Comparative Study of the Active and Passive Circulating Current Suppression Methods for Modular Multilevel Converters

Circulating current is an undesirable phenomenon in modular multilevel converter which should be attenuated to reduce current stress and power losses. This letter presents a comparative study of the active and passive circulating current suppression methods. Voltage penalty of the active circulating current control is derived, and design of the passive circulating current filter parameters is provided. Simulations and experiments are performed to validate the analysis.