Design of High Frequency Transformer for a Dual Active Bridge (DAB) Converter

Dual Active Bridge (DAB) converter became very popular among the isolated bidirectional DC-DC converters for high voltage and high power applications due to its high power density and higher efficiency. The high power density is achieved as the isolation is provided with a high frequency transformer (HFT). Apart from the isolation, the HFT participates in the active power transfer through its leakage inductance. In this paper a design methodology is proposed for an HFT, which is suitable for DAB application. A step-by-step procedure is given in a flow chart to design the HFT. The process involves the selection of core, winding, number of turns and the winding arrangements. As a specific leakage inductance is required for a given active power transfer for a DAB, a suitable winding arrangement is proposed in this paper. The detailed loss analysis is carried out in Ansys Maxwell simulation. The proposed design is verified in a hardware prototype of a 48/400V, 1kW HFT with an operating frequency of 50kHz.