An extended Kalman filter approach to rotor time constant measurement in PWM induction motor drives

A rotor time constant estimation technique for the purpose of updating the control gains of an induction motor field-oriented controller is described. An extended Kalman filter is employed to estimate the inverse rotor time constant online only using measurements of the stator voltages and currents and rotor speed of an induction motor. The motor is driven by a pulsewidth modulated (PWM) inverter with or without current feedback loops. By utilizing the wideband harmonic contents inherent in conventional PWM voltage waveforms, no external random test signal is required for parameter estimation. Both computer simulation and experimental results show that the filter is capable of estimating the rotor time constant while the rotor speed is either constant or time varying