Design Method of Control Parameters for VSG Grid-Connected System Oriented to Grid Stability and Frequency Support

Abstract

A VSG grid-connected system control parameter design method for grid stability and frequency support belongs to the field of power system automation control technology, and solves the problem of the influence of active frequency support control of renewable energy power generation on the stability of the power system; the present invention establishes a small signal model for the grid-connected inverter, virtual synchronous generator control link and other control links; adopts the eigenvalue analysis method according to the small signal model to obtain the stability range of each control parameter; establishes a frequency response model of the VSG grid-connected system, analyzes the control parameters related to the frequency support capability, and obtains the constraint range of the control parameters according to the frequency regulation requirements; combines the stability range of each control parameter obtained by the eigenvalue analysis method, and finally obtains the value range of all parameters after intersection; the method of the present invention takes into account both frequency support capability and system stability, and can be directly used for parameter design under VSG control in the form of photovoltaic power generation systems, wind turbines, energy storage systems, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system automation control, and relates to a VSG grid-connected system control parameter design method for grid stability and frequency support. Background Art

[0002] As the installed capacity of my country's renewable energy power generation systems continues to increase, when large-scale renewable energy sources such as wind power and photovoltaics are connected to traditional power grids, the renewable energy power generation systems often operate in maximum power point mode, unable to provide frequency regulation support to the grid, which has a significant impact on the stable operation of the power system. Therefore, it is crucial to study the technology of actively supporting grid frequency stability with renewable energy power generation systems. However, the premise of active frequency support control for large-scale renewable energy power generation systems is to ensure the safe operation of the entire power system. Existing studies have shown that active frequency support control for renewable energy power generation can affect the stability of the power system. Therefore, it is necessary to develop a parameter design method that can balance frequency support capability and system stability. Summary of the Invention

[0003] The present invention is used to solve the problem of the influence on the stability of the power system when the new energy power generation performs active frequency support control.

[0004] The present invention solves the above technical problems through the following technical solutions:

[0005] A VSG grid-connected system control parameter design method for grid stability and frequency support includes the following steps:

[0006] S1. Establish small signal models for the grid-connected inverter main circuit, VSG control link, power calculation link, virtual impedance link, and voltage and current control link; integrate the small signal models of each link to obtain the state space matrix of the VSG grid-connected system;

[0007] S2. Based on the state space matrix, the eigenvalue analysis method is used to calculate the eigenvalues of the characteristic matrix, and the stability of the system at this time is determined. The participation factor of the characteristic matrix is calculated to obtain the influencing parameters of each oscillation mode of the system;

[0008] S3. Under the premise of system stability, by changing the influencing parameters of each oscillation mode one by one, the corresponding eigenvalue trajectory diagram is drawn. According to the eigenvalue trajectory diagram, the boundary value where the real part of the eigenvalue is less than 0 is obtained. The corresponding control parameter is the boundary value of system stability, thereby obtaining the stable range of each control parameter;

[0009] S4. Establish a frequency response model for the VSG grid-connected system, derive control parameters related to frequency support capability, and derive constraint ranges for the control parameters based on frequency regulation requirements;

[0010] S5. Combining the stability range of each control parameter obtained by the eigenvalue analysis method with the constraint range of the frequency support, the intersection is taken to finally obtain the value range of all parameters and complete the parameter design.

[0011] Furthermore, the method for establishing the small signal model of the grid-connected inverter main circuit, VSG control link, power calculation link, virtual impedance link, and voltage and current control link described in step S1 is as follows:

[0012] S11. Use n first-order nonlinear ordinary differential equations to describe the state space equations of the grid-connected inverter main circuit and VSG control link, power calculation link, virtual impedance link, and voltage and current control link, specifically:

[0013]

[0014] Where x=[x1,x2,…,x n ] T is the state variable of the system, the constant n is the number of state variables of the system, that is, the order of the system, u=[u1,u2,…,u r ] T is the input quantity of the system, the constant r is the number of system input quantities, and f() is the differential quantity describing the system state variable A function that relates to the system state variable x and the system input u;

[0015] S12. Linearize the state space equation at the system steady-state point to obtain the corresponding small signal model, which is:

[0016]

[0017] Where Δx is the disturbance of the state variable, is the differential corresponding to the disturbance, matrix A is the system state space matrix, Δu is the disturbance input to the system, and matrix B is the input coefficient matrix.

