Unfolder-Based Single-Stage AC-AC Conversion System for Wireless Charging Applications

This paper presents a grid-frequency to high-frequency AC-AC converter and its control scheme for wireless charging applications. The proposed AC-AC converter utilizes a T-type converter to process the soft DC-link generated by a 3-F unfolder. A control strategy for the T-type converter to perform both power factor correction and output voltage or current control simultaneously is presented in this paper. The expressions for duty ratios of the T-type converter are derived using the fundamental harmonic analysis method. Simulation results for a 100 kW system driving a series-series compensated wireless charging topology are presented to validate the control method. Hardware results of a 1 kW scaled-down prototype with less than 2% grid current THD using feed-forward control are presented to demonstrate the applicability of the proposed system.