Supertwisting Sliding-Mode Direct Torque and Flux Control of Induction Machine Drives

A new supertwisting sliding-mode direct torque and flux controller (STSM-DTC) is proposed and investigated for induction motor drives. The supertwisting algorithm is a second-order sliding-mode control (SMC) that operates without high-frequency chattering and preserves the robustness properties of the classical SMC. The new STSM-DTC scheme uses torque and stator flux controllers implemented in the stator flux reference frame and it does not employ current controllers as in the conventional vector control. Both controllers contain a design parameter that allows adjusting their behavior between a linear proportional-integral (PI) like operation and a constant-gain classical sliding-mode behavior. Experimental tests show that STSM-DTC displays a very robust behavior, similar to a conventional SMC, and it works without notable steady-state chattering, as a PI controller. This article presents theoretical aspects for the new STSM-DTC scheme, stability analysis, design and implementation details, and relevant experimental results for a sensorless induction motor drive. The scheme is compared to a second-order sliding-mode controller and a linear PI controller. A robustness assessment against DTC with PI controllers, based on experimental tests, is also included.