Different techniques for real time estimation of an induction motor rotor resistance in sensorless direct torque control for electric vehicle

Four different techniques for rotor resistance estimation in sensorless direct torque control (DTC) are studied and compared. Since input voltage contains harmonics, many available techniques cannot be applied in the DTC. Three of the four above-mentioned techniques are the generalization of the previous methods. The fourth technique is a new one, which is applied by the authors. Speed of motor is estimated based on the governing equations of the induction motor and DTC. The resistance is estimated above rated speeds, which were required in electric vehicles (EV's). Although the four techniques enable to estimate the rotor resistance in real time, the new technique and TE (torque-error) method have some advantages over two other techniques.