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Patent Issued for Methods of rotating a hub of a wind turbine (USPTO 11098696)

  • Sep 15, 2021 1:15 am GMT
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Source: 
Engineering Business Daily

2021 SEP 14 (NewsRx) -- By a News Reporter-Staff News Editor at Engineering Business Daily -- According to news reporting originating from Alexandria, Virginia, by NewsRx journalists, a patent by the inventors Gil Molla, Isaac (Nantes, FR), Rates Palau, Sergi (Barcelona, ES), Schoenleber, Kevin (Barcelona, ES), Subramanian, Shanmuga-Priyan (Hamburg, DE), filed on August 29, 2019, was published online on August 24, 2021.

The assignee for this patent, patent number 11098696, is General Electric Renovables Espana S.L. (Barcelona, Spain).

Reporters obtained the following quote from the background information supplied by the inventors: “Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly (“directly driven”) or through the use of a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.

“When wind turbines are erected, the tower is generally constructed first. Then, the nacelle, which usually contains the generator and the gearbox (if present), is usually mounted on top of the tower. Then, the hub may be hoisted and mounted. Finally, the blades are hoisted one by one from a ground level towards the rotor hub and mounted therein. In an alternative method, one or more blades may be pre-assembled with the hub and be lifted together with the hub. The hub comprises a plurality of annular mounting flanges with openings. The blade comprises a plurality of fasteners, such as bolts, or pins or studs at its blade root. During installation, these fasteners are to be fitted into the openings in the mounting flanges.

“The installation of wind turbine blades has become an increasingly challenging task due to the general tendency to considerably increase the size and weight of modern wind turbines.

“The blades may be installed in a variety of ways, e.g. in a substantially vertical manner or substantially horizontally or at other inclined angles. However, such methods require rotation of the hub between the mounting of one blade and another for orientating the mounting flanges of the hub towards the direction of the blade during fastening of the connection. In order to correctly position the hub, torque is required for rotating the wind turbine rotor after mounting one blade in order to mount the next one. When not all blades have been mounted onto the hub, the hub is not balanced, so that the weight of one or more blades has to be carried upwards when rotating the hub. The corresponding torque may thus be very high.

“The torque may be delivered using the gearbox (when present) with an external power supply for rotating the rotor. Such a system may be used in combination with a locking pin for maintaining the rotor in a desired position for installation. This is not possible in case of directly driven wind turbines as no gearbox is provided between rotor and generator. Even though the generator may be suitable for operating as a motor, it will generally not be able to deliver the required torque to rotate the hub, especially when the hub is unbalanced, i.e. when at least one blade, but not all the blades have been mounted.

“Wind turbines comprise a converter or inverter to convert the power generated by the generator to make it compatible with the electrical grid. In theory, the converter of the wind turbine could be suitable to convert the power of the external power supply to run the generator as a motor. However, in order to provide a sufficient torque to make the hub rotate, the current supplied by the converter to the wind turbine generator must be very high. Furthermore, the voltage and the frequency must be very low.

“For these reasons, wind turbine converters are in practice not suitable to provide a sufficient torque for rotating the hub. In order to enhance the capabilities of the wind turbine controller for increasing the current delivered to the generator, the converter has to be completely redesigned. Such a redesign may imply oversizing the wind turbine converter which may produce an extra cost and an extra weight. Furthermore, as the working ranges of the electrical parameters of such oversized converters are wider, the efficiency of the oversized converter when the wind turbine is generating power may be penalized. The efficiency of the wind turbine may therefore be reduced.

“The present disclosure provides examples of systems and methods that at least partially resolve some of the aforementioned disadvantages.”

In addition to obtaining background information on this patent, NewsRx editors also obtained the inventors’ summary information for this patent: “In a first aspect, a method of rotating an unbalanced hub of a direct drive turbine is provided. The method comprises providing an auxiliary converter and a structure supporting the auxiliary converter, mounting the structure on the wind turbine, coupling the auxiliary converter to a generator of the wind turbine, supplying power from a power source to the auxiliary converter and supplying a current from the auxiliary converter to the wind turbine generator for generating a torque for rotating the unbalanced hub.

“In this aspect, the auxiliary converter may be particularly configured to convert the power provided by the power source to a suitable current supplied to the wind turbine generator that generates a torque for rotating the unbalanced hub. The “normal” wind turbine converter may therefore be designed only to control the power to be delivered to the electrical grid.

“In addition, as the structure supports the auxiliary converter, the auxiliary converter may be more easily lifted and mounted on the wind turbine. As a result, the time for transporting the auxiliary converter from one wind turbine to another wind turbine may be reduced. Expensive cranes and jack-up barges may thus be more efficiently used which may represent a significant cost saving in an offshore installation. Furthermore, as the auxiliary converter is placed near to the generator, controlling the rotation of the generator rotor may be simpler.

