System for suppressing subsynchronous oscillation of doubly-fed grid-connected system

Abstract

The invention relates to the technical field of subsynchronous oscillation suppression, in particular to a system for suppressing subsynchronous oscillation of a doubly-fed grid-connected system, and the system comprises a doubly-fed generator module which is used for converting wind power into electric energy; the subsynchronous oscillation spectrum disturbance module specifically comprises a current disturbance generation unit and a phase decoupling optimization unit; and the multi-frequency domain decomposition and absorption module specifically comprises a frequency spectrum decomposition unit and a self-adaptive absorption unit. According to the invention, the current disturbance generation unit actively injects a low-power and non-linearly distributed current disturbance signal, dynamically destroys the coherence of the subsynchronous oscillation signal, and combines the spectrum decomposition unit to accurately identify the subsynchronous oscillation dominant frequency and the harmonic component thereof, thereby refining the distribution analysis of the oscillation energy, and improving the accuracy of the subsynchronous oscillation. The high-precision target positioning capability is provided for the oscillation suppression strategy, the multi-level oscillation suppression from active disturbance to precise control is realized through the cooperative operation of the two, and the stability and adaptability of the system under the complex power grid condition are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of subsynchronous oscillation suppression, and in particular to a system for suppressing subsynchronous oscillation of a double-fed grid-connected system. Background Art

[0002] With the continuous expansion of wind power grid-connected scale, doubly-fed generators (DFIG) are widely used in wind farms due to their good variable speed constant frequency characteristics and high efficiency. However, with the increasing complexity of wind power grid-connected systems, subsynchronous oscillation problems have gradually become an important factor restricting system stability. Subsynchronous oscillation is a low-frequency oscillation phenomenon, usually occurring in the range of 10Hz to 50Hz. Its main causes include energy coupling between generators and grids, weak grid characteristics, and output fluctuations of wind farms with high penetration rates. Subsynchronous oscillation may cause equipment fatigue, reduced power generation efficiency, and even lead to system instability.

[0003] The current mainstream technologies for suppressing subsynchronous oscillations mainly focus on the following aspects: Damping control technology: The system is compensated by adding a damping controller to weaken the oscillation, but this method requires precise design of the damping coefficient and has poor adaptability to dynamic loads and grid disturbances.

[0004] Energy storage technology: Absorb or release energy through battery storage, supercapacitors and other devices to alleviate the impact of oscillations, but its frequency selectivity is poor and it is difficult to accurately control specific subsynchronous frequencies. Summary of the invention

[0005] The invention provides a system for suppressing subsynchronous oscillation of a double-fed grid-connected system.

[0006] A system for suppressing subsynchronous oscillation of a double-fed grid-connected system, comprising: A double-fed generator module, used to convert wind power into electrical energy, comprises a stator side and a rotor side, wherein the stator side is directly connected to the grid, and the rotor side is connected to the grid via a grid-connected inverter; The sub-synchronous oscillation spectrum disturbance module specifically includes: The current disturbance generating unit injects low-power, nonlinearly distributed current disturbance signals through the grid-connected inverter, destroying the coherence of the subsynchronous oscillation signal, forming random fluctuations, and suppressing the accumulation of oscillation energy; The phase decoupling optimization unit dynamically adjusts the phase relationship between the subsynchronous oscillation signal and the injected current disturbance signal to ensure destructive interference between the disturbance signal and the oscillation frequency, weaken the energy resonance effect, and achieve the optimal oscillation disturbance effect; Multi-frequency domain decomposition and absorption module, including: The spectrum decomposition unit uses the composite Hilbert-Huang transform technique to decompose the subsynchronous oscillation signal into multiple frequency domain components and identify the energy distribution of the subsynchronous oscillation frequency and its harmonic components; The adaptive absorption unit, which consists of a self-tuning circuit and a fast energy storage device, absorbs the key frequency components of the subsynchronous oscillation in real time according to the results of the spectrum decomposition unit, and releases the absorbed energy through reactive power compensation to avoid interference with other frequency components of the power grid.

