Wind power plant broadband oscillation suppression method and system based on amplitude-phase characteristic remodeling

Abstract

The invention discloses a wind power plant broadband oscillation suppression method and system based on amplitude-phase characteristic remodeling. The method comprises the following steps: respectively establishing a frequency domain impedance model of each wind turbine generator set and performing dynamic order reduction, analyzing amplitude-frequency and phase-frequency characteristics of wind power plant multi-machine parallel coupling based on the order reduction model, determining an interaction rule of a module value and a phase angle, designing additional damping control and active damping control, and determining a wind power plant multi-machine parallel coupling amplitude-frequency and phase-frequency characteristic of the wind power plant multi-machine parallel coupling amplitude-frequency and phase-frequency characteristic. A weak position of a system is positioned based on an s-domain node admittance matrix method, a function is set by taking improvement of amplitude-phase characteristics as a target and optimizing and setting control parameters for a target wind turbine generator corresponding to the position, the optimized parameters are applied to the target generator, and effective suppression of broadband oscillation is realized. According to the application, the broadband oscillation problem caused by high-proportion new energy grid connection can be systematically solved by synergistically remodeling the frequency domain amplitude-phase characteristics of the wind power plant.

Description

Technical Field

[0001] This application relates to the field of grid-connected stability control of new energy sources, and more specifically, to a method and system for suppressing broadband oscillations in wind farms based on amplitude and phase characteristic reshaping. Background Technology

[0002] With the increasing severity of global energy issues, the development and utilization of renewable energy have gained attention from various countries. China aims to achieve a transition to clean energy in its energy structure. Guided by dual carbon targets, accelerating the low-carbon transformation of the power system is key to achieving low-carbon development. At the same time, technologies for large-scale grid connection of high-proportion renewable energy are developing rapidly. Wind farms, as a major source of renewable energy, play an indispensable role. However, with large-scale wind power being connected to the grid via converters, the problem of broadband grid oscillations has become prominent.

[0003] Wind turbines interact in complex ways within renewable energy power plants. The amplitude and phase characteristics of a wind farm are no longer simply the algebraic superposition of the impedance characteristics of a single turbine, but rather the result of the amplitude and phase frequency characteristics of multiple wind turbines coupling together over a wide frequency band. However, each wind turbine is generally controlled independently, lacking coordination. Optimizing the control structures to achieve optimal amplitude and phase characteristics, reshaping the overall impedance characteristics of the power plant, and effectively suppressing broadband oscillations are critical issues that urgently need to be addressed.

[0004] Therefore, this application provides a method and system for suppressing broadband oscillations in wind farms based on amplitude and phase characteristic reshaping, in order to solve one of the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this application is to provide a method and system for suppressing broadband oscillations in wind farms based on amplitude and phase characteristic reshaping, which can solve at least one of the aforementioned technical problems. The specific solution is as follows: According to a specific embodiment of this application, in a first aspect, this application provides a method for suppressing broadband oscillations in wind farms based on amplitude and phase characteristic reshaping, comprising: The control structure parameters and steady-state operation data of each wind turbine in the wind farm are obtained. Based on the frequency domain small-signal interference method, a frequency domain impedance model of each wind turbine is established, and the frequency domain impedance model is dynamically reduced to obtain a simplified frequency domain impedance model of each wind turbine. Based on the simplified frequency domain impedance model of each wind turbine, the amplitude-frequency characteristics and phase-frequency characteristics of the overall impedance of the wind farm are determined, and the interaction law between the modulus and phase angle under multi-turbine parallel coupling is obtained. According to the interaction law, additional damping control and active damping control are determined. Based on the topology of the wind farm grid-connected system, an s-domain node admittance matrix is ​​constructed, and the system resonant modes and participation factors of each node are calculated. The node with the highest participation factor is identified as the weak point of the system. For the target wind turbine corresponding to the weak point, an objective function is set according to the improvement requirements of amplitude and phase characteristics. The parameters of the additional damping control and active damping control of the target wind turbine are optimized and tuned using the objective function to obtain optimized control parameters. The optimized control parameters are applied to the target wind turbine to perform broadband oscillation suppression on the wind farm.

[0006] In one embodiment, the step of dynamically reducing the order of each frequency domain impedance model to obtain a simplified frequency domain impedance model for each wind turbine includes: obtaining the transfer function of each control element, calculating the Bode plot of the transfer function of each control element, and determining the corner frequency of each control element based on the Bode plot; calculating the degradation frequency of each control element based on the corner frequency and a preset engineering margin coefficient; comparing the target frequency band with the degradation frequency of each control element for a preset target frequency band; for a target control element whose frequency is higher than the degradation frequency in the target frequency band, simplifying the transfer function of the target control element to an inertial element to obtain the simplified frequency domain impedance model; wherein, the target frequency band is a frequency band prone to broadband oscillations in wind farms, and the selection range of the target frequency band is 0Hz to 300Hz.

[0007] In one embodiment, the degradation frequency is the product of the transition frequency and the engineering margin coefficient; the engineering margin coefficient is 10.

[0008] In one embodiment, the amplitude-frequency characteristic of the overall impedance of the wind farm is expressed by the following formula: ; in, This represents the equivalent impedance modulus of the entire wind farm. This represents the admittance modulus of the wind turbine. This represents the impedance modulus of the wind turbine itself. The phase angle represents the impedance of the wind turbine itself. i and jThese are two distinct wind turbine identifiers used to identify the two different wind turbines in the current calculation. n This refers to the number of wind turbines in the wind farm.

[0009] In one embodiment, the phase frequency characteristic expression of the overall impedance of the wind farm is: ; ;in, The phase angle is the equivalent impedance of the entire wind farm. to express n The impedance phase angle of each typhoon turbine unit, in order to represent to The first in i item, Indicates except the first i Outside of the inverter The phase angle after the inverter impedance vectors are superimposed takes a value between the phase angles of all the impedances involved in the superposition. to express n The impedance vector of each typhoon generator unit.

[0010] In one embodiment, the additional damping control takes a power signal as input, which is filtered and phase-compensated before being superimposed onto the control channel to improve the system's amplitude-frequency characteristics; the transfer function of the additional damping control is expressed by the following formula: ;in, The transfer function representing the additional damping control is... This indicates the center frequency of the bandpass filter. z This indicates the damping ratio of the filter. and The time constants representing lead and lag are used; the inner current transfer function after adding additional damping control is expressed by the following formula: ; ;in, This represents the inner current transfer function after additional damping control. This represents the original inner current transfer function. This represents the additional transfer function resulting from the additional damping control. This represents the voltage amplitude at the grid connection point of the wind turbine unit during steady-state operation of the system.

