关键词: 储能系统, 锂离子电池, SOC均衡, 寿命均衡

Abstract:

Lithium-ion batteries can serve as backup power supplies to provide different alternate and direct current power levels for the primary and secondary equipment and communication management of the power system to ensure that the core equipment continues to function normally in emergencies. The parallel energy storage system has higher reliability due to the parallel module backup and can also avoid the barrel effect of traditional series backup power supply. However, the parallel scheme can cause differences in module life due to the inconsistencies between modules. Additionally, differences in voltage distribution within the series-connected batteries can lead to overcharging or over-discharging of the battery cells. Therefore, we propose a multitimescale equalization method for parallel lithium-ion battery storage systems. First, bypass equalization is performed on the single cell within the battery module group with the state of charge as the index to achieve intragroup equalization in the short-time scale of a single charge/discharge cycle. Subsequently, the system is balanced in the long-time scale of life decay through the life equalization between parallel battery module groups. Interestingly, the proposed equalization method can improve the consistency between modules when using a parallel energy storage system, enhance the reliability of parallel modules for mutual backup, reduce the operation and maintenance cost, and improve the efficiency of Li-ion battery use. Furthermore, a simulation model is built to verify the effectiveness of the proposed method under different conditions based on accelerated battery aging experiments to verify the equalization method.

Key words: energy storage systems, Li-ion batteries, SOC equalization, lifetime equalization