Research On Parameter Adaptive Control And Frequency Stability Based On Virtual Synchronous Generator

At the present stage,people are so keen to pursue a happy life that the demand for energy is huge.In the circumstances,traditional fossil energy storage can no longer meet the long-term development in the future.To solve the current resource problem,the crucial thing is to adopt the renewable energy with the large storage,pollution-free renewable energy.As the major power generation method,distributed power generation technology also faces challenges.Due to the lack of mechanical energy storage devices,traditional power electronic converters cannot provide sufficient inertia and damping support for large power grids as traditional synchronous generators.Conversely,through simulating the characteristics of synchronous generator,the Virtual Synchronous Generator(VSG)control can provide sufficient and variable inertia and damping for the grid system,improving the "friendliness" between the microgrid and the large grid.However,there are many factors that affect the operation of the microgrid system.The most common ones are load switching,power changes,etc,which need to be considered and deal with in a timely manner by the VSG control algorithm.Based on this control requirement,this dissertation mainly discusses the power disturbance,parameter adaptation and frequency stability of the VSG control system.The specific content is as follows:Firstly,on the basis of basic topology of the microgrid inverter,by the analysis of the mathematical model of the synchronous generator,the fifth-order mathematical model of the VSG is established.On the other hand,in the VSG control algorithm,a analysis and design is made for the links of active-frequency and reactive-voltage as well as the principle formula of voltage and current double closed-loop control at the same time.And the simulation is be verified in the MATLAB/Simulink.Secondly,during the operation of the VSG,given the phenomenon of power bulge and anticlimax,a adaptive control strategy of inertia and damping is proposed,which can suppress the overshoot of system variables,improve the transient stability of the system,and make the system output frequency,voltage,current,and power all quickly reach a stable state again.Thirdly,since the the VSG control algorithm can only achieve primary frequency modulation without the frequency adjustment.In this case,a Linear Active Disturbance Rejection Control secondary frequency modulation control is proposed to deal with the load switching in the island state.Compared with the second frequency modulation control strategy based on proportional integral(PI)control proposed by most scholars,the dissertation analyzes and resets the parameters of the control system on the basis.Finally,on the semi-physical experimental platform based on the VSG algorithm is built in this dissertation,the frequency and voltage regulation characteristics of the VSG are verified through relevant experimental tests,which proves that the control algorithm is effective and feasible.