The analysis and comparison of carrier-based PWM methods for 3-level inverter

This paper provides the analysis and comparison of carrier-based PWM methods for 3-level inverter. Up to now, there were few papers dealing with harmonic characteristics of various modulation indexes in the 3-level inverter. Therefore, the PWM methods for the 3-level inverter need be analyzed and compared. The current harmonics of a 3-level inverter is compared with those of conventional 2-level inverter by the analysis of harmonic voltage vector, and the harmonic currents for various modulators are compared with one another. In addition, we investigate the variation of neutral point current, which becomes an important problem in the NPC inverter, of each PWM method according to the modulation index (MI) and power factor (PF). Finally, with the simulation results, this paper proposes the optimal PWM method according to the modulation index (Mi) and power factor (PF) among the considered methods.