A control method for suppressing subsynchronous oscillation of a doubly-fed wind turbine and related devices

Abstract

The embodiment of the application discloses a control method for inhibiting subsynchronous oscillation of a doubly-fed fan and related equipment, relates to the technical field of stability control of power systems, and directly estimates a subsynchronous frequency based on inherent parameters such as series compensation capacitance reactance, equivalent inductance and grid synchronous frequency, so that the influence of grid resistance parameter change on the estimated value of the subsynchronous frequency is excluded; based on the estimated value of the subsynchronous frequency obtained above, a frequency spectrum analysis range is quickly locked; through fast Fourier decomposition of rotor current and in combination with an amplitude comparison strategy in the preset frequency spectrum analysis range, an oscillation frequency, namely a subsynchronous resonance frequency, is accurately locked, and the subsynchronous resonance frequency in the rotor side control system of the doubly-fed fan is filtered out, so that oscillation is inhibited.

Description

Technical Field

[0001] This invention relates to the field of power system stability control technology, and in particular to a control method and related equipment for suppressing subsynchronous oscillations of doubly fed wind turbines. Background Technology

[0002] With the ever-increasing global demand for clean energy, wind power, as a crucial component of new energy generation, is showing immense promise. Wind farms are typically located in remote areas, far from load centers. To address power transmission issues, series capacitor compensation technology is widely used in transmission lines to improve transmission capacity and stability. However, this technology also introduces the potential risk of subsynchronous oscillations. Once subsynchronous oscillations occur, they can easily disrupt the normal operation of doubly-fed induction generators (DFIGs). If effective suppression measures are not taken, it may lead to wind turbine failures, subsequently causing extremely adverse effects on the entire wind power transmission system. Summary of the Invention

[0003] In view of this, the present invention provides a control method and related equipment for suppressing subsynchronous oscillations of a doubly fed fan.

[0004] The specific technical solution of the first embodiment of the present invention is as follows: a control method for suppressing subsynchronous oscillation of a doubly-fed induction generator (DFIG), the method comprising: obtaining an estimated value of the subsynchronous frequency of the DFIG in a three-phase coordinate system based on the series compensation capacitor reactance of the DFIG, the equivalent inductive reactance of the DFIG and the grid side, and the grid synchronization frequency; using a vector control method based on stator voltage d-axis orientation, obtaining the rotor current of the DFIG on the rotor side based on the stator current of the DFIG and a preset relationship between the stator current and the rotor current; performing fast Fourier decomposition on the rotor current to obtain harmonic components of the rotor current at different frequencies in the dq coordinate system; converting the target harmonic component with the frequency of the estimated subsynchronous frequency into a frequency estimate of the subsynchronous resonant component of the rotor current in the dq coordinate system; comparing the amplitudes of each frequency component within a preset spectrum analysis range centered on the frequency estimate of the subsynchronous resonant component; determining the frequency corresponding to the frequency component with the largest amplitude as the subsynchronous resonant frequency of the DFIG rotor-side control system; and filtering out the subsynchronous resonant frequency in the DFIG rotor-side control system.

[0005] Preferably, the subsynchronous frequency estimate is obtained using the following formula:

[0006]

[0007] in, This is the estimated value of the subsynchronous frequency. The series compensation capacitor reactance, The equivalent inductive reactance of the doubly-fed wind turbine and the grid side, The power grid synchronization frequency is [value].

[0008] Preferably, filtering out the subsynchronous resonant frequency in the rotor-side control system of the doubly-fed wind turbine includes: designing a notch filter with the subsynchronous resonant frequency as the notch angular frequency in the transfer function of the notch filter; and using the notch filter to filter out the subsynchronous resonant component corresponding to the subsynchronous resonant frequency in the rotor-side control system of the doubly-fed wind turbine.

[0009] Preferably, the step of using the notch filter to filter out the subsynchronous resonance component corresponding to the subsynchronous resonance frequency in the rotor-side control system of the doubly fed wind turbine includes: connecting the notch filter to the current loop of the rotor-side converter of the rotor-side control system of the doubly fed wind turbine to filter out the subsynchronous resonance component.

