Minimal Controller Synthesis Adaptive Control for Direct Torque Controlled Induction Motor Drives

An adaptive speed controller based on the minimum controller synthesis (MCS) algorithm is developed for the direct torque control (DTC) induction motor drive. MCS is an extension of the conventional model reference adaptive controller, but with simpler implementation that does not require information about the plant under control. The proposed MCS controller compares the motor speed with the speed of a reference model and applies a torque reference to the DTC drive accordingly. An additional adaptive term is added to the MCS controller in order to operate the motor speed in 2nd order manner. The resulting controller preserves the key DTC advantage of requiring minimal information about the induction motor that it drives, making them suitable combination for a robust, high performance "off-the-shelf" induction motor drive. The performance of the controller applied to DTC is compared in simulation and experiment with the widely used PI controller for speed transient, sudden load disturbance and non-linear torque variations. In all cases, the proposed controller exhibits significant improvements.