This paper proposes a sensorless (i.e. not requiring feedback information about rotor speed and position, and about wind velocity) control technique solving the tracking problem of the maximum delivered power characteristic for a wind energy conversion system equipped with a permanent magnet synchronous generator. A previously published sensorless control scheme ensuring the achievement of maximum power efficiency of the wind turbine is here extended to consider the drive-train dynamics. A novel observer of the electrical speed, based on the electrical variables only, is proposed, and asymptotic vanishing of the observation error is proved, as well as boundedness of the observer variables. Moreover, it is proved that the derived control algorithm can be easily modified also to ensure fault tolerance with respect to a class of system faults, sensor faults occurring in mechanical sensors being absent because of the sensorless approach here pursued. The proposed control solution has been validated on a 5 - MW three-blade wind turbine using the National Renewable Energy Laboratory (NREL) wind turbine simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code. (C) 2015 Elsevier Ltd. All rights reserved.