Research On Charging And Discharging Control And Scheduling Methods Of Electric Vehicles In The Park Micro-Grid

In recent years,Electric Vehicle(EV)and its related technologies are developing rapidly,and its market share is increasing year by year.This technology can enable electric vehicles to participate in grid operation in an orderly manner,improve the efficiency of grid operation,have the functions of valley power peak use,auxiliary grid frequency regulation,and smooth new energy power generation,etc.It can also enable electric vehicle owners to obtain certain economic benefits and realize a win-win situation for both grid and electric vehicle owners.However,V2 G technology has not yet been applied on a large scale,and most EVs are in a disorderly charging state,and the current structure of the distribution grid cannot accept a large number of EV feeders.Therefore,while maintaining the stable operation of the microgrid in the region,how to realize the bi-directional transmission of electric energy between the grid and EVs,adjust the charging and discharging power of EVs according to the real-time information,and realize the coordinated scheduling of EVs and other new energy sources in the region has gradually become a hot spot in the industry.This paper focuses on the above key issues,combines advanced control strategies and optimization methods,and conducts in-depth research on V2 G technology and optimal dispatching strategies,with the following main research contents.First,to solve the energy transfer problem between EV and grid at the bottom control level,a control strategy of EV charging and discharging interface based on Virtual Synchronous Generator(VSG)technology is proposed.The working principle and mathematical model of the conventional three-phase synchronous generator are analogous,the bidirectional converter control technology is analyzed,and the circuit topology of the EV charging/discharging interface is studied,and then the VSG technology is applied to the AC side control of the EV charging/discharging interface.Simulink simulation verifies that the proposed control strategy can achieve bi-directional power flow at the bottom control.Second,to reduce the adverse effects of the complex structure of VSG system,high grid inrush current,and low control accuracy due to the phase-locked loop structure,a fractional order sliding mode control(FOSMC)-based grid-connected control strategy for VSG system without phase locking loop is proposed.According to the principle of frequency loop control on the AC side of VSG,the controller is used to generate frequency compensation signal,and then realize the automatic tracking of grid frequency and phase of the system.The Simulink simulation verifies that the proposed control strategy can automatically track the grid frequency and phase during the grid connection of the VSG system,and the grid connection shock is small and the system operation is stable.Then,in order to solve the problem that a large number of electric vehicles are randomly connected to the grid,which leads to increased frequency fluctuations and reduced stability of the grid,a distributed electric vehicle intelligent charging and discharging control strategy based on a neuro-fuzzy controller is proposed.Based on the previously proposed EV charging and discharging interface control,the neuro-fuzzy controller is introduced to combine expert experience and online learning technology to automatically project the optimal value of output power,which reduces the battery loss of EVs while relieving the pressure on the grid,taking into account the EV charging state,battery capacity and real-time frequency of the grid.The proposed control strategy is verified by MATLAB/ANFIS simulation to enable EVs to autonomously adjust charging and discharging power based on real-time information,which can meet EV users’ expectations while participating in grid frequency and voltage regulation to maintain system stability and improve grid operation efficiency.Finally,in order to solve the problem of excessive peak-to-valley difference of the park load caused by the park photovoltaic consumption and electric vehicle access to the power grid,an optimization strategy of the park microgrid electric vehicle orderly charging and discharging based on the improved pigeon flock algorithm is proposed.The mathematical model of EV orderly charging and discharging is established,and the improved pigeon flock algorithm is adopted to solve the EV charging and discharging scheduling problem by considering the output of PV power generation system in the park,system economic efficiency,operational stability and user satisfaction.Finally,it is verified through simulation that the proposed control strategy can make electric vehicles cut peaks and fill valleys,reduce users’ charging costs,and achieve mutual benefit for vehicles and networks.