An object of the present invention is to provide a Wind Turbine Generation System that eliminates the necessity of switching to a circuit different from the one used during a normal power generation operation even when Power grid voltage sags. To accomplish the above object, the Wind Turbine Generation System according to the present invention includes a wind turbine having blades rotating upon receipt of wind, a rotor connected to the blades, and a permanent magnet generator connected to the rotor, the permanent magnet generator generating electric power by rotating a rotator having a permanent magnet in accordance with the rotation of the rotor; auxiliary machinery and a wind turbine controller that control the wind turbine; a power converter that adjusts the electric power generated by the permanent magnet and supplies the adjusted electric power to the auxiliary machinery and to the wind turbine controller; a DC converter that is connected to the permanent magnet generator to convert AC power to DC power; and a control device that is connected to the DC converter to control the power converter by using the DC power obtained from conversion.