Study on voltage consistency characteristics of lithium-ion battery energy storage system

Abstract

In the long-term operation of lithium-ion battery energy storage power stations, the consistency of batteries, as an important indicator representing the operation condition of the system, needs to be focused. In practice, the parameters of voltage, capacity, and internal resistance are most commonly used for the consistency evaluation of batteries, and voltage is the most intuitive one. In this paper, a real lithium-ion battery energy storage power station is studied, and the consistency of voltages is calculated. The results show that, with the decline of the battery capacity during discharge, the consistency of the battery presents a strong nonlinear characteristic. At the beginning of discharge, the max-min and standard deviation of voltage are only 0.04 and 0.01 V, while at the end of discharge, the max-min and standard deviation of voltage are up to 0.25 V and 0.045 V, respectively. At about 40-50 minutes of the discharge, i.e., when the corresponding voltages are about 3.132 V to 3.176 V, the voltage consistency deteriorates rapidly. Then, this period of discharge is considered as a threshold interval of consistency deterioration of batteries. The results are helpful for system condition evaluation and operation optimization.