SENSORLESS SPEED MEASUREMENT USING CURRENT HARMONIC SPECTRAL ESTIMATION IN INDUCTION MACHINE DRIVES

This paper proposes a sensorless speed measurement scheme that improve s the performance of transducerless induction machine drives, especial ly for low-frequency operation, Speed-related harmonics that arise fro m rotor slotting and eccentricity are analyzed using digital signal pr ocessing, These current harmonics exist at any nonzero speed and are i ndependent of time-varying parameters, such as stator winding resistan ce. A spectral estimation technique combines multiple current harmonic s to determine the rotor speed with more accuracy and less sensitivity to noise than analog filtering methods or the fast Fourier transform, An on-line initialization routine determines machine-specific paramet ers required for slot harmonic calculations, This speed detector, whic h has been verified at frequencies as low as 1 Hz, can provide robust, parameter-independent information for parameter tuning or as an input to a sensorless flux observer for a field-oriented drive, The perform ance of the algorithm is demonstrated over a wide range of inverter fr equencies and load conditions.