[0010] Preferably, the relationship between the preset sub-current and the rotor current is as follows:

[0011]

[0012] in, For the mutual inductance between the stator and rotor, For stator inductance, This represents the d-axis component of the rotor current. The d-axis component of the stator current. This represents the q-axis component of the rotor current. The q-axis component of the stator current; the d-axis component of the rotor current and the q-axis component constitute the rotor current.

[0013] Preferably, the transfer function of the notch filter is obtained using the following formula:

[0014]

[0015] in, The transfer function is... For the Laplace operator, The subsynchronous resonant frequency is... This is the preset notch factor.

[0016] Preferably, the subsynchronous resonant frequency is obtained using the following formula:

[0017]

[0018] in, The subsynchronous resonant frequency is... The estimated value of the subsynchronous frequency. The power grid synchronization frequency is denoted as .

[0019] The specific technical solution of the second embodiment of the present invention is as follows: a control system for suppressing subsynchronous oscillation of a doubly-fed induction generator (DFIG), the system comprising: a subsynchronous frequency estimation module, a rotor current acquisition module, a decomposition module, a frequency estimation module, a comparison module, a subsynchronous resonant frequency acquisition module, and a filtering module; the subsynchronous frequency estimation module is used to acquire the subsynchronous frequency estimate of the DFIG in a three-phase coordinate system based on the series compensation capacitor reactance of the DFIG, the equivalent inductive reactance of the DFIG and the grid side, and the grid synchronization frequency; the rotor current acquisition module is used for a vector control method based on stator voltage d-axis orientation, wherein the rotor current of the DFIG is obtained based on the stator current of the DFIG and a preset relationship between the stator current and the rotor current; The decomposition module is used to perform fast Fourier decomposition on the rotor current to obtain harmonic components of the rotor current at different frequencies in the dq coordinate system; the frequency estimation module is used to convert the target harmonic component with the frequency of the subsynchronous frequency estimation value into the frequency estimation value of the subsynchronous resonance component of the rotor current in the dq coordinate system; the comparison module is used to compare the amplitude of each frequency component within a preset spectrum analysis range with the frequency estimation value of the subsynchronous resonance component as the center; the subsynchronous resonance frequency acquisition module is used to determine the frequency corresponding to the frequency component with the largest amplitude as the subsynchronous resonance frequency of the doubly-fed wind turbine rotor-side control system; the filtering module is used to filter out the subsynchronous resonance frequency in the doubly-fed wind turbine rotor-side control system.

[0020] The specific technical solution of the third embodiment of the present invention is as follows: a control device for suppressing subsynchronous oscillation of a doubly fed wind turbine, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of any one of the methods described in the first embodiment of this application.

[0021] The specific technical solution of the fourth embodiment of the present invention is as follows: a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor performs the steps of the method as described in any one of the first embodiments of this application.

[0022] Implementing the embodiments of the present invention will have the following beneficial effects:

[0023] This invention directly estimates the subsynchronous frequency based on inherent parameters such as series compensation capacitor reactance, equivalent inductive reactance, and grid synchronization frequency, eliminating the influence of grid resistance parameter changes on the estimated subsynchronous frequency. Based on the obtained subsynchronous frequency estimate, the spectrum analysis range is quickly locked. By performing fast Fourier decomposition of the rotor current and combining it with an amplitude comparison strategy within the preset spectrum analysis range, the oscillation frequency, i.e., the subsynchronous resonant frequency, is accurately locked. The subsynchronous resonant frequency in the doubly-fed wind turbine rotor-side control system is then filtered out to suppress oscillation. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A flowchart illustrating the steps of a control method to suppress subsynchronous oscillations in a doubly-fed fan;

[0026] Figure 2 This is a schematic diagram of a doubly fed wind turbine connected to the grid via series compensation.