[0018] Furthermore, the state space matrix of the VSG grid-connected system described in step S1 is:

[0019] A=[l1 l2 l3 l4 l5 l6 l7 l8 l9 l 10 l 11 l 12 l 13 l 14 ] T (3)

[0020] Where l1…l 14 is the corresponding matrix row vector, and its specific expression is:

[0021]

[0022]

[0023] l3=[0 0 -ω c 0 0 0 1.5h c I od 1.5h c I oq 1.5h c U od 1.5h c U oq 0 0 0 0];

[0024] l4=[0 0 0 -ω c 0 0 -1.5h c I oq 1.5h c I od 1.5h c U oq -1.5h c U od 0 0 0 0];

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031] l 11 =[I oq L v 1 0 0 0 0 -1 0 -r v oh n L v 0 0 0 0];

[0032] l 12 =[-I od L v 0 0 0 0 0 0 -1 -ω n L v -r v 0 0 0 0];

[0033] l 13 =[Ioq L v K Pv K Pv 0 0 -1 0 -K Pv -ω n C f -r v K Pv +1 K Pv L v ω n K iv 0 0 0];

[0034] l 14 =[-I od L v K Pv 0 0 0 0 -1 ω n C f -K Pv K Pv L v ω n -r v K Pv +1 0 K iv 0 0];

[0035] Where, K p is the frequency modulation coefficient, J is the inertia constant, D is the damping constant, ω n is the fundamental frequency, K i is the reactive loop integral coefficient, K q is the voltage regulation coefficient, U od 、U oq are the dq components of the steady-state output voltage at the PCC point, ω c The cutoff frequency of the low-pass filter in the power calculation link, I od , I oq are the dq components of the steady-state output current at the PCC point, I d , I q are the dq components of the inverter output current steady-state value, L v 、r v are virtual inductance and virtual resistance respectively, C f 、L f 、r f They are filter capacitor, filter inductor and parasitic resistance respectively, K Pv , K iv are the proportional coefficient and integral coefficient of the voltage loop proportional-integral controller, K Pi , K ii are the proportional coefficient and integral coefficient of the current loop proportional-integral controller, L c is the equivalent inductance of the grid.

[0036] Furthermore, the method for calculating the eigenvalues of the characteristic matrix using the eigenvalue analysis method based on the state space matrix described in step S2 is as follows:

[0037] make Solving state-space equations Find the system steady-state point I d , I q 、U od 、U oq , I od , I oq The steady-state point, main circuit parameters and control parameters are substituted into the state space matrix A to obtain the eigenvalue of the state space matrix A. The eigenvalue is expressed as: λ = σ + jω, σ is the real part of the eigenvalue, ω is the imaginary part of the eigenvalue, and j is the imaginary unit.

[0038] Furthermore, the method for determining the stability of the system in step S2 is as follows:

[0039] 1) The necessary condition for system stability is that the real parts of all eigenvalues of the state space matrix A are less than 0, that is, σ1…σ 14 <0;

[0040] 2) If σ1…σ 14 If one of them is not less than 0, the system is unstable;

[0041] 3)σ1…σ 14 The smaller the value, the more stable the system.

