Research On The Control Strategy Of Charging And Discharging Device Of Electric Vehicle Based On V2G

In recent years,in order to solve the increasingly serious environmental and energy issues,electric vehicles have been widely promoted and applied.V2G(Vehicle to Grid)is an interactive technology of smart grid and electric vehicle,and an effective way to avoid the idle electric vehicle energy.The V2 G charging and discharging machine plays an important role in connecting the electric vehicle and the electric network.Aiming at the problem of bidirectional flow of electric energy in the V2 G charging and discharging machine,this paper makes an in-depth study from the following aspects.Firstly,the development status of V2 G technology in electric vehicle charging station is analyzed in detail.According to the demand of charging and discharging,the design of the AC/DC converter and the back stage bidirectional DC/DC converter is used as the topology of the V2 G charge and discharge motor.Then the characteristics of the common battery are analyzed,a lithium battery is used as an electric vehicle battery and its mathematical model is established,which provides a basis for simulation modeling.Secondly,in order to meet the demand of fast charging and discharging,a deadbeat predictive current controller is designed.According to the switching status of AC/DC converter and the output voltage vector and the current dynamic equation of an electric current in a ?? stationary coordinate system,an improved deadbeat predictive current control model is obtained.In order to improve the service life of the lithium battery,the constant current and constant voltage control strategy is adopted in the bi-directional DC/DC converter.In the initial stage of charging,the constant current charging with current single closed loop control is used.When the voltage reaches a certain value,it switches to constant voltage charging of double closed loop control of voltage and current.In order to meet the demand of grid connected discharge,the constant current discharge control strategy with current single closed loop control is adopted.Furthermore,the V2 G system simulation model is built in Matlab/Simulink.The simulation results verify the correctness of the control strategy.Whencharging,the constant current and constant voltage charging is realized,the phase of the voltage and current is the same as that on the grid side,and the power factor is about 1.The constant current discharge is used in the discharge,and the phase different between voltage and current on the network side is ?.At the same time,the voltage of DC side is stability.The results show that the discharge of this charging and discharging system has good dynamic performance,and DC bus voltage fluctuation is small.Finally,the experimental platform is set up,and partial charge or discharge experiments are carried out,the bidirectional flow of electric energy is verified.