MRAC based online stator resistance and rotor time constant estimation scheme in sensorless field oriented controlled induction motor drives

An induction motor is the most widely used electric machine in high performance drive applications. This paper presents performance analysis of rotor speed estimation method using model reference adaptive control (MRAC) concept along with online estimation of machine parameters mainly stator resistance information requires especially at low speeds and online tuning of rotor time constant for high performance slip control in indirect rotor field oriented control of induction motor drive. Any mismatch in the parameters value used in machine model and estimation algorithm may lead to the field disorientation causing the coupling between flux and torque producing current. Knowledge of stator resistance is required for the correct operation of speed senseless control of the induction motor in low speed region. Also, slip calculation used in indirect field oriented vector control vary with rotor time constant due to temperature variation of rotor resistance, may distort the field orientation control. Therefore MRAC based speed estimation method insensitive to stator resistance variation and online estimation of rotor time constant is proposed. The proposed method is verified by MATLAB/Simulink software package. A simulation result shows the robustness and accuracy of the proposed method and good speed tracking capability and fast responses have been achieved.