Full wave modulation applied to 3-level FC and NPC inverters

The multi-level converters are more and more used for high power medium voltage applications. They seem to be the best option to reduce the weight of the converter and still have high efficiency. However, they should be used with an adapted control strategy to reduce their power losses that could be high due to the used high switching frequencies and also to improve the output harmonics quality. The commonly used PWM strategy can lead to high switching losses and less output harmonic content in comparison with full wave modulation. This paper aims to explain the limits of PWM modulation for our application and the advantages of full wave modulation adapted to multilevel converters. These control strategies will be compared for 3-level FC, and 3-level NPC topologies and their effect on the converter weight and performances will be studied to find the most interesting solution regarding specific power and inverter efficiency.