A Novel Method for Predicting the Leakage Inductance of the High-frequency Transformer in a DAB Converter Considering Parasitic Capacitance

The dual active bridge (DAB) converter is receiving a lot of attention recently because it can transmit power bidirectionally and exhibits galvanic isolation, high efficiency, and high-power density. Among the elements constituting the DAB converter, leakage inductance is an essential element for transferring power bi-directionally by a phase shift between the primary and secondary switching elements. The input and output voltage of the DAB converter is highly dependent on the turn ratio of its transformer component. Therefore, the characteristics of the DAB converter are determined by the leakage inductance and the turn ratio of the transformer. The DAB converter uses a switching element, such as a MOSFET, which exhibits parasitic capacitance. The parasitic capacitance interferes with the change in voltage and affects the DAB converter output. This paper analyzes the relationship between the output and leakage inductance of the DAB converter, and the turn ratio of the high-frequency transformer. Using the analyzed results, this paper proposes a method for predicting the leakage inductance inside the DAB converter and the turn ratio of the high-frequency transformer. Because the parasitic capacitance of the MOSFET affects the output of the DAB converter, it is considered in order to improve the accuracy of prediction of leakage inductance and transformer turn ratio. The method presented in the paper is verified through experiments and simulations.