[0027] Figure 3 This is a schematic diagram of the equivalent circuit for the subsynchronous frequency.

[0028] Figure 4 This is a block diagram of the rotor-side control of a doubly-fed wind turbine.

[0029] Figure 5 Bode plot of a notch filter;

[0030] Figure 6 The control block diagram of the d-axis current loop of the rotor-side converter of a doubly fed wind turbine with a notch filter connected to the inner current loop of the converter.

[0031] Figure 7 A block diagram of the q-axis current loop control for connecting a notch filter to the inner current loop of the rotor-side converter of a doubly fed wind turbine.

[0032] Figure 8 A schematic diagram of the control system for suppressing subsynchronous oscillations in a doubly-fed fan;

[0033] Figure 9 This is a diagram of the internal structure of a computer device.

[0034] Among them, 201 is the subsynchronous frequency estimation acquisition module; 202 is the rotor current acquisition module; 203 is the decomposition module; 204 is the frequency estimation acquisition module; 205 is the comparison module; 206 is the subsynchronous resonant frequency acquisition module; and 207 is the filtering module. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0036] The terms "first," "second," etc., used in the specification, claims, and drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally include steps or modules not listed, or may optionally include other steps or modules inherent to such processes, methods, products, or apparatus.

[0037] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0038] Please see Figure 1 This is a flowchart illustrating the steps of a control method for suppressing subsynchronous oscillations in a doubly-fed wind turbine according to the first embodiment of this application, thereby achieving oscillation suppression. The method includes:

[0039] Step 101: Based on the series compensation capacitor reactance of the doubly fed wind turbine... Equivalent inductance of doubly-fed wind turbine and grid side Synchronized frequency with the power grid Obtain the estimated subsynchronous frequency of the doubly fed wind turbine in a three-phase coordinate system. ;

[0040] Step 102: Vector control method based on stator voltage d-axis orientation, wherein the rotor side of the doubly fed wind turbine obtains the rotor current according to the stator current of the doubly fed wind turbine and the preset relationship between the stator current and the rotor current;

[0041] Step 103: Perform fast Fourier decomposition on the rotor current to obtain the harmonic components of the rotor current at different frequencies in the dq coordinate system.

[0042] Step 104: Set the frequency to the estimated value of the subsynchronous frequency. The target harmonic component is converted into the frequency estimate of the subsynchronous resonant component of the rotor current in the dq coordinate system. ;

[0043] Step 105: Estimate the frequency of the subsynchronous resonance component in the frequency spectrum. Centered on the target frequency, compare the amplitudes of each frequency component within the preset spectrum analysis range;

[0044] Step 106: Determine the frequency corresponding to the frequency component with the largest amplitude as the subsynchronous resonant frequency of the doubly fed wind turbine rotor-side control system.

[0045] Step 107: Filter out the subsynchronous resonant frequency in the rotor-side control system of the doubly fed wind turbine.

[0046] Specifically, the first step is to obtain the series compensation capacitor reactance. Equivalent inductance of doubly-fed wind turbine and grid side Synchronized frequency with the power grid Among them, series compensation capacitor reactance The equivalent inductive reactance of the doubly-fed wind turbine and the grid side can be obtained through direct measurement. The equivalent inductive reactance of a doubly-fed wind turbine can be measured by injecting a disturbance signal; grid synchronization frequency. The common setpoint is typically 50Hz. Based on the series compensation capacitor reactance connected to the doubly-fed induction generator (DFIG), the equivalent inductive reactance of the DFIG and the grid side, and the grid synchronization frequency, the estimated subsynchronous frequency of the DFIG in the three-phase coordinate system is calculated, providing crucial foundational data for subsequent analysis. The system operates based on a stator voltage d-axis oriented vector control method. The DFIG rotor-side controller acquires the stator current signal in real time. Based on a pre-established model of the relationship between stator current and rotor current, derived through extensive experimental and theoretical analysis, the required rotor current is precisely calculated, ensuring accurate and timely control. The calculated rotor current undergoes Fast Fourier Decomposition (FFT). Using a high-performance digital signal processor, the harmonic components of the rotor current at different frequencies in the dq coordinate system are acquired quickly. The target harmonic component, whose frequency corresponds to the estimated subsynchronous frequency, is carefully selected and converted into the estimated frequency of the subsynchronous resonant component of the rotor current in the dq coordinate system. In the spectrum analysis phase, using this estimated frequency of the subsynchronous resonant component as the center, within a preset spectrum analysis range, professional spectrum analysis software is used to compare the amplitudes of each frequency component. After careful investigation, the frequency component with the largest amplitude was identified, and its corresponding frequency was determined as the subsynchronous resonance frequency of the doubly-fed induction generator (DFIG) rotor-side control system. In the DFIG rotor-side control system, based on the determined subsynchronous resonance frequency, a suitable filter was designed and implemented to filter out this subsynchronous resonance frequency, effectively suppressing the subsynchronous resonance phenomenon, ensuring the stable and reliable operation of the DFIG, and improving the power generation efficiency and power quality of the wind farm.

