High Efficiency Isolated 5-Level Dual Active DC–DC Converter Using Wide Band Gap Devices

Abstract

In this paper a bidirectional isolated dc-dc converter is proposed for application in shipboard power systems. In this topology, an active 5-level T-type converter is used on the primary and secondary sides of a high-frequency transformer. The operation of the proposed converter is optimized based on minimizing power losses. For the optimization, the transformer core loss, reactive power, and rms current are considered. Wide band gap devices are used for minimization of semiconductor switching losses. A control method based on the Fourier series and decomposition theorem is proposed. The proposed converter features higher efficiency, fault tolerant capability and smaller filter size compared to the common dual active bridge dc-dc converters. To reduce voltage overshoot, a laminated dc-link is designed and a two-level turn-off method is used for operating frequencies around 75 kHz. Finally, the step-up and step-down operations of the proposed structure are verified through experiments.