State of charge estimation considering OCV hysteresis in lithium iron phosphate battery for UPS applications

In recent years, there is growing interest in improving lithium-ion battery state monitoring. This is due to growing concern over ensuring reliable and safe operation of lithium-ion based energy storage system especially in automotive and stationary e.g. UPS in data center applications. In this paper, battery state of charge estimation based on Extended Kalman Filter (EKF) and improved battery model considering hysteresis is presented. Hysteresis in battery is complex phenomenon and normally not considered in SOC estimation. However, the consideration is crucial especially in lithium iron phosphate (LFP) battery. Simplification of hysteresis in open circuit voltage (OCV) in the battery leads to higher percentage error in SOC estimation. To consider and model hysteresis in OCV, discrete Preisach model (DPM) is utilized to provide satisfactory improvement in SOC estimation.