A method for establishing equivalent impedance model of wind farm under all working conditions

Abstract

A method for establishing an equivalent impedance model for all operating conditions of a wind farm, comprising: Step 1: Collect the active power P of the i-th steady-state operating point of the wind farm through a current transformer i , reactive power Q i , voltage U i , current I i ; The calculation formula for the equivalent impedance model of all operating conditions of the wind farm is: P 2 + aQ 2 + bZ 2 + cP + dQ + eZ + f = 0; Construct an error calculation formula: #imgabs0# Solve the sum of squared errors of N operating points; Solve the coefficients a, b, c, d, e, f to be determined. After obtaining the coefficients, substitute the collected P and Q of any operating point into formula (1) to obtain the impedance model Z under any operating condition. The purpose of the present invention is to design a method for establishing an equivalent impedance model for all operating conditions of a wind farm, a prediction method for establishing an equivalent impedance model for all operating conditions through a known operating condition impedance model, so as to solve the current dilemma that the operating conditions of wind farms are complex and numerous and cannot be enumerated

Description

Technical field:

[0001] The invention relates to the technical field of wind farm equivalent modeling, and in particular to a method for establishing a full-operating-condition equivalent impedance model of a wind farm. Background technology:

[0002] In recent years, global warming has become a topic of great concern. The core issue at present is how to reduce carbon dioxide emissions. For the power system sector, increasing renewable energy generation seems to be the best and most practical solution to this problem. Among new energy sources, wind power generation technology is relatively mature, wind power resources are abundant, and can be widely used around the world. According to the European Wind Energy Association report, by the end of 2020, Europe will install about 230GW of wind turbines. This will provide 14-17% of the EU's electricity.

[0003] Wind power generation has the advantages of high efficiency, cleanliness and sustainability, and is an inevitable choice for the development of contemporary electricity. In recent years, wind power has been developed on a large scale worldwide, and the wind power content in the power grid has continued to increase. With the completion of wind power bases of tens of millions of kilowatts, the centralized grid connection of large-scale wind turbines has brought huge challenges to the safe and stable operation of the power system. With the increasing maturity of wind power generation technology, the scale of grid connection of wind farms has increased rapidly. A wind farm often has dozens or even hundreds of wind turbines. Therefore, the construction of a full-operating model of a wind farm has an important demand in the fields of simulation modeling and stability analysis. However, due to the limitation that the operating conditions of wind farms cannot be exhaustively listed, it is necessary to derive a full-operating model through existing operating condition data. Summary of the invention:

[0004] The purpose of the present invention is to design a method for establishing an equivalent impedance model of all working conditions of a wind farm, and to establish a prediction method for the equivalent impedance model of all working conditions through a known working condition impedance model, so as to solve the current dilemma that the working conditions of wind farms are complex and numerous and cannot be exhaustively listed.

[0005] A method for establishing a full-operating equivalent impedance model of a wind farm comprises the following steps:

[0006] Step 1: Collect the active power P of the i-th steady-state working point of the wind farm through the current transformer i , reactive power Q i , voltage U i 、Current I i ;

[0007] Step 2: Construct the calculation formula of the equivalent impedance model of the wind farm under all working conditions as follows:

[0008] P 2 +aQ 2 +bZ 2 +cP+dQ+eZ+f=0 (1)

[0009] Among them, a, b, c, d, e, f are the coefficients to be determined, and Z is the impedance model;

[0010] Step 3: Construct the error calculation formula:

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[0012] Among them, Z i is the impedance model of the ith steady-state operating point;

[0013] Solve the sum of square errors of N working points. The specific calculation method is:

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[0015] Step 4: Solve the coefficients a, b, c, d, e, and f to be determined. After the coefficients are obtained, substitute the P and Q of any working point collected into formula (1) to obtain the impedance model Z under any working condition.

[0016] Preferably, the method of step 4 specifically comprises the following steps:

[0017] Let G(a,b,c,d,e,f) take partial derivatives of a,b,c,d,e,f respectively, and let the partial derivatives be 0.

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[0019] Substituting formula (2) and formula (3) into formula (4) yields formula (5):

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[0021] Continuing to take partial derivatives of formula (5), we can get formula (6):

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[0023] To simplify and facilitate the solution, let:

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[0048] Through formula (7):

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[0050] Then a, b, c, d, e, and f can be calculated. After all coefficients in the calculation formula of the equivalent impedance model of the full working condition are calculated, only P, Q, and Z are unknown in formula (1). If we need to predict the equivalent impedance model Z of the electric field at the kth working point k , then we only need to collect the active power P of the kth working point k , reactive power Q k , the P k and Q k Substituting into formula (1), we can calculate Z k .

