Implementation of a novel full-order observer for speed sensorless vector control of induction motor drives

In this paper, the implementation of a novel speed sensorless vector control of induction motor (IM) drive based on full-order observer is presented. The adaptive full-order observer based on IM equations has been used to estimate stator currents and rotor flux. A novel feedback gains of full-order observer have been proposed to satisfy the stability of the system. The speed is estimated depending on the error between the actual and estimated stator currents. However, the performance of this scheme deteriorates when approaching the zero speed zones because of the effect of the variation of the stator resistance and the problem of the stability. The stator resistance has been estimated in parallel with the rotor speed to compensate the error in estimated rotor speed in the low speed region. Lyapunov’s stability criterion is employed to estimate rotor speed and stator resistance. All gains of all PI controllers have been calculated based on the linearized models of the IM. This paper presents an experimental evaluation of the performance of speed observer when working at very low speed. Synthesis of the controller has been presented. The simulations and experimental results prove excellent steady-state and dynamic performances of the drive system in a wide speed range, especially at very low speeds, which confirms validity of the proposed scheme.