Second-order supercapacitor model and its parameter extraction

In certain cases, the application of traditional measurement techniques and related procedures for supercapacitor parameter extraction in time-domain could be an unnecessarily time-consuming process, which also requires different sets of measurement equipment, commonly expensive. This is a strong motivation for the development of procedures for supercapacitor parameter extraction which complies with the above. One such is presented in this paper. This paper presents a model of supercapacitors based on two parallel RC branches, respectively, as a second-order system described by four parameters. In this paper, we will show that even a very simple second-order model credibly describes a supercapacitor in a dynamic regime of a rapid discharging process. Also, we proposed an improved set of expressions that establish the relations between the supercapacitor parameters and measured quantities as well as the procedure for parameter extraction in time domain. We demonstrated that using a generalised least square method and the provided set of analytical expressions is a powerful and effective tool in supercapacitor parameter extraction from the waveform of supercapacitor current in rapid discharge regime. The validity of the proposed approach, expressions, and obtained parameters was confirmed by comparing the waveforms of short-circuit current obtained by an experiment and a simulation.