Wind power generation system transient equivalent impedance prediction method based on PSCAD (Power System Computer Aided Design)

Abstract

The invention belongs to the technical field of electrical engineering, and particularly relates to a wind power generation system transient equivalent impedance prediction method based on PSCAD (Power System Computer Aided Design), which monitors and acquires parameters influencing the transient equivalent impedance of a wind power generation system in real time, and calculates the equivalent resistivity, equivalent resistance and equivalent reactance of the wind power generation system after the wind power generation system enters a transient state; and calculating the equivalent impedance of the wind power generation system after the wind power generation system enters a transient state by using the calculated transient equivalent resistance and transient equivalent reactance of the wind power generation system, and verifying the prediction accuracy of the transient equivalent impedance of the wind power generation system on the basis of PSCAD (Power System Computer Aided Design). According to the method, the influence of various parameters such as wind speed, air density, atmospheric pressure, illumination intensity, temperature, humidity, equivalent sectional area of a line, equivalent length of the line and the like on the transient process of the wind power generation system is fully considered, so that the transient equivalent impedance of the wind power generation system is effectively predicted, and the prediction performance is improved; and the dual requirements of accuracy and rapidity of the prediction method are met.

Description

Technical Field

[0001] The present invention relates to the field of electrical engineering technology, and in particular to a PSCAD-based method for predicting transient equivalent impedance of a wind power generation system. Background Art

[0002] In recent years, with the progress of human society and economic development, the consumption of traditional fossil energy has increased, leading to increasingly severe energy shortages and environmental pollution. Wind energy, as a clean, renewable energy source with abundant global reserves and easy large-scale development, can effectively alleviate these problems. Consequently, wind power generation is experiencing rapid growth. However, wind power systems are susceptible to external environmental interference during their operation. When a wind power system is disturbed and enters transient operation, its transient equivalent impedance will continuously change with the changing external environment. Therefore, the ability to accurately predict the transient equivalent impedance of a wind power system in real time is a critical issue facing the wind power industry.

[0003] Existing methods for predicting transient equivalent impedance of wind power generation systems include time-domain simulation and direct methods. The time-domain simulation method is computationally intensive, time-consuming, and slow, making it incapable of online monitoring of transient operation of wind power generation systems. The direct method is difficult to construct transient energy functions for complex systems, has poor adaptability, and produces overly conservative results with low prediction accuracy. The PSCAD-based method for predicting transient equivalent impedance of wind power generation systems can quickly and accurately monitor transient processes in wind power generation systems in real time as the external environment changes. This method predicts transient equivalent impedance with high accuracy and speed, providing a reliable basis and theoretical guidance for further research on wind power generation systems.

[0004] Therefore, we proposed a PSCAD-based transient equivalent impedance prediction method for wind power generation systems to solve the above problems. Summary of the Invention

[0005] (1) Technical problems solved

[0006] In response to the shortcomings of the existing technology, the present invention provides a PSCAD-based method for predicting the transient equivalent impedance of a wind power generation system, which tracks the transient process of the wind power generation system in real time, quickly and accurately predicts the transient equivalent impedance of the wind power generation system, and solves the xx problem raised in the above background technology.

[0007] (2) Technical solution

[0008] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0009] The PSCAD-based method for predicting transient equivalent impedance of a wind power generation system includes the following steps:

[0010] S1. Real-time monitoring and acquisition of parameters affecting the transient equivalent impedance of the wind power generation system, including:

[0011] Environmental parameters: wind speed V(t), air density ρ(P, T(t), H(t)), atmospheric pressure P, light intensity I(t), temperature T(t), humidity H(t);

[0012] System parameters: line equivalent cross-sectional area SS and equivalent length L;

[0013] S2. Calculate the equivalent resistivity of the wind power generation system after it enters the transient state ;

[0014] S3. Calculate the equivalent resistance R of the wind power generation system after it enters the transient state eq ;

[0015] S4. Calculate the equivalent reactance X after the wind power generation system enters the transient state eq ;

[0016] S5, the transient equivalent resistance R of the wind power generation system calculated using S3 and S4 eq and transient equivalent reactance X eq , calculate the equivalent impedance Z of the wind power generation system after entering the transient state eq ;

[0017] S6. Verify the accuracy of transient equivalent impedance prediction of wind power generation system based on PSCAD.

