Feedback Operating Frequency Control for Eliminating Dead Zone in Dynamic Wireless Power Transfer

Dynamic wireless power transfer using repeater coils is studied as a cost-effective method that allows a single inverter to supply power to multiple transmitter coils. However, this method has a zone where the receiver coil positions on a transmitter coil called a dead zone. In the dead zone, the transfer efficiency and received power are significantly reduced. This is caused by matching the series resonance frequencies of each closed-loop circuit with the operating frequency of the inverter. Therefore, this article proposes the operating frequency control of the inverter to improve the power factor, which increases the efficiency and received power. The angle difference between the inverter output voltage and current is measured, and the operating frequency is controlled using a proportional–integral controller so that the angle difference becomes 0. From the experimental results, it was confirmed that the efficiency is 0.90 and the received power increases by <inline-formula><tex-math notation="LaTeX">$\text{1.33} \,\text{kW}$</tex-math></inline-formula> when the operating frequency in the dead zone is not fixed compared to when it was fixed. In addition, the settling time of the operating frequency and angle difference was compared between the hill climbing algorithm and the proportional–integral controller. The settling time decreased by <inline-formula><tex-math notation="LaTeX">$\text{2.9} \,\text{ms}$</tex-math></inline-formula>.