An improved speed and position estimator for salient permanent-magnet synchronous motors

An improved phase-locked-loop-type speed and position estimator for permanent-magnet synchronous motor (PMSM) drives is considered. Particular attention is put on salient-rotor PMSMs with fast mechanical dynamics. A method is presented, whereby significantly improved tracking is achieved. While saliency makes nominal-speed stability more difficult to guarantee (an analysis of this is presented), a benefit is that signal-injection methods can be used at low speeds for accurate position estimation, which is also included in the modified estimator.