Supercapacitor Stack Active Voltage Balancing Circuit Based on Dual Active Full Bridge Converter with Selective Low Voltage Side

In supercapacitor energy storage tanks where there is a significant difference between the capacitance of cells and which are used at high charging and discharging currents, equalization systems with the ability of high equalization currents are required. Passive equalization methods do not prove practical for such applications, and the solution is sought in active voltage equalization methods. If a voltage equalization system is designed for an energy tank that has a large number of supercapacitor cells connected in series, application of topologies which use converters with transformers for each cell results with a topology with many transformers. If high equalization currents are required, this can significantly raise the price and dimensions of the equalization system. On the other hand, many other active voltage equalization topologies that do not use transformers are not practical for achieving high equalization currents. This paper examines a solution that uses only one Dual Active Full Bridge converter whose low-voltage side can be switched between cells of the supercapacitor module. The equalizing current can be controlled by the converter, and the selective low voltage side selects the cells whose voltage is to be equalized with the voltages of the other cells. Using the simulation model and conducting simulation experiments the functional capabilities and basic characteristics of this voltage equalization system were examined and the advantages and disadvantages compared to the existing equalization methods and topologies are highlighted.