Method for suppressing subsynchronous oscillation of double-fed wind turbine based on online sequence impedance spectrum identification

Abstract

The present application relates to the field of doubly-fed wind turbine subsynchronous oscillation suppression, and particularly relates to a doubly-fed wind turbine subsynchronous oscillation suppression method based on online sequence impedance spectrum identification. The content includes: real-time acquisition of three-phase voltage and current analog signals of a doubly-fed wind turbine grid-connected point, and extraction of positive sequence voltage and current components; based on the positive sequence voltage and current components, frequency domain positive sequence impedance is obtained, a frequency domain positive sequence impedance spectrum is generated, and a subsynchronous oscillation frequency is extracted; based on the subsynchronous oscillation frequency, in combination with the frequency domain positive sequence impedance spectrum, a frequency compensation output control signal is calculated, a positive sequence impedance dynamic adjustment formula at the subsynchronous oscillation frequency point is constructed, and the dynamic adjustment amount of the positive sequence impedance at the subsynchronous oscillation frequency point is calculated. The problem that the traditional subsynchronous oscillation suppression method is difficult to accurately identify the subsynchronous oscillation frequency, cannot adapt to the oscillation characteristics of the low-frequency region of the doubly-fed wind turbine, cannot realize targeted and accurate suppression, and cannot meet the real-time control requirements of engineering is solved.

Description

Technical Field

[0001] This invention relates to the field of subsynchronous oscillation suppression of doubly-fed wind turbines, and more particularly to a method for suppressing subsynchronous oscillations of doubly-fed wind turbines based on line sequence impedance spectrum identification. Background Technology

[0002] As the global energy structure transitions towards cleaner and lower-carbon energy, wind power, as a core component of renewable energy, is seeing its installed capacity and penetration rate in the power system gradually increase, becoming a crucial support for ensuring energy supply and achieving "dual-carbon" goals. Among these, the doubly-fed induction generator (DFIG) wind turbine, with its variable-speed constant-frequency operation characteristics, high energy conversion efficiency, and good grid adaptability, has been widely used in wind power systems, becoming the mainstream model in the current wind power field. It undertakes the important task of large-scale wind power grid connection and transmission, promoting the large-scale development and engineering implementation of wind power technology. However, with the large-scale grid connection of DFIG wind turbines, the dynamic characteristics of the power system are becoming increasingly complex, and various operational risks are becoming more prominent. Subsynchronous oscillation (SSO) is one of the typical problems faced by DFIG wind turbines during operation.

[0003] In the low-frequency operating region, the electrical structure of doubly-fed induction generator (DFIG) wind turbines is prone to resonance with grid parameters, easily inducing subsynchronous oscillations. Subsynchronous oscillations pose a serious threat to grid stability and the safety of the wind turbine itself. They not only cause voltage and current distortions in the grid, affecting the normal power supply quality of the power system, but may also damage key electrical components of the wind turbine, shorten its service life, and even trigger large-scale grid failures, thus hindering the safe and stable operation of DFIG wind turbines and the further large-scale development of wind power.

[0004] Currently, there are various methods for suppressing subsynchronous oscillations in the industry, but they generally suffer from drawbacks such as complex design, cumbersome debugging, and slow response. The core shortcoming is that it is difficult to accurately identify the subsynchronous oscillation frequency, cannot adapt to the oscillation characteristics of the low-frequency region of the doubly fed fan, cannot achieve targeted and precise suppression, and cannot meet the engineering real-time control requirements. Summary of the Invention

[0005] This invention provides a method for suppressing subsynchronous oscillations in doubly-fed wind turbines based on online sequence impedance spectrum identification. This method addresses the technical problems of traditional subsynchronous oscillation suppression methods, which are unable to accurately identify the subsynchronous oscillation frequency, adapt to the oscillation characteristics of doubly-fed wind turbines in the low-frequency region, achieve targeted and precise suppression, and meet the requirements of engineering real-time control.

