Practical design of dual active bridge converter as isolated bi-directional power interface for solid state transformer applications

Abstract

As a bi-directional isolated interface for solid state transformer applications, practical design considerations of a dual active bridge (DAB) converter are proposed by means of a detailed mathematical model based on the converter’s steady state operations. The DAB converter is useful in isolated bi-directional power conversion applications due to high performance, high efficiency, and bidirectional control manner. However, design considerations should be taken into account to overcome the disadvantages of DAB converter, such as low efficiency caused by restricted soft switching capability at light load conditions and high circulating current at heavy load conditions. The practical design considerations of the converter’s power stage will be discussed to maximize soft switching capability and to minimize the conduction losses. In addition, to reduce the current stress of the power devices during a cold start sequence, an effective soft start algorithm will be proposed. Experimental results with a 3.3 kW prototype DAB converter will be given in order to validate the effectiveness of the proposed design considerations.