Identification of dynamic model parameters for ultracapacitor used in electric vehicles

An improved equivalent circuit model for ultracapacitors used in electric vehicles (EVs) and the parameters estimation method for the model are proposed. The improved model, with perfect stable and dynamic characteristics according to the physical properties, was consisted with a self-discharging resistance to simulate real-time characteristics of the ultracapacitor. Furthermore, the extended Kalman filter (EKF) was employed to identify the parameters of the model. Finally, the proposed model and parameters estimation method were verified and evaluated by simulation experiments and bench tested under the custom dynamic conditions. The results show that the improved model can well simulate the non-linear dynamic charge and discharge conditions and well demonstrate the self-recovery voltage behavior afterwards, and with a high accuracy.