[0006] The present invention provides a method for suppressing subsynchronous oscillations in doubly-fed wind turbines based on online sequence impedance spectrum identification, comprising the following steps:

[0007] S1. Real-time acquisition of three-phase voltage and current analog signals at the grid connection point of the doubly fed wind turbine, and extraction of positive sequence voltage and positive sequence current components; based on the positive sequence voltage and positive sequence current components, obtain the frequency domain positive sequence impedance; based on the frequency domain positive sequence impedance, generate the frequency domain positive sequence impedance spectrum, and extract the subsynchronous oscillation frequency.

[0008] S2. Based on the subsynchronous oscillation frequency and combined with the frequency domain positive sequence impedance spectrum, calculate the frequency compensation output control signal; based on the frequency compensation output control signal, construct the dynamic adjustment formula for the positive sequence impedance at the subsynchronous oscillation frequency point, and calculate the dynamic adjustment amount of the positive sequence impedance at the subsynchronous oscillation frequency point.

[0009] Preferably, S1 specifically includes:

[0010] The three-phase voltage and current analog signals of the collected doubly fed wind turbine grid connection point are sequentially subjected to anti-aliasing filtering, ADC conversion and symmetrical component transformation to extract the positive sequence voltage component and positive sequence current component; the positive sequence voltage component and positive sequence current component are subjected to discrete Fourier transform to obtain the frequency domain positive sequence impedance; the discretized data corresponding to the frequency domain positive sequence impedance are subjected to frequency domain interpolation to generate the frequency domain positive sequence impedance spectrum.

[0011] Preferably, S1 specifically includes:

[0012] Based on the positive-sequence impedance spectrum in the frequency domain, combined with the subsynchronous frequency band, the subsynchronous oscillation frequency is extracted using a joint criterion of peak amplitude and second-order rate of change of impedance phase.

[0013] Preferably, S2 specifically includes:

[0014] Using the subsynchronous oscillation frequency and the real-time frequency domain positive sequence impedance value at the subsynchronous oscillation frequency as input, and combining impedance deviation exponential grade correction with frequency band impedance attenuation constraint, a formula for calculating the frequency normalization compensation control signal is constructed, and the frequency compensation output control signal is calculated.

[0015] Preferably, S2 specifically includes:

[0016] In the frequency normalization compensation control signal calculation formula, the frequency domain positive sequence reference impedance at the subsynchronous oscillation frequency is calculated under the steady-state condition of the power grid without oscillation, and used as the reference impedance. The impedance deviation is quantified, and the impedance correction intensity is dynamically adjusted in combination with the exponential correction term.

[0017] Preferably, S2 specifically includes:

[0018] The dynamic adjustment formula for the positive sequence impedance at the subsynchronous oscillation frequency point integrates the frequency compensation output control signal, impedance deviation correction, and frequency domain change rate prediction to obtain the dynamic adjustment amount of the positive sequence impedance at the subsynchronous oscillation frequency point.

[0019] Preferably, S2 specifically includes:

[0020] In the dynamic adjustment formula for the positive sequence impedance at the subsynchronous oscillation frequency, the positive sequence target impedance at the subsynchronous oscillation frequency is generated based on the rated operating parameters provided by the wind turbine manufacturer; and based on the positive sequence target impedance at the subsynchronous oscillation frequency, an impedance deviation correction term, a frequency domain rate of change prediction constraint term, and a deviation amplitude constraint term are generated.

[0021] Preferably, S2 specifically includes:

[0022] The dynamic adjustment of the positive sequence impedance at the subsynchronous oscillation frequency point is output to the control loop of the rotor-side converter and grid-side converter of the doubly fed wind turbine. The modulation ratio, phase angle and current command of the converter are automatically adjusted by the converter control unit built into the doubly fed wind turbine, thereby changing the equivalent impedance characteristics of the wind turbine grid connection port in real time.

[0023] The beneficial effects of the technical solution of the present invention are:

[0024] 1. Accurately identify oscillation frequency: By using the positive sequence impedance spectrum identification method, the subsynchronous oscillation frequency in the low-frequency region of the doubly fed wind turbine can be accurately captured, making up for the shortcomings of inaccurate frequency identification in traditional methods.

