Direct torque control of induction motor using sliding-mode and fuzzy-logic methods

Direct torque control (DTC) is known to generate fast and robust control for induction motor drives. Even though, in classical DTC, there exists a notable ripple in torque and flux during steady state, which can be reflected towards the speed response and generating undesirable acoustic noise. This paper introduces two approaches based on variable structure control (VSC) and fuzzy logic control (FLC) to mitigate steady state chattering problem while preserving the merits of DTC operation. The inverter is controlled directly on the basis of stator flux and the torque errors, by selecting most appropriate voltage vector from switching logic table. A comparative study is performed for the three control topologies including conventional DTC and simulation results are presented and discussed. It is concluded that SMC and intelligent control based technique provide better characteristics in steady state operation with regards to the conventional DTC.