Improved Speed-Sensorless Input/Output Linearisation-Based SVPWM-DTC of IM

In this paper, speed-sensorless input-output linearisation controller (IOLC) based direct torque control (DTC) of induction motor (IM) is implemented in simulation. The switching states of the inverter are determined by the space vector pulse width modulation (SVPWM) method to provide switching conditions with constant switching frequency instead of the lookup table-based conventional DTC method. Thus the torque and flux fluctuations, total current harmonic distortions and switching loss are decreased. In this drive system, IOLC is used instead of proportional-integral (PI) controller to obtain voltage reference vector of the SVPWM. In order to increase the control performance, an extended Kalman filter (EKF)-based estimator is used for the estimation of stator resistance in addition to stator current, stator flux, rotor mechanical angular velocity and load torque. According to the simulation results, it is understood that the sensitivity of the drive system to stator resistance is eliminated by EKF-based estimator and a very high dynamic control performance is achieved with the accurate estimations of EKF algorithm.