Sensorless control of PMSM for low speed range

Abstract

Purpose – The purpose of this paper is to develop the Permanent Magnet Synchronous Motors drive which has possibility to work in sensorless mode at low speed based on back EMFs estimation. Design/methodology/approach – Estimation uses modified Luenberger observer and the preprocessing of the EMFs before calculating the speed, using derivative and the Kalman filter (KF) to obtain smooth waveform of the estimated speed. This modification is needed because of the nonlinear change of the estimated back EMFs amplitude as a function of speed, in low-speed range. Findings – How to use back EMF observer to estimate a speed in the low-speed range was found in the course of the work. Simple and effective algorithm uses KF and can work even with a relatively big deformation of the estimated back EMF. Practical implications – Such sensorless drive may be used in low-cost constant or variable speed drive in domestic use or industrial application. Such drive may work properly where there is no initial load torque and t...