Pitch varying device, pitch varying method and pitch varying control device for wind turbine blade and wind turbine

A pitch varying device for a blade of a wind turbine, configured to control a pitch angle of the blade rotatably mounted on a hub, and the blade being mounted on the hub through a pitch bearing, and the pitch varying device comprises:

• a disc-type driving structure fixedly mounted on the blade and being perpendicular to an axis of the pitch bearing, wherein a track surrounding the axis of the pitch bearing is provided on the disc-type driving structure;
• a first linear telescopic driving mechanism having one end hinged to the hub and another end hinged to a first clamping member;
• and
• a second linear telescopic driving mechanism having one end hinged to the hub and another end hinged to a second clamping member;
• wherein
• the first linear telescopic driving mechanism is configured to drive the disc-type driving structure in a case that an included angle between a target pitch angle and a present pitch angle is smaller than or equal to a preset threshold;
• in this case, the first clamping member is configured to clamp the track, and the second clamping member is configured to be disengaged from the track;
• and
• the second linear telescopic driving mechanism is configured to drive the disc-type driving structure in a case that the included angle is greater than the preset threshold;
• in this case, the second clamping member is configured to clamp the track, and the first clamping member is configured to be disengaged from the track.