An improved CSI fed induction motor drive for medium voltage applications

CSI fed induction motor drives are employed in medium voltage high power applications. One of the major limitations of these drives is the injection of current harmonics into the source, due to the presence of fully controlled ac to dc converter at input stage. There is an increased demand by the industry to modify these drives to meet IEEE 519 standards. This paper proposes a novel CSI drive, in which two identical multilevel inverters are used as active filters, one at the input end and another at the motor terminals, with common dc bus. The active filter at input end provides necessary active current to maintain dc bus. Such an arrangement will ensure sinusoidal input current, sinusoidal motor current and motor voltages. Since the active filter has very high bandwidth, it will be possible to meet the harmonic specifications as per IEEE 519 standards. The proposed drive is simulated and the results are presented. The experimental implementation is in progress. The proposed configuration promises a better alternative compared to other conventional methods like use of passive filters or multi pulse rectifiers at the input stages in terms of cost and performance.