Online oscillation suppression method and device of doubly-fed wind turbine generator and doubly-fed wind turbine generator

Abstract

The invention discloses an online oscillation suppression method and device of a doubly-fed wind turbine generator and the doubly-fed wind turbine generator, and relates to the technical field of wind power generation. According to the method, monitoring voltage representing the voltage state of a power grid is obtained, frequency domain analysis is carried out on the monitoring voltage, the characteristics of inter-harmonic voltage in the voltage of the power grid are recognized in real time, and therefore whether the doubly-fed wind turbine generator oscillates or not is judged. And when oscillation is detected, an oscillation suppression mechanism is triggered to perform control intervention on the unit. The method does not need to depend on an accurate system model, can carry out the online detection and quick response of the oscillation of the power system under the condition of a weak power grid, overcomes the problems that the oscillation recognition is lagged and the suppression capability is insufficient in a high-proportion new energy access scene in an existing network tracking type and network constructing type control mode, and improves the reliability of the system. And the operation stability and the grid-connected reliability of the doubly-fed wind turbine generator in a weak power grid environment are improved.

Description

Technical Field

[0001] This invention relates to the field of wind power generation technology, and in particular to an online oscillation suppression method, device, and doubly-fed wind turbine generator set. Background Technology

[0002] Wind power, as a key technology in new energy sources, has received widespread attention worldwide. my country's complex topography makes its wind energy resources extremely abundant, providing favorable factors for the vigorous development of wind power.

[0003] Wind turbines are connected to the grid via power electronic converters. With the significant increase in installed wind turbine capacity, new energy power systems are gradually exhibiting "dual-high" characteristics: a high proportion of power electronic equipment and a high proportion of renewable energy. Since power electronic equipment itself lacks inertia support capabilities, its large-scale grid connection can lead to a lack of grid inertia, resulting in a weak grid with high impedance. Existing doubly-fed induction generator (DFIG) wind power systems use grid-following control methods. This control method lacks the ability to actively provide frequency and voltage support to the grid. When system inertia is insufficient, it can cause grid fluctuations or jeopardize the stable operation of the converter itself, failing to meet the requirements for stable operation of new energy grid-connected systems under weak grid conditions.

[0004] To address the instability issue of grid-connected doubly-fed induction generator (DFIG) wind turbines in weak grid environments, grid-connected control methods are gradually being promoted and applied in new energy equipment (such as...). Figure 1 However, grid-based control methods still cannot completely solve the problem of wide-band oscillation in power systems with a high proportion of new energy and weak grids. When the grid voltage fluctuates rapidly, the slow dynamic response of grid-based control often fails to suppress the oscillation and may even amplify the oscillating current of the generating units, causing equipment to disconnect from the grid or even malfunction.

[0005] Existing oscillation suppression technologies mainly fall into two categories: prevention and mitigation. Prevention methods rely on accurate system models and unit parameters, and it is difficult to effectively identify oscillation characteristics when the model is inaccurate. Mitigation methods, on the other hand, usually have a delayed response and poor timeliness, making it difficult to meet the needs for rapid identification and suppression of oscillations under conditions of high proportion of renewable energy and weak power grids.

[0006] Therefore, there is an urgent need for an online oscillation detection and suppression method suitable for doubly-fed induction generator (DFIG) wind turbines, in order to achieve real-time identification and rapid suppression of grid oscillations and improve the operational stability of wind turbines in weak grid environments. Summary of the Invention

[0007] The purpose of this invention is to provide an online oscillation suppression method, device, and doubly-fed induction generator (DFIG) wind turbine, which can detect and respond quickly to power system oscillations under weak grid conditions. This overcomes the problems of lagging oscillation identification and insufficient suppression capability of existing grid-connected and grid-connected control methods in scenarios with a high proportion of renewable energy access, and improves the operational stability and grid connection reliability of DFIG wind turbine in weak grid environments.

[0008] To address the aforementioned technical problems, this invention provides an online oscillation suppression method for doubly-fed induction generator (DFIG) wind turbines, comprising: acquiring a monitoring voltage for characterizing grid voltage; performing frequency domain analysis on the monitoring voltage to obtain frequency domain analysis results of the grid voltage; determining the interharmonic content in the grid voltage based on the frequency domain analysis results, and determining whether the DFIG wind turbine is oscillating; determining the interharmonic content in the grid voltage based on the frequency domain analysis results includes: statistically processing each frequency component in the frequency domain analysis results, extracting frequency components inconsistent with the fundamental frequency, and using the amplitude information of the frequency components inconsistent with the fundamental frequency as the interharmonic content, wherein the interharmonic content reflects the presence of abnormal frequency components in the grid voltage; when oscillation is determined to occur, triggering an oscillation suppression mechanism to perform oscillation suppression control on the DFIG wind turbine.

