Oscillation suppression method and system based on impedance reshaping of high-inertia energy storage type phase modifier

Abstract

The present application belongs to the technical field of power system oscillation suppression, and specifically discloses an oscillation suppression method and system based on high-inertia energy storage type phase modifier impedance remodeling, which comprises the following steps: identifying a target suppression frequency band; obtaining the active power signal of a grid-connected new energy unit or new energy station, and performing band-pass filtering to obtain the subsynchronous and / or supersynchronous oscillation component of the target suppression frequency band; performing asymmetric complex number lead correction on the oscillation component; after amplitude shaping and safety limiting of the phase-compensated signal, the signal is injected into the rotor-side converter power outer ring of the high-inertia energy storage type phase modifier as an additional control signal to form an additional power deviation; the deviation is output as a rotor-side current reference value after PI regulation, and then a damping power opposite to the oscillation component is formed on the stator side to remodel the equivalent output impedance of the point of common coupling. The present application can suppress the subsynchronous and / or supersynchronous oscillation of the new energy station.

Description

Technical Field

[0001] This invention relates to the field of power system oscillation suppression technology, and in particular to an oscillation suppression method and system based on impedance reshaping of a high-inertia energy storage synchronous condenser. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] With the significant enhancement of dynamic coupling between new energy power plants and weak power grids, system stability issues have become increasingly prominent, among which broadband oscillation is a typical problem.

[0004] For renewable energy generator units connected to the grid via converters, such as wind turbines, under specific grid strength, control parameters, and operating conditions, renewable energy power plants may experience subsynchronous and / or supersynchronous oscillations in the 1–100 Hz frequency band. These oscillations not only manifest as oscillation frequencies spanning a wide frequency band but may also be accompanied by coupling between different frequency components. For example, when renewable energy power plants operate under weak grid conditions, multi-time-scale couplings can occur between the power plant-side converter control loop, the grid equivalent impedance, and the internal network of the power plant. The interaction between the power loop, current loop, phase-locked loop, and network resonant modes can easily cause a simultaneous decrease in damping in both the subsynchronous and supersynchronous frequency bands, resulting in coupled oscillations of active power fluctuations, grid-connected current oscillations, and bus voltage disturbances. In severe cases, this can jeopardize the safe and stable operation of the grid-connected system.

[0005] Existing methods for suppressing broadband oscillations at renewable energy power plants mainly fall into two categories: adding damping or compensation devices and adjusting the control parameters of grid-connected equipment. The former typically compensates for specific frequency points, has a limited scope of application, and increases equipment investment and engineering modification costs; the latter, while not adding hardware, often requires a trade-off between dynamic performance and stability margin. After migrating parameters to different grid strengths or different operating points, the oscillation suppression effect is prone to decrease, and may even introduce new oscillation risks. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes an oscillation suppression method and system based on impedance reshaping of a high-inertia energy storage synchronous condenser. Utilizing the characteristics of the high-inertia energy storage synchronous condenser rotor-side converter's power outer loop—which combines an adjustable active power channel with good engineering accessibility—an additional control signal is injected into the rotor-side converter's power outer loop to reshape the equivalent output impedance of the common coupling point, thereby improving the phase margin in the target frequency band and suppressing subsynchronous and / or supersynchronous oscillations at renewable energy power plants under weak grid conditions.

[0007] In some implementations, the following technical solutions are adopted: An oscillation suppression method based on impedance reshaping of a high-inertia energy storage phase shifter includes: By combining the small-signal impedance model of high-inertia energy storage synchronous condenser with that of grid-connected new energy power station, the target suppression frequency band can be identified. Acquire the active power signal of the grid-connected renewable energy unit or renewable energy power station; perform bandpass filtering on the active power signal to obtain the subsynchronous and / or supersynchronous oscillation components of the target suppressed frequency band; The oscillation component is subjected to asymmetric complex lead correction to compensate for insufficient phase margin; After phase compensation, the signal is shaped and limited for safety, and then injected as an additional control signal into the power outer loop of the rotor-side converter of the high-inertia energy storage type synchronous condenser to form an additional power deviation. The deviation is adjusted by a PI controller to output a reference value for the rotor-side current, which in turn generates damping power on the stator side that is opposite to the oscillation component. This power is used to reshape the equivalent output impedance of the common coupling point, thereby suppressing subsynchronous and / or supersynchronous oscillations in new energy power plants.

[0008] As a further approach, a combined analysis of the high-inertia energy storage synchronous condenser and the small-signal impedance model of the grid-connected renewable energy power station is conducted to identify the target suppression frequency band, specifically: A small-signal impedance model of the main circuit and control loop of a high-inertia energy storage synchronous condenser is established to obtain the equivalent impedance on the station side. By combining the equivalent impedance on the station side and the equivalent impedance on the grid side, the amplitude-frequency crossover point is identified, and at each crossover frequency point, the difference between the phase angle of the station impedance and the phase angle of the grid impedance is calculated. The dominant oscillation frequency is identified by the phase margin criterion, and the target suppression frequency band is determined. The accuracy of the dominant oscillation frequency is further verified by the Nyquist criterion.

[0009] As a further option, the target suppression frequency band includes at least one subsynchronous oscillation frequency band and / or at least one supersynchronous oscillation frequency band in the range of 1 to 100 Hz.

[0010] As a further solution, the active power signal of the grid-connected renewable energy unit or renewable energy power station is specifically: the active power signal of a single renewable energy unit, the aggregated active power signal of the renewable energy power station, or the equivalent active power signal obtained by weighted summation of the active power signals of multiple renewable energy units.

[0011] As a further solution, the active power signal is bandpass filtered, and the transfer function of the bandpass filter is: ; in, s Let Laplace be a complex variable. ω0 is the bandpass center frequency, set at or near the dominant oscillation frequency; H 0 represents the gain at the bandpass center frequency. Q 0 is the quality factor, used to characterize the bandpass width.

[0012] As a further solution, the oscillation component is subjected to asymmetric complex lead correction, and the transfer function of the asymmetric complex lead correction module is: ; in, ξ z This is the first damping ratio, used to provide phase lead compensation near the resonance point; ξ p This is the second damping ratio, used to delay phase fall-off and maintain phase margin over a wider frequency band. ξ z < ξ p ; ω z The complex zero frequency is set near the dominant oscillation frequency. ω p The frequency of the complex poles is set far from the dominant oscillation frequency.

[0013] As a further solution, when the amplitude, peak value of the spectral value or equivalent energy index of the subsynchronous and / or supersynchronous oscillation components in the target suppression frequency band exceeds the preset start-up threshold, the above-mentioned oscillation suppression method based on impedance reshaping of high inertia energy storage type phase shifter is triggered. When the amplitude, peak value or equivalent energy index of the subsynchronous and / or supersynchronous oscillation components in the target suppression frequency band decreases to below the preset start-up threshold, the output of the additional control signal is gradually reduced according to the preset slope to reduce the disturbance of the control switching on the original power regulation channel.

