Standstill Identification of the Rotor Flux in Salient-Pole PMSMs

This paper proposes a new method to estimate the rotor flux of a Permanent-Magnet Synchronous Motor (PMSM) at standstill. This method works on motors that have enough magnetic saliency so that the reluctance torque can cancel the magnet-alignment torque. A nonlinear controller is designed to achieve standstill operation. The stability of this controller is studied using both the linearized model and nonlinear control theory. It is proven that the desired operating condition, where the rotor flux can be estimated, is locally asymptotically stable. Thanks to its bifurcation property, the proposed controller ensures zero speed for any type of PMSM, which is not the case for all existing methods. Furthermore, the estimation accuracy is made independent of the motor loading using a compensation procedure. The theoretical results are verified in simulation on an 11kW motor model.