A COMPARISON OF SPECTRUM ESTIMATION TECHNIQUES FOR SENSORLESS SPEED DETECTION IN INDUCTION MACHINES

This paper compares digital spectrum estimation techniques which can b e used to extract speed information from rotor slot and eccentricity h armonics contained in the stator current. In previous work, speed-rela ted current harmonics have been shown to improve the performance of ex isting back-EMF-based sensorless schemes, since these harmonics are pa rameter independent and exist at virtually any nonzero speed. Digital filtering, however, requires a minimum data sampling time in order to achieve the desired resolution. The contribution of this paper is to d etermine the optimal method for accurately extracting the speed-relate d harmonics in the least amount of time. Several digital signal proces sing algorithms are investigated, including the fast Fourier transform and other traditional methods, as well as parametric techniques which can provide improved spectrum estimation for short data records. Each approach is evaluated on the criteria of accuracy, robustness, and co mputation time given a short data record.