A Visual Method to Compare Balancing Algorithms for Modular Multilevel Converters Integrating Batteries

This paper proposes an intuitive methodology to evaluate the performance of the balancing algorithms for modular multilevel converters integrating battery energy storage systems at the submodule level. Their internal balancing operation can be achieved by injecting AC and DC circulating components to balance the converter arms and legs. The suggested technique exploits the space vector representation to decouple the AC and DC balancing operations. In this way, a dynamic vision of the internal converter imbalance is obtained, and the individual contribution of each circulating current component can be evaluated. The proposed methodology is applied to the two most used balancing algorithms, taken from the literature, showing their strengths and weaknesses.