Selective harmonic elimination PWM applied to H-bridge topology in high speed applications

The aim of this document is to discuss PWM strategies on 3-level NPC H-bridge topology. This structure is composed of three cells, each one contains two 3-level NPC legs. In this paper, we present a structure allowing the achievement of 6 kV phase to phase motor voltage and a control strategy that enables to obtain 5 levels on output voltage. However, using asynchronous PWM at high speed use, switching losses in the inverter become too high due to switching frequency which has to be at least 10 times the modulation frequency. Thus, one solution consists in using synchronous PWM with which the number of switching is reduced. Thus, this document proposes a synchronous method to respond to some criteria such as harmonic elimination, voltage level increasing and losses balancing on the two cells legs.