“In a further aspect, an apparatus for rotating an unbalanced direct drive wind turbine hub is provided. The system comprises an auxiliary converter configured to be coupled to a generator of the direct drive wind turbine, and configured to be coupled to a power source, and a structure supporting the auxiliary converter and configured to be temporarily supported by the direct drive wind turbine. The auxiliary converter is configured to supply a current to the wind turbine generator for generating a torque to rotate the direct drive wind turbine hub when the hub is unbalanced.

“According to this aspect, the apparatus for rotating the hub may be quickly mounted on the wind turbine. Installation time may thus be reduced. The auxiliary converter of the apparatus may thus provide a current required to make the rotor hub of a direct drive wind turbine hub rotate when the hub is unbalanced.”

The claims supplied by the inventors are:

“1. An apparatus for rotating an unbalanced hub of a direct drive wind turbine that includes a generator and a converter electrically coupled to the generator, the apparatus comprising: an auxiliary converter configured to couple to the generator of the direct drive wind turbine to a power source; a structure supporting the auxiliary converter and configured to be temporarily supported by the direct drive wind turbine; and wherein the auxiliary converter is configured to supply a current to the wind turbine generator for generating a torque to rotate the hub of the direct drive wind turbine when the hub is unbalanced.

“2. The apparatus according to claim 1, wherein the structure is configured to mount on top of a tower of the direct drive wind turbine.

“3. The apparatus according to claim 1, further comprising a first transformer coupled to the auxiliary converter.

“4. The apparatus according to claim 3, wherein the first transformer is configured to reduce a voltage supplied from the power source from a medium voltage to a low voltage.

“5. A system for rotating an unbalanced hub of a direct drive wind turbine that includes a generator and a converter electrically coupled to the generator, comprising: a power source; an auxiliary converter configured to couple to the generator of the direct drive wind turbine and to the power source; a structure supporting the auxiliary converter and configured to be temporarily supported by the direct drive wind turbine; and wherein the auxiliary converter is configured to supply a current to the wind turbine generator for generating a torque to rotate the hub of the direct drive wind turbine when the hub is unbalanced.

“6. The system according to claim 5, wherein the power source is a medium voltage electrical grid.

“7. The system according to claim 5, comprising a first transformer arranged between the power source and the auxiliary power converter, and a second transformer arranged between the first transformer and the power source.

“8. The system according to claim 7, wherein the power source comprises a fuel generator group and the second transformer is configured to raise the voltage supplied from the fuel generator group, and wherein the first transformer is configured to reduce the voltage supplied from the second transformer.

“9. The system according to claim 5, wherein the power source comprises a fuel generator group and the structure supports the fuel generator group.

“10. The system according to claim 5, comprising a controller configured to couple to a controller of the wind turbine for controlling the rotation of the hub of the wind turbine.

“11. A method of rotating an unbalanced hub of a direct drive wind turbine that includes a generator and a converter electrically coupled to the generator, the method comprising: providing an auxiliary converter and a structure supporting the auxiliary converter; mounting the structure on the wind turbine; coupling the auxiliary converter to the generator; supplying power from a power source to the auxiliary converter; and supplying a current from the auxiliary converter to the generator for generating a torque for rotating the unbalanced hub.

“12. The method according to claim 11, wherein mounting the structure on the wind turbine comprises mounting the structure on a top of a tower of the wind turbine.

“13. The method according to claim 11, comprising coupling a first transformer to the auxiliary converter.

“14. The method according to claim 13, wherein the power source is a medium voltage electrical grid and wherein the method comprises coupling the medium voltage electrical grid to the first transformer.

“15. The method according to claim 14, wherein the power source comprises a fuel generator group; and wherein the method further comprises: providing a second transformer; and coupling the second transformer to the fuel generator group and to the first transformer.

“16. The method according to claim 15, wherein the wind turbine is an offshore wind turbine and the second transformer and the fuel generator group are arranged in a vessel.

“17. The method according to claim 11, wherein the power source comprises a fuel generator group, comprising connecting the fuel generator group to the auxiliary converter.

“18. The method according to claim 11, wherein the method further comprises installing a wind turbine blade on the unbalanced hub by: rotating the hub to a first mounting position; lifting the wind turbine blade; and connecting the wind turbine blade to the hub.

“19. The method according to claim 18, comprising: rotating the hub to a second mounting position; lifting a second wind turbine blade; and connecting the second wind turbine blade to the hub.

“20. The method according to claim 18, wherein the wind turbine is an offshore wind turbine, the method comprising: mounting a first transformer on the top of the tower coupled to the auxiliary converter; providing a second transformer on a vessel; providing a power source on a vessel, wherein the power source includes a fuel generator group; coupling the second transformer to the first transformer; and supplying power from the power source to the auxiliary converter through the first and second transformers.”

For more information, see this patent: Gil Molla, Isaac. Methods of rotating a hub of a wind turbine. U.S. Patent Number 11098696, filed August 29, 2019, and published online on August 24, 2021. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=11098696.PN.&OS=PN/11098696RS=PN/11098696

 

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