Speed-sensorless direct torque control of induction motors using an adaptive flux observer

This paper presents a new sensorless induction motor drive. The drive uses an adaptive flux observer for speed estimation and the discrete-time direct torque control technique for torque and stator flux control. The adaptive flux observer uses a mechanical model to improve the behavior during speed transients. The estimated stator flux of the adaptive observer is used in the discrete-time direct torque control method to provide fast torque response combined with torque-ripple-free operation over the whole speed range. The sensorless drive system is capable of working from very low speed to high speed and exhibits good dynamic and steady-state performance. The steady-state and dynamic performance of the proposed sensorless drive using simulation and experimental results are demonstrated.