Nine-Phase AC-DC Converter for Vector Controlled Induction Motor Drives

This paper presents the design and analysis of a multi-phase system for improving the power quality indices at the point of common coupling (PCC) in vector controlled induction motor drives (VCIMD's). An autotransformer has been designed suitable for producing the nine-phase voltages of same magnitude and having equal phase shift. The proposed 9-phase ac-dc converter is found capable of suppressing upto 17th harmonic in the supply current alongwith the power factor improvement close to unity 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 existing 6-pulse and proposed 9-phase ac-dc converter are also presented for an easy comparison of their performance.