Multi-Phase Input-Parallel Output-Parallel Dual Active Bridge with Inherent Current sharing and Optimized Integrated Transformer

Input-Parallel Output-Parallel (IPOP) Dual Active Bridge (DAB) system is proposed for high power applications for its inherent current sharing capability due to insensitivity to current imbalance compared to the paralleling switching device method. An integrated three-phase transformer is proposed, and its total volume and power loss are modelled analytically in terms of dimensions of limbs and primary number of turns; a model for three discrete single-phase transformers is developed as a counterpart. Based on the analytical models, optimization design points are highlighted in terms of efficiency and power density, which appears as the optimum curve of designs. A 22kW 650V/460V 100kHz prototype with efficiency of 97.47% is built to verify the theoretical analysis and models. Specifically, the improved efficiency and power density of the integrated three-phase transformer, compared to the discrete single-phase transformers, is verified in the prototypes.