A model based balancing system for battery energy storage systems

Battery balancing is considered as one of the most promising solutions for the inconsistency problem of a series-connected battery energy storage system. The passive balancing method (PBM) is widely used since it is low-cost and low-complexity. However, the PBM normally suffers low-power problems, and the balancing speed is usually unsatisfactory. To solve these problems, a model based balancing system (MBBS) is proposed in this paper. A variable and controllable balancing current can be applied to the battery cells with the MBBS. The balancing current can be much higher than the traditional PBM and most active balancing methods. Additionally, the cost of the main circuits of such an MBBS is lower than that of the traditional PBM. The model based balancing current estimation method is proposed to eliminate the balancing current sensors, further reducing system cost. The experimental platform is established, and the proposed MBBS is experimentally verified. The experimental results show that the maximum balancing current of the MBBS can be as large as 10 A, compared to typically 0.1 A for the traditional PBM. Meanwhile, for the 10 A balancing current requirement, the cost of the main circuits of the proposed MBBS is dramatically reduced compared to that of the traditional PBMs, not to mention the active balancing methods.