Variable-Structure Direct Torque Control—A Class of Fast and Robust Controllers for Induction Machine Drives

A family of variable-structure controllers for induction machine drives is presented, in which the principles of direct torque control (DTC), variable-structure control (VSC), and space-vector pulsewidth modulation are combined to ensure high-performance operation, both in the steady state and under transient conditions. Three new VSC schemes are designed following the DTC voltage-control-based philosophy. These provide robust, fast, and accurate torque and flux control, without the penalty of high chattering. Comparative results demonstrate that proposed techniques preserve the DTC transient merits, while the steady-state behavior is significantly improved. Experimental results prove the strong robustness, accuracy, quickness, and low-ripple sensor-less operation of a drive that uses the new schemes.