State of charge balancing after hot swap for cascaded H-bridge multilevel converters

In battery supplied multilevel converters it is a common problem to maintain the energy balance between the energy storage placed in different modules. Large unbalance between the state-of-charge (SoC) appears when a damaged battery module is exchanged, and with high probability the newly inserted battery module has different SoC than the other modules. In case the unbalance is large it takes long time to equalize the modules SoC. In this paper a method to minimize the time used for the balancing is proposed. The proposed method is an extension of the nearest level control with sorting and selection based balancing, thus, it can be implemented as an addition to the nearest level control method.