This paper proposes a disturbance observer to estimate position and speed of the rotor of sensorless permanent magnet synchronous motor (PMSM), via detecting voltages and currents, which contain electromagnetic interference (EMI) produced by switching processes of inverters. In order to explore and relieve impacts of EMI on position error and speed error, theoretically introducing and analyzing main interference sources and common mode interference transmission paths in motor drive system, the inverter circuit with ideal and non-ideal metal-oxide-semiconductor field effect transistor (MOSFET) is built, and different gain coefficients of back-electromotive force (EMF) are carried out in Matlab/Simulink. The research of this paper provides a novel thoughts and ideas for enhancing theoretical framework of sensorless PMSM.

Electromagnetic interference (EMI), disturbance observer, metal-oxide-semiconductor field effect transistor (MOSFET), permanent magnet synchronous motor (PMSM).