A method for equivalent modeling of wind turbines

Abstract

A method for equivalent modeling of a wind turbine generator set includes: applying three-phase voltages with a frequency of f to the terminals of the three-phase voltages of the wind turbine generator set model; collecting the ABC three-phase currents output by the wind turbine generator set model, and calculating the three-phase inductance, three-phase resistance, and three-phase capacitance at the frequency f; calculating the equivalent inductance, equivalent resistance, and equivalent capacitance at the frequency f; applying three-phase voltages with a frequency of f<subgt;0< / subgt> to the terminals of the three-phase voltages of the wind turbine generator set model; collecting the ABC three-phase currents output by the wind turbine generator set model at the frequency f<subgt;0< / subgt>, and calculating the three-phase inductance, three-phase resistance, and three-phase capacitance at the frequency f<subgt;0< / subgt>; calculating the inductance optimization coefficient, resistance optimization coefficient, and capacitance optimization coefficient; calculating the optimized equivalent inductance L(f), equivalent resistance R(f), and equivalent capacitance C(f) of the wind turbine generator set model at the frequency f, and constructing the optimized model W(f) = j2πfL(f) + R(f) - j / (2πfC(f)) of the wind turbine generator set. This method plays an important role in analyzing the grid connection stability of large-scale wind farms. At the same time, frequency-domain equivalent modeling also has important reference significance for the accuracy of time-domain simulation.

Description

Technical Field:

[0001] The present invention relates to the technical field of equivalent modeling of wind farms, and particularly to a method for equivalent modeling of wind turbines. Background Art:

[0002] Wind power generation has the advantages of high efficiency, cleanness and sustainability, and is an inevitable choice for the contemporary power development. In recent years, a large amount of wind power has been developed globally, and the proportion of wind power in the power grid has been continuously increasing. With the successive completion of ten-million-kilowatt-level wind power bases, the large-scale centralized grid connection of 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 grid connection scale of wind farms has increased rapidly. A wind farm often has dozens or even hundreds of wind turbines. If a detailed model is established for each wind turbine separately, it will greatly increase the complexity of the power system simulation model and the simulation calculation time, and even face the problem of "curse of dimensionality". In addition, the operating characteristics and dynamic responses of each wind turbine in a large-scale wind farm are not exactly the same. Therefore, in order to accurately analyze the interaction between a large-scale wind farm and the power system, it is of great significance to study and establish a suitable equivalent model of the wind farm. In the research on equivalent modeling of wind farms, it is found that when too few clustering indexes are selected, the unit information is incomplete, resulting in a large error between the equivalent model and the detailed model; when too many indexes are selected, the clustering workload is increased, and if the correlation between variables and the redundancy in data are not processed, it will also affect the accuracy of the results. Therefore, although the frequency-domain equivalent modeling of wind farms has become an important research means for analyzing the grid connection characteristics of large-scale wind farms, there are still certain difficulties in the frequency-domain fast and high-precision equivalent modeling of wind turbines at present. Summary of the Invention:

[0003] The purpose of the present invention is to design a method for equivalent modeling of wind turbines to solve the difficulties existing in the current frequency-domain fast and high-precision equivalent modeling of wind turbines.

[0004] A method for equivalent modeling of wind turbines includes the following steps:

[0005] Step 1: Apply three-phase voltages ua k (f), ub k (f), uc k (f) with frequency f to the terminals of the three-phase voltages of the wind turbine model, where a, b, and c respectively represent the three phases A, B, and C, and k is the sampling sequence;

[0006] Step 2: Collect the three-phase currents ia k (f), ib k (f), ic k(f), calculate the inductance, resistance, and capacitance of phases A, B, and C at frequency f based on the three-phase voltage and three-phase current at frequency f; calculate the equivalent inductance, equivalent resistance, and equivalent capacitance of the wind turbine model at frequency f based on the inductance, resistance, and capacitance of phases A, B, and C.

[0007] Step 3: Apply a three-phase voltage ua k (f0), ub k (f0), uc k (f0) to the terminals of the three-phase voltage of the wind turbine model.

