Dual Active Bridge (DAB) converters have many advantages, such as the ability to transmit power in both directions and are becoming increasingly popular in energy storage systems such as microgrids. However, the input-output voltage conversion ratio must be equal to the turn ratio of the magnetic transformer, and failure to meet this requirement results in poor power efficiency at light loads. Hard switching has attracted attention as the cause of this power efficiency deterioration. However, previous studies have not addressed the fact that part of the copper loss in phase control is a fixed loss, which causes efficiency deterioration at light loads. Therefore, in this paper, we proposed a triangular current control in buck mode and trapezoidal current control in boost mode, respectively and analyzed them using the extended state averaging method. With these controls, hard switching and copper losses were improved.
