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

Due to the energy shortage and various contradictions and problems between non-renewable energy such as fossil fuels and the environment are becoming more and more serious,renewable energy such as solar energy and wind energy has gradually attracted people's attention.These renewable energy sources are connected to the distributed system,which has the advantages of energy conservation,environmental protection,safety and stability.Microgrid is a new type of distributed power supply,which can effectively improve power quality,avoid power failure and improve power generation efficiency.Inverter is the link of energy exchange between distributed generation system and microgrid.However,due to the lack of rotary inertia and damping characteristics of the inverter,the stability of the microgrid cannot be guaranteed.Synchronous generators have natural good inertia and damping,and are widely used in power grids.Therefore,if the operation mode of synchronous generators can be simulated and the inverter has corresponding rotary inertia and damping characteristics,then the safety and stability of micro grid can be guaranteed.Therefore,virtual synchronous generator technology came into being.In this paper,the structure and characteristics of micro grid are briefly introduced,the current development status of micro grid is analyzed,and it is concluded that the inverter is the key to the development of micro grid.Then,by introducing three traditional control methods of micro-grid inverter,the control process of the three methods is analyzed,and then a new inverter control strategy,virtual synchronous generator control technology,is introduced.The structure and mathematic model of synchronous generator are introduced,and the mathematic model and topology of virtual synchronous generator are obtained.The design of the main control algorithm of the virtual synchronous generator is presented,and the phase-locked loop structure based on the second order generalized integral is applied to the virtual synchronous machine system.Then,a kind of adaptive control based on virtual synchronous generator is proposed,the influence of rotation inertia and damping coefficient on output frequency and power fluctuation of virtual synchronous generator is studied,and the optimal damping ratio of a system is determined.The simulation model of virtual synchronous generator is built on MATLAB/Simulink software platform,and the simulation verifies the feasibility of virtual synchronous generator algorithm to control the inverter and that the phase-locked loop based on second-order generalized integral can improve the stability of the system.Finally,a system experimental circuit is built in theModelingTech power electronics simulation experiment system to further verify the accuracy of the virtual synchronous generator control strategy.