[0047] Specifically, firstly, a simplified equivalent circuit for the subsynchronous frequency of the doubly-fed induction generator (DFIG) is established based on the DFIG-connected series-compensated grid system. A schematic diagram of the DFIG-connected series-compensated grid system is shown below. Figure 2 As shown, a simplified equivalent circuit for the subsynchronous frequency is obtained through a simplified analysis of a doubly fed wind turbine connected to a series-compensated grid system, such as... Figure 3As shown, the subsynchronous frequency estimate of the control system on the rotor side of the doubly-fed induction generator (DFIG) is estimated based on this equivalent circuit. .in, Figure 3 slip ratio The calculation formula is: ,in, The rotor speed frequency of a doubly fed wind turbine is generally... ,so Based on the obtained By locking the range of FFT spectrum analysis, fast Fourier decomposition is performed on the rotor current in the dq coordinate system to determine the subsynchronous resonant frequency. Figure 3 middle, The slip at the subsynchronous frequency; , These are the rotor resistance and stator resistance of the doubly-fed induction generator, respectively. The equivalent resistance of the rotor-side converter. , These are the rotor leakage reactance and stator leakage reactance at the subsynchronous frequency, respectively. , These are the equivalent resistance on the grid side and the grid-side reactance at subsynchronous frequency (including line reactance and transformer leakage reactance), respectively. It is the equivalent impedance at the subsynchronous frequency as viewed from the power grid side.

[0048] Specifically, FFT is based on the Discrete Fourier Transform (DFT) theory, which converts discrete-time signals into discrete-frequency signals, thereby extracting the various frequency components in the signal.

[0049] For a discrete signal of length N, its DFT is defined as:

[0050]

[0051] in, This represents the complex amplitude of the k-th frequency component, corresponding to the frequency. , It is the sampling frequency.

[0052] The Fast Fourier Transform (FFT) is an efficient algorithm for computing the DFT. Its basic idea is to decompose a DFT of length N into multiple DFTs of smaller length, thereby greatly reducing the amount of computation.

[0053] Based on sampling frequency and number of sampling points N Calculate the frequency axis:

[0054]

[0055] To calculate the amplitude of each frequency component in the spectrum, the modulus of the spectrum is usually taken:

[0056]

[0057] in, and These are the spectral components. The real and imaginary parts.

[0058] When the three-phase rotor current of a doubly-fed fan is decomposed by Fast Fourier Transform, the frequency of the output is... harmonic components When the frequency of the subsynchronous resonance component is estimated by transforming it to the dq coordinate system, the frequency estimate of the subsynchronous resonance component can be obtained. Based on frequency Centered on the component, compare the amplitudes of the frequency components near it, and determine the frequency corresponding to the frequency component with the largest amplitude as the subsynchronous resonant frequency.

