Design of Integrated Medium Frequency Transformer (iMFT) for Dual-Active-Bridge (DAB) Based Solid-State-Transformers

Dual-Active-Bridge (DAB) converters (DC-DC, AC-DC and AC-AC) are proposed for Solid-State-Transformers (SSTs). Integrated medium frequency transformer (iMFT) provides a compact magnetic solution for isolated DABs, by eliminating the need for additional inter-bridge auxiliary inductor. A common practice to design the leakage inductance of the MFT is by customizing the core through insertion of core air-gaps/slits, which adds to the fabrication cost. In this paper, a design technique is proposed which can attain the desired leakage inductance value by changing the winding arrangement to increase inter-winding magnetic leakage energy. 2 kW, 225V MFT designs with the conventional concentric winding, as well as, the proposed disjoint winding, are evaluated through FEM simulations. Subsequently, 2 kW MFT prototypes are built for experimental characterization, which show that unlike the conventional concentric MFT design, the proposed MFT design can incorporate the required leakage inductance. Further, some additional simulation results are provided for a 2 kW AC-DC DAB converter, having the same MFT design as per the proposed prototype, which validates the proposed MFT solution.