SOC Equalization Control Method Considering SOH in DC–DC Converter Cascaded Energy Storage Systems

Shixian Bai, Xiangqian Tong (), Xin Ma and Jie Zhou
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Shixian Bai: School of Electrical Engineering, Xi’an University of Technology, Xi’an 710048, China
Xiangqian Tong: School of Electrical Engineering, Xi’an University of Technology, Xi’an 710048, China
Xin Ma: Xi’an Weiguang Energy Technology Co., Ltd., Xi’an 710075, China
Jie Zhou: School of Electrical Engineering, Xi’an University of Technology, Xi’an 710048, China

Energies, 2024, vol. 17, issue 24, 1-16

Abstract: In large-scale industrial and commercial energy storage systems, as well as ground power station energy storage systems, the trend is to adopt large-capacity battery cells to reduce system construction costs. It is essential to screen the consistency of battery cells during the initial design phase. In conventional energy storage systems, battery clusters utilize multiple batteries connected in series, which can lead to differential attenuation over time and inconsistent state of charge (SOC) among the batteries. The “barrel effect” diminishes the effective capacity of the energy storage system. To mitigate this issue, a DC–DC converter cascaded energy storage system has been developed, incorporating precise charge and discharge management for each battery module within a cluster. By implementing SOC equalization control at the module level, it mitigates the barrel effect and enables full utilization of each battery module’s charging and discharging capabilities, thereby enhancing the overall charge–discharge capacity of the energy storage system. However, when considering only the SOC equalizing factor, its effectiveness may be limited by constraints such as DC–DC converter power limitations and device voltage stress levels. Therefore, a novel SOC equalization control method that considers both SOH and SOC variations across battery modules is proposed here. Through a droop control methodology combined with closed-loop control implementation on eight DC–DC converter cascaded energy storage systems, we validate the improved effectiveness achieved by incorporating SOH-aware SOC equalization control. The energy storage system has the capability to enhance both charging and discharging capacities, achieving a remarkable increase of 1.85% every 10 min, thereby yielding significant economic advantages.

Keywords: droop control method; DC–DC converter cascaded energy storage system; SOC equalization control; SOH (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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