Design And Optimization Of Wireless Electric Vehicle Charging System Ground Device Based On SiC Devices

The rapid development of electric vehicle industry has brought great challenges to vehicle charging equipment.The traditional wired charging method uses charging gun to connect the electric vehicle with the charging pile,which brings a series of problems: the wiring is complex,the charging gun is easy to be damaged,and the charging equipment cannot move flexibly.The emergence of the wireless charging technology provides a solution for it.Traditional wireless charging system is based on Si device,which has poor performance in high temperature and high frequency environment.In order to improve the performance of wireless charging system,this dissertation uses SiC device to develop the ground device of wireless charging vehicle.Firstly,this dissertation studies the structure of the ground device.The characteristics of different APFC technologies and high-frequency inverter are compared and analyzed,and the topology design and control scheme of ground power module are completed.Aiming at reliability and flexibility,the output characteristics of four compensation networks are studied deeply,and the topology structure of the ground compensation network is determined by comparison.In order to suppress the high-order harmonic of the inverter output,a harmonic suppression circuit is proposed,and the parameter design method of the harmonic suppression circuit is proposed by analyzing the harmonic components of the inverter output current,which greatly reduces the harmonic content of the output current of the power module.Secondly,this dissertation develops power factor correction circuit,inverter module,ground compensation network.Based on the analysis of the high frequency characteristics of the ground device,the power device selection scheme is determined.The input power factor of the ground device is greatly improved by using APFC technology.In order to avoid tripping fault,a soft-start circuit is added to suppress the impulse current.By comparing the parameters of SiC MOSFET and Si MOSFET,the driving characteristics of SiC MOSFET are analyzed,and the driving circuit with high reliability is designed.In view of the voltage oscillation and voltage spike caused by the switching speed of SiC MOSFET,a suitable snubber circuit is used to absorb the oscillation and voltage spike energy.In order to ensure that the thermal failure of the ground device will not occur,air-cooling radiator and copper cooling fin are selected to provide low thermal resistance channel for the power device.Finally,the experimental platform of ground device is built to conduct experiments on the power module and ground compensation network.The results show that the ground power module works stably,the inverter output current harmonic content is low,the input power factor is greater than 0.99,and the peak efficiency of the power module is higher than 98.3%.Compared with Si device,SiC device has advantages in efficiency,power density and volume.Using SiC power devices can effectively improve the performance of wireless charging system.