Optimization of PWM technique with partially constant modulating waves

In this paper the waveform quality and overmodulation region voltage-gain characteristic of pulsewidth-modulation (PWM) method with partially constant modulating waves are investigated. Thus the number of switchings in the three-phase inverter decreases by 33% as compared to the classical methods. A PWM version is proposed, in which during an interval of pi/3 intervals only two switchings of the inverter semiconductor devices are performed. This method is different to those known in literature because it assure the necessary corrections of PWM-voltage in order to decrease the inverter output low order harmonics amplitudes voltages. These corrections eliminate the undesirable effects of the modulation wave discontinuities.