Abstract
A developed control strategy for firing instances in pulse-width modulated ac voltage regulators is presented. In this type of regulator, output voltage is controlled by varying the on/off time ratios of a series controlled switch. Using a microprocessor as a controller makes it possible to vary firing instances at will according to a predetermined timing regime. One of these regimes is proposed by this paper by adjusting firing instances such that selected dominant lower order harmonics can be eliminated. This in turn leads to improved system power factor and efficiency.