[0008] Step 4: Collect the three-phase currents ia k (f0), ib k (f0), ic k (f0) output by the wind turbine model at frequency f0 through current transformers, and calculate the inductance, resistance, and capacitance of the three phases at frequency f0 based on the three-phase voltage and three-phase current at frequency f0.

[0009] Step 5: Calculate the inductance optimization coefficient, resistance optimization coefficient, and capacitance optimization coefficient based on the inductance, resistance, and capacitance of the three phases at frequency f0 obtained in Step 4.

[0010] Step 6: Calculate the optimized equivalent inductance L(f), equivalent resistance R(f), and equivalent capacitance C(f) of the wind turbine model at frequency f based on the equivalent inductance, equivalent resistance, equivalent capacitance obtained in Step 2 and the inductance optimization coefficient, resistance optimization coefficient, and capacitance optimization coefficient calculated in Step 5, and construct the optimized model of the wind turbine at frequency f: W(f) = j2πfL(f) + R(f) - j / (2πfC(f)).

[0011] Preferably, the calculation formulas for the three-phase voltages ua k (f), ub k (f), uc k (f) at frequency f are as follows:

[0012]

[0013] Among them, M(f) represents the amplitude of the three-phase voltages of phases A, B, and C at frequency f, M(f) is a fixed value, and its value is 0.01 times the rated voltage amplitude of the wind turbine; ΔT is the sampling time interval, π is 3.1415926. Generally, if the sampling time interval is ΔT, the sampling sequence is the data at ΔT, 2ΔT, and 3ΔT.

[0014] Preferably, the formulas for calculating the inductance, resistance, and capacitance of phases A, B, and C at frequency f are as follows:

[0015]

[0016]

[0017]

[0018] Among them, La(f), Lb(f), and Lc(f) are the inductances of phases A, B, and C at frequency f; Ra(f), Rb(f), and Rc(f) are the resistances of phases A, B, and C at frequency f; Ca(f), Cb(f), and Cc(f) are the capacitances of phases A, B, and C at frequency f.

[0019] The formulas for calculating the equivalent inductance, equivalent resistance, and equivalent capacitance of the wind turbine model at frequency f are as follows:

[0020]

[0021] Among them, L0(f), R0(f), and C0(f) are the equivalent inductance, equivalent resistance, and equivalent capacitance at frequency f, respectively.

[0022] Preferably, the formulas for calculating the three-phase voltages ua k (f0), ub k (f0), and uc k (f0) are as follows:

[0023]

[0024] Among them, M(f0) represents the amplitudes of the three-phase voltages of A, B, and C at frequency f0. M(f0) is a fixed value, which is 0.01 times the rated voltage amplitude of the wind turbine.

[0025] Preferably, the formulas for calculating the inductances, resistances, and capacitances of phases A, B, and C at frequency f0 are as follows:

[0026]

[0027]

[0028]

[0029] Among them, La(f0), Lb(f0), and Lc(f0) are the inductances of phases A, B, and C at frequency f0; Ra(f0), Rb(f0), and Rc(f0) are the resistances of phases A, B, and C at frequency f0; Ca(f0), Cb(f0), and Cc(f0) are the capacitances of phases A, B, and C at frequency f0.

[0030] Preferably, the formulas for calculating the inductance optimization coefficient, resistance optimization coefficient, and capacitance optimization coefficient are as follows:

[0031]

[0032]

[0033] Among them, ΔL1 and ΔL2 are inductance optimization coefficients, and ΔR1 and ΔR2 are resistance optimization coefficients. is the capacitance optimization coefficient.

[0034] Preferably, the calculation formulas for the optimized equivalent inductance L(f), equivalent resistance R(f), and equivalent capacitance C(f) at frequency f are:

[0035]

[0036] Preferably, k ∈ [1, 3]; ΔT adopts a typical interval: 0.00001S.

[0037] Preferably, the value range of f is 1 to 1000 Hz, and f0 is 50 Hz.