[0007] Optionally, the current disturbance generating unit specifically includes: Oscillation monitoring subunit, real-time monitoring of the frequency of the subsynchronous oscillation signal , Amplitude ; A signal generating subunit, based on the output data of the oscillation monitoring subunit, generates a low-power, nonlinearly distributed current disturbance signal using a pseudo-random signal generator, wherein the disturbance signal has dynamically changing frequency, phase and amplitude characteristics; The inverter modulation subunit adopts pulse width modulation (PWM) technology to superimpose and inject the pseudo-random current disturbance signal into the output current of the grid-connected inverter.

[0008] Optionally, the pseudo-random current disturbance signal generation in the signal generation subunit is expressed as: ,in, is the current disturbance signal injected into the grid, is the amplitude of the current disturbance signal, which is lower than the subsynchronous oscillation signal amplitude (lower than 0.1 times the subsynchronous signal amplitude), is the frequency of the current disturbance signal, which is obtained by combining the pseudo-random number generator with the subsynchronous oscillation signal frequency The frequency distribution is in the nonlinear range. is the random phase of the disturbance signal, uniformly distributed between 0 and , is Gaussian white noise, representing random disturbance, satisfying , is the frequency number of the disturbance signal, , with a subsynchronous oscillation frequency Based on random offset Generate a disturbance signal frequency nearby, with a random offset range of Sure, Dynamically adjust according to the frequency change characteristics of the sub-synchronous oscillation signal.

[0009] Optionally, the signal generation subunit further includes a nonlinear distribution relationship between the control amplitude and the frequency, which is expressed as: ,in, is the proportionality factor, which determines the maximum disturbance amplitude, It is the frequency attenuation factor, which controls the rapid decay of the disturbance signal amplitude as the frequency increases.

[0010] Optionally, the pulse width modulation technology injects a disturbance signal into the output current of the grid-connected inverter, and the output current of the grid-connected inverter is expressed as: ,in, is the output current of the grid-connected inverter, is the original grid output current, is the current disturbance signal; The pulse width modulation technique modulation is expressed as: ,in, It is the output voltage signal of the grid-connected inverter after PWM modulation. is the DC bus voltage of the grid-connected inverter, is the inverter's carrier frequency (usually in the kilohertz range), is the sign function, used for PWM modulation.

[0011] Optionally, the phase decoupling optimization unit specifically includes: Phase difference calculation formula: ,in, is the phase difference between the current disturbance signal and the target subsynchronous oscillation signal, is the phase of the current disturbance signal, is the phase of the target subsynchronous oscillation signal; The phase relationship is dynamically adjusted as follows: ,in, is the adjusted current disturbance signal phase, is the phase adjustment gain factor, which controls the rate of phase adjustment, .

[0012] Optionally, the spectrum decomposition unit specifically includes: Empirical Mode Decomposition Subunit: Subsynchronous Oscillation Signals Decompose and generate a set of intrinsic mode functions (IMFs) , the following conditions are met: ,in, is the number of IMF components, indicating the number of oscillation modes obtained by signal decomposition, It is The intrinsic mode function represents the local oscillation characteristics of the signal. is the residual component of the signal, including the low-frequency trend term; Hilbert transform subunit: For each Perform Hilbert transform to generate its instantaneous frequency and the instantaneous amplitude : ,in, is the instantaneous amplitude of the IMF component, indicating the change of signal strength over time, is the instantaneous frequency of the IMF component, which represents the local oscillation frequency of the signal, is the instantaneous phase, which indicates the change of signal phase over time. represents a small increment in the time dimension, represents the Hilbert transform operation; Energy distribution calculation subunit: combined with instantaneous frequency and the instantaneous amplitude , calculate the energy distribution of each frequency component : ,in, is the target frequency The corresponding energy reflects the intensity of a specific frequency component. are the start and end time of the analysis period, is the Dirac function, which is used to extract specific frequency components The energy It is the square of the instantaneous amplitude and represents the local intensity of the signal energy.

