Highly Efficient Nonlinear Torque Control of Induction Motor Drives Considering Magnetic Saturation and Iron Losses

In this paper, an input-output feedback linearization (IOFL)-based direct torque control (DTC) is proposed for induction motor (IM) drives using the maximum torque per Ampere (MTPA) strategy and full nonlinear IM model. In contrast to conventional IOFL technique, the stability of the proposed IOFL is proven by Lyapunov theory. The proposed method not only provides an appropriate tracking of electromagnetic torque, but also leads to an optimal relation between direct (d)- quadrature (q) axis stator currents. Since both MTPA strategy and IOFL control depend on the IM model, more accurate dynamic modelling including effects of magnetic saturation and iron losses is essential. In this regard, a fifth-order IM model developed based on a full nonlinear model is used in the controller design by considering variations of magnetizing inductance and iron loss resistance in terms of the magnetic current and rotor speed, respectively. The proposed control scheme is validated by experimental results showing a significant reduction in the stator current for a light load compared to the conventional model, in which saturation and iron losses are neglected.