Synchronized overmodulation techniques for the neutral-clamped inverters

Abstract

The paper presents detailed analysis of the synchronized overmodulation control modes for three-level neutral-clamped inverters with control algorithms which eliminate the common-mode voltages. Two basic versions of discontinuous pulsewidth modulation (PWM) for control of inverters in the zone of overmodulation have been analysed in the paper. The spectra of the output voltage of inverters do not contain even harmonics and sub-harmonics (combined harmonics) in the overmodulation zone, which is especially important for the medium- and high-power systems. Simulations show, that linearity of the fundamental voltage during overmodulation is much better for the algebraic algorithms of synchronized PWM in comparison with the trigonometric ones.