Three-phase Bidirectional DC-DC Converter with Enhanced Current Sharing Capability

Current unbalance is an important issue in multiphase dc-dc converters. In this paper, three types of three-phase bidirectional dc-dc converters are introduced. Comparing to other two types of converters, the Y-connection type converter reduces the current mismatch significantly due to the inherent current sharing capability. To additionally alleviate current mismatch, a small signal method is applied to derive the relationship between phase shift angle and the transformer current. Based on the analysis, a closed loop control strategy and RPC (Ratio Presetting Controller) method are developed to enhance current sharing capability. Simulation and experimental results on a 6 kW prototype are presented to verify the proposed method.