Analysis on equalization circuit topology and system architecture for series-connected Ultra-capacitor

A three-individual cell direct-equalization circuit is researched in detail by directed graph. This equalizer consists of two basic switch converter topologies and six essential operation modes. Its has reasonable structure topology that can transfer power energy directly from the highest to the lowest by the corresponding switch’s on-off control, whenever what imbalance state among these three cells are. Comparative studies of performances between several equalization circuits are also performed according to speed and structure complexity aspects. Based on the proposed circuit module, a scheme of two-layer equalization system structure is build up for 9 series Ultra-capacitors stack, which can realize cell voltage balance by planning the energy transfer path with reasonable control strategy. Simulation results show that this scheme is effective and can meet speed, efficiency and structure simplification requirements and can be applied to equalize long series-connected Ultra-capacitors or high power density batteries.