AC to DC Converter Topology for Improved Power Factor and Lower Harmonics-A Review

Rectifier circuits are being applied in various AC to DC conversion requiring DC supply at load end as the power source is mostly AC. In most electronic power supplies, the AC input is rectified and a bulk capacitor is connected directly after the diode rectifier bridge. This type of utility interface draws excessive peak input currents; it produces a high level of harmonics, and both the input power factor (PF) and total harmonic distortion (THD) are poor. The low PF makes the efficiency of the electrical power grid to be very low. Earlier; the converters were large in size and were expensive as well. A remarkable reduction in size and price was possible due to the invention of switch mode power supply. For a better utilization of the existing electrical energy the entire power system should be operated at high efficiency. At present, various techniques of rectification by using Diode based bridge rectifier, thyristor based bridge rectifier etc. in open loop are available but these techniques have their limitations. Therefore, PWM rectifiers are now being considered This paper reviews the most effective techniques widely used by researchers for improving single phase and three phase converters. This, will aid further study of the inherent research problems associated with harmonic distortion (THD) and power factor correction (PFC) in converters.