Design Of Charging Piles For Electric Vehicles And Research On Charging And Discharging Strategies

In recent years,environmental and energy issues are accelerating the development of electric vehicle technology.As a green travel tool,the popularity of electric vehicles is increasing.Among them,electric vehicle charging piles are a hot topic in the field of electric vehicle research,mainly focusing on energy storage technology and energy surplus technology.Its performance directly affects the development of electric vehicles.However,the charging piles currently put on the market generally have the disadvantages of large volume,low power and high cost,and cannot recover and reuse the remaining energy in electric vehicles.In view of the above problems,this paper proposes a two-way charging pile system based on V2G.The main research contents are as follows:The thesis studies and analyzes the V2G technology and domestic and international development trends,as well as the commonly used circuit topology of V2G charging piles.On this basis,the three-phase half-bridge voltage-type bidirectional AC/DC converter is selected as the pre-circuit topology,half-bridge The two-way DC/DC converter is used as the post-stage circuit topology.The working principles of bidirectional AC/DC converter and bidirectional DC/DC converter are analyzed,and their mathematical models are established.Secondly,in order to meet the requirements of the charging pile,the front-stage bidirectional AC/DC converter uses a voltage and current double closed-loop control strategy in a synchronous rotating coordinate system,which can speed up the voltage response speed of the three-phase PWM rectifier to a certain extent and stabilize the DC bus voltage Both work under unit power factor when realizing rectification and inverter.In order to improve the service life of the lithium battery,the post-stage bidirectional DC/DC converter uses a constant voltage control strategy in the charging state and a constant current control strategy in the discharging state.In the simulation environment of Matlab/Simulink,a simulation model of V2G charging pile was built,and the simulation results were analyzed.The simulation results show that:in the charging state,the voltage and current phases of the grid side are the same,the DC bus voltage is stable at 700V,and the power factor is about 1.In the discharge state,the phase of the grid-side voltage and current differs by 180°,and the DC bus voltage is also stable at 700V.The stability of the DC bus voltage indicates that the V2G charging pile has good dynamic performance.Finally,the main control module and system software module of the electric vehicle DC charging pile are designed.