A new method for rotor time constant tuning in indirect field oriented control

A novel adaptive controller for correction of the rotor time constant necessary for the calculation of the slip frequency in indirect field-oriented control of induction machines has been investigated and implemented. The implementation of the controller is based on the machine airgap field flux, which is measured by detecting the third harmonic component of the stator phase voltages. the adaptive controller depends only on a single, easily measurable machine parameter estimate, namely the magnetizing inductance. A correction strategy to compensate for changes of the magnetizing inductance when changes in the airgap flux level occur is also proposed. This strategy is based on a function that relates the value of this inductance to the amplitude of the third harmonic stator voltage component. This controller does not require any sensors in the airgap of the machine, nor does it require complex computations of machine parameters. Only access to the stator neutral connection is necessary to measure the airgap flux. Verification of the validity and feasibility of the technique is obtained from simulation and preliminary experimental results.<<ETX>>

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