Drive converters with the synchronized pulsewidth modulation during overmodulation

This paper presents detailed analysis of the synchronized overmodulation control modes for standard voltage source inverters for adjustable speed ac drives. Two basic versions of symmetrical discontinuous pulsewidth modulation (PWM) for control of inverters in the zone of overmodulation have been analyzed in the paper. It provides smooth shock-less pulses-ratio changing, and the spectra of the output voltage of inverters do not contain even harmonics and sub-harmonics (combined harmonics) in the overmodulation one, which is especially important for large drive systems. Simulations show, that linearity of the fundamental voltage during overmodulation is much better for the algebraic algorithms of synchronized pulsewidth modulation in comparison with the trigonometric ones.