[0011] In one embodiment, the active damping control includes a low-pass filter and a notch filter. The notch filter is connected in series in the forward path of the current loop to improve the phase frequency characteristics of the system. After adding active damping control, the transfer function of the inner current loop is expressed by the following formula: ;in, This represents the inner current loop transfer function after adding active damping control. This represents the original inner current transfer function. This represents the transfer function of the active damping controller.

[0012] In one embodiment, the objective function includes a first objective function and a second objective function: the first objective function is used to minimize the deviation between the wind turbine impedance phase angle and the target phase angle; the second objective function is used to maximize the sum of the phase angles of the parallel coupling impedances; wherein the target phase angle is configured to be 45° by default.

[0013] In one implementation, the first objective function is expressed as follows: min The second objective function is expressed as follows: max ;in, This represents the impedance of the wind turbine after incorporating active damping control. s Represents the Laplace variable. j Represents the imaginary unit. Represents angular frequency. The parameter vector of the active damping controller to be optimized. Indicates the phase angle of the reference target. This indicates the impedance of the wind turbine with additional damping control. This represents the total equivalent impedance of the active damping control fan and the additional damping control fan connected in parallel. , This represents the characteristic frequency of the low-pass filter in the active damping controller. k This represents the gain coefficient of the active damping controller. This represents the characteristic frequency of the notch filter in the active damping controller. Let represent the damping ratio of the notch filter in the active damping controller; wherein the first objective function and the second objective function satisfy the following constraints: .

[0014] According to a specific embodiment of this application, in a second aspect, this application provides a wind farm broadband oscillation suppression system based on amplitude and phase characteristic reshaping, comprising: The system comprises the following modules: a data acquisition module for acquiring control structure parameters and steady-state operation data of each wind turbine in the wind farm; a modeling and order reduction module for establishing frequency domain impedance models of each wind turbine based on the frequency domain small-signal interference method, and dynamically reducing the order of each frequency domain impedance model to obtain a simplified frequency domain impedance model; a coupling analysis module for determining the amplitude-frequency and phase-frequency characteristics of the overall impedance of the wind farm based on the simplified frequency domain impedance models of each wind turbine, and obtaining the interaction law between the modulus and phase angle under multi-turbine parallel coupling; and a control design module for determining additional damping control and active control based on the interaction law. The system includes a damping control module; an optimized positioning module for constructing an s-domain node admittance matrix based on the topology of the wind farm grid-connected system, calculating the system resonant modes and the participation factors of each node, and identifying the node with the highest participation factor as the weak point of the system; a parameter optimization module for setting an objective function based on the improvement requirements of amplitude and phase characteristics for the target wind turbine corresponding to the weak point of the system, and using the objective function to optimize and tune the parameters of the additional damping control and active damping control of the target wind turbine to obtain optimized control parameters; and an execution module for applying the optimized control parameters to the target wind turbine to perform broadband oscillation suppression on the wind farm.

[0015] Compared with the prior art, the above-described solutions of this application have at least the following beneficial effects: This application provides a method for suppressing broadband oscillations in wind farms based on amplitude-phase characteristic reshaping. First, a frequency domain impedance model of the grid-side converter for direct-drive wind turbines is established. To reduce computational complexity, a dynamic impedance reduction method based on the control loop's distributed frequency band is proposed. Second, the coupling relationship between the wind farm and the amplitude-phase frequency characteristics of a single wind turbine is analyzed. Based on the phase angle neutralization characteristic and amplitude variation law, an impedance reshaping design scheme is proposed. The frequency domain amplitude characteristics of the wind turbine are improved by adding a damping controller, and the frequency domain phase frequency characteristics of the wind turbine are improved by using active damping based on notch filters. A control strategy for amplitude-phase characteristic reshaping is proposed based on the s-domain nodal admittance matrix method. An objective function is constructed based on the requirements for frequency domain amplitude-phase characteristics, and the control parameters are optimized. Attached Figure Description

[0016] Figure 1 A flowchart of a method for suppressing broadband oscillations in wind farms based on amplitude and phase characteristic reshaping is shown; Figure 2 A control structure for a grid-side converter of a direct-drive wind turbine is shown. Figure 3 A control block diagram of a phase-locked loop control structure is shown; Figure 4 This illustrates the frequency band distribution pattern of each control element. Figure 5A block diagram of an additional damping control is shown; Figure 6 A block diagram of an active damping control based on a notch filter is shown. Figure 7 A schematic diagram of a simulation system is shown; Figure 8 A slice diagram showing the three-dimensional relationship between gain, frequency, and phase angle is presented. Figure 9 A schematic diagram of the system's resonant mode variation is shown; Figure 10 A schematic diagram of a node 3 time-domain current waveform is shown; Figure 11 A block diagram of a broadband oscillation suppression system for wind farms based on amplitude and phase characteristic reshaping, according to an embodiment of this application, is shown. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail 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 in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the application. The singular forms “a,” “said,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0019] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0020] It should be understood that although the terms first, second, third, etc., may be used in the embodiments of this application, these descriptions should not be limited to these terms. These terms are only used to distinguish the descriptions. For example, first may also be referred to as second without departing from the scope of the embodiments of this application, and similarly, second may also be referred to as first.

[0021] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0022] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0023] It should be noted that any symbols and / or numbers present in the specification that are not marked in the accompanying drawings are not reference numerals.

[0024] The optional embodiments of this application are described in detail below with reference to the accompanying drawings.

[0025] The embodiments provided in this application are embodiments of a wind farm broadband oscillation suppression method based on amplitude and phase characteristic reshaping.

[0026] The following is combined Figure 1 The embodiments of this application will be described in detail.

[0027] Figure 1 A flowchart of a broadband oscillation suppression method for wind farms based on amplitude and phase characteristic reshaping is shown, as follows: Figure 1 As shown, it includes the following steps; S101. Obtain the control structure parameters and steady-state operation data of each wind turbine in the wind farm. Based on the frequency domain small signal interference method, establish the frequency domain impedance model of each wind turbine and perform dynamic order reduction processing on each frequency domain impedance model to obtain the simplified frequency domain impedance model of each wind turbine.

[0028] The control structure parameters include the parameters of the phase-locked loop, the inner current loop, the outer current loop, and the filtering stage. The steady-state operating data includes the steady-state values ​​of voltage and current.

[0029] S102. Based on the simplified frequency domain impedance model of each wind turbine, determine the amplitude-frequency characteristics and phase-frequency characteristics of the overall impedance of the wind farm, and obtain the interaction law between the modulus and phase angle under multi-turbine parallel coupling.

[0030] S103. Based on the interaction law, determine the additional damping control and the active damping control.

[0031] S104. Based on the topology of the wind farm grid-connected system, construct the node admittance matrix in the s-domain, calculate the system resonant modes and the participation factors of each node, and determine the node with the highest participation factor as the weak point of the system.

[0032] S105. For the target wind turbine corresponding to the weak point of the system, set the objective function according to the improvement requirements of amplitude and phase characteristics, and use the objective function to optimize and tune the parameters of the additional damping control and active damping control of the target wind turbine to obtain the optimized control parameters.

