Journal of Shanghai University(Natural Science Edition) ›› 2020, Vol. 26 ›› Issue (3): 413-424.doi: 10.12066/j.issn.1007-2861.2048

• Research Articles • Previous Articles     Next Articles

A square root UKF with variable-parameter model for Li-ion batteries SOC estimation method

GAO Wenkai1, YAN Limin1(), SUN Die2   

  1. 1. Microelectronic Research and Development Center, Shanghai University, Shanghai 200444, China
    2. School of Mechatronic Engineering and Automation, Shanghai University, Shanghai 200444, China
  • Received:2018-03-24 Online:2020-06-30 Published:2020-07-07
  • Contact: YAN Limin E-mail:yanlm@shu.edu.cn

Abstract:

The state of charge (SOC) estimation is an important aspect of modern battery management system. Methods based on Thevenin Equivalent model for Lithium Battery such as extended Kalman filter (EKF) have been widely used in SOC estimation. However, there are some limitations in the derivation of Jacobian matrix and linearization. In this paper, a square root unscented Kalman filter (SRUKF) based on variable-parameter model is proposed to estimate SOC, which does not need to linearize the nonlinear model. At the same time, the square root property improves the numerical properties of the state covariance. The variable-parameter model is based on the second order Thevenin model, which makes the parameters of the lithium battery change with the quantity of electricity and reduces the error caused by the fixed parameter model that cannot reflect the change of parameters under different electric quantity. The experiment results show that the proposed method is effective. Compared with the existing SOC estimation method, the EKF, UKF and the estimation results from the fixed-parameter model, the error of this method is obviously smaller than that of the other three methods.

Key words: Li-ion battery, state of charge, variable-parameter model, square root unscented Kalman filter (UKF)

CLC Number: