Inter-Submodule Remaining Lifetime Balancing in a Battery Energy Storage System for Extended System Lifespan

Utility-scale battery energy storage systems (BESSs) represent a promising solution to address the intermittent power generation of renewables. Additionally, the cascaded H-bridge (CHB) converter has been identified as an attractive topology for interfacing utility-scale BESS at the medium voltage level. However, remaining life (RL) unbalances among the batteries can be a limiting factor to the CHB-BESS, as the batteries with the lowest RL determine the system lifetime and thus demand earlier maintenance. Although some control methods can be utilized to balance the batteries RL, these control methods will increase the overall degradation of the CHB-BESS. Thus, control methods not accounting for this degradation increase may not extend the system lifespan as much as possible. In sight of this challenge, this paper studies the trade-off between the RL balancing speed and the overall CHB-BESS degradation. Accordingly, a model predictive control strategy is proposed to extend the CHB-BESS lifespan by simultaneously balancing the battery RL and constraining the overall degradation increase. Simulation results have been obtained to verify the proposed method.