Power flow analysis for 3-port 3-phase dual active bridge dc/dc converter and design validation using high frequency planar transformer

In this paper, an inductor-integrated three-winding shell-type planar transformer is designed and analyzed for three-port dual-active bridge (DAB) dc/dc converters in wye wye-delta connection. The steady-state operation principle of the proposed topology has been studied and design parameters of the isolation transformer are analytically determined. The proposed geometry and design method for the ac-link transformer allows us to integrate a large number of bulky inductors required for three phase DAB operation to the transformer without additional connections and unanticipated parasitic effects. It also considerably simplifies the equivalent leakage inductance circuit model and power flow analysis. This configuration is suitable for high power and high step up/down ratio dc/dc converter applications which requires series and/or parallel combination of converters. The experimental and FEM simulation results from prototypes are presented and it validates the theoretical considerations and feasibility of the proposed approach for isolated dc/dc converter applications such as solid-state transformer (SST).