A soft-switching three-phase ac-ac converter with a high-frequency ac link

A new three-phase ac-ac converter with a high-frequency ac link, soft switching characteristic, unity input power factor, step-up and step-down operation, and bidirectional power flow is introduced in this paper. The converter's link is composed of an ac inductor and a very small ac capacitor; there is no short-life bulky electrolytic capacitor. Moreover, the converter's switches are zero voltage at turn-on and low loss at turn-off; therefore, the switching losses are considerably low, which subsequently permits the switching frequency to be high. The total number of the switches in this novel topology is as low as twelve, suitable for low power applications. The basic operation of the new converter includes eight distinct modes, which are described in detail. The analysis and optimal design of the proposed topology are carried out as well. Simulation results are also given to demonstrate the effectiveness of the proposed power converter.