0038] Network admittance matrix

[0039] Add the power electronic switch device branch to the multi-source access grid equivalent network, and the full multi-source access grid equivalent network resistance matrix Full multi-source access to the grid equivalent network inductance matrix Where R e is the diagonal array of branch resistances of power electronic switching devices;

[0040] Equivalent network historical current matrix of full multi-source access to the power grid

[0041] Equivalent network admittance matrix of full multi-source access to the power grid

[0042] Accordingly, the node-branch correlation matrix B needs to be augmented according to the connection properties of the power electronic switching devices to obtain the equivalent network node-branch correlation matrix B of the full multi-source access grid a ;

[0043] The equivalent network equation of full multi-source access to the power grid is obtained

[0044] Preferably, step S3:

[0045] Power electronic switching device branch power electronic switching device switching state resistance

[0046]

[0047] The corresponding diagonal elements of the power electronic switching devices in the inductance matrix of the fully multi-source access grid equivalent network are 0, so the historical current matrix of the fully multi-source access grid equivalent network will not change every time the switching state of the power electronic switching devices changes;

[0048] The change of the equivalent network admittance matrix of the full multi-source access grid when the switching state of the power electronic switching device changes is: Where, is the equivalent network admittance matrix Y after the change of full multi-source access grid a The element in row b and column b, is the equivalent network admittance matrix Y of the full multi-source access grid before the change a The element in row b and column b, Δy a,bb is the equivalent network admittance matrix Y of the full multi-source access grid a The change in the element in row b and column b,

[0049] Preferably, step S4:

[0050] In the equivalent network node state of multi-source access power grid, some nodes are voltage source nodes, the voltage of the voltage source node is a known quantity and the injected current is an unknown quantity, and some nodes are intermediate nodes, the current of the intermediate node is a known quantity and the voltage is an unknown quantity;

[0051] The unknown quantities of the multi-source access power grid equivalent network are calculated according to the full multi-source access power grid equivalent network equation.

[0052] The present invention provides a dynamic simplification and simulation method for an equivalent network model of a multi-source access power grid, which has the following beneficial effects: the network topology simplification method of the present invention inherits the advantage of time-domain Kron simplification being applicable to dynamic and inhomogeneous networks, while limiting the method for selecting the null space basis vectors therein, thereby obtaining a network dynamic simplification method that is applicable to dynamic and inhomogeneous networks and can obtain a physical model; the present invention mainly accelerates the simulation calculation of a multi-source access distribution network through two key steps: network dynamic simplification and parallel calculation of power electronic switching devices. The network dynamic simplification reduces the scale of network nodes, and the parallel calculation of power electronic switching devices accelerates the refreshing of controller results; the present invention can reduce the scale of power grid nodes, reduce the order of the calculation matrix of the multi-source access distribution network, accelerate the simulation speed of the distribution network system, and provide a basis for the safe and stable operation of the distribution network system and the transient fault analysis.

Brief Description of the Drawings

[0053] Figure 1 The present invention is a flow chart of a dynamic simplification and simulation method of an equivalent network model of multi-source access to a power grid.

[0054] Figure 2 The invention is a branch model diagram of a dynamic simplification and simulation method of an equivalent network model of a multi-source access power grid.

[0055] Figure 3 The invention relates to a network simplification diagram of a dynamic simplification and simulation method of an equivalent network model of a multi-source access power grid. [Specific implementation method]

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0057] Example

[0058] This embodiment implements a method for dynamically simplifying and simulating a multi-source access power grid equivalent network model.

[0059] Figure 1 This is a flow chart of a dynamic simplification and simulation method for a multi-source access power grid equivalent network model. Figure 1 As shown, the specific implementation is mainly divided into four steps, namely: 1. Obtaining the equivalent network connection relationship and connection parameters, 2. Establishing the historical current source matrix and the admittance matrix of the entire network, 3. Calculating the power electronic switch state and refreshing the admittance matrix of the entire network, 4. Calculating the network state quantity.

