A series resonant circuit for voltage equalization of series connected energy storage devices

Abstract

In this paper, a novel cell voltage equalizer using a series LC resonant converter topology is proposed for a series connection of energy storage devices, namely battery, or supercapacitor cells. The objective of the target project is to design an active voltage equalization circuit that is low cost, small in size and achieves a short voltage equalization time. The target application is electric vehicles. Compared to existing solutions, the series LC resonant converter eliminates the complexity of multi-winding transformers and it can balance series connected energy storage devices quickly by transporting energy successively between the lowest and highest charge cell pairs. The circuit operation and a theoretical analysis is provided. Simulation and experimental results are presented for a circuit balancing three supercapacitors demonstrating from an initial voltage difference of 527 mV to a final difference of 10 mV in 900 seconds.