Isolated ZVS High-Frequency-Link AC-AC Converter With a Reduced Switch Count

This paper introduces an isolated soft-switched three-phase ac-ac converter with a high-frequency link and reduced switch count for low- and medium-power applications. A small air-gapped high-frequency transformer acts as the key component by providing galvanic isolation as well as transferring power using its magnetizing inductance. Two small ac capacitors are placed on both sides of the transformer to realize zero-voltage switching for the semiconductor devices in addition to passive clamping. Therefore, the proposed topology is expected to be highly efficient and reliable due to soft-switching operation and exclusion of limited-lifetime electrolytic capacitors. Furthermore, the proposed converter has a high input power factor, step-up/down ability, and bidirectional power flow with arbitrary output voltage amplitude and frequency. The basic operation of the converter includes eight modes and is described in detail. Theoretical analysis and design are also given to illustrate its operation at various operating points. Simulation and experimental results are provided to verify the performance of the proposed power converter.