Dynamic Stator Resistance Adaptation in Sensorless Direct Torque Control of SynRm

Direct torque control (DTC) method controls the electromagnetic torque and flux in AC machines, directly. This method is though immune to machine inductance variations but do get affected by stator resistance changes. Ignoring the stator resistance variation can lead to unstable motor drive operation. This paper proposes a new sensorless direct torque control (sDTC) method for a Synchronous reluctance motor that adapts to stator resistance variation. This is accomplished by adapting to changes in the error between the estimated and reference angles of the current and the stator flux vectors. Importantly, it completely obviates the need of any speed sensor. With the present estimation proposal, the sDTC is made to dynamically adjust to the changes in stator resistance ensuring proper motor performance under different operating conditions involving disturbances. The proposed sDTC approach manages to improves the torque and actual stator flux in the SynRm unlike existing DTC approach that greatly struggles under stator resistance variations and results in unstable operation. The performance of the SynRm with the envisaged sDTC with stator resistance change proposed in this paper is compared with the existing DTC method for a close one-to-one comparison and easy appreciation. Besides, ruggedness of the proposed approach for the SynRm is tested under stator resistance changes, motor speed changes and load disturbances.