State of Charge balancing control of a multi-functional battery energy storage system based on a 11-level cascaded multilevel PWM converter

This paper focuses on modeling and SOC (State of Charge) balancing control of lithium-ion battery energy storage system based on cascaded multilevel converter for both grid integration and electric vehicle propulsion applications. The equivalent electrical circuit model of lithium-ion battery module is established based on the relationship between SOC (State of Charge) and OCV (Open Circuit Voltage) which is obtained from the battery charge and discharge test curves. A hierarchical control structure is proposed to realize different operating modes. The decoupled current control scheme is adopted to control active power and reactive power independently, and the zero-sequence voltage injection and a sorting and select algorithm are employed for SOC balancing control. The simulation results have been carried out with PLECS Simulation Software and are presented to validate the SOC control schemes.