Prime-mover dynamo plants – Fluid-current motors – Wind
Patent
1998-06-10
1999-11-23
Enad, Elvin
Prime-mover dynamo plants
Fluid-current motors
Wind
290 52, 290 44, 290 53, 290 54, F03D 900, H02P 904
Patent
active
059905689
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL AREA
The present invention relates to a yawing system for wind turbines intended for adjusting the wind turbine in the required wind direction about the yawing axis of the turbine and for preventing periodic vibrations in the nacelle around the yawing axis being transmitted as pulsating moments to the tower structure.
BACKGROUND TO THE INVENTION
Hydraulic motors are conventionally used in wind power stations to yaw the turbine nacelle to the required angle against the wind. Once the required position is reached the nacelle is locked with powerful brakes. The turbine is kept in this position until the wind direction has changed by a certain minimum angle, whereupon the brakes are released and the turbine is rotated to a new position where it is again locked etc. The system has a number of disadvantages and limitations; the turbines do not provide optimum efficiency and the stresses on the brakes are very large which often results in slipping and damage. Another problem of wind turbines is that the vibrations occurring in the nacelle as a result of the forces acting on the rotor are not equally large over the entire sweep area of the rotor. For example, the wind speed is often higher at greater heights than nearer the ground.
These problems are well known and many systems have been developed to prevent these fluctuations being transmitted as pulsating moments to the power station structure, more particularly the tower. For example, EP-A1-0 110 807 describes a system in which a controllable flow valve is arranged in a by-pass line to the hydraulic motor which is intended to yaw the nacelle towards the wind, while accumulators are provided to reduce the pressure vibrations in the hydraulic system caused by the nacelle fluctuations about the yawing axis. The inventors of the now proposed system have tested systems of this type and have found that in order to achieve an intended effect by the by-pass valve, its throttle must be of such a large diameter that it would need a very large flow from the oil pump to get the turbine to yaw at all. This solution is therefore considered to be impossible to use in practice.
There also remains the problem that the energy which is produced by the nacelle fluctuations is not in itself transmitted to the tower but is retained in the hydraulic system through recharging the accumulators. In addition the energy stored in the accumulators acts in the wrong direction, so to speak, as when the nacelle has swung round to an end position and the accumulators have been fully recharged, the pressure is exerted in the same direction as the returning vibrations and so does not damp the vibration but increases it instead. The unwanted energy from the fluctuations is therefore not removed to any great extent.
DESCRIPTION OF THE INVENTION
The aim of the invention is to reduce the periodic vibrations which arise during operation, to prevent the energy produced as a result of the vibrations being transmitted to the turbine structure, as well as to yaw the turbine continuously during operation against the direction of the wind. This aim is achieved with a wind turbine yawing system for adjusting the wind turbine in the required direction against the wind by rotation about the yawing axle of the turbine and preventing periodic vibrations in the nacelle around the yawing axle being transmitted as pulsating moments to the tower structure, which is characterised in that the nacelle is arranged so as to be able to rotate about the yawing axle with the aid of at least one hydraulic motor, that a controllable throttle valve is arranged in a parallel line (by-pass line) of the hydraulic motor, and that the opening diameter of said parallel valve is arranged so as to be adjustable in accordance with the nacelle position in relation to the wind direction.
DESCRIPTION OF THE FIGURES
In the following description of a preferred embodiment, reference is made to the following figures in which
FIG. 1 is a side view of the nacelle of a wind turbine in a partially cut away view,
FIG. 2 is a c
REFERENCES:
patent: 4515525 (1985-05-01), Doman
patent: 4522564 (1985-06-01), Carter, Jr. et al.
patent: 4792281 (1988-12-01), Coleman
patent: 5178518 (1993-01-01), Carter, Sr.
patent: 5353593 (1994-10-01), Phillips
patent: 5354175 (1994-10-01), Coleman et al.
patent: 5584655 (1996-12-01), Deering
Hildingsson Sten
Westin Torbjorn
Enad Elvin
Kvaerner ASA
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