DC Bias Study for DC-DC Dual-Active-Bridge Converter

For the dual-active-bridge (DAB) converter, the adoption of high-frequency transformer provides galvanic isolation, but also brings the possibility of dc bias. In this paper, the calculation methods for dc bias are derived in details. Hence, the dc bias magnetizing current can be predicted considering the inconsistency of semiconductor switches and driver signals. In other words, if the maximum permitted dc bias of the transformer is given, the range of the inconsistency of semiconductor switches and driver signals can be obtained. This can provide the guidance for the selection of semiconductor devices and design of the transformer. Then, extra flux balancing method can be avoided and the overall cost and volume will be reduced further. The experimental results show great agreement with the theoretical analysis.