CN-120784903-B - Pre-oscillation stable monitoring active damper for grid-connected power electronic system

CN120784903BCN 120784903 BCN120784903 BCN 120784903BCN-120784903-B

Abstract

The invention discloses a pre-oscillation stable monitoring active damper for a grid-connected power electronic system, and belongs to the technical field of power electronics. The method comprises the steps of stabilizing energy storage of a direct-current voltage control loop, calculating power grid impedance and inverter impedance based on fundamental wave separation and FFT by a stability monitoring loop through wideband pulse disturbance injection synchronous with phase locking, generating an activation signal by utilizing MPC criteria, starting a virtual resistor by a damping control loop according to the activation signal, and dynamically adjusting the virtual resistor through closed loop optimization to enable the stability margin of a system to approach a critical value. The invention realizes intervention before oscillation, solves the problems of response delay, high energy consumption and poor compatibility of the traditional scheme, and has the simulation display that the response time of harmonic suppression is less than or equal to 20ms and the THD is reduced to 0.57 percent.

Inventors

LIU ZIPENG
ZHOU YIHAN
LIU JINJUN
CHEN DAWEI
BAO GUOJUN
ZENG ZHIJIE
Wu Jialuo
LIN XIAOQING
TIAN YE

Assignees

西安交通大学
国网福建省电力有限公司

Dates

Publication Date: 20260508
Application Date: 20250806

Claims (10)

1. A pre-oscillation stability monitoring active damper for a grid-tied power electronic system, comprising: the direct-current voltage control loop is connected with the direct-current capacitor and used for adjusting the voltage of the direct-current capacitor to stabilize energy storage and feeding back redundant energy to the power grid; The stability monitoring loop, the input end connects the voltage signal and current signal of the electric wire netting, the output end produces and activates/activates the signal; The damping control loop, the input end receives the said activation/deactivation signal, the output end produces the fictitious resistance control signal; the stability monitoring circuit includes: The disturbance injection module outputs a periodic broadband pulse signal to the output end of the active damper, and the injection phase of the disturbance injection module is synchronous with the voltage of the power grid through a phase-locked loop, so that the time domain response data of the voltage and the current are obtained in real time; The input end of the impedance calculation module is connected with a power grid voltage and current response signal, and the power grid impedance Z g and the inverter impedance Z inv are calculated through separation of a fundamental component and fast Fourier transformation; the stability criterion module is used for triggering an activation/deactivation signal by comparing the minimum loop gain T track with a preset stable forbidden zone based on a maximum peak standard criterion; The damping control loop includes: the virtual resistor generation module is used for generating a self-adaptive virtual resistor value R v according to the activation signal and dynamically adjusting the output impedance Z ad of the active damper; The closed loop optimization module calculates new loop gain T with Z ad in real time, and the track of T approximates to the set stability margin boundary by iteratively adjusting R v .
2. The active damper for pre-oscillation stability monitoring of grid-connected power electronic system according to claim 1, wherein the acquired voltage-current time domain response data is processed as follows: the disturbance response is first separated by subtracting the fundamental waveform, then frequency domain analyzed using an FFT on the separated disturbance response, and the impedance of the system is calculated based on the frequency domain information.
3. The active damper for pre-oscillation stability monitoring of grid-connected power electronic system according to claim 1, wherein the disturbance injection module outputs a set periodic pulse reference signal, the duration of a single pulse of which is 0.5% -5% of the grid period, and each injection time maintains a fixed phase difference with the grid voltage zero crossing point through a phase-locked loop.
4. The pre-oscillation stability monitoring active damper for a grid-connected power electronic system of claim 1, wherein the impedance calculation module performs: The method comprises the steps of obtaining time domain response data, subtracting fundamental wave waveforms from the time domain response data to separate disturbance responses, performing fast Fourier transform on the separated disturbance responses to obtain frequency domain information, and calculating grid impedance Z g and inverter impedance Z inv based on the frequency domain information.
5. The active damper for pre-oscillating stability monitoring of a grid-connected power electronic system according to claim 1, wherein in the stability criterion module, the stability exclusion zone is a region that the nyquist curve corresponding to the minimum loop gain T in the complex plane is not allowed to enter, and when any part of the nyquist curve enters the exclusion zone, it is determined that there is a potential risk of instability or insufficient stability margin of the system.
6. The pre-oscillating stability monitoring active damper for a grid-connected power electronic system of claim 1, wherein the initial R v of the virtual resistance generation module is 0.1-1 Ω, R v is increased when the stability margin is greater than a set threshold, and R v is decreased when the stability margin is less than the set threshold.
7. The active damper for pre-oscillation stability monitoring of a grid-tied power electronic system of claim 1, wherein the input of the phase-locked loop is connected to a grid voltage signal and the output provides a phase-synchronized clock signal to the disturbance injection module.
8. The pre-oscillating stable monitoring active damper for grid-tied power electronic systems of claim 1, wherein the dc voltage control loop comprises: The voltage sampling circuit is used for collecting the voltage of the direct-current capacitor; and the current tracking controller drives the full-bridge circuit to feed back direct-current side energy to the power grid.
9. The active damper for pre-oscillation stability monitoring of grid-connected power electronic system according to claim 1, wherein the hardware carriers of the stability monitoring loop and the damping control loop are digital signal processors, the disturbance injection module realizes pulse signal output through a PWM generator of the digital signal processors, the impedance calculation module is executed through an FFT calculator built in the digital signal processors, and the virtual resistance generation module updates R v in real time through a floating point operation unit of the digital signal processors.
10. The active damper for pre-oscillation stability monitoring of a grid-tied power electronic system of claim 1, wherein the active damper is electrically connected to a grid common coupling point through an output interface circuit, the output interface circuit being configured to filter switching frequency harmonics output by the power electronic converter and to match impedance characteristics between the damper and the grid.

