Asymmetrical PWM technique with harmonic elimination and power factor control in AC choppers

This paper describes the asymmetrical pulse width modulated (APWM) control 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 fundamental component of the output voltage. The APWM switching patterns at the specified phase angle are obtained by the Newton-Raphson method and can be implemented by a one-chip microprocessor. Theoretical comparisons are made with conventional PWM technique and the computed performance indicates the superiority of the proposed APWM technique. Practical verification of the theoretical predictions is presented to conform the capabilities of the new technique