[0009] Optionally, frequency domain analysis is performed on the monitored voltage to obtain the frequency domain analysis results of the grid voltage, including: performing fast Fourier transform analysis on the monitored voltage to obtain a frequency domain analysis spectrum of the grid voltage; determining each interharmonic voltage in the grid voltage based on the frequency domain analysis spectrum of the grid voltage; when oscillation is determined to occur, the online oscillation suppression method of the doubly-fed induction generator further includes: sorting the amplitudes of all the interharmonic voltages and determining the frequencies corresponding to the interharmonic voltages with the largest amplitudes as the oscillation frequencies of the doubly-fed induction generator; triggering the oscillation suppression mechanism to perform oscillation suppression control on the doubly-fed induction generator, including: triggering the oscillation suppression mechanism according to the determined oscillation frequency, and performing oscillation suppression control on the doubly-fed induction generator according to the oscillation frequency.

[0010] Optionally, triggering the oscillation suppression mechanism according to the determined oscillation frequency and performing oscillation suppression control on the doubly-fed wind turbine according to the oscillation frequency includes: sending the oscillation frequency to the controller of the turbine-side converter and / or grid-side converter in the doubly-fed wind turbine, so that the controller executes the oscillation suppression mechanism according to the oscillation frequency.

[0011] Optionally, when the oscillation frequency is sent to the turbine-side converter in the doubly-fed wind turbine, the controller executes the oscillation suppression mechanism according to the oscillation frequency, including: acquiring the rotor current of the doubly-fed wind turbine; performing coordinate transformation on the rotor current to obtain a dq current; inputting the dq current into a resonant controller to obtain a resonant regulation voltage; and superimposing the resonant regulation voltage with the voltage signal output from the inner current loop of the turbine-side converter to generate a control signal for controlling the turbine-side converter.

[0012] Optionally, after generating the control signal for controlling the machine-side converter, the method further includes: performing coordinate inverse transformation and pulse width modulation on the control signal to generate a switching control signal, and using the switching control signal to control the switching devices in the machine-side converter.

[0013] Optionally, the transfer function of the resonant controller is: Among them, G R (s) is the transfer function of the resonant controller, K r ω is the gain coefficient of the resonant controller. i ω is the center frequency of the resonant controller. r The bandwidth affected by the resonant controller is s, where s is the Laplace operator; K r ω i ω r It is related to the oscillation frequency.

[0014] Optionally, acquiring a monitoring voltage for characterizing the grid voltage includes: acquiring the stator-side voltage of the doubly-fed wind turbine, and / or acquiring the output voltage of the grid-side converter; the monitoring voltage includes the stator-side voltage and / or the output voltage.

[0015] Optionally, frequency domain analysis is performed on the monitored voltage to obtain the frequency domain analysis result of the grid voltage, including: performing fast Fourier transform analysis on the monitored voltage to obtain a frequency domain analysis spectrum of the grid voltage; obtaining the total harmonic content of the grid voltage based on the frequency domain analysis spectrum of the grid voltage; and determining whether the doubly-fed wind turbine is oscillating, including: comparing the total harmonic content with a preset threshold, and determining that the doubly-fed wind turbine is oscillating when the total harmonic content is greater than the preset threshold.

[0016] To address the aforementioned technical problems, the present invention also provides an online oscillation suppression device for a doubly-fed wind turbine, comprising: a memory for storing a computer program; and a processor for implementing the steps of the online oscillation suppression method for a doubly-fed wind turbine as described above when executing the computer program.

[0017] To address the aforementioned technical problems, the present invention provides a doubly fed wind turbine generator set, including the online oscillation suppression device for the doubly fed wind turbine generator set as described above.

[0018] This invention provides an online oscillation suppression method, device, and doubly-fed induction generator (DFIG) wind turbine. By acquiring a monitoring voltage characterizing the grid voltage state and performing frequency domain analysis on the monitored voltage, the characteristics of interharmonic voltages in the grid voltage are identified in real time, thereby determining whether the DFIG wind turbine is oscillating. When oscillation is detected, an oscillation suppression mechanism is triggered to control and intervene in the turbine. This invention does not rely on a precise system model and can perform online detection and rapid response to power system oscillations under weak grid conditions. It overcomes the problems of lagging oscillation identification and insufficient suppression capability of existing grid-connected and grid-linked control methods in scenarios with a high proportion of renewable energy access, thus improving the operational stability and grid connection reliability of DFIG wind turbines in weak grid environments. Attached Figure Description

[0019] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic block diagram of a network-based control method in the prior art; Figure 2 A flowchart of an online oscillation suppression method for a doubly fed wind turbine provided by the present invention; Figure 3 A schematic block diagram illustrating online oscillation suppression for a doubly fed wind turbine generator provided by the present invention; Figure 4 This invention provides a block diagram for converter harmonic current control based on a resonant controller. Detailed Implementation

[0021] The core of this invention is to provide an online oscillation suppression method, device, and doubly-fed induction generator (DFIG) wind turbine, which can detect and respond quickly to power system oscillations under weak grid conditions. This overcomes the problems of lagging oscillation identification and insufficient suppression capability of existing grid-connected and grid-connected control methods in scenarios with a high proportion of new energy access, and improves the operational stability and grid connection reliability of DFIG wind turbine in weak grid environments.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0023] To make it easier to understand, let me first explain Figure 1 In the middle, V pcc I pcc These represent the grid connection point voltage and current, respectively; P and Q represent the active power and reactive power output of the wind turbine, respectively; P ref Q ref These are the active power command value and reactive power command value of the wind turbine generator, respectively; U ref This is the commanded voltage value at the grid connection point; U is the grid connection point angular frequency command value; U and θ are the electromotive force and phase generated by the power control loop within the grid-connected unit, respectively; U dc This is the DC bus voltage of the doubly fed wind power converter.

