Torque ripple reduction in direct torque controlled five-phase induction motor using modified five-level torque comparator

摘要

The five-phase induction motor inherently has the minimal torque ripple. However, when it is controlled by direct torque control (DTC) technique, the torque ripple increases due to the presence of a hysteresis torque comparator. The classical five-level torque comparator is presented in the previous literatures to control the torque ripple. However, this comparator has the drawback of wrong selection of zero voltage vectors inside the inner band on the positive side of the comparator, which enables the torque ripple to increase and dc-link utilization to decrease. In this paper, in order to reduce the torque ripple and to increase the dc-linkutilization, a modified five-level torque comparator is proposed, which selects either medium or small voltage vectors instead of zero voltage vectors inside the inner band on the positive side of the comparator. In addition to torque ripple reduction and improvement in dc-link utilization, the proposed comparator significantly improves the quality of phase current. All the available 32 voltage vectors are selected through the proposed five-level torque comparator based on the location of x–y stator flux in order to eliminate the x–y stator flux so as to obtainreduced distortion in the phase current. By employing all the available voltage vectors, the freedom of utilization of all voltage vectors in the five-phase induction motor DTC drive is availed. The proposed five-level torque comparator is compared to its classical five-level counterpart through simulation and experimental results in order to validate the proposed DTC strategy.