[0033] S106. Apply optimized control parameters to the target wind turbine to perform broadband oscillation suppression on the wind farm.

[0034] In this embodiment, a frequency domain impedance model of the grid-side converter for direct-drive wind turbines is first established. To reduce computational complexity, a dynamic impedance reduction method based on the control loop distributed frequency band is proposed. Secondly, the coupling relationship between the wind farm and the amplitude-phase frequency characteristics of a single wind turbine is analyzed. Based on the phase angle neutralization characteristic and amplitude variation law, an impedance reshaping design scheme is proposed. The frequency domain amplitude characteristics of the wind turbine are improved by adding a damping controller, and the frequency domain phase frequency characteristics of the wind turbine are improved by using active damping based on a notch filter. A control strategy for amplitude-phase characteristic reshaping is proposed based on the s-domain nodal admittance matrix method. An objective function is constructed based on the requirements for frequency domain amplitude-phase characteristics, and the control parameters are optimized.

[0035] The method provided in this application is applicable to various types of wind turbines such as direct-drive wind turbines and doubly-fed wind turbines. For ease of understanding, the following embodiments use a direct-drive wind turbine as an example to illustrate the specific implementation process of steps S101 to S106.

[0036] In some embodiments, in steps S101 and S102, the frequency domain amplitude and phase characteristics of each wind turbine in the wind farm are modeled. The specific modeling process is illustrated below using a direct-drive wind turbine as an example.

[0037] Figure 2 A control structure for a grid-side converter of a direct-drive wind turbine is shown.

[0038] For example, such as Figure 2 As shown, and These are the reference values ​​for the dq axis current of the grid-side converter of the direct-drive wind turbine. and These are the reference values ​​for the dq-axis voltages of the converter. and These are the per-unit values ​​of the dq-axis voltages of the converter. and These represent the per-unit values ​​of the d-q axis currents of the converter, and L is the output inductance. The angular frequency at the power frequency. and The voltage and current values ​​measured at the outlet. It is the transfer function of the inner current loop. This is the measured value of the dq axis voltage. The phase angle is output by the phase-locked loop (PLL). This is the capacitor voltage value. The final output... , After the Park inverse transformation, it enters the PWM power electronic switch.

[0039] In response to the presence of nonlinear elements such as power electronic equipment and Park transform, it is first necessary to establish a frequency domain steady-state model of the nonlinear system. Under the steady-state operating state of the system, a small disturbance signal is superimposed, and the nonlinear elements involved are linearized using methods such as Taylor series expansion and Fourier transform. The input-output linearization model of the grid-connected converter is then established to obtain the small-signal response relationship of voltage and current at the wind turbine outlet. The ratio of the response to the disturbance is the impedance of the system at the disturbance frequency.

[0040] Based on this, by traversing the disturbance frequencies, a small-signal impedance model of the grid-side converter of the direct-drive wind turbine can be established, thereby obtaining its frequency domain amplitude and phase characteristics.

[0041] In some specific embodiments, based on the above derivation logic, the derived expression for the inverter's frequency domain impedance is as follows: ; in, Where L is the inverter's frequency domain impedance, and L is the fan outlet inductance. Let be the disturbance transfer function of the frequency disturbance component of the small-signal interference quantity in the frequency domain from the AC side voltage to the valve side voltage. This is the disturbance transfer function from the output phase of the phase-locked loop to the valve-side voltage. Let be the disturbance transfer function of the frequency disturbance component of the small-signal interference quantity in the frequency domain, from the AC side current to the valve side voltage. , These are the AC voltage and current values ​​during steady-state operation. , These are the reference values ​​for the dq axis during steady-state operation. For frequency domain complex variables, Let j be the complex variable in the frequency domain corresponding to the power frequency, and j be the imaginary unit. Angular frequency is a variable.

[0042] The perturbation transfer functions are expressed as follows: ; in, Let be the disturbance transfer function from the AC side voltage to the phase-locked loop output phase. The transfer function of the phase-locked loop. The transfer function for the power filtering stage. The transfer function for the dq-axis voltage filtering stage. , Here are the transfer functions for per-unit scaling of voltage and current values, respectively, and is a constant. The constant coefficient, The voltage and current phase angle difference during steady-state operation. .

[0043] In related technologies, the control system of a direct-drive wind turbine involves the mutual coordination and constraints of multiple controllers to achieve flexible control and stable operation according to set objectives. However, the interaction between different controllers makes it difficult to distinguish which controller plays a key role in different frequency bands. In this application, in order to more intuitively understand the operation mode of the direct-drive fan controller in the frequency domain, and at the same time reduce the operation and calculation complexity, a dynamic order reduction method suitable for the frequency domain impedance model of the direct-drive fan is proposed, and the specific implementation is shown below.

[0044] For example, the impedance model can be reduced in order across different frequency bands based on the degree of influence of different controllers in different frequency bands.

[0045] As a feasible implementation method, the disturbance transfer function of each control link is first established based on the frequency domain small signal interference method. After decomposing the typical links, the Bode plot of the transfer function and the corner frequency are calculated and solved. After considering the engineering application margin and the fundamental frequency shift, the influence frequency band of the controller is determined. The degradation frequency of the controller is found. After the degradation frequency, the link is reduced in order and simplified. After the degradation of the main controller is completed, the frequency domain reduced impedance model of the direct drive fan is finally established.

[0046] In one specific implementation, step S101 involves dynamically reducing the order of each frequency domain impedance model to obtain a simplified frequency domain impedance model for each wind turbine. This includes: obtaining the transfer function of each control element, calculating the Bode plot of the transfer function of each control element, and determining the corner frequency of each control element based on the Bode plot; calculating the degradation frequency of each control element based on the corner frequency and a preset engineering margin coefficient; comparing the target frequency band with the degradation frequency of each control element for a preset target frequency band; and simplifying the transfer function of the target control element to an inertial element for a target control element with a frequency higher than the degradation frequency in the target frequency band, thereby obtaining a simplified frequency domain impedance model.

[0047] The target frequency band is the frequency band prone to broadband oscillations in wind farms, and the selection range of the target frequency band is 0Hz to 300Hz.

[0048] The degradation frequency is the product of the corner frequency and the engineering margin coefficient.

[0049] Preferably, the engineering margin factor is 10.

[0050] In this application, a simplified frequency domain impedance model can be obtained based on the implementation methods provided in the above embodiments. For ease of understanding, this application will use a phase-locked loop as an example to illustrate the above process.

[0051] Figure 3 A control block diagram of a phase-locked loop control structure is shown.

