Microprocessor based harmonic elimination in chopper type AC voltage regulators

A control strategy for firing instances in pulse-width-modulated (PWM) 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, proposed here, involves adjusting firing instances so that selected dominant lower-order harmonics can be eliminated. This in turn leads to improved system power factor and efficiency. The theoretical principles used in evaluating firing instances are described, and experimental results verifying the analysis are presented