[0013] Optionally, the spectrum decomposition unit further includes a target main frequency identification subunit, which identifies the target main frequency of the subsynchronous oscillation frequency according to the energy distribution spectrum. and its harmonic components, and the frequency component of the energy peak is selected as : ,in, is the main frequency of the subsynchronous oscillation, F is the range of all possible frequencies, usually the subsynchronous frequency range, is the frequency The energy is used to determine the main frequency.

[0014] Optionally, the adaptive absorption unit specifically includes: Frequency tracking subunit: Based on the recognition result of the target main frequency recognition subunit, it locks the target main frequency of the subsynchronous oscillation in real time , generate a tuning control signal of the target frequency, and tune the tuning signal frequency of the tuning control signal ; Self-tuning circuit subunit: according to the tuning signal frequency , energy absorption is achieved through the following tuning conditions: ,in, is the equivalent impedance of the tuned circuit, is the loop resistance, used to dissipate the absorbed energy, is the angular frequency of the target frequency, are the inductance and capacitance parameters of the tuning circuit, Represents an imaginary unit, representing equivalent impedance imaginary number; Fast energy storage subunit: The oscillation energy absorbed by the tuned loop is captured by a fast energy storage device (such as a supercapacitor or lithium battery).

[0015] Optionally, the adaptive absorption unit further includes a reactive power compensation subunit, which releases the absorbed energy through reactive power compensation to avoid interference with other frequency components of the power grid; The energy absorbed by the fast energy storage device is released to the grid through reactive power compensation, and the released reactive power is controlled. for: ,in, is the reactive power compensation amount, is the grid voltage, is the current released to the grid, is the phase angle between the compensation current and the grid voltage.

[0016] Beneficial effects of the present invention: The present invention actively injects low-power, nonlinearly distributed current disturbance signals through a current disturbance generating unit, dynamically destroys the coherence of subsynchronous oscillation signals, weakens the accumulation of oscillation energy from the signal source, and enhances the dynamic response capability of the system. In combination with the technology of the spectrum decomposition unit based on the composite Hilbert-Huang transform, the main frequency of the subsynchronous oscillation and its harmonic components are accurately identified, and the distribution analysis of the oscillation energy is further refined, providing high-precision target positioning capability for the oscillation suppression strategy. The coordinated operation of the two realizes multi-level oscillation suppression from active disturbance to precise control, and effectively improves the stability and adaptability of the system under complex power grid conditions.

[0017] In the present invention, the adaptive absorption unit absorbs the oscillation energy and dynamically compensates the reactive power of the power grid in real time for the key sub-synchronous frequency identified by the spectrum decomposition unit through the joint work of the self-tuning circuit and the fast energy storage device, thereby avoiding the further diffusion of the oscillation energy to the power grid and the resonance effect. The tuning circuit ensures the selectivity of the absorption frequency by adjusting the resonant frequency to match the target oscillation frequency, thereby avoiding interference with other frequency components of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic diagram of system function modules according to an embodiment of the present invention; Figure 2 A schematic diagram of a current disturbance generating unit according to an embodiment of the present invention; Figure 3 A schematic diagram of a spectrum decomposition unit according to an embodiment of the present invention; Figure 4 Schematic diagram of an adaptive absorption unit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. At the same time, it is explained here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art may also adopt other alternatives to implement some known technologies; and the accompanying drawings are only for more specific description of the embodiments, and are not intended to specifically limit the present invention.

[0021] It should be noted that the references to "one embodiment", "embodiment", "exemplary embodiments", "some embodiments" and the like in the specification indicate that the embodiments described may include specific features, structures or characteristics, but not every embodiment may include the specific features, structures or characteristics. In addition, when a specific feature, structure or characteristic is described in conjunction with an embodiment, it should be within the knowledge of a person skilled in the art to implement such feature, structure or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0022] In general, a term can be understood, at least in part, from its use in context. For example, depending, at least in part, on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in the singular sense, or can be used to describe a combination of features, structures, or characteristics in the plural sense. Additionally, the term "based on" can be understood as not necessarily intended to convey an exclusive set of factors, but can instead, depending, at least in part, on the context, allow for the presence of other factors that are not necessarily explicitly described.

