Stator resistance estimator for direct torque control of permanent magnet synchronous motor drive systems using multi-resolution analysis wavelet

This paper presents an innovative technique for stator resistance estimation of direct torque control permanent magnet synchronous motor based on multi-resolution analysis wavelet PI controller. The online stator resistance estimation employed adjusts precisely the stator resistance value relatively to the evolution of the stator current estimation error gradient to avoid the drive instability and ensure the tracking of the actual value of the stator resistance. The multi-resolution wavelet PI controller implemented for the three level wavelet decomposition is computationally far simpler as compared to the multi-resolution technique with separate computations for high and low pass filtering at each level of decomposition. Also it is prominent by less number of tuning constants and less tuning effort as compared to a standard multi-resolution wavelet controller. The simulation results show that the proposed method can reduce the torque ripple and current ripple, superior to track the actual value of the stator resistance for different operating conditions.