An optimal ZVS angle selection for constant current charging of EV's battery in series-series compensated wireless power transmission system

In this paper, first, to realize the constant current charging for EV's Battery and ZVS operation of primary inverter simultaneously, variable frequency and phase shift control strategy (VF-PSC) is adopted and the optimal operation frequency range (OOFR) is obtained. Second, a three loop control strategy (TLCS) is proposed to make the system work accurately at any points of this OOFR by adjusting the zero voltage switching angle (ZVSA). Third, to achieve the maximum efficiency of the system, a maximum efficiency point tracking strategy (MEPT) is proposed to maximize the system efficiency by changing the ZVSA continuously in OOFR. The combination between TLCS and MEPT is prominent and excellent because it realizes constant current charging, ZVS operation, and maximum system efficiency simultaneously, which dramatically reduces EMI, improves the security and reliability, and saves electrical energy. Finally, a 500W WPT system (WPTS) is built to verify the correctness of theoretical analysis and the effectiveness of the proposed control strategy.