Research On Grid-Connected Technology Of V2G Charging Pile And Smart Microgrid

Electric Vehicles,EVs have been strongly supported and developed because they do not need to consume fossil fuels and exhaust emissions.V2G(Vehicle to Grid)technology combines electric vehicles and Smart Grid to realize the interaction of energy between them.It has become a research hotspot at present.Charging pile plays an important role in the process of two-way flow of energy.For the access process of electric vehicles to the micro-grid,how to control charging and discharging behavior with reasonable strategies,effectively suppress harmonics and reduce the harm to the grid is the key technology to realize V2 G.This paper studies the selection of charging and discharging mode and grid connection of electric vehicles,chooses two-stage charging pile as the research object,chooses three-phase voltage converter to realize rectification or inversion for AC/DC,and controls with voltage and current double closed-loop.The design of the controller mainly includes dq coordinate transformation and decoupling,voltage and current loop design,SVPWM vector control method,and numerical calculation of some important device parameters.As for DC/DC,BUCK/BOOST topology is selected to realize boost and buck,and constant current charging and constant current discharging strategy is adapted to take control.On this basis,some improvement on the strategy is conducted concerning the current control strategy cannot select the charging and discharging mode according to the user's wishes.A mode selection module is added to the DC/DC,which will give priority to the user input mode.When the user has no input,the charging or discharging mode will be automatically selected according to the battery SOC(State of Charge)of the electric vehicles,the operation status of the power grid and the current electricity price.A low-power hardware platform is built to verify the control strategy and topology,including the design and analysis of the main circuit,driving circuit,sampling circuit and zero-crossing comparison circuit.The grid-connected experimental results and grid-connected standards are compared and analyzed,which proves the feasibility of the proposed control strategy.