Research And Application Of Control Strategy Based On Virtual Synchronous Generator In Microgrid

With the continuous development of new energy industry in China,if micro grid and large grid can operate stably,inverter is an important device of new energy access to the grid,so it is imperative to study the control strategy of inverter,which is also one of the hot issues in the electrical field.The new energy power generation is affected by the region,environment and other aspects,and its anti-interference ability is weak.The traditional inverter control strategy is not enough to meet the demand of modern users for power quality.The inverter control strategy based on virtual synchronous generator(VSG)technology can simulate the damping and inertia characteristics of synchronous generator on the basis of traditional inverter control strategy,and can better realize active frequency regulation and reactive voltage regulation.It is an effective and feasible control strategy,and has important practical significance for the research of VSG Technology.Based on VSG technology,this paper studies the control strategy of inverter,establishes the mathematical model,designs the VSG control model by analyzing the principle and control process of synchronous generator,and verifies the feasibility of VSG technology through simulation.Aiming at the three factors affecting power quality: voltage,frequency and harmonic,three improved control strategies are proposed,namely seamless switching technology based on virtual reactance,adaptive technology based on improved JD(J represents rotor inertia,D represents damping coefficient)and control strategy based on improved current harmonic suppression.In order to make the output phase and voltage of the system consistent with the large power grid before grid connection,it is necessary to adjust the output frequency.Based on VSG technology,the pre synchronization control technology is proposed,which can adjust the output frequency of the inverter in time by tracking the signal of the inverter output frequency,and improve the traditional pre synchronization technology by introducing virtual reactance,which lays the foundation for smooth switching of the system.In order to solve the adverse effects of frequency disturbance and input power disturbance on output power,based on VSG technology,virtual inertia and virtual damping are introduced by simulating synchronous generator parameters.Based on the improved adaptive inertia damping coefficient,JD is changed into adaptive control strategy on the basis of fixed traditional JD.In order to solve the problem of current harmonics caused by distributed generation(DG)access,a new method based on proportional resonance(PR)is proposed,Based on the traditional harmonic suppression,VSG technology is introduced to design pr double loop control strategy.By comparing the current and power with or without PR controller,the current harmonic analysis is carried out,and finally an improved PR controller harmonic suppression control strategy is realized.The three control strategies are improved on the basis of the original traditional control strategy,and then through Matlab/Simlink modeling and simulation,the control effect of the three control methods is significantly improved compared with the original control method,and the feasibility and effectiveness of the three control methods are verified.