[0018] Furthermore, in step S1, the wind speed V(t), light intensity I(t), temperature T(t), and humidity H(t) are functions of time t, and the air density It is a function of atmospheric pressure P, temperature T(t), and humidity H(t).

[0019] Furthermore, in step S2, the equivalent resistivity is calculated , calculated as follows:

[0020] (1);

[0021] Where, T(t) represents the temperature of the area where the wind power generation system is located as a function of time t, H(t) represents the humidity of the area where the wind power generation system is located as a function of time t, V(t) represents the wind speed of the area where the wind power generation system is located as a function of time t, and I(t) represents the light intensity of the area where the wind power generation system is located as a function of time t. It represents the air density function of the area where the wind power generation system is located, and P represents the atmospheric pressure in the area where the wind power generation system is located. This parameter is a constant.

[0022] Furthermore, in step S3, the equivalent resistance R is calculated. eq , calculated as follows:

[0023] (2);

[0024] Where, Indicates the equivalent resistivity of the wind power generation system after entering the transient state, represents the air density function of the area where the wind power generation system is located, T(t) represents the temperature function of the area where the wind power generation system is located with respect to time t, H(t) represents the humidity function of the area where the wind power generation system is located with respect to time t, L and S are both constants, representing the equivalent length and equivalent cross-sectional area of ​​the line in the wind power generation system, respectively.

[0025] Furthermore, in step S4, the equivalent reactance X is calculated. eq , calculated as follows:

[0026] (3);

[0027] Where R eq represents the equivalent resistance of the wind power generation system after entering the transient state, f represents the rated frequency of the wind power generation system during production operation, T(t) represents the temperature of the area where the wind power generation system is located as a function of time t, H(t) represents the humidity of the area where the wind power generation system is located as a function of time t, I(t) represents the light intensity of the area where the wind power generation system is located as a function of time t, L and S are both constants, representing the equivalent length and equivalent cross-sectional area of ​​the line in the wind power generation system, respectively.

[0028] Furthermore, the step S5 includes:

[0029] Step S5.1: Calculate the modulus of the equivalent impedance Zeq after the wind power generation system enters the transient state , calculated as follows:

[0030] (4);

[0031] Where R eq It represents the equivalent resistance of the wind power generation system after entering the transient state, X eq represents the equivalent reactance of the wind power generation system after entering the transient state, f represents the rated frequency of the wind power generation system during production operation, L and S are constants, representing the equivalent length and equivalent cross-sectional area of ​​the line in the wind power generation system respectively;

[0032] Step S5.2: Calculate the equivalent impedance Z of the wind power generation system after it enters the transient state eq Impedance angle , calculated as follows:

[0033] (5);

[0034] Where, Indicates the equivalent impedance Z of the wind power generation system after entering the transient state eq The modulus value, R eq It represents the equivalent resistance of the wind power generation system after entering the transient state, X eq It represents the equivalent reactance of the wind power generation system after entering the transient state, and f represents the rated frequency of the wind power generation system during production operation.

[0035] Furthermore, the equivalent cross-sectional area S and equivalent length L of the line are determined according to actual line parameters of the wind power generation system.

[0036] Furthermore, in step S6, a wind power generation system and its transient model are constructed in PSCAD. The parameters in the wind power generation system and its transient model include: the angular velocity of the wind turbine WT, the power of the doubly fed induction generator DFIG, the power of the wind power generation system side converter WTSC, the value of the capacitor C, the power of the grid side converter GSC, the power of the step-up transformer T, and the number n of wind power generation system units.

