EV Hybrid Battery with Integrated Multilevel Neutral-Point-Clamped Interfacing and Lossless Module State-of-Charge Balancing

The battery is at the heart of the electric vehicle and determines many of its key performance features. Hybrid batteries, combining two battery cell chemistries, benefit from the particular strengths of each battery cell technology, such as high specific energy or high specific power. This paper proposes a novel hybrid battery configuration where the interfacing between the two sets of cells is accomplished through a bidirectional multilevel neutral-point-clamped dc-dc converter. The novel topology is presented and a suitable power converter modulation and control are developed. The feasibility and benefits of such configuration are demonstrated and illustrated. In particular, the proposed battery system features a lossless intermodule battery state-of-charge balancing within both sets of battery cells. Simulation and experimental results are provided in the case of the three-level internal battery interfacing to verify the good performance of the proposed hybrid battery configuration, modulation, and control.