Unequal Voltage Sharing Between Super Capacitors

Abstract

Newly developed super capacitor (SC), sometimes referred to as ultra capacitor have very high capacitance values compared with ordinary capacitors making them attractive for energy to rage applications. Due to the low voltage rating of a single cell it is necessary to connect a number of SC modules in a series to obtain a practical voltage rating required for power application. However when connected in series they lead to unequal voltage distributions during several cycles of chargedischarge and over voltage may appear on capacitors and therefore it is necessary to prevent this unbalance and hence to prevent individual capacitors from exceeding its rate voltage due to manufacturer’s internal parameter tolerance. If preventative action is not taken the characteristics of the SC element subjected to a higher voltage could influence its lifespan, its characteristics may change with time and therefore the voltage equalization is necessary. This project has studied the problem of unequal voltages sharing in a series connection of SCs forcing the equal sharing of voltage between two and three SCs.