Comparison of natural voltage balancing in three-level H-bridge capacitor- and diode-clamped converters

Reported are the results of simple analytical comparison of natural voltage balancing mechanisms in three-level H-bridge flying capacitor and diode-clamped converters with carrier-based PWM strategies. While the optimal voltage quality of the nearest level switching is obtained for both of them, natural voltage balancing dynamic properties are essentially different. It is shown that a flying capacitor H-bridge converter with appropriate phase-shifted carrier-based PWM delivers much faster natural voltage balancing dynamics, especially, for small DC voltage commands and AC modulation indices. Along with reduced parts (diodes) count, this gives a three-level H-bridge flying capacitor converter a competitive advantage over other three-level H-bridge converter topologies with natural balancing.