An improved PWM technique for AC choppers

A novel pulse-width-modulated (PWM) control technique for AC choppers is proposed that has the advantages of enabling linear control of the fundamental component of the output voltage and complete elimination of its harmonics up to a specified order. Theoretical comparisons are made with other basic PWM techniques, and the computed performance indicates the superiority of the present method. The carrier wave required for the new technique is easily determined as a modification of a basic triangular wave that enables these beneficial features to be obtained over the full range of chopper operation and can be implemented by the storage of relatively simple control equations. An experiment has verified the feasibility of the method as applied to the control of a single-phase automatic voltage regulator. In the experiment, the modified triangular carrier wave is used to generate the required PWM switching function. Good agreement is obtained between the calculated and experimental results