Abstract:

The cascaded utilization of batteries is an economic and efficient metho d for handling retired lithium batteries. However, during the process of cascaded utilization, some issues may arise due to the imbalance caused by the simultaneous use of batteries of different ages and conditions, affecting the safe and stable operation of the battery system. This study analyzes the issues of current loops and low battery system capacity utilization caused by the imbalance arising when the batteries prepared for cascaded utilization are directly paralleled. To address these issues, this study proposes a battery system in parallel and a balancing control algorithm based on power converters. In this approach, each battery module is connected to a power converter to form a power module. By adjusting the output of the voltage loop, current loop, and state-of-charge loop, the charging and discharging currents of each battery module are controlled independently, achieving balanced and optimized control for cascaded utilization of batteries. This study provides a detailed analysis of the control strategy and discusses experimental results to evaluate and validate the effectiveness of the proposed balancing method. The experimental test results demonstrate that the proposed balancing control strategy can effectively and stably control the currents of different batteries, ensure balanced state-of-charge parameters between batteries, and improve the overall efficiency of the battery system. Thus, this study promotes the effective cascaded utilization of retired batteries and provides new ideas for implementing balancing control in battery systems. By achieving balanced utilization of batteries, their lifespan can be extended, the risk of system failure can be reduced, and the reliability and stability of the battery system can be improved.

Key words: battery energy storage system, state-of-charge (SOC), charging balancing, power converter, battery cascaded utilization