[0023] like Figure 1-Figure 4 As shown, a system for suppressing subsynchronous oscillation of a double-fed grid-connected system comprises: The double-fed generator module is used to convert wind power into electrical energy, including a stator side and a rotor side. The stator side is directly connected to the grid, and the rotor side is connected to the grid through a grid-connected inverter; The double-fed generator module is used to convert wind power into electrical energy, including: The wind wheel and main shaft convert wind power into mechanical energy and drive the rotor of the generator to rotate through the main shaft; The stator side of the generator includes three-phase windings, which directly convert the mechanical energy generated by the rotor movement into constant-frequency AC power through electromagnetic induction, and are connected to the grid through fixed wiring to output active power and reactive power to the grid; The generator rotor side includes windings and slip ring devices, which capture the electromagnetic induction current inside the rotor and transmit it to the input end of the grid-connected inverter through the slip ring; The grid-connected inverter is used to convert the variable-frequency AC power obtained from the rotor side into a fixed-frequency AC power that is consistent with the grid frequency and phase, and inject the converted electric energy into the grid through the output terminal; The controller adjusts the operating parameters of the grid-connected inverter, including the amplitude, frequency and phase of the output current, to achieve grid synchronous operation and power factor optimization, and cooperates with the sub-synchronous oscillation suppression module to improve system stability.

[0024] The sub-synchronous oscillation spectrum disturbance module specifically includes: The current disturbance generating unit injects low-power, nonlinearly distributed current disturbance signals through the grid-connected inverter, destroying the coherence of the subsynchronous oscillation signal, forming random fluctuations, and suppressing the accumulation of oscillation energy; The phase decoupling optimization unit dynamically adjusts the phase relationship between the subsynchronous oscillation signal and the injected current disturbance signal to ensure destructive interference between the disturbance signal and the oscillation frequency, weaken the energy resonance effect, and achieve the optimal oscillation disturbance effect; Multi-frequency domain decomposition and absorption module, including: The spectrum decomposition unit uses the composite Hilbert-Huang transform technique to decompose the subsynchronous oscillation signal into multiple frequency domain components and identify the energy distribution of the subsynchronous oscillation frequency and its harmonic components; The adaptive absorption unit, which consists of a self-tuning circuit and a fast energy storage device, absorbs the key frequency components of the subsynchronous oscillation in real time according to the results of the spectrum decomposition unit, and releases the absorbed energy through reactive power compensation to avoid interference with other frequency components of the power grid.

[0025] The spectrum disturbance module weakens the resonance condition by actively destroying the coherence of the oscillation signal, while the multi-frequency domain decomposition and absorption module further intervenes in the frequency energy components on this basis to achieve more thorough oscillation suppression.

[0026] Through the collaborative work of the above-mentioned subsynchronous oscillation spectrum disturbance module and the multi-frequency domain decomposition and absorption module, the system can actively intervene in and precisely control the energy path generated by subsynchronous oscillations from the signal spectrum level, effectively suppress the amplitude growth of subsynchronous oscillations, and improve the dynamic stability of the system.

[0027] The current disturbance generating unit specifically includes: Oscillation monitoring subunit, real-time monitoring of the frequency of the subsynchronous oscillation signal , Amplitude ; The signal generation subunit generates a low-power, nonlinearly distributed current disturbance signal using a pseudo-random signal generator based on the output data of the oscillation monitoring subunit, and the disturbance signal has dynamically changing frequency, phase and amplitude characteristics; The inverter modulation subunit uses pulse width modulation (PWM) technology to superimpose and inject a pseudo-random current disturbance signal into the output current of the grid-connected inverter.

[0028] The oscillation monitoring subunit monitors the subsynchronous oscillation frequency, amplitude and energy distribution in real time, as follows: The real-time sampling expression of subsynchronous oscillation signal is: ,in, is a subsynchronous oscillation signal (current or voltage), is the amplitude of the oscillation signal, corresponding to the sub-synchronous frequency components, This subsynchronous frequency component is lower than the power grid frequency (10Hz to 50Hz). is the initial phase of the subsynchronous frequency component, is the number of frequencies into which the oscillating signal is resolved.

