(19)
(11)EP 2 919 353 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
14.08.2019 Bulletin 2019/33

(21)Application number: 14169252.5

(22)Date of filing:  21.05.2014
(51)International Patent Classification (IPC): 
H02J 3/34(2006.01)
H02J 3/38(2006.01)

(54)

METHOD AND APPARATUS FOR OBTAINING ELECTRICITY FROM OFFSHORE WIND TURBINES

VERFAHREN UND VORRICHTUNG ZUR ERZEUGUNG VON STROM MIT OFFSHORE-WINDTURBINEN

PROCÉDÉ ET APPAREIL PERMETTANT D'OBTENIR DE L'ÉLECTRICITÉ À PARTIR D'ÉOLIENNES EN MER


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 14.03.2014 US 201461953111 P
15.04.2014 US 201414253590

(43)Date of publication of application:
16.09.2015 Bulletin 2015/38

(73)Proprietor: ABB Schweiz AG
5400 Baden (CH)

(72)Inventors:
  • Pan, Jiuping
    Raleigh, NC 27606 (US)
  • Das, Debrup
    Raleigh, NC 27606 (US)
  • Feng, Xiaoming
    Cary, NC 27519 (US)

(74)Representative: Lundqvist, Alida Maria Therése 
ABB AB Intellectual Property Forskargränd 7
721 78 Västerås
721 78 Västerås (SE)


(56)References cited: : 
EP-A1- 1 276 224
WO-A1-2012/048743
US-A1- 2003 227 172
EP-A2- 2 161 443
CN-A- 103 311 951
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    TECHNICAL FIELD



    [0001] The present invention generally relates to offshore wind turbines and particularly relates to obtaining electricity from offshore wind turbines.

    BACKGROUND



    [0002] Typical large-scale offshore wind farm architectures include a plurality of wind turbines, along with generators and collection networks, for collecting the generated electricity and transmitting it to shore, e.g., via high-voltage DC, HVDC, or high-voltage AC, HVAC, transmission systems. The choice of HVAC or HVDC transmission depends mainly on the distance from the offshore wind farm to the onshore grid connection point.

    [0003] The use of low-frequency AC, LFAC, transmission at high voltages to the onshore grid connection point has also been considered. While LFAC transmission from the offshore wind farm requires additional frequency conversion equipment at the onshore grid connection point, its usage can extend the economic distance of HVAC connections between the offshore wind farm and the onshore grid connection point.

    [0004] In a known approach to low-frequency collection and transmission of electricity in offshore wind farms, low-speed generators produce AC outputs with a nominal frequency of 16.7Hz or 20Hz. The generated electricity is coupled into the LFAC transmission system using one or more boost transformers. However, it is recognized herein that this approach suffers from a number of disadvantages, including necessitating the use of undesirably large equipment. Known systems for obtaining electricity from wind turbines are disclosed in documents EP 2 161 443 A2 and CN 103 311 951 A.

    SUMMARY



    [0005] According to one aspect of the teachings herein, various feeder connection arrangements and architectures are disclosed, for collecting electricity from wind turbines in an offshore collection grid that operates at a fixed low frequency, e.g., at one third of the targeted utility grid frequency. Embodiments herein detail various feeder arrangements, such as the use of parallel feeder connections and cluster-based feeder arrangements where a centralized substation includes a common step-up transformer for outputting electricity at a stepped-up voltage, for low-frequency transmission to onshore equipment. Further aspects relate to advantageous generation arrangements, e.g., tower-based arrangements, for converting wind power into electrical power using, for example, medium-speed or high-speed gearboxes driving generators having a rated electrical frequency for full-power output in a range from about 50 Hz to about 150 Hz, with subsequent conversion to the fixed low frequency.

    [0006] In an example embodiment, a system is configured for obtaining electricity in an offshore wind turbine farm. The system includes at least a first arrangement that comprises a gearbox, a generator, and an AC-to-AC converter. The gearbox is configured to mechanically convert a first variable rotational speed of a wind turbine into a corresponding higher second variable rotational speed. The generator has a rated electrical frequency for full-power output in a range from about 50 Hz to about 150 Hz, and is configured to be driven at the variable second rotational speed by an output of the gearbox. The generator thereby generates electricity at a correspondingly variable first frequency and the AC-to-AC converter is configured to convert the electricity from the generator into electricity output from the AC-to-AC converter at a fixed low frequency for off-shore collection at the fixed low frequency. The fixed low frequency is lower than the utility grid frequency, e.g., one-third of the frequency of the targeted onshore utility grid.