[0025] 2. The suppression effect is highly efficient and reliable. By introducing impedance deviation index graded correction and frequency band impedance attenuation constraint, the frequency compensation output control signal is calculated. By integrating the frequency compensation output control signal, impedance deviation correction and frequency domain change rate prediction, the dynamic adjustment amount of the positive sequence impedance at the subsynchronous oscillation frequency point is obtained, so as to achieve a dual improvement in adjustment response speed and stability, effectively avoiding the threat of oscillation to grid stability and wind turbine safety.

[0026] 3. Ensures system safety and stability, effectively avoids problems such as grid voltage and current distortion and wind turbine component damage, helps double-fed wind turbines operate safely and stably, promotes the large-scale grid connection of wind power, and meets the needs of clean and low-carbon energy transformation. Attached Figure Description

[0027] Figure 1 This is a flowchart of the doubly fed wind turbine subsynchronous oscillation suppression method based on online sequence impedance spectrum identification as described in this invention. Detailed Implementation

[0028] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0030] The following description, in conjunction with the accompanying drawings, details the specific scheme of the doubly fed wind turbine subsynchronous oscillation suppression method based on online sequence impedance spectrum identification provided by this invention.

[0031] See attached document Figure 1 The diagram illustrates a flowchart of a method for suppressing subsynchronous oscillations in a doubly-fed wind turbine based on online sequence impedance spectrum identification, according to an embodiment of the present invention. The method includes the following steps:

[0032] S1. Real-time acquisition of three-phase voltage and current analog signals at the grid connection point of the doubly fed wind turbine, and extraction of positive sequence voltage and positive sequence current components; based on the positive sequence voltage and positive sequence current components, obtain the frequency domain positive sequence impedance; based on the frequency domain positive sequence impedance, generate the frequency domain positive sequence impedance spectrum, and extract the subsynchronous oscillation frequency.

[0033] First, the three-phase voltage and three-phase current analog signals at the grid connection point of the doubly-fed induction generator (DFIG) are acquired in real time. A second-order Butterworth low-pass filter with a cutoff frequency of 100Hz is used for anti-aliasing filtering to remove high-frequency noise and harmonic interference. Then, an analog-to-digital converter (ADC) module is used to convert the analog signals to digital signals, obtaining discretized time-domain voltage and current signals. To eliminate the interference of three-phase asymmetry and zero-sequence and negative-sequence components on impedance identification accuracy, the Fortischus symmetric component transform method is first used to perform symmetric component transformation on the discretized time-domain voltage and current signals, extracting the positive-sequence voltage and positive-sequence current components that characterize the main electrical characteristics of the DFIG grid connection.

[0034] Subsequently, a Discrete Fourier Transform was performed on the positive-sequence voltage and positive-sequence current components to obtain the positive-sequence voltage and positive-sequence current in the frequency domain. Based on the complete small-signal modeling principle of doubly-fed induction generators, a positive-sequence impedance model was constructed. The frequency-domain positive-sequence impedance was calculated by the ratio of the positive-sequence voltage to the positive-sequence current. The calculation formula is as follows: ,in, The positive sequence impedance in the frequency domain is a parameter characterizing the electrical characteristics of the grid-connected port of a doubly-fed wind turbine. The positive sequence voltage in the frequency domain; This is the positive sequence current in the frequency domain; It is a fixed imaginary unit and a fundamental constant for frequency domain operations; It is the angular frequency, which is directly related to the signal frequency. The oscillation frequency variable during the online operation phase is obtained by performing discrete Fourier transform analysis on the collected positive sequence voltage and positive sequence current components. Its range is within the subsynchronous frequency band (5Hz to 50Hz according to the "Guidelines for the Safety and Stability of Power Systems").