[0029] The pseudo-random current disturbance signal generation in the signal generation subunit is expressed as: ,in, is the current disturbance signal injected into the grid, is the amplitude of the current disturbance signal, which is lower than the subsynchronous oscillation signal amplitude (lower than 0.1 times the subsynchronous signal amplitude), is the frequency of the current disturbance signal, which is obtained by combining the pseudo-random number generator with the subsynchronous oscillation signal frequency The frequency distribution is in the nonlinear range. is the random phase of the disturbance signal, uniformly distributed between 0 and , is Gaussian white noise, representing random disturbance, satisfying , is the frequency number of the disturbance signal, , with a subsynchronous oscillation frequency Based on random offset Generate a disturbance signal frequency nearby, with a random offset range of Sure, Dynamically adjust according to the frequency change characteristics of the sub-synchronous oscillation signal.

[0030] The signal generation subunit also includes a nonlinear distribution relationship between the control amplitude and the frequency, which is expressed as: ,in, is the proportionality factor, which determines the maximum disturbance amplitude, It is the frequency attenuation factor, which controls the rapid decay of the disturbance signal amplitude as the frequency increases.

[0031] The pulse width modulation technology injects the disturbance signal into the output current of the grid-connected inverter. The output current of the grid-connected inverter is expressed as: ,in, is the output current of the grid-connected inverter, is the original grid output current, is the current disturbance signal; The pulse width modulation technique modulation is expressed as: ,in, It is the output voltage signal of the grid-connected inverter after PWM modulation. is the DC bus voltage of the grid-connected inverter, is the inverter's carrier frequency (usually in the kilohertz range), is the sign function, used for PWM modulation.

[0032] The phase decoupling optimization unit specifically includes: Phase difference calculation formula: ,in, is the phase difference between the current disturbance signal and the target subsynchronous oscillation signal, is the phase of the current disturbance signal, is the phase of the target subsynchronous oscillation signal; The dynamic adjustment of the phase relationship is expressed as: ,in, is the adjusted current disturbance signal phase, is the phase adjustment gain factor, which controls the rate of phase adjustment, .

[0033] The spectrum decomposition unit specifically includes: Empirical Mode Decomposition Subunit: Subsynchronous Oscillation Signals Decompose and generate a set of intrinsic mode functions (IMFs) , the following conditions are met: ,in, is the number of IMF components, indicating the number of oscillation modes obtained by signal decomposition, It is The intrinsic mode function represents the local oscillation characteristics of the signal. is the residual component of the signal, including the low-frequency trend term; Hilbert transform subunit: For each Perform Hilbert transform to generate its instantaneous frequency and the instantaneous amplitude : ,in, is the instantaneous amplitude of the IMF component, indicating the change of signal strength over time, is the instantaneous frequency of the IMF component, which represents the local oscillation frequency of the signal, is the instantaneous phase, which indicates the change of signal phase over time. represents a small increment in the time dimension, represents the Hilbert transform operation; Energy distribution calculation subunit: combined with instantaneous frequency and the instantaneous amplitude , calculate the energy distribution of each frequency component : ,in, is the target frequency The corresponding energy reflects the intensity of a specific frequency component. are the start and end time of the analysis period, is the Dirac function, which is used to extract specific frequency components The energy It is the square of the instantaneous amplitude and represents the local intensity of the signal energy.

[0034] Target main frequency identification subunit: Identify the target main frequency of the subsynchronous oscillation frequency based on the energy distribution spectrum and its harmonic components, and the frequency component of the energy peak is selected as : ,in, is the main frequency of the subsynchronous oscillation, F is the range of all possible frequencies, usually the subsynchronous frequency range, is the frequency The energy is used to determine the main frequency.

