An 18-pulse AC-DC converter for power quality improvement in vector controlled induction motor drives

This paper deals with a novel autotransformer based improved power quality eighteen-pulse ac-dc: converter feeding vector controlled induction motor drives (VCIMD's). 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 parameters 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. Laboratory prototypes of proposed autotransformer based 12-pulse and 18-pulse ac-dc converters are developed and test results are presented to validate the proposed design and developed model of the converter system.