    [0007] In some embodiments, the first arrangement further comprises a step-up transformer connected between the generator and the AC-to-AC converter. The step-up transformer has a rated frequency corresponding to the rated electrical frequency of the generator and is configured to step up a voltage of the electricity output from the generator, and thereby output electricity at a stepped-up voltage. Embodiments not comprising a step-up transformer do not form part of the present invention. Correspondingly, the AC-to-AC converter is configured to convert the electricity output at the stepped-up voltage from step-up transformer. Thus, it will be understood that in some embodiments the AC-to-AC converter operates on the variable-frequency electricity as directly output from the generator, and in other embodiments it operates on the electricity output from a transformer that is connected between the AC-to-AC converter and the generator.

    [0008] In another embodiment, a method of obtaining electricity from an offshore wind turbine farm includes mechanically converting a variable first rotational speed of a wind turbine into a corresponding higher variable second rotational speed, and generating electricity at a variable first frequency using a generator having a rated electrical frequency for full-power output in a range from about 50 Hz to about 150 Hz. The generator is driven at the variable second rotational speed and the method further includes converting the variable-frequency electricity output from the generator into a fixed low frequency for offshore collection at the fixed low frequency. Conversion to the fixed low frequency may operate directly on the output from the generator, or may operate on the output of a step-up transformer that is driven by the output from the generator. The fixed low frequency is in a range from about 16 Hz to about 20 Hz, for example.

    [0009] In a further example embodiment, a system is configured for obtaining electricity in an offshore wind turbine farm that includes a plurality of wind turbines. The system includes an arrangement corresponding to each wind turbine. Each arrangement includes a gearbox, a generator, and an AC-to-AC converter. The gearbox is configured to mechanically convert a variable first low rotational speed of the corresponding wind turbine to a higher variable second rotational speed. The generator has a rated electrical frequency for full-power output in a range from about 50 Hz to about 150 Hz, and outputs electricity at a variable first frequency, based on being driven by the gearbox at the variable second rotational speed. Correspondingly, the AC-to-AC converter is configured to convert the electricity from the generator, either taken directly from the generator or through a step-up transformer, into output electricity at a fixed low frequency, which is lower than the grid frequency of the targeted onshore electrical grid.

    [0010] Further, the example system includes an offshore low-frequency collection grid that comprises one or more feeders. Each feeder is associated with one or more of the arrangements and is configured to collect the electricity output from the associated arrangements at the fixed low frequency.

    [0011] Of course, the present invention is not limited to the above features and advantages. Those of ordinary skill in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0012] 

    Fig. 1 is a block diagram of one embodiment of a system and arrangement for obtaining electricity from an offshore wind turbine farm.

    Fig. 2 is a logic flow diagram of one embodiment of a method of obtaining electricity from an offshore wind turbine.

    Figs. 3A-3C are block diagrams of alternate embodiments of feeder networks within an offshore low-frequency collection grid, for collecting electricity from a plurality of wind turbines.

    Fig. 4 is a block diagram of another embodiment of arrangements for obtaining electricity from respective offshore wind turbines and a corresponding embodiment for an offshore low-frequency collection grid.


    DETAILED DESCRIPTION



    [0013] Fig. 1 illustrates a plurality of like arrangements 10-1, 10-2, ..., and 10-N, each of which is configured to obtain electricity in an offshore wind farm. More particularly, each arrangement is associated with a given wind turbine 8, and includes a gearbox 12, a generator 14, an optional step-up transformer 16, and an AC-to-AC converter 18. Unless suffixes are needed for clarity, the reference numeral "10" will be used to refer to any given arrangement 10 in the singular sense, and to any given arrangements 10 in the plural sense.

    [0014] The plurality of arrangements 10 connect to a low-frequency offshore collection grid 20, which includes one or more feeders 22, shown here as feeders 22-1, 22-2, ..., 22-M. The value of M is an integer number generally less than the value of N-i.e., the number of arrangements 10-inasmuch as each feeder 22 usually will be associated with more than one arrangement 10. Broadly, however, each feeder 22 is coupled to one or more arrangements 10 among the plurality of arrangements 10 and collects the electricity from its associated arrangements 10 into the low-frequency offshore collection grid 20.

