This article presents a control strategy for wind farms equipped with doubly fed induction generators (DFIG) operating in a network with a complex load. As is known from vector control theory, DFIG are able to generate active and reactive powers in an independent way. Therefore, taking into account a unitary power factor, a wind farm control law based on the passivity theory is proposed looking for damping frequency oscillations after a network disturbance. Then, different practical considerations allow to simplify the obtained expression in order to achieve a feasible control law. The last one is added to the normal operating power reference of the wind farm established by a Supervisory Control. Finally, some simulations are shown to support the theoretical considerations.