Sensorless Direct Torque Control Research Articles

Sensorless Direct Torque Control of Induction Motors Used in Electric Vehicle

A three-phase squirrel-cage induction motor is used as the propulsion system of an electric vehicle (EV). The motor is controlled at different operating conditions using a direct torque control (DTC) technique combined with a new switching pattem producing low harmonics. The operating flux of the motor is chosen optimally for both loss minimization and good dynamic response. Since speed estimation is sensitive to rotor resistance variations, the rotor resistance value is calculated and modified in real-time continuously. Simulation and experimental results show that the proposed DTC is able to follow the reference speed (which may be only input reference of the system) with a reasonable dynamic and relatively low error.

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 the 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. The 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 (EVs). 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.