Subsynchronous oscillation suppression device for doubly-fed fan

Abstract

The utility model provides a subsynchronous oscillation suppression device used for a doubly-fed fan, a machine side converter and a grid side converter of the doubly-fed fan both adopt a VSG control strategy, the doubly-fed fan comprises an active power error path and a reactive power error path, and the subsynchronous oscillation suppression device comprises a self-adaptive wave trap, a voltage stabilizing circuit, a voltage stabilizing circuit and a voltage stabilizing circuit, the adaptive wave trap is arranged in the active power error path and the reactive power error path; and the subsynchronous information estimator is installed at a grid connection point of the double-fed fan, and the subsynchronous information estimator is used for estimating the subsynchronous oscillation frequency. According to the utility model, the technical problem of grid-connected broadband oscillation of the doubly-fed fan in which both the machine-side converter and the grid-side converter adopt a VSG control strategy is solved.

Description

Technical Field

[0001] This utility model relates to the field of power system technology, and more specifically, to a subsynchronous oscillation suppression device for doubly fed wind turbines. Background Technology

[0002] With the implementation of my country's "dual-carbon" policy, a large number of new energy power generation devices have been connected to the power grid. Due to the differences in the geographical distribution of China's natural resources and the uneven economic development between regions, new energy power generation often requires long-distance transmission. In actual engineering, series compensation capacitors are used in transmission lines to compensate for reactance, improve system voltage, and reduce power loss. However, series compensation transmission lines and new energy power generation stations often experience interactive oscillations, causing power grid faults.

[0003] Both the turbine-side and grid-side converters adopt the dual virtual synchronous machine control structure of the grid-type doubly fed wind turbine, which can provide inertia and frequency support when wind power is connected to the grid, and avoid the impact of phase-locked loop on the grid-connected stability of the system. This solves the problems of low system inertia and negative resistance effect caused by phase-locked loop controller.

[0004] However, in actual implementation, there is a problem: doubly fed wind turbines that use VSG control strategies in both the turbine-side and grid-side converters have a wideband oscillation problem when connected to the grid. Utility Model Content

[0005] This invention solves the technical problem of wideband oscillations during grid connection in doubly-fed wind turbines where both the turbine-side and grid-side converters employ VSG control strategies.

[0006] To address the aforementioned problems, this utility model provides a subsynchronous oscillation suppression device for a doubly-fed induction generator (DFIG). Both the turbine-side converter and the grid-side converter of the DFIG employ a VSG control strategy. The DFIG includes an active power error path and a reactive power error path. The subsynchronous oscillation suppression device includes: an adaptive notch filter, which is located in both the active power error path and the reactive power error path; and a subsynchronous information estimator, which is installed at the grid connection point of the DFIG and is used to estimate the subsynchronous oscillation frequency.

[0007] Compared with existing technologies, the technical effects achieved by this solution are as follows: both the turbine-side converter and the grid-side converter employ VSG control strategies, which can provide inertia and frequency support for the system and avoid the impact of phase-locked loops on the grid-connected stability. However, the use of this new structure urgently requires solving the problem of wideband oscillation during grid connection. To address this issue, this application designs a subsynchronous oscillation suppression device for doubly-fed induction generator (DFIG) wind turbines. By automatically identifying and locking oscillation information and adaptively adjusting algorithm parameters, subsynchronous oscillations are suppressed. An adaptive notch filter can effectively filter out the subsynchronous components of active and reactive power, thereby blocking the circulation of subsynchronous components. The subsynchronous signal estimator detects unstable subsynchronous modes and accurately estimates the subsynchronous oscillation frequency. This application can suppress wideband oscillations during grid connection of dual-VSG controlled DFIG wind turbines, and its suppression effect is unaffected by wind farm operating conditions and time-varying oscillation frequencies.

[0008] In one embodiment of this utility model, the subsynchronous oscillation suppression device further includes: an input module, which extracts a signal with a significant subsynchronous component when subsynchronous oscillation occurs as an input signal; an oscillation information module, which obtains oscillation information in the input signal based on a compaction technique approximate projection subspace tracking algorithm; an oscillation information screening module, which extracts subsynchronous oscillation information from the oscillation information; an identification module, which determines the oscillation status of the system based on the subsynchronous oscillation information; and an adjustment module, which sets the enable signal and center frequency of the adaptive notch filter trigger based on the oscillation status.

[0009] In one embodiment of this invention, the oscillation information includes the frequency and attenuation coefficient of the sinusoidal component in the input signal.

