Power quality improvement in load commutated inverter-fed synchronous motor drives

The load commutated inverter (LCI)-fed synchronous motor (SM) drive, also known as commutatorless motor (CLM) drive, is popular in high power applications. Most promising features of these drives include high efficiency, economic operation, flexibility of operation and variable speed in high power range, which led to their applications in blowers, fans, pumps, mill drives for a range of industries as mining, water treatment plants, chemical, paper, textile, cement, rolling mills and petrochemical plants. However, the power quality (PQ) concerns have resulted in a set-back for such applications of these drives. This study investigates various topologies for the mitigation of PQ problems in LCI-fed SM drives using multi-pulse AC-DC converters. A set of hybrid topologies is proposed to feed CLM, which use a multi-winding transformer and diode rectifiers with a chopper cascaded named as -rectifier-chopper-. These topologies improve PQ at AC mains, that is, reduce total harmonic distortion in the input current and correct the power factor. It also presents a basis for selection of a suitable AC-DC converter for PQ improvement at the input AC mains of the LCI-fed SM drives.