High-power-density three-phase converter utilizing a balanced-flux transformer core

Abstract

Three-phase architecture is an outstanding option to achieve high power ranges, which in another way are hard to reach with conventional topologies. For a three-phase galvanically isolated topology the core choice for low cost and volume is the three-legged core. Unfortunately, three-legged core has an intrinsic flux asymmetry due to unbalance on the mutual impedances among phases, caused by the core geometry; this phenomenon contribute in detriment of the converter performance. Then numerous corrective strategies have been implemented, but the asymmetry phenomenon still not totally solved. Hence, this work utilizes a singular geometrical balanced-flux core which naturally copes with asymmetry and enhances the overall converter efficiency. Therefore, a three-phase soft-switching dc-dc converter associated with a three-phase wye-wye transformer and a triple version of the hybridge rectifier is proposed. Complete study of the operating stages, balanced-flux core behavior, dynamic analysis and design of a 1.2 kW prototype is presented.