The subject matter described herein relates generally to start-up methods and systems for start-up of a wind turbine.
Generally, a wind turbine includes a turbine that has a rotor that includes a rotatable hub assembly having multiple blades. The blades, which are also referred to as rotor blades, transform wind energy into a mechanical rotational torque that drives one or more generators via the rotor. The generators are sometimes, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid via at least one electrical connection. Gearless direct drive wind turbines also exist. The rotor, generator, gearbox and other components are typically mounted within a housing, or nacelle, that is positioned on top of a base that may be a truss or tubular tower.
Each of the rotor blades is typically rotatably mounted on the hub using a respective pitch-drive system having a gearing supporting the rotor blade. Accordingly, the rotor blades can be adjusted relative to the wind direction. During partial load operation of the wind turbine, the rotor blades are typically in a fully powered position which may correspond to respective fully powered pitch angle values of 0° of the pitch-drive systems while pitch angle values of 90° may correspond to respective feathered positions. If the wind speed exceeds its rated value, the pitch angles of the rotor blades are typically varied so that the wind turbine can operate with fully rated power. On average, the pitch-drive systems typically operates the rotor blades in or close to the fully powered positions for more than about 50%, more than about 60% or even more than about 70% of the operating time. Accordingly, the fully powered positions of the rotor blades typically correspond to main operating positions in which and/or close to which the risk of gear wear of corresponding load portions of the pitch-drive systems is increased.
The load portions may be lubricated during a non-operating phase of the wind turbine, for example during a regular maintenance or in the absence of high enough wind. However, production phase may be long posing a risk of gear damage due to a non-surviving lubricating film. On the other hand, short maintenance intervals ensuring sufficient lubrication result in production losses and, thus, increase costs. This is of particular importance for coastal or offshore wind turbines.
It would therefore be desirable to provide systems and methods for improved lubrication of pitch drive systems.