Adaptive signal injection method combined with EEMF based position sensorless control of IPMSM drives

Abstract

This paper deals with an amplitude adjusting method for a signal injection in position sensorless controls of IPMSM (Interior Permanent Magnet Synchronous Motor) drives. Signal injection is necessary for position estimation at standstill and low speeds. Response signals to the injected signals have position information caused by a saliency of the IPMSMs. The position information appears in inductances depending on the rotor positions, therefore, time derivative of motor currents has to be measured directly or indirectly. The position estimation method discussing in this paper is based on an EEMF (Extended Electromotive Force) model. Although the EEMF model is mainly used in middle and high speed regions of IPMSM drives, it can be applied all speed regions by combining with signal injection methods. We apply a signal injection method to stabilize the estimation and reduce the effects of disturbances. Then the amplitude of the signal currents is adjusted so as to keep an enough amplitude of EEMF against disturbances. Signal settings become easier because the lower limit of EEMF can be adjusted against a degree of disturbances.