[0010] In one embodiment of this utility model, when the attenuation coefficient is greater than 0, it is determined that the subsynchronous oscillation suppression device is experiencing divergent subsynchronous oscillation; when the attenuation coefficient is less than 0, it is determined that the subsynchronous oscillation suppression device has sufficient damping at the corresponding frequency.

[0011] Compared with existing technologies, the technical effects achieved by this solution are as follows: the magnitude of the attenuation coefficient can directly determine the subsynchronous oscillation of the system; an attenuation coefficient greater than 0 indicates that the system is diverging at a frequency of... The oscillation; a damping coefficient less than 0 indicates that the system has sufficient damping when oscillating at the corresponding frequency.

[0012] In one embodiment of this utility model, the subsynchronous oscillation information includes: the subsynchronous oscillation frequency.

[0013] In one embodiment of this utility model, the machine-side converter collects the first voltage and first current at the asynchronous motor port, and the first output active power and first reactive power of the computer-side part; the first output active power and first reactive power are used as the first control signal of the machine-side converter; the reference angle of the PWM modulation part at the grid-side converter end is obtained by calculating the reference angle and the rotation angle difference between the stator and rotor according to the VSG control strategy.

[0014] In one embodiment of this utility model, the grid-side converter collects the second voltage and the second current at the asynchronous motor port to calculate the second output active power and the second reactive power of the grid-side portion; the second output active power and the second reactive power are used as the second control signal of the grid-side converter.

[0015] By adopting the technical solution of this utility model, the following technical effects can be achieved:

[0016] (1) This application can suppress the wideband oscillation of the grid-connected doubly fed wind turbine with dual VSG control, and its suppression effect is not affected by the wind farm operating conditions and time-varying oscillation frequency.

[0017] (2) The frequency and attenuation coefficient information in the subsynchronous oscillation signal of the system are obtained online by using the compaction technique approximate projection subspace tracking algorithm. When the obtained attenuation coefficient reaches the preset threshold, the adaptive notch filter is triggered and put into the control loop of the doubly fed wind turbine rotor side converter. The parameters of the adaptive notch filter are adaptively adjusted according to the obtained frequency to block the propagation of the subsynchronous oscillation component and achieve the purpose of suppressing the subsynchronous oscillation.

[0018] (3) Based on the online operation data of the system, the real-time oscillation information of the system is extracted. It does not rely on the accurate mathematical model of the system, requires a small amount of data, has good real-time performance, and has strong robustness and adaptability.

[0019] (4) Setting an adaptive notch filter can effectively filter out the subsynchronous components of active and reactive power, thereby blocking the circulation of subsynchronous components;

[0020] (5) The function of the subsynchronous signal estimator is to detect unstable subsynchronous modes and accurately estimate the subsynchronous oscillation frequency. Attached Figure Description

[0021] Figure 1 A grid-connected system structure diagram of a doubly fed wind turbine provided in Embodiment 1 of this utility model;

[0022] Figure 2 In order to be in Figure 1 A schematic diagram of adding an adaptive notch filter to the reactive power error path in the image;

[0023] Figure 3 In order to be inFigure 1 A schematic diagram of adding an adaptive notch filter to the active power error path in the image;

[0024] Figure 4 for Figure 1 Block diagram of the adaptive notch filter principle. Detailed Implementation

[0025] To make the above-mentioned objectives, features, and advantages of this utility model more apparent and understandable, the technical solutions in the embodiments of this utility model are clearly and completely described. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0026] Example 1

[0027] See Figure 1 This utility model provides a subsynchronous oscillation suppression device for doubly-fed wind turbines, combined with Figures 2-4 Both the machine-side converter and the grid-side converter of the doubly-fed induction generator (DFIG) adopt the VSG control strategy. The DFIG includes an active power error path and a reactive power error path. The subsynchronous oscillation suppression device includes an adaptive notch filter and a subsynchronous information estimator. The adaptive notch filter is located in the active power error path and the reactive power error path. The subsynchronous information estimator is installed at the grid connection point of the DFIG and is used to estimate the subsynchronous oscillation frequency.

[0028] In one specific embodiment, the adaptive notch filter blocks subsynchronous oscillations by filtering out the circulation of subsynchronous current in the doubly-fed induction generator (DFIG) control loop. When subsynchronous oscillations occur in the system, the subsynchronous component in the turbine-side loop is introduced by the active and reactive power outputs of the turbine. Therefore, the adaptive notch filter is installed in the active power error path and reactive power error path of the VSG control on both the turbine side and the grid side. Figure 2 This is a schematic diagram of adding an adaptive notch filter to the reactive power error path. Figure 3 This is a schematic diagram of adding an adaptive notch filter to the active power error path. The adaptive notch filter effectively filters out the subsynchronous components of both active and reactive power, thereby blocking the cycling of subsynchronous components. The subsynchronous signal estimator detects unstable subsynchronous modes and accurately estimates the subsynchronous oscillation frequency. It is installed at the grid connection point of the doubly-fed induction generator (DFIG). This application uses the output current of the DFIG as the input signal to the subsynchronous signal estimator, and represents it as a superposition of several sinusoidal signals with attenuation coefficients and noise.

