An improved direct torque control of induction motor with modified sliding mode control approach

This work presents an improved direct torque control (DTC) of induction motor using modified sliding mode control technique for flux and torque control. The DTC gives fast dynamic response and robust control in ac drives. The conventional DTC method using hysteresis regulator has considerable flux and torque ripples at steady-state operation and also the switching frequency varies on a wide range. The proposed DTC technique based on sliding mode control (SMC) reduces flux, current, and torque ripples. It also narrows down the switching frequency variations in induction motor control. Two different sliding surfaces such as flux and torque sliding surfaces are used to control them. The error between reference and actual values are driven to respective sliding surfaces where the error is enforced to zero. A switching table based on space vectors of the voltage source inverter (VSI) is used to select the proper switching of the inverter. The performance of the proposed control technique is compared with that of conventional DTC. Simulation results for the proposed control method and conventional DTC control technique are presented.