Design and Implementation of Improved SEPIC Bidirectional DC-DC Converter with Switched Inductors

The objective of this paper is to modify the topology of the unidirectional non-coupled inductor modified SEPIC converter to a bidirectional topology and applied between the DC bus and the battery energy storage system. To improve the conversion ratio, active switched inductors are employed, eliminating the need for a coupled inductor or transformer. This approach offers several advantages, including continuous input current non-inverting input and output. Furthermore, by increasing the switching frequency and utilizing wide bandgap components such as gallium nitride (GaN) instead of Si-based MOSFETs, the converter's volume can be reduced while achieving high efficiency and excellent high-frequency characteristics. The paper will provide an analysis of the operational principles and present experimental results with the following specifications: low side voltage of 48V, high side voltage of 400V, switching frequency of 500kHz, and output power of 500W. The step-down mode achieves a peak efficiency of 93.7%, while the step-up mode reaches a peak efficiency of 90.9%.