Temperature Dependent Charging Algorithm of Supercapacitor Module

In order to increase energy efficiency in distributed energy generation systems, energy storage systems are used. Supercapacitors are one type of energy storage elements whose characteristics include high power density, long cycle life and low energy density. Since they are better suited for usage in high power applications, it is important to consider their temperature in order to avoid overheating and cause irreversible damage. This paper presents a supercapacitor charging algorithm that takes into account its temperature in order to increase energy efficiency. The algorithm is part of a regenerative braking system integrated within an electric railway vehicle. The foundation of the temperature dependent charging algorithm is the supercapacitor's electro-thermal model, which includes forced air-cooling, and its development within MATLAB. The electro-thermal model consists of a supercapacitor's electrical model and thermal model; the electric model's rheostatic loss is the input for the thermal model, which outputs the supercapacitor's temperature. The resulting algorithm outputs the maximum allowed charging/discharging current depending on the supercapacitor temperature, and results in an increase in energy savings, as well as lowering the impact of the light electric railway vehicle's accelerating and braking on the power grid concerning current and voltage peak values.