A New PWM ControlMethodfor Three-Phase Autosequentially CommutatedCurrentSource Inverters

A newcurrent pulsewidth modulation (PWM)methodis presented which uses theprinciple ofcreating zero three-phase currents at selected instants oftime,through whichtheloadcurrent harmonic content canbecontrolled along withthemagnitude ofitsfundamental content. Thisgives rise toreduction ofmotortorque ripples through the selection ofsuitable PWM patterns andafast current control inthe inverter byvarying thepulsewidths ofthePWM pattern. Underthis new PWM modeofoperation, theautosequentially commutated inverter (ASCI) circuit canbemodified easily sothat ahigher numberofpulses canbeaccomodated within ahalf-cycle, compared tothenormal ASCI circuit. Theexperimental oscillograms verify theeffectiveness ofthenew PWM method.