Improved Direct Torque Control Strategy Suitable for Wide Range Speed Control Of Induction Motor Drive

Abstract

Materials and Methods: This research work implements performance index based hybrid flux estimation, variable width torque and flux hysteresis band controllers and improved switching vector tables. The performance index is calculated from operating speed, THD of stator current and switching frequency of the Power Electronic (PE) device used in Voltage Source Inverter (VSI). This new strategy is simulated using Matlab/Simulink and experimentally confirmed in real time on Digital Motor Control board using F28035 DSP controller board with 0.25 h.p. induction motor. newlineResults and Discussion: Simulation of VSI fed IM drive with conventional DTC strategy shows high torque ripple, high THD of stator current, variable switching frequency, and poor low-speed performance. After implementing performance index K based improved DTC strategy, simulation results indicate that there is a significant reduction in torque ripple and %THD for the low-speed mode. The same is experimentally confirmed by implementing it on Digital Motor Control kit with F28035 DSP of Texas Instrument. newlineConclusion: In this research work improved control strategy for wide range speed control is implemented. Smooth and automatic transition from high-speed mode to low-speed mode or vice versa is possible based on performance index K. Thus, for wide range speed applications, this improved strategy is useful giving lesser torque ripple, lesser THD of stator current and better switching frequency for the whole speed range.