A wind turbine power plant having high capacity of generating electric power by installing a plurality of wind turbine electric power generator units each of which utilizes the rotation force generated by applying wind force to a plurality of blades to drive a generator via the rotor shaft, is constructed at high elevation such as the top of a hill or mountain or at a place such as above the sea where high wind velocity can be received. The generator set is generally controlled by adjusting the pitch angle of blades connected to the wind turbine rotor for keeping required generation of power corresponding with the energy of wind and the power to be consumed (required generation power) at the time of operation.
An upwind type wind turbine having a rotor with blades attached in the front part of the nacelle supported on a support prevails for use in the wind turbine generator unit.
An upstream type wind turbine like this is disclosed in Japanese Patent Application Publication No. 5-60053, which has a nacelle (wind turbine rotor supporting body) supporting a turbine rotor by means of a main shaft (turbine rotor shaft). The nacelle contains therein an energy converting unit such as an electric generator and a transmission mechanism for transmitting the rotation of the main shaft to the energy converting unit, and is supported for rotation in a horizontal plane on a support standing erect on the earth or on a ship.
In the wind turbine generator unit, a yaw control (azimuth control) means is used for keeping the revolution surface of the blades always toward the direction of wind to allow the wind force to act efficiently on the blades by rotating the nacelle supporting the wind turbine for rotation in accordance with the direction of wind. The wind turbine is equipped with a yaw control means which includes a yaw brake for braking the nacelle which is allowed to rotate in accordance with the direction of wind when wind is strong due to a typhoon, etc., as shown, for example, in patent document 1 (Japanese patent Application Publication No. 8-82277)
As shown in FIG. 13 and FIG. 14 which shows the detail of Z part of FIG. 13 in a perspective view, the yaw brake 3 is used for locking the wind turbine proper 100A consisting of blades 101, a rotor 105, a rotor shaft, and a nacelle 102. A rotation seat bearing 312 is located between the top face of the support 106 and the wind turbine proper 100A mounted above the support 106. A brake disk 304 is attached between the support 106 and the bearing 312. A hydraulically actuated disk brake unit 310 having a hydraulic cylinder 301a, 301b and a brake caliper 308 sandwiches the brake disk 304. The rotation of the wind turbine proper 100A relative to the support 106 is braked by pressing the brake disk from its upper and lower side by the hydraulically actuated disk brake unit 310.
In the upwind type wind turbine generator equipped with the yaw control means and the yaw brake, the nacelle is controlled by the yaw control means in normal operation to rotate so that the revolution surface of the blades directs always to wind. When a power outage occurs due to a sudden gust of wind, or strong wind caused by a typhoon, etc., the yaw control becomes impossible, so the nacelle is locked by actuating the yaw brake.
As mentioned above, with the conventional art as disclosed in the patent document 1, generally the rotation of the nacelle is locked by actuating the yaw brake to keep the nacelle in a standby state when a power outage occurs due to a sudden gust of wind, or strong wind due to a typhoon, etc. Therefore, when a strong wind blows on the blades in a slanting direction when the rotation of the nacelle is locked into a standby state, breakage occurs in the blades many times due to an excessively biased-load acting on the blades in the slanting direction.