Abstract:
The input current of uncontrolled diode rectifier with output filter capacitor is non-sinusoidal. The output voltage of controlled rectifier is controllable but the input current is non-sinusoidal. To overcome the problem of non-sinusoidal input current of single phase diode bridge rectifier, various input current shaping and power factor correction [PFC] methods are available. These are Buck, Boost, Buck-Boost, Ĉuk, Sepic, Inverse Sepic or Zeta converter controlled rectifiers. Various Isolated Converters like Flyback, Forward, Push-Pull, Full-Bridge and Half-Bridge converters are also used for the same purpose. A Buck Boost circuit provides output voltage that may be less than or greater than the input voltage. The output voltage is negative with respect to input and input current is discontinuous. For discontinuous input current, filtering needs large size of inductor and capacitor. Switching is possible both at the output and input sides of the rectifier. Both output switched and input switched Conventional Buck Boost Single Phase AC-DC Converters are available in literature. In such converters input current is discontinuous, input current THD is high and input power factor is low. To overcome the problem of discontinuous input current, high input current THD and low input power factor, three AC-DC converter topologies are proposed and studied. These are Output Switched Modified Buck Boost Single Phase AC-DC Converter, Input Switched Modified Buck Boost Single Phase AC-DC Converter (One Switch and Two Inductors) and Input Switched Modified Buck Boost Single Phase AC-DC Converter (One Switch and One Inductor). These three proposed topologies are studied with and without input filter between the source and the rectifier. Comparing various results of the previous and proposed works it is found that for proposed output switched and input switched topologies with one inductor THD of input current is reduced, input power factor is improved and found near unity and efficiency is also improved compared to previous conventional Buck Boost topology based single phase AC-DC converter.