[0014] In other embodiments, the following technical solutions are adopted: An oscillation suppression system based on impedance reshaping of a high-inertia energy storage phase shifter includes: The target suppression frequency band determination module is configured to combine and analyze the small-signal impedance models of high-inertia energy storage synchronous condensers and grid-connected new energy power stations to identify the target suppression frequency band. The signal acquisition module is configured to acquire the active power signal of grid-connected renewable energy units or renewable energy power plants; The preprocessing module is configured to perform bandpass filtering on the active power signal to obtain the subsynchronous and / or supersynchronous oscillation components of the target suppressed frequency band; The phase compensation module is configured to perform asymmetric complex lead correction on the oscillation component to compensate for insufficient phase margin. The gain limiting module is configured to perform amplitude shaping and safety limiting on the phase-compensated signal; The control injection module is configured to inject the limited signal as an additional control signal into the power outer loop of the rotor-side converter of the high-inertia energy storage type synchronous condenser. The execution module is configured to generate an additional power deviation based on the additional control signal; the deviation is PI-regulated and outputs a rotor-side current reference value, thereby generating a damping power on the stator side that is opposite to the oscillation component, so as to reshape the equivalent output impedance of the common coupling point and thus suppress subsynchronous and / or supersynchronous oscillations of the new energy power station.

[0015] In other embodiments, the following technical solutions are adopted: A terminal device includes a processor and a memory, wherein the processor is used to implement instructions; and the memory is used to store multiple instructions adapted to be loaded and executed by the processor for the above-described oscillation suppression method based on impedance reshaping of a high-inertia energy storage type phase shifter.

[0016] In other embodiments, the following technical solutions are adopted: A computer-readable storage medium storing a plurality of instructions adapted for loading and execution by a processor of a terminal device of the above-described oscillation suppression method based on impedance reshaping of a high-inertia energy storage type phase shifter.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention fully utilizes the kinetic energy buffering capacity of high-inertia energy storage synchronous condensers and the reactive power support capacity of synchronous condensers, providing energy support and oscillation damping for the system without the need for additional dedicated damping compensation hardware. The use of an additional control structure based on the RSC power outer loop avoids the saturation and robustness degradation problems caused by directly implementing high-gain compensation in the fast current loop, demonstrating good engineering feasibility. By reshaping the equivalent output impedance at the PCC point, the phase margin in the target frequency band under weak grid conditions is improved, enhancing the broadband oscillation suppression capability and operational stability of the grid-connected power station.

[0018] This invention uses the oscillating component of the active power output from new energy generating units or new energy power plants as feedback information, which can more directly characterize the energy exchange state between the power plant and the power grid. Compared with control constructed using only local voltage or current signals, this feedback quantity reflects the system-level oscillation characteristics more fully, and the target of vibration suppression is more clearly defined, thus having stronger pertinence.

[0019] Other features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] Figure 1 This is a flowchart of the oscillation suppression method based on impedance reshaping of a high-inertia energy storage phase shifter in an embodiment of the present invention; Figure 2 This is a GSC control topology diagram of a high-inertia energy storage type synchronous condenser in an embodiment of the present invention; Figure 3 This is a diagram of the RSC control topology before impedance reshaping of a high-inertia energy storage phase shifter in this embodiment of the invention. Figure 4 This is a diagram of the RSC control topology after adding additional control signals in an embodiment of the present invention. Figure 5 This is a grid connection topology diagram of a high-inertia energy storage synchronous condenser and a wind farm in an embodiment of the present invention; Figure 6 This is a diagram showing the small-signal theoretical impedance model and measured sweep frequency curve of a wind farm with a high-inertia energy storage synchronous condenser before impedance reshaping in an embodiment of the present invention. Figure 7 This is a waveform diagram of the active power of the wind farm before impedance reshaping in an embodiment of the present invention; Figure 8 This is a spectrum diagram of the active power of a wind farm before impedance reshaping in an embodiment of the present invention, obtained through FFT analysis. Figure 9 The above are the measured frequency sweep curves and grid impedance characteristics of a wind farm with a high-inertia energy storage synchronous condenser after impedance reshaping in this embodiment of the invention. Figure 10 This is a comparison diagram of the active power waveforms of the wind farm before and after impedance reshaping in an embodiment of the present invention; Figure 11 This is a spectrum diagram of the active power of a wind farm after impedance reshaping in an embodiment of the present invention, obtained through FFT analysis. Detailed Implementation

[0021] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Example 1 High Inertia Energy Storage Synchronous Condenser (HIESSC) combines the dynamic reactive power support capability of synchronous condensers with the kinetic energy buffering capability of high-inertia rotors, and has demonstrated application value in voltage support, short-circuit capacity enhancement, and frequency support. However, current applications of HIESSC mainly focus on inertia support and reactive power regulation, lacking a complete technical route for using the controllable power channel on the rotor side of HIESSC for impedance reshaping in renewable energy power plants. In particular, no method or system has yet been found to address subsynchronous and / or supersynchronous oscillation suppression in renewable energy power plants, leveraging the adjustable output impedance, rapid rotor kinetic energy exchange, and ease of superimposing additional control on the RSC power outer loop of the rotor-side converter, based on the characteristics of HIESSC.

[0024] Based on this, in order to address the problems that new energy power plants may simultaneously experience insufficient damping in the subsynchronous and supersynchronous frequency bands under weak grid conditions, and that existing vibration suppression methods have narrow applicable frequency bands, poor parameter mobility, and large engineering modifications, one or more embodiments disclose an oscillation suppression method based on impedance reshaping of a high-inertia energy storage synchronous condenser. This method relies on the existing control channel of the high-inertia energy storage synchronous condenser to implement impedance reshaping, thereby improving the broadband oscillation stability of grid-connected power plants without changing the main circuit hardware topology of the main equipment.

[0025] Combination Figure 1 The oscillation suppression method based on impedance reshaping of a high-inertia energy storage phase shifter specifically includes the following process: S101: Combine the analysis of high-inertia energy storage synchronous condensers with the small-signal impedance model of grid-connected new energy power stations to identify the target suppression frequency band.

[0026] In this embodiment, an impedance analysis model of a high-inertia energy storage synchronous condenser and a grid-connected renewable energy power station is first established. The main circuit model of the high-inertia energy storage synchronous condenser includes a motor module, a phase-locked loop (PLL) module, a filter module, and a DC bus control module; the control loop model includes a grid-side converter (GSC) control section and a rotor-side converter (RSC) control section; wherein, the GSC control section includes a voltage outer loop, a current inner loop, and a modulation output stage, and the RSC control section includes a speed outer loop, a power outer loop, and a current inner loop.

[0027] The RSC's outer speed loop forms a closed-loop control based on the flywheel reference speed and the actual speed, and outputs a power control reference command; the outer power loop generates a control command based on the deviation between the reference power and the actual power and sends it to the current control loop to achieve dynamic adjustment of the active power channel of the high-inertia energy storage synchronous condenser.

[0028] As a specific implementation method, before constructing the impedance reshaping strategy, the linearized small-signal impedance matrix of the high-inertia energy storage condenser at the PCC point is first constructed from the perspective of the underlying physical electrical equations. Based on the dq coordinates, in the following formula, Δ represents the small-signal quantity of the variable, the superscript "*" represents the per-unit value, and the subscript "ref" represents the reference value.

[0029] like Figure 2 and Figure 3 As shown, the GSC control section of the high-inertia energy storage type synchronous condenser includes a voltage outer loop, a current inner loop, and a modulation output stage, while the RSC control section includes a speed outer loop, a power outer loop, and a current inner loop.

[0030] Combination Figure 2 The GSC employs a vector control strategy based on grid-side voltage d-axis orientation. Its main control objective is to maintain DC bus voltage stability and achieve independent decoupled control of grid-side reactive power. The control section includes an outer loop for DC voltage and an inner loop for grid-side current.

[0031] The specific control instructions are as follows: (1) DC voltage outer loop: The preset DC bus voltage reference value V dcref Compared with the actual value of the collected DC bus voltage V dc The difference is used to obtain the DC voltage deviation.

