Observers for induction motor rotor current estimation

The Kalman filter (KF) in its basic form is a state estimator and can be applied to the problem of estimating induction motor rotor currents in a vector control scheme. It is shown how this filter combines information from the plant model with output measurements to produce an optimal estimate of the unmeasured states. Because the KF can deal with a time-varying linear plant model, the rotor current can be estimated while the rotor speed is varying. The application of the extended Kalman filter algorithm induction motor drive is also described. Significant savings in computing requirements are obtained with a reduced-order model of the motor, in which measured, rather than computed, values of stator currents are used.<>