A novel modulation for the comprehensive neutral-point balancing in the three-level NPC inverter with minimum output switching-frequency ripple

This paper presents a new modulation approach for the complete control of the neutral-point voltage in the three-level three-phase neutral-point-clamped voltage source inverter. The balancing of the neutral-point is achieved over the full range of converter output voltages and for all load power factors with the minimum output voltage distortion at around the switching-frequency. The simple phase duty-ratio expressions in d-q-0 coordinates that define this modulation solution are presented. The performance of this modulation approach and its benefits over other previously proposed solutions are verified through simulation and experimentation.