Vector Controlled Variable Frequency Induction Motor

Sensitive equipment and non-linear loads are now more common in both the industrial/commercial sectors and the domestic environment. Because of this a heightened awareness of power quality is developing among electricity users. Therefore, power quality is an issue that is becoming increasingly important to electricity consumers at all levels of usage. Continuous variation of single-phase loads on the power system network leads to voltage variation and unbalance, most importantly; the three-phase voltages tend to become asymmetrical. Application of asymmetrical voltages to induction motor driven systems severely affects its working performance. Simulation of an Induction Motor under various voltage sag conditions using Matlab/Simulink is presented in this paper. Variation of input current, speed and output torque for vector controlled variable frequency induction motor-drive is investigated. Simulation results show that the variation of speed and current in motor-drive system basically depends on the size of the dc link capacitor. It is shown that the most reduction of dc-link voltage happens during voltage sag. It is also observed that as the power quality become poor, the motor speed decreases, causing significant rise in power input to meet the rated load demand.