A NOVEL POSITION SENSOR ELIMINATION TECHNIQUE FOR THE INTERIOR PERMANENT-MAGNET SYNCHRONOUS MOTOR DRIVE

A new approach to the position sensor elimination of an interior permanent-magnet (IPM) synchronous motor drive is proposed in this paper. The phase inductance of an IPM synchronous motor varies appreciably as a function of the rotor position. This feature is utilized to get an estimate of the rotor position. Analytical equations are developed in this paper for the calculation of the phase inductance of an IPM motor driven by a current-controlled PWM converter with a hysteresis controller. The calculated phase inductance is then used to estimate the position of the rotor using a set of stored data relating the phase inductance and the rotor position. In order to obtain an unambiguous relation between the phase inductance and the rotor position, the phase inductance of phases a, b, and c is calculated during different segments of each electrical cycle. A direct approach to inductance calculation, which is computationally less intensive and gives uniformly good results, is also proposed. Simulation results are presented to show the effectiveness of the new controller, and it is shown that the position error is very small for speed-control applications. A current regulator using constant-frequency switching is also analyzed in order to avoid the random switching of the hysteresis current controller.