Research For Smooth Switching Of Microgrid Based On Virtual Synchronous Generator

With the global energy crisis and environmental pollution becoming increasingly serious,clean energy is increasingly favored by human beings,promoting the use and research of distributed generation technologies that use solar energy and wind energy as the main energy sources.However,the inherent randomness of distributed power supplies limits its large-scale grid connection.As an efficient distributed power organization,microgrid can effectively avoid the adverse effects of direct integration of distributed power into the grid and give full play to the advantages of renewable energy.The operation capability of the microgrid in grid-connected and island operation mode and the smooth switching in the process of grid-connected switching are the key to the technical and economical realization of the micro-grid.Smooth switching is the basic requirement for ensuring the full utilization of distributed energy and flexible and reliable operation of the microgrid.Therefore,an effective control strategy is needed to ensure smooth switching between the stable operation and the operation mode of the system in the two modes of operation.Firstly,aiming at the shortcomings of the traditional inverter control strategy,combined with the mathematical model of synchronous generator,this paper designs a new virtual synchronous generator control strategy,which makes the output of the inverter have the inertia and damping characteristics of the synchronous generator.The ability of the microgrid to cope with sudden changes in load.At the same time,the influence of virtual inertia coefficient and damping coefficient on frequency variation is analyzed,and this is used as a reference for parameter tuning.Then the virtual synchronous generator control and constant power control are combined to form a dual-mode parallel inverter control strategy,so that the micro-grid can flexibly switch different inverter control strategies in different operating modes.According to the switching process of microgrid from island to grid connection,a pre-synchronization control strategy is designed.By real-time tracking and effective processing of grid voltage amplitude and phase,the smooth switching of microgrid grid-connected process is realized.At the same time,the traditional state following controller is improved for the switching process of the grid-connected to island operation mode,which makes the impact of the off-grid process smoother.Finally,the microgrid model of master-slave structure is built on MATLAB/Simulink platform,and the effectiveness of the proposed control strategy is verified.