[0038] Inject two frequencies f and f0 into formula (1) to calculate the counteracting disturbance. The two frequencies are symmetric about f0 in the frequency domain. During the solution process of formula (1), the result is affected by f0, so it needs to be optimized; f0 is used to establish the operating working point and calculate the optimization parameters. Therefore, in formula (6), only the frequency f0 is injected to solve the impedance characteristics of the steady-state working point. Therefore, in formula (1), f cannot be equal to f0.

[0039] A method for equivalent modeling of a wind turbine designed by the present invention plays an important role in analyzing the grid connection stability of large-scale wind farms, especially for the early warning or risk analysis of the subsynchronous oscillation phenomenon caused after the wind turbine is connected to the grid. At the same time, the frequency-domain equivalent modeling also has important reference significance for the accuracy of time-domain simulation. Description of the Drawings:

[0040] Attached Figure 1 is a flowchart of a method for equivalent modeling of a wind turbine provided by the present invention.

[0041] Attached Figure 2 is a structural diagram of an external disturbance source of the wind turbine model. Detailed Embodiments:

[0042] The following combines the description of the drawings Figure 1 and the drawings Figure 2 to illustrate the preferred embodiments of a method for equivalent modeling of a wind turbine provided by the present invention.

[0043] A method for equivalent modeling of a wind turbine includes the following steps:

[0044] Step 100: Apply three-phase voltages \(u_a(f)\), \(u_b(f)\), and \(u_c(f)\) with frequency \(f\) to the terminals of the three-phase voltages of the wind turbine model, where \(M(f)\) represents the amplitudes of the three-phase voltages of phases A, B, and C at frequency \(f\). \(M(f)\) is a fixed value, taking 0.01 times the rated voltage amplitude of the wind turbine; \(\Delta T\) is the sampling time interval, and \(\pi = 3.1415926\). k (f), \(u_b\) k (f), \(u_c\) k (f), where M(f) represents the amplitudes of the three-phase voltages of phases A, B, and C at frequency f. M(f) is a fixed value, taking 0.01 times the rated voltage amplitude of the wind turbine; ΔT is the sampling time interval, and π is 3.1415926.

[0045] Step 110: Collect the three-phase currents \(i_a(f)\), \(i_b(f)\), and \(i_c(f)\) output by the wind turbine model through current transformers, and calculate the three-phase inductances, three-phase resistances, and three-phase capacitances of phases A, B, and C at frequency \(f\) based on the three-phase voltages and three-phase currents at frequency \(f\); calculate the equivalent inductance, equivalent resistance, and equivalent capacitance of the wind turbine model at frequency \(f\) based on the three-phase inductances, three-phase resistances, and three-phase capacitances of phases A, B, and C, where k (f), \(i_b\) k (f), \(i_c\) k (f), and calculate the three-phase inductances \(L_a(f)\), \(L_b(f)\), \(L_c(f)\) of phases A, B, and C at frequency \(f\), the three-phase resistances \(R_a(f)\), \(R_b(f)\), \(R_c(f)\) of phases A, B, and C at frequency \(f\), the three-phase capacitances \(C_a(f)\), \(C_b(f)\), \(C_c(f)\) of phases A, B, and C at frequency \(f\); the equivalent inductance \(L_0(f)\), equivalent resistance \(R_0(f)\), and equivalent capacitance \(C_0(f)\) at frequency \(f\) respectively.

[0046]

[0047]

[0048]

[0049]

[0050] where \(L_a(f)\), \(L_b(f)\), \(L_c(f)\) are the three-phase inductances of phases A, B, and C at frequency \(f\); \(R_a(f)\), \(R_b(f)\), \(R_c(f)\) are the three-phase resistances of phases A, B, and C at frequency \(f\); \(C_a(f)\), \(C_b(f)\), \(C_c(f)\) are the three-phase capacitances of phases A, B, and C at frequency \(f\); \(L_0(f)\), \(R_0(f)\), \(C_0(f)\) are the equivalent inductance, equivalent resistance, and equivalent capacitance at frequency \(f\) respectively.

