Research On Control Strategy Of Microgrid Inverter Based On Virtual Synchronous Generator

With the progressive development of society and overused energy,human beings are facing problems such as energy crisis and environmental issues.The concept of microgrid technology is proposed to generate electricity with renewable energy.The addition of the Virtual Synchronous Generator(VSG)algorithm enables the traditional inverter to simulate the inertial damping,voltage and frequency regulation characteristics of the synchronous generator,improving the stability of the microgrid.In this paper,the inverter based on VSG control is chosen as main study object.This paper is focused on the inverter based on VSG control,and its working principle and control strategy running in island and grid-connected mode.First,analyze the mathematical model of the synchronous generator,imitate the working principles of its electrical and mechanical parts,establish a mathematical model of the VSG algorithm,and design the active-frequency control link and the reactive-voltage control link.Perform mathematical modeling of the main circuit of the VSG control algorithm,design the selection strategy of related component parameters,design the voltage and current double loop control,and give the overall topology of the microgrid inverter based on the VSG control strategySecondly,as VSG microgrid inverters are susceptible to the adverse effects of system randomness and volatility,the islanding mode is taken as the research object,and the sliding mode control with variable structure is introduced into the VSG control strategy.By establishing the mathematical model of the island mode VSG output voltage in the αβ coordinate system,derive the control law of the sliding mode variable structure control.In order to further improve the anti-interference ability of the system,combine the back-stepping control strategy with the sliding mode variable structure control strategy.The backstepping sliding mode control strategy can make up the shortcomings of the backstepping control that is sensitive to system parameters and lacks robustness.Then,take the LCL type VSG microgrid inverter in grid-connected mode as the research object.According to the inherent resonance characteristics of the LCL filter,a Bode diagram is plotted to make an detailed analyze on the resonance mechanism of the LCL filter and the effect of the traditional passive damping method on the resonance.Aiming at the power consumption of passive damping,an active control strategy is proposed based on virtual impedance.In order to achieve multi-objective optimization,combine the sliding mode variable structure control with the active damping control strategy,and propose an improved current double-loop control strategy to improve the system’s anti-interference ability and output voltage and current quality.Finally,this article establishes a VSG simulation model based on the MATLAB/Simulink simulation experimental platform,design different experimental conditions,simulates the involved control strategy,and verifies the correctness and rationality of the proposed strategy with simulation results.