Estimation of rotor position and speed of a synchronous reluctance motor for servodrives

The main advantage of synchronous reluctance motors is their structural ruggedness. To retain this advantage in a drive system using such a motor, no position sensor should be used. Instead, it is advantageous to use a software estimator. An effective algorithm is proposed for position and speed estimation based on the motor terminal voltages and currents. In a VSI-fed drive system, the terminal voltages are determined by the DC-link voltage and the switching pattern. Therefore only current sensors are needed. In the proposed method, the position and speed are estimated independently, and the estimation depends only on the measured currents without dependency on any estimated variable. No iteration is involved in the estimation process. Digital simulation demonstrates that the proposed method is suitable for both transient and steady-state operation of the drive system, with any initial position