Parameter Identification for Lithium Ion Supercapacitor Based on a Modified RLS Method

As a kind of renewable energy source, lithium ion supercapacitors have bright prospects in national grids, new energy technologies and tram applications. It has the good features of high energy/power density, extremely low resistance, no demand for maintenance and long cycle life. In this paper, we build up the 2ndorder RC equivalent circuit model, which is based on the Thevenin equivalent circuit model. In order to improve the accuracy and stability, and achieve accurate identification of model parameters, such as OCV, R0, Rp1, Rp2, a variable forgetting factor method is introduced into the traditional fixed forgetting factor recursive least squares method. This provides a basic method and reference for the subsequent state estimation and life prediction of lithium ion supercapacitors. The accuracy of the model parameter identification method is verified by the experimental result.