[0042] Furthermore, the calculation method of the participation factor in step S2 is as follows:

[0043] Combining the characteristic column vectors of the state space matrix A by column, we have: Combining the left eigenvectors of the state space matrix A by row, we have The definition of matrix P is arranged according to column vectors: P = [p1 p2 ...p n ], then P i =[p 1i p 2i ... p ni ] T =[φ 1i ψ i1 φ 2i ψ i2 ... φ ni ψ in ] T , where the elements P of the matrix P are ki is the participation factor, which indicates the degree of participation of the kth state variable in the i-th oscillation mode.

[0044] Furthermore, the method of establishing the frequency response model of the VSG grid-connected system in step S4, obtaining control parameters related to the frequency support capability, and obtaining the constraint range of the control parameters according to the frequency regulation requirements is as follows:

[0045] The frequency response model of the VSG grid-connected system is as follows:

[0046]

[0047] Where, U n is the rated amplitude of the grid-connected voltage, X is the modulus of the output impedance of the virtual synchronous generator;

[0048] When the dynamic process of frequency modulation ends, the relationship between the change in active power ΔPe output by the virtual synchronous machine and the change in system frequency Δωg is:

[0049]

[0050] By setting D and K p Adjust the ability of VSG to actively participate in grid frequency regulation;

[0051] Design VSG control parameters, namely:

[0052] Δω g =2πf≤1.256 (6)

[0053] Where ΔP e is the change in VSG active power, which is related to the ability of VSG to participate in frequency regulation. In new energy stations, 10% to 20% of the rated capacity must be equipped as frequency regulation support. With 10% of the rated capacity as the constraint condition, ΔP e =10%S n , thus obtaining the control parameters D and K p scope of constraints.

[0054] The advantages of the present invention are:

[0055] The present invention establishes a small signal model for the grid-connected inverter, the virtual synchronous generator control link (VSG) and other control links; uses the eigenvalue analysis method based on the small signal model to obtain the stable range of each control parameter; establishes a frequency response model of the VSG grid-connected system, analyzes the control parameters related to the frequency support capability, and obtains the constraint range of the control parameters according to the frequency modulation requirements; combines the stable ranges of each control parameter obtained by the eigenvalue analysis method, and finally obtains the value range of all parameters after intersection; the method of the present invention takes into account both frequency support capability and system stability; compared with the existing technology, its significant advantages are: 1) the present invention decomposes the control module of the target system to obtain the representation of each control model module, which is universal; 2) the physical meaning is clear, the model accuracy is high, and the method is intuitive and effective; 3) the parameter design method of the present invention can be directly used for parameter design under VSG control in the form of photovoltaic power generation systems, wind turbines, energy storage systems, etc., and has strong scalability and extensibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A flow chart of the control parameter design method for VSG grid-connected system for grid stability and frequency support;

[0057] Figure 2 is the eigenvalue trajectory of the damping constant of the VSG control parameter D;

[0058] Figure 3 is the eigenvalue trajectory of the inertia constant of the VSG control parameter J;

[0059] Figure 4 is the VSG control parameter K i is the eigenvalue trajectory diagram of the reactive loop integral coefficient;

[0060] Figure 5 The frequency response model diagram of the VSG grid-connected system;

[0061] Figure 6 The simulation comparison diagram of active power and frequency before and after the VSG grid-connected system parameter correction. DETAILED DESCRIPTION

[0062] 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 will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0063] The technical solution of the present invention is further described below with reference to the accompanying drawings and specific embodiments:

[0064] Example 1

[0065] like Figure 1 As shown, the VSG grid-connected system control parameter design method for grid stability and frequency support according to an embodiment of the present invention is used for parameter design under VSG control in the form of photovoltaic power generation systems, wind turbines, energy storage systems, etc., and includes the following steps:

[0066] Step 1: Establish small signal models for the grid-connected inverter main circuit, VSG control link, power calculation link, virtual impedance link, and voltage and current control link respectively; integrate the small signal models of each link to obtain the state space matrix of the VSG grid-connected system; the details are as follows:

[0067] Step 1.1: Obtain the corresponding state-space equations based on the VSG grid-connected inverter main circuit and VSG control link, power calculation link, virtual impedance link, and voltage and current control link. Linearize the state-space equations to obtain the small signal models corresponding to each link.