[0060] Specifically,

[0061] Step 1: Based on time-domain Kron simplification, a simplified network model is established to obtain equivalent network connection relationships and connection parameters.

[0062] Figure 2 It is a branch model diagram of a dynamic simplification and simulation method of a multi-source access power grid equivalent network model. Figure 2 As shown, this embodiment ignores the line conductance and susceptance to ground, and considers the network line to be a simple segment line model, specifically a resistor and an inductor connected in series.

[0063] 1A. Based on the input original model network topology and network parameters, establish the original model node-branch association matrix B, inductance matrix L, and resistance matrix R.

[0064] The elements in the node-branch association matrix B are:

[0065]

[0066] Where b ib is the element in the i-th row and b-th column of the node-branch association matrix B.

[0067] The inductance matrix L is a diagonal matrix with the following diagonal elements:

[0068] l bb =L b

[0069] Where, l bb is the element in the bth row and bth column of the inductance matrix L; L b is the inductance of branch b. The resistance matrix R is a diagonal matrix with the following diagonal elements:

[0070] r bb =R b

[0071] Where r bb is the element in the bth row and bth column of the resistance matrix R; R b is the resistance value of branch b.

[0072] 1B. Divide the nodes in the original model into reducible nodes and irreducible nodes, and divide the node-branch association matrix of the original model into the reducible node-branch association matrix B0 and the irreducible node-branch association matrix B1.

[0073] The reducible node is a zero-input node, that is, the node is not connected to any other voltage source or current source except for being connected to the network line, and has no injected current or output current.

[0074] On the contrary, an irreducible node is connected to at least one voltage source or current source, and has either injected current or output current.

[0075] The reducible node-branch association matrix B0 is the reducible node-related rows in the node-branch association matrix B; the irreducible node-branch association matrix B1 is the irreducible node-related rows in the node-branch association matrix B.

[0076] 1C. Figure 3 This is a network simplified diagram of a dynamic simplification and simulation method for a multi-source access power grid equivalent network model. Figure 3 As shown, in this embodiment, the network is simplified and the simplified node-branch association matrix B of the equivalent model is calculated. red , simplified inductance matrix L red , simplified resistance matrix R red .

[0077] Since the injected current of the simplified node is 0, the following equation holds true.

[0078] B0f=0

[0079] Where B0 is the reducible node-branch association matrix; f is the branch current column vector.

[0080] Therefore, f can be expressed as follows:

[0081]

[0082] Where f is the branch current column vector; P is the B0 null space basis vector, which is obtained by Gaussian elimination. When it is the radical amplitude, only a single radical is assigned a non-zero value of 1 or -1 each time, and the rest of the radicals are assigned to 0. is the column vector of the reduced branch current.

[0083] Reduced node-branch association matrix B red for:

[0084] B red =B1P

[0085] Where B1 is the irreducible node-branch incidence matrix; P is the null space basis vector of B0.

[0086] Simplified inductance matrix L red for:

[0087] L red =PT LP

[0088] Where L is the inductance matrix; P is the B0 null space basis vector, P T is the transposed matrix of P.

[0089] Simplified resistance matrix R red for:

[0090] R red =P T RP

[0091] Where R is the resistance matrix; P is the B0 null space basis vector, P T is the transposed matrix of P.

[0092] Step 2: Based on the equivalent network model, perform differential modeling on the components and establish the historical current source matrix and the admittance matrix of the entire network.

[0093] 2A. Differential circuit components.

[0094] The network equation in differential form is:

[0095]

[0096] Where B red is the reduced node-branch correlation matrix; v1 is the irreducible node voltage column vector; R red is the simplified resistance matrix; L red is the simplified inductance matrix; is the column vector of the reduced branch current.

[0097] After differentiating the derivatives of the reduced branch current column vector, we can obtain:

[0098]

[0099] Where dt is the simulation calculation time interval, and are the reduced branch current column vectors at time t and time (t-dt) respectively.

