A Novel Analysis, Design, and Optimal Methodology of High-Frequency Oscillation for Dual Active Bridge Converters With WBG Switching Devices and Nanocrystalline Transformer Cores

With the fast development of advanced switches and magnetic cores, high-frequency oscillation (HFO) caused by high dv/dt of fast switching devices and stray capacitances of transformer in dual active bridge (DAB) presents a significantly challenge. In this article, a comprehensive analysis, design, and optimal methodology of HFO for DAB with wideband gap (WBG) switching devices and nanocrystalline transformer cores is proposed. The stray parameters equivalent circuit of DAB is built and the key influencing factors to mitigated the HFO are identified by establishing a time-domain analytical model. Based on the theoretical analysis, this article points out for the first time that the traditional method of decreasing the stray capacitance of the transformer to eliminate HFO is not suitable for high dv/dt occasions when using WBG switching devices. Correspondingly, a novel elimination method of HFO by equating the voltage changing time of dv/dt to the oscillation cycle is proposed, through which the minimum voltage spike amplitude (VSA) of HFO can be achieved mathematically. A 6.6-kW DAB prototype with three different transformers is developed and an approximately 95% reduction of the VSA can be achieved when the proposed HFO elimination method is adopted, which verifies the effectiveness of the proposed method.