Analytic Solutions for Minimum Conduction Loss Modulation of Dual Active Bridge Converters Including Frequency Variation

This paper presents analytic solutions for the calculation of an optimal modulation scheme including frequency variation for a bidirectional single phase dual active bridge (DAB) dc-dc converter used for charging high-voltage batteries of electric vehicles. The proposed modulation scheme facilitates the minimum conduction loss operation of the DAB converter. The losses can be reduced significantly, especially for light- and medium-load conditions. Analytic expressions are derived for a direct calculation of the optimal control parameters. These expressions are verified with a numerical simulation. Moreover, a significant reduction of the necessary computational time can be achieved for the analytic determination.