Digital current regulation of field oriented controlled induction motor based on predictive flux observer

The switching frequency of an inverter for a high-power induction motor drive cannot become higher than a few kilohertz, and such a switching frequency produces a large current ripple, which in turn produces torque ripple. To minimize the current ripple, a new method based on deadbeat current regulation under field oriented control is proposed, in which the pulse-width modulation (PWM) pattern is determined at every sampling instant. Measuring stator currents and motor speed and computing the rotor flux vector by a predictive state observer with variable pole selection, the stator currents are controlled to be exactly equal to the reference currents at every sampling instant. A theoretical analysis, computer simulations, and experimental results are described.>