배터리 임피던스 변화를 반영한 확장 칼만 필터를 기반으로 한 배터리 SOC 추정에 관한 연구

Abstract

The state of charge(SOC) of battery should be accurately estimated because it is used as basic data for various functions of the battery management(BMS) as well as the remaining battery capacity. Extended Kalman Filter(EKF) based on a battery model is widely used as a real-time SOC estimation technique. However, the parameters of battery model are slightly different for each SOC section and changed by C-rate. As a result, if the battery parameters are used a fixed value, the accuracy of SOC estimation using EKF is decreased. In this paper, to improve the accuracy of the SOC estimation using EKF, the changes in battery parameters according to C-rate were analyzed for five SOC sections. Also, the accuracy of the SOC estimation according to the number of SOC sections was calculated by simulation. Experimental results show that the battery parameters reduce as C-rate increases. In addition, as the SOC decreased, the internal resistor R<SUB>i</SUB> and loss resistor R<SUB>d</SUB> increased, but the double layer capacitor C<SUB>d</SUB> decreased. Therefore, in order to increase the accuracy of SOC estimation using EKF, it is necessary to reflect the changes in battery parameters in each SOC section according to the C-rage. This was verified by simulation.