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In this paper, the direct torque control (DTC) for a three-level five-phase inverter-fed five-phase induction motor is proposed to improve the low-speed performance. The classical DTC scheme (DTC-I) is modified in order to minimize the demagnetization effect during a low-speed operation. According to the modification, the voltage vector space plane is divided into 20 sectors, each of sector 18°. For odd number of sectors, ${{\pm 36^\circ }}$ displaced intermediate voltage vectors, and for even number of sectors, ${{\pm 36^\circ }}$ displaced main voltage vectors are selected instead of classic ${{\pm 72^\circ }}$ displaced voltage vectors. The zero voltage vectors are omitted in the proposed DTC scheme (DTC-II) for the low-speed operation. The DTC-II scheme reduces the demagnetization effect during a low-speed region at the cost of increase in the torque ripple due to avoiding zero voltage vectors. As the speed ramps up, the ${{\pm 72^\circ }}$ displaced voltage vectors are selected through a seven-level torque comparator and are divided into ten sectors. Therefore, in the medium and the higher speed region, the torque ripple is reduced by using the seven-level torque comparator. Simulation and experimental results are presented in order to validate the DTC-II method. [ABSTRACT FROM PUBLISHER]

This paper presents a simplified implementation technique for direct torque control (DTC) of asymmetric six-phase induction motor drive. Current harmonics of fifth and seventh order are observed in the phase currents if conventional DTC scheme is extended for the asymmetric six-phase machine. These harmonic components are not responsible for torque production, thus causing losses in the motor winding. Synthetic vectors are generally used for reduction of current harmonics. Average voltage in $xy$ subspace is maintained to zero by synthetic vectors leading to reduction of currents in $xy$ subspace. A simplified method of implementation of synthetic vectors is proposed in this paper, which eliminates the need for designing of switching sequence and requirement of field-programmable gate array. Also, the number of synthetic vectors that can be possibly produced is increased compared with the ones developed by techniques available in the literature. The experimentation is carried out on a laboratory-developed prototype and the experimental results are presented in this paper to verify the proposed scheme. [ABSTRACT FROM PUBLISHER]

This paper proposes two direct torque control (DTC) strategies to reduce the common-mode voltage (CMV) in the five-phase induction motor driven by three-level five-phase inverter. In each technique, 31 voltage vectors consisting of 30 nonzero voltage vectors, and a zero voltage vector are selected out of available 243 voltage vectors. The selection of these voltage vectors are based on their capabilities of reducing the CMV, eliminating the x–y stator flux and maintaining the torque ripple under control. The ten large, ten small, and a zero voltage vector are same in both schemes, however only difference in designing the control strategy for the two schemes is the utilization of different ten medium voltage vectors. First proposal (DTC-I) reduces the CMV to $3V_{{\rm{dc}}}\,/ 10$ and second proposal (DTC-II) reduces to $V_{{\rm{dc}}}\,/ 10$. These schemes are compared with DTC technique of five-phase induction motor fed by two-level five-phase inverter in order to judge the capabilities of proposed schemes in context of reducing the CMV. The simulation and experimental results validate the proposed DTC techniques. [ABSTRACT FROM AUTHOR]

In a switching-table-based direct torque control method (ST-DTC), the torque ripple reduces with increasing number of levels of the torque comparator. The number of levels is decided by the availability of the number of voltage vectors according to the topology of the inverter. This paper proposes the seven-level torque comparator to reduce the torque ripple in the DTC-controlled five-phase induction motor fed by the three-level five-phase inverter. In the five-phase induction motor, an elimination of x − y stator flux is inevitable otherwise the stator phase current will be distorted. In order to eliminate the x − y stator flux, the virtual voltage vectors are formed. Experimental results are presented to validate the proposed DTC method. [ABSTRACT FROM PUBLISHER]