Research On Design And Control Strategy Of Efficientwireless Charging System For Electric Vehicles

With the continuous development of Wireless Power Transmission(WPT),its application is becoming more and more widespread.WPT has developed rapidly on electric vehicle(EV)due to its safty and convenience.In order to promote the industrialization of WPT technology in the field of electric vehicles,the author design and manufacture a wireless charger for EV based on SiC devices.The prototype designed in this paper has a rated power of 6.6kW when the air gap between primary and secondary is 150 mm.It can also ensure that the output voltage is adjusted within the range of 200~500V.Other than this,it has reached the relevant standards of the vehicle charger: the output voltage ripple peak-to-peak value coefficient is 0.51%,the output current ripple peak-to-peak value coefficient is 0.39%,and the efficiency of the WPT system in the prototype is as high as 95.7%.In order to ensure the universality of wireless chargers,this paper investigates dozens of electric vehicle manufacturers' products to get their common characteristics,and finally determines the technical specifications of wireless chargers.By establishing the mathematical model of the coupler in WPT system,the conclusion is show that secondary side equivalent impedance and the primary secondary loss resistance will affect the energy transfer efficiency of the coupler.This provides a theoretical basis for the design of the coupled coil in a WPT system.Finally,the correctness and effectiveness of the coupler's design proposed in the paper are verified by experiments.Through theoretical analysis and small signal model analysis for the secondary converter in the WPT system,the author design suitable control system.This paper show that the prototype can achieve constant voltage and constant current output in different work mode.Finally,the experimental results prove the correctness and reliability of the system's design.Lastly,after the mathematical modeling analysis of WPT system,the time domain solution of primary coil current is given by mathematical iterative operation.Compared with the simulation results,the correctness of the mathematical model is verified.Through simulation and experimental verification for the proposed phase-shift limiting strategy,the effectiveness of this strategy in the startup process is analyzed and compared.And the result is get that phase-shifting open-loop current limiting control strategy is simple and effective in the startup process.