Fluid reaction surfaces (i.e. – impellers) – With control means responsive to non-cyclic condition... – Plural distinct impellers having related control
Reexamination Certificate
2000-01-25
2002-03-26
Kwon, John (Department: 3747)
Fluid reaction surfaces (i.e., impellers)
With control means responsive to non-cyclic condition...
Plural distinct impellers having related control
C416S031000
Reexamination Certificate
active
06361275
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention concerns a wind power installation comprising a rotor with at least one rotor blade for converting the kinetic energy of the wind into mechanical energy, an adjusting device for individual adjustment of at least one rotor blade, a generator for converting the mechanical energy of the rotor into electrical energy, and an operative connection between the rotor and the generator for transmitting the mechanical energy of the rotor to the generator.
b) Description of the Related Art
Wind power installations of that kind are part of the state of the art. Thus for example the German reference book ‘Windkraftanlagen’ by Erich Hau, Springer-Verlag, 2nd edition, 1996, pages 52, 175, 222 to 242, 269 and 320 shows wind power installations of that kind. In those known wind power installations, the speed of rotor rotation and the power output can be regulated by means of a regulating system for the angle of incidence of the rotor blade. In addition the known system for regulating the rotor blade angle of incidence serves to protect the rotor from rotating at an excessive speed in the event of high wind speeds or in the event of a mains failure in which the generator torque abruptly disappears. Both cases involve protecting the wind power installation from damage due to a rotor rotating at an excessively high speed.
In that respect there are essentially two ways of producing a reduction in the speed of rotor rotation, by means of rotor blade adjustment; on the one hand the blade setting angle can be reduced in the direction of smaller aerodynamic angles of incidence in order thereby to reduce the power consumption of he rotor. On the other hand, it is possible to achieve the critical aerodynamic angle of incidence, the so-called stall condition, by adjusting the rotor blade setting angle to larger angles. The latter option affords the advantage of adjustment in a shorter distance, but it entails the disadvantage that flow break-down (stall) is related to high loadings for the rotor and the entire wind power installation. A common aspect of both adjustment options however, is that they only take account of a mean wind speed acting on the entire wind power installation, or a certain limit speed of rotor rotation, as the starting signal for setting the rotor blade angle.
A known wind power installation is installed in GB-A-2 067 247. In accordance with that publication, the wind power is measured in the plane of the rotor of wind power installations by means of pressure probes which are disposed at the surface of the rotor blades in the proximity of the profile nose. In that publication, the measurement values ascertained in that way are used inter alia to pivot the rotor plane of a wind power installation until the measurement values are the same for a rotor position of 90° and 270°.
A further known wind power installation is known from U.S. Pat. No. 4,297,076. The wind turbine disclosed here is a stall-controlled machine. The main rotor blades of that known installation are fixedly connected to the hub and are not rotatable on their longitudinal axis. The main loads in the main shaft of the installation are produced by the non-rotatable components of the rotor blades.
The above mentioned options in the state of the art do not take account of the fact that, particularly when a large rotor diameter is involved, there can be a non-uniform distribution of the wind conditions over the area of the rotor. That in turn results in different loadings on individual rotor blades as well as asymmetrical loadings for the drive train of the wind power installation, that is to say the hub, the drive shaft and the respective bearings. Different asymmetrical loadings of that kind, however do not only occur just as from a given speed of rotor rotation or a given wind speed, but also take place continuously during normal operation of the wind power installation. The blade angle regulation known hitherto from the state of the art cannot therefore react to fluctuations in wind speed and fluctuations in load, which are related thereto, in the region of the rotor, as the known installations provide for uniform, synchronous adjustment of the rotor blades.
In more modern installations (see in particular page 238 of the above-mentioned reference book), on the one hand, individual electrical adjustment of each individual rotor blade has admittedly been proposed; however that proposal is also based on the assumption of a mean wind speed acting on the wind power installation. With that and the further assumption that the wind speed increases with height, the proposal is then for a fixed, rotationally cyclical correction of the rotor blade incidence angle in order to be able to at least partially regulate out the changing loads upon the increase in wind speed with height. That rotor blade setting procedure also suffers from the disadvantage that the angle of incidence of the rotor blades is fixedly predetermined and therefore cannot react to local, temporary changes in the wind speed over a part of the rotor. With this proposal also therefore, there is an asymmetrical loading on the components of the wind power installation, which thus reduces the service life thereof, in the case of local peaks in the wind speed as viewed over the area of the rotor.
OBJECT AND SUMMARY OF THE INVENTION
Primary object of the invention is therefore that of avoiding the above-mentioned problems and providing a wind power installation which reduces the loadings which can occur by virtue of local, temporary peaks in the wind speed in portions of the rotor area.
In accordance with the invention, that object is attained in that, in a wind power installation of the kind set forth in the opening part of this specification, there are provided measuring means for ascertaining the instantaneous loading of a part of the wind power installation, control means for ascertaining a position of at least one rotor blade, wanted for the instantaneous loading, and for suitably adjusting the rotor blade by means of the adjusting device, and connecting means connecting the adjusting device and the measuring means to the control means.
The wind power installation according to the invention makes it possible, by means of the adjusting device for individual adjustment of at least one rotor blade, for the wind power installation to be matched by means of the control means to instantaneous loadings which occur locally only at a part of the wind power installation, such loadings being ascertained by the measuring means. This advantageously provides that local peaks in the loading on the rotor blades, the hub, the shaft drive and the bearings used are avoided. That in turn has the consequence that the service life of the wind power installation is increased or is not unintentionally reduced as asymmetrical loadings of parts of the wind power installation, which are such as to reduce the service life thereof, are substantially avoided.
In addition, the wind power installation according to the invention permits optimum use to be made of the instantaneous distribution of the wind speeds on the rotor area and thus makes it possible to contribute to an increased power output from the wind power installation as all rotor blades are always operated with the desired and thus optimum blade angle and therefore the level of efficiency per rotor blade rises in comparison within the efficiency of the wind power installations in the state of the art.
It is particularly preferred for the position of the rotor blade or blades to be uninterruptedly adapted to the instantaneous loading of the wind power installation. In that way it is possible to ensure that the wind power installation is continually operated in the optimum working range and at the same time is protected from loading peaks, triggered due to wind speed peaks which occur locally in the region of the rotor.
In a preferred embodiment of the invention the measuring means for ascertaining the local loading on a rotor blade ascertain a wind speed which obtains
Kwon John
Reed Smith LLP
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