    [0015] The diagram further depicts a number of protective devices 24 disposed at wind turbines 8 for coupling the corresponding arrangements 10 with the low-frequency offshore collection grid 20. Further protective devices 24 are used within a central substation 30 that is included in the low-frequency offshore collection grid 20 for coupling feeders 22 and low-frequency collection transformer 28 with the bus 26. In more detail, one sees that the output from the collection transformer 28, also referred to as the "step-up transformer 28," couples into a low-frequency high-voltage transmission system 32, which includes one or more transmission lines 34 that carry the electricity output from the low-frequency offshore collection grid 20 to onshore equipment 36. In turn, the onshore equipment 36 converts the electricity from the offshore wind into the correct frequency for the coupling into the onshore electric grid 38, with or without further voltage adjustments.

    [0016] The onshore electric grid 38 comprises, for example, an onshore transmission system operating at 50 Hz or 60 Hz. In some embodiments, the low-frequency offshore collection grid 20 is configured to operate at one-third of the frequency of the onshore electric grid 38, e.g., at about 16 Hz for a 50 Hz utility grid frequency and at about 20 Hz for a 60 Hz utility grid frequency.

    [0017] With these example details in mind, then, the diagram of Fig. 1 can be understood as disclosing a system 40 that is configured for obtaining electricity in an offshore wind turbine farm. In a minimal configuration, the system 40 includes at least a first one of the previously described arrangements 10. In some embodiments, that first arrangement 10 includes gearbox 12 that is configured to mechanically convert a variable first rotational speed of a wind turbine 8 into a higher variable second rotational speed. As a non-limiting example, the gearbox provides an input-to-output turns ratio of from about 10-to-1 to 100-to-1.

    [0018] The first arrangement 10 further includes a generator 14 having a rated electrical frequency for full-power output in a range from about 50 Hz to about 150 Hz. For example, the generator 14 has a rated electrical frequency of 75 Hz, for full-power output. It is desired herein to generate electricity at frequencies substantially higher than the rotational speed of the wind turbine 8, and it will be appreciated that these higher frequencies can be obtained by mechanical gearing in the gearbox 12 and/or by configuring the number of electrical poles in the generator 14. However, the actual frequency of the electricity output from the generator 14 at any given instant will be proportional to the rotational speed of the wind turbine 8 and will vary with the rotational speed of the wind turbine 8.

    [0019] The electricity output from the generator 14 is referred to herein as having a variable first frequency, denoted as f1 in the diagram. In a non-limiting example of actual operation, the first variable frequency may range from about 20 Hz to about 150 Hz, in dependence on actual wind speed. In more detail, the variable first frequency of the generated electricity may deviate or vary from the rated electrical frequency of the generator with variation of wind speed. For example, a generator 14 having a rated electrical frequency of 50 Hz for full-power output may generate electricity at a corresponding variable frequency in a range between about 20 Hz and about 50 Hz, according to changes in wind speed. At lower wind speeds, the generator may operate near 20 Hz, while at higher wind speeds, it may operate near 50 Hz.

    [0020] The example first arrangement 10 further includes an AC-to-AC converter 18 that is configured to convert the electricity from the generator 14 into electricity that is output from the AC-to-AC converter 18 at a fixed low frequency, denoted as f2 in the diagram, for offshore collection at the fixed low frequency. The fixed low frequency is lower than the targeted utility grid frequency. In some situations it may be beneficial to choose this fixed low frequency to be a value of about one-third of the utility grid frequency, which is denoted as f3 in the diagram. Note that the AC-to-AC converter 18 operates on the electricity output from the generator 14 directly in cases where the step-up transformer 16 is omitted, and indirectly in cases where the step-up transformer 16 is included.

    [0021] In that latter case, the first arrangement 10 further includes the step-up transformer 16 disposed or connected between the generator 14 and the AC-to-AC converter 18. The step-up transformer 16 has a rated frequency that matches or corresponds to the rated electrical frequency of the generator 14 in the first arrangement. That is, the rated frequency of the transformer 16 complements the rated frequency of the generator 14 and the generally higher electrical frequencies obtained with the disclosed configuration of the arrangement 10 advantageously results in the step-up transformer 16 having a lighter and more compact build than would be practical if the transformer 16 were rated, for example, for operation at or below 20 Hz.