[0052] For example, the perturbation variable propagation path into the phase-locked loop is as follows: Figure 2 As shown, under the control of the PLL, a small-signal disturbance in the AC voltage will introduce a small-signal component into the phase-locked loop angle. The disturbance transfer function, calculated from the AC voltage measurement to the PLL output phase after passing through the PLL, can be obtained as follows: ; ; in, Represents a Laplace complex variable. This represents the magnitude of the grid voltage during steady-state operation of the system. The linearized model of the phase detector of the phase-locked loop is shown. This constitutes a double integral element, representing the dominant dynamic characteristics of the phase-locked loop in the low-frequency range. This constitutes a first-order differential element, which determines the corner frequencies of the transfer function. This represents the open-loop transfer function of the phase-locked loop controller. This represents the proportional gain in a phase-locked loop (PLL) PI controller. This represents the integral coefficient in the phase-locked loop PI controller.

[0053] Based on the above embodiments, it can be seen that the small disturbance transfer function of the phase-locked loop includes an integral element and a first-order differential element, with a corner frequency of . , Before the turning point, the two integrators play a major role; after the turning point, the integrator and the first derivative work together, effectively leaving only the integrator. This single integral plays a dominant role, reducing the PLL transfer function expression after the corner frequency to just this one integral element.

[0054] Based on this, and considering engineering margins, the degradation frequency of a component is usually taken as ten times the transition frequency. At this point, the phase-locked loop disturbance transfer function in the original full-order impedance expression In It degenerates into having only one inertial link remaining, transforming into... , means as follows: ; ; Furthermore, the inner loop degradation frequency is solved according to the above process. Outer ring degradation frequency and the degradation frequency of the filtering stage Parameters such as [list of parameters] are used to obtain the operating frequency bands of each controller based on the degradation frequency, and the frequency band distribution pattern is organized and output as follows: Figure 4 As shown.

[0055] Figure 4 This illustrates the frequency band distribution pattern of each control element. For example, with Figure 4 Taking the frequency band distribution pattern shown as an example, when analyzing the target frequency band, if we want to analyze the oscillation problem from 100 Hz to 400 Hz, we set this range as the target frequency band and analyze the relationship between the degradation frequency of each controller and the target frequency band. For example, assuming that the phase-locked loop degradation frequency is calculated to be 50 Hz, since all frequencies within the target frequency band are higher than the degradation frequency of the phase-locked loop, the condition is met for simplification, and the transfer function of the phase-locked loop is simplified to an inertial element.

[0056] In some embodiments, after determining the simplified frequency domain impedance model of each wind turbine, the amplitude-frequency and phase-frequency characteristics of the overall wind farm impedance can be determined based on the simplified frequency domain impedance model of each wind turbine, thus obtaining the interaction law between the magnitude and phase angle under multi-turbine parallel coupling. The amplitude-frequency characteristic includes the magnitude of the overall wind farm impedance, and the phase-frequency characteristic includes the phase angle of the overall wind farm impedance. For ease of understanding, the following explanation also uses a direct-drive motor as an example.

[0057] In some specific embodiments, it is assumed that a wind farm is located within... n The impedance of each direct-drive wind turbine is as follows: , … Then the overall impedance expression of the station is: in, This represents the overall impedance of the wind farm. This represents the impedance modulus of the wind turbine itself, and 'i' is the wind turbine identifier used to identify different wind turbines. to express n The impedance vector of each typhoon generator unit.

[0058] Furthermore, as shown in the equation, the overall frequency domain amplitude and phase characteristics of the wind farm are not a linear superposition of the frequency domain impedances of each wind turbine unit in the system; rather, their phase and amplitude are the result of nonlinear coupling of the impedances of each wind turbine unit. Based on the impedance model, the amplitude-frequency and phase-frequency expressions of the wind farm impedance are analyzed separately to explore the impact of multi-turbine amplitude-phase coupling on the overall damping level of the wind farm.

[0059] Specifically, regarding the amplitude-frequency characteristics, the amplitude-frequency characteristics of the overall impedance of a wind farm are expressed by the following formula: ; in, This represents the equivalent impedance modulus of the entire wind farm. This represents the admittance modulus of the wind turbine. This represents the impedance modulus of the wind turbine itself. The phase angle represents the impedance of the wind turbine itself. i and j These are two distinct wind turbine identifiers used to identify the two different wind turbines in the current calculation. n This refers to the number of wind turbines in the wind farm.

[0060] The phase-frequency characteristic of the overall impedance of a wind farm is expressed by the following formula: ; ; in, The phase angle is the equivalent impedance of the entire wind farm. to express n The impedance phase angle of each typhoon turbine unit, in order to represent to The first in i item, Indicates except the first i Outside of the inverter The phase angle after the impedance vectors of the inverters are superimposed, and its value lies between the phase angles of all the impedances involved in the superposition, is defined as the neutralization phase angle in this embodiment. to express n The impedance vector of each typhoon generator unit.

[0061] Furthermore, analysis can be conducted based on the amplitude-frequency characteristic formula and phase-frequency characteristic formula of the overall impedance of the wind farm.

[0062] On the one hand, regarding the amplitude-frequency characteristics of the overall impedance of a wind farm, the amplitude characteristic of the wind farm admittance consists of two turbine coupling components: one is the sum of the squares of the admittance moduli of each turbine, i.e. Under the influence of this component, improving the amplitude characteristics of any wind turbine can enhance the system's amplitude-frequency characteristics; secondly, it is the sum of the products of the admittance magnitudes of any two turbines and the cosine of the phase angle difference, i.e. This component is affected by both the amplitude of each unit and the phase difference between units. The impedance magnitude represents its damping characteristics to some extent, and improving the damping characteristics helps the oscillation mode decay rapidly. Therefore, based on the amplitude-frequency characteristics of the overall wind farm impedance, if we want to increase the magnitude of the parallel coupling impedance of the wind farm, the impedance magnitude of each individual unit should be as large as possible, and the phase angle difference between the impedances should be as large as possible.

[0063] On the other hand, regarding the phase frequency characteristics of the overall impedance of the wind farm, n In the case of multiple inverters connected in parallel, the overall phase angle always lies between the maximum and minimum phase angles of a single inverter. This indicates that the coupling impedance phase characteristics of a parallel system can be effectively controlled by improving the frequency domain phase frequency characteristics of certain individual units, but care must be taken to avoid parallel resonance between multiple units. Therefore, in the process of improving the impedance characteristics of a power station, the coupling effects of the amplitude and phase angle of multiple inverter units must be considered, and the impedance of multiple inverters must be adjusted collaboratively. The method provided in this application, in step S102, can obtain the interaction law between the magnitude and phase angle under multi-machine parallel coupling by using the amplitude-frequency characteristic formula and phase-frequency characteristic formula of the overall impedance of the wind farm in the above embodiments. Furthermore, the design of the control structure can be carried out based on the interaction law.

