Harmonic analysis of Input Current of Single-Phase PFC Buck Converter

The firing angle control of thyristor full wave ac-dc converters to set the desired DC bus voltage in Uninterruptible Power Supply (UPS) systems have drawbacks of pulsating input current, high harmonic content, low pf, low efficiency and large size of inductors and filters. International standards impose several constraints concerning the electric power quality and harmonic content of the line current in the equipment below some assigned limits. Hence there is a need to reduce the line current harmonics so as to improve the power factor of the system. In many applications, this distortion can be made acceptable with adequate linecurrent THD and PF performance. This paper proposes a PFC buck converter in UPS to set desired DC bus voltage which satisfies the EN61000-3-2 standards. The analysis of harmonic content and observed line voltage and current waveforms of hardware implemented are presented in this paper.