[0059] The method in this embodiment directly estimates the subsynchronous frequency based on inherent parameters such as series compensation capacitor reactance, equivalent inductive reactance, and grid synchronization frequency, eliminating the influence of grid resistance parameter changes on the estimated subsynchronous frequency. Based on the obtained subsynchronous frequency estimate, the spectrum analysis range is quickly locked. By performing fast Fourier decomposition of the rotor current and combining it with an amplitude comparison strategy within the preset spectrum analysis range, the oscillation frequency, i.e., the subsynchronous resonant frequency, is accurately locked. The subsynchronous resonant frequency in the doubly-fed wind turbine rotor-side control system is then filtered out to suppress oscillation.

[0060] In a specific embodiment, the subsynchronous frequency estimate The following formula is used to obtain it:

[0061]

[0062] in, This is the estimated value of the subsynchronous frequency. The series compensation capacitor reactance, The equivalent inductive reactance of the doubly-fed wind turbine and the grid side, Let be the synchronization frequency of the power grid. Specifically, this formula is derived by specifying the series compensation capacitor reactance. And the equivalent inductive reactance of the doubly-fed wind turbine and the grid side. Synchronized frequency with the power grid The relationship is used to calculate the estimated value of the subsynchronous frequency. Compared to some rough estimation methods, this embodiment comprehensively considers the electrical parameters of key components in the system, enabling a more accurate determination of the subsynchronous frequency. This provides accurate foundational data for subsequent analysis and processing of subsynchronous resonance phenomena. For example, in actual wind farm systems, accurate subsynchronous frequency estimation helps to accurately identify frequency points that may trigger resonance, avoiding misjudgments or omissions caused by frequency estimation errors.

[0063] In a specific embodiment, filtering out the subsynchronous resonant frequency in the doubly-fed induction generator (DFIG) rotor-side control system includes: designing a notch filter using the subsynchronous resonant frequency as the notch angular frequency in the transfer function of the notch filter; and using the notch filter to filter out the subsynchronous resonant component corresponding to the subsynchronous resonant frequency in the DFIG rotor-side control system. Specifically, the determined subsynchronous resonant frequency is used as the notch angular frequency in the transfer function of the notch filter, allowing the notch filter to be precisely designed for this specific frequency. In the DFIG rotor-side control system, the subsynchronous resonant component can severely affect system stability and power quality. Through this precise design, the notch filter can effectively filter out the component corresponding to the subsynchronous resonant frequency, minimizing its adverse effects on the system.

[0064] In a specific embodiment, the step of using the notch filter to filter out the subsynchronous resonance component corresponding to the subsynchronous resonance frequency in the rotor-side control system of the doubly fed wind turbine includes: connecting the notch filter to the current loop of the rotor-side converter of the rotor-side control system of the doubly fed wind turbine to filter out the subsynchronous resonance component.

[0065] Specifically, based on the rotor-side control strategy, the location of the adaptive notch filter is determined. First, vector control based on stator voltage d-axis orientation is adopted to obtain the relationship between the stator output power and the rotor dq-axis current of the doubly-fed induction generator (DFIG).

[0066]

[0067] in, and These represent the stator voltage and the stator flux linkage vector, respectively. The active power output by the stator. This represents the d-axis component of the rotor current. Let Q be the q-axis component of the rotor current, and let Q be the reactive power output of the stator.

[0068] Active and reactive power can be controlled by controlling the d-axis and q-axis components of the rotor current, respectively. The rotor-side converter adopts dual closed-loop control, with the outer loop being the power loop and the inner loop being the current loop. The control block diagram is shown below. Figure 4 As shown.

[0069] Reference values ​​for the d-axis and q-axis components of the corresponding rotor current can be obtained from the power outer loop. The actual rotor current's d-axis and q-axis components can be obtained through the current feedback loop. The difference between the reference components and the actual components is passed through a PI controller, and coupled with the d- and q-axis rotor voltage coupling terms, the d- and q-axis components of the rotor voltage can be obtained. Thus, the actual rotor voltage can be controlled by the converter to meet the grid operation requirements.

