Study on direct torque control of permenant magnet synchronous motor following duty ratio modulation with advanced mtpa scheme to minimize torque ripple

Abstract

This thesis studies the mathematical model of Permanent Magnet Synchronous Motor (PMSM), a general idea of the conventional Direct Torque Control (DTC) method, a DTC based on duty ratio modulation, Maximum torque per ampere (MTPA) based duty ratio modulated DTC, and advanced duty ratio modulation scheme combining previous two methods. Space Vector Modulation (SVM) is used to choose the inverter's voltage vectors for various time periods. Look-Up Table (LUT) is used to choose the voltage vectors for various values of torque and flux with various phases. The two approaches discussed above are then used to simulate the PMSM drive in the MATLAB® SIMULINK environment. Then the ripples produced in speed and torque response of DTC with duty ratio modulation, DTC with MTPA based duty ratio modulation and advanced Duty ratio modulation are compared. It is obvious that DTC has a specific drawback because of how much torque and current ripple it possesses. An efficient remedy for this problem is the Advanced Duty Ratio Modulation Technique. The advanced duty ratio modulated approach is preferred for greatly lowering the ripple percentage, according to this thesis work. When there are changes in load, it can also lower the torque ripple.