Vector control of interior permanent magnet synchronous motor without a shaft sensor

Abstract

This paper describes the two control techniques to perform the sensorless vector control of interior permanent magnet synchronous motors (IPMSM) by injecting the high frequency voltage to the stator terminal. The first technique is the estimation algorithm of the rotor initial position including the identification of the rotor magnet N-S polarity at standstill. IPMSM possess the saliency which produces the ellipse of the stator current when the high frequency voltage is injected to the motor terminal. The major axis angle of the current ellipse gives rotor position information at standstill. The center of the current ellipse shifts because of the magnetic saturation effect from the origin, which makes it possible to identify the rotor magnet N-S polarity. The averaging method of the multi-cycles stator current is utilized to identify the rotor magnet N-S polarity. This averaging method increases the accuracy of the position estimation and solves the current ripple problem. The second control technique is a sensorless control algorithm that injects the high frequency current to the stator terminal in order to estimate the rotor position and speed. The rotor position and speed for sensorless vector control is achieved by appropriate signal processing to extract the position information from the stator current even in the low speed range. Experimental results are presented to verify the feasibility of the proposed control schemes.