A Novel Bipolar Direct PWM Controlled Buck-Type AC/AC Converter

This paper proposes a topology structure of a bipolar direct PWM controlled AC-AC converter. It consists of two identical single-ended AC-AC converters, which eliminates the current reversal problem during energy feedback compared to the traditional bidirectional switch-type AC-AC converters. Since the duty cycles of the two converters in the circuit can be independently controlled, bipolar modulation of the output voltage can be achieved. In the modulation strategy, there is no need to determine the direction of the inductor current, only the polarity of the output voltage needs to be determined, enabling direct PWM control of the converter. Through the design and production of an experimental prototype, the experimental results validate the feasibility and effectiveness of the proposed bipolar AC-AC converter topology and its modulation strategy.