A hierarchical cascaded multilevel converter with continuous uniform SOC management for battery storage systems

摘要

This paper presents a hierarchal cascaded multilevel converter (HCMC) for continuous uniform SOC operation of battery energy storage for a powertrain system. The proposed HCMC is a combination of half-bridge converters and H-bridge unfolders with the feature of modular design for cost reduction and reliability improvement. Furthermore, continuous uniform SOC operation can be achieved via the proposed topology without adding additional balancing circuits, which guarantees high utilisation and reliability of the batteries. Failed individual battery modules/cells can be bypassed via the converter without bringing down the whole battery system. Detailed hardware implementation is described with a double reference signal-based carrier phase-shifted modulation scheme. Both simulation and experimental results have been carried out to verify the performance of the proposed HCMC with a continuous uniform SOC control strategy.