Abstract

The application of multilevel converters for exciting permanent magnet machines with low-phase inductance to DC-link voltage ratios facilitates a reduction in high frequency switching harmonics. However, converter non-linearities and, in-particular, on-state device voltage drops, create additional low-frequency harmonics. This paper therefore proposes a generic compensation scheme to accommodate the effects of such converter non-linearities and, in so doing, improve the harmonic quality of the machine phase currents. Experimental results gathered from a prototype 5-level diode clamped converter validate the benefits of the proposed scheme by showing quantitative reductions in low frequency harmonics.