[0100] Substituting the above formula into the network equation, we can get:

[0101]

[0102] Where I1(t) is the column vector of the irreducible node injection current at time t; B red is the reduced node-branch correlation matrix; v1(t) is the irreducible node voltage column vector at time t; R red is the simplified resistance matrix; L red is the simplified inductance matrix; is the column vector of the simplified branch current at time (t-dt).

[0103] 2B. Establish the historical current source matrix and the admittance matrix of the entire network.

[0104] The above-mentioned differential network formula can be expressed as:

[0105]

[0106] Where H his is the historical current matrix; Y eq is the network admittance matrix.

[0107] Therefore, the historical current matrix H can be obtained his for:

[0108]

[0109] The network admittance matrix is:

[0110]

[0111] Add the switch branch to the network to form the full network resistance matrix R a , the full network inductance matrix L a .

[0112] The full network resistance matrix is:

[0113]

[0114] Where R e It is the diagonal array of control branch resistance of power electronic switching devices.

[0115] The full network inductance matrix is:

[0116]

[0117] Therefore, the historical current matrix H of the entire network can be obtained a and the full network admittance matrix Y a .

[0118] The historical current matrix H of the entire network a for:

[0119]

[0120] Full network admittance matrix Y a for:

[0121]

[0122] Correspondingly, the node-branch correlation matrix also needs to be augmented according to the connection properties of the power electronic switches to obtain the node-branch correlation matrix B of the entire network a .

[0123] The full network equation is:

[0124]

[0125] Step 3: Perform parallel calculations on the states of the power electronic switching devices and update the full network admittance matrix based on the calculation results.

[0126] 3A. Because the internal calculations of each converter controller are relatively independent, parallel computing can be used for each converter controller. After parallel computing, the switching status of each power electronic switching device can be obtained.

[0127] In a distribution network with multiple sources connected, the network admittance matrix must consider not only the network nodes themselves but also the switching states of the switching devices. When the switch is on, it can be seen as a branch with extremely low resistance; when the switch is off, it can be seen as a branch with extremely high resistance. Therefore, the resistance of the branch controlled by the power electronic switching device is:

[0128]

[0129] 3B. Update the full network admittance matrix based on the calculated switch states.

[0130] Since the corresponding diagonal elements of the power electronic switching devices in the full network inductance matrix are 0, the full network historical current matrix will not change each time the switch state changes.

[0131] The change of the full network admittance matrix when the switch state changes is:

[0132]

[0133] Where, is the changed admittance matrix Y of the entire network a The element in row b and column b; is the full network admittance matrix Y before the change a The element in row b and column b; Δy a,bb is the admittance matrix Y of the entire network a The amount by which the element in row b and column b changes.

[0134] Where Δy a,bb for:

[0135]

[0136] Step 4: Calculate the network state quantity based on the historical current source matrix of the entire network, the admittance matrix of the entire network and the network boundary conditions.

[0137] In the node state, some nodes are voltage source nodes, that is, the node voltage is a known quantity and the node injection current is an unknown quantity; some nodes are intermediate nodes, that is, the node current is a known quantity and the node voltage is an unknown quantity.

[0138] The unknown state quantities of the network are calculated based on the full network equation.

[0139] In the case of multi-source access distribution networks, model equivalence needs to preserve the dynamic characteristics of the model. At the same time, due to the complexity of multi-source access, the model is often analyzed using simulation algorithms. The method of this embodiment inherits the advantage of time-domain Kron simplification for dynamic and heterogeneous networks, while limiting the selection method of the null space basis vectors, thereby obtaining a network dynamic simplification method that is applicable to dynamic and heterogeneous networks and can also obtain a physical model. Based on the above network simplification method, this embodiment designs a set of equivalent modeling and simulation methods suitable for multi-source access distribution networks.