[0037] Furthermore, the transient equivalent impedance of the wind power system is simulated and verified in PSCAD. If the simulation results are 、 and the value calculated in step S5 of the prediction method 、 If formula (6) and formula (7) are satisfied, it means that the method of the present invention is effective;

[0038] (6);

[0039] (7);

[0040] Where, is the modulus of the transient equivalent impedance of the wind power generation system calculated by the present invention, is the modulus of the transient equivalent impedance of the wind power system calculated by PSCAD simulation, is the impedance angle of the transient equivalent impedance of the wind power generation system calculated by the present invention, is the impedance angle of the transient equivalent impedance of the wind power system calculated by PSCAD simulation.

[0041] Furthermore, the parameters of the PSCAD model in step S6 include:

[0042] Wind turbine angular speed range: 18–25 r / min;

[0043] Doubly-fed induction generator power range: 1.5–3 MW;

[0044] The number of system units n≥5.

[0045] (3) Beneficial effects

[0046] Compared with the existing technology, the present invention provides a method for predicting transient equivalent impedance of wind power generation system based on PSCAD, which has the following beneficial effects:

[0047] The method of the present invention fully considers the influence of various parameters such as wind speed, air density, atmospheric pressure, light intensity, temperature, humidity, equivalent cross-sectional area of ​​the line, equivalent length of the line on the transient process of the wind power generation system. It not only realizes the effective prediction of the transient equivalent impedance of the wind power generation system, but also improves the prediction performance, meeting the dual requirements of accuracy and speed of the prediction method.

[0048] This method can track the transient process of the wind power generation system online and monitor the changes of equivalent impedance over time in real time, laying the foundation for calculating data such as power angle, active power, reactive power, voltage, and current in the transient process. It is of great significance to improving the transient stability of the wind power generation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Schematic diagram of the method flow of the present invention;

[0050] Figure 2 Schematic diagram of the PSCAD software verification model of the present invention. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0052] Example

[0053] like Figure 1 and Figure 2 As shown, an embodiment of the present invention proposes a method for predicting transient equivalent impedance of a wind power generation system based on PSCAD, comprising the following steps:

[0054] Step S1: monitor and measure various parameters that affect the transient equivalent impedance of the wind power generation system. Environmental parameters include wind speed V(t) and air density in the area where the wind power generation system is located. (P, T(t), H(t)), atmospheric pressure P, light intensity I(t), temperature T(t), humidity H(t), and other parameters include the equivalent cross-sectional area S and equivalent length L of the line in the wind power generation system. Among them, wind speed V(t), light intensity I(t), temperature T(t), humidity H(t) are functions of time t, and air density It is a function of atmospheric pressure, temperature T(t), and humidity H(t).

[0055] In this embodiment, various parameters affecting the transient equivalent impedance of a wind power generation system in a certain area are monitored for one year. By processing and analyzing the change curves formed by the monitoring data, functions that can describe the various parameters are defined. The change functions of the various parameters within 24 hours are: The light intensity function is:

[0056] , ;

[0057] The temperature function is as follows:

[0058] , ;

[0059] The humidity function is as follows:

[0060] , ;

[0061] , ;

[0062] The wind speed function is , ;

[0063] The atmospheric pressure is P = 97.99 kPa, and the equivalent cross-sectional area of ​​the line in the wind power generation system is S = 150 mm 2 , the equivalent length of the line in the wind power generation system is L=8km.

[0064] Step S2: Calculate the equivalent resistivity of the wind power generation system after it enters the transient state , the calculation method is shown in formula (1):

[0065] (1);

[0066] Where, T(t) represents the temperature of the area where the wind power generation system is located as a function of time t, H(t) represents the humidity of the area where the wind power generation system is located as a function of time t, V(t) represents the wind speed of the area where the wind power generation system is located as a function of time t, and I(t) represents the light intensity of the area where the wind power generation system is located as a function of time t. It represents the air density function of the area where the wind power generation system is located, and P represents the atmospheric pressure in the area where the wind power generation system is located. This parameter is a constant.

