چكيده به لاتين
In this thesis, a novel method is proposed in order to simultaneously reduce the flux and torque ripple in Permanent Magnet Synchronous Motor (PMSM) drives based upon the Direct Torque Control (DTC) strategy. The suggested method which is based on the duty ratio modulation employs two other voltage vectors in addition to the initial vector for reducing the flux and torque ripple. These three vectors are applied to the inverter according to their corresponding operating times in each cycle. The time periods of applying these voltage vectors are calculated based on the minimization of flux and torque RMS values and are Simplified only based on the flux and torque errors, no need to use the rotating reference frame and also independent of the machine parameters (except the stator resistance).
The thesis report begins with explanation of the PMSM structure and its mathematical model and then, the DTC method principles are described. Detailed explanation of the proposed method, the procedure of switching frequency reduction, the method used for calculating the duty cycles and also the determination approach of the constant values used in the proposed method are discussed in the remainder of the report. In order to verify the performance of the proposed method, this three-vector strategy, and also the previous two-vector and the conventional direct torque control methods are simulated in the MATLAB/Simulink environment. The results are obtained, analyzed and compared for a sampling period of 50μs and switching frequency of 3.3 kHz, in different conditions such as sudden changes in torque and speed (with a negative final value), a one-percent value of the nominal speed and also the increase of the stator resistance value. Finally, the results are summarized and also several recommendations are presented.