[0068] The state space equation can be described by n first-order nonlinear ordinary differential equations, specifically:

[0069]

[0070] Where x=[x1,x2,…,x n ] T is the state variable of the system, the constant n is the number of state variables of the system, that is, the order of the system, u=[u1,u2,…,u r ] T is the input quantity of the system, the constant r is the number of system input quantities, and f() is the differential quantity describing the system state variable A function that expresses the relationship between the system state variable x and the system input u.

[0071] By linearizing the state space equation at the steady-state point of the system, the corresponding small signal model can be obtained, which is:

[0072]

[0073] Where Δx is the disturbance of the state variable, is the differential corresponding to the disturbance, matrix A is the system state space matrix, Δu is the disturbance input to the system, and matrix B is the input coefficient matrix.

[0074] Step 1.2: Based on the small signal models of each link, the state space matrix of the VSG grid-connected system can be obtained by integrating the matrix form, as follows:

[0075] The state space matrix obtained after integration is an n-order square matrix. In the example model of the embodiment of the present invention, n=14, and the expression of the state space matrix A is:

[0076] A=[l1 l2 l3 l4 l5 l6 l7 l8 l9 l 10 l 11 l 12 l 13 l 14 ] T (3)

[0077] Where l1…l 14 is the corresponding matrix row vector, and its specific expression is:

[0078]

[0079]

[0080] l3=[0 0 -ω c 0 0 0 1.5ω c I od 1.5ω c I oq 1.5ω c U od 1.5ω c U oq 0 0 0 0];

[0081] l4=[0 0 0 -ω c 0 0 -1.5ω c I oq 1.5ω c I od 1.5ω c U oq -1.5ω c U od 0 0 0 0];

[0082]

[0083]

[0084]

[0085]

[0086]

[0087]

[0088] l11 =[I oq L v 1 0 0 0 0 -1 0 -r v ω n L v 0 0 0 0];

[0089] l 12 =[-I od L v 0 0 0 0 0 0 -1 -ω n L v -r v 0 0 0 0];

[0090] l 13 =[I oq L v K Pv K Pv 0 0 -1 0 -K Pv -ω n C f -r v K Pv +1 K Pv L v ω n K iv 0 0 0];

[0091] l 14 =[-I od L v K Pv 0 0 0 0 -1 ω n C f -K Pv K Pv L v ω n -r v K Pv +1 0 K iv 0 0];

[0092] Where, K p is the frequency modulation coefficient, J is the inertia constant, D is the damping constant, ω n is the fundamental frequency, K i is the reactive loop integral coefficient, K q is the voltage regulation coefficient, U od 、U oq are the dq components of the steady-state output voltage at the PCC point, ω c The cutoff frequency of the low-pass filter in the power calculation link, I od , I oqare the dq components of the steady-state output current at the PCC point, I d , I q are the dq components of the inverter output current steady-state value, L v 、r v are virtual inductance and virtual resistance respectively, C f 、L f 、r f They are filter capacitor, filter inductor and parasitic resistance respectively, K Pv , K iv are the proportional coefficient and integral coefficient of the voltage loop proportional-integral controller, K Pi , K ii are the proportional coefficient and integral coefficient of the current loop proportional-integral controller, L c is the equivalent inductance of the grid.

