The Performance of the Frame-Angle-Based Direct Torque Controller for PMSM Drives at Low and Very Low Speeds

This paper extends the performance testing of the frame-angle-based (FAB) direct torque controller (DTC) for permanent magnet synchronous motor (PMSM) drives, which are fed by 3 phi, 6-pulse wavelet modulated (WM) dc-ac power electronic converters (PECs). The performance testing of the FAB-DTC is extended to the low and very low speed operation of PMSM drives. The FAB-DTC regulates the d - q-axis components of PMSM stator voltages (v(d) and v(q)), in response to variations in the load torque and/or drive speed. The adjustments in v(d) and v(q) are created by changing the angle v of the frame spanned by v(d) and v(q). In order to extended the FAB-DTC to low and very low speeds, the changes in v are accompanied by changes in the maximum scale J. The values of J, v(d), and v(q) are used to update or change the reference signals employed by the wavelet modulation to generate switching pulses to operate 3 phi dc-ac PEC. The complete PMSM drive system incorporating the modified FAB-DTC is simulated for a 10-hp PMSM drive system. The performance of the FAB-DTC is investigated for different changes in the command torque for various low and very low speeds. Performance results demonstrate stable, fast, dynamic, and accurate responses, which have minor sensitivity to variations in load torque and/or drive speed.