Dual-Mode Wide-Voltage-Range Operation of Hybrid Triple Active Bridge Converter for Bipolar DC Distribution Systems

In this paper, the dual-mode bipolar hybrid triple active bridge (HyTAB) converter is proposed for bipolar DC systems with a wide output voltage operation range and bidirectional power transfer capability. The converter operates in the quasi-parallel mode at lower output voltages and switches to the series mode at higher output voltages. Moreover, the power flow between positive and negative poles can be actively dispatched. The mode switching between the quasi-parallel mode and the series mode of the proposed converter is achieved without additional auxiliary bidirectional switches. In addition, soft switching of the active switches in the converter can be achieved within a wide voltage range with the dual-mode operation. The boundary of the two modes is determined with consideration of minimal total conduction loss of the switches. The performance of the proposed dual-mode converter is validated by an experimental prototype with a +/- 110 V bipolar input voltage and a 40-120 V output voltage range, demonstrating small efficiency fluctuation over the required output voltage range at the rated power.