Method for evaluating stability margin of new energy multi-infeed system of receiving-end power grid

Abstract

The invention belongs to the field of new energy power system stability analysis and evaluation, and discloses a receiving end power grid new energy multi-infeed system stability margin evaluation method comprising the following steps: S1, determining a new energy station having the highest influence on a generalized short circuit ratio critical value; s2, the equivalent single-feed-in system impedance, determined in the step S1, of the new energy station is calculated; s3, calculating the equivalent model parameters of the new energy station determined in the step S1; and S4, calculating the stability margin of the new energy multi-infeed system of the receiving-end power grid. According to the method, the new energy station which has the highest influence on the generalized short-circuit ratio critical value is determined, disturbance measurement output is applied to the grid-connected point of the new energy station to calculate related parameters, and then the stability margin of the system is calculated; the method can effectively solve the problems that the control parameters of the current new energy station are difficult to obtain and the stability margin of the high-proportion new energy power system is difficult to calculate, has the characteristics of simple principle, easiness in implementation and the like, and has better practicability.

Description

Technical Field

[0001] The present invention belongs to the field of stability analysis and evaluation of new energy power systems, and in particular relates to an evaluation method for the stability margin of a new energy multi-feedback system of a receiving-end power grid. Background Art

[0002] In order to make full use of renewable resources such as wind and light, new energy stations usually operate in maximum power tracking mode, which requires grid voltage support. With the continuous increase in access capacity, the grid voltage support capacity is relatively insufficient, which may cause grid instability and lead to serious consequences such as large-scale disconnection and collapse.

[0003] A large number of methods have been proposed in existing research to evaluate the stability margin of power systems with a high proportion of renewable energy. Among them, the generalized short-circuit ratio theory uses the characteristic roots of the power flow Jacobian matrix to make judgments, defines the grid-related information as the generalized short-circuit ratio, and defines the equipment-related information as its critical value. The difference between the two is used to characterize the stability margin of the renewable energy multi-feed system, which has a rigorous theoretical basis. The critical value of the generalized short-circuit ratio includes the operation and control parameters of the renewable energy site, but equipment manufacturers usually do not open the control parameters for commercial confidentiality, which makes it difficult to calculate the stability margin of power systems with a high proportion of renewable energy. Summary of the invention

[0004] In view of this, the present invention proposes a method for evaluating the stability margin of a receiving-end power grid renewable energy multi-feed system. In view of the current problems that the control parameters of renewable energy stations are difficult to obtain and the stability margin calculation of power systems containing a high proportion of renewable energy is difficult, the present invention calculates the relevant parameters by applying disturbance measurement output at the renewable energy station grid connection point, and then calculates the stability margin of the system, which can better meet the needs of the project site, has the characteristics of simple principle, easy implementation, etc., and has good practicality.

[0005] To achieve the above object, the present invention provides a method for evaluating the stability margin of a receiving-end power grid renewable energy multi-feed system, which is characterized by comprising the following steps:

[0006] S1. Determine the new energy station with the highest impact on the critical value of generalized short-circuit ratio;

[0007] S2. Calculate the equivalent single-feed system impedance of the new energy station determined in step S1;

[0008] S3. Calculate the equivalent model parameters of the new energy station determined in step S1;

[0009] S4. Calculate the stability margin of the new energy multi-feed system of the receiving power grid.

[0010] Further, the step S1 includes the following sub-steps:

[0011] S1.1 Obtain the DC bus voltage U of the equivalent single-machine model of the new energy station when the power grid is operating normally dc0 , grid-connected point voltage dq axis component U d0 and U q0 , grid-connected point voltage phase θ0, output current dq axis component I d0 and I q0 , output power per unit value P b and Q b , the number of new energy stations n, the AC grid multi-port admittance matrix B;

[0012] S1.2 Calculate the generalized short-circuit ratio gSCR;

[0013]

[0014] Where minλ(·) is the minimum characteristic root of the calculation matrix; S B =diag(S B1 ,S B2 ,K,S Bn ) is the rated capacity matrix of new energy stations, S Bi is the rated capacity of each new energy station, i=1,2,…,n;

[0015] S1.3 Calculation matrix The eigenvector v1 of each new energy station is then used to calculate the generalized interaction factor gMIIF ij ;

[0016]

[0017] In the formula, Z ij is the mutual impedance between nodes i and j in the node impedance matrix Z; Z ii is the self-impedance of node i in the node impedance matrix Z; ν i1 and ν j1 are the i-th and j-th elements of the feature vector v1 respectively;

[0018] The new energy station with the largest generalized interaction factor is the new energy station with the highest impact on the critical value of the generalized short-circuit ratio.

