Direct estimation of stator flux by a MRAS observer in sensorless application

The stator flux estimation is the framework of direct torque control technique (DTC) method. The accurate estimated flux grantees the desirable sensorless drive function. There are different methods for flux estimation that the voltage model is simplest ones. These methods are sensitive to the stator resistance; therefore have poor performance and incorrect estimated flux at very low speed. In this paper a novel flux estimation method is proposed based on model reference adaptive system (MRAS). In the proposed MRAS method the equations of the reference and adaptive models are based on stator current. Traditionally, MRAS observer is used for estimation different parameters such as rotor speed and resistances. Now in novel technique the stator flux is directly estimated from a MRAS observer. The proposed method is less sensitive to the stator resistance so has proper performance at the low speed operation. The robustness and the dynamic performance of the proposed observer are evaluated by simulations.