[0070] In a specific embodiment, the relationship between the preset sub-current and the rotor current is as follows:

[0071]

[0072] in, For the mutual inductance between the stator and rotor, For stator inductance, This represents the d-axis component of the rotor current. The d-axis component of the stator current. This represents the q-axis component of the rotor current. The q-axis component of the stator current; the d-axis component of the rotor current and the q-axis component constitute the rotor current.

[0073] In a specific embodiment, the transfer function of the notch filter is obtained using the following formula:

[0074]

[0075] in, The transfer function is... For the Laplace operator, The subsynchronous resonant frequency is... This is the preset notch factor.

[0076] In a specific embodiment, the subsynchronous resonant frequency is obtained using the following formula:

[0077]

[0078] in, The subsynchronous resonant frequency is... The estimated value of the subsynchronous frequency. The grid synchronization frequency is given. The notch bandwidth can be adjusted by adjusting the notch factor of the notch filter. The Bode plot of the notch filter after adjusting the notch bandwidth is shown in the figure. Figure 5 As shown.

[0079] like Figure 6 and Figure 7 As shown, connecting the notch filter in this invention in series with the PI controller of the inner loop of the current control of the rotor-side converter of the doubly fed wind turbine can filter out the subsynchronous frequency component in the current error signal, while having no amplitude attenuation or phase delay for the DC component. This can effectively suppress the subsynchronous oscillation of the grid-connected doubly fed wind farm and improve the stability of the grid operation.

[0080] In a specific embodiment, please refer to Figure 8This is a schematic diagram of a control system for suppressing subsynchronous oscillations of a doubly-fed induction generator (DFIG) according to a second embodiment of this application. The system includes: a subsynchronous frequency estimation module 201, a rotor current acquisition module 202, a decomposition module 203, a frequency estimation module 204, a comparison module 205, a subsynchronous resonant frequency acquisition module 206, and a filtering module 207. The subsynchronous frequency estimation module 201 is used to acquire the estimated subsynchronous frequency of the DFIG in a three-phase coordinate system based on the series compensation capacitor reactance of the DFIG, the equivalent inductive reactance of the DFIG and the grid side, and the grid synchronization frequency. The rotor current acquisition module 202 is used for a vector control method based on the stator voltage d-axis orientation, whereby the rotor side of the DFIG obtains the stator current of the DFIG and a preset relationship between the stator current and the rotor current. The rotor current; the decomposition module 203 is used to perform fast Fourier decomposition on the rotor current to obtain harmonic components of the rotor current at different frequencies in the dq coordinate system; the frequency estimation module 204 is used to convert the target harmonic component with the frequency of the subsynchronous frequency estimation value into the frequency estimation value of the subsynchronous resonance component of the rotor current in the dq coordinate system; the comparison module 205 is used to compare the amplitude of each frequency component within a preset spectrum analysis range with the frequency estimation value of the subsynchronous resonance component as the center; the subsynchronous resonance frequency acquisition module 206 is used to determine the frequency corresponding to the frequency component with the largest amplitude as the subsynchronous resonance frequency of the doubly-fed wind turbine rotor-side control system; the filtering module 207 is used to filter out the subsynchronous resonance frequency in the doubly-fed wind turbine rotor-side control system.

[0081] In this embodiment, the system directly estimates the subsynchronous frequency based on inherent parameters such as series compensation capacitor reactance, equivalent inductive reactance, and grid synchronization frequency, eliminating the influence of grid resistance parameter changes on the estimated subsynchronous frequency. Based on the obtained subsynchronous frequency estimate, the spectrum analysis range is quickly locked. By performing fast Fourier decomposition of the rotor current and combining it with an amplitude comparison strategy within the preset spectrum analysis range, the oscillation frequency, i.e., the subsynchronous resonant frequency, is accurately locked. The subsynchronous resonant frequency in the doubly-fed wind turbine rotor-side control system is then filtered out to suppress oscillation.

