Harmonic mitigation using 12-pulse AC-DC converter in vector-controlled induction motor drives

In this paper, a novel autotransformer with a reduced kilovolt-ampere rating is presented for harmonic current reduction in twelve-pulse ac-dc converter-fed vector-controlled induction motor drives (VCIMDs). Different transformer arrangements for 12-pulse-based rectification are also studied and a novel harmonic mitigator capable of suppressing fifth, seventh, and 11th (most dominant harmonics) in the supply current is presented. The design procedure for the proposed autotransformer is presented to show the flexibility in the design for making it a cost-effective replacement suitable for retrofit applications, where presently a six-pulse diode bridge rectifier is being used. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed harmonic mitigator. A set of power-quality indices on input ac mains and on a dc bus for a VCIMD fed from different 12-pulse ac-dc converters is given to compare their performance.