Synchronous undermodulation control modes of system with three PWM converters

This paper is focused on the operation analysis of transformer-based ac drive system with three modulated converters connected specifically to windings of power transformer. It provides multilevel voltage to induction machine by means of three sets of converter-side windings of power transformer. A special switching scheme has been disseminated for adjustment of converters, insuring synchronization of its output voltages and symmetry of voltage waveforms. The total harmonics distortion factor and weighted total harmonic distortion factor have been determined and compared for the basic voltages of this installation. The system performance with three techniques of continuous and discontinuous pulsewidth modulation (PWM) has been evaluated with accent on comparative study of voltage distortion on the converter-side windings of the transformer.