[0035] To accurately locate the characteristic frequency of the subsynchronous oscillation, the positive sequence impedance in the frequency domain is then analyzed. The corresponding discretized data is used for frequency domain interpolation using the existing Sinc interpolation algorithm, converting the discrete frequency point data into a continuous, high-resolution frequency domain positive-sequence impedance spectrum. To facilitate the analysis of impedance characteristics at different frequencies, an optimized joint criterion of peak amplitude and second-order rate of change of impedance phase is used to extract the subsynchronous oscillation frequency. The specific formula is as follows:

[0036]

[0037] in, This is the subsynchronous oscillation frequency; The frequency variable is used to traverse the subsynchronous frequency band from 5Hz to 50Hz and filter out the subsynchronous oscillation frequency. When the frequency is The positive sequence impedance value in the frequency domain represents the electrical characteristics of the coupling between the wind turbine and the power grid, reflecting the voltage and current relationship between the wind turbine and the power grid, and is taken from the positive sequence impedance spectrum in the frequency domain. When the frequency is The positive-sequence impedance phase reflects the phase difference between current and voltage, revealing the impedance characteristics of the wind turbine's grid connection port and its phase relationship with the power grid. It is obtained through frequency domain phase extraction of the positive-sequence impedance, with a value range of [value missing]. ; The term represents the absolute value of the second-order phase derivative, indicating the phase with respect to the positive-sequence impedance. With frequency The second derivative of the change in impedance phase reflects the absolute value of the second-order rate of change of the impedance phase. Represents the differential operator; To define the range, the maximum value is to be calculated within the subsynchronous frequency band of 5~50Hz, in order to avoid interference from irrelevant frequency points.

[0038] S2. Based on the subsynchronous oscillation frequency and combined with the frequency domain positive sequence impedance spectrum, calculate the frequency compensation output control signal; based on the frequency compensation output control signal, construct the dynamic adjustment formula for the positive sequence impedance at the subsynchronous oscillation frequency point, and calculate the dynamic adjustment amount of the positive sequence impedance at the subsynchronous oscillation frequency point.

[0039] After obtaining the subsynchronous oscillation frequency, the subsynchronous oscillation frequency and the real-time positive-sequence impedance value in the frequency domain at that frequency are used as input parameters to construct a frequency-normalized compensation control signal calculation formula. This formula targets and adjusts the frequency domain positive-sequence impedance spectrum to adapt to the engineering operation requirements of the doubly-fed induction generator (DFIG) wind turbine. The frequency-normalized compensation control signal calculation formula uses the rated power frequency of the DFIG grid-connected system as the normalization benchmark. By introducing a combination of impedance deviation graded correction and frequency-corresponding impedance attenuation constraints, it achieves precise pre-adjustment of the impedance at the subsynchronous oscillation frequency point, obtaining the frequency-compensated output control signal. This achieves a dual improvement in compensation accuracy and the stability of the DFIG grid-connected system. The frequency-normalized compensation control signal calculation formula is as follows:

[0040]

[0041] in, Output control signal for frequency compensation; For the secondary synchronous oscillation frequency The frequency domain positive sequence impedance at that point is taken from the frequency domain positive sequence impedance spectrum; Under the steady-state condition of the power grid without oscillations, at the subsynchronous oscillation frequency The positive-sequence reference impedance in the frequency domain is used as a reference impedance to quantize the current positive-sequence impedance in the frequency domain. The impedance deviation is used to determine the compensation amplitude. The data comes from the no-load commissioning stage before the doubly fed wind turbine is connected to the grid. Specifically, when the wind turbine is no-load, a small amplitude excitation frequency within the sub-synchronous frequency band of 5Hz to 50Hz, with an amplitude not exceeding 5% of the rated voltage, is applied to its grid connection port. The excitation frequency is obtained by traversing the sub-synchronous frequency band according to a preset step size (such as 0.1Hz). The positive sequence voltage component and positive sequence current component of the grid in oscillation-free steady state at each excitation frequency are collected in real time. The positive sequence voltage component and positive sequence current component are processed by the existing discrete Fourier transform method and the above frequency domain positive sequence impedance calculation method to obtain the frequency domain positive sequence impedance at each excitation frequency. Based on the frequency domain positive sequence impedance at all excitation frequencies, a frequency domain positive sequence reference impedance is constructed. The rated power frequency of the doubly fed wind turbine grid-connected system is used as the reference frequency for frequency normalization to eliminate impedance deviation differences under different excitation frequencies. The impedance attenuation coefficient in the frequency band characterizes the subsynchronous oscillation frequency. The attenuation of the impedance amplitude at a given point relative to the maximum impedance amplitude in the 5Hz to 50Hz frequency band is calculated using the following formula: ,in In the positive sequence impedance spectrum of the frequency domain within the 5Hz to 50Hz frequency band Maximum amplitude, The range of values ​​is ; This is the impedance deviation normalization term at the subsynchronous oscillation frequency point, used to unify the impedance deviation at different oscillation frequencies and obtain the standardized impedance deviation. This is a term combining impedance deviation grading correction and frequency-corresponding impedance attenuation constraint, with an exponential correction term controlled by the frequency band impedance attenuation coefficient. It can dynamically adjust the impedance correction force according to the magnitude of the impedance deviation;

