Speed sensorless control for three-level inverter-fed induction motors using an Extended Luenberger Observer

This paper proposes an extended Luenberger observer (ELO) for speed sensorless vector control of induction motor drive fed by a three-level neutral point clamped (NPC) inverter. Two simple methods for observer gain selection are proposed, which eliminates the speed dependent items and decreases the relevant errors caused by observed speed. Conventional speed adaptive observer observes only flux and speed, while ELO observes not only flux linkage and rotor speed, but also load torque, which makes use of mechanical model and more smooth and accurate speed estimation is obtained. Both simulation and experimental results are presented to validate the effectiveness of ELO proposed in this paper.