[0024] like Figure 2 As shown, in a first aspect, the present invention provides an online oscillation suppression method for a doubly-fed wind turbine generator, comprising: S11: Obtain the monitoring voltage used to characterize the grid voltage.

[0025] In this embodiment, the acquisition of monitoring voltage to characterize the grid voltage specifically involves the direct acquisition of the objective state of the grid voltage under the grid-connected operation of the doubly-fed induction generator (DFIG) wind turbine. Since grid voltage is the primary physical quantity for energy exchange and dynamic coupling between the turbine and the external power system, its amplitude, phase, and spectrum changes accurately reflect grid disturbances and oscillations. Therefore, acquiring the monitoring voltage allows for the characterization of the grid's operating state. This monitoring voltage can originate from, but is not limited to, the stator voltage of the DFIG wind turbine, the voltage at the grid connection point, or the converter output voltage. The acquired voltage signal is stored in time-series format for subsequent processing and analysis.

[0026] In a specific embodiment, the monitoring voltage can be acquired using a voltage sensor installed at the electrical connection node of the doubly-fed induction generator (or converted by a voltage conversion module before being acquired by the voltage sensor). The sensor continuously samples the AC voltage and outputs a digital voltage signal. The sampling process can continue during normal operation of the unit, independent of external triggering conditions, ensuring that the acquired monitoring voltage covers various dynamic changes that may occur during grid operation. Since the monitoring voltage comes directly from the actual operating voltage on the grid side, its changes are not affected by unit control parameters or model assumptions, and it can completely preserve potential oscillation information in the grid.

[0027] Furthermore, in this embodiment, the monitored voltage is used as a raw observation, without any prior frequency assumptions or feature screening. Instead, it is provided to subsequent steps as a raw or pre-processed voltage signal. In this way, the fundamental, harmonic, and interharmonic components contained in the monitored voltage are fully preserved, providing fundamental data support for subsequent analysis of the frequency domain characteristics of the power grid voltage, and ensuring that the subsequent oscillation judgment process is based on the actual power grid voltage characteristics.

[0028] S12: Perform frequency domain analysis on the monitored voltage to obtain the frequency domain analysis results of the grid voltage.

[0029] In this embodiment, frequency domain analysis of the monitored voltage involves analyzing the energy distribution of the voltage signal along the frequency dimension based on the obtained time-series signal. Since oscillations generated during power grid operation typically manifest as specific frequency components in the voltage signal other than the fundamental frequency, frequency domain analysis can convert the monitored voltage from a time-domain form to a frequency-domain form, allowing different frequency components to be represented in the spectrum. In this embodiment, frequency domain analysis can employ, but is not limited to, Discrete Fourier Transform, Fast Fourier Transform, or equivalent spectral analysis methods to process the monitored voltage signal and obtain frequency domain analysis results reflecting the frequency composition of the power grid voltage.

[0030] In its implementation, this embodiment samples the monitored voltage within a preset time window and performs frequency domain analysis independently within each time window to obtain the frequency domain analysis results of the grid voltage for the corresponding time period. These results can be represented in spectral form, where different frequency points correspond to different voltage amplitude information, reflecting the proportion of each frequency component in the monitored voltage. In this way, the fundamental, harmonic, and potentially interharmonic components contained in the monitored voltage can all be reflected in the frequency domain analysis results.

[0031] Furthermore, in this embodiment, the frequency domain analysis results serve as an objective description of the frequency characteristics of the monitored voltage, and their content does not depend on pre-set oscillation frequencies or system model parameters. Regardless of whether there is a single-frequency disturbance or multiple-frequency superimposed disturbances in the grid voltage, the frequency domain analysis results can reflect the corresponding frequency positions and their amplitude changes.

[0032] S13: Determine the interharmonic content in the grid voltage based on the frequency domain analysis results, and determine whether the doubly fed wind turbine unit oscillates.

[0033] This embodiment describes the process of determining the state of the power grid voltage frequency characteristics. The frequency domain analysis results include the amplitude distribution of the monitored voltage at different frequency positions. This embodiment identifies the interharmonic components and their corresponding amplitudes in the power grid voltage by identifying frequency components at non-fundamental frequencies. The interharmonic content reflects the presence of abnormal frequency components in the power grid voltage and can be used as a basis for determining whether the power grid is in an oscillating state.

[0034] In a specific embodiment, this embodiment can perform statistical processing on each frequency component in the frequency domain analysis results, extract frequency components that are inconsistent with the fundamental frequency, and use their amplitude information as interharmonic content for calculation and characterization. Interharmonic content can be expressed, but is not limited to, using a single interharmonic amplitude, a combination of multiple interharmonic amplitudes, or a normalized comprehensive index. Based on the interharmonic content, this embodiment judges the current operating status of the doubly-fed wind turbine. When the interharmonic content meets preset judgment conditions, the doubly-fed wind turbine is considered to be oscillating.