[0032] (2) Inner loop of grid-side current: The DC voltage deviation is adjusted by the PI of the outer voltage loop to output the reference value of the grid-side d-axis current. i gdref Since the d-axis is oriented, the q-axis current reference value is 0; the deviation between the current reference value and the actual value is calculated. i gdref - i gd and i gqref - i gq .

[0033] (3) Inner loop regulation and dynamic decoupling feedforward compensation: In order to eliminate the dynamic coupling between the d-axis and q-axis and the line impedance voltage drop, a grid-side impedance voltage drop and cross-decoupling compensation term are superimposed at the regulator output. Specifically, this is the grid-side filter resistor. R g The resulting active voltage drop and grid-side inductance cross-decoupling terms manifest as follows: ω s L g .

[0034] (4) Control voltage generation: Combining dynamic decoupling feedforward compensation and current deviation through the PI loop, and the stator voltage d-axis and q-axis components. usd , u sq The final control voltage command of GSC is obtained through synthesis. u gd and u gq .

[0035] Combination Figure 3 RSC employs stator voltage-oriented vector control. Its outer loop includes a speed / active power outer loop and a stator voltage / reactive power outer loop, while the inner loop is the rotor current inner loop.

[0036] The specific control instructions are as follows: (1) Rotational speed outer ring: The reference rotational speed of the high-inertia energy storage type synchronous condenser. ω rref Compared with actual speed ω r The difference is input to the outer loop PI regulator of the speed, and the output is the active power reference value. P ref .

[0037] (2) Power outer loop: The active power reference value P ref and actual value P meas The deviation obtained by subtraction is used to obtain the d-axis current reference value through the power outer loop PI regulator. i rdref ;Reactive power reference value Q ref and actual value Q meas The deviation obtained by subtraction is used to obtain the q-axis current reference value through the power outer loop PI regulator. i rqref .

[0038] (3) Inner current loop: The stator voltage orientation angular velocity determined by the phase-locked loop and position sensor, and the rotor mechanical angular velocity are the slip angular velocities. ω slip The actual three-phase rotor current was collected and transformed using Park to obtain the actual values ​​of the rotor d-axis and q-axis currents. i rd and i rq The difference between the actual value and the reference value yields the current inner loop deviation.

[0039] (4) Inner loop regulation and dynamic decoupling feedforward compensation: To eliminate the strong electromagnetic coupling between the rotor's d and q axes, a feedforward superposition of the machine-side impedance voltage drop and a negative cross-decoupling compensation term is applied at the regulator output. Specifically, this is achieved by comprehensively considering the rotor resistance. Rr The resulting voltage drop and rotor slip frequency ω slip Total leakage flux coefficient of motor L r And rotor equivalent self-inductance and equivalent mutual inductance L m The combined effects of these factors.

[0040] (5) Control voltage generation: final synthesis of RSC final control voltage command u rd and u rq .

[0041] In this embodiment, the GSC is mainly used to maintain the DC bus voltage stability and complete the AC side voltage and current regulation, while the RSC is mainly used to realize the speed, active power, and rotor current control of the high-inertia energy storage synchronous condenser. Since the RSC power outer loop is located outside the fast current inner loop, it can effectively regulate the oscillation of the target frequency band while avoiding the control coupling and stability deterioration problems caused by directly changing the parameters of the current inner loop.

[0042] High-inertia energy storage synchronous condensers, serving as supporting devices connected in parallel to the PCC (Power Control Center), not only provide dynamic reactive power support and short-circuit capacity enhancement, but also offer kinetic energy exchange capabilities that can be rapidly adjusted via the rotor-side power channel. When subsynchronous or supersynchronous oscillations occur at the power station, their kinetic energy exchange capability can be converted into additional damped output oriented towards the target frequency band. The small-signal impedance models of each module of the high-inertia energy storage synchronous condenser are as follows: (1) The small-signal impedance model of the motor module is: ; ; In the formula, u sdq and u rdq These are the d-axis and q-axis components of the stator and rotor voltages of the motor, respectively. i sdq and i rdq These are the d-axis and q-axis components of the stator and rotor currents of the motor, respectively. ω sc and ω r,sc These are the angular velocity and rotor angular velocity of the high-inertia energy storage synchronous condenser, respectively. G ss , G sr 、G sω , G rs , Grr , G rω , G rωr These are the corresponding matrix coefficients.

[0043] (2) The small-signal impedance model of the PLL module is: ; in, G ω These are the coefficients of the phase-locked loop matrix.

[0044] (3) The small-signal impedance model of the filtering module is: ; in, u gdq The d and q components of the GSC output voltage of a high-inertia energy storage synchronous condenser. i gdq For the d and q components of the GSC output current of a high-inertia energy storage type synchronous condenser, G fi , G fω These are the corresponding matrix coefficients.

[0045] (4) The small-signal impedance model of the GSC control module for a high-inertia energy storage synchronous condenser, taking into account the power outer loop and the current inner loop, is as follows: ; ; in, u dc This is the DC bus voltage. G udc , G ig 、G igref , G igω These are the corresponding matrix coefficients.

[0046] (5) The small-signal impedance model of the RSC module of the high-inertia energy storage synchronous condenser, taking into account the outer loop of rotation speed, the outer loop of power, and the inner loop of current, is as follows: ; ; ; ; in, S s =[ P s , Qs ] T , P s , Q s These represent the active power and reactive power output from the stator side of a high-inertia energy storage synchronous condenser, respectively. G ωr , G us 、G is , G s 、G ri , G riref 、G ris , G riω , G riωr These are the corresponding matrix coefficients.

[0047] , These represent the inner-loop current reference values ​​for GSC and RSC in the dq rotating coordinate system, respectively. They are calculated and output by the voltage, power, or speed regulators of the outer loop, serving as the setting reference for the inner-loop current closed-loop control. Δ represents the small-signal quantity of the variable, and the superscript "*" indicates the per-unit value.

[0048] By nesting and eliminating the above control equations, the equivalent output admittance matrix of the high-inertia energy storage synchronous condenser at the PCC point can be obtained: ; in, , These represent the full-order equivalent small-signal admittance matrix and impedance matrix of a high-inertia energy storage synchronous condenser grid-connected system in the dq rotating coordinate system, respectively, and are mathematical models that quantify the electrical impedance characteristics of the synchronous condenser port. Z HIESSC ( s It integrates internal electromagnetic dynamics and multi-loop traditional control of the motor to quantitatively characterize the damping characteristics of a high-inertia energy storage synchronous condenser at the PCC point.

[0049] It should be noted that the matrix coefficients mentioned above all belong to the system matrix characteristic quantities in the full-order dynamic impedance model of the high-inertia energy storage synchronous condenser. These coefficients are the dynamic coefficient matrices of the small-signal impedance / state-space model of the synchronous condenser grid-connected system in the dq rotating coordinate system. These matrix coefficients are based on the basic topology of the doubly-fed induction motor, simultaneously solving the stator voltage equation, rotor voltage equation, stator flux linkage equation, rotor flux linkage equation, and rotor mechanical motion equation. Then, the DC voltage loop / reactive power loop of the GSC, the speed power loop / stator voltage loop of the RSC, and the frequency domain equations and phase-locked loop dynamic differential equations of the inner loop current PI regulator are substituted into the above basic motor equations. The above nonlinear equations are linearized near the steady-state operating point of the system to eliminate intermediate state quantities. The specific determination method of the matrix coefficients is achievable with existing technology, so it will not be described in detail.

