Study of Input Power Factor Correction in Single Phase AC-DC Circuit Using Parallel Boost Converter

An ac to dc converter is t h e m o s t i m p o r t a n t p a r t o f any power supply unit used in the all- electronic equipments that forms a considerable part of load on the utility. Power electronic equipments are increasingly being used for power conversion, thereby injecting lower order harmonics into the utility. As a result, the total harmonic distortion is high and input power factor is poor. Thus, power factor correction schemes are implemented so as to make the power factor unity thereby leading to low input current distortion. Amongst the several techniques used for PFC, high frequency active PFC is used to get better power factor but it has drawbacks that includes additional losses, thus reducing the overall efficiency, increase in EMI. The efficiency is improved by reducing the losses using soft switching techniques such as ZVS and ZCS. Boost converter is preferred because input current does not have cross-over distortion and it is continuous. In this project, a control technique for boost converter is proposed. This is based on hysteresis-control scheme in which two sinusoidal current references are generated namely IP,ref, IV,ref, such that one is for the peak and the other is for the valley of the inductor current. In this control technique, when the inductor current goes below the lower reference IV,ref the switch is turned on and is turned off when the inductor current goes above the upper reference IP,ref, thereby giving rise to a variable frequency control. To avoid too high switching frequency, the switch should be kept open near the zero crossing of the line voltage so introducing dead times in the line current. Thus, we can say that by using hysteresis controlled boost converter PFC , power factor of an AC-DC converter can be increased.