Abstract
This paper presents an effective scheme to minimize the torque ripples for direct torque control (DTC) of induction motor drives. The switching strategy compares the torque error from a PI torque controller with two triangular waveforms, and then produces a constant switching frequency, which is determined by the frequency of the triangular waveforms and is almost independent of the speed. The gains of PI torque controller are designed based on root-locus plot to guarantee a good convergence of the torque error. In order to examine the performance of the proposed DTC scheme for an induction motor drive, a complete simulation model is developed using MATLAB/Simulink and validated under a wide speed range. The proposed DTC drive is also implemented and tested in real-time using a DSP-DS1102 control board for a prototype 1 KW induction motor. Simulation and experimental results show that the proposed DTC drive exhibits a good dynamic and steady state performances with low torque ripples over a wide speed control range.