[0050] This embodiment improves the interaction between the equivalent impedance of the power station and the grid impedance by reshaping the equivalent output impedance of the PCC point. The phase margin in the target oscillation frequency band is significantly improved, which enhances the phase margin in the target frequency band under weak grid conditions. This strengthens the broadband oscillation suppression capability and operational stability of the grid-connected power station and has better adaptability to different grid strengths and different operating points. It overcomes the shortcomings of existing vibration suppression methods, such as narrow applicable frequency band and poor parameter mobility.

[0051] When establishing the above impedance model, the small signal input-output relationship of each module can be obtained in the dq synchronous rotating coordinate system. Then, the equivalent impedance expression of the station for grid-connected stability analysis can be obtained by model splicing and appropriate order reduction processing.

[0052] For wind turbine groups connected in parallel, the impedance of each unit, along with the impedances of the collector lines, transformer substations, step-up transformers, and PCC network, can be converted to the grid connection point to form the equivalent impedance on the station side for impedance margin analysis.

[0053] In engineering implementation, the aforementioned impedance model can be used for offline tuning of control parameters, or combined with online identification or offline modeling results to determine the center frequency of the bandpass filter, the zero-pole positions of the asymmetric complex lead compensator module, and the gain limiting parameters. For scenarios with significant grid strength variations, multiple parameter tables can be pre-configured to allow switching based on the grid short-circuit ratio or operating mode.

[0054] In this embodiment, in the scenario of a weak power grid, the weak power grid is equivalent to an RLC series network, and the power grid side impedance can be obtained.

[0055] Based on the impedance model constructed above, and combining the amplitude-frequency and phase-frequency characteristics of the equivalent impedance of the power station and the power grid impedance, the dominant oscillation frequency and the target suppression frequency band are identified using the phase margin criterion and the Nyquist criterion; the specific implementation process is as follows: Within the 1–100 Hz frequency band, amplitude-frequency curves of the equivalent impedance of the power station and the grid impedance are plotted respectively. The intersection frequency points of the two curves are potential candidate oscillation frequencies. At each amplitude intersection frequency point, the difference Δφ(ω) between the phase angle of the power station impedance and the phase angle of the grid impedance is calculated. c If |Δφ(ω) c If |>180°, the system is unstable (negative damping) at that frequency point, and this frequency is the dominant oscillation frequency; finally, the target suppression frequency band is determined to be a wideband centered on the dominant oscillation frequency.

[0056] After the phase margin criterion is initially determined, the Nyquist curve of the impedance ratio L(jω) is further plotted to verify whether it encloses the point (-1, j0) in order to strictly confirm the accuracy of the system stability state and oscillation frequency.

[0057] In this embodiment, the target suppression frequency band includes at least one subsynchronous oscillation frequency band and / or at least one supersynchronous oscillation frequency band in the range of 1 to 100 Hz; this frequency band range covers the main oscillation frequencies that may occur in new energy power plants under weak grid conditions, and can effectively cope with broadband oscillation problems.

[0058] S102: Acquire the active power signal of grid-connected renewable energy units or renewable energy power stations; perform bandpass filtering on the active power signal to obtain the subsynchronous and / or supersynchronous oscillation components of the target suppressed frequency band.

[0059] Analysis shows that the active power output of the power station contains characteristic information that can characterize the oscillation state. Therefore, the active power signal of the new energy unit or the new energy power station can be used as the feedback quantity for additional control.

[0060] The reason why this embodiment chooses the active power signal as the additional control input is that when subsynchronous and / or supersynchronous oscillations occur, the energy exchange between the power station and the power grid will be primarily reflected in the active power fluctuations. Compared with simply using local current or voltage as feedback, the active power signal is more likely to reflect the overall oscillation trend after multiple machines are connected in parallel, and is more conducive to implementing unified suppression at the power station level.

[0061] As an optional implementation method, to adapt to different site sizes and communication architectures, the active power signals of grid-connected renewable energy units or renewable energy power stations can be implemented using a single-unit measurement point direct feedback method (i.e., active power signal of a single renewable energy unit), a site main control summary feedback method (i.e., summary active power signal of the renewable energy power station), or a representative unit weighted fusion feedback method (i.e., weighted summation of active power signals of multiple renewable energy units). When using multi-signal fusion, different weights can be assigned to each active power signal according to the unit capacity, access location, oscillation participation degree, or signal quality.

[0062] This technical solution offers flexible signal acquisition methods, allowing for selection of single-unit sampling or station-level sampling based on the scale of the power plant, communication conditions, and measurement point configuration, balancing measurement availability, signal noise immunity, and control timeliness. When using the aggregated active power of the power plant as input, the impact of single-unit measurement noise and local disturbances on control performance can be reduced. When using the equivalent signal obtained by weighting and synthesizing the active power of representative units as input, both real-time signal performance and targeting of critical oscillating units can be considered. Therefore, it offers high flexibility in terms of measurement availability, noise immunity, and communication implementation, making it suitable for widespread application in new energy power plants with different control architectures.

[0063] When the system has a subsynchronous oscillation frequency ω 1 and supersynchronous oscillation frequency ω At 2 o'clock, using the base frequency ω Using 0 as a reference, the DC component and non-target frequency band components are filtered out by bandpass filtering to obtain the subsynchronous and / or supersynchronous oscillation components of the target suppression frequency band, and to ensure that no significant phase lag is introduced in the subsynchronous / supersynchronous interest frequency band.

[0064] The transfer function of the bandpass filter is: ; in, s Let Laplace be a complex variable. ω 0 represents the bandpass center frequency, set at or near the target dominant oscillation frequency; H 0 represents the gain at the bandpass center frequency. Q 0 is the quality factor, used to characterize the bandpass width.

[0065] Specifically, the bandpass center frequency ω 0. Strictly anchored to the dominant oscillation frequency or its geometric center identified by the system's small-signal impedance model, gain H 0 is typically fixed at a value of 1.0, ensuring that signals near the center frequency can pass through with equal amplitude; quality factor Q 0. A dynamic trade-off design is employed to suppress a wide frequency range as needed. As an example, to accurately cover the 40-60Hz oscillation range while completely filtering out steady-state DC components, the quality factor is optimized through engineering. Q 0 takes the value 1.5.

[0066] This bandpass filter has significant attenuation characteristics in the power frequency and high frequency bands, and can automatically block DC bias and non-target frequency band interference. Finally, it outputs only the pure subsynchronous and supersynchronous active power oscillation components located in the target suppression frequency band.

[0067] This embodiment uses the center frequency of the bandpass filter to strictly anchor the geometric center of the identified subsynchronous and / or supersynchronous frequency bands. The selection of the quality factor ensures that no phase shift is introduced within a wide range of oscillation frequencies and that steady-state DC bias is effectively filtered out, thereby accurately extracting the feature components containing oscillation information. The subsynchronous or supersynchronous frequency bands of interest are close to the center frequency, and the phase lead or lag introduced by the bandpass filter itself is very small, thus ensuring that no significant phase lag is introduced within the subsynchronous and / or supersynchronous frequency bands of interest.

[0068] S103: Perform asymmetric complex lead correction on the oscillation component to compensate for insufficient phase margin.

[0069] In this embodiment, after extracting the oscillation component, an asymmetric complex lead correction module is set up to address the phase lag and wideband negative damping issues present in the system at the target frequency point, in order to compensate for insufficient phase margin and delay phase fall-off in other frequency bands.

