Multilevel boost rectifiers as a unity power factor supply for power electronics drive and for battery charger

Single and three phase boost rectifiers operate with unity power factor and low switching frequency when a multilevel controller is used. A novel structure for multilevel control is proposed. Single phase systems operate mainly as a force commutated rectifier however line commutation is very useful especially for zero crossing supply voltage because, during overlapping, current rate is high and harmonics are reduced. In a three phase system the multilevel control is achieved by using 9 active switches. A method based on a comparison reference and available current rates or comparison voltage drops on supply side inductances is proposed to evaluate the rectifier controllability. Results of simulation and laboratory tests confirm a unity power factor.