New Parameter Identification Method for Supercapacitor Model

The paper introduces a straightforward procedure for estimating the electrical parameters of a simple, but reasonably accurate, two-branches model of a supercapacitor (SC). The equivalent electrical circuit model includes the voltage and frequency dependence on the SC's capacitance, neglecting the self-discharge phenomenon, so it is mainly devoted to short and mid-term simulations suitable for most industrial applications. The estimation procedure of the electrical parameters starts by analysing the experimental data achieved by a common constant-current discharge test. Such data are used to build a fitting function which is compared with the analytical solution and numerical approximations for the SC's voltage evolution. Thus, initial estimated values of the electrical parameters are obtained through simple relations and are optimised by implementing the least squares method. The procedure is validated after an easy and fast extraction of the optimal parameters of the two-branches model of an SC. Several tests involving a commercial SC have been carried out in Simulink and the results have been compared against experimental data. A good accuracy of the two-branches model in a wide range of constant-current charging/discharging cycles is reported.