[0070] The transfer function of the asymmetric complex lead compensator module is: ; in, ξ z A smaller damping ratio is used to provide phase lead compensation near the resonance point; ξ p A larger damping ratio is used to delay phase fall-off and maintain phase margin over a wider frequency band, and ξ z < ξ p ; ω z The complex zero frequency is set near the dominant oscillation frequency. ω p The complex pole frequency is set far from the dominant oscillation frequency. Complex zeros are used to provide the desired phase lead near the target frequency, and complex poles are used to suppress excessive amplification in non-target frequency bands and maintain control stability over a wide bandwidth.

[0071] In this embodiment, the asymmetric complex lead correction module provides the required phase lead by configuring a weakly damped zero near the target frequency point, while effectively avoiding gain divergence in non-target frequency bands by configuring a high-frequency strong damped pole, so that the system maintains sufficient stability margin in the range of 1 to 100 Hz, compensates for insufficient phase margin of the system, and delays phase fall-off in other frequency bands.

[0072] Asymmetric complex lead compensation compensates for the severe phase lag of the original system under weak grid conditions. It can actively provide accurate phase lead compensation in the negative damping region to quickly fill the phase margin lost by the system, and can also delay phase fallback in other frequency bands far from the dominant frequency.

[0073] In this embodiment, the center frequency, quality factor, and zero-pole positions of the asymmetric complex lead correction module of the bandpass filter are tuned based on the dominant oscillation frequency of the grid-connected system, the grid short-circuit ratio, and the capacity margin.

[0074] Bandpass filter center frequency setting ω 0 = 2π × 50 ≈ 314.1 rad / s, to ensure that the impedance reshaping control signal can accurately lock the current oscillation frequency, so that the damping gain of the filter in this frequency band reaches the maximum, while effectively filtering out power frequency and other unrelated frequency band components.

[0075] The quality factor is a compromise based on the oscillation bandwidth determined by the grid short-circuit ratio. In this embodiment, a value of 1.5 is determined for the potential oscillation frequency band of 40-60Hz. This value ensures that the filter has a sufficiently wide passband, enabling the control system to not only effectively suppress sub / supersynchronous oscillations in this frequency band, but also improve the adaptability and robustness of the control strategy.

[0076] Asymmetric complex lead compensator configuration with a pair of complex zero frequencies ω z =2π×35 rad / s, minimum damping ratio ξ z =0.10, these weakly damped zeros will fill the negative damping at the target frequency; configure a pair of high-frequency complex poles. ω p =2π×90rad / s, maximum damping ratio ξ z =0.80, the strong damping pole can effectively avoid high-frequency gain divergence in the region above 100Hz.

[0077] By selecting the values ​​of the above core parameters, it is ensured that the control parameters match the system operating conditions. For scenarios with large variations in grid strength, multiple sets of parameter tables can be pre-configured to switch according to the grid short-circuit ratio or operating mode, thereby improving the adaptability and robustness of the control strategy.

[0078] S104: After phase compensation, the signal is shaped and limited for safety, and then injected as an additional control signal into the power outer loop of the rotor-side converter of the high-inertia energy storage type synchronous condenser to form an additional power deviation. S105: After the deviation is adjusted by PI, the rotor side current reference value is output, which in turn forms a damping power on the stator side that is opposite to the oscillation component, so as to reshape the equivalent output impedance of the common coupling point and thus suppress the subsynchronous and / or supersynchronous oscillation of the new energy power station.

[0079] In this embodiment, the phase-compensated signal enters the gain and limiting module, and the negative gain K is used to shape the amplitude of the control signal. The safe limiting is used to suppress the converter overmodulation that may occur under large disturbance conditions, and the power fluctuation signal is shaped into an additional control signal that is sufficient to change the output characteristics of RSC.

[0080] The additional control signal is injected into the power outer loop of the rotor-side converter of the high-inertia energy storage synchronous condenser. Since the RSC power outer loop is located outside the fast current inner loop, it can effectively regulate the oscillation of the target frequency band and avoid the saturation and robustness reduction problems caused by directly implementing high gain compensation in the fast current loop. It also avoids the control coupling and stability deterioration problems caused by directly changing the parameters of the current inner loop, and has good engineering feasibility.

[0081] Figure 4 The additional control signal Δ is shown. P add A schematic diagram of the injected RSC power outer loop, and the additional control signal Δ generated in step S104. P add The previous power outer loop deviation is superimposed in a feedforward form. P ref - P meas The additional power deviation after reshaping is superimposed at the node. P em =( P ref - P meas ±Δ P add ).

[0082] Additional power deviation P em The input is sent to the outer loop PI regulator on the machine side. Its output, based on the original steady-state command, is directly injected with dynamic fluctuation components corresponding to the oscillation frequency band, resulting in an output rotor inner loop current reference value containing oscillation suppression characteristics. The final output rotor control voltage gains additional damping characteristics, causing the stator terminal of the synchronous condenser to generate a positively damped signal at the PCC point that is out of phase with the original system's broadband oscillation power component.

[0083] In small-signal model processing, the original rotor current reference value is Δ i rdqref = G s (Δ S sref -Δ S s After impedance reshaping Δ i rdqref = Gs (Δ S sref -Δ S s +Δ P add This is equivalent to introducing a wind turbine power signal. Traditionally, grid-connected synchronous condensers and new energy wind farms are independent of each other in the control link. This embodiment, by collecting wind turbine power and injecting it into the rotor side of the synchronous condenser after impedance reshaping, breaks the independent boundary between the two control systems at the control level, thereby enabling the high-inertia energy storage synchronous condenser to reshape its own impedance at the PCC point and thus suppress the oscillation of the farm.

[0084] As a further implementation, the injection location of the additional control signal can be configured according to the existing controller structure. For example, it can be superimposed on the active power reference value terminal and the active power feedback value terminal of the high-inertia energy storage synchronous condenser, or it can be weighted separately and then applied to both simultaneously, so as to balance the control response speed and system robustness.

[0085] When injected into the active power reference value, it facilitates the formation of a clear power correction command. When injected into the active power feedback value, it helps to maintain the original reference channel structure. When weighted injection is performed on both ends, a balance can be achieved between response speed and disturbance rejection stability.

[0086] In this embodiment, the active power signal output by the new energy unit or new energy power station is introduced into the RSC control loop of the high-inertia energy storage synchronous condenser. By utilizing the kinetic energy buffering capability of the high-inertia energy storage synchronous condenser and the adjustable characteristics of the rotor-side control channel, the high-inertia energy storage synchronous condenser outputs damping power that is out of phase with the oscillation component at the common coupling point. From the perspective of impedance, this process is equivalent to reshaping the output impedance at the PCC point, thereby weakening the negative damping characteristics of the original system.

[0087] In this embodiment, after introducing additional control signals, a small-signal impedance model for a high-inertia energy storage synchronous condenser connected to the grid, taking into account the impedance reshaping process, is established. The Nyquist criterion combined with a phase margin criterion based on impedance amplitude-frequency characteristics is used to analyze system stability. The analysis shows that after implementing impedance reshaping, the interaction between the equivalent impedance of the power station and the grid impedance is improved, the phase margin within the target oscillation frequency band is increased, and the risk of subsynchronous and / or supersynchronous oscillations at the new energy power station is reduced.

[0088] Therefore, this embodiment does not passively avoid oscillations by changing the original control parameters of the new energy unit, but actively improves the equivalent output impedance of the PCC point by constructing an additional damping channel oriented towards the target frequency band on the high-inertia energy storage synchronous condenser side. Therefore, it has better adaptability to different grid strengths and different operating points.

