Parameter Design for Suppressing Current Distortion Caused by DC Bias in Dual-Active-Bridge Converters

The dual-active-bridge (DAB) converter has been widely used, but the current distortion caused by dc bias has not been well addressed due to the high/medium switching frequency. A conventional DAB converter utilizes an auxiliary inductor to enhance efficiency in normal operation, with the auxiliary inductor typically connected to the primary side of the DAB transformer. However, replacing the original auxiliary inductor with distributed auxiliary inductors, one connected to the primary side and the other connected to the secondary side, can help alleviate current distortion when the magnetic core is saturated without influence on the DAB converter during normal operation. In this article, a numerical calculation method is introduced to simultaneously calculate both the induced voltage and the excitation current of the DAB converter under dc bias. Based on the calculation results, a data fitting-based formula for optimizing the inductance distribution is proposed. The rationale behind the proposed formula is elucidated using mathematical methods. The accuracy of the numerical calculation process is verified by simulation results. The effectiveness of the proposed formula is validated through numerical, simulation, and experimental results.