[0019] Further, the S2 comprises the following sub-steps:

[0020] S2.1 applies power frequency disturbance voltage to the grid connection point of the new energy station determined in step S1, and measures the power frequency current phasor flowing into the grid and the voltage phasor at the point of application

[0021] S2.2 Calculation of equivalent single-feed system impedance Z g ;

[0022]

[0023] In the formula, and It is the power frequency voltage at the application point and the power frequency current flowing into the grid before the disturbance is applied; and It is the power frequency voltage after the disturbance is applied and the power frequency current flowing into the grid;

[0024]

[0025] In the formula, θ u0 =tan -1 (U q0 / U d0 );θ i0 =tan -1 (I q0 / I d0 ); j is an imaginary operator.

[0026] Further, the step S3 includes the following sub-steps:

[0027] S3.1 Apply a disturbance voltage to the grid connection point of the new energy station determined in step S1 at every interval ω0 = 30 Hz, and measure the dq-axis component U of the disturbance voltage amplitude fdk , U fqk and the global phase θ uk , the dq-axis component I of the current output of the new energy station under the corresponding frequency disturbance vdk ,I vqk and the global phase θ ik , until kω0 = 300 Hz, i.e. k = 10;

[0028] S3.2 Calculate the frequency response matrix G of the new energy station determined in step S1 by using the disturbance voltage and the current measured on the equipment side m (jω);

[0029]

[0030] S3.3 construct the frequency response matrix G(jω) of the equivalent single-machine model of the new energy station determined in step S1;

[0031]

[0032] in,

[0033]

[0034] In the formula, L f is the equivalent filter inductance of the equivalent model of the new energy station; s is the Laplace operator; C dcis the equivalent DC bus capacitance of the equivalent model of the new energy station; k po , k io are the outer loop proportion and integral coefficient of the equivalent model of new energy stations respectively; k pi , k ii They are the inner loop proportion and integral coefficient of the equivalent model of new energy stations respectively;

[0035] S3.4 Use particle swarm or genetic algorithm to solve the objective function minf = G(jω)-G m (jω), obtain the equivalent model parameter k in step S3.3 po , k io , k pi , k ii .

[0036] Furthermore, the calculation expression of the stability margin of the receiving-end power grid new energy multi-feed system is:

[0037] γ=gSCR-CgSCR

[0038] In the formula, γ represents the stability margin of the receiving-end power grid renewable energy multi-feed system; CgSCR is the critical value of the generalized short-circuit ratio;

[0039] The calculation method of CgSCR is: solve the equation Re[CgSCR 2 +βCgSCR+χ]=0

[0040] Where Re[·] means taking the real part; the calculation expressions of β and χ are as follows:

[0041]

[0042] Where P b and Q b is the per unit value of the apparent capacity of the new energy station. When the power factors of the stations are the same, the P b and Q b Same; F 11 、F 12 、F 21 、F 22 The expressions are:

[0043]

[0044] Where θ0 is the initial value of the grid-connected point voltage phase.

[0045] The beneficial effects of the present invention are:

[0046] Aiming at the problems that the control parameters of the current new energy stations are difficult to obtain and the stability margin calculation of the power system containing a high proportion of new energy is difficult, the present invention proposes a method for evaluating the stability margin of the receiving-end power grid new energy multi-feed system. The method calculates the relevant parameters by selecting the new energy station with the highest influence on the critical value of the generalized short-circuit ratio and applying the disturbance measurement output at its grid connection point, and then calculates the stability margin of the system. The method can better meet the needs of the engineering site, has the characteristics of simple principle, easy implementation, etc., and has good practicality.

[0047] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a flow chart of a method for evaluating stability margin of a receiving-end power grid renewable energy multi-feed system according to the present invention;

[0049] Figure 2 This is a topological diagram of a receiving-end power grid new energy multi-feed system of the present invention. DETAILED DESCRIPTION

[0050] In order to make the technical solutions, advantages and purposes of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of this application.