[0093] Step 2: Based on the state space matrix, the eigenvalue analysis method is used to calculate the eigenvalues of the characteristic matrix, and the stability of the system at this time is determined. The participation factor of the characteristic matrix is calculated to obtain the influencing parameters of each oscillation mode of the system; the details are as follows;

[0094] Step 2.1: Set the left side of the state-space equation to 0 and solve the state-space equation to obtain the system steady-state quantity. Substitute the system steady-state quantity, main circuit parameters, and various control parameters into the state-space matrix A, calculate the eigenvalue of the state-space matrix A, and determine the stability of the system at this time. The details are as follows:

[0095] make Solving state-space equations Find the system steady-state point I d , I q 、U od 、U oq , I od , I oq The steady-state point, main circuit parameters and control parameters are substituted into the state space matrix A to obtain the eigenvalue of the state space matrix A. It is assumed that the eigenvalue is expressed as: λ = σ + jω, σ is the real part of the eigenvalue, ω is the imaginary part of the eigenvalue, and j is the imaginary unit.

[0096] The system stability is determined according to the following criteria:

[0097] 1) The necessary condition for system stability is that the real parts of all eigenvalues of the state space matrix A are less than 0, that is, σ1…σ 14 <0;

[0098] 2) If σ1…σ 14 If one of them is not less than 0, the system is unstable;

[0099] 3)σ1…σ 14The smaller the value, the more stable the system.

[0100] The results of eigenvalue analysis are shown in Table 1. It can be seen that the real parts of all eigenvalues of the state space matrix are less than 0, so the system is stable.

[0101] Table 1 Eigenvalue analysis results

[0102]

[0103]

[0104] Step 2.2: Calculate the participation factor of the state space characteristic matrix A and obtain the main influencing parameters of each oscillation mode of the system, as follows:

[0105] The participation factor is used to describe the main relevant variables of each oscillation mode. The characteristic column vectors of the state space matrix A are combined by columns, and we have: Combining the left eigenvectors of the state space matrix A by row, we have The definition of matrix P is arranged according to column vectors: P=[p1 p2 ... p n ], then P i =[p 1i p 2i ... p ni ] T =[φ 1i ψ i1 φ 2i ψ i2 ... φ ni ψ in ] T , where the element P of the matrix P is ki is the participation factor, which indicates the degree of participation of the kth state variable in the i-th oscillation mode.

[0106] Step 3: Under the premise of system stability, by changing the influencing parameters of each oscillation mode one by one, the corresponding eigenvalue trajectory diagram is drawn. According to the eigenvalue trajectory diagram, the boundary value of the real part of the eigenvalue less than 0 can be obtained. The corresponding control parameter is the boundary value of system stability, thereby obtaining the stability range of each control parameter.

[0107] Figure 2 、 Figure 3 、 Figure 4 Some eigenvalue trajectory diagrams that have a significant impact on system stability are given. Furthermore, the boundary values of system stability can be calculated based on the eigenvalue trajectory diagrams. The specific parameter ranges are shown in Table 2.

[0108] Table 2 Parameter range

[0109] parameter <![CDATA[w c ]]> <![CDATA[K i ]]> <![CDATA[r v ]]> <![CDATA[L v ]]> <![CDATA[K pv ]]> scope 24.98-62.8 0-7.48 1.44-2 0-0.01034 0.24-50 parameter <![CDATA[K iv ]]> <![CDATA[K pi ]]> <![CDATA[K ii ]]> J D scope 1-65 0.6-100 50-222 1-6.5 120.36-200

[0110] Step 4: Establish a frequency response model for the VSG grid-connected system, derive control parameters related to frequency support capability, and derive the constraint range of the control parameters based on the frequency regulation requirements, as follows:

[0111] According to the VSG small signal model, the active control loop model can be expanded as Figure 5 According to the control block diagram, the frequency response model of the VSG grid-connected system can be obtained as follows:

[0112]

[0113] Where, U n is the rated amplitude of the grid-connected voltage, X is the modulus of the output impedance of the virtual synchronous generator;

[0114] Equation (4) describes the dynamic process of VSG participating in frequency support. When the grid frequency changes, the active power output by the VSG also changes accordingly, actively participating in the primary frequency regulation of the grid. After the dynamic process of frequency regulation ends, the relationship between the change in active power output by the virtual synchronous machine ΔPe and the change in system frequency Δωg is:

[0115]

[0116] Formula (5) reflects the active power-frequency droop characteristics of VSG. By setting D and K p It can flexibly adjust the ability of VSG to actively participate in grid frequency regulation.

