Conduction loss reduction of isolated bidirectional DC-DC triple active bridge

DC microgrids host multiple loads and energy resources with different power and voltage levels. Multi-port converters allow a compact and efficient means for multiple interconnecting busses with flexible power routing. One promising multi-port converter is the triple active bridge, which inter-connects three ports utilizing a three-terminal high-frequency transformer. This paper aims at improving the efficiency of the triple active bridge converter by means of conduction loss optimization. The approach exploits multiple degrees of freedom available for converter modulation. The optimization is based on the minimization of the true rms current, differently from other optimization approaches in literature based on the fundamental component only. The approach constitutes of two steps: favorable modulation patterns for efficiency maximization are found first by numerical analysis, and, subsequently, true rms current optimization is performed analytically considering only the identified, most favorable, modulation patterns. The approach is demonstrated considering an experimental converter prototype rated 5.5 kW.