Comparison Among Various Approaches for the Optimal Feedback Control of Induction Motor Drives

Abstract The application of optimal control techniques to drives using as an actuator a frequency controlled induction motor makes it possible to impose suitable restrictions on the stator current and flux, so to have a good operation both of the motor and of the static converter supplying the motor. An approach to this problem consists of its subdivision in two control loops: an outer one giving the required value of the motor torque and an inner one that forces the electromagnetic circuits of the motor to produce the desired torque. This second control loop is the more difficult to be synthetized. The paper takes into consideration several different approaches to the optimal tracking problem for the electromagnetic state variables of the motor. The main peculiarities of the different approaches are described, the obtained control solutions are presented and their performances and computational difficulties are compared by simulation. Also the implementation problems of each solution on a microcomputer-based system are evaluated.