A Distributed State-of-Charge Balancing Control Scheme for Three-Port Output-Series Converters in DC Hybrid Energy Storage Systems

In this study, a distributed state-of-charge (SoC) balancing control strategy is proposed for output-series, hybrid energy storage, three-port converters (TPCs), to address the problem of SoC and voltage imbalance as well as the power distribution in the series converters. The topology of a single hybrid energy storage TPC is described first. On this basis, a brief analysis on the key operating waveforms with the phase shift plus duty cycle modulation is also presented. The principle of the proposed SoC balancing control strategy for the TPC-based output-series system is then analyzed in detail, including the analysis of battery SoC balancing and supercapacitor SoC self-recovery. By performing generalized averaging modelling, both the output-series converter system model and the control model are established, and the influences of the balancing coefficient on the dynamic behavior and stability of the system are then analyzed. Finally, the simulation validation of the output-series converter system with its SoC balancing control strategy is performed in PLECS, and an experimental prototype of the output-series, hybrid energy storage TPC, is constructed to verify the proposed control strategy in various experimental scenarios.