[0051] Step 120: Apply three-phase voltages \(u_a(f_0)\), \(u_b(f_0)\), and \(u_c(f_0)\) with frequency \(f_0\) to the terminals of the three-phase voltages of the wind turbine model, where k (f0), \(u_b\) k (f0), \(u_c\) k (f0), where where \(M(f_0)\) represents the amplitudes of the three-phase voltages of phases A, B, and C at frequency \(f_0\). \(M(f_0)\) is a fixed value, taking 0.01 times the rated voltage amplitude of the wind turbine.

[0052] Step 130: Collect the three-phase currents \(i_a(f_0)\), \(i_b(f_0)\), and \(i_c(f_0)\) output by the wind turbine model at frequency \(f_0\) through current transformers k (f0), \(i_b\)k (f0), ic k (f0), calculate the three-phase inductance, three-phase resistance, and three-phase capacitance at frequency f0 based on the three-phase voltage and three-phase current at frequency f0, where

[0053]

[0054]

[0055]

[0056] where La(f0), Lb(f0), and Lc(f0) are the three-phase inductances of phases A, B, and C at frequency f0; Ra(f0), Rb(f0), and Rc(f0) are the three-phase resistances of phases A, B, and C at frequency f0; Ca(f0), Cb(f0), and Cc(f0) are the three-phase capacitances of phases A, B, and C at frequency f0.

[0057] Step 140: Calculate the inductance optimization coefficient, resistance optimization coefficient, and capacitance optimization coefficient based on the three-phase inductance, three-phase resistance, and three-phase capacitance at frequency f0 = 50Hz obtained in Step 130, where

[0058]

[0059]

[0060] where ΔL1 and ΔL2 are the inductance optimization coefficients, ΔR1 and ΔR2 are the resistance optimization coefficients, is the capacitance optimization coefficient.

[0061] Step 150: Calculate the optimized equivalent inductance L(f), equivalent resistance R(f), and equivalent capacitance C(f) of the wind turbine model at frequency f based on the equivalent inductance, equivalent resistance, equivalent capacitance obtained in Step 110 and the inductance optimization coefficient, resistance optimization coefficient, and capacitance optimization coefficient calculated in Step 140, where

[0062]

[0063] Step 160: Construct the optimized model of the wind turbine at frequency f as:

[0064] W(f) = j2πfL(f) + R(f) - j / (2πfC(f)).

[0065] The above is only the preferred embodiment of the present invention. It should be noted that: for those of ordinary skill in the art, without departing from the principles and purposes of the present invention, several improvements, substitutions, variations, and refinements can be made, and these improvements, substitutions, variations, and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for equivalent modeling of a wind turbine, characterized in that, It includes the following steps: Step 1: Apply three-phase voltages \(u_a(f)\), \(u_b(f)\), and \(u_c(f)\) with frequency \(f\) to the terminals of the three-phase voltage of the wind turbine model, where \(a\), \(b\), and \(c\) represent phases A, B, and C respectively, and \(k\) is the sampling sequence; k (f), \(u_b\) k (f), \(u_c\) k (f), where \(a\), \(b\), and \(c\) represent phases A, B, and C respectively, and \(k\) is the sampling sequence; Step 2: Collect the three-phase currents \(i_a\), \(i_b\), and \(i_c\) output by the wind turbine model through a current transformer. k (f), \(i_b\) k (f), \(i_c\) (f), k (f), calculate the three-phase inductance, three-phase resistance, and three-phase capacitance at frequency \(f\) based on the three-phase voltage and three-phase current at frequency \(f\); calculate the equivalent inductance, equivalent resistance, and equivalent capacitance of the wind turbine model at frequency \(f\) based on the three-phase inductance, three-phase resistance, and three-phase capacitance of phases A, B, and C. Step 3: Apply three-phase voltages \(u_a\) k [(f0)], \(u_b\) k [(f0)], and \(u_c\) k [(f0)] with a frequency \(f_0\) to the terminals of the three-phase voltages of the wind turbine model; k (f0), \(u_b\) k (f0), \(u_c\) k (f0); Step 4: Collect the three-phase currents \(i_a\) k (\(f_0\)), \(i_b\) k (\(f_0\)), \(i_c\) k (\(f_0\)) output by the wind turbine model through a current transformer, and calculate the three-phase inductance, three-phase resistance, and three-phase capacitance at frequency \(f_0\) based on the three-phase voltage and three-phase current at frequency \(f_0\); Step Five: Calculate the inductance optimization coefficient, resistance optimization coefficient, and capacitance optimization coefficient based on the three-phase inductance, three-phase resistance, and three-phase capacitance at the frequency f0 obtained in Step Four; Step Six: Calculate the optimized equivalent inductance L(f), equivalent resistance R(f), and equivalent capacitance C(f) of the wind turbine model at the frequency f based on the equivalent inductance, equivalent resistance, equivalent capacitance obtained in Step Two, and the inductance optimization coefficient, resistance optimization coefficient, and capacitance optimization coefficient calculated in Step Five, and construct the optimized model of the wind turbine at the frequency f: W(f) = j2πfL(f) + R(f) - j / (2πfC(f)).

