Distributed online active balancing scheme for battery energy storage system

Focussing on the ineffective operating cycle and potential battery life degradation introduced by traditional energy converter-based balancing techniques, a new distributed online active balancing scheme is proposed. In order to achieve a wider output voltage range, a new distributed converter is presented first, which can operate in boost or buck mode. Then, by regulating the discharge rate of each smart cell proportional to the deviation between its own state of charge (SOC) and the average SOC of all cells, an online linear SOC balancing scheme is presented. An experimental prototype consisting of eight smart cells is developed, experiments in constant resistance discharging mode and dynamic current discharging mode are carried out, and the results demonstrate the successful cell SOC balancing and DC bus adjustment capability of the proposed scheme.