Predictive Control of Induction Motor Drive Using Dspace

Since the induction motor drives have gained its popularity among regulated drives area, the great effort is put on increasing their efficiency. The use of predictive algorithm to control their speed is becoming a popular approach that preserves high efficiency. This paper presents implementing predictive control on the dSPACE DS1103 system, where the dSPACE is the control part of the system, drives the outputs of the power IGBTs and provides online communication with computer through ControlDesk. 1 Induction motor drive Induction motors (IM) are nowadays thanks to their simplicity, price, robustness and high reliability the most widely used motors in the area of regulated drives and are displacing DC motors. IM consists of two main parts, the stator and the rotor. The stator is made of a three phase winding circuits and the individual windings are positioned in a way to create a rotating magnetic field when AC voltage is connected to its terminals. The rotor consists of cylindrical core with parallel conductors from copper or aluminum that are short circuited by the end rings. When the stator winding is connected to a 3 phase AC source, it creates a rotating magnetic field at an angular speed of the AC source. As the rotor winding in an induction motor is directly shorted by end ring an emf is according to Faraday’s law induced in the rotor and a current flows through the rotor. The rotor current then creates its own magnetic field. Here the relative velocity between the rotating stator flux and rotor flux is the cause for torque generation. So the rotor will rotate in the same direction to reduce the cause, in this case the relative velocity. Therefore, it can be observed that the rotor can not reach the speed of the stator flux. If the speeds equals, there would be no difference in velocities, so no induction in the rotor and no current would be flowing. Therefore, no torque would be generated. The induction motor can be described by a few sets equations. The equations used for model in this application are provided in [1]. The first two equations describe generation of stator and rotor flux from AC voltage source and from rotor currents respectively. The third and fourth describe linkage between fluxes and currents and the fifth equation describes a torque generated by the IM.