[0064] In this embodiment, the power system stabilizer can provide positive damping in the excitation control system to reduce oscillation divergence, and therefore has been widely used. Its main principle is as follows: a control signal is superimposed on the excitation control system. If the system is in an unstable state, the input signal causing system instability can be phase-shifted by a phase shifter and input as a feedback control signal to the stabilizer's control system, forming a feedback loop. This adjusts the generator excitation, generating a damping torque to increase the generator's damping of power oscillations. Therefore, additional damping control can be used to enhance the positive damping of the grid-side converter of a direct-drive wind turbine to suppress oscillations. Furthermore, since the selection of the damping controller input signal should be comprehensively considered, it needs to accurately reflect the characteristics or source of system oscillations and be easy to measure and control; therefore, power is selected as the input signal for the additional control.

[0065] Figure 5 A block diagram of an additional damping control is shown.

[0066] For example, such as Figure 5 As shown, the oscillation signal can be filtered by the filtering stage, the phase difference can be adjusted by the phase compensation stage, and the oscillation signal can be superimposed on the output channel by selecting an appropriate gain to achieve oscillation suppression.

[0067] In some embodiments, the additional damping control takes a power signal as input, which is filtered and phase-compensated before being superimposed onto the control channel to improve the system's amplitude-frequency characteristics.

[0068] In some specific embodiments, based on the inverter frequency domain impedance expression in the above embodiments, the expression for the inverter impedance after adding damping control is derived as follows: ; in, Indicates the inverter impedance after additional damping control, in Replace the original part , which represents the inner current transfer function after additional damping control.

[0069] Based on the same logic, the transfer function of the additional damping control is expressed by the following formula: ; in, The transfer function representing the additional damping control is... This indicates the center frequency of the bandpass filter. z This indicates the damping ratio of the filter. and The time constants representing lead and lag.

[0070] Furthermore, the transfer function of the inner current loop after adding additional damping control is expressed by the following formula: ; ; in, This represents the inner current transfer function after additional damping control. This represents the original inner current transfer function. This represents the additional transfer function resulting from the additional damping control. This represents the voltage amplitude at the grid connection point of the wind turbine unit during steady-state operation of the system.

[0071] As can be seen from the frequency band analysis and division of the direct-drive wind turbine in the above embodiments, the inner current loop has a non-negligible influence in the frequency domains prone to oscillation, such as the sub-synchronous / super-synchronous and mid-to-high frequency bands. Therefore, the compensation strategy for the inverter phase characteristics can be used to adjust and optimize the inner current loop.

[0072] In addition to additional damping control, this application also considers the introduction of active damping control.

[0073] For example, active damping control based on notch filters refers to changing the overall impedance characteristics of the converter through series correction in the forward path containing the current controller. This utilizes the characteristics of the notch filter to alter the amplitude and phase response of the original control system, thereby achieving system stability. The main types of cascaded filters are low-pass filters, notch filters, and lead-lag phase compensators.

[0074] Further analysis reveals that the phase-frequency characteristics of the converter determine the wind turbine's oscillation range. Therefore, the frequency domain amplitude-phase characteristics of the wind turbine used in this study exhibit capacitive behavior in the supersynchronous and mid-to-high frequency ranges. Moving closer to resistive-inductive behavior would reduce the risk of resonance with an inductive power grid. In the subsynchronous frequency range, improving the phase margin is more important. Based on the active damping control principle using a notch filter, the overall impedance characteristics of the converter are altered by using a series filter in the current feedforward channel. The notch filter then changes the phase response of the original control system, thereby improving the system damping.

[0075] Figure 6 A block diagram of an active damping control based on a notch filter is shown.

[0076] For example, such as Figure 6 As shown, where Let be the transfer function of the desired filter. Regarding filter selection, considering that a single notch filter or filter is unlikely to achieve phase correction over a long frequency band of 0-300Hz, a series combination of a low-pass filter and a notch filter is chosen to achieve the above objective.

[0077] In some embodiments, active damping control includes a low-pass filter and a notch filter, with the notch filter connected in series in the forward path of the current loop to improve the phase frequency characteristics of the system.

[0078] In some specific embodiments, based on Figure 6 As shown in the control block diagram, the inner current transfer function after adding active damping control is expressed by the following formula: ; in, This represents the inner current loop transfer function after adding active damping control. This represents the original inner current transfer function. This represents the transfer function of the active damping controller.

[0079] Based on the environmental conditions under which the method is applied, it is known that due to the complex and variable resonant modes within actual new energy power plants, modification of only one control structure is insufficient to address broadband oscillation problems. Therefore, synergistic reshaping of two control structures can be performed at weak points in the system. The specific application methods of additional damping control and active damping control are described below in this application.

[0080] In this embodiment of the application, in steps S104 and S105, based on the topology of the wind farm grid-connected system, an s-domain node admittance matrix is ​​constructed, the system resonant modes and the participation factors of each node are calculated, and the node with the highest participation factor is determined as the weak point of the system; for the target wind turbine corresponding to the weak point of the system, an objective function is set according to the improvement requirements of amplitude and phase characteristics, and the parameters of the additional damping control and active damping control of the target wind turbine are optimized and tuned using the objective function to obtain the optimized control parameters.

[0081] As a feasible implementation method, the system resonant modes and damping ratios can be directly solved using the s-domain nodal admittance matrix method. Furthermore, the calculated nodal participation factor represents the optimal controllable and observable node for the system's resonant modes, which is the identified weak point in the system, i.e., the grid-connected node of the wind turbine with the highest participation in a specific broadband oscillation mode. Since wind turbines are generally located at the end of the power line, optimizing the control structure of the terminal units is crucial to regulating the impedance characteristics of the optimal node.

[0082] The additional damping controller is designed to improve the overall damping of the converter in the oscillation-prone frequency range from 0Hz to 300Hz.

[0083] On the one hand, the parameter tuning of the active damping strategy can be based on the following principles: it is hoped that after configuring active damping control, the frequency domain impedance characteristics of this wind turbine will be close to resistive-inductive in the sub-synchronous / super-synchronous and mid-to-high frequency bands. Furthermore, the parallel coupling impedance should be inductive in the sub-synchronous / super-synchronous frequency bands, while avoiding resonance with another wind turbine. That is, the phase angle of the parallel impedance should be far from the zero-degree axis, but to maintain good damping characteristics, the phase angle should not be too large.

[0084] On the other hand, for additional damping control, the filter parameters and the time constant of the phase lead / lag function can be determined by an iterative method. The corresponding objective function and iterative process will not be elaborated here.

[0085] Based on the above embodiments, it can be seen that after obtaining the complete parameters and impedance characteristics of the additional damping control, this application can carry out the design and tuning of the active damping control parameters. The parameters that need to be tuned are the low-pass filter characteristic frequency, the overall transfer function gain, the notch filter characteristic frequency, and the damping ratio, which correspond to the design objective function.

