Control of boost unity power factor correction systems

For domestic use, there are numerous switching mode power supplies, composed of a full bridge rectifier with a capacitor filter. It derives a DC voltage from the AC mains and generates a pulsed line current with high harmonic content. This paper deals with a boost unity power factor correction system, which can be added to realise a sinusoidal line current. Two simple and fast DC capacitor voltage controllers are studied and analysed. They are compared in terms of settling time, filtering of twice mains frequency and overshoots of the DC voltage under load transients. The first is based on an integral proportional controller. The second is based on identification of the disturbance and regulation using a pole placement RST controller. The effectiveness of the proposed approach is assessed by simulations and extended to parallel connection PFC systems. A near unity power factor and very low distortion with good output voltage regulation is achieved for variable power applications.