Analysis of Unstable Regions in Vector-Controlled IPMSM Sensorless Control

Abstract

This paper reports our study of a phenomenon in which magnetic saturation causes a step-out in sensorless control of IPMSM motors using the magnetic flux observer. The Finite-Element-Method (FEM) can simulate the flux distribution and electromotive force at any armature current. The obtained voltage is supplied to the flux observer containing model errors. Under stable condition, the estimated phase error of this observer is calculated by easy vector operational expression. By the phase error characteristics, it was found that the unstable current appeared in the region, where the error fluctuation increases to the negative direction. We described this problem was caused by the voltage equivalent to interference component arising from the phase error fluctuation. Finally, we suggested a method of avoiding this unstable phenomenon and showed the improved result obtained through some experiments.