Power quality improvement in switched mode power supplies using autoconnected transformer based 9-phase AC-DC converters

Switched Mode Power Supplies (SMPS) of medium power ratings are extensively used in heating, welding and telecommunication power supply applications. Invariably, they use a 3-phase ac-dc converter at the front end. In this paper, different autoconnected transformer-based 9-phase ac-dc converter configurations are designed, modeled and simulated to feed such medium capacity SMPS for improving the power quality indices at the point of common coupling (PCC). The autoconnected transformer is designed suitable for producing 9-phase voltages of same magnitude and having equal phase shift. The proposed 9-phase ac-dc converters are found capable of suppressing up to 17th harmonic in the supply current along with the power factor improvement close to unity at varying loads. A set of power quality indices on input ac mains and magnetic ratings for various autoconnected transformer configurations for this SMPS are also presented so that the best converter configuration can be chosen according to the requirements for a particular application