Novel bifunctional converter-based supercapacitor energy storage module with active voltage equalizing technology

A bifunctional converter module for supercapacitor energy storage based on an input-series-output-series (ISOS) circuit is proposed in this paper. Compared to the existing topologies, the proposed circuit acts both as a supercapacitor cell voltage equalizer and as an output voltage regulator. During the charging process, series- connected flyback converters transfer energy from fully charged cells to the string via a bypass. Therefore, the fully charged cells maintain the rated terminal voltage, and the charging speed of the rest of the cells increases. During the discharging process, the output voltage of the module can be regulated with the same set of converters. The working principles during the discharging/charging processes are analyzed. The designs of the flyback converter and the control system are presented. A prototype consisting of three submodules is implemented. Experimental results verify the effectiveness of the proposed topology. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.