PWM strategies for microprocessor control of variable speed drives

Pulse width modulation (PWM) strategies suitable for inverter based systems are presented. Sinusoidal modulation is reviewed showing the superiority of regular asymmetric sampling over regular symmetric and natural sampling. Results concerning harmonic current minimization, harmonic torque minimization, and harmonic elimination techniques are presented. A technique to develop PWM strategies where different performance criteria are combined is outlined. A modulation process which approximates the characteristics of the harmonic current minimization is given. A method to switch from the PWM mode to the quasi square wave mode with reduced harmonic distortion and negligible transient phenomena is shown.