[0051] Preferably, Z iThe calculation method is: Among them, U i and I i are the complex voltage and complex current respectively.

[0052] Preferably, the number N of steady-state operating points needs to be at least 6 groups, that is, N≥6.

[0053] Since U and I are constantly changing in a wind farm, Z is also constantly changing. Existing research can only obtain the impedance model Z of a certain working point by detecting parameters such as voltage and current at each working point, but cannot predict the impedance model of any working point. However, the working conditions of a wind farm are often numerous and complex. If one wants to know the impedance model of all working conditions, one can only measure them one by one through exhaustive enumeration, which is too time-consuming and labor-intensive. The present invention discloses a method for establishing an equivalent impedance model of all working conditions of a wind farm, and establishes a calculation method that can predict the equivalent impedance model of all working conditions. Only a small amount of tests are needed to effectively predict the impedance conditions of tens of thousands of working conditions, thereby effectively saving the test time of wind turbines and improving the test efficiency. Description of the drawings:

[0054] Attached Figure 1 The present invention provides a flow chart for establishing a full-operating-condition equivalent impedance model for a wind farm. Specific implementation method:

[0055] In the present invention, a method for establishing a full-operating equivalent impedance model of a wind farm comprises the following steps:

[0056] Step 100: Collect the active power P of the i-th steady-state working point of the wind farm through the current transformer i , reactive power Q i , voltage U i 、Current I i ;

[0057] Step 110: Construct a calculation formula for the equivalent impedance model of the wind farm under all working conditions as follows:

[0058] P 2 +aQ 2 +bZ 2 +cP+dQ+eZ+f=0 (1)

[0059] Among them, a, b, c, d, e, f are the coefficients to be determined, and Z is the impedance model;

[0060] Step 120: Construct the error calculation formula:

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[0062] Solve the sum of square errors of N working points. The specific calculation method is:

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[0064] Step 130: Solve the coefficients a, b, c, d, e, f:

[0065] Let G(a,b,c,d,e,f) take partial derivatives of a,b,c,d,e,f respectively, and let the partial derivatives be 0.

[0066] Right now:

[0067] Substituting formula (2) into formula (4) yields formula (5):

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[0069] Continuing to take partial derivatives of formula (5), we can get formula (6):

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[0071] To simplify and facilitate the solution, let:

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[0096] Through formula (7):

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[0098] Then a, b, c, d, e, and f can be calculated.

[0099] The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements, substitutions, modifications and embellishments can be made without departing from the principle and purpose of the present invention. These improvements, substitutions, modifications and embellishments should also be regarded as the scope of protection of the present invention.

Claims

1. A method for establishing a full-operating equivalent impedance model of a wind farm, characterized in that: The following steps are involved: Step 1: Collect the active power P of the i-th steady-state working point of the wind farm through the current transformer i , reactive power Q i , voltage U i 、Current I i ; Step 2: Construct the calculation formula of the equivalent impedance model of the wind farm under all working conditions as follows: P 2 +aQ 2 +bZ 2 +cP+dQ+eZ+f=0 (1) Among them, a, b, c, d, e, f are the coefficients to be determined, and Z is the impedance model; Step 3: Construct the error calculation formula: Among them, Z i is the impedance model of the ith steady-state operating point; Solve the sum of square errors of N working points. The specific calculation method is: Step 4: Solve the coefficients a, b, c, d, e, and f to be determined. After the coefficients are obtained, substitute the P and Q of any working point collected into formula (1) to obtain the impedance model Z under any working condition.

2. A method for establishing a full-operating equivalent impedance model of a wind farm according to claim 1, characterized in that: The method of step 4 specifically comprises the following steps: Let G(a,b,c,d,e,f) take partial derivatives of a,b,c,d,e,f respectively, and let the partial derivatives be 0. Right now: Substituting formula (2) and formula (3) into formula (4) yields formula (5): Continuing to take partial derivatives of formula (5), we can get formula (6): To simplify and facilitate the solution, let: Through formula (7): Then a, b, c, d, e, and f can be calculated.

3. The method for establishing a full-operating equivalent impedance model of a wind farm according to claim 1, characterized in that: Z i The calculation method is: Among them, U i and I i are the complex voltage and complex current respectively.

4. The method for establishing a full-operating equivalent impedance model of a wind farm according to claim 1, characterized in that: The number N of steady-state operating points needs to be at least 6 groups, that is, N≥6.

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