Single Stage Wireless Power Transfer Battery Charger for Electric Vehicles

This paper analyzes the feasibility of a wireless charging system for electric vehicles controlled with variable frequency. The design of the battery charger is based on the load requirements, that have been defined with a complete characterization of the battery pack. The coupling system and compensation networks have been sized to guarantee the voltage gain requested by the load and to allow soft-switching operations of the inverter MOSFETs. In particular, with a parallel secondary compensation, the vehicle assembly inductance is reduced when compared with a series compensation, allowing space and weight on the vehicle to be saved. The control system is designed to generate a variable inverter output voltage in the range of variation demanded by the direct supply of a Li-Ion battery pack connected to the WPT output. The paper demonstrates that the output voltage range is obtained with a switching frequency that falls into the range recommended by the SAE J2954:2020 standard.