Design and implementation of an improved AC voltage regulator

Abstract

High frequency switching power supplies have become part of electronic equipments to provide regulated DC of desired voltage at a low cost and high efficiency. These power supplies have several advantages over their counterpart the linear power supplies. Main advantages are smaller compact size due to elimination of step down transformer and small filter due to high frequency operation. These power supplies have high efficiency because the regulating device in them works as switches ensuring low device loss. Their output voltage can be controlled for a wide range of input voltage variation by on/off ratio (duty cycle) control. Utility AC voltage fluctuation both momentary and prolonged, affect adversely the domestic, industrial and commercial customers. In this thesis a switch mode AC voltage regulator made of ideal switches and practical IGBT switches have investigated. For generation of switching voltage a commercially available IC chip SG1524B is used, thus circuit is compact and more viable. The same chip is used to regulate the output voltage. A fraction of the output voltage is taken as the input voltage of the IC chip to produce the error signal for controlling the duty cycle if any changes occur in the output voltage. As a result the regulator is maintaining a constant voltage across the load during any change in supply voltage as well as for variation of load. Freewheeling path and surge voltage across switches create problem in the proposed regulator. Snubbers are used for suppressing surge voltage across switches. Proper size of Land C of the input and output filter is selected for improving power factor and hence to reduce the input current to an acceptable limit. From the simulation result it is shown that the input power factor of the proposed regul~tor is above 0.9 and efficiency is above 88%. After simulation the regulator is implemented practically in the laboratory. The comparison of simulation results and:-the results found from practically implemented circuit are also presented in this paper. It is seen that the results found from practically implemented circuit shown a good agreement with the simulation results.