A Novel Hybrid Control Strategy for the Energy Storage Modular Multilevel Converters

In this paper, a novel hybrid control strategy has been proposed for the energy storage modular multilevel converters (ESMMC) to realize a nice current performance and ensure the state of change (SOC) of batteries to be balanced. Firstly, traditional proportional integral (PI) control was used to get the circulating current reference; then an improved model predictive control (MPC) method with the weighting factors being online tuned has been designed to obtain the accessing numbers of the submodules in each phase. Lastly, the conventional sorting method for the SOC balancing was given. Experimental comparisons indicate that this proposed novel control strategy can not only ensure a nice current control performance, but also effectively suppress the circulating current component, and it can save over 39.42% execution time in contrast with the traditional PI method, which is feasible for the digital implementation.