A Three-Phase Triple-Voltage Dual-Active-Bridge Converter for Medium Voltage DC Transformer to Reduce the Number of Submodules

In order to improve the power density of dc transformer (DCT), this article proposes a novel three-phase dual-active-bridge (DAB) dc–dc converter, which possesses triple input voltage of conventional full-bridge DAB converter without increasing the voltage stress of switches. By adopting it as the DCT submodule (SM), the number of SMs in DCT is reduced markedly and power density can be improved. Based on the analysis of operation principle, design procedure, basic control strategy and startup scheme of the proposed three-phase triple-voltage DAB (T
²
-DAB) converter are presented. Then, the feasibility of proposed converter is verified with simulation and a 2 kW, 600/200 V prototype. Finally, the superiority of the DCT scheme based on proposed T
²
-DAB converter is verified by a comparison with some existing DAB schemes.