[0089] As a further optional implementation, to further reduce the impact of additional control switching on the original power setpoint, a slow start and slow stop mechanism can be set at the output of the additional control. When the amplitude, peak spectral value, or equivalent energy index of the subsynchronous and / or supersynchronous oscillation components in the target suppression frequency band exceeds a preset start threshold, the aforementioned oscillation suppression method based on impedance reshaping of a high-inertia energy storage type synchronous condenser is triggered. When the amplitude, peak spectral value, or equivalent energy index of the subsynchronous and / or supersynchronous oscillation components in the target suppression frequency band decreases to below the preset start threshold, the output of the additional control signal is gradually reduced according to a preset slope to avoid secondary disturbances to the original power regulation channel caused by the moment the controller is put into and taken out.

[0090] Specifically, the equivalent energy index is used to characterize the cumulative energy distribution of oscillation disturbance signals within the target suppression frequency band. In this embodiment, the equivalent energy index is calculated by performing root mean square (RMS) calculation on the power oscillation components within the target suppression frequency band; or by performing spectral analysis on the power oscillation components and integrating the power spectral density within the 1~100Hz target frequency band. The physical significance of introducing the equivalent energy index lies in its ability to more accurately reflect the overall severity of sub / supersynchronous multimodal coupled oscillations through a multi-band energy accumulation mechanism, thereby improving the stability and robustness of impedance reshaping control.

[0091] This oscillation triggering and exiting logic can reduce the impact of additional control on normal steady-state operation, avoid secondary disturbances caused by the moment the controller is put into operation and taken out of operation, and improve the stability of system operation.

[0092] The core of this embodiment is not simply to increase the control gain of a certain control link, but to construct a closed-loop vibration suppression link from oscillation identification, signal extraction, phase correction, power injection to impedance reshaping, so that the high-inertia energy storage synchronous condenser can directionally adjust the real part and phase characteristics of the equivalent impedance of the common coupling point without changing the main circuit hardware topology of the main equipment.

[0093] This embodiment utilizes the characteristics of the high-inertia energy storage type synchronous condenser rotor-side converter power outer loop, which has both adjustable active power channels and good engineering accessibility. The active power oscillation component of the station is used as feedback information. After preprocessing, phase compensation and gain limiting, it forms an additional control quantity, which is then converted into an execution signal that can output anti-phase damping power at the common coupling point through the RSC power outer loop, thereby changing the equivalent impedance characteristics of the station in the target frequency band.

[0094] The following time-domain simulation is used to verify the method for suppressing subsynchronous and / or supersynchronous oscillations of new energy power stations based on impedance reshaping of high-inertia energy storage type synchronous condensers described in this embodiment.

[0095] Taking a wind farm system with high-inertia energy storage synchronous condensers as an example, its grid topology is as follows: Figure 5 As shown. Figure 5 The system consists of a DFIG cluster (1.5MW each), a high-inertia energy storage synchronous condenser (11MW), and an external power grid (35kV). The stators of each wind turbine in the DFIG cluster are connected in parallel to the PCC point via corresponding 0.69kV / 35kV transformers. The high-inertia energy storage synchronous condenser is constructed by coaxially connecting a DFIM and a high-inertia flywheel, and its stator is connected in parallel to the PCC point via a corresponding 10.5kV / 35kV transformer. V dc This indicates the DC bus voltage between the internal connection RSC and GSC of the high-inertia energy storage synchronous condenser. R grid , L grid and C grid The equivalent line resistance, equivalent line inductance, and equivalent ground / phase capacitance of the external power grid, used to quantitatively and equivalently characterize the transmission line and the external power grid respectively, jointly determine the short-circuit ratio and grid strength at the grid connection point. Specifically... R grid =0.026Ω L grid =0.013H, C grid =1.54×10 -5 F.

[0096] Specifically, the power station consists of high-inertia energy storage synchronous condensers and 60 doubly-fed induction generators (DFIGs), each DFIG with a rated power of 1.5MW, and the high-inertia energy storage synchronous condensers with a rated power of 11MW; the equivalent grid parameters are as follows: R grid =0.026Ω L grid =0.013H, C grid =1.54×10 -5 F; The high-inertia energy storage type synchronous condenser and DFIG are connected in parallel to the 35kV bus via 10.5 / 35kV and 0.69 / 35kV step-up transformers, respectively.

[0097] Based on the above parameters, the dq-domain small-signal impedances of high-inertia energy storage synchronous condensers and wind farms are theoretically transformed to obtain an equivalent reduced-order positive-sequence impedance model considering the influence of interconnected systems, such as... Figure 6 The black solid line in the middle shows the curve. For comparison, the measured curve was obtained through impedance frequency sweep in the time-domain simulation, as shown below. Figure 6The black "+" curves in the middle show that the two curves largely overlap, indicating that the established small-signal theoretical impedance model can accurately reflect the impedance characteristics of the actual grid-connected system.

[0098] Figure 6 The black dashed line represents the equivalent impedance curve of the power grid. According to the phase margin criterion based on impedance amplitude-frequency characteristics, before impedance reshaping, the equivalent impedance of the power station... Z eqp With grid impedance Z g The amplitude curves intersect near 40Hz and 60Hz, and the phase difference at the intersection exceeds 180°, indicating a risk of system instability.

[0099] Time-domain simulation was performed using Matlab / Simulink. The system started in a stable state, and at t = 0.5s, it transitioned from a strong power grid to a weak power grid. Figure 7 Active power signal of the wind turbine P WT The waveform shows that the system oscillates continuously from t=0.5s.

[0100] The time-domain simulation results P WT Perform FFT analysis, the spectrum is as follows Figure 8 As shown in the figure. The results indicate that the system exhibits subsynchronous / supersynchronous oscillation components at 40 Hz and 60 Hz, consistent with the impedance stability analysis results.

[0101] To address the aforementioned oscillation characteristics, impedance reshaping control is implemented on the outer loop of the RSC power of the high-inertia energy storage synchronous condenser. The specific process is as follows: Step 1: Acquire the output active power signal of the wind turbine or wind farm. P WT The oscillation components are then subjected to synchronous rotation coordinate transformation or equivalent frequency shift processing to obtain the corresponding subsynchronous / supersynchronous characteristic components.

[0102] Step 2: Set up a preprocessing module, using a bandpass filter to remove DC components and low-frequency interference, ensuring no significant phase lag is introduced within the target oscillation frequency band. The center frequency of the bandpass filter is... ω 0. Strictly anchor the identified sub- and / or supersynchronous frequency band geometric center, and set... ω 0 = 2π × 50 ≈ 314.1 rad / s. Quality factor Q 0 is the core of extraction accuracy, ensuring accuracy across a wide range of 40. This embodiment takes the following characteristics: It does not introduce phase shift within the 60Hz range and can effectively filter out steady-state DC bias. Q 0 = 1.5. Furthermore, the passband center gain is fixed as... H0 = 1.0.

[0103] As an example, the signal acquisition module on the site side acquires the total output active power signal of the wind farm. P WT The active power signal is transformed to the dq coordinate system via Park transform and then fed into a preprocessing module consisting of a bandpass filter. When the grid-connected system experiences wideband oscillations, the output power is superimposed with subsynchronous (e.g., 40Hz), supersynchronous (e.g., 60Hz) disturbances, and a steady-state DC component. This filter exhibits significant attenuation characteristics in the power frequency and high-frequency bands, automatically blocking DC bias and non-target frequency band interference, ultimately outputting only pure subsynchronous and supersynchronous active power oscillation components located within the target suppression frequency band.

