On the comparison of fundamental and high frequency carrier-based PWM techniques for multilevel NPC inverters

Many different kinds of multicarrier sinusoidal pulse-width modulation (MSPWM) techniques have been used to control the multilevel neutral-point-clamped (NPC) inverter topology. These techniques are the natural extension of the conventional two-level SPWM method. In this paper, some of their characteristics are further explored. Since the switching losses are the most critical factor in selecting the "right" control method for higher power applications, the potential impact of the MSPWM methods on the switching losses is investigated. Moreover, the fundamental frequency PWM (FFPWM) is also considered. By comparing the MSPWM with FFPWM control method with attention to their effects on the total harmonic distortion (THD) of the output voltage and the switching losses, some important conclusions are reported. It is confirmed with simulation results that MSPWM is not necessarily more advantageous than the simple FFPWM control method in many occasions.