    [0022] The step-up transformer 16 is configured to step up a voltage of the electricity output from the generator 14, and thereby output electricity at a stepped-up voltage. Correspondingly, the AC-to-AC converter is configured to convert the electricity output at the stepped-up voltage from the step-up transformer 16. That is, the AC-to-AC converter 18 operates on the electricity at the stepped-up voltage. However, this electricity is still considered as being from the generator 14, inasmuch as it is directly obtained by stepping up the output voltage of the generator 14.

    [0023] In one example of such an embodiment, the generator 14 is configured to output electricity in a voltage range of about 690 V to about 13 KV and the step-up transformer 16 is configured to output electricity in a voltage range of about 13 KV to about 72 KV. In the same or other embodiments, the AC-to-AC converter 18 is configured to output electricity at a fixed low frequency in the range of about 16 Hz to about 20 Hz. See the circled number annotations in Fig. 1 for reference.

    [0024] Referring to these circled annotation numbers as "Item" numbers, Item 1 denotes the variable first rotational speed of the wind turbine 8. Item 2 denotes the higher variable second rotational speed of the gearbox output, as mechanically derived from the wind turbine input. Item 3 denotes the electricity output from the generator 14, which has a first voltage and the variable first frequency.

    [0025] Continuing with the Item references, Item 4 denotes the electricity output from the step-up transformer 16, having a stepped-up voltage relative to the generator voltage. This stepped-up voltage may be referred to as a second voltage level, which is higher than the first voltage level provided by the generator 14. Because the step-up transformer 16 is included in some embodiments and not in others, the input to the AC-to-AC converter 18 is marked with Item 3 or Item 4, indicating that the AC-to-AC converter 18 may receive electricity at the first or second voltage level. In either case, the AC-to-AC converter 18 outputs electricity having a fixed low frequency, which is denoted as Item 5. It will be understood that the electricity at the output of the AC-to-AC converter 18 may be at the generator voltage, in embodiments that omit the step-up transformer 16, or at the stepped-up voltage of the step-up transformer 16, in embodiments that include the step-up transformer 16.

    [0026] One further sees that the feeders 22 operate at whatever voltage is output from the AC-to-AC converters 18 that are coupled to each respective feeder 22. Thus, the Item 5 designation is propagated into the low-frequency offshore collection grid 20 and is carried across the bus or buses 26 within the offshore collection grid 20, for input to the substation step-up transformer 28. Correspondingly, the step-up transformer 28 steps up the collection grid voltage to a higher voltage, which may be referred to as a third voltage level or a transmission voltage, denoted by Item 6. This latter designation indicates that the voltage output from the step-up transformer 28 is the voltage used for the low-frequency high-voltage transmission system 32.

    [0027] While it is contemplated to have a system 40 that includes only a first arrangement 10 as set forth above, other embodiments of the system 40 include a plurality of like arrangements 10, including the first arrangement 10. Each arrangement 10 is associated with a corresponding one of the wind turbines 8 in an offshore wind farm and each includes a gearbox 12, generator 14, and AC-to-AC converter 18. The "overall" system 40 in such embodiments further comprises one or more feeders 22 comprising an offshore low-frequency collection grid 20. Each such feeder 22 is configured to collect the electricity output from the AC-to-AC converter 18 of each arrangement 10. That is, each feeder 22 is associated with one or more of the arrangements 10 and is configured to "collect" the electricity output from the associated arrangements 10 at the fixed low frequency.

    [0028] The offshore low-frequency collection grid 20 includes a substation 30 having a common step-up transformer 28 that is configured to step up the electricity collected by one or more of the feeders 22. Further, as previously noted, the offshore low-frequency collection grid is configured to output electricity at a stepped-up voltage for transmission to an onshore electric grid 38 via a low-frequency high-voltage transmission system 32. In some embodiments, each feeder 22 is configured for parallel collection of the electricity output by those arrangements 10 among the plurality of arrangements 10 that are coupled to the feeder.

    [0029] Fig. 2 illustrates a related method 200 of obtaining electricity from an offshore wind turbine farm. The method 200 includes mechanically converting (Block 202) a variable first rotational speed of a wind turbine 8 into a corresponding higher variable second rotational speed, and generating (Block 204) electricity at a variable first frequency, based on driving a generator 14 at the variable second rotational speed. The generator 14 has a rated electrical frequency for full-power output in a range from about 50 Hz to about 150 Hz. Thus, while the nominal frequency of the electricity output from the generator 14 may be taken as its rated frequency, the actual electricity will have a variable first frequency that is a function of the wind speed.