[0104] Step 3: To address the phase lag and negative damping characteristics of the system around 40 Hz and 60 Hz, an asymmetric complex lead compensation module is installed to compensate for insufficient system phase margin and delay phase fallback in non-target frequency bands, maintaining sufficient stability margin within the 1–100 Hz range. Calculations show that the system requires approximately 50° of field-supplied phase lead at 40 Hz; therefore, to meet this requirement, this embodiment configures a pair of complex zero-frequency components, such as… ω z =2π×35 rad / s, minimum damping ratio ξ z =0.10, these weakly damped zeros will fill the negative damping at the target frequency; configure a pair of high-frequency complex poles. ω p =2π×90rad / s, maximum damping ratio ξ z =0.80, the strong damping pole can effectively avoid high-frequency gain divergence in the region above 100Hz.

[0105] Step 4: The phase-compensated signal enters the gain and limiting module, which shapes the power fluctuation signal into an additional control signal sufficient to change the RSC output characteristics, and avoids converter overmodulation under grid faults or severe disturbances. This embodiment uses... K = -5, set the extreme value of the saturation limiting function to ±0.12pu.

[0106] Step 5, process the additional control signal Δ P add The RSC power outer loop of a high-inertia energy storage type synchronous condenser is introduced and superimposed on the active power reference value terminal and / or active power feedback value terminal; the additional control signal is PI regulated to form the rotor side current reference value, and then forms the damping power on the stator side that is opposite to the grid oscillation component.

[0107] To introduce additional control signal Δ Padd Impedance scanning tests were conducted on the grid-connected systems of high-inertia energy storage synchronous condensers and wind farms. Continuous frequency scanning was performed within the 1–100 Hz frequency range to obtain the equivalent impedance spectra of the reshaped power station and the grid. Figure 9 As shown. Figure 9 The black "+" curve represents the equivalent impedance curve of the power station obtained from time-domain simulation frequency sweep, while the black dashed line represents the equivalent impedance curve of the power grid. Analysis shows that after impedance reshaping, the phase margin within the target frequency band of the system is significantly improved, and system stability is enhanced.

[0108] Time-domain simulations were performed using Matlab / Simulink. The system transitioned from a strong grid to a weak grid at t=0.5s, and at t=2s, the high-inertia energy storage synchronous condenser's power outer loop impedance reshaping control was implemented. Figure 10 Active power signal of the wind turbine P WT The waveform shows that the oscillations decayed rapidly after t=2s, and the system returned to stability.

[0109] After impedance reshaping P WT Perform FFT analysis, the spectrum is as follows Figure 11 As shown in the figure. The results indicate that the subsynchronous / supersynchronous oscillation components of the system are effectively suppressed in the target frequency band.

[0110] In summary, after implementing the RSC power outer loop impedance reshaping control based on high-inertia energy storage synchronous condensers, the system oscillation amplitude significantly decreased and returned to stable operation, indicating that the control method proposed in this embodiment can effectively suppress the subsynchronous and / or supersynchronous oscillations of the new energy power station grid-connected system.

[0111] This embodiment fully utilizes the kinetic energy buffering capability of high-inertia energy storage synchronous condensers and the reactive power support capability of synchronous condensers. By constructing an additional damping channel oriented towards the target frequency band on the high-inertia energy storage synchronous condenser side, it actively improves the equivalent output impedance of the PCC point. It can provide energy support and oscillation damping for the system without adding dedicated damping compensation hardware or changing the main circuit hardware topology of the main equipment. It can be implemented based on the existing high-inertia energy storage synchronous condenser control platform. In principle, it does not require changes to the main wiring and main power circuit structure of the power station. Therefore, it has good applicability for retrofitting existing new energy power stations and can balance technical integrity and economic efficiency in engineering implementation.

[0112] Example 2 In one or more embodiments, an oscillation suppression system based on impedance reshaping of a high-inertia energy storage type phase shifter is disclosed, specifically including: The target suppression frequency band determination module is configured to combine and analyze the small-signal impedance models of high-inertia energy storage synchronous condensers and grid-connected new energy power stations to identify the target suppression frequency band. The signal acquisition module is configured to acquire the active power signal of grid-connected renewable energy units or renewable energy power plants; The preprocessing module is configured to perform bandpass filtering on the active power signal to obtain the subsynchronous and / or supersynchronous oscillation components of the target suppressed frequency band; The phase compensation module is configured to perform asymmetric complex lead correction on the oscillation component to compensate for insufficient phase margin. The gain limiting module is configured to perform amplitude shaping and safety limiting on the phase-compensated signal; The control injection module is configured to inject the limited signal as an additional control signal into the power outer loop of the rotor-side converter of the high-inertia energy storage type synchronous condenser. The execution module is configured to generate an additional power deviation based on the additional control signal; the deviation is PI-regulated and outputs a rotor-side current reference value, thereby generating a damping power on the stator side that is opposite to the oscillation component, so as to reshape the equivalent output impedance of the common coupling point and thus suppress subsynchronous and / or supersynchronous oscillations of the new energy power station.

[0113] The signal acquisition module is responsible for acquiring the active power signal of the new energy unit or new energy power station and outputting it to the preprocessing module; the preprocessing module extracts the oscillation component in the target frequency band; the phase compensation module completes the required phase lead correction; the gain limiting module generates an additional control signal that meets the execution constraints; the control injection module introduces the additional control signal into the RSC power outer loop; the execution module outputs damping power that is out of phase with the oscillation component at the PCC according to the injected control command.

[0114] Each module can be integrated into the high-inertia energy storage synchronous condenser controller, or it can be distributed between the main control system of the site and the high-inertia energy storage synchronous condenser controller according to the site control architecture, so as to meet the implementation requirements of different engineering scenarios.

[0115] The system can be deployed in a centralized manner, where the main control unit at the site completes signal aggregation, target frequency band identification, and additional control generation, and then sends the data to the high-inertia energy storage synchronous condenser controller for execution; or it can be deployed in an embedded manner, where the relevant algorithms are directly integrated into the high-inertia energy storage synchronous condenser controller, thereby reducing communication links within the site and improving control real-time performance.

[0116] For project implementation, each functional module can be implemented using digital signal processors, programmable logic devices, industrial controllers, or combinations thereof, and can work collaboratively with existing new energy power station monitoring systems, protection systems, and high-inertia energy storage synchronous condenser control systems. Since it does not involve changes to the main circuit topology, it offers good convenience for engineering modifications.

[0117] This embodiment employs a modular control structure encompassing signal acquisition, preprocessing, phase compensation, gain limiting, and control injection. The parameters have clear physical meanings, facilitating integration into existing high-inertia energy storage synchronous condenser control platforms. It can be tuned for different grid strengths, operating points, and station sizes, exhibiting good engineering portability. It can be used for offline control parameter tuning or combined with online identification or offline modeling results. For scenarios with significant grid strength variations, multiple parameter tables can be pre-configured for switching based on grid short-circuit ratios or operating modes. The system can be implemented using existing high-inertia energy storage synchronous condenser control platforms, and in principle, requires no changes to the station's main wiring and main power circuit structure. Therefore, it has good applicability for retrofitting existing renewable energy stations, balancing the technical integrity required by the authorized text with economic efficiency in engineering implementation.

