Modeling of Supercapacitor Behavior With an Improved Two-Branch Equivalent Circuit

Abstract

In this paper, an improved two-branch equivalent circuit model with a controlled current source is proposed to describe the real-time charge/discharge and self-discharge operating characteristics of a supercapacitor (SC). First, the self-discharge mechanism of the SC is investigated based on the two-branch model and experimental analyses at the different charge and discharge stages. Furthermore, the controlled current source is introduced into the two-branch model to reflect the self-discharge effect of the SC. On this basis, the recursive least square method is adapted to identify the model parameters. To improve the accuracy of the proposed model, the iterative optimization algorithm is also adapted to optimize the dynamic parameters of the controlled current source. Finally, the improved two-branch equivalent circuit model with the controlled current source is simulated. The simulation results are basically in accordance with the experimental results. The relative error of the proposed model is less than 0.7%. Compared with the conventional two-branch model, the proposed model can not only reflect the SC dynamic behavior during the charge/discharge phase but also better reflect the self-discharge effect of the SC.