Comparison of full-model and reduced-model EKF based position and speed estimators for sensorless DTC of permanent magnet synchronous machines

The aim of this paper is to study the use of the Extended Kalman filer (EKF) for sensorless control of a permanent magnet synchronous motor (PMSM) drive controlled by direct torque control (DTC). The main drawback of DTC is the necessity of short sampling period. The challenge for the EKF is therefore the minimization of its execution time. This is achieved by using so called reduced state space model of the drive with only two state variables, the rotor speed and the rotor position. It is proved by simulations and experiments that the EKF with this reduced model has the same performance as the four-dimensional full state space model at much lower computational cost. The sensorless DTC with the reduced model EKF was found to be equal to DTC with the full model EKF in terms of performance and superior in terms of computational cost. All experiments were carried out on a laboratory prototype of the drive with rated power of 250 W.