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Levi, E, Aware, MV, Pandit, JK and Nemade, R Direct torque control scheme for a six-phase induction motor with reduced torque ripple http://researchonline.ljmu.ac.uk/4731/ Article LJMU has developed LJMU Research Online for users to access the research output of the University more effectively. Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Users may download and/or print one copy of any article(s) in LJMU Research Online to facilitate their private study or for non-commercial research. You may not engage in further distribution of the material or use it for any profit-making activities or any commercial gain.The version presented here may differ from the published version or from the version of the record. Please see the repository URL above for details on accessing the published version and note that access may require a subscription.For more information please contact researchonline@ljmu.ac.uk http://researchonline.ljmu.ac.uk/ Citation (please note it is advisable to refer to the publisher's version if you intend to cite from this work) AbstractThis paper presents an improved direct torque control (DTC) method for an asymmetrical six-phase induction motor using a two-level six-phase inverter. As is well-known, a simple extension of three-phase direct torque control technique to an asymmetrical six-phase motor, using large vectors only, introduces significant current harmonics of the order 6n±1 (n = 1,3,5,…), which are mapped into the non-flux/torque producing (xy) plane. These harmonics cause only losses in the motor winding as they do not take part in torque production. Hence a number of different improved DTC techniques have been developed in the past for multiphase motor drives. The paper takes one such DTC method as the starting point and improves it further by using the concept of virtual voltage vectors. Developed vector selection algorithm, based on two virtual voltage vectors, requires the information on position of the flux in the auxiliary (xy) subspace and provides stator current quality commensurate with the currently available best DTC algorithm for six-phase drives. However, use of two virtual voltage vectors enables a substantial reduction of the torque ripple, which is achieved by means of a five-level torque comparator. Extensive experimentation is performed and it is shown that the reduction of the current harmonics is in essence almost the same as in another recently developed DTC scheme, based on the use of a single virtual voltage vector. However, the achieved torque ripple reduction, which is verified experimentally, makes the scheme superior when compared to the existing approaches. At the same time, developed scheme retains qualities of conventional DTC schemes, such as simple structure and fast response. Its additional beneficial feature is the easiness of implementation.

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