Design And Research Of DC Charging System For Electric Vehicle

With the worsening of the environmental problems and the traditional energy consumption is increasing,the popularity of electric vehicles(EVs)has become an inevitable trend.This is because the EVs can realize the local utilization of renewable energy and improve the overall operation of the economic and environmental benefits.With the growing popularity of EVs,there is an urgent demand to solve the impact and stress on grid caused by irregular and frequent access of EVs.But at present,the research in this field is still in the theoretical stage,and there is not a set of feasible and practical methods.Therefore,a new type of DC charging system structure and improved power supply and charging strategy is proposed in this thesis,to ensure the rapid charging of EVs on the basis of solving the existing problems in charging of EVs.The specific research contents are as follows:1.The new type of DC charging system structure is designed,and the AC and DC hybrid power supply system is analyzed in this thesis.Photovoltaic power(PV)generation system and AC grid hybrid power supply are used to ensure the effective utilization of new energy resources based on the continuous power supply of the charging system.PV power generation is the main power supply mode.The system modeling and the circuit topology of each unit are analyzed,and the power flow mode in the DC charging system is summarized.2.A fast charging strategy based on virtual synchronous generator(VSG)and an improved MPPT control method are proposed.AC and DC power supply circuit controller were designed separately.The DC power supply circuit adopts an improved MPPT control strategy based on hysteresis,which can effectively reduce misjudgments and system concussion so as to make the maximum use of the solar energy.The AC power supply system adopts the control strategy based on VSG,in order to ensure the continuous supply of power supply system and effectively solve the impact of the power grid.3.From the point of view of load,an self-regulating charging algorithm for EVs is proposed.The two stage droop control strategy based on battery SOC is used to make the charging load share the fluctuation of the system in a certain range within a certain range,and self-regulate charging,in order to avoid the frequent access and exit of power grid.This will cause unnecessary waste and increase harmonic pollution.4.The hardware platform of DC charging system based on DSP28335 is built,and the feasibility of control strategy is verified.According to the control scheme proposed in this thesis,the simulation model of each part and the whole of the system are built firstly,and the theory is verified.Then,the hardware platform of each part of the system is built,the main power circuit parameters of the system and the peripheral hardware circuit,including the sampling circuit,drive circuit,etc.are designed.The design of the circuit and the selection of the device are described in detail,and the experimental results are analyzed.