A Soft-Switched Three-Phase AC-AC Converter With a High-Frequency AC Link

This paper introduces a three-phase ac-ac resonant converter with a high-frequency ac link, soft-switching operation, almost unity input power factor, step-up/down capability, and bidirectional power flow. The converter's link is composed of an ac inductor and a small ac capacitor. The link inductor transfers power by charging through the input and discharging to the output, and the link capacitor creates partial resonances to realize zero-voltage switching for all the switches of the converter. Therefore, the proposed topology is expected to have high reliability and long lifetime due to the soft-switching operation and exclusion of short-life electrolytic capacitors. The total number of switches in this novel topology is as low as 12, which is suitable for low-and medium-power applications. The basic operation of the converter includes eight modes, which are described in detail. The full analysis and optimal design of the proposed topology are provided as well. Results of several simulations and experiments at different operating conditions are also presented to show the validity of the proposed converter.