[0051] like Figure 1 and 2 As shown, this embodiment provides a method for evaluating the stability margin of a receiving-end power grid renewable energy multi-feed system, comprising the following steps:

[0052] S1. Determine the new energy station with the highest impact on the critical value of generalized short-circuit ratio;

[0053] S1.1 Obtain the DC bus voltage U of the equivalent single-machine model of the new energy station when the power grid is operating normally dc0 , grid-connected point voltage dq axis component U d0 and U q0 , grid-connected point voltage phase θ0, output current dq axis component I d0 and I q0 , output power per unit value P b and Q b, the number of new energy stations n, the AC grid multi-port admittance matrix B;

[0054] S1.2 Calculate the generalized short-circuit ratio gSCR;

[0055]

[0056] Where minλ(·) is the minimum characteristic root of the calculation matrix; S B =diag(S B1 ,S B2 ,K,S Bn ) is the rated capacity matrix of new energy stations, S Bi is the rated capacity of each new energy station, i=1,2,…,n;

[0057] S1.3 Calculation matrix The eigenvector v1 of each new energy station is then used to calculate the generalized interaction factor gMIIF ij ;

[0058]

[0059] In the formula, Z ij is the mutual impedance between nodes i and j in the node impedance matrix Z; Z ii is the self-impedance of node i in the node impedance matrix Z; ν i1 and ν j1 are the i-th and j-th elements of the feature vector v1 respectively;

[0060] The new energy station with the largest generalized interaction factor is the new energy station with the highest impact on the critical value of the generalized short-circuit ratio.

[0061] S2. Calculate the equivalent single-feed system impedance of the new energy station determined in step S1;

[0062] S2.1 applies power frequency disturbance voltage to the grid connection point of the new energy station determined in step S1, and measures the power frequency current phasor flowing into the grid and the voltage phasor at the point of application

[0063] S2.2 Calculation of equivalent single-feed system impedance Z g ;

[0064]

[0065] In the formula, and It is the power frequency voltage at the application point and the power frequency current flowing into the grid before the disturbance is applied; and It is the power frequency voltage after the disturbance is applied and the power frequency current flowing into the grid;

[0066]

[0067] In the formula, θ u0 =tan -1 (U q0 / U d0 );θ i0 =tan -1 (I q0 / I d0 ); j is an imaginary operator.

[0068] S3. Calculate the equivalent model parameters of the new energy station determined in step S1;

[0069] S3.1 Apply a disturbance voltage to the grid connection point of the new energy station with the highest impact on the critical value of the generalized short-circuit ratio at every interval ω0=30Hz, and measure the dq-axis component U of the disturbance voltage amplitude fdk , U fqk and the global phase θ uk , the dq-axis component I of the current output of the new energy station under the corresponding frequency disturbance vdk ,I vqk and the global phase θ ik , until kω0 = 300 Hz, i.e. k = 10;

[0070] S3.2 Calculate the frequency response matrix G of the new energy station determined in step S1 by using the disturbance voltage and the current measured on the equipment side m (jω);

[0071]

[0072] S3.3 construct the frequency response matrix G(jω) of the equivalent single-machine model of the new energy station determined in step S1;

[0073]

[0074] in,

[0075]

[0076] In the formula, L f is the equivalent filter inductance of the equivalent model of the new energy station; s is the Laplace operator; C dc is the equivalent DC bus capacitance of the equivalent model of the new energy station; k po , k io are the outer loop proportion and integral coefficient of the equivalent model of new energy stations respectively; k pi , k ii They are the inner loop proportion and integral coefficient of the equivalent model of new energy stations respectively;

[0077] S3.4 Use particle swarm or genetic algorithm to solve the objective function minf = G(jω)-G m (jω), obtain the equivalent model parameter k in step S3.3 po , k io , k pi , k ii .

[0078] S4. Calculate the stability margin of the receiving-end power grid's renewable energy multi-feed system;

[0079] The calculation expression of the stability margin of the receiving-end power grid renewable energy multi-feed system is:

[0080] γ=gSCR-CgSCR

[0081] In the formula, γ represents the stability margin of the receiving-end power grid renewable energy multi-feed system; CgSCR is the critical value of the generalized short-circuit ratio;

[0082] The calculation method of CgSCR is: solve the equation Re[CgSCR 2 +βCgSCR+χ]=0

[0083] Where Re[·] means taking the real part; the calculation expressions of β and χ are as follows:

[0084]

[0085] Where P b and Q b is the per unit value of the apparent capacity of the new energy station. When the power factors of the stations are the same, the P b and Q b Same; F 11 、F 12 、F 21 、F 22 The expressions are:

[0086]

[0087] Where θ0 is the initial value of the grid-connected point voltage phase.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the protection scope of the present invention.

Claims

1. A method for evaluating the stability margin of a receiving-end power grid renewable energy multi-feed system, characterized in that: The following steps are involved: S1. Determine the new energy station with the highest impact on the critical value of generalized short-circuit ratio; S2. Calculate the equivalent single-feed system impedance of the new energy station determined in step S1; S3. Calculate the equivalent model parameters of the new energy station determined in step S1; S4. Calculate the stability margin of the new energy multi-feed system of the receiving power grid.

