An Integrated Three-phase Transformer for Partial Parallel Dual Active Bridge Converter

In this paper, an integrated three-phase transformer is utilized in the partial parallel dual active bridge (PPDAB) converter. Due to the symmetrical structure, the flux generated by the primary windings is equally distributed to the three outer legs. Given the same number of turns of the windings in each parallel modules, the ac currents can inherently balance in the parallel modules. In order to enlarge the leakage inductor to serve as the interfacing ac inductor in the PPDAB converter, the coupling between the primary windings and secondary windings is weakened by placing the primary and secondary windings on the center and outer legs, respectively. Compared to the discrete three-phase transformers, the winding loss will also decrease with the proposed structure. A 1kW 400V/50V 500 kHz prototype with an efficiency of 96.72% is built and tested to verify the theoretical analysis.