A Low-Complexity Balancing Technique for Flying-Capacitor Odd-Level Converters

In flying-capacitor multilevel (FCML) converters, it is necessary to regulate the flying-capacitor (FC) voltages to their nominal values using either active or passive means. Many active balancing schemes have been proposed in the literature, which often involve sensing and regulating several FC voltages fed into multiple balancing loops. In this paper, a simplified balancing strategy is proposed for flying-capacitor odd-level converters, in which only odd-numbered FC voltages are sensed and fed into a single balancing compensator that nulls the main source of imbalance in the converter. The approach is further combined with an innovative design provision to improve the closed-loop FC voltage dynamics. The proposed technique is tested in simulations on 5-level and 7-level case studies, and through experiments on a 10 V-to-2.4 V, 200 kHz 5-level FCML prototype.