[0067] In this embodiment, the temperature function, humidity function, wind speed function, light intensity function, air density function and atmospheric pressure are as shown in step S1 in this embodiment.

[0068] According to the variation function of each parameter, calculate the parameter values ​​of a certain area at 3:00, 6:00, 9:00, 12:00, 15:00, 18:00, 21:00 and 24:00 in one day, and substitute the obtained parameter values ​​into the formula (1) of step S2 to calculate the transient equivalent resistivity at 3:00, 6:00, 9:00, 12:00, 15:00, 18:00, 21:00 and 24:00. 0.365 respectively , 0.234 , 0.212 , 0.414 , 0.315 , 0.603 , 0.315 , 0.513 .

[0069] Step S3: Calculate the equivalent resistance R of the wind power generation system after it enters the transient state. eq , the calculation method is shown in formula (2):

[0070] (2);

[0071] Where, Indicates the equivalent resistivity of the wind power generation system after entering the transient state, represents the air density function of the area where the wind power generation system is located, T(t) represents the temperature function of the area where the wind power generation system is located with respect to time t, H(t) represents the humidity function of the area where the wind power generation system is located with respect to time t, L and S are both constants, representing the equivalent length and equivalent cross-sectional area of ​​the line in the wind power generation system, respectively.

[0072] In this embodiment, the air density function, temperature function, humidity function, equivalent length of the line in the wind power generation system, and equivalent cross-sectional area of ​​the line in the wind power generation system are as shown in step S1 in this embodiment, and the transient equivalent resistivity Take the calculation result of step S2 in this embodiment.

[0073] Calculate the parameter values ​​of a certain area at 3:00, 6:00, 9:00, 12:00, 15:00, 18:00, 21:00 and 24:00 in one day, and calculate the parameter values ​​and transient equivalent resistivity. Substitute into formula (2) in step S3 to calculate the transient equivalent resistance R at 3:00, 6:00, 9:00, 12:00, 15:00, 18:00, 21:00, and 24:00 eq 20.201 respectively , 17.996 , 22.345 , 21.264 , 18.236 , 23.569 , 19.329 , 19.227 .

[0074] Step S4: Calculate the equivalent reactance X after the wind power generation system enters the transient state. eq , the calculation method is shown in formula (3):

[0075] (3);

[0076] Where R eq represents the equivalent resistance of the wind power generation system after entering the transient state, f represents the rated frequency of the wind power generation system during production operation, T(t) represents the temperature of the area where the wind power generation system is located as a function of time t, H(t) represents the humidity of the area where the wind power generation system is located as a function of time t, I(t) represents the light intensity of the area where the wind power generation system is located as a function of time t, L and S are both constants, representing the equivalent length and equivalent cross-sectional area of ​​the line in the wind power generation system, respectively.

[0077] In this embodiment, the temperature function, humidity function, light intensity function, equivalent length of the line in the wind power generation system, and equivalent cross-sectional area of ​​the line in the wind power generation system are as shown in step S1 in this embodiment. The rated frequency f=50.795Hz and transient equivalent resistance R eq Take the calculation result of step S3 in this embodiment.

[0078] Calculate the parameter values ​​of a certain area at 3:00, 6:00, 9:00, 12:00, 15:00, 18:00, 21:00, and 24:00 in one day, and use the parameter values ​​and transient equivalent resistance R eq And the rated frequency f is substituted into the formula (3) of step S4 to calculate the transient equivalent reactance X at 3 o'clock, 6 o'clock, 9 o'clock, 12 o'clock, 15 o'clock, 18 o'clock, 21 o'clock and 24 o'clock. eq 12.351 respectively , 14.758 , 14.569 , 13.887 , 16.217 , 14.997 , 17.258 , 15.331 .

