A preliminary review of advanced carrier based modulation techniques for three-phase three-level NPC inverter is reported, focusing the attention to double signal and hybrid modulations. The problem of the neutral-point balancing is considered and reference to previous proposals recalled. A general analytical approach for the calculation of conduction and switching losses in NPC 3-level inverter is proposed, emphasizing the role of the adopted modulation strategy on the calculations. Finally simulation results are reported based on the model of a grid-connected three-phase three-level neutral-point-clamped inverter.
