Design consideration of efficinecy improvement in three phase dual active bridge converter for LVDC application

To increase the efficiency of the three-phase dual active bridge (DAB) converter for low voltage direct current (LVDC) system, the design consideration based on performance analysis is proposed. The three phase DAB converters are widely used in high-power applications requiring bidirectional power conversion. This is because the three phase DAB converter has not only capability of zero voltage switching (ZVS), but also a lower conduction loss than a single-phase DAB converter. However, for high voltage/high power applications such as LVDC system, IGBTs are mostly used as active components, fading the one of merits of 3-phase DAB converters, ZVS, causing high switching losses. In addition, in a 3-phase DAB converter, the conduction losses increase due to the high circulating current under high load conditions. In this paper, the effective design consideration of coupling inductance is proposed based on the operation principle of the three phase DAB converter. By designing the coupling inductance, the IGBT turn-off current and the phase RMS current can be reduced to overcome the above disadvantages. Experimental results demonstrate the practical feasibility and the effectiveness of the proposed design method of three phase DAB converter through the 5 kW prototype.