A Critical Review on State-of-Charge Balancing Methods in Multilevel Converter Based Battery Storage Systems

The use of multilevel converters (MLCs) in battery storage systems (BSSs) has increased significantly among researchers in the past decade. Electrochemical differences in battery cells may cause state-of-charge (SOC) imbalances in a MLC based BSS. As a result, capacity and efficiency of BSS reduces drastically. Hence, SOC balancing in MLC based BSS is critical and has received much attention during the past decade. However, previous reviews have only focused on cell SOC balancing in a battery pack rather than SOC balancing in MLC based BSSs. This paper aims to fill this gap in the literature by giving a detailed overview of SOC balancing methods in MLC based BSSs by considering both traditional methods and latest developments in the area. Finally, research gaps and future directives on SOC balancing in MLC based BSSs are included.