[0118] Example 3 In one or more embodiments, a terminal device is disclosed, comprising a processor and a memory, wherein the processor is used to implement instructions; and the memory is used to store multiple instructions adapted to be loaded by the processor and executed by the processor for oscillation suppression method based on impedance reshaping of a high-inertia energy storage type phase shifter as described in Embodiment 1.

[0119] It should be understood that in this embodiment, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0120] Memory may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of memory may also include non-volatile random access memory. For example, memory may also store information about the device type.

[0121] In the implementation process, each step of the above method can be completed by the integrated logic circuits in the processor hardware or by software instructions.

[0122] Example 4 In one or more embodiments, a computer-readable storage medium is disclosed, wherein a plurality of instructions are stored, the instructions being adapted to be loaded by a processor of a terminal device and executed by the oscillation suppression method based on impedance reshaping of a high-inertia energy storage type phase shifter as described in Embodiment 1.

[0123] Although the present invention has been described above in conjunction with a DFIG-containing wind farm, the technical concept of the present invention is not limited to this specific object. For new energy power farms with similar active power oscillation characteristics and equipped with high-inertia energy storage synchronous condensers or equivalent high-inertia controllable support devices, such as full-power converter wind farms, photovoltaic power farms, or wind-solar-storage combined power farms, the corresponding impedance reshaping and oscillation suppression can also be implemented with reference to the ideas of the present invention.

Claims

1. A method for suppressing oscillations based on impedance reshaping of a high-inertia energy storage phase shifter, characterized in that, include: By combining the small-signal impedance model of high-inertia energy storage synchronous condenser with that of grid-connected new energy power station, the target suppression frequency band can be identified. Acquire the active power signal of the grid-connected renewable energy unit or renewable energy power station; perform bandpass filtering on the active power signal to obtain the subsynchronous and / or supersynchronous oscillation components of the target suppressed frequency band; The oscillation component is subjected to asymmetric complex lead correction to compensate for insufficient phase margin; After phase compensation, the signal is shaped and limited for safety, and then injected as an additional control signal into the power outer loop of the rotor-side converter of the high-inertia energy storage type synchronous condenser to form an additional power deviation. The deviation is adjusted by a PI controller to output a reference value for the rotor-side current, which in turn generates damping power on the stator side that is opposite to the oscillation component. This power is used to reshape the equivalent output impedance of the common coupling point, thereby suppressing subsynchronous and / or supersynchronous oscillations in new energy power plants.

2. The oscillation suppression method based on impedance reshaping of a high-inertia energy storage phase shifter as described in claim 1, characterized in that, By combining the high-inertia energy storage synchronous condenser with the small-signal impedance model of grid-connected renewable energy power stations for analysis, the target suppression frequency band is identified, specifically: A small-signal impedance model of the main circuit and control loop of a high-inertia energy storage synchronous condenser is established to obtain the equivalent impedance on the station side. By combining the equivalent impedance on the station side and the equivalent impedance on the grid side, the amplitude-frequency crossover point is identified, and at each crossover frequency point, the difference between the phase angle of the station impedance and the phase angle of the grid impedance is calculated. The dominant oscillation frequency is identified by the phase margin criterion, and the target suppression frequency band is determined. The accuracy of the dominant oscillation frequency is further verified by the Nyquist criterion.

3. The oscillation suppression method based on impedance reshaping of a high-inertia energy storage phase shifter as described in claim 2, characterized in that, The target suppression frequency band includes at least one subsynchronous oscillation frequency band and / or at least one supersynchronous oscillation frequency band in the range of 1 to 100 Hz.

4. The oscillation suppression method based on impedance reshaping of a high-inertia energy storage phase shifter as described in claim 1, characterized in that, The active power signal of the grid-connected renewable energy generating unit or renewable energy power station specifically refers to: the active power signal of a single renewable energy generating unit, the aggregated active power signal of a renewable energy power station, or the equivalent active power signal obtained by weighted summation of the active power signals of multiple renewable energy generating units.

5. The oscillation suppression method based on impedance reshaping of a high-inertia energy storage phase shifter as described in claim 1, characterized in that, The active power signal is bandpass filtered, and the transfer function of the bandpass filter is: ； in, s Let Laplace be a complex variable. ω 0 is the bandpass center frequency, set at or near the dominant oscillation frequency; H 0 represents the gain at the bandpass center frequency. Q 0 is the quality factor, used to characterize the bandpass width.

6. The oscillation suppression method based on impedance reshaping of a high-inertia energy storage phase shifter as described in claim 1, characterized in that, The oscillation component is subjected to asymmetric complex lead compensation. The transfer function of the asymmetric complex lead compensation module is: ； in, ξ z This is the first damping ratio, used to provide phase lead compensation near the resonance point; ξ p This is the second damping ratio, used to delay phase fall-off and maintain phase margin over a wider frequency band. ξ z < ξ p ; ω z The complex zero frequency is set near the dominant oscillation frequency. ω p The frequency of the complex poles is set far from the dominant oscillation frequency.

7. The oscillation suppression method based on impedance reshaping of a high-inertia energy storage phase shifter as described in claim 1, characterized in that, When the amplitude, peak value of the spectral value or equivalent energy index of the subsynchronous and / or supersynchronous oscillation component in the target suppression frequency band exceeds the preset start-up threshold, the oscillation suppression method based on impedance reshaping of a high-inertia energy storage type phase shifter as described in any one of claims 1-6 is triggered. When the amplitude, peak value or equivalent energy index of the subsynchronous and / or supersynchronous oscillation components in the target suppression frequency band decreases to below the preset start-up threshold, the output of the additional control signal is gradually reduced according to the preset slope to reduce the disturbance of the control switching on the original power regulation channel.

8. An oscillation suppression system based on impedance reshaping of a high-inertia energy storage type phase shifter, characterized in that, include: The target suppression frequency band determination module is configured to combine and analyze the small-signal impedance models of high-inertia energy storage synchronous condensers and grid-connected new energy power stations to identify the target suppression frequency band. The signal acquisition module is configured to acquire the active power signal of grid-connected renewable energy units or renewable energy power plants; The preprocessing module is configured to perform bandpass filtering on the active power signal to obtain the subsynchronous and / or supersynchronous oscillation components of the target suppressed frequency band; The phase compensation module is configured to perform asymmetric complex lead correction on the oscillation component to compensate for insufficient phase margin. The gain limiting module is configured to perform amplitude shaping and safety limiting on the phase-compensated signal; The control injection module is configured to inject the limited signal as an additional control signal into the power outer loop of the rotor-side converter of the high-inertia energy storage type synchronous condenser. The execution module is configured to generate an additional power deviation based on the additional control signal; the deviation is PI-regulated and outputs a rotor-side current reference value, thereby generating a damping power on the stator side that is opposite to the oscillation component, so as to reshape the equivalent output impedance of the common coupling point and thus suppress subsynchronous and / or supersynchronous oscillations of the new energy power station.

9. A terminal device comprising a processor and a memory, the processor for implementing instructions; the memory for storing multiple instructions, characterized in that, The instructions are adapted to be loaded by a processor and executed by the oscillation suppression method based on impedance reshaping of a high-inertia energy storage type synchronous condenser as described in any one of claims 1-7.

10. A computer-readable storage medium storing a plurality of instructions, characterized in that, The instructions are adapted to be loaded by the processor of the terminal device and executed by the oscillation suppression method based on impedance reshaping of a high-inertia energy storage type synchronous condenser as described in any one of claims 1-7.

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