Research On Key Issues Of Integrated Charging Topology And Regenerative Braking For Electric Vehicle

Renewable energy vehicles,containing hybrid electric vehicles,plug-in hybrid vehicles and fuel cell vehicles are seeing a fundamental development with the energy transformation.On-board charging and regenerative braking are the main power supply of batteries.The thesis focuses on two problems of electric vehicles:1)control of power decoupling circuit and rectifier in power decoupling converter;2)line braking torque distribution of four-wheel drive electric vehicle.Three current inner loop control methods are analyzed and compared:PI current control,parabolic method and dead time compensation hysteresis control method;two outer loop controllers:direct power decoupling typical controller,automatic power decoupling typical controller;and automatic power decoupling controller with power outer loop.Based on the power decoupling circuit,the structure and design of each controller are analyzed and compared.Simulation results show that the proposed power outer loop dead time compensated hysteresis inner loop automatic power decoupling controller has an ideal DC steady-state voltage and current waveform,and the design difficulty is also lower than the direct power decoupling control structure.By summarizing and comparing the above control methods,the general methodology of anti-disturbance design is obtained.In a four-wheel drive electric vehicle,the braking energy feedback efficiency can be improved with suitable braking torque distribution strategy.Based on the slip losses and electromechanical losses,an online torque distribution strategy is proposed.Through the sensitivity analysis,the assumption that the motor braking torque change does not affect the motor speed and the load change of the tire is obtained.The motor efficiency curve is derived,and a flow chart form algorithm for online braking torque distribution is thus obtained.During the procedure,the dimension of variable is reduced from four to one.Finally,the online algorithm is compared with the offline algorithm and the traditional braking torque distribution algorithm,and the Carsim-Simulink co-simulation is performed.The simulation results show that the online torque distribution algorithm has strong real-time performance and high efficiency,together with better adaption to different vehicle parameters.