[0079] Step S5: Using the transient equivalent resistance R of the wind power generation system calculated in steps S3 and S4 eq and transient equivalent reactance X eq , calculate the equivalent impedance Z of the wind power generation system after entering the transient state eq ;

[0080] Step S5.1: Calculate the equivalent impedance Z of the wind power system after it enters the transient state eq The modulus value , the calculation method is shown in formula (4):

[0081] (4);

[0082] Where R eq It represents the equivalent resistance of the wind power generation system after entering the transient state, X eq It represents the equivalent reactance of the wind power generation system after entering the transient state, f represents the rated frequency of the wind power generation system during production operation, L and S are both constants, representing the equivalent length and equivalent cross-sectional area of ​​the line in the wind power generation system respectively.

[0083] In this embodiment, the equivalent length of the line in the wind power generation system and the equivalent cross-sectional area of ​​the line in the wind power generation system are as shown in step S1 in this embodiment, the rated frequency f=50.795Hz when the wind power generation system is in production and operation, and the transient equivalent resistance R eq and transient equivalent reactance X eq The calculation results in step S3 and step S4 are obtained respectively.

[0084] The equivalent length L of the line in the wind power generation system, the equivalent cross-sectional area S of the line in the wind power generation system, and the transient equivalent resistance R calculated in step S3 are eq , the transient equivalent reactance X calculated in step S4 eq And the rated frequency f of the wind power generation system during production operation is substituted into the formula (4) of step S5.1 to calculate the transient equivalent impedance Z at 3:00, 6:00, 9:00, 12:00, 15:00, 18:00, 21:00 and 24:00 eq The modulus value 28.995 respectively , 30.147 , 29.365 , 31.259 , 28.669 , 33.992 , 35.963 , 34.254 .

[0085] Step S5.2: Calculate the equivalent impedance Z of the wind power generation system after it enters the transient state eq Impedance angle , the calculation method is shown in formula (5):

[0086] (5);

[0087] Where, Indicates the equivalent impedance Z of the wind power generation system after entering the transient state eq The modulus value, R eq It represents the equivalent resistance of the wind power generation system after entering the transient state, X eq It represents the equivalent reactance of the wind power generation system after entering the transient state, and f represents the rated frequency of the wind power generation system during production operation.

[0088] In this embodiment, the rated frequency f of the wind power generation system during production operation is 50.795 Hz, and the transient equivalent resistance R eq and transient equivalent reactance X eq Take the calculation results in step S3 and step S4 respectively. The rated frequency f of the wind power generation system during production operation and the transient equivalent resistance R calculated in step S3 are eq , the transient equivalent reactance X calculated in step S4 eq Substitute into formula (5) in step S5.2 to calculate the transient equivalent impedance Z at 3:00, 6:00, 9:00, 12:00, 15:00, 18:00, 21:00, and 24:00 eq Impedance angle They are 45.103°, 55.234°, 49.687°, 43.664°, 60.579°, 49.562°, 57.589° and 55.208° respectively.

[0089] Step S6: verifying the accuracy of the wind power system transient equivalent impedance prediction based on PSCAD;

[0090] A wind power generation system and its transient model are built in PSCAD. The parameters of the wind power generation system and its transient model include: the angular velocity of the wind turbine WT, the power of the doubly fed induction generator DFIG, the power of the wind power generation system side converter WTSC, the value of the capacitor C, the power of the grid side converter GSC, the power of the step-up transformer T, and the number n of wind power generation system units. The transient equivalent impedance of the wind power generation system is simulated and verified in PSCAD. If the simulation results are 、 and the value calculated in step S5 of the prediction method 、 If formula (6) and formula (7) are satisfied, it means that the method of the present invention is effective;

[0091] (6);

[0092] (7);

[0093] Where, is the modulus of the transient equivalent impedance of the wind power generation system calculated by the present invention, is the modulus of the transient equivalent impedance of the wind power system calculated by PSCAD simulation, is the impedance angle of the transient equivalent impedance of the wind power generation system calculated by the present invention, is the impedance angle of the transient equivalent impedance of the wind power system calculated by PSCAD simulation.