[0029] Furthermore, the subsynchronous oscillation suppression device also includes: an input module, an oscillation information module, an oscillation information screening module, an identification module, and an adjustment module. The input module is used to extract the signal with a significant subsynchronous component when subsynchronous oscillation occurs as the input signal; the oscillation information module obtains the oscillation information in the input signal based on the compaction technique approximate projection subspace tracking algorithm; the oscillation information screening module is used to extract the subsynchronous oscillation information from the oscillation information; the identification module determines the oscillation status of the system based on the subsynchronous oscillation information; and the adjustment module sets the enable signal and its center frequency for the adaptive notch filter trigger based on the oscillation status.

[0030] Oscillation information includes the frequency and attenuation coefficient of the sinusoidal component in the input signal.

[0031] When the attenuation coefficient is greater than 0, it is determined that the subsynchronous oscillation suppression device is experiencing divergent subsynchronous oscillation; when the attenuation coefficient is less than 0, it is determined that the subsynchronous oscillation suppression device has sufficient damping at the corresponding frequency.

[0032] The subsynchronous oscillation information includes: the subsynchronous oscillation frequency.

[0033] Specifically, the output current of the doubly-fed induction generator (DFIG) is used as the input signal of the subsynchronous signal estimator, and is represented as a superposition of several sinusoidal signals with attenuation coefficients and noise, i.e.: In the formula, k = 1, 2, ..., r; r is the number of complex sinusoidal components in the sampled signal; The sampling period; , , , These are the amplitude, initial phase, attenuation coefficient, and frequency of the k-th sinusoidal component, respectively. It is white noise.

[0034] The sampled data vector x(t) at time t is represented as: In the formula, This is the matrix transpose; m is the window length, preferably set to 100; the sampling frequency is set to 1000Hz, and the vector data is updated every 0.1s.

[0035] The oscillation information estimator for subsynchronous signals uses a compaction technique to approximate the projected subspace tracking algorithm, monitoring unstable subsynchronous modes and accurately estimating the subsynchronous oscillation frequency. The unconstrained cost function is defined as follows:

[0036] ,

[0037] ;

[0038] In the formula: W(t) is an m×r parameter matrix introduced to construct the objective function; x(t) is the current vector output at time t. is the forgetting factor, and c(t) is the parameter matrix introduced to construct the objective function.

[0039] When the cost function reaches its global minimum, the frequency and attenuation coefficient of the sinusoidal component in the signal can be estimated and input into the adaptive adjustment algorithm. The specific process is as follows:

[0040] W(t) approximates the eigenvectors of the signal subspace S in c(t), thereby estimating the correlated oscillation information in the signal. W(t) is solved iteratively using the recursive least squares method. The submatrix can be obtained by deleting the first and last rows of matrix W(t). and ,Right now

[0041] ;

[0042] Therefore, the signal subspace S is represented as: In the formula It is a pseudo-inverse matrix.

[0043] By calculating the eigenvalues ​​of the signal subspace S (k=1,2,……r) can be used to estimate the frequency and attenuation coefficient of the sinusoidal component in the signal:

[0044] frequency: ,

[0045] Attenuation coefficient: ;

[0046] Attenuation coefficient The magnitude of the oscillation can be used to intuitively determine the subsynchronous oscillation of the system: A value greater than 0 indicates that the system is diverging, with a frequency of The oscillation; A value less than 0 indicates that the system has sufficient damping during oscillation at the corresponding frequency. To avoid unnecessary malfunctions, the frequency needs to be extracted from the acquired oscillation signal. The subsynchronous oscillation signal has a range of 4-46Hz.

[0047] When determining the attenuation coefficient When the value is greater than 0, the center oscillation frequency is calculated. Based on the calculated center oscillation frequency, the adaptive notch filter adaptively adjusts its own coefficient, so that the characteristics of the filter can change with the harmonics and noise. After adjustment, the adaptive notch filter is put into the system to filter out the oscillation signal. Let be the signal to be filtered at time t. The signal after filtering at time t. The center frequency of the notch filter is determined by... Generate sine and cosine signals with the same frequency, and then use weighting coefficients. and Linear combination generates weighted signals The frequency of the weighted signal is The amplitude and phase are controlled by weighting coefficients. The key to this adaptive notch filter is updating these weighting coefficients using an adaptive algorithm and recursive least squares method. The adaptive algorithm adjusts the amplitude and phase weighting coefficients in real time, filtering out the corresponding subsynchronous oscillation components and continuously bringing the frequency of the filtered signal closer to the fundamental frequency.