[0042] Next, the frequency compensation output control signal will be... Substituting the values ​​into the dynamic adjustment formula for the positive sequence impedance at the subsynchronous oscillation frequency, this formula integrates the frequency compensation output control signal, impedance deviation correction, and frequency domain rate of change prediction to obtain the dynamic adjustment amount of the positive sequence impedance at the subsynchronous oscillation frequency. This achieves a dual improvement in adjustment response speed and stability, adapting to the oscillation suppression requirements under complex operating conditions of doubly-fed induction generators. The specific formula for the dynamic adjustment of the positive sequence impedance at the subsynchronous oscillation frequency is as follows:

[0043]

[0044] in, For the secondary synchronous oscillation frequency The dynamic adjustment amount of the corresponding positive sequence impedance is used to characterize the current real-time frequency domain positive sequence impedance. The magnitude and direction of the adjustments; The frequency of secondary synchronous oscillation The positive-sequence target impedance that satisfies the Nyquist stability criterion is calculated based on the rated operating parameters (such as rated power, rated voltage, and rated current) provided by the wind turbine manufacturer, in accordance with the "Guidelines for the Safety and Stability of Power Systems" and using the power system impedance Nyquist stability criterion method. The maximum amplitude of the positive-sequence impedance spectrum in the frequency domain within the 5Hz to 50Hz frequency band; This is an impedance deviation correction item, which can accurately correct impedance deviations and avoid over- or under-adjustment of impedance. As a frequency domain rate of change prediction constraint, it can combine the impedance deviation amplitude to predict the impedance change trend and make precise adjustments. The subsynchronous oscillation frequency The rate of change of the positive-sequence impedance spectrum in the frequency domain is used to characterize the dynamic change trend of the positive-sequence impedance with frequency, and is used to predict the direction of impedance adjustment in advance. This is a deviation amplitude constraint term, used to constrain the magnitude of trend prediction and avoid overly aggressive predictions.

[0045] The dynamic adjustment amount of the calculated positive sequence impedance The output is directly connected to the rotor-side converter and grid-side converter control loop of the doubly fed wind turbine. The converter control unit built into the doubly fed wind turbine automatically adjusts the modulation ratio, phase angle and current command of the converter, and changes the equivalent impedance characteristics of the wind turbine grid connection port in real time, so that the impedance at the subsynchronous oscillation frequency can be matched to the stable operating range, thereby achieving the subsynchronous oscillation suppression effect.

[0046] In summary, a method for suppressing subsynchronous oscillations in doubly-fed wind turbines based on online sequence impedance spectrum identification has been completed.

[0047] The order of the embodiments is for illustrative purposes only and does not represent the superiority or inferiority of the embodiments. The processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0048] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for suppressing subsynchronous oscillations in doubly-fed wind turbines based on online sequence impedance spectrum identification, characterized in that, Includes the following steps: S1. Real-time acquisition of three-phase voltage and current analog signals at the grid connection point of the doubly fed wind turbine, and extraction of positive sequence voltage and positive sequence current components; The frequency domain positive-sequence impedance is obtained based on the positive-sequence voltage component and the positive-sequence current component. Based on the positive sequence impedance in the frequency domain, a positive sequence impedance spectrum in the frequency domain is generated, and the subsynchronous oscillation frequency is extracted. S2. Based on the subsynchronous oscillation frequency and combined with the frequency domain positive sequence impedance spectrum, calculate the frequency compensation output control signal; Based on the frequency compensation output control signal, a dynamic adjustment formula for the positive sequence impedance at the subsynchronous oscillation frequency point is constructed, and the dynamic adjustment amount of the positive sequence impedance at the subsynchronous oscillation frequency point is calculated.