[0082] In a specific embodiment, the third embodiment of this application provides a control device for suppressing subsynchronous oscillations in a doubly-fed induction generator (DFIG) wind turbine, including a memory and a processor. The memory stores a computer program, which, when executed by the processor, causes the processor to perform the steps of the method described in any one of the first embodiments of this application. In this embodiment, the device directly estimates the subsynchronous frequency based on inherent parameters such as series compensation capacitor reactance, equivalent inductive reactance, and grid synchronization frequency, eliminating the influence of grid resistance parameter changes on the estimated subsynchronous frequency. Based on the obtained subsynchronous frequency estimate, the spectrum analysis range is quickly locked. Through fast Fourier decomposition of the rotor current and combined with an amplitude comparison strategy within a preset spectrum analysis range, the oscillation frequency, i.e., the subsynchronous resonant frequency, is accurately locked, filtering out the subsynchronous resonant frequency in the DFIG rotor-side control system to suppress oscillations.

[0083] In a specific embodiment, the fourth embodiment of this application provides a computer-readable storage medium storing a computer program. The computer program, when executed by a processor, causes the processor to perform the steps of the method described in any one of the first embodiments of this application. In this embodiment, the storage medium directly estimates the subsynchronous frequency based on inherent parameters such as series compensation capacitor reactance, equivalent inductive reactance, and grid synchronization frequency, eliminating the influence of grid resistance parameter changes on the estimated subsynchronous frequency. Based on the obtained subsynchronous frequency estimate, the spectrum analysis range is quickly locked. Through fast Fourier decomposition of the rotor current and combined with an amplitude comparison strategy within a preset spectrum analysis range, the oscillation frequency, i.e., the subsynchronous resonant frequency, is accurately locked. This filters out the subsynchronous resonant frequency in the doubly-fed wind turbine rotor-side control system, thereby suppressing oscillation.

[0084] Figure 9 An internal structural diagram of a computer device in one embodiment is shown. This computer device can specifically be a terminal or a server. See also... Figure 9 The computer device includes a processor, memory, etc., connected via a system bus. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and may also store a computer program. When executed by the processor, this computer program causes the processor to implement the method described in this embodiment. The internal memory may also store a computer program, which, when executed by the processor, causes the processor to perform the method described in this embodiment. Those skilled in the art will understand that... Figure 9 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0085] The above embodiments merely illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A control method for suppressing subsynchronous oscillations in a doubly-fed induction generator (DFIG), characterized in that, The method includes: The estimated value of the subsynchronous frequency of the doubly-fed wind turbine in the three-phase coordinate system is obtained based on the series compensation capacitor reactance of the doubly-fed wind turbine, the equivalent inductive reactance of the doubly-fed wind turbine and the grid side, and the grid synchronization frequency. Based on the vector control method of stator voltage d-axis orientation, the rotor side of the doubly fed wind turbine obtains the rotor current according to the stator current of the doubly fed wind turbine and the preset relationship between stator current and rotor current. The rotor current is subjected to fast Fourier decomposition to obtain the harmonic components of the rotor current at different frequencies in the dq coordinate system. The target harmonic component with the frequency of the subsynchronous frequency estimate is converted into the frequency estimate of the subsynchronous resonant component of the rotor current in the dq coordinate system. Centered on the frequency estimate of the subsynchronous resonance component in the spectrum, the amplitudes of each frequency component within a preset spectrum analysis range are compared. The frequency corresponding to the frequency component with the largest amplitude is determined as the subsynchronous resonant frequency of the rotor-side control system of the doubly fed wind turbine. The subsynchronous resonant frequency in the rotor-side control system of the doubly fed wind turbine is filtered out.

2. The control method for suppressing subsynchronous oscillations of a doubly-fed wind turbine as described in claim 1, characterized in that, The estimated subsynchronous frequency is obtained using the following formula: in, The estimated value of the subsynchronous frequency. The series compensation capacitor reactance, The equivalent inductive reactance of the doubly-fed wind turbine and the grid side, The power grid synchronization frequency is [value].