[0086] In some embodiments, for active damping control, the objective function includes a first objective function and a second objective function. The first objective function aims to configure the frequency domain impedance characteristics of the wind turbine to be close to resistive-inductive in the sub-synchronous / super-synchronous and mid-to-high frequency bands after active damping control. The second objective function aims to ensure that the parallel coupling impedance is inductive in the sub-synchronous / super-synchronous frequency bands, while avoiding resonance with another wind turbine.

[0087] In some specific embodiments, the first objective function can be defined as minimizing the deviation between the wind turbine impedance phase angle and the target phase angle, and the second objective function can be defined as maximizing the sum of the phase angles of the parallel coupling impedances, with the target phase angle configured by default as 45°.

[0088] Specifically, the first objective function is expressed as follows: min ; in, This represents the impedance of the wind turbine after incorporating active damping control. s Represents the Laplace variable. j Represents the imaginary unit. Represents angular frequency. The parameter vector of the active damping controller to be optimized.

[0089] The second objective function is expressed as follows: max ; in, This represents the impedance of the wind turbine after incorporating active damping control. s Represents the Laplace variable. j Represents the imaginary unit. Represents angular frequency. The parameter vector of the active damping controller to be optimized. Indicates the phase angle of the reference target. This indicates the impedance of the wind turbine with additional damping control. This represents the total equivalent impedance of the active damping control fan and the additional damping control fan connected in parallel.

[0090] In the above embodiments, the active damping controller parameter vector to be optimized The following representation is used: ; in, This represents the characteristic frequency of the low-pass filter in the active damping controller. k This represents the gain coefficient of the active damping controller. This represents the characteristic frequency of the notch filter in the active damping controller. This indicates the damping ratio of the notch filter in the active damping controller.

[0091] In the above embodiments, the first objective function and the second objective function satisfy the following constraints: ; in, This represents the characteristic frequency of the low-pass filter in the active damping controller. k This represents the gain coefficient of the active damping controller. This represents the characteristic frequency of the notch filter in the active damping controller. This indicates the damping ratio of the notch filter in the active damping controller.

[0092] In the above embodiments, to distinguish between wind turbines with two different additional control structures, in addition to optimizing the control structure, in a multi-wind turbine environment, the wind turbines are coupled together through a collector network, with different electrical distances and degrees of interaction. Therefore, it is also necessary to select the optimal coupling turbine among the wind turbines connected to the weakest point. The first objective function represents finding the minimum sum of impedance phase angles, and the second objective function represents finding the sum of phase angles of the parallel coupling impedances, which is the target phase angle. Since the second objective function already considers the impedance coupling phase angle, damping characteristics are not further considered. However, in practical applications, constraints on the impedance amplitude can still be introduced similarly to the first objective function.

[0093] Based on the above implementation method, the optimal location for amplitude-phase optimized branch access can be obtained, achieving a balance between maximizing damping performance and minimizing control costs. Therefore, in step S106, the optimized control parameters are applied to the target wind turbine corresponding to the weak point of the system to perform broadband oscillation suppression on the wind farm.

[0094] In some further embodiments, simulation verification can be performed on the above-described implementation methods.

[0095] Figure 7 A schematic diagram of a simulation system is shown.

[0096] Figure 8 A slice diagram showing the three-dimensional relationship between gain, frequency, and phase angle is shown.

[0097] As one feasible implementation, such as Figure 7 As shown, electrical energy is transmitted via a 220kV cable after passing through a 35kV collector. A system node admittance matrix is ​​constructed, and stability analysis is performed using the s-domain node admittance matrix method with a frequency resolution of 1Hz. The analytical results show an oscillation risk at 96Hz, with node 10 having the highest participation factor among the inverter nodes. After applying a disturbance to the system, the resonant mode is excited. FFT analysis of the time-domain waveform reveals a resonant frequency of 97.6Hz, which is close to the calculated resonant mode, and the error is within an acceptable range.

[0098] Furthermore, the cooperative control parameters are solved according to the objective function, where n=6 and 45° is set as the target phase angle. The solution results are shown in Table 1 below.

[0099] Table 1 Among them, the optimal cooperative control position is Figure 7Of the 11 nodes, only the gain parameter was inconsistent. Further analysis of the parameter sensitivity revealed that the impedance phase angle is extremely sensitive to the gain. Therefore, the relationship between gain and converter impedance and coupling impedance was established.

[0100] like Figure 8 As shown, the phase angle change is basically smooth; therefore, three frequencies were chosen to represent the sub / supersynchronous band and the mid-to-high frequency band. Figure 8 As shown, the impedance in the mid-to-high frequency band is not sensitive to changes in gain, but it changes significantly in the subsynchronous / supersynchronous phase, and the trends are opposite. The phase angle of the wind turbine and parallel coupling impedance increases with the increase of gain in the subsynchronous frequency band. When the gain is small, the coupling impedance is close to resistive. In the supersynchronous frequency band, the impedance decreases with the increase of gain. When the gain is large, the coupling impedance is close to resistive. In order to reduce the frequency range in which the coupling impedance approaches the resistive characteristic, 0.02 is selected as the final gain parameter.

[0101] Figure 9 A schematic diagram of the system's resonant mode variation is shown.

[0102] Figure 10 A schematic diagram of a node 3 time-domain current waveform is shown.

[0103] Depend on Figure 9 and Figure 10 It can be seen that when wind turbines No. 10 and No. 11 adopt the amplitude and phase characteristic reshaping combination strategy, the system resonance is basically suppressed. The resonance mode analysis results show that the resonance mode amplitude without control is significantly larger than that of the simulated system after impedance co-reconstruction. The time-domain power oscillation in the supersynchronous frequency band is suppressed, and the amplitude of the oscillation component is reduced by more than 90%. Therefore, the method provided in this application is effective.

[0104] This application provides an implementation scheme for a broadband oscillation suppression method for wind farms based on amplitude and phase characteristic reshaping. This method reveals the multi-machine parallel coupling law by performing frequency domain impedance modeling and analysis on each wind turbine in the wind farm, and designs a collaborative control strategy accordingly. Finally, it achieves effective suppression of broadband oscillations through parameter optimization.

[0105] In some embodiments, establishing the frequency domain impedance model of a wind turbine includes the following process: First, the control structure parameters and steady-state operating data of each wind turbine in the wind farm are obtained. The control structure parameters include the control parameters of the phase-locked loop (PLL), the inner current loop, and the filtering stage. The steady-state operating data includes the steady-state operating point values ​​of voltage and current. Based on the frequency domain small-signal linearization method, a frequency domain impedance model for each wind turbine is established. To reduce model complexity, the frequency domain impedance model is dynamically reduced in order based on the influence of each control element in different frequency bands, resulting in a simplified frequency domain impedance model for each wind turbine. For example, for the PLL control element, the degradation frequency is determined by calculating its Bode plot and corner frequency. In frequency bands higher than this degradation frequency, the PLL transfer function is simplified to an inertial element.

