Power Quality Improvements Using Delta-Polygon Connected Autotransformer Based Nine Phase AC-DC Converter

This paper deals with a novel delta-polygon connected autotransformer based improved power quality nine-phase ac-dc converter feeding vector controlled induction motor drives (VCIMDs). The design of the proposed autotransformer is presented alongwith the necessary modifications required for making it suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The proposed ac-dc converter is found capable of improving the power quality indices in the wide operating range of the drive. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed ac-dc converter. A set of power quality indices on input ac mains and on dc bus for a VCIMD fed from various ac-dc converters are also given to compare their performance.