A Dual Frequency Tuning Method for Improved Coupling Tolerance of Wireless Power Transfer System

This letter proposes a dual-frequency tuning method for improved coupling tolerance of an inductively coupled wireless power transfer (WPT) system by exploiting the fundamental and third-order harmonic components of a square-wave voltage out of a full-bridge inverter. A dual-frequency hybrid compensation topology is designed to simultaneously utilize the characteristics of series-series (SS) and LCL-S networks under the two different frequencies. Consequently, the output power of the proposed system under a fixed load is maintained approximately constant against coupling variations. A practical hybrid WPT system with a 100 kHz square-wave excitation and a 10.5 Ω resistive load is built to verify the theoretical modeling and analysis. Experimental results show that the system achieves an approximately constant output voltage and power of around 39 V and 150 W against a coupling coefficient variation from 0.52 to 0.72, with maximum fluctuations less than 5% and 10%, respectively.