CN-122026396-A - Method, system, equipment and medium for suppressing broadband oscillation of grid-connected converter

CN122026396ACN 122026396 ACN122026396 ACN 122026396ACN-122026396-A

Abstract

The invention discloses a method, a system, equipment and a medium for suppressing broadband oscillation of a grid-connected converter, which belong to the technical field of grid-connected oscillation suppression. The system comprises a resonance characteristic identification module, a self-adaptive damping adjustment module, a phase loss quantization module, a phase lag compensation module, a virtual complex resistance reconstruction module and a cooperative damping suppression execution module. The invention overcomes the problem of negative damping instability caused by digital control delay under the working condition of a weak current network through the coupling of the frequency selective virtual impedance and the self-adaptive phase compensation technology. And the rapid locking and nondestructive inhibition of broadband burst oscillation are realized, and the running stability and the robustness of the grid-connected converter under an extremely weak power grid are obviously improved.

Inventors

HE MINGJUN
ZHANG SONG
SHI TONG
He Molin
XU CHANG
YANG LUNHUI
ZHOU ZIJIAN
FAN KE
WANG YANG
SONG ZIHONG
YOU XINYU
YIN CHENBIN
MAO YANG
DENG SONG
OUYANG GUANGZE
ZHOU LIN

Assignees

贵州电网有限责任公司

Dates

Publication Date: 20260512
Application Date: 20251230

Claims (10)

