A Dual-Frequency-Detuning Method to Improve Coupling Tolerance for Wireless Power Transfer System

This paper proposes a dual-frequency-detuning method to provide smooth wireless power transfer under coupling variations, which exploits the fundamental and third-order harmonic components of a square-wave voltage out of a full-bridge inverter. The fundamental and third-order harmonic components alternately serve as the main power transfer channel under strong and weak coupling conditions, respectively. The primary and secondary sides are designed as different detuning states under various frequencies to maintain effective power transfer. Based on the proposed detuning rate design method, less power fluctuation over large coupling variation can be achieved. A 130W simulation system with a 50kHz square-wave excitation is built to verify the theoretical modeling and analysis. The simulation results show that the system can realize a quasi-constant output power against a coupling coefficient range from 0.32 to 0.68, with a maximum power fluctuation of less than 5%.