Comparison of Neutral-Point-Clamped, Symmetrical, and Hybrid Asymmetrical Multilevel Inverters

This paper presents a comparison of three topologies of multilevel inverters applied to drive an induction motor of 500 kVA/4.16 kV rating. The multilevel inverters analyzed are the following: a neutral-point-clamped inverter, a symmetrical cascaded multilevel inverter, and a hybrid asymmetrical cascaded multilevel inverter. The performance indexes used in the comparison are total harmonic distortion, first-order distortion factor, second-order distortion factor, common-mode voltage, semiconductor power loss distribution, and heat-sink volume. The multilevel inverters are designed to present 99% efficiency at the nominal operating point, and the aforementioned performance indexes are compared for distinct values of amplitude modulation depth.