[0035] The adaptive absorption unit specifically includes: Frequency tracking subunit: Based on the recognition result of the target main frequency recognition subunit, it locks the target main frequency of the subsynchronous oscillation in real time , generate a tuning control signal of the target frequency, and tune the tuning signal frequency of the tuning control signal ; Self-tuning circuit subunit: according to the tuning signal frequency , energy absorption is achieved through the following tuning conditions: ,in, is the equivalent impedance of the tuned circuit, is the loop resistance, used to dissipate the absorbed energy, is the angular frequency of the target frequency, are the inductance and capacitance parameters of the tuning circuit, Represents an imaginary unit, representing equivalent impedance imaginary number; Fast energy storage subunit: The oscillation energy absorbed by the tuning loop is captured by a fast energy storage device (such as a supercapacitor or a lithium battery). The stored instantaneous energy is expressed as: ,in, is the energy stored in the energy storage device, is the energy storage capacitor, is the voltage across the energy storage device.

[0036] Reactive power compensation subunit: releases absorbed energy through reactive power compensation to avoid interference with other frequency components of the power grid; The energy absorbed by the fast energy storage device is released to the grid through reactive power compensation, and the released reactive power is controlled. for: ,in, is the reactive power compensation amount, is the grid voltage, is the current released to the grid, is the phase angle between the compensation current and the grid voltage.

[0037] The present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention. In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without the description of these details. In addition, in order to avoid unnecessary confusion about the essence of the present invention, well-known methods, processes, procedures, components and circuits are not described in detail.

[0038] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A system for suppressing subsynchronous oscillation of a double-fed grid-connected system, characterized in that: include: A double-fed generator module, used to convert wind power into electrical energy, comprises a stator side and a rotor side, wherein the stator side is directly connected to the grid, and the rotor side is connected to the grid via a grid-connected inverter; The sub-synchronous oscillation spectrum disturbance module specifically includes: The current disturbance generating unit injects low-power, nonlinearly distributed current disturbance signals through the grid-connected inverter, destroying the coherence of the subsynchronous oscillation signal, forming random fluctuations, and suppressing the accumulation of oscillation energy; The phase decoupling optimization unit dynamically adjusts the phase relationship between the subsynchronous oscillation signal and the injected current disturbance signal to ensure destructive interference between the disturbance signal and the oscillation frequency; Multi-frequency domain decomposition and absorption module, including: The spectrum decomposition unit uses the composite Hilbert-Huang transform technique to decompose the subsynchronous oscillation signal into multiple frequency domain components and identify the energy distribution of the subsynchronous oscillation frequency and its harmonic components; The adaptive absorption unit, which consists of a self-tuning circuit and a fast energy storage device, absorbs the key frequency components of the subsynchronous oscillation in real time according to the results of the spectrum decomposition unit, and releases the absorbed energy through reactive power compensation to avoid interference with other frequency components of the power grid.

2. A system for suppressing subsynchronous oscillation of a double-fed grid-connected system according to claim 1, characterized in that: The current disturbance generating unit specifically includes: Oscillation monitoring subunit, real-time monitoring of the frequency of the subsynchronous oscillation signal , Amplitude ; A signal generating subunit, based on the output data of the oscillation monitoring subunit, generates a low-power, nonlinearly distributed current disturbance signal using a pseudo-random signal generator; The inverter modulation subunit adopts pulse width modulation technology to superimpose and inject the pseudo-random current disturbance signal into the output current of the grid-connected inverter.

3. A system for suppressing subsynchronous oscillation of a double-fed grid-connected system according to claim 2, characterized in that: The current disturbance signal generation in the signal generation subunit is expressed as: ,in, is the current disturbance signal injected into the grid, is the amplitude of the current disturbance signal, which is lower than the amplitude of the subsynchronous oscillation signal. is the frequency of the current disturbance signal, which is obtained by combining the pseudo-random number generator with the subsynchronous oscillation signal frequency The frequency distribution is in the nonlinear range. is the random phase of the perturbation signal, is Gaussian white noise, representing random disturbance, satisfying , is the frequency number of the disturbance signal, , with a subsynchronous oscillation frequency Based on random offset Generate a disturbance signal frequency nearby, with a random offset range of Sure.

