P.K. Athul Vijay, Varsha A. Shah, and V.V. Shimin
Electrical vehicle, ultracapacitor, modelling, energy, open circuit voltage, equivalent series resistance
As an emerging technology, the ultracapacitor (UC) accomplishes an important role in electrical vehicle as an energy storage system. The inherent properties of the ultracapacitor such as high power density, longer life cycle, high charge discharge efficiency, high current capability, wide range of operating temperature and voltage will make the ultracapacitor an auxiliary source to act along with the battery in electrical vehicles. The model of the ultracapacitor is needful to simulate the performance of the system to meet all electrical constrains, before implementing in the real hardware system. In this paper, a new methodology named as energy-based parameter identification has been proposed to identify the parameters for the existing three branch model developed by the Zubieta. The methodology developed by the Zubeita is based on voltage-based parameter identification. The energy-based parameter identification methodology provides a more accurate and convenient way of exact time instant calculation for the required branch model parameters identification. Based on the experimental test result, the slope changing point of the UC terminal voltage characteristics is used to identify the model parameters of the UC. This paper also analyses the variation of ultracapacitor equivalent series resistance as a function of initial open circuit voltage, through experimental studies. The simulation results obtained through the newly proposed energy-based parameter identification method have shown an excellent matching with the terminal voltage characteristics of the ultracapacitor obtained in real time charging at constant current.
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