Research On The Charging Technology Of Electric Vehicle Based On Virtual Synchronous Machine

With the increasing number of electric vehicles,the load of electric vehicles charging will have a non-negligible influence of the power system.By using the energy storage characteristics of EV batteries,idle EV can participate in grid regulation and provide support for power grid.At present,the research in this direction is mainly focused on cluster scheduling,which relies on the dispatching control center of power grid.It is lack of autonomy,and insufficient consideration is given to the charging demand of electric vehicles.On the other hand,the traditional converter control strategy has the problems of power shock and harmonic interference.Therefore,an EV charging technology based on virtual synchronous machine is studied in this thesis.Through the introduction of the VSM model,the charger can participate in power grid regulation independently.The damping and inertia characteristics introduced in the model also make the power output characteristics of the charger more friendly and reduce the impact of power electronic devices on the power system.However,damping and inertia also make the dynamic response speed of the converter become slow,and the power regulation cannot be adjusted quickly and smoothly.To solve this problem,an inertia and damping adaptive regulating control strategy of VSM on load side was proposed.At different stages of power regulation,the inertia J and damping D of VSM will be regulated autonomously to realize the optimal control of output power.Finally,dead zone and sectional droop coefficient are introduced for the charging strategy to improve the regulating capacity of daily load fluctuation of electric vehicles and preserve the battery life,based on droop control of VSM.In order to verify the effectiveness of the strategy,the MATLAB/Simulink model was established,and the simulation experiment was carried out.Simulation results show that theproposed virtual synchronization control strategy in this thesis has better dynamic adjustment performance.It has faster adjustment speed and it can avoid the occurrence of oscillation and overshooting.The EV charging strategy based on this model can effectively participate in grid frequency regulation and meet the user's demand.