Equalization technique utilizing series-parallel connected supercapacitors for energy storage system

Series connection of supercapacitors (SCs) leads to cell voltage imbalance due to individual differences in cell properties. Cell voltage imbalance should be minimized to prolong cycle lives and maximize the available energies of SCs. In this paper, an equalization technique utilizing series-parallel connected SCs, which is considered to be suitable for energy storage systems using SCs instead of secondary batteries as main energy sources, is proposed. The proposed equalization circuit, which requires only SCs and switches as its main elements, utilizes SCs not only for energy storage but also for charge shuttling between adjacent SCs for equalization. The operating principle and experimental charge/discharge performance of the SCs using the proposed equalization technique are presented.