Patent ID: 6242885
Filing Date: 2001-06-05
Classification: H02P

Abstract:
A method of controlling an induction motor by bringing .gamma.-.delta. coordinate axes which are reference coordinate axes of a control system configuration into agreement with d-q coordinate axes where the d-axis represents the direction of the vector of secondary magnetic fluxes of the induction motor and the q-axis represents an axis perpendicular to the d-axis, said method comprising the steps of detecting at least two of three-phase stator currents of the induction motor, converting the detected stator currents into a .gamma.-.delta. coordinate system to derive a .gamma.-axis current Is.gamma. and a .delta.-axis current Is.delta., constructing a state estimator using differences Is.gamma.-Is.gamma., Is.delta.-Is.delta. between estimated values Is.gamma., Is.delta. of the .gamma.-axis current and the .delta.-axis current in a preceding control loop and actual values thereof as corrective quantities, using stator voltage command values Us.gamma.*, Us.delta.* in the .gamma.-.delta. coordinate system as inputs, and using an induced electromotive force generated by rotation of a rotor as a disturbance, and estimating estimated values Is.gamma., Is.delta. of stator currents and estimated values .epsilon..sub..gamma., .epsilon..sub..delta. of the induced electromotive force in the .gamma.-.delta. coordinate system.