[0035] Furthermore, in this embodiment, the oscillation judgment process does not rely on grid structure parameters or generator mathematical models, but is directly based on the frequency domain characteristics of the monitored voltage. Regardless of whether the oscillation manifests as a single frequency component or a superposition of multiple frequency components, it can be reflected by changes in interharmonic content, thus establishing the oscillation judgment based on the actual spectral characteristics of the grid voltage.

[0036] S14: When oscillation is detected, the oscillation suppression mechanism is triggered to perform oscillation suppression control on the doubly fed wind turbine.

[0037] This embodiment describes the process of intervening in the unit's operating status after an oscillation state is identified. This step uses the aforementioned oscillation judgment result as the trigger condition. When the judgment result indicates that the doubly-fed induction generator (DFIG) wind turbine is in an oscillation state, this embodiment enters the oscillation suppression control process; when no oscillation occurs, the original operating status of the unit is maintained, and the oscillation suppression mechanism is not executed.

[0038] In a specific embodiment, the oscillation suppression mechanism can be triggered by outputting a suppression command to the control loop of the doubly-fed induction generator (DFIG) to put the generator into the corresponding oscillation suppression operation mode, or by superimposing control quantities for oscillation suppression on the original control. This oscillation suppression mechanism can be adjusted based on, but is not limited to, current, voltage, or power-related quantities. Its triggering time is directly determined by the oscillation judgment result, ensuring a clear correspondence between the oscillation suppression action and the oscillation state.

[0039] Furthermore, in this embodiment, by immediately triggering the oscillation suppression mechanism upon detecting an oscillation, the doubly-fed induction generator (DFIG) wind turbine responds to abnormal frequency components of the grid voltage, suppressing the continuation or spread of the oscillation. This process uses real-time detection results as input, does not rely on manual intervention, and enables the oscillation suppression control process to be automatically executed as the grid operating state changes.

[0040] As an optional embodiment, frequency domain analysis is performed on the monitored voltage to obtain the frequency domain analysis results of the grid voltage, including: performing fast Fourier transform analysis on the monitored voltage to obtain the frequency domain analysis spectrum of the grid voltage; determining the interharmonic voltages in the grid voltage based on the frequency domain analysis spectrum of the grid voltage; when oscillation is determined to occur, the online oscillation suppression method for the doubly-fed induction generator (DFIG) wind turbine further includes: sorting the amplitudes of all interharmonic voltages and determining the frequencies corresponding to the interharmonic voltages with the largest amplitudes as the oscillation frequencies of the DFIG wind turbine; triggering the oscillation suppression mechanism to perform oscillation suppression control on the DFIG wind turbine, including: triggering the oscillation suppression mechanism according to the determined oscillation frequency and performing oscillation suppression control on the DFIG wind turbine according to the oscillation frequency.

[0041] In this embodiment, the frequency domain analysis of the monitored voltage employs Fast Fourier Transform (FFT) analysis, converting the monitored voltage from a time-domain signal to a frequency-domain signal, resulting in a frequency domain analysis spectrum of the grid voltage reflecting its frequency distribution characteristics. This spectrum, with frequency on the horizontal axis and voltage amplitude on the vertical axis, visually reflects the magnitude and distribution of each frequency component in the monitored voltage. In this embodiment, the analysis window length and update period of the FFT can be set according to the sampling frequency of the monitored voltage, enabling the spectrum to continuously reflect the changes in the grid voltage spectrum.

[0042] In this embodiment, the determination of interharmonic voltages in the grid voltage based on the grid voltage frequency domain analysis spectrum is achieved by identifying frequency components in the spectrum that deviate from the fundamental frequency. For each identified interharmonic frequency point, this embodiment extracts its corresponding voltage amplitude and records this amplitude as the corresponding interharmonic voltage. These interharmonic voltages can exist individually or in multiples simultaneously; their quantity and distribution are determined by the current grid operating state, and the frequency domain analysis spectrum fully preserves this information.

[0043] When oscillation is detected, this embodiment sorts the amplitudes of all interharmonic voltages. The sorting process can proceed from largest to smallest amplitude to reflect the relative proportion of each interharmonic in the monitored voltage. In the sorting results, interharmonic voltages with larger amplitudes typically correspond to the dominant abnormal frequency components in the grid voltage. Therefore, this embodiment determines the frequencies corresponding to several interharmonic voltages with the largest amplitudes as the oscillation frequencies of the doubly-fed induction generator (DFIG). These frequencies can be set according to actual needs, and may include, but are not limited to, one or more.

[0044] In this embodiment, the oscillation frequency is used as a key parameter to trigger the oscillation suppression mechanism. Once the oscillation frequency is determined, this embodiment triggers the oscillation suppression mechanism based on the oscillation frequency, causing the doubly-fed induction generator (DFIG) wind turbine to enter an oscillation suppression control process corresponding to the current oscillation state. This triggering process is based on real-time frequency domain analysis results and does not rely on a preset fixed frequency, ensuring that the oscillation suppression control remains consistent with the actual oscillation frequency in the grid voltage.