[0106] As a feasible implementation, the analysis of multi-turbine coupling characteristics of a wind farm is achieved through the following method: Based on a simplified frequency domain impedance model of each wind turbine, the overall equivalent impedance of the wind farm at the point of common coupling is obtained by calculating the vector sum of the admittances of all wind turbines, thereby determining the mode-frequency and phase-frequency characteristics of the overall wind farm impedance. By analyzing the mathematical expressions of the mode-frequency and phase-frequency characteristics, the interaction law between the magnitude and phase angle under multi-turbine parallel coupling is obtained. Specifically, the mode-frequency characteristic characterizes the relationship between the amplitude of the overall wind farm impedance and frequency, and the phase-frequency characteristic characterizes the relationship between the phase of the overall wind farm impedance and frequency.

[0107] As a specific embodiment, the design of additional damping control and active damping control includes the following steps: Based on the aforementioned interaction law, an additional damping control structure and an active damping control structure are designed. The additional damping control structure is designed based on the principle of a power system stabilizer, using a power signal as input, which is filtered and phase-compensated before being superimposed onto the control channel to improve the system's damping characteristics. The active damping control structure is based on a notch filter design, connected in series in the forward channel of the current loop to improve the system's phase-frequency characteristics. For example, the transfer function of the additional damping control structure includes a gain stage, a bandpass filter stage, and a phase compensation stage; the transfer function of the active damping control structure is a series combination of a low-pass filter and a notch filter.

[0108] In some embodiments, determining the system's weak points and optimizing control parameters is achieved through the following process: Based on the topology of the wind farm grid-connected system, an s-domain node admittance matrix is ​​constructed, the system resonant modes and the participation factors of each node are calculated, and the node with the highest participation factor is determined as the system's weak point. For the target wind turbine corresponding to the system's weak point, an objective function is set according to the improvement requirements for the mode frequency and phase frequency characteristics. The parameters of the additional damping control and active damping control of the target wind turbine are optimized using the objective function to obtain the optimized control parameters. For example, the objective function includes minimizing the deviation between the wind turbine's impedance phase angle and the target phase angle, and maximizing the sum of the phase angles of the parallel coupling impedance.

[0109] As a feasible implementation, the control effect is verified by applying the optimized control parameters to the target wind turbine, establishing a multi-turbine grid-connected system model, and conducting time-domain simulation verification. The effectiveness of the broadband oscillation suppression method is verified by comparing the amplitude changes of the system's resonant modes and the attenuation of time-domain power oscillations before and after applying control. For example, the amplitude reduction ratio of the oscillation component at the resonant frequency can be calculated by analyzing the time-domain waveform using Fast Fourier Transform.

[0110] The broadband oscillation suppression method for wind farms provided in this application has broad applicability. For different wind farm engineering scenarios, targeted oscillation suppression can be achieved by adjusting the branch positions, number, and control parameters of additional damping control and active damping control. The method forms a complete technical closed loop through systematic frequency domain modeling, coupling analysis, control design, and parameter optimization, which can effectively improve the stability of the power system under high-proportion renewable energy access.

[0111] This application also provides system embodiments that follow the above embodiments, for implementing the method steps described in the above embodiments. The interpretation of the same names is the same as that in the above embodiments, and they have the same technical effects as those in the above embodiments, so they will not be repeated here.

[0112] like Figure 11 As shown, this application provides a broadband oscillation suppression system 1100 for wind farms based on amplitude and phase characteristic reshaping, comprising: The data acquisition module 1101 is used to acquire the control structure parameters and steady-state operation data of each wind turbine in the wind farm.

[0113] The modeling and order reduction module 1102 is used to establish the frequency domain impedance model of each wind turbine based on the frequency domain small signal interference method, and to perform dynamic order reduction processing on each frequency domain impedance model to obtain a simplified frequency domain impedance model of each wind turbine.

[0114] The coupling analysis module 1103 is used to determine the amplitude-frequency characteristics and phase-frequency characteristics of the overall impedance of the wind farm based on the simplified frequency domain impedance model of each wind turbine, and to obtain the interaction law between the modulus and phase angle under multi-turbine parallel coupling.

[0115] The control design module 1104 is used to determine the additional damping control and the active damping control based on the interaction law.

[0116] The optimized positioning module 1105 is used to construct the s-domain node admittance matrix based on the topology of the wind farm grid-connected system, calculate the system resonant modes and the participation factors of each node, and determine the node with the highest participation factor as the weak point of the system.

[0117] The parameter optimization module 1106 is used to set an objective function for the target wind turbine corresponding to the weak point of the system, based on the improvement requirements of amplitude and phase characteristics, and to optimize and tune the parameters of the additional damping control and active damping control of the target wind turbine using the objective function, so as to obtain the optimized control parameters.

[0118] The execution module 1107 is used to apply optimized control parameters to the target wind turbine to perform broadband oscillation suppression on the wind farm.

[0119] Regarding the system in the above embodiments, the specific ways in which each module performs operations have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0120] Although the operations are described in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order or serial order shown, or requiring all of the operations shown to obtain the desired result. In certain environments, multitasking and parallel processing may be advantageous.

[0121] The methods and systems of this application can be implemented using standard programming techniques, utilizing rule-based logic or other logic to implement various method steps. It should also be noted that the terms "system" and "module" as used herein and in the claims are intended to include implementations using one or more lines of software code and / or hardware implementations and / or devices for receiving input.

[0122] Any step, operation, or procedure described herein may be performed or implemented using one or more hardware or software modules, either alone or in combination with other devices. In one embodiment, the software module is implemented using a computer program product comprising a computer-readable medium containing computer program code, which is executable by a computer processor to perform any or all of the described steps, operations, or procedures.

[0123] The foregoing description of implementations of this application has been provided for illustrative and descriptive purposes. The foregoing description is not exhaustive and is not intended to limit this application to the exact forms disclosed. Various modifications and variations may exist in accordance with the foregoing teachings, or may arise from practice of this application. These embodiments were chosen and described to illustrate the principles of this application and its practical application, enabling those skilled in the art to utilize this application in various implementations and modifications to suit the specific purpose of the concept.

[0124] Regarding the system in the above embodiments, the specific ways in which each module performs operations have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0125] It can be further understood that, unless otherwise specified, "connection" includes both direct connections where no other components exist between the two parties and indirect connections where other components exist between them.

[0126] It is further understood that although the operations are described in a specific order in the accompanying drawings in the embodiments of this application, this should not be construed as requiring these operations to be performed in the specific order or serial order shown, or requiring all the operations shown to be performed to obtain the desired result. In certain environments, multitasking and parallel processing may be advantageous.

[0127] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the field of this application that are not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0128] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

[0129] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 application.