4. A system for suppressing subsynchronous oscillation of a double-fed grid-connected system according to claim 3, characterized in that: The signal generation subunit also includes a nonlinear distribution relationship between the control amplitude and the frequency, which is expressed as: ,in, is the proportionality factor, which determines the maximum disturbance amplitude, is the frequency attenuation factor, which controls the rapid attenuation of the disturbance signal amplitude as the frequency increases.

5. A system for suppressing subsynchronous oscillation of a double-fed grid-connected system according to claim 2, characterized in that: The pulse width modulation technology injects the disturbance signal into the output current of the grid-connected inverter. The output current of the grid-connected inverter is expressed as: ,in, is the output current of the grid-connected inverter, is the original grid output current, is the current disturbance signal; The pulse width modulation technique modulation is expressed as: ,in, It is the output voltage signal modulated by the grid-connected inverter. is the DC bus voltage of the grid-connected inverter, is the carrier frequency of the inverter, is a sign function.

6. A system for suppressing subsynchronous oscillation of a double-fed grid-connected system according to claim 1, characterized in that: The phase decoupling optimization unit specifically includes: Phase difference calculation formula: ,in, is the phase difference between the current disturbance signal and the target subsynchronous oscillation signal, is the phase of the current disturbance signal, is the phase of the target subsynchronous oscillation signal; The phase relationship is dynamically adjusted as follows: ,in, is the adjusted current disturbance signal phase, is the phase adjustment gain factor, which controls the rate of phase adjustment.

7. A system for suppressing subsynchronous oscillation of a double-fed grid-connected system according to claim 1, characterized in that: The spectrum decomposition unit specifically includes: Empirical Mode Decomposition Subunit: Subsynchronous Oscillation Signals Decompose and generate a set of intrinsic mode functions , the following conditions are met: ,in, is the number of IMF components, indicating the number of oscillation modes obtained by signal decomposition, It is The intrinsic mode function represents the local oscillation characteristics of the signal. is the residual component of the signal, including the low-frequency trend term; Hilbert transform subunit: For each Perform Hilbert transform to generate its instantaneous frequency and the instantaneous amplitude ; Energy distribution calculation subunit: combined with instantaneous frequency and the instantaneous amplitude , calculate the energy distribution of each frequency component .

8. A system for suppressing subsynchronous oscillation of a double-fed grid-connected system according to claim 7, characterized in that: The spectrum decomposition unit further includes a target main frequency identification subunit, which identifies the target main frequency of the subsynchronous oscillation frequency according to the energy distribution spectrum. and its harmonic components, and the frequency component of the energy peak is selected as .

9. A system for suppressing subsynchronous oscillation of a double-fed grid-connected system according to claim 8, characterized in that: The adaptive absorption unit specifically comprises: Frequency tracking subunit: Based on the recognition result of the target main frequency recognition subunit, it locks the target main frequency of the subsynchronous oscillation in real time , generate a tuning control signal of the target frequency, and tune the tuning signal frequency of the tuning control signal ; Self-tuning circuit subunit: according to the tuning signal frequency , energy absorption is achieved through the following tuning conditions: ,in, is the equivalent impedance of the tuned circuit, is the loop resistance, used to dissipate the absorbed energy, is the angular frequency of the target frequency, are the inductance and capacitance parameters of the tuning circuit, represents an imaginary unit; Fast energy storage subunit: The oscillation energy absorbed by the tuned loop is captured by a fast energy storage device.

10. A system for suppressing subsynchronous oscillation of a double-fed grid-connected system according to claim 9, characterized in that: The adaptive absorption unit also includes a reactive power compensation subunit, which releases the absorbed energy through reactive power compensation to avoid interference with other frequency components of the power grid; The energy absorbed by the fast energy storage device is released to the grid through reactive power compensation, and the released reactive power is controlled. for: ,in, is the reactive power compensation amount, is the grid voltage, is the current released to the grid, is the phase angle between the compensation current and the grid voltage.

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