Induction motor drive with PWM direct torque control

This paper presents an induction motor drive using a method of direct torque and stator flux control. One disadvantage of the algorithm is a variable switching frequency of a voltage source inverter although it is used a constant period for the direct torque control processing in a digital signal controller. It is difficult to carry out a good filtration of the variable switching frequency; therefore it finally leads to higher level of interference. It is possible to avoid the problem and ensure the constant switching frequency of the voltage source inverter by the application of a pulse-width modulator in the control structure of the induction motor drive. In the paper it is described basic mathematical equations of the direct torque control of the induction motor and it is shown simulation results which confirm theoretical assumptions of the induction motor drive properties.