1. The method for suppressing broadband oscillation of the grid-connected converter is characterized by comprising the following steps of: acquiring an electric signal of a grid-connected point, and constructing a resonance characteristic identification model by combining frequency domain distribution differences of fundamental wave components and harmonic wave components, wherein resonance characteristic parameters of the harmonic wave components in the electric signal of the grid-connected point are extracted through the resonance characteristic identification model, and the resonance characteristic parameters comprise oscillation center frequency and resonance voltage amplitude; Combining the resonance characteristic parameters, dynamically obtaining a self-adaptive damping adjustment model through dead zone threshold value judging logic and nonlinear gain mapping logic, and determining a virtual resistance amplitude through the self-adaptive damping adjustment model; Combining the resonance characteristic parameters, obtaining a phase loss quantization model through quantization association of system delay characteristics and phase lag, and calculating a phase compensation angle through the phase loss quantization model; Combining the phase compensation angle, constructing a phase lag compensation model through an advanced phase superposition principle, and correcting a virtual impedance phase through the phase lag compensation model so as to maintain positive damping characteristics; Combining the virtual resistor amplitude and the phase compensation angle, and reconstructing a frequency selective virtual complex impedance model through vector coupling of the amplitude and the phase; And generating a virtual damping voltage instruction through the frequency selective virtual complex impedance model, and superposing the virtual damping voltage instruction to a modulation wave to drive the converter to act so as to inhibit broadband harmonic oscillation.
2. The method for suppressing broadband oscillation of a grid-connected inverter according to claim 1, wherein the method comprises the following steps: the step of constructing a resonance characteristic identification model by combining the frequency domain distribution difference of the fundamental wave component and the harmonic wave component, and the step of extracting resonance characteristic parameters of the harmonic wave component in the grid-connected point electric signal through the resonance characteristic identification model comprises the following steps: Establishing self-adaptive orthogonal signal generation logic based on closed-loop feedback as the resonance characteristic identification model; calculating a dynamic error signal between the grid-connected point electric signal and a model feedback estimated value; Processing the dynamic error signal through an integral adjustment mechanism to iteratively update an oscillation center frequency, and generating an in-phase component and a quadrature component which are mutually orthogonal by using the oscillation center frequency as a reference variable; and calculating the resonance voltage amplitude through vector synthesis of the in-phase component and the quadrature component, and combining the oscillation center frequency and the resonance voltage amplitude into the resonance characteristic parameter.
3. The method for suppressing broadband oscillation of a grid-connected inverter according to claim 1, wherein the method comprises the following steps: combining the resonance characteristic parameters, dynamically obtaining an adaptive damping adjustment model through dead zone threshold value judging logic and nonlinear gain mapping logic, and determining a virtual resistance amplitude through the adaptive damping adjustment model comprises the following steps: Presetting a dead zone voltage threshold and a nonlinear growth coefficient; comparing the resonance voltage amplitude in the resonance characteristic parameter with the dead zone voltage threshold value; When the resonance voltage amplitude is smaller than or equal to the dead zone voltage threshold value, setting the virtual resistance amplitude to be zero or a preset reference maintenance value; When the resonance voltage amplitude is larger than the dead zone voltage threshold, a nonlinear function with the nonlinear growth coefficient as an index is called, a damping response value which monotonically increases along with the resonance voltage amplitude is calculated, and the damping response value is output as the virtual resistance amplitude.
4. The method for suppressing broadband oscillation of a grid-connected inverter according to claim 1, wherein the method comprises the following steps: combining the resonance characteristic parameters, obtaining a phase loss quantization model through quantization association of system delay characteristics and phase lag, and calculating a phase compensation angle through the phase loss quantization model comprises the following steps: acquiring the total inherent delay time of a digital control system, wherein the total inherent delay time represents the time consumption of all-link signal processing from a signal acquisition end to a control instruction output end; determining a basic hysteresis phase angle corresponding to the total inherent delay time under the oscillation center frequency through the phase loss quantization model; and converting the basic lag phase angle into an angle value and superposing a preset phase safety margin to obtain the phase compensation angle.
5. The method for suppressing broadband oscillation of a grid-connected inverter according to claim 1, wherein the method comprises the following steps: And combining the phase compensation angle, constructing a phase lag compensation model through a lead phase superposition principle, and correcting the virtual impedance phase through the phase lag compensation model comprises the following steps: Defining lead phase rotation logic for the oscillation center frequency in the phase lag compensation model; Inputting the phase compensation angle into the advance phase rotation logic; and shifting the phase angle response characteristic of the virtual impedance to the leading direction by the value of the phase compensation angle by utilizing the leading phase rotation logic, so that the virtual impedance presents non-capacitive positive damping characteristic at the oscillation center frequency.
6. The method for suppressing broadband oscillation of a grid-connected inverter according to claim 1, wherein the method comprises the following steps: The reconstructing the frequency selective virtual complex impedance model by combining the virtual resistance amplitude and the phase compensation angle through vector coupling of the amplitude and the phase comprises: constructing a transfer function in the form of a second-order band-pass filter by taking the oscillation center frequency as a center frequency, the virtual resistance amplitude as a passband gain and the phase compensation angle as a phase rotation parameter; a transfer function in the form of the second order bandpass filter is established as the frequency selective virtual complex impedance model whose impedance magnitude approaches zero at the fundamental frequency.
7. The method for suppressing broadband oscillation of a grid-connected inverter according to claim 1, wherein the method comprises the following steps: Generating a virtual damping voltage command through the frequency selective virtual complex impedance model, and superposing the virtual damping voltage command into a modulation wave to drive the converter to act comprises: Processing grid-connected point current signals acquired in real time by utilizing the frequency selective virtual complex impedance model, extracting a resonant current component corresponding to the oscillation center frequency, applying the virtual resistance amplitude and the phase compensation angle to the resonant current component, and generating the virtual damping voltage instruction; Reversely superposing the virtual damping voltage command to a fundamental wave voltage reference signal of the converter for transmitting fundamental wave power to generate a final modulation wave; And driving the converter submodule switching device to act by utilizing the final modulation wave, and generating reverse damping voltage for inhibiting the resonant current at the converter alternating current port.
8. A system for suppressing broadband oscillation of a grid-connected inverter, a method for suppressing broadband oscillation of a grid-connected inverter according to any one of claims 1 to 7, comprising: The resonance characteristic identification module is used for acquiring the grid-connected point electric signals, constructing a resonance characteristic identification model by combining the frequency domain distribution difference of the fundamental wave component and the harmonic wave component, and extracting resonance characteristic parameters of the harmonic wave component in the grid-connected point electric signals through the resonance characteristic identification model, wherein the resonance characteristic parameters comprise oscillation center frequency and resonance voltage amplitude; The self-adaptive damping adjustment module is used for combining the resonance characteristic parameters, dynamically obtaining a self-adaptive damping adjustment model through dead zone threshold value judgment logic and nonlinear gain mapping logic, and determining a virtual resistance amplitude through the self-adaptive damping adjustment model; The phase loss quantization module is used for combining the resonance characteristic parameters, obtaining a phase loss quantization model through quantization association of the system delay characteristic and the phase lag, and calculating a phase compensation angle through the phase loss quantization model; The phase lag compensation module is used for combining the phase compensation angle, constructing a phase lag compensation model through the advanced phase superposition principle, and correcting the virtual impedance phase through the phase lag compensation model so as to maintain the positive damping characteristic; The virtual complex resistance reconstruction module is used for combining the virtual resistance amplitude and the phase compensation angle and reconstructing a frequency selective virtual complex resistance model through vector coupling of the amplitude and the phase; and the cooperative damping suppression execution module is used for generating a virtual damping voltage instruction through the frequency selective virtual complex impedance model, and superposing the virtual damping voltage instruction into a modulation wave to drive the converter to act so as to suppress broadband harmonic oscillation.
9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, carries out the steps of a method for broadband oscillation suppression of a grid-tie inverter according to any one of claims 1 to 7.
10. A computer readable storage medium having stored thereon a computer program, characterized in that the computer program when executed by a processor realizes the steps of a method of grid-tie inverter broadband oscillation suppression according to any one of claims 1 to 7.

