An Optimized Carrier-Based PWM Method and Voltage Balancing Control for Five-Level ANPC Converters

Abstract

Five-level active neutral-point clamped (5L-ANPC) converter is an attractive topology, which is suitable for medium-voltage high-power conversions. Both phase-disposition pulsewidth modulation (PDPWM) and phase-shifted PWM (PSPWM) can be used to control this converter. PDPWM has the best harmonic characteristics, but the conduction and switching losses are not uniformly distributed. Although PSPWM has the natural voltage balance ability for flying-capacitor cells, its quality of line voltage is much worse than PDPWM. In order to combine the advantages of these two modulation methods, an optimized carrier-based PWM method for 5L-ANPC converters is proposed in this article, which features the same harmonic performance with PDPWM and the same control characteristics with PSPWM. An optimized neutral-point potential balance method is also proposed, which can make a tradeoff between the neutral-point potential balancing and the harmonic performance. Simulation and experimental results demonstrated the feasibility of this method.