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. Numerous rotor position sensorless control techniques have been proposed for PMSM drives, but most rely directly or indirectly on the estimation of the rotor flux linkage vector. The performance of this method is poor due to the voltage distortions caused by the nonlinear behavior of a pulsewidth-modulation (PWM) voltage source inverter (VSI). In this paper, the nonlinearity in a PWM VSI is analyzed and a new online estimation method is proposed to compensate the voltage distortion. 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.