ASYMMETRICAL PWM TECHNIQUE WITH HARMONIC ELIMINATION AND POWER-FACTORCONTROL IN AC CHOPPERS

This paper describes the asymmetrical pulse width modulated (APWM) con trol technique for single phase ac choppers, which improves the input power factor and eliminates the harmonics of the output voltage up to a specified order. This technique also enables linear control of the f undamental component of the output voltage, The APWM switching pattern s at the specified phase angle are obtained by the Newton-Raphson meth od and can be implemented by a one-chip microprocessor, Theoretical co mparisons are made with conventional PWM technique and the computed pe rformance indicates the superiority of the proposed APWM technique, Pr actical verification of the theoretical predictions is presented to co nform the capabilities of the new technique.