Design and analysis of a single phase single switch cuk and sepic AC-DC converter with improved performance

Abstract

Single phase full wave bridge rectifiers are nonlinear in nature and draws non sinusoidal current from a sinusoidal voltage source. This causes low input power factor and high input current THD and causes a lot of problems in sensitive electronic equipment and high power equipment in power system. There are several methods including passive and active filtering to solve the problem. Passive filtering uses bulky sized inductors and capacitors, while active filtering uses switching mode regulators to improve the input current and power factor. The inductors and capacitors required in active filtering are smaller sized than that of passive filters. Generally, switching is performed in output side of the rectifier, which makes input current high frequency switched. Then a passive filter is used to get low THD and high input power factor. In this thesis, two new topologies of single phase single switch AC-DC converter using Ĉuk and SEPIC conversion is proposed. These converters’ input current is chopped at high frequency during positive and negative cycle by a single semiconductor switch to get step up/step down AC to DC conversion, instead of using a single phase rectifier followed by a DC-DC converter or using a bridge rectifier with two diodes and two switches. Comparison is made between proposed and conventional circuit under same Load and operating conditions. The proposed circuit shows better performance i.e. higher power factor and lower THD than conventional one. The efficiency of these converters is also high. No additional control scheme is required to achieve these advantages. The feedback controller circuits are also introduced to the proposed converters to achieve regulated output voltage. The results after connecting the feedback controller are also presented in the thesis.