An identical bipolar buck‐boost AC‐AC converter based on a coupled‐inductor with safe‐commutation, high gain, and high efficiency

Abstract This article proposes a new identical bipolar buck‐boost AC‐AC converter with integrated coupled inductors. It possesses all the critical features of a bipolar buck‐boost topology, providing both in‐phase and anti‐phase output voltages. Compared to its counterparts, a high boost factor is achieved without large duty ratios due to using magnetic coupling. Also, a high efficiency is obtained. A unipolar half‐cycle modulation is employed in which only half of the switches of a phase‐leg are modulated per half‐cycle. Therefore, only two out of eight power switches operate at high frequency at any instant, ensuring high‐efficiency operation. The safe‐commutation operation is achieved by completely turning on the auxiliary switches of the main phase leg for a half‐cycle, ensuring a continuous inductor current path during dead times. This results in voltage‐spike‐free operation. Additionally, this converter benefits from continuous input current and performs well with inductive and non‐linear loads. The proposed topology can mitigate both voltage sags and swells due to bipolar operation when employed as a dynamic voltage restorer (DVR). Its high boost factor helps compensate for deep voltage sags (above 50%). This article presents the detailed theoretical aspects of the proposed topology, followed by experimental verifications on laboratory‐built hardware.