Bidirectional Isolated Hexamode DC–DC Converter

Abstract

The proposed isolated buck-boost series resonant dc dc converter contains two full-bridge hybrid switching cells capable of half-bridge operation. This feature is regarded as topology morphing control. The voltage buck regulation requires special modulations applied to the primary-side hybrid switching cell. In contrast, the voltage boost regulation requires special modulations for the secondary-side hybrid switching cell. Combining the topology morphing control with the buck-boost regulation capability a novel dc-dc converter operating in six different modes is derived. Moreover, the proposed converter is capable of bidirectional operation. This paper describes how the topology morphing control influences the converter dc voltage gain, which results in three boost and three buck modes. The obtained six modes are described and equations for the converter dc voltage gain are provided. Selected design guidelines for the power part and control system are presented. Using those, a 350 W prototype was designed and built. Experimental results confirm the theoretical expressions for the converter dc voltage gain. Experimental efficiency is provided in a wide input voltage range for both energy transfer directions. Analysis of operating points with the highest thermal stress of components is presented with corresponding power loss breakdown calculations confirming measured thermal results.