High step‐up direct ac‐ac boost converter with optimal component counts based on SEPIC

Abstract

This paper introduces a new direct step‐up ac‐ac converter designed based on the SEPIC. It provides a higher step‐up conversion ratio than other counterparts with valuable features like high efficiency, reasonable input and output total harmonic distortions (THD), continuous input current waveform, common ground, few components, and single‐stage conversion without snubber and LC filters. Unlike most counterparts, the duty cycle can be varied between zero and one in boost operation and is not limited to any value below one. The voltage stress on one switch is reduced by increasing the winding coefficient of the utilized coupled inductor, and current stress on another is independent of this coefficient. It reduces the switches' losses and improves the converter efficiency. Thanks to the above attributes, the proposed converter is suitable for inductive power transfer from low‐voltage ac sources, operating as an ac voltage regulator for sensitive ac loads, and any applications that require a boost converter with few components. This article shows the converter's operation principle and evaluates its performance through experiments on a 225 W prototype. Accordingly, the maximum obtained efficiency is 95.4%. The input and output current THDs for the nominal inductive load equal 4.5 and 2.8%, respectively. Results confirm the claims.