Small Signal Modeling of Series-Parallel-Connected Battery Energy Storage System with SOC Balancing Control

This paper presents a small signal modeling method for a series-parallel connected battery energy storage system. In this system, each battery cell is paired with a low-power distributed DC-DC converter, which is then connected in parallel at the output to compose a battery module. The outputs of each battery module are then connected in series to form the whole battery pack. An SOC balance controller is presented to realize the SOC balance between parallel cells within modules and between multiple battery modules within the pack. The stability of the battery system with SOC balancing controller is validated by small-signal model analysis.