[0048] After detecting system oscillation, the center frequency of the adaptive notch filter is set: In the formula, This is the system's base frequency.

[0049] The principle block diagram of the adaptive notch filter is shown in Figure 4. It adjusts its own coefficients through an adaptive algorithm to achieve the optimal filtering effect. The specific control algorithm is as follows: In the formula, the subscript t corresponds to time t, and k represents the iteration relationship. This is the formula for updating the weight vector of the adaptive notch filter.

[0050] The prior estimation error is: ;

[0051] The gain vector is: ;

[0052] The inverse correlation matrix is: ;

[0053] The forgetting factor is set to 0.998, which represents the stickiness of information from previous iterations.

[0054] Furthermore, the machine-side converter collects the first voltage and first current at the asynchronous motor port, and the first output active power and first reactive power of the computer-side part; the first output active power and first reactive power are used as the first control signal of the machine-side converter; the reference angle of the PWM modulation part at the grid-side converter end is obtained by calculating the reference angle and the rotation angle difference between the stator and rotor according to the VSG control strategy.

[0055] Furthermore, the grid-side converter collects the second voltage and second current at the asynchronous motor port to calculate the second output active power and second reactive power of the grid-side portion; the second output active power and second reactive power are used as the second control signal of the grid-side converter.

[0056] Specifically, the machine-side converter collects the first voltage and first current at the asynchronous motor port, and the first output active power and first reactive power of the computer-side section are used as the first control signal. The reference angle of the PWM modulation section is the VSG control strategy calculation reference angle. Subtract the rotation angle difference between the stator and rotor The grid-side converter collects the second output active and second reactive power from the grid side as the VSG control signal (i.e., the second control signal) to modulate the converter drive signal.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A subsynchronous oscillation suppression device for a doubly-fed wind turbine, characterized in that, Both the machine-side converter and the grid-side converter of the doubly-fed induction generator (DFIG) adopt the VSG control strategy. The DFIG includes an active power error path and a reactive power error path. The subsynchronous oscillation suppression device includes: An adaptive notch filter is disposed in the active power error path and the reactive power error path; A subsynchronous information estimator is installed at the grid connection point of the doubly fed wind turbine, and the subsynchronous information estimator is used to estimate the subsynchronous oscillation frequency.

2. The subsynchronous oscillation suppression device according to claim 1, characterized in that, The subsynchronous oscillation suppression device further includes: The input module is used to extract the signal with a significant subsynchronous component when subsynchronous oscillation occurs as the input signal; An oscillation information module, which acquires oscillation information in the input signal based on a compaction technique approximate projection subspace tracking algorithm; An oscillation information screening module is used to extract subsynchronous oscillation information from the oscillation information; The identification module determines the oscillation status of the system based on the subsynchronous oscillation information. An adjustment module is provided, which sets the enable signal and center frequency of the adaptive notch filter trigger based on the oscillation condition.

3. The subsynchronous oscillation suppression device according to claim 2, characterized in that, The oscillation information includes the frequency and attenuation coefficient of the sinusoidal component in the input signal.

4. The subsynchronous oscillation suppression device according to claim 3, characterized in that, When the attenuation coefficient is greater than 0, it is determined that the subsynchronous oscillation suppression device is experiencing divergent subsynchronous oscillation. When the attenuation coefficient is less than 0, it is determined that the subsynchronous oscillation suppression device has sufficient damping at the corresponding frequency.

5. The subsynchronous oscillation suppression device according to claim 2, characterized in that, The subsynchronous oscillation information includes: the subsynchronous oscillation frequency.

6. The subsynchronous oscillation suppression device according to claim 2, characterized in that, The machine-side converter collects the first voltage and first current at the asynchronous motor port, and outputs the first active power and first reactive power on the computer side. The first output active power and the first reactive power are used as the first control signal of the machine-side converter; The reference angle of the PWM modulation section at the grid-side converter is obtained by calculating the reference angle and the rotation angle difference between the stator and rotor based on the VSG control strategy.

7. The subsynchronous oscillation suppression device according to claim 2, characterized in that, The grid-side converter collects the second voltage and the second current at the asynchronous motor port to calculate the second output active power and the second reactive power of the grid-side portion. The second output active power and the second reactive power are used as the second control signals of the grid-side converter.

Images