2. The method for suppressing subsynchronous oscillations of a doubly-fed wind turbine based on online sequence impedance spectrum identification according to claim 1, characterized in that, S1 specifically includes: The three-phase voltage and current analog signals of the collected doubly fed wind turbine grid connection point are sequentially subjected to anti-aliasing filtering, ADC conversion and symmetrical component transformation to extract the positive sequence voltage component and positive sequence current component; the positive sequence voltage component and positive sequence current component are subjected to discrete Fourier transform to obtain the frequency domain positive sequence impedance; the discretized data corresponding to the frequency domain positive sequence impedance are subjected to frequency domain interpolation to generate the frequency domain positive sequence impedance spectrum.

3. The method for suppressing subsynchronous oscillations of a doubly-fed wind turbine based on online sequence impedance spectrum identification according to claim 2, characterized in that, S1 specifically includes: Based on the positive-sequence impedance spectrum in the frequency domain, combined with the subsynchronous frequency band, the subsynchronous oscillation frequency is extracted using a joint criterion of peak amplitude and second-order rate of change of impedance phase.

4. The method for suppressing subsynchronous oscillations of a doubly-fed wind turbine based on online sequence impedance spectrum identification according to claim 1, characterized in that, S2 specifically includes: Using the subsynchronous oscillation frequency and the real-time frequency domain positive sequence impedance value at the subsynchronous oscillation frequency as input, and combining impedance deviation exponential grade correction with frequency band impedance attenuation constraint, a formula for calculating the frequency normalization compensation control signal is constructed, and the frequency compensation output control signal is calculated.

5. The method for suppressing subsynchronous oscillations of a doubly-fed wind turbine based on online sequence impedance spectrum identification according to claim 4, characterized in that, S2 specifically includes: In the frequency normalization compensation control signal calculation formula, the frequency domain positive sequence reference impedance at the subsynchronous oscillation frequency is calculated under the steady-state condition of the power grid without oscillation, and used as the reference impedance. The impedance deviation is quantified, and the impedance correction intensity is dynamically adjusted in combination with the exponential correction term.

6. The method for suppressing subsynchronous oscillations of a doubly-fed wind turbine based on online sequence impedance spectrum identification according to claim 1, characterized in that, S2 specifically includes: The dynamic adjustment formula for the positive sequence impedance at the subsynchronous oscillation frequency point integrates the frequency compensation output control signal, impedance deviation correction, and frequency domain change rate prediction to obtain the dynamic adjustment amount of the positive sequence impedance at the subsynchronous oscillation frequency point.

7. The method for suppressing subsynchronous oscillations of a doubly-fed wind turbine based on online sequence impedance spectrum identification according to claim 6, characterized in that, S2 specifically includes: In the dynamic adjustment formula for the positive sequence impedance at the subsynchronous oscillation frequency, the positive sequence target impedance at the subsynchronous oscillation frequency is generated based on the rated operating parameters provided by the wind turbine manufacturer; and based on the positive sequence target impedance at the subsynchronous oscillation frequency, an impedance deviation correction term, a frequency domain rate of change prediction constraint term, and a deviation amplitude constraint term are generated.

8. The method for suppressing subsynchronous oscillations of a doubly-fed wind turbine based on online sequence impedance spectrum identification according to claim 1, characterized in that, S2 specifically includes: The dynamic adjustment of the positive sequence impedance at the subsynchronous oscillation frequency point is output to the control loop of the rotor-side converter and grid-side converter of the doubly fed wind turbine. The modulation ratio, phase angle and current command of the converter are automatically adjusted by the converter control unit built into the doubly fed wind turbine, thereby changing the equivalent impedance characteristics of the wind turbine grid connection port in real time.

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