[0140] The multi-source access distribution network equivalent model and simulation method of this embodiment with dynamic network simplification mainly accelerate the simulation calculation of the multi-source access distribution network through two key steps, namely dynamic network simplification and parallel calculation of power electronic switching devices. Dynamic network simplification reduces the scale of network nodes, and parallel calculation of power electronic switching devices accelerates the refresh of controller results.

[0141] Those skilled in the art will appreciate that all or part of the steps for implementing the above embodiments may be accomplished by hardware, or may be accomplished by a program instructing the relevant hardware, and the program may be stored in a computer-readable storage medium, wherein the storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0142] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the principles of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for dynamically simplifying and simulating a network model equivalent to a multi-source access grid, wherein the multi-source access grid includes a plurality of renewable energy sources connected in the form of distributed power sources, and the renewable energy sources are connected to the grid via power electronic switching devices; The following steps are involved: S1. Based on the time-domain Kron simplification, the original network model of multi-source access to the power grid is established, and the equivalent network connection relationship and connection parameters are obtained by simplification, thereby obtaining the equivalent network model of multi-source access to the power grid; S2. Based on the multi-source access grid equivalent network model, perform differential modeling on the components, add the power electronic switch device branch to the multi-source access grid equivalent network, and establish the full multi-source access grid equivalent network historical current source matrix and full multi-source access grid equivalent network admittance matrix; S3, parallel calculation of the states of power electronic switching devices, and updating the equivalent network admittance matrix of the full multi-source access grid according to the calculation results; S4. Calculate the state quantity of the multi-source access grid equivalent network according to the historical current source matrix of the full multi-source access grid equivalent network, the admittance matrix of the full multi-source access grid equivalent network and the boundary conditions of the multi-source access grid equivalent network.

2. A method for dynamic simplification and simulation of a multi-source access grid equivalent network model according to claim 1, characterized in that Step S1: The branch of the equivalent network model of the multi-source access power grid ignores the line-to-ground conductance and ground susceptance, and is simplified to a series circuit of resistance and inductance.

3. A method for dynamic simplification and simulation of a multi-source access grid equivalent network model according to claim 2, characterized in that Step S1 specifically includes the following sub-steps: S11, establishing a node-branch association matrix B, an inductance matrix L, and a resistance matrix R of the original network model of the multi-source access power grid according to the input topology and network parameters of the original network model of the multi-source access power grid; S12. Divide the nodes of the original network model of the multi-source access power grid into reducible nodes and irreducible nodes, and divide the node-branch association matrix B of the original network model of the multi-source access power grid into a reducible node-branch association matrix B0 and an irreducible node-branch association matrix B1. S13, simplify the multi-source access grid network and calculate the simplified node-branch correlation matrix B of the multi-source access grid equivalent network model red , simplified inductance matrix L red , simplified resistance matrix R red .

4. A method for dynamic simplification and simulation of a multi-source access grid equivalent network model according to claim 3, characterized in that Step S11: Elements in the node-branch association matrix B Where b ib is the element in the i-th row and b-th column of the node-branch association matrix B; The inductance matrix L is a diagonal matrix, and its diagonal elements l bb =L b , where l bb is the element in the bth row and bth column of the inductance matrix L, L b is the inductance of branch b; The resistance matrix R is a diagonal matrix with diagonal elements r bb =R b , where r bb is the element in the bth row and bth column of the resistance matrix R, R b is the resistance value of branch b.

5. A method for dynamic simplification and simulation of a multi-source access grid equivalent network model according to claim 4, characterized in that Step S12: The reducible node is a zero-input node. In addition to being connected to the network line, it is no longer connected to other voltage sources or current sources, and has no injected current or output current. The irreducible node is connected to at least one voltage source or current source, and has injected current or output current; The reducible node-branch association matrix B0 is the reducible node-related rows in the node-branch association matrix B, and the irreducible node-branch association matrix B1 is the irreducible node-related rows in the node-branch association matrix B.