[0094] In this embodiment, a wind power generation system and its transient model are constructed in PSCAD. The angular velocity of the wind turbine WT is 22 r / min, the power of the doubly fed induction generator DFIG is 2.2 MW, the power of the wind power generation system side converter WTSC is 2.5 MW, the value of the capacitor C is 0.15 F, the power of the grid side converter GSC is 2.3 MW, the power of the step-up transformer T is 3 MW, and the number of wind power generation system units is 8.

[0095] According to the set parameters, PSCAD simulation is used to calculate the transient equivalent impedance modulus and impedance angle of the wind power system at 3:00, 6:00, 9:00, 12:00, 15:00, 18:00, 21:00 and 24:00 respectively. and 44.773°, 31.013 and 55.002°, 29.894 and 49.993°, 31.566 and 44.231°, 29.292 and 60.024°, 33.688 and 49.936°, 36.608 and 58.023°, 34.691 and 55.152°, the calculation results satisfy the formula (6) and formula (7) in step S6. Through the above analysis and calculation, it can be concluded that a wind power system transient equivalent impedance prediction method based on PSCAD can achieve effective prediction of the wind power system transient equivalent impedance.

[0096] In summary, as the scale of wind power generation systems becomes larger and larger, their transient processes become more and more complex. Therefore, the requirements for wind power generation system transient equivalent impedance prediction methods are getting higher and higher. The present invention provides a wind power generation system transient equivalent impedance prediction method based on PSCAD. This method fully considers the influence of various parameters such as wind speed, air density, atmospheric pressure, light intensity, temperature, humidity, equivalent cross-sectional area of ​​the line, equivalent length of the line on the transient process of the wind power generation system. It not only achieves effective prediction of the transient equivalent impedance of the wind power generation system, but also improves the prediction performance, meeting the dual requirements of accuracy and speed of the prediction method. This method can track the transient process of the wind power generation system online, monitor the constant change of equivalent impedance over time in real time, and lay the foundation for calculating data such as power angle, active power, reactive power, voltage, current, etc. in the transient process, which is of great significance to improving the transient stability of the wind power generation system.

[0097] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A wind power system transient equivalent impedance prediction method based on PSCAD is characterized by: The following steps are involved: S1. Real-time monitoring and acquisition of parameters affecting the transient equivalent impedance of the wind power generation system, including: Environmental parameters: wind speed V(t), air density ρ(P, T(t), H(t)), atmospheric pressure P, light intensity I(t), temperature T(t), humidity H(t); System parameters: line equivalent cross-sectional area SS and equivalent length L; S2. Calculate the equivalent resistivity of the wind power generation system after it enters the transient state ; S3. Calculate the equivalent resistance R of the wind power generation system after it enters the transient state eq ; S4. Calculate the equivalent reactance X after the wind power generation system enters the transient state eq ; S5, the transient equivalent resistance R of the wind power generation system calculated using S3 and S4 eq and transient equivalent reactance X eq , calculate the equivalent impedance Z of the wind power generation system after entering the transient state eq ; S6. Verify the accuracy of transient equivalent impedance prediction of wind power generation system based on PSCAD.

2. The method for predicting transient equivalent impedance of a wind power generation system based on PSCAD according to claim 1, characterized in that: In step S1, wind speed V(t), light intensity I(t), temperature T(t), and humidity H(t) are functions of time t, and air density It is a function of atmospheric pressure P, temperature T(t), and humidity H(t).

3. The PSCAD-based transient equivalent impedance prediction method for a wind power generation system according to claim 1, characterized in that: In step S2, the equivalent resistivity is calculated , calculated as follows: (1)； Where, T(t) represents the temperature of the area where the wind power generation system is located as a function of time t, H(t) represents the humidity of the area where the wind power generation system is located as a function of time t, V(t) represents the wind speed of the area where the wind power generation system is located as a function of time t, and I(t) represents the light intensity of the area where the wind power generation system is located as a function of time t. It represents the air density function of the area where the wind power generation system is located, and P represents the atmospheric pressure in the area where the wind power generation system is located. This parameter is a constant.