2. The equivalent modeling method of a wind turbine unit according to claim 1, wherein Three-phase voltage \(u_a\) with frequency \(f\) k (f), \(u_b\) k (f), \(u_c\) k (f) is calculated by the formula: Among them, M(f) represents the amplitudes of the three-phase voltages A, B, and C at the frequency f, M(f) is a fixed value, and its value is 0.01 times the rated voltage amplitude of the wind turbine; ΔT is the sampling time interval, and π is 3.1415926.

3. The equivalent modeling method of a wind turbine unit according to claim 1, characterized in that The formulas for calculating the three-phase inductance, three-phase resistance, and three-phase capacitance of A, B, and C at the frequency f are: Among them, La(f), Lb(f), and Lc(f) are the three-phase inductances of A, B, and C at the frequency f; Ra(f), Rb(f), and Rc(f) are the three-phase resistances of A, B, and C at the frequency f; Ca(f), Cb(f), and Cc(f) are the three-phase capacitances of A, B, and C at the frequency f. The formulas for calculating the equivalent inductance, equivalent resistance, and equivalent capacitance of the wind turbine model at the frequency f are: Among them, L0(f), R0(f), and C0(f) are the equivalent inductance, equivalent resistance, and equivalent capacitance at the frequency f, respectively.

4. The equivalent modeling method of a wind turbine unit according to claim 1, characterized in that Calculate the three-phase voltages \(u_a\) k (\(f_0\)), \(u_b\) k (\(f_0\)), \(u_c\) k (\(f_0\)) with the formula: Among them, M(f0) represents the amplitudes of the three-phase voltages A, B, and C at the frequency f0, M(f0) is a fixed value, and its value is 0.01 times the rated voltage amplitude of the wind turbine.

5. The equivalent modeling method of a wind turbine unit as described in claim 1, wherein The formulas for calculating the three-phase inductance, three-phase resistance, and three-phase capacitance of A, B, and C at the frequency f0 are: Among them, La(f0), Lb(f0), and Lc(f0) are the three-phase inductances of A, B, and C at the frequency f0; Ra(f0), Rb(f0), and Rc(f0) are the three-phase resistances of A, B, and C at the frequency f0; Ca(f0), Cb(f0), and Cc(f0) are the three-phase capacitances of A, B, and C at the frequency f0.

6. The equivalent modeling method of a wind turbine unit according to claim 1, characterized in that The formulas for calculating the inductance optimization coefficient, resistance optimization coefficient, and capacitance optimization coefficient are: Among them, ΔL1 and ΔL2 are inductance optimization coefficients, and ΔR1 and ΔR2 are resistance optimization coefficients, which are capacitance optimization coefficients.

7. A method for equivalent modeling of a wind turbine unit according to claim 1, characterized in that, The calculation formulas for the optimized equivalent inductance L(f), equivalent resistance R(f), and equivalent capacitance C(f) at the frequency f are: 。 8. The equivalent modeling method of a wind turbine unit according to claim 2, characterized in that k ∈ [1, 3]; ΔT adopts a typical interval: 0.00001S.

9. The equivalent modeling method of a wind turbine unit according to claim 2, characterized in that The value range of f is 1 to 1000 Hz, and f0 is 50 Hz.

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