The State and Parameter Estimation of an Li-Ion Battery Using a New OCV-SOC Concept

Abstract

The open circuit voltage (OCV) is widely used to estimate the state of charge (SOC) in many SOC estimation algorithms. But the relationship between the OCV and SOC can not be exactly same for all batteries. Because the conventional OCV-SOC differs between batteries, there is a problem in that the OCV-SOC data should be measured to accurately estimate the SOC in different batteries. Therefore, the conventional OCV-SOC should be modified. In this paper, a new OCV-SOC that is independent of the battery conditions is proposed. Thus, problems resulting from the defects of the EKF can be avoided by preventing the OCV-SOC data from varying. In this paper, the SOC and battery capacity are estimated using the dual EKF with the proposed OCV-SOC.

State of the Art of Lithium-Ion Battery SOC Estimation for Electrical Vehicles

“…Result shows that the MRSTEKF is faster than EKF and STEKF by 55.34% and 49.51%, and is more precise by 52.66% and 33.88%, respectively [55]. The advanced EKF method has a better performance than generality EKF, KF, and the ampere-hour counting method in terms of effectiveness and dynamic adaptability [96][97][98].…”

“…Because of the advantages of EKF, many researchers have applied this method to the study of battery SOC, such as Lee et al [96], who proposed dual EKF, and Chen et al [97] and Zhu et al [98], who improved the nonlinear battery model with EKF to estimate the SOC of a lithium-ion battery. Compared to other extended Kalman filter algorithms, the strong tracking cubature extended Kalman filter (STCEKF) proposed by Gao et al [54] gave an accurate SOC prediction and faster computational time.…”

A comprehensive review on estimation strategies used in hybrid and battery electric vehicles

“…In [91,92], NN; in [93], adaptive wavelet neural network (AWNN); and in [94], Elman neural network (ENN) methods are proposed to estimate the SOC of lithium ion batteries. Many researchers pay attention to KF [95,96]; and its derivatives broadly such as series Kalman filter (SKF) [97]; EKF [10,[98][99][100][101][102][103][104][105][106][107][108]; improved extended Kalman filter (IEKF) [109]; AEKF [110][111][112][113]; model adaptive extended Kalman filter (MAEKF) [114]; robust extended Kalman filter (REKF) [115]; multiscale extended Kalman filter (MEKF) [116]; UKF [117][118][119]; adaptive unscented Kalman filter (AUKF) [120,121]; sigma point Kalman filter (SPKF) [122,123] and iterated extended Kalman filter (ITEKF) [124]. In [119], a modified battery equivalent circuit model is designed that contains the impact of different temperatures and current rates on the SOC.…”

Online impedance spectroscopy estimation of a battery

“…Open Circuit voltage [4] - [5] SOC is estimated using an OCV and SOC look up table. The OCV maybe estimated using the terminal voltage and battery circuit model.…”