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

Abstract

This paper deals with an amplitude-adjusting method for signal injection in position sensorless control of interior permanent magnet synchronous motor (IPMSM) drives. Signal injection is necessary for position estimation at standstill and low speeds. Response signals to the injected signals have position information because of the 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 discussed in this paper is based on an extended electromotive force (EEMF) model. Although the EEMF model is mainly used in middleand high-speed regions of IPMSM drives, it can be applied to all speed regions by combining it with signal injection methods. We adopt a signal injection method to stabilize the estimation and reduce the effects of disturbances. Then, the amplitude of the signal currents is adjusted to maintain a sufficiently high amplitude of EEMF against disturbances. Signal setting becomes easier because the lower limit of EEMF can be adjusted against the degree of disturbances.