Bidirectional Chopper With Single-Cell Auxiliary Full-Bridge Converter for Onboard Battery Energy Storage System

This article focuses on a bidirectionalchopper with an auxiliary converter for onboard battery energy storage systems. The auxiliary converter is made of single-phase full-bridge cells connected in cascade, which can function as an active power filter. This setup aims to reduce both the switching-ripple current of the inductor (i.e., inductance) and its associated volume. However, using multiple cells could lead to an eventual rise of the converter loss and cost. To mitigate these issues, a single-cell auxiliary converter is proposed. Subsequently, the inductor switching-ripple current, inductor volume, and power loss in the chopper are evaluated. Theoretical analysis shows that the use of single-cell auxiliary converter in the chopper can reduce the maximum switching-ripple current to 4/9 of that the conventional bidirectional chopper under the same switching frequency. Further, the validity of the theoretical analysis and the steady- and transient-state performances of the proposed chopper are experimentally verified using a 2 kW downscaled model. Finally, the efficacy of the proposed chopper is verified through a comparison with respect to the inductor volume, power loss, and efficiency, with the conventional bidirectional chopper, the three-level flying capacitor converter, and the bidirectional chopper with auxiliary converter using three cells.