[0117] According to the national standard GB / T15945-2008, the allowable range of frequency deviation in my country is 0.2Hz to 0.5Hz. With the steady-state frequency deviation not exceeding 0.2Hz as the constraint condition Δfsmax≤0.2Hz, the VSG control parameters are designed as follows:

[0118] Δω g =2πf≤1.256 (6)

[0119] Where ΔP e is the change in VSG active power, which is related to the ability of VSG to participate in frequency regulation. Generally, in new energy stations, 10% to 20% of rated capacity must be equipped as frequency regulation support. With 10% rated capacity as the constraint condition, ΔP e =10%S n , we can get the control parameters D and K p The specific parameter ranges are shown in Table 3.

[0120] Table 3 Constraint range of control parameters

[0121] Frequency support parameters D Kp Constraint Scope 2.54-200 Greater than 0

[0122] Step 5: Combine the stable range of each control parameter obtained based on the eigenvalue analysis method in step 3 and the frequency support constraint range obtained in step 4, take the intersection and finally obtain the value range of all parameters to complete the parameter design.

[0123] Simulation test:

[0124] The VSG grid-connected system was built using Matlab / Simulink simulation software, and simulation tests were carried out before and after parameter correction. Considering that the system parameters were stable before correction, the main corrections were made to the frequency support related parameters, which are given in Table 4. Based on the simulation test data, the simulation results before and after parameter correction were compared.

[0125] Table 4 Correction of frequency support related parameters

[0126] parameter D Kp Parameter value before correction 70 30 Corrected parameter value 150 30000

[0127] The simulation conditions are as follows: When the system runs for 6 seconds, the load suddenly increases, causing the grid frequency to drop. Figure 6 A comparison of the active power and frequency simulation waveforms of the VSG grid-connected system before and after parameter modification after a grid frequency drop is presented. The figure shows that the system remains stable after the parameter modification, but the magnitude of the grid frequency drop is less than before the modification, indicating that the frequency support capability of the VSG control has been enhanced. Therefore, the simulation results verify the correctness of the parameter design.

[0128] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A VSG grid-connected system control parameter design method for grid stability and frequency support, characterized by: The following steps are involved: S1. Establish small signal models for the grid-connected inverter main circuit, VSG control link, power calculation link, virtual impedance link, and voltage and current control link; integrate the small signal models of each link to obtain the state space matrix of the VSG grid-connected system; The method for establishing the small signal model of the grid-connected inverter main circuit, VSG control link, power calculation link, virtual impedance link, and voltage and current control link is as follows: S11. Use n first-order nonlinear ordinary differential equations to describe the state space equations of the grid-connected inverter main circuit and VSG control link, power calculation link, virtual impedance link, and voltage and current control link, specifically: （1） Where, =[ 1, 2,…, n ] T is the state variable of the system, the constant n is the number of state variables of the system, that is, the order of the system, =[ 1, 2,…, r ] T is the input quantity of the system, the constant r is the number of input quantities of the system, To describe the differential of the system state variable and system state variables , system input The function of the relationship; S12. Linearize the state space equation at the system steady-state point to obtain the corresponding small signal model, which is: （2） Where, is the disturbance of the state variable, is the differential corresponding to the disturbance, and the matrix A is the system state space matrix. is the disturbance input to the system, and matrix B is the input coefficient matrix; The state space matrix of the VSG grid-connected system is: （3） Where, is the corresponding matrix row vector, and its specific expression is: ； ； ； ； ； ； ； ； ； ； ； ； ； ； Where, is the frequency modulation coefficient, is the inertia constant, is the damping constant, is the fundamental frequency, is the reactive loop integral coefficient, is the voltage regulation coefficient, They are the steady-state values of the output voltage at the PCC point. Quantity, The cutoff frequency of the low-pass filter in the power calculation link, They are the steady-state values of the output current at the PCC point. Quantity, are the steady-state values of the inverter output current Quantity, are virtual inductance and virtual resistance respectively, They are filter capacitor, filter inductor and parasitic resistance respectively. are the proportional coefficient and integral coefficient of the voltage loop proportional-integral controller, are the proportional coefficient and integral coefficient of the current loop proportional-integral controller respectively, is the equivalent inductance of the grid; S2. Based on the state space matrix, the eigenvalue analysis method is used to calculate the eigenvalues of the characteristic matrix, and the stability of the system at this time is determined. The participation factor of the characteristic matrix is calculated to obtain the influencing parameters of each oscillation mode of the system; S3. Under the premise of system stability, by changing the influencing parameters of each oscillation mode one by one, the corresponding eigenvalue trajectory diagram is drawn. According to the eigenvalue trajectory diagram, the boundary value where the real part of the eigenvalue is less than 0 is obtained. The corresponding control parameter is the boundary value of system stability, thereby obtaining the stable range of each control parameter; S4. Establish a frequency response model for the VSG grid-connected system, derive control parameters related to frequency support capability, and derive constraint ranges for the control parameters based on frequency regulation requirements; S5. Combining the stability range of each control parameter obtained by the eigenvalue analysis method with the constraint range of the frequency support, the intersection is taken to finally obtain the value range of all parameters and complete the parameter design.

