In this paper a variable speed doubly fed induction generator (DFIG) based wind energy conversion system (WECS) is employed for simultaneous power generation and grid harmonic current filtering. WECS active and reactive powers are controlled using vector control strategy. An improved harmonic isolator in the time domain, based on a new high selective signal detector or filter (HSF) has been used. Since the polluting currents contain direct and reverse harmonics of (6k +/- 1) order, the HSF can be used to isolate one particular harmonic or the whole harmonic components. The compensation technique of the whole harmonic components of the grid current is chosen. The rotor side converter (RSC) control structure has been modified in order to include the filtering task. Simulation for a 3 MW WECS with DFIG at two different wind speeds (8 m/s and 12 m/s) has been performed. Results showed that in addition to power generation, grid current harmonics filtering action is achieved by the WECS and a decrease by 4% of the total harmonic distortion is obtained. (C) 2013 Elsevier Ltd. All rights reserved.