Sensorless vector control using a model reference feedforward system

A sensorless control algorithm using model reference feedforward control is reported, based on a rotor flux oriented steady state model of the induction motor. Magnetising and torque currents are obtained from measurement of stator current, and deviations from model values and their derivatives are used to adjust the output voltage and generated frequency. Slip frequency is calculated from torque current, and speed error is compensated by a filter, chosen to give stable operation and fast transient response. Motor parameters are obtained by a self-commissioning technique. Good dynamic performance and low-speed performance have been achieved down to speeds of 2 Hz or lower, allowing 150% starting torque from rest and 150% torque transients