The Active Power Control of Cascaded Multilevel Converter Based Hybrid Energy Storage System

Because of its simple structure, high power quality and enhanced output voltage, cascaded multilevel converter (CMC) has been utilized as the main circuit of power conversion system of energy storage system. However, it is difficult to adapt CMC to hybrid energy storage system (HESS) because of the asymmetric power distribution problem. This paper proposes a novel topology for CMC-based HESS, in which, an LC branch is inserted at the end of cascaded H-bridges as a tuned filter, and an odd-harmonic-hybrid-modulation (OHHM) is further proposed to control the harmonic frequency components to transfer power among different energy storage components through the LC branch. The principle of the OHHM technique and the design of the LC branch are analyzed, based on which, a joint energy recovery and SOC balancing system is introduced. The principle and control method of the proposed HESS is verified by both the simulations and experiments.