2. The VSG grid-connected system control parameter design method for grid stability and frequency support according to claim 1 is characterized in that: The method for calculating the eigenvalues of the characteristic matrix using the eigenvalue analysis method based on the state space matrix described in step S2 is as follows: make Solving state-space equations , find the system steady-state point The steady-state point, main circuit parameters and control parameters are substituted into the state space matrix A to obtain the eigenvalue of the state space matrix A. The eigenvalue is expressed as: , is the real part of the eigenvalue, is the imaginary part of the eigenvalue, Is an imaginary unit.

3. The VSG grid-connected system control parameter design method for grid stability and frequency support according to claim 2 is characterized in that: The method for determining the stability of the system described in step S2 is as follows: 1) The necessary condition for system stability is that the real parts of all eigenvalues of the state space matrix A are less than 0, that is, ; 2) If If one of them is not less than 0, the system is unstable; 3) The smaller the value, the more stable the system.

4. The VSG grid-connected system control parameter design method for grid stability and frequency support according to claim 3 is characterized in that: The calculation method of the participation factor described in step S2 is as follows: Combining the characteristic column vectors of the state space matrix A by column, we have: , combine the left eigenvectors of the state space matrix A by row, and we have , define the matrix P arranged as column vectors: , then , where the elements of the matrix P are is the participation factor, indicating the In the oscillation mode The participation degree of a state variable.

5. The VSG grid-connected system control parameter design method for grid stability and frequency support according to claim 4 is characterized in that: The method for establishing the frequency response model of the VSG grid-connected system in step S4, obtaining control parameters related to the frequency support capability, and obtaining the constraint range of the control parameters according to the frequency regulation requirements is as follows: The frequency response model of the VSG grid-connected system is as follows: （4） Where, , is the rated amplitude of the grid-connected voltage, is the modulus of the output impedance of the virtual synchronous generator; When the dynamic process of frequency modulation ends, the relationship between the change in active power ΔPe output by the virtual synchronous machine and the change in system frequency Δωg is: （5） By setting D and Adjust the ability of VSG to actively participate in grid frequency regulation; Design VSG control parameters, namely: （6） in, is the change in VSG active power, which is related to the ability of VSG to participate in frequency regulation. In new energy stations, 10% to 20% of the rated capacity must be equipped as frequency regulation support. With 10% rated capacity as the constraint condition, , thus obtaining the control parameters D and scope of constraints.

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