An optimized soft‐start procedure of dual active bridge converter for charging current suppression

Abstract

As a typical topology of solid-state transformer, dual active bridge converter (DABC) is widely used for voltage levels conversion due to its advantage in bidirectional power transfer and galvanic isolation. In the start-up process, an overcurrent will occur when the converter charges the output capacitor. To address this problem, special soft-start procedures are used to protect switches from the inrush current. The soft-start framework used in this paper adds an inner-phase-shift in the closed loop control. Compared to the conventional step-to-step soft-start methods, it simplifies the transition process from the open loop to the closed loop control. However, higher current stress appears in the soft-start process. So, based on the framework, an optimized soft-start procedure with simple implementation, including the phase transformation and the inverse-trigonometric inner-phase-shift, is proposed to improve the voltage tracking performance and reduce the charging current further. The simulation and experimental results confirm the effectiveness of the proposed soft-start procedure on the output voltage control and charging current suppression.