6. A method for dynamic simplification and simulation of a multi-source access grid equivalent network model according to claim 5, characterized in that Step S13: The injected current of the reducible node is 0, B0f=0, where B0 is the reducible node-branch correlation matrix, and f is the branch current column vector; Let f be expressed as follows Where f is the branch current column vector, P is the B0 null space basis vector, is the column vector of reducible branch current; Reduced node-branch association matrix B red =B1P, where B1 is the irreducible node-branch incidence matrix and P is the null space basis vector of B0; Simplified inductance matrix L red =P T LP, where L is the inductance matrix, P is the B0 null space basis vector, and P T is the transposed matrix of P; Simplified resistance matrix R red =P T RP, where R is the resistance matrix; P is the B0 null space basis vector, P T is the transposed matrix of P.

7. A method for dynamic simplification and simulation of a multi-source access grid equivalent network model according to claim 6, characterized in that Step S2: Equivalent network equations of multi-source access to power grid in differential form Where B red is the reduced node-branch correlation matrix, v1 is the irreducible node voltage column vector, R red is the simplified resistance matrix, L red is the simplified inductance matrix, is the column vector of reducible branch current; Differentiate the derivatives of the reducible branch current column vectors Where, dt is the simulation calculation time interval, and are the reducible branch current column vectors at time t and time (t-dt) respectively; Substitute the differential formula of the reducible branch current column vector derivative into the equivalent network equation of the multi-source access power grid Where I1(t) is the column vector of the irreducible node injection current at time t, B red is the reduced node-branch correlation matrix, v1(t) is the irreducible node voltage column vector at time t, R red is the simplified resistance matrix, L red is the simplified inductance matrix, is the reducible branch current column vector at time (t-dt); The equivalent network equation of multi-source access to the power grid after differentiation is expressed as: Where H his is the historical current matrix, Y eq is the network admittance matrix; Historical current matrix Network admittance matrix Add the power electronic switch device branch to the multi-source access grid equivalent network, and the full multi-source access grid equivalent network resistance matrix Full multi-source access to the grid equivalent network inductance matrix Where R e is the diagonal array of branch resistances of power electronic switching devices; Equivalent network historical current matrix of full multi-source access to the power grid Equivalent network admittance matrix of full multi-source access to the power grid Accordingly, the node-branch correlation matrix B needs to be augmented according to the connection properties of the power electronic switching devices to obtain the equivalent network node-branch correlation matrix B of the full multi-source access grid a ; The equivalent network equation of full multi-source access to the power grid is obtained 8. A method for dynamic simplification and simulation of a multi-source access grid equivalent network model according to claim 7, characterized in that Step S3: Power electronic switching device branch power electronic switching device switching state resistance The corresponding diagonal elements of the power electronic switching devices in the inductance matrix of the fully multi-source access grid equivalent network are 0, so the historical current matrix of the fully multi-source access grid equivalent network is a The secondary power electronic switching device will not change when the switching state changes; The change of the equivalent network admittance matrix of the full multi-source access grid when the switching state of the power electronic switching device changes is: Where, is the b-th row and b-th column element of the modified network admittance matrix of the fully multi-source access grid, is the equivalent network admittance matrix Y of the full multi-source access grid before the change a The element in row b and column b, Δy a,bb is the equivalent network admittance matrix Y of the full multi-source access grid a The change in the element in row b and column b, 9. A method for dynamic simplification and simulation of a multi-source access grid equivalent network model according to claim 8, characterized in that Step S4: In the equivalent network node state of multi-source access power grid, some nodes are voltage source nodes, the voltage of the voltage source node is a known quantity and the injected current is an unknown quantity, and some nodes are intermediate nodes, the current of the intermediate node is a known quantity and the voltage is an unknown quantity; The unknown quantities of the multi-source access power grid equivalent network are calculated according to the full multi-source access power grid equivalent network equation.

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