Scott-Connected Autotransformer Based Multipulse AC-DC Converters for Power Quality Improvement In Vector Controlled Induction Motor Drives

This paper deals with the Scott (T) - connected autotransformer based multipulse ac-dc converters feeding vector controlled induction motor drives (VCIMD's) for improving power quality at the point of common coupling (PCC). The proposed twenty four-pulse ac-dc converter is realized on the principle of dc ripple re-injection technique for harmonic mitigation. The proposed ac-dc converter is found capable of suppressing upto 21
^st
harmonics in the supply current alongwith the power factor improvement close to unity in the wide operating range of the drive. The design of the autotransformer is given for the proposed ac-dc converter for making it suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed ac-dc converter.