[0045] Furthermore, in this embodiment, the oscillation suppression control process regulates the doubly-fed induction generator (DFIG) according to the oscillation frequency, enabling the generator's operating state to respond to abnormal frequency components in the grid voltage. This control regulation can continue until the corresponding interharmonic amplitude changes in the frequency domain analysis results or the oscillation state is resolved. This embodiment achieves targeted processing of the oscillation frequency in this way, ensuring that the oscillation suppression mechanism always maintains a correspondence with the monitored grid voltage spectrum characteristics.

[0046] It is important to understand that this embodiment chooses interharmonics as the object of oscillation identification and analysis, rather than whole harmonics, because the oscillations caused or participated in by doubly-fed induction generators under weak grid conditions are usually not strictly locked to integer multiples of the grid fundamental frequency. Their frequency positions are easily affected by grid impedance, power electronic control characteristics, and changes in operating conditions, manifesting as non-integer multiples of the whole harmonic frequency. Whole harmonics are mostly related to the characteristics of power electronic switches or the inherent characteristics of known equipment, and their frequencies are relatively fixed, while abnormal frequency components formed during oscillation often appear in the grid voltage spectrum in the form of interharmonics.

[0047] As an optional embodiment, an oscillation suppression mechanism is triggered based on a determined oscillation frequency, and oscillation suppression control is performed on the doubly-fed wind turbine based on the oscillation frequency, including: sending the oscillation frequency to the controller of the turbine-side converter and / or grid-side converter in the doubly-fed wind turbine, so that the controller executes the oscillation suppression mechanism based on the oscillation frequency.

[0048] In this embodiment, triggering the oscillation suppression mechanism based on the determined oscillation frequency is a process that uses the oscillation frequency as the control triggering basis. Once the oscillation frequency is determined, this embodiment processes it as a specific frequency parameter, rather than simply as a result of determining whether oscillation exists. By establishing a correlation between the oscillation frequency and the control flow within the doubly-fed induction generator (DFIG), the oscillation suppression mechanism can operate around the specific oscillation characteristics currently detected, rather than controlling a fixed or preset frequency range.

[0049] In this specific embodiment, the oscillation frequency is transmitted to the controllers of the turbine-side converter and / or grid-side converter in the doubly-fed induction generator (DFIG) wind turbine. The transmission process can be implemented, but is not limited to, through the unit's internal communication bus, control signal interface, or shared storage unit, enabling the controller to receive the oscillation frequency parameters in real time. The turbine-side converter and grid-side converter can receive the oscillation frequency individually or simultaneously, depending on the current control structure of the unit.

[0050] Furthermore, in this embodiment, after receiving the oscillation frequency, the controller executes an oscillation suppression mechanism based on the oscillation frequency. This execution process adjusts the controller's internal control logic based on the oscillation frequency, ensuring that the control action corresponds to the current oscillation frequency. In this way, this embodiment achieves a direct correlation between oscillation suppression control and the actual oscillation frequency of the grid voltage, enabling the oscillation suppression mechanism to be updated synchronously with changes in the oscillation frequency.

[0051] like Figure 4 As shown, I dq For the d-axis and q-axis components of the stator current of a doubly-fed induction generator, V dqref For the d-axis and q-axis component command values ​​of the control signal used to control the machine-side converter, I dqref PQ represents the d-axis and q-axis command values ​​of the stator current of the doubly-fed induction generator (DFIG) input to the inner current loop, and PQ represents the active and reactive power output of the wind turbine. ref These are the active power command values ​​and reactive power command values ​​for the wind turbine generator set.

[0052] As an optional embodiment, when the oscillation frequency is sent to the turbine-side converter in the doubly-fed wind turbine, the controller executes an oscillation suppression mechanism based on the oscillation frequency, including: acquiring the rotor current of the doubly-fed wind turbine; performing coordinate transformation on the rotor current to obtain the dq current; inputting the dq current into the resonant controller to obtain the resonant regulation voltage; and superimposing the resonant regulation voltage with the voltage signal output from the inner current loop of the turbine-side converter to generate a control signal for controlling the turbine-side converter.

[0053] In this embodiment, when the oscillation frequency is sent to the turbine-side converter in the doubly-fed induction generator (DFIG) wind turbine, the controller enters an oscillation suppression control process based on this frequency. This process uses directly obtainable electrical quantities from within the turbine as the control object. In this embodiment, the rotor current of the DFIG wind turbine is selected as the input signal to characterize the electromagnetic state on the rotor side. The rotor current changes with grid voltage disturbances, and its changing characteristics contain information corresponding to the oscillation frequency. Therefore, by acquiring the rotor current, the dynamic response of the turbine under oscillation conditions can be reflected.

[0054] In this embodiment, the coordinate transformation of the rotor current to obtain the dq current is a process of converting the AC rotor current into an equivalent DC current in a rotating coordinate system. This coordinate transformation can be implemented, but is not limited to, using a synchronous rotating coordinate system, so that the components of the rotor current in the quadrature and direct axes correspond to different electromagnetic adjustment channels. In this way, the oscillating components originally superimposed on the AC signal are mapped into the dq current, facilitating subsequent processing of specific frequency components.