    [0030] The method 200 thus includes converting (Block 208) electricity output from the generator 14 into electricity at a fixed low frequency for offshore collection at the fixed low frequency. The fixed low frequency is lower than the grid frequency of the onshore electric grid 38.

    [0031] Some embodiments include the further step or operation of stepping up (Block 206) the voltage of the electricity output from the generator 14, in advance of the conversion operation in Block 208. For example, each arrangement 10 includes a step-up transformer 16 connected between the generator 14 and the AC-to-AC converter 18 in the same arrangement 10. When included, the step-up transformer 16 has a rated electrical frequency that matches or otherwise corresponds to the rated electrical frequency of the generator 14.

    [0032] The method 200 in some embodiments includes the further steps or operation of collecting (Block 210) the electricity output from the AC-to-AC converter used in Block 208 to obtain the electricity at the fixed low frequency, along with the electricity produced from any like converters 18 associated with other wind turbines 8 in the offshore wind farm, via a low-frequency offshore collection grid 20, and stepping up (Block 212) the voltage of the electricity output from the low-frequency offshore collection grid 20, for transmission to onshore equipment 36 via a low-frequency high-voltage transmission system 32. The onshore equipment 36 provides whatever frequency and/or voltage adjustments are required with respect to the onshore electric grid 38.

    [0033] Referring back to Fig. 1 momentarily, the wind turbines 8 may be grouped and connected to different feeders 22 of the low-frequency offshore collection grid 20. In embodiments where each arrangement 10 includes a step-up transformer 16 between the generator 14 and the AC-to-AC converter 18, the output of the wind turbine 8 associated with each such arrangement 10 is made to "match" the desired voltage and frequency of the collection grid 20. In other words, the variable frequency and variable voltage output of each generator 14, which operates under varying wind speeds, is transformed to the rated frequency and rated voltage of the low-frequency offshore collection grid 20-e.g., an rated frequency of 20 Hz and a rated voltage of 33 KV. Advantageously, then, such arrangements 10 allow multiple wind turbines 8 to be connected in parallel to a given feeder 22. A feeder 22 operated at, say 33 KV, may transfer 30-50MW of electric power economically. In a contemplated example, as many as ten wind turbines 8 are associated with a given feeder 22, each having a rated capacity of 5 MW, with additional feeders 22 obtaining electricity from further pluralities of wind turbines 8. The electricity is "collected" in parallel on each such feeder 22 and aggregated at the substation 30.

    [0034] As non-limiting examples of other contemplated architectures, Figs. 3A-3C illustrate various cluster-based collection architectures that are implemented by the low-frequency offshore collection grid 20 in various different embodiments. To appreciate these configurations, consider a system 40 in which generators 14 in the plurality of arrangements 10 are configured to output electricity in a voltage range of, say, 6.6 KV to 13.8 KV. Of course, higher output voltages may be configured, too. At such voltages, it is economical to couple the output of each generator 14 to the AC-to-AC converter 18 in the same arrangement 10, without use of the intervening step-up transformer 16.

    [0035] The cluster-based collection architectures of Figs. 3A-3C are particularly interesting in such cases. For example, Fig. 3A illustrates an example cluster comprising eight arrangements 10-each associated with a wind turbine 8-that are connected to one cluster platform substation 30 directly. There may be multiple such clusters in the low-frequency offshore collection grid 20.

    [0036] Fig. 3B illustrates a similar cluster, but one in which nine arrangements 10 are included in the cluster, by virtue of including a wind turbine 8 and corresponding arrangement 10 directly on the same platform as used to support the substation 30. Fig. 3C provides yet another variation in which fifteen wind turbines 8-not explicitly shown-have their respective arrangements 10 connected to one cluster platform substation 30 directly, or via short feeders.

    [0037] Cluster collection of wind turbines may be more suitable for medium sized wind farms. The collected wind powers are aggregated at the cluster platform substation. Step-up transformers-e.g., a step-up transformer 28 acting as a common step-up transformer for the cluster-are used to boost the voltage of the low-frequency offshore collection grid 20 to a higher, transmission voltage, for transmission to onshore equipment 36.

