Improved rotor position estimation employing voltage distortion compensation for sensorless PMSM drives at low speed

The PMSM is inherently electronically controlled and requires rotor position information for proper drives. However, the problems of the space, cost, and reliability of rotor position sensors have motivated research in the area of position sensorless PMSM drives. Numbers of rotor position sensorless control techniques have been proposed for PMSM drives, but most rely on the estimation of the rotor flux linkage vector. The performance of this method, however, is poor at low speed region due to the voltage distortions caused by the nonlinear behavior of a pulse width-modulation (PWM) voltage source inverter (VSI). In this paper, a new online voltage distortion compensation method is employed to overcome this problem. To prove effectiveness of the voltage distortion compensation method to the improvement of the rotor position estimation, the proposed method is applied to PMSM drive system and implemented in a digital manner using a digital signal processor.