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

A new technique based on deadbeat control theory is proposed to control induction motor stator currents under field-oriented control. Stator currents and motor speed were measured. Rotor fluxes are predicted using a state observer with variable poles selection. Then, the pulse-width-modulated (PWM) pattern of the inverter is controlled such that the stator currents are exactly equal to the reference currents at every sampling instant. From the theoretical analysis, digital simulations, and experimental results, the following conclusions were made. The deadbeat controller permitted low current ripple with lower switching frequency, which, in turn, resulted in low torque ripple. The predictive state observer made possible the estimation of rotor flux with very low sensitivity to parameter variation and then contributed to performance improvement of conventional vector control