Efficiency Optimization of a Dynamic Wireless EV Charging System Using Coupling Coefficient Estimation

Dynamic Wireless Power Transfer (DWPT) systems are becoming an interesting option for charging EVs in urban and suburban areas, due to its advantages. Since Efficiency of these system is of major concern, maximizing transferred power efficiency is analyzed in this paper. Optimization of equivalent load resistance is proposed in this paper by using a DC-DC buck converter in the secondary side. Since the optimum load is a function of coupling coefficient which may varies for moving vehicles, an estimation method is proposed to calculate it dynamically. By using the estimated coupling coefficient, an optimum equivalent load resistance and the corresponding buck duty cycle is calculated and applied to the converter by PWM method to maximize the efficiency. In addition, a voltage regulation method is proposed by controlling the duty cycle of the primary side inverter. As a result, the load voltage is fixed at its reference value and a constant power is delivered to the load even if coupling coefficient changes. The proposed control method is applied to a DWPT system, where the simulation results indicate the effectiveness of the proposed method.