A Comparison of PI-Based and Sorting-Based State of Charge Balancing Methods in Cascaded H - Bridge Converters

In the operation of battery energy storage systems (BESSs) based on cascaded H-bridge (CHB) converters, balancing the state of charge (SoC) among the sub modules (SMs) within each phase arm is important to utilize their full energy capacity. Multiple methods have been proposed to balance the SoC. The mainstream methods are classified into two main categories, i) those based on proportional and integral (PI) controllers, and ii) those using a sorting stage. This paper compares the SoC balancing capabilities of the two different methods and provides a guide to choose the appropriate method according to the system specifications.