4. The PSCAD-based transient equivalent impedance prediction method for a wind power generation system according to claim 1, characterized in that: In step S3, the equivalent resistance R is calculated. eq , calculated as follows: (2)； Where, Indicates the equivalent resistivity of the wind power generation system after entering the transient state, represents the air density function of the area where the wind power generation system is located, T(t) represents the temperature function of the area where the wind power generation system is located with respect to time t, H(t) represents the humidity function of the area where the wind power generation system is located with respect to time t, L and S are both constants, representing the equivalent length and equivalent cross-sectional area of ​​the line in the wind power generation system, respectively.

5. The PSCAD-based transient equivalent impedance prediction method for a wind power generation system according to claim 1, characterized in that: In step S4, the equivalent reactance X is calculated. eq , calculated as follows: (3)； Where R eq represents the equivalent resistance of the wind power generation system after entering the transient state, f represents the rated frequency of the wind power generation system during production operation, T(t) represents the temperature of the area where the wind power generation system is located as a function of time t, H(t) represents the humidity of the area where the wind power generation system is located as a function of time t, I(t) represents the light intensity of the area where the wind power generation system is located as a function of time t, L and S are both constants, representing the equivalent length and equivalent cross-sectional area of ​​the line in the wind power generation system, respectively.

6. The method for predicting transient equivalent impedance of a wind power generation system based on PSCAD according to claim 1, characterized in that: The step S5 includes: Step S5.1: Calculate the modulus of the equivalent impedance Zeq after the wind power generation system enters the transient state , calculated as follows: (4)； Where R eq It represents the equivalent resistance of the wind power generation system after entering the transient state, X eq represents the equivalent reactance of the wind power generation system after entering the transient state, f represents the rated frequency of the wind power generation system during production operation, L and S are constants, representing the equivalent length and equivalent cross-sectional area of ​​the line in the wind power generation system respectively; Step S5.2: Calculate the equivalent impedance Z of the wind power generation system after it enters the transient state eq Impedance angle , calculated as follows: (5)； Where, Indicates the equivalent impedance Z of the wind power generation system after entering the transient state eq The modulus value, R eq It represents the equivalent resistance of the wind power generation system after entering the transient state, X eq It represents the equivalent reactance of the wind power generation system after entering the transient state, and f represents the rated frequency of the wind power generation system during production operation.

7. The method for predicting transient equivalent impedance of a wind power generation system based on PSCAD according to claim 6, characterized in that: The equivalent cross-sectional area S and equivalent length L of the line are determined according to actual line parameters of the wind power generation system.

8. The PSCAD-based transient equivalent impedance prediction method for a wind power generation system according to claim 1, characterized in that: In step S6, a wind power generation system and its transient model are constructed in PSCAD. The parameters of the wind power generation system and its transient model include: the angular velocity of the wind turbine WT, the power of the doubly fed induction generator DFIG, the power of the wind power generation system side converter WTSC, the value of the capacitor C, the power of the grid side converter GSC, the power of the step-up transformer T, and the number n of wind power generation system units.

9. The method for predicting transient equivalent impedance of a wind power generation system based on PSCAD according to claim 8, characterized in that: The transient equivalent impedance of the wind power generation system is simulated and verified in PSCAD. If the simulation results 、 and the value calculated in step S5 of the prediction method 、 If formula (6) and formula (7) are satisfied, it means that the method of the present invention is effective; (6)； (7)； Where, is the modulus of the transient equivalent impedance of the wind power generation system calculated by the present invention, is the modulus of the transient equivalent impedance of the wind power system calculated by PSCAD simulation, is the impedance angle of the transient equivalent impedance of the wind power generation system calculated by the present invention, is the impedance angle of the transient equivalent impedance of the wind power system calculated by PSCAD simulation.

10. The PSCAD-based transient equivalent impedance prediction method for wind power generation systems according to claim 9, characterized in that: The parameters of the PSCAD model in step S6 include: Wind turbine angular speed range: 18–25 r / min; Doubly-fed induction generator power range: 1.5–3 MW; The number of system units n≥5.

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