Description

Method, system, equipment and medium for suppressing broadband oscillation of grid-connected converter Technical Field The invention relates to the technical field of grid-connected oscillation suppression, in particular to a method, a system, equipment and a medium for suppressing broadband oscillation of a grid-connected converter. Background With the continuous expansion of new energy grid-connected scale mainly based on wind and light and the wide application of flexible direct current transmission technology, the short-circuit ratio of the power grid is obviously reduced, and the characteristics of a weak power grid with high impedance and weak support are presented. Under the background, the control loop of the modularized multi-level converter is easy to interact with weak grid impedance, so that the problem of broadband harmonic resonance is caused. The resonance phenomenon has wide coverage frequency range and strong burst, the voltage or current distortion of the grid-connected point is caused by light resonance phenomenon, the protection action of equipment is triggered by heavy resonance phenomenon, and even the grid-off accident of the system is caused. There are still a number of limitations to the current methods of suppressing such resonances. The passive damping attenuates harmonic waves by adding a resistor-capacitor or a resistor-inductor-capacitor filter, but the passive element parameters are fixed, so that the passive damping cannot adapt to the time-varying characteristic of the impedance of the power grid, is huge in volume and can introduce additional fundamental wave power loss. The fixed parameter virtual impedance control simulates damping characteristics at an algorithm level, but the parameters are usually set off-line based on specific working conditions, so that the fixed parameter virtual impedance control is difficult to adapt to wide fluctuation of the short-circuit ratio of a weak current network, and the self-adaptive capacity for coping with time-varying working conditions is lacking. In addition, the conventional virtual resistance strategy usually acts on the full frequency band, and a larger virtual resistance value is often required to suppress stronger resonance, which can generate a significant voltage drop at the frequency of the power frequency fundamental wave, and seriously affect the power transmission efficiency in a steady state. More importantly, the prior art often ignores the sampling and computation delays inherent in digital control systems. In a wide frequency range, particularly in a high frequency range, significant phase lag is introduced in control delay, so that an originally set positive damping resistor presents a negative damping characteristic on an actual physical level, and high-frequency resonance is aggravated. The existing self-adaptive scheme depends on complex online impedance identification or spectrum analysis based on a long window function, is large in calculated amount and long in convergence time, and is difficult to quickly lock and restrain sudden harmonic oscillation in a millisecond grid-connected transient process. Disclosure of Invention In view of the above problems, the present invention provides a method, a system, a device and a medium for suppressing broadband oscillation of a grid-connected inverter. The invention solves the technical problems that the existing virtual impedance technical parameter is fixed, the fluctuation of the short-circuit ratio of a weak power grid is difficult to adapt, the fundamental wave voltage loss is caused by full-frequency band damping, the high-frequency negative damping instability is caused by neglecting digital control delay, and the sudden broadband oscillation cannot be effectively solved. The technical scheme includes that an electric signal of a grid-connected point is obtained, a resonance characteristic identification model is built by combining frequency domain distribution difference of fundamental components and harmonic components, resonance characteristic parameters of the harmonic components in the electric signal of the grid-connected point are extracted through the resonance characteristic identification model, the resonance characteristic parameters comprise oscillation center frequency and resonance voltage amplitude, an adaptive damping adjustment model is dynamically obtained through dead zone threshold judgment logic and nonlinear gain mapping logic by combining the resonance characteristic parameters, virtual resistance amplitude is determined through the adaptive damping adjustment model, a phase loss quantization model is obtained through quantization of system delay characteristics and phase lag quantity by combining the resonance characteristic parameters, a phase compensation angle is calculated through the phase loss quantization model, a phase lag compensation model is built by combining the phase compensation angle, virtual impedance phase is corrected th