Bidirectional Single Power-Conversion DC–AC Converter With Noncomplementary Active-Clamp Circuits

Abstract

This paper presents a bidirectional single power-conversion dc-ac converter with noncomplementary active-clamp circuits. The proposed converter comprises a bidirectional flyback converter and an unfolding bridge. In order to interface the grid with a low-voltage energy storage through only single power-conversion, the bidirectional flyback converter transforms the low voltage directly into the folded grid voltage and regulates the folded grid current. The proposed converter adopts noncomplementary operation strategy for the active-clamp circuits. By using this strategy, the bidirectional flyback converter not only avoids the voltage spike but also minimizes the power losses by the circulating energy. Thus, with single power-conversion and noncomplementary active-clamp circuits, the proposed converter obtains high power efficiency. To facilitate the bidirectional single power-conversion, a novel control algorithm is developed. With this control algorithm, the proposed converter ensures high grid power quality and seamless mode transition. The proposed bidirectional dc-ac converter is theoretically analyzed in detail. The experimental results based on a 250-W prototype are provided to evaluate its performance.