Sensorless control of interior permanent magnet synchronous motor by estimation of an extended electromotive force

Recently, many methods have been proposed for surface permanent magnet synchronous motor (SPMSM) sensorless control based on an estimation of electromotive force (EMF), in which the motor's position information is included. However, these methods cannot be applied to internal permanent magnet synchronous motors (IPMSMs) directly, because the position information is included in not only the EMF but also the inductance of stator. In this paper, a new mathematical model for IPMSMs is proposed and an extended EMF is defined, which includes both position information from the EMF and the stator inductance. As a result sensorless controls for SPMSMs can easily be applied to IPMSMs. As an example, a disturbance observer is studied and the experimental results show that the proposed method is very effective.