Description

Pre-oscillation stable monitoring active damper for grid-connected power electronic system Technical Field The invention belongs to the technical field of power electronics, and particularly relates to a pre-oscillation stable monitoring active damper for a grid-connected power electronic system. Background With the wide application of renewable energy sources such as wind energy and solar energy, power electronic equipment such as grid-connected inverters have become an important component of modern power systems. However, the nonlinear characteristics of the power electronic equipment and the interaction of the power electronic equipment with the power grid easily cause the problem of system stability under the condition of weak power grid, so that the operation reliability is reduced, and the safety of the power grid is affected. To address these issues, damping techniques stabilize the system by reshaping the system impedance characteristics. Referring to fig. 1, the conventional passive damping method adopts passive elements such as resistors, capacitors or inductors, and the like, which can immediately suppress oscillation, and has simple implementation and low cost, but the fixed damping characteristic and inherent energy loss limit the application of the passive damping method in modern power electronic systems. The active damping method constructs a virtual resistor through an additional feedback control loop, can theoretically restrain oscillation without physical energy loss and adapt to real-time change of a power grid, but needs to modify the existing system control, and is not compatible with a third party converter lacking an open control interface. On the basis of an active damping method, an active damper independent of the existing power electronic system is provided, and the external connection mode enables the active damper to adapt to most of the existing power electronic systems on the premise of guaranteeing an active damping function. However, most of the existing active dampers are in reactive working modes, damping is activated only when the harmonic amplitude exceeds an IEEE harmonic standard threshold, and the delayed response can cause unstable propagation in a system, increase total harmonic distortion and reduce the power quality. Disclosure of Invention The invention aims to solve the technical problems of the prior art, and provides a pre-oscillation stable monitoring active damper for a grid-connected power electronic system, which is used for solving the technical problems of excessive power loss caused by current response delay and dependence on fixed parameter setting and poor compatibility with the existing system controller. The invention adopts the following technical scheme: A pre-oscillation stability monitoring active damper for a grid-tied power electronic system, comprising: the direct-current voltage control loop is connected with the direct-current capacitor and used for adjusting the voltage of the direct-current capacitor to stabilize energy storage and feeding back redundant energy to the power grid; The stability monitoring loop, the input end connects the voltage signal and current signal of the electric wire netting, the output end produces and activates/activates the signal; The damping control loop, the input end receives the said activation/deactivation signal, the output end produces the fictitious resistance control signal; the stability monitoring circuit includes: The disturbance injection module outputs a periodic broadband pulse signal to the output end of the active damper, and the injection phase of the disturbance injection module is synchronous with the voltage of the power grid through a phase-locked loop, so that the time domain response data of the voltage and the current are obtained in real time; The input end of the impedance calculation module is connected with a power grid voltage and current response signal, and the power grid impedance Z g and the inverter impedance Z inv are calculated through separation of a fundamental component and fast Fourier transformation; the stability criterion module is used for triggering an activation/deactivation signal by comparing the minimum loop gain T track with a preset stable forbidden zone based on a maximum peak standard criterion; The damping control loop includes: the virtual resistor generation module is used for generating a self-adaptive virtual resistor value R v according to the activation signal and dynamically adjusting the output impedance Z ad of the active damper; The closed loop optimization module calculates new loop gain T with Z ad in real time, and the track of T approximates to the set stability margin boundary by iteratively adjusting R v. Preferably, the acquired voltage-current time domain response data is processed, specifically as follows: the disturbance response is first separated by subtracting the fundamental waveform, then frequency domain analyzed using an FFT on t