Continuous approach to the direct torque and flux control of induction motor

An approach to the direct torque and flux control of the induction motor is presented in the paper. The main contribution of the work is the direct connection of the torque and flux with the applied stator voltage, which was established with the calculation of the torque and rotor flux derivatives dependant solely on the torque, rotor flux and speed. Instead of indirect control through the rotor and stator, a direct torque and flux control is performed. The difference between the presented method and the classical DTC algorithms is the use of the PWM voltages instead of voltage vectors, which results in the reduced torque and flux ripple. The algorithm could also be described as a direct torque and flux control of the induction motor in rotor field coordinates, where torque and flux are controlled directly instead through the control of the stator current. Any observer or estimator algorithm having the torque, rotor flux, rotor flux derivative, and rotor speed, can be applied to the method. The parameter dependence of the method can be decreased with the use of PI-estimators that replaces the feedback terms of the algorithm. The performance is investigated and verified with simulations and experiments.