DC bus balancing control techniques for the cascaded neutral point clamped modular converter

This paper investigates different compensation methods for neutral point potential deviation based on modular multilevel single star neutral point clamped bridge converter. Theoretical analysis indicates injecting an offset for a cell can effectively decrease this deviation, so this research presents different offset-based compensation techniques, and evaluates their output performance. Besides, this research also presents a hierarchical voltage balancing control to efficiently manage the power flow among cells. Laboratory test results are provided to verify their effectiveness.