[0055] In this embodiment, the dq current is input to the resonant controller. This utilizes the resonant controller's selective response to specific frequency signals to adjust the current component corresponding to the oscillation frequency. The resonant controller uses the oscillation frequency as its operating basis, adjusting the corresponding frequency component in the dq current and outputting a resonant adjustment voltage. This resonant adjustment voltage reflects the control correction amount for the current oscillation frequency, and its magnitude and phase are determined by the internal structure of the resonant controller.

[0056] In this embodiment, the resonant regulation voltage is superimposed with the voltage signal output from the inner current loop of the machine-side converter to generate a control signal for controlling the machine-side converter. This introduces a compensation amount for the oscillation frequency on the basis of the original current control. This superposition method can be expressed as direct addition or combined according to a preset ratio, enabling the machine-side converter to respond to the current component corresponding to the oscillation frequency while maintaining its original current regulation function. In this way, the generated control signal can simultaneously reflect the normal operation requirements and oscillation suppression requirements, and is used for subsequent control execution of the machine-side converter.

[0057] like Figure 3 As shown, as an optional embodiment, after generating the control signal for controlling the machine-side converter, the method further includes: performing coordinate inverse transformation and pulse width modulation on the control signal to generate a switching control signal, and using the switching control signal to control the switching devices in the machine-side converter.

[0058] In this embodiment, after generating the control signal for controlling the generator-side converter, performing an inverse coordinate transformation on the control signal is a process of converting the control signal formed in the dq coordinate system back into a three-phase stationary coordinate system signal suitable for the converter's execution. This inverse coordinate transformation can, but is not limited to, employing an inverse transformation method corresponding to the aforementioned coordinate transformation, to restore the control signal to a voltage command form that matches the generator-side converter's power circuit.

[0059] The control signal, after inverse coordinate transformation, undergoes further pulse width modulation (PWM) processing to generate corresponding switching control signals. These switching control signals directly control the on / off states of various switching devices in the generator-side converter, enabling the converter to operate according to the control signal's instructions. In this way, the controller's output control signal is transformed into specific switching actions, achieving actual control of the generator-side converter's operating state.

[0060] As an optional embodiment, the transfer function of the resonant controller is: Among them, G R (s) is the transfer function of the resonant controller, K r ω is the gain coefficient of the resonant controller. i ω is the center frequency of the resonant controller. r The bandwidth of the resonant controller is affected by s, where s is the Laplace operator; K r ω i ω r It is related to the oscillation frequency.

[0061] In this embodiment, the resonant controller employs a transfer function, which responds to the component of the input signal corresponding to the oscillation frequency by exhibiting a distinct frequency selectivity around a specific frequency. The center frequency ω in the transfer function... i Used to determine the frequency position of interest for the resonant controller, when ω i When the oscillation frequency is detected, the resonant controller has a significant effect on that frequency component, while its influence on other frequency components is relatively small. This structure allows the resonant controller to adjust for the oscillation-related frequency components in the current signal.

[0062] Gain coefficient K r The resonant controller is used to adjust the intensity of its effect on the oscillation frequency component; its value determines the amplitude level of the resonant regulating voltage. The parameter ω affects the bandwidth. r Used to define the response range of the resonant controller to frequency components near the center frequency, ω r Different values ​​of K correspond to different operating ranges of the resonant controller in the frequency domain. By analyzing K... r ω i and ω rBy making settings, a balance can be struck between frequency selectivity and control strength.

[0063] Furthermore, in this embodiment, K r ω i and ω r The system adjusts in real time based on the oscillation frequency. When the monitored oscillation frequency changes, the center frequency and related parameters of the resonant controller are updated accordingly, ensuring that the resonant controller always corresponds to the current oscillation state. This parameter adjustment process is based on changes in the oscillation frequency, enabling the resonant controller to function effectively for the corresponding oscillation frequency under different operating conditions.

[0064] like Figure 3 As shown, Figure 3 The voltage transformer in the system is used to convert the voltage from the stator voltage or the voltage output by the grid-side converter via LC to obtain a smaller, easier-to-measure voltage, and then measure it. Figure 3 The current transformer in the middle is used to obtain a small, easily measurable current and to measure it. The pulse width modulation switch control signal is the switch control signal described in the above embodiment for controlling the machine-side converter and / or the grid-side converter. Two filters are used to filter the signal output from the wind turbine and the signal output from the grid-side converter, respectively. This embodiment describes a specific implementation where the online oscillation suppression device of the doubly-fed wind turbine is used to obtain the output voltage of the grid-side converter, and a third-party detection device is used to obtain the voltage on the stator side of the doubly-fed wind turbine. However, in practice, the online oscillation suppression device of the doubly-fed wind turbine can also be used to obtain the output voltage of the grid-side converter and / or the voltage on the stator side of the doubly-fed wind turbine; this application is not limited to this.

[0065] As an optional embodiment, acquiring a monitoring voltage for characterizing the grid voltage includes: acquiring the stator-side voltage of the doubly-fed wind turbine, and / or acquiring the output voltage of the grid-side converter; the monitoring voltage includes the stator-side voltage and / or the output voltage.

