A Transformerless Bidirectional Active Switched Inductor-Based SEPIC High-Gain DC–DC Converter With Buck–Boost Capability

The growing demand for efficient and compact power conversion systems in electric vehicles (EVs), renewable energy systems, DC microgrids, and both portable and stationary medical equipment has intensified research into non-isolated high-gain bidirectional DC-DC converters. Existing solutions often employ transformer-based topologies or coupled inductors, which introduce increased cost, size, and control complexity. This paper presents a novel transformerless bidirectional high-gain DC-DC converter based on a modified Single-Ended Primary Inductor Converter (SEPIC) architecture. The proposed topology incorporates an Active Switched Inductor (ASL) at the input stage to achieve a wide voltage conversion ratio while ensuring reduced voltage stress on the main power switches. A key feature of the converter is its ability to provide bidirectional buck–boost operation in both power flow directions, while maintaining a reduced component count and improved efficiency through synchronous rectification. The converter’s performance is thoroughly analyzed under both continuous conduction mode (CCM) and discontinuous conduction mode (DCM). Furthermore, detailed small-signal modeling and closed-loop controller design are developed for both voltage-mode and current-mode control. A 200 W experimental prototype employing SiC MOSFETs is implemented to validate the theoretical analysis. Experimental results confirm the high efficiency, robust dynamic response, and practical feasibility of the proposed converter for next-generation power conversion applications.