Challenges and limits of extended Kalman Filter based sensorless control of permanent magnet synchronous machine drives

A sophisticated simulator of permanent magnet synchronous machine (PMSM) drive was developed and is used for research into model-based sensorless control strategies. In this paper, we focus on estimators based on the extended Kalman Filter (EKF). The limits and possible improvements of the EKF are investigated using the developed simulator and real data recorded on designed laboratory prototypes of PMSM drives. From the viewpoint of possible improvement of the estimator, the main attention has been paid to the following phenomena: (i) uncertainty of a stator voltage vector (effects of dead-times, non-linear voltage drops on power devices, etc.), (ii) impact of imperfect model discretization, and (iii) impact of unknown load torque. These phenomena are analyzed and the results are used to tune covariance matrices of the EKF via a semi-analytical approach. Theoretical results are verified by experiments made on two developed prototypes of PMSM drive of rated power of 10.7kW and 310W. Finally, this paper summarizes the major limits of EKF and proposes prospective ways for further research leading to reduction of these limits.