[0066] In this embodiment, the monitoring voltage used to characterize the grid voltage can be obtained by acquiring the stator-side voltage of the doubly-fed induction generator (DFIG) and / or the output voltage of the grid-side converter. The stator-side voltage directly reflects the electromagnetic coupling state between the DFIG and the grid, and can characterize the voltage changes near the grid connection point; the output voltage of the grid-side converter reflects the voltage characteristics when the generator injects electrical energy into the grid via the converter. In this embodiment, the monitoring voltage may include only the stator-side voltage, only the output voltage, or both of the above voltage signals.

[0067] When the monitored voltage includes both the stator-side voltage and the grid-side converter output voltage, the two voltage signals can be compared to determine if an error exists. This comparison can be based on voltage amplitude, phase, or trend to reflect the voltage consistency between the stator side and the converter output at the same operating moment. In specific implementation, this embodiment can align the stator-side voltage and the grid-side converter output voltage under the same time reference and then compare them. When the difference between the two exceeds a preset range, an error is considered to exist. This error can reflect the differences in the performance of changes in the unit's internal electrical state or grid-side disturbances at different measuring points, providing reference information for subsequent processing based on the monitored voltage.

[0068] In this embodiment, the grid-side common bus voltage or remote grid voltage was not directly selected as the monitoring object because such voltages are usually outside the direct acquisition range of the unit's control system. The acquisition process relies on additional communication or measurement devices, which can lead to sampling delays, inconsistencies, or limited availability. In contrast, the stator-side voltage and the grid-side converter output voltage are electrical quantities that can be directly measured during the operation of the doubly-fed induction generator (DFIG). Their acquisition paths are short, their signal sources are clear, and they can continuously reflect the voltage changes during grid-connected operation.

[0069] Furthermore, in this embodiment, both the stator-side voltage and the grid-side converter output voltage are electrically related to the grid voltage, and their changing trends can reflect the dynamic characteristics of the grid-side voltage. By selecting the above voltages as monitoring voltages, this embodiment achieves the characterization of the grid voltage state without introducing additional external measurement conditions.

[0070] As an optional embodiment, frequency domain analysis is performed on the monitored voltage to obtain the frequency domain analysis results of the grid voltage, including: performing fast Fourier transform analysis on the monitored voltage to obtain the frequency domain analysis spectrum of the grid voltage; obtaining the total harmonic content of the grid voltage based on the frequency domain analysis spectrum of the grid voltage; and determining whether the doubly-fed induction generator (DFIG) oscillates, including: comparing the total harmonic content with a preset threshold, and determining that the DFIG oscillates when the total harmonic content is greater than the preset threshold.

[0071] In this embodiment, the frequency domain analysis spectrum of the grid voltage is used to reflect the amplitude distribution of the monitored voltage at different frequency positions, so that the fundamental component and various non-fundamental frequency components contained in the grid voltage can be expanded in the frequency domain. In this embodiment, the fast Fourier transform can be performed within a continuous or segmented time window to obtain the frequency domain analysis spectrum corresponding to different times.

[0072] The total harmonic content of the grid voltage, obtained from the frequency domain analysis spectrum, is calculated by summarizing the non-fundamental frequency components in the spectrum. This total harmonic content characterizes the proportion of harmonic components in the overall voltage. Its calculation method can be, but is not limited to, weighted summation or normalization of the amplitudes of each harmonic. Through this total harmonic content, harmonic information dispersed at different frequency locations can be converted into a single quantitative indicator.

[0073] Comparing the total harmonic content with a preset threshold is the basis for judging the current operating status of the power grid voltage. The preset threshold can be set based on the operating experience of doubly-fed induction generator (DFIG) wind turbines or grid connection standards, and is used to distinguish between normal and abnormal operating states. When the total harmonic content is less than or equal to the preset threshold, the power grid voltage is considered to be within an acceptable range; when the total harmonic content exceeds the preset threshold, abnormal frequency components are considered to exist in the power grid voltage.

[0074] Furthermore, when the total harmonic content exceeds a preset threshold, the doubly-fed induction generator (DFIG) is determined to be oscillating. This determination process is directly based on the frequency domain analysis results of the monitored voltage, without relying on a priori settings for the oscillation frequency, enabling the oscillation judgment process to be automatically updated as the grid operating status changes.

[0075] To address the aforementioned technical problems, the present invention also provides an online oscillation suppression device for a doubly-fed wind turbine, comprising: a memory for storing a computer program; and a processor for implementing the steps of the online oscillation suppression method for a doubly-fed wind turbine as described above when executing the computer program.

[0076] For an introduction to the online oscillation suppression device for doubly-fed wind turbines, please refer to the embodiments of the online oscillation suppression method for doubly-fed wind turbines described above; further details will not be repeated here.

[0077] To address the aforementioned technical problems, the present invention provides a doubly fed wind turbine generator set, including the online oscillation suppression device for the doubly fed wind turbine generator set as described above.

[0078] For an introduction to doubly-fed induction generator (DFIG) wind turbines, please refer to the embodiments of the online oscillation suppression method for DFIG wind turbines described above; this application will not repeat the details here.

