Multipulse improved-power-quality AC-DC convertors for vector-controlled induction-motor drives

The paper deals with polygon autotransformer-based 12-pulse and 18-pulse AC-DC convertors feeding vector-controlled induction-motor drives (VCIMDs) for improving power quality at the point of common coupling (PCC). The design of autotransformers is carried out for proposed AC-DC convertors to make them suitable for retrofit applications, where at present a six-pulse diode bridge is used. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of proposed AC-DC convertors over a wide operating range. Laboratory prototypes of proposed autotransformer-based 12-pulse and 18-pulse AC-DC convertors are developed and test results are presented to validate the proposed design and model developed of the system.