    [0038] Fig. 4 illustrates another variant of the cluster architecture, in which each arrangement 10 omits the AC-to-AC converter 18, and AC-to-AC conversion to the fixed low-frequency is instead handled by one or more AC-to-AC converters 50 that are centrally located, preferably on the same platform used to support the substation 30. Note that in the cluster-based architecture, the protective device 24 corresponding to a faulty wind turbine 8 or to a faulty arrangement 10 may be used to disconnect from the affected arrangement 10.

    [0039] Notably, modifications and other embodiments of the disclosed invention(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention(s) is/are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.


    Claims

    1. A system (40) configured for obtaining electricity in an offshore wind turbine farm and including a first arrangement (10) that comprises:

    a gearbox (12) configured to mechanically convert a variable first rotational speed of a wind turbine (8) into a higher variable second rotational speed;

    a generator (14) having a rated electrical frequency for full-power output in a range from about 50 Hz to about 150 Hz, and configured to be driven at the variable second rotational speed by an output of the gearbox (12) and to thereby generate electricity at a correspondingly variable first frequency; characterized in that it further comprises

    an AC-to-AC converter (18) configured to convert the electricity from the generator (14) into electricity output from the AC-to-AC converter (18) at a fixed low frequency for off-shore collection at the fixed low frequency, wherein the fixed low frequency is lower than a utility grid frequency, and

    a step-up transformer (16) having a rated electrical frequency corresponding to the rated electrical frequency of the generator (14), wherein the step-up transformer (16) is connected between the generator (14) and the AC-to-AC converter (18), wherein the step-up transformer (16) is configured to step up a voltage of the electricity output from the generator (14), and thereby output electricity at a stepped-up voltage, and wherein the AC-to-AC converter (18) is configured to convert the electricity output at the stepped-up voltage from the step-up transformer (16).


     
    2. The system (40) of claim 1, wherein the generator (14) is configured to output electricity in a voltage range of about 690 V to about 13 KV and wherein the step-up transformer (16) is configured to output electricity in a voltage range of about 13 KV to about 72 KV.
     
    3. The system (40) of claim 1, wherein the AC-to-AC converter (18) is configured to output electricity at a fixed low frequency in a range of about 16 Hz to about 20 Hz.
     
    4. The system (40) of claim 1, further comprising:

    a plurality of like arrangements, including the first arrangement; and

    one or more feeders (22) comprising an offshore low-frequency collection grid (20);

    wherein each feeder (22) is configured to collect the electricity output from the AC-to-AC converter (18) of each arrangement that is coupled to the feeder (22).


     
    5. The system (40) of claim 4, wherein the offshore low-frequency collection grid (20) includes a substation (30) having a common step-up transformer (28) that is configured to step up the electricity collected by one or more of the feeders (22), and to correspondingly output electricity at a stepped-up voltage for transmission to an onshore electric grid (38) via a low-frequency, high-voltage transmission system (32).
     
    6. The system (40) of claim 4, wherein each feeder (22) is configured for parallel collection of the electricity output by those arrangements among the plurality of arrangements that are coupled to the feeder.
     
    7. A method of obtaining electricity from an offshore wind turbine farm comprising:

    mechanically converting a variable first rotational speed of a wind turbine (8) into a corresponding higher variable second rotational speed;

    generating electricity at a variable first frequency via a generator (14) having a rated electrical frequency for full-power output in a range from about 50 Hz to about 150 Hz and driven at the variable second rotational speed;

    converting electricity output from the generator (14) into electricity at a fixed low frequency for offshore collection at the fixed low frequency wherein the fixed low frequency is lower than a utility grid frequency, and

    stepping up a voltage of the electricity output from the generator (14) at the variable first frequency via a transformer (16) having a rated electrical frequency corresponding to the rated electrical frequency of the generator (14), to obtain electricity at a stepped-up voltage and at the variable first frequency, and wherein said step of converting the electricity output from the generator (14) to electricity at the fixed low frequency comprises converting the electricity at the stepped-up voltage and at the variable first frequency into the electricity at the fixed low frequency.


     
    8. The method of claim 7, further comprising obtaining electricity at the fixed low frequency in like manner from a plurality of wind turbines (8) and collecting such electricity at the fixed low frequency from the plurality of wind turbines, via one or more feeders (22) operating as an offshore low-frequency collection grid.
     