3. The control method for suppressing subsynchronous oscillations of a doubly-fed wind turbine as described in claim 1, characterized in that, The step of filtering out the subsynchronous resonant frequency in the rotor-side control system of the doubly fed wind turbine includes: The notch filter is designed by using the subsynchronous resonant frequency as the notch angular frequency in the transfer function of the notch filter. The notch filter is used to filter out the subsynchronous resonance component corresponding to the subsynchronous resonance frequency in the rotor-side control system of the doubly fed wind turbine.

4. The control method for suppressing subsynchronous oscillations of a doubly-fed wind turbine as described in claim 3, characterized in that, The step of using the notch filter to filter out the subsynchronous resonance component corresponding to the subsynchronous resonance frequency in the rotor-side control system of the doubly fed wind turbine includes: The notch filter is connected to the current loop of the rotor-side converter of the doubly fed wind turbine rotor-side control system to filter out the subsynchronous resonance component.

5. The control method for suppressing subsynchronous oscillations of a doubly-fed induction generator (DFIG) as described in claim 1, characterized in that, The relationship between the preset sub-current and the rotor current is as follows: in, For the mutual inductance between the stator and rotor, For stator inductance, This represents the d-axis component of the rotor current. The d-axis component of the stator current. This represents the q-axis component of the rotor current. The q-axis component of the stator current; the d-axis component of the rotor current and the q-axis component constitute the rotor current.

6. The control method for suppressing subsynchronous oscillations of a doubly-fed wind turbine as described in claim 3, characterized in that, The transfer function of the notch filter is obtained using the following formula: in, The transfer function is... For the Laplace operator, The subsynchronous resonant frequency is... This is the preset notch factor.

7. The control method for suppressing subsynchronous oscillations of a doubly-fed fan as described in claim 6, characterized in that, The subsynchronous resonant frequency is obtained using the following formula: in, The subsynchronous resonant frequency is... The estimated value of the subsynchronous frequency. The power grid synchronization frequency is [value].

8. A control system for suppressing subsynchronous oscillations in a doubly-fed wind turbine, characterized in that, The system includes: a subsynchronous frequency estimation acquisition module, a rotor current acquisition module, a decomposition module, a frequency estimation acquisition module, a comparison module, a subsynchronous resonant frequency acquisition module, and a filtering module; The subsynchronous frequency estimation module is used to obtain the subsynchronous frequency estimation value of the doubly fed wind turbine in the three-phase coordinate system based on the series compensation capacitor reactance of the doubly fed wind turbine, the equivalent inductive reactance of the doubly fed wind turbine and the grid side, and the grid synchronization frequency. The rotor current acquisition module is used for a vector control method based on stator voltage d-axis orientation. The rotor side of the doubly fed wind turbine obtains the rotor current according to the stator current of the doubly fed wind turbine and the preset relationship between stator current and rotor current. The decomposition module is used to perform fast Fourier decomposition on the rotor current to obtain the harmonic components of the rotor current at different frequencies in the dq coordinate system. The frequency estimation module is used to convert the target harmonic component with the frequency of the subsynchronous frequency estimation into the frequency estimation of the subsynchronous resonant component of the rotor current in the dq coordinate system. The comparison module is used to compare the amplitudes of each frequency component within a preset spectrum analysis range, centered on the frequency estimate of the subsynchronous resonance component. The subsynchronous resonant frequency acquisition module is used to determine the frequency corresponding to the frequency component with the largest amplitude as the subsynchronous resonant frequency of the doubly fed wind turbine rotor-side control system. The filtering module is used to filter out the subsynchronous resonant frequency in the rotor-side control system of the doubly fed wind turbine.

9. A control device for suppressing subsynchronous oscillations in a doubly-fed wind turbine, comprising a memory and a processor, characterized in that, The memory stores a computer program that, when executed by the processor, causes the processor to perform the steps of the method as described in any one of claims 1-7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, the processor performs the steps of the method as described in any one of claims 1-7.

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