The rotor position and speed of synchronous motors are required in vector control applications to achieve efficient performance of such motors. Many methods of sensorless speed control of a permanent-magnet synchronous motor (PMSM) have been developed to overcome the limitations of sensors. This work introduces a new sensorless speed controller of PMSM using fractional-order extended state observer (FoESO). The fractionalorder dynamics of the extended state observer provide better performance and higher estimation accuracy than the integer-order one. The performance of the proposed model is validated via numerical simulations by using two distinct realizations for the FoESO; namely, Oustaloup’s, and El-Khazalis’ approximations. Besides its lowest order, El-Khazali’s first-order approximation provides a competitive candidate to that of other approximations of higher orders. All results are demonstrated via numerical simulation.
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