A 21-kW Unfolding-Based Single-Stage AC-DC Converter for Wireless Charging Applications

This article introduces a single-stage grid-tied ac-dc conversion system designed for wireless charging applications. The proposed system employs a T-type converter to process soft dc-link voltages that are generated by a 3-Phi Unfolder. To achieve multiple control-related tasks simultaneously, such as input power factor correction and output power regulation, a modulation scheme is presented for the high-frequency T-type converter. The T-type converter-based soft-dc to dc system is modeled using the phasor transformation technique, and closed-loop control analysis is performed to effectively regulate the battery current. In addition, in order to facilitate power level scalability, a modular architecture is proposed, and a board with dimensions of 26.2 in (L) x 13.2 in (W) x 4.5 in (H), including the cold plate, is designed to house three T-type converters, each rated for 21 kW of output power. Hardware results of a 21-kW prototype are presented based on a single T-type module. The prototype demonstrates an ac-dc efficiency from the grid to the battery of similar to 96% and a grid current total harmonic distortion of 1.27%. To demonstrate the modular structure for multiple T-type converters operated in tandem, six T-type converter modules are tested in parallel, and corresponding hardware results are presented as well.