Claims

1. A method for suppressing broadband oscillations in wind farms based on amplitude and phase characteristic reshaping, characterized in that, Includes the following steps: The control structure parameters and steady-state operation data of each wind turbine in the wind farm are obtained respectively. Based on the frequency domain small signal interference method, the frequency domain impedance model of each wind turbine is established, and the frequency domain impedance model is dynamically reduced to obtain the simplified frequency domain impedance model of each wind turbine. Based on the simplified frequency domain impedance model of each wind turbine, the amplitude-frequency characteristics and phase-frequency characteristics of the overall impedance of the wind farm are determined, and the interaction law between the modulus and phase angle under multi-turbine parallel coupling is obtained. Based on the aforementioned interaction law, additional damping control and active damping control are determined; Based on the topology of the wind farm grid-connected system, an s-domain node admittance matrix is ​​constructed, the system resonant modes and the participation factors of each node are calculated, and the node with the highest participation factor is identified as the weak point of the system. For the target wind turbine corresponding to the weak point of the system, an objective function is set according to the improvement requirements of amplitude and phase characteristics. The parameters of the additional damping control and active damping control of the target wind turbine are optimized and tuned using the objective function to obtain the optimized control parameters. The optimized control parameters are applied to the target wind turbine to perform broadband oscillation suppression on the wind farm.

2. The method according to claim 1, characterized in that, The process of dynamically reducing the order of each frequency domain impedance model to obtain a simplified frequency domain impedance model for each wind turbine includes: Obtain the transfer function of each control element, calculate the Bode plot of the transfer function of each control element, and determine the corner frequency of each control element based on the Bode plot. Based on the aforementioned transition frequency and combined with a preset engineering margin coefficient, the degradation frequency of each control element is calculated. For a preset target frequency band, the target frequency band is compared with the degradation frequency of each control link; For a target control element whose frequency is higher than the degradation frequency in the target frequency band, the transfer function of the target control element is simplified to an inertial element to obtain the simplified frequency domain impedance model. The target frequency band is the frequency band prone to broadband oscillations in wind farms, and the selection range of the target frequency band is 0Hz to 300Hz.

3. The method according to claim 2, characterized in that, The degradation frequency is the product of the cutoff frequency and the engineering margin coefficient; The project margin factor is 10.

4. The method according to claim 1, characterized in that, The amplitude-frequency characteristic of the overall impedance of the wind farm is expressed by the following formula: ； in, This represents the equivalent impedance modulus of the entire wind farm. This represents the admittance modulus of the wind turbine. This represents the impedance modulus of the wind turbine itself. The phase angle represents the impedance of the wind turbine itself. i and j These are two distinct wind turbine identifiers used to identify the two different wind turbines in the current calculation. n This refers to the number of wind turbines in the wind farm.

5. The method according to claim 1, characterized in that, The phase frequency characteristic expression of the overall impedance of the wind farm is as follows: ； ； in, The phase angle is the equivalent impedance of the entire wind farm. to express n The impedance phase angle of each typhoon turbine unit, in order to represent to The first in i item, Indicates except the first i Outside of the inverter The phase angle after the inverter impedance vectors are superimposed takes a value between the phase angles of all the impedances involved in the superposition. to express n The impedance vector of each typhoon generator unit.

6. The method according to claim 1, characterized in that, The additional damping control takes a power signal as input, and after filtering and phase compensation, it is superimposed on the control channel to improve the system's amplitude-frequency characteristics. The transfer function of the additional damping control is expressed by the following formula: ； in, The transfer function representing the additional damping control is... This indicates the center frequency of the bandpass filter. z This indicates the damping ratio of the filter. and The time constants representing lead and lag; With the addition of additional damping control, the transfer function of the inner current loop is expressed by the following formula: ； ； in, This represents the inner current transfer function after additional damping control. This represents the original inner current transfer function. This represents the additional transfer function resulting from the additional damping control. This represents the voltage amplitude at the grid connection point of the wind turbine unit during steady-state operation of the system.

7. The method according to claim 1, characterized in that, The active damping control includes a low-pass filter and a notch filter, with the notch filter connected in series in the forward channel of the current loop to improve the phase frequency characteristics of the system. The transfer function of the inner current loop after incorporating active damping control is expressed by the following formula: ； in, This represents the inner current loop transfer function after adding active damping control. This represents the original inner current transfer function. This represents the transfer function of the active damping controller.

8. The method according to claim 1, characterized in that, The objective function includes a first objective function and a second objective function: The first objective function is used to minimize the deviation between the wind turbine impedance phase angle and the target phase angle; The second objective function is used to maximize the sum of the phase angles of the parallel coupling impedances; The target phase angle is configured to be 45° by default.

9. The method according to claim 8, characterized in that, The first objective function is expressed as follows: min ; The second objective function is expressed as follows: max ; in, This represents the impedance of the wind turbine after incorporating active damping control. s Represents the Laplace variable. j Represents the imaginary unit. Represents angular frequency. The parameter vector of the active damping controller to be optimized. Indicates the phase angle of the reference target. This indicates the impedance of the wind turbine with additional damping control. This represents the total equivalent impedance of the active damping control fan and the additional damping control fan connected in parallel. , This represents the characteristic frequency of the low-pass filter in the active damping controller. k This represents the gain coefficient of the active damping controller. This represents the characteristic frequency of the notch filter in the active damping controller. This indicates the damping ratio of the notch filter in the active damping controller; Wherein, the first objective function and the second objective function satisfy the following constraints: 。 10. A broadband oscillation suppression system for wind farms based on amplitude and phase characteristic reshaping, characterized in that, include: The data acquisition module is used to acquire the control structure parameters and steady-state operation data of each wind turbine in the wind farm. The modeling and order reduction module is used to establish the frequency domain impedance model of each wind turbine based on the frequency domain small signal interference method, and to perform dynamic order reduction processing on each frequency domain impedance model to obtain a simplified frequency domain impedance model of each wind turbine. The coupling analysis module is used to determine the amplitude-frequency and phase-frequency characteristics of the overall impedance of the wind farm based on the simplified frequency domain impedance model of each wind turbine, and to obtain the interaction law between the modulus and phase angle under multi-turbine parallel coupling. The control design module is used to determine the additional damping control and the active damping control based on the interaction law. An optimized positioning module is used to construct an s-domain node admittance matrix based on the topology of a wind farm grid-connected system, calculate the system resonant modes and the participation factors of each node, and determine the node with the highest participation factor as the weak point of the system. The parameter optimization module is used to set an objective function for the target wind turbine corresponding to the weak point of the system, based on the improvement requirements of amplitude and phase characteristics, and to optimize and tune the parameters of the additional damping control and active damping control of the target wind turbine using the objective function to obtain optimized control parameters. An execution module is used to apply the optimized control parameters to the target wind turbine to perform broadband oscillation suppression on the wind farm.

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