This paper presents a power control study of a Wind Energy Conversion System (WECS) based on a DoublyFed Induction Generator (DFIG) connected to the electric power grid. Proportional-Integral (PI) and Sliding Mode (SM) controls are used to compare the system's performances in terms of reference tracking and robustness to disturbance rejection and with respect to the machine parameters variation. The DFIG control method is based on vector direct control loop with stator flux orientation and the active and reactive powers are controlled PI and sliding mode Simulation studies were performed using Matlab/Simulink/ SimPowerSystems software.