[0079] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0080] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An online oscillation suppression method for a doubly-fed wind turbine generator, characterized in that, include: Obtain the monitoring voltage used to characterize the grid voltage; Frequency domain analysis was performed on the monitored voltage to obtain the frequency domain analysis results of the grid voltage; Based on the frequency domain analysis results, determine the interharmonic content in the grid voltage and determine whether the doubly fed wind turbine unit oscillates; Determining the interharmonic content in the grid voltage based on the frequency domain analysis results includes: statistically processing each frequency component in the frequency domain analysis results, extracting frequency components that are inconsistent with the fundamental frequency, and using the amplitude information of the frequency components that are inconsistent with the fundamental frequency as the interharmonic content. The interharmonic content reflects the existence of abnormal frequency components in the grid voltage. When oscillation is detected, an oscillation suppression mechanism is triggered to suppress oscillation in the doubly fed wind turbine.

2. The online oscillation suppression method for a doubly-fed wind turbine as described in claim 1, characterized in that, Frequency domain analysis of the monitored voltage is performed to obtain the frequency domain analysis results of the grid voltage, including: The monitored voltage was analyzed by Fast Fourier Transform to obtain the frequency domain analysis spectrum of the power grid voltage; The interharmonic voltages in the grid voltage are determined based on the frequency domain analysis spectrum of the grid voltage; when oscillation is determined to occur, the online oscillation suppression method of the doubly-fed wind turbine further includes: The amplitudes of all the interharmonic voltages are sorted, and the frequencies corresponding to the interharmonic voltages with the largest amplitudes are determined as the oscillation frequencies of the doubly fed wind turbine. Triggering an oscillation suppression mechanism to perform oscillation suppression control on the doubly-fed wind turbine generator, including: The oscillation suppression mechanism is triggered according to the determined oscillation frequency, and the doubly fed wind turbine is subjected to oscillation suppression control according to the oscillation frequency.

3. The online oscillation suppression method for doubly-fed wind turbines as described in claim 2, characterized in that, The oscillation suppression mechanism is triggered according to the determined oscillation frequency, and oscillation suppression control is performed on the doubly-fed wind turbine according to the oscillation frequency, including: The oscillation frequency is sent to the controller of the generator-side converter and / or grid-side converter in the doubly fed wind turbine, so that the controller executes the oscillation suppression mechanism according to the oscillation frequency.

4. The online oscillation suppression method for doubly-fed wind turbines as described in claim 3, characterized in that, When the oscillation frequency is sent to the turbine-side converter in the doubly-fed wind turbine, the controller executes the oscillation suppression mechanism according to the oscillation frequency, including: Obtain the rotor current of a doubly-fed wind turbine; The rotor current is transformed by coordinates to obtain the dq current; The dq current is input into the resonant controller to obtain the resonant adjustment voltage; The resonant regulation voltage is superimposed with the voltage signal output from the inner current loop of the machine-side converter to generate a control signal for controlling the machine-side converter.

5. The online oscillation suppression method for a doubly-fed wind turbine as described in claim 4, characterized in that, After generating the control signal for controlling the machine-side converter, the process further includes: The control signal is subjected to inverse coordinate transformation and pulse width modulation to generate a switching control signal, and the switching control signal is used to control the switching devices in the machine-side converter.

6. The online oscillation suppression method for a doubly-fed wind turbine as described in claim 4, characterized in that, The transfer function of the resonant controller is: ； Among them, G R (s) is the transfer function of the resonant controller, K r ω is the gain coefficient of the resonant controller. i ω is the center frequency of the resonant controller. r To influence the bandwidth of the resonant controller, s is the Laplace operator; K r ω i ω r It is related to the oscillation frequency.

7. The online oscillation suppression method for a doubly-fed wind turbine as described in claim 1, characterized in that, Acquire the monitoring voltage used to characterize the grid voltage, including: Obtain the stator-side voltage of the doubly-fed wind turbine generator, and / or obtain the output voltage of the grid-side converter; The monitored voltage includes the stator-side voltage and / or the output voltage.

8. The online oscillation suppression method for a doubly-fed wind turbine as described in claim 1, characterized in that, Frequency domain analysis of the monitored voltage is performed to obtain the frequency domain analysis results of the grid voltage, including: The monitored voltage was analyzed by Fast Fourier Transform to obtain the frequency domain analysis spectrum of the power grid voltage; The total harmonic content of the grid voltage is obtained from the frequency domain analysis spectrum of the grid voltage. Determining whether the doubly-fed wind turbine unit is oscillating includes: The total harmonic content is compared with a preset threshold. When the total harmonic content is greater than the preset threshold, it is determined that the doubly fed wind turbine is oscillating.

9. An online oscillation suppression device for a doubly-fed wind turbine generator, characterized in that, include: Memory, used to store computer programs; A processor, configured to, when executing a computer program, implement the steps of the online oscillation suppression method for a doubly-fed wind turbine as described in any one of claims 1-8.

10. A doubly-fed wind turbine generator, characterized in that, Includes the online oscillation suppression device for doubly fed wind turbines as described in claim 9.

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