Research On Half Cycle Control Technology Of High Efficiency Topology For Electric Vehicle Charger

In order to improve the environmental pollution and solve the energy crisis,countries all over the world are vigorously developing new energy vehicles,among which electric vehicles are the first to be popularized in the market in recent years due to the relatively mature technology.With the popularity of electric vehicles,the corresponding supporting infrastructure has also been rapid development.With the development of smart grid,V2 G technology emerges as the times require.Therefore,it is of far-reaching significance and wide application prospect to study the charging and discharging system of electric vehicles which can realize two-way energy flow.In this dissertation,AC/DC converter of DC fast charging system is taken as the research object to improve the charging and discharging efficiency of the system under the premise of realizing V2 G function:(1)The research status of the key technology of charging and discharging in DC fast charging system is analyzed,and the basic no dead time topology of AC/DC converter is determined.Based on this topology,the mathematical model is established in different coordinate systems,and the working principle of the topology in the full cycle and half cycle control strategy is compared and analyzed.A control method which can improve the efficiency of the charger is determined theoretically.(2)Space vector pulse width modulation(SVPWM)is studied.Based on SVPWM technology,this paper analyzes that the reason that affects the efficiency of charger under half cycle control strategy is the current zero-crossing distortion.The reason of current zero-crossing distortion is analyzed qualitatively and quantitatively,that is sudden change of inductance current at zero-crossing point.And then,a half cycle control strategy to suppress current zero-crossing distortion is proposed.(3)Based on the proposed half cycle control strategy to suppress current zerocrossing distortion,the corresponding software and hardware parameters are designed,including the selection of power devices,the parameter design of key inductors and capacitors,and the corresponding software execution flow chart.The overall architecture of the system is given,and the corresponding test platform is built.In addition,in order to verify the rationality of the theoretical analysis,based on MATLAB/Simulink simulation platform,the corresponding simulation model is built,and the rationality of the relevant parameter design through simulation is verified.Finally,an experimental prototype is built and the corresponding experiments are carried out.The simulation and experimental results show that the topology and control strategy can achieve the desired effect,and prove the feasibility of the theoretical analysis.The proposed half cycle control strategy can improve the efficiency of the charger system.