2. The method for evaluating the stability margin of a receiving-end power grid renewable energy multi-feed system according to claim 1 is characterized in that: The step S1 comprises the following sub-steps: S1.1 Obtain the DC bus voltage U of the equivalent single-machine model of the new energy station when the power grid is operating normally dc0 , grid-connected point voltage dq axis component U d0 and U q0 , grid-connected point voltage phase θ0, output current dq axis component I d0 and I q0 , output power per unit value P b and Q b , the number of new energy stations n, the AC grid multi-port admittance matrix B; S1.2 Calculate the generalized short-circuit ratio gSCR; Where minλ(·) is the minimum characteristic root of the calculation matrix; S B =diag(S B1 ,S B2 ,K,S Bn ) is the rated capacity matrix of new energy stations, S Bi is the rated capacity of each new energy station, i=1,2,…,n; S1.3 Calculation Matrix The eigenvector v1 of each new energy station is then used to calculate the generalized interaction factor gMIIF ij ; In the formula, Z ij is the mutual impedance between nodes i and j in the node impedance matrix Z; Z ii is the self-impedance of node i in the node impedance matrix Z; ν i1 and ν j1 are the i-th and j-th elements of the feature vector v1 respectively; The new energy station with the largest generalized interaction factor is the new energy station with the highest impact on the critical value of the generalized short-circuit ratio.

3. The method for evaluating the stability margin of a receiving-end power grid renewable energy multi-feed system according to claim 2 is characterized in that: The S2 comprises the following sub-steps: S2.1 applies power frequency disturbance voltage to the grid connection point of the new energy station determined in step S1, and measures the power frequency current phasor flowing into the grid and the voltage phasor at the point of application S2.2 Calculation of equivalent single-feed system impedance Z g ; In the formula, and It is the power frequency voltage at the application point and the power frequency current flowing into the grid before the disturbance is applied; and It is the power frequency voltage after the disturbance is applied and the power frequency current flowing into the grid; In the formula, θ u0 =tan -1 (U q0 / U d0 );θ i0 =tan -1 (I q0 / I d0 ); j is an imaginary operator.

4. The method for evaluating the stability margin of a receiving-end power grid renewable energy multi-feed system according to claim 3 is characterized in that: The step S3 comprises the following sub-steps: S3.1 Apply a disturbance voltage to the grid connection point of the new energy station determined in step S1 at every interval ω0 = 30 Hz, and measure the dq-axis component U of the disturbance voltage amplitude fdk , U fqk and the global phase θ uk , the dq-axis component I of the current output of the new energy station under the corresponding frequency disturbance vdk ,I vqk and the global phase θ ik , until kω0=300Hz, i.e. k=10; S3.2 Calculate the frequency response matrix G of the new energy station determined in step S1 by using the disturbance voltage and the current measured on the equipment side m (jω); S3.3 construct the frequency response matrix G(jω) of the equivalent single-machine model of the new energy station determined in step S1; in, In the formula, L f is the equivalent filter inductance of the equivalent model of the new energy station; s is the Laplace operator; C dc is the equivalent DC bus capacitance of the equivalent model of the new energy station; k po , k io are the outer loop proportion and integral coefficient of the equivalent model of new energy stations respectively; k pi , k ii They are the inner loop proportion and integral coefficient of the equivalent model of new energy stations respectively; S3.4 Use particle swarm or genetic algorithm to solve the objective function minf = G(jω)-G m (jω), obtain the equivalent model parameter k in step S3.3 po , k io , k pi , k ii .

5. The method for evaluating the stability margin of a receiving-end power grid renewable energy multi-feed system according to claim 4 is characterized in that: The calculation expression of the stability margin of the receiving-end power grid new energy multi-feed system is: γ=gSCR-CgSCR In the formula, γ represents the stability margin of the multi-feed-in system of renewable energy in the receiving-end power grid; CgSCR is the critical value of the generalized short-circuit ratio; The calculation method of CgSCR is: solve the equation Re[CgSCR 2 +βCgSCR+χ]=0 Where Re[·] means taking the real part; the calculation expressions of β and χ are as follows: Where P b and Q b is the per unit value of the apparent capacity of the new energy station. When the power factors of the stations are the same, the P b and Q b Same; F 11 、F 12 、F 21 、F 22 The expressions are: Where θ0 is the initial value of the grid-connected point voltage phase.

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