Using the Poles Shifting Method in a New Reduced-Order Observer for Direct Torque Control Technique in Induction Motor

In this paper, a new closed-loop stator flux observer based on the voltage model (reduced-order) in direct torque control (DTC) applications for induction motors is proposed. The rule of DTC is based on controlling flux and its angle. Therefore, flux estimation is one of the fundamental issues in this method. Using the conventional open-loop voltage model observers can cause some problems such as, appearing dc offset in output, integrator saturation and incorrect estimation in low-speeds. One of the available solutions for compensating these shortcomings and improving the drive system performance is using closed-loop observers. The proposed observer in this paper is a novel closed-loop reduced-order observer based on shifting poles of its transfer function to the left in the complex plane. The simulation results show that the DTC performance is improved in different operation points, especially in low-speeds and also the observer is able to keep its stability in critical conditions.