A Transient Characteristics Improvement Method in Dual Active Bridge Converter with Multilevel Inverter Topology

Abstract

In the operation of the dual active bridge (DAB) converter, reducing the DC offset current, which causes magnetic saturation, is critical when phase shifts change. In other words, reducing the DC offset current is necessary to improve the transient characteristics. This paper proposes DC offset reduction methods applicable to DAB converters with multilevel inverter topology. DC offset current reduction methods determined by the phase shifts command for the transient state are discussed. The proposed method is consists of the following elements: adjustment of the phase between the legs of the active bridges, adjustment of the phase between the active bridges, and voltage polarity at phase adjustment. The simulations and the experiments verified the effectiveness of the proposed reduction methods. As a result, under the simulation and experimental conditions conducted in this paper, the peak values of the inductor current moving average in a period of AC voltages were lowered to 4.79 A and 1.6 A, respectively, using the proposed method.