    9. The method of claim 8, further comprising stepping up a voltage of the electricity, as collected via the one or more feeders (22), to output electricity at a stepped-up voltage and at the fixed low frequency, for transmission to an onshore electric grid (38) via a low-frequency, high-voltage transmission system (32).
     
    10. The method of claim 8, further comprising, for each feeder (22) among the one or more feeders, using parallel electrical connections for each wind turbine (8) associated with the feeder (22).
     
    11. A system (40) configured for obtaining electricity in an offshore wind turbine farm that includes a plurality of wind turbines (8), wherein the system comprises:

    an arrangement (10) corresponding to each wind turbine (8), each arrangement comprising:

    a gearbox (12) configured to mechanically convert a variable first rotational speed of the wind turbine (8) to a corresponding higher variable second rotational speed;

    a generator (14) having a rated electrical frequency for full-power output in a range from about 50 Hz to about 150 Hz, and configured to be driven by the gearbox (12) at the variable second rotational speed and thereby output electricity at a variable first frequency; and

    an AC-to-AC converter (18) configured to convert electricity from the generator (14) into electricity output from the AC-to-AC converter (18) at a fixed low frequency that is lower than a utility grid frequency;

    a step-up transformer (16) connected between the generator (14) and the AC-to-AC converter (18), and wherein the step-up transformer (16) has a rated electrical frequency corresponding to the rated electrical frequency of the generator (14) in that same arrangement (10) and is configured to step up a voltage of the electricity output from the generator (14) and thereby output electricity at a stepped-up voltage and at the variable first frequency, and wherein the electricity output from the AC-to-AC converter (18) at the fixed low frequency is obtained from the electricity output from the step-up transformer (16), and

    an offshore low-frequency collection grid (20) comprising one or more feeders (22), each feeder associated with one or more of the arrangements (10) and configured to collect the electricity output from the associated arrangements at the fixed low frequency.


     
    12. The system (40) of claim 11, wherein the offshore low-frequency collection grid (20) includes a step-up transformer (28) configured to step up the electricity collected by the one or more feeders (22) and thereby output electricity at a stepped up voltage and at the fixed low-frequency, for transmission to onshore equipment (36) via a low-frequency, high-voltage transmission system (32).
     
    13. The system (40) of claim 11, wherein the offshore low-frequency collection grid (20) includes a substation (30) having a common step-up transformer (28) that is configured to step up the electricity collected by one or more of the feeders (22), and to correspondingly output electricity at a stepped-up voltage for transmission to an onshore electric grid (38) via a low-frequency, high-voltage transmission system (32).
     


    Ansprüche

    1. System (40), das dafür ausgelegt ist, elektrische Energie in einem Offshore-Windturbinenpark zu gewinnen, und das eine erste Anordnung (10) aufweist, welche umfasst:

    ein Getriebe (12), das dafür ausgelegt ist, mechanisch eine variable erste Drehgeschwindigkeit einer Windturbine (8) in eine höhere variable zweite Drehgeschwindigkeit umzuwandeln;

    einen Generator (14) mit einer elektrischen Nennfrequenz für Vollleistungsabgabe in einem Bereich von ungefähr 50 Hz bis ungefähr 150 Hz und dafür ausgelegt, von einem Abtrieb des Getriebes (12) mit der variablen zweiten Drehgeschwindigkeit angetrieben zu werden und dadurch elektrische Energie mit einer entsprechend variablen ersten Frequenz zu erzeugen;

    dadurch gekennzeichnet, dass es ferner umfasst:

    einen Wechselstrom-Wechselstrom (AC-AC)-Wandler (18), der dafür ausgelegt ist, die elektrische Energie vom Generator (14) in elektrische Energie umzuwandeln, die vom AC-AC-Wandler (18) mit einer festen niedrigen Frequenz abgegeben wird, zur Offshore-Sammlung mit der festen niedrigen Frequenz, wobei die feste niedrige Frequenz niedriger als eine Versorgungsnetzfrequenz ist, und

    einen Aufwärtstransformator (16) mit einer elektrischen Nennfrequenz, die der elektrischen Nennfrequenz des Generators (14) entspricht, wobei der Aufwärtstransformator (16) zwischen den Generator (14) und den AC-AC-Wandler (18) geschaltet ist, wobei der Aufwärtstransformator (16) dafür ausgelegt ist, eine Spannung der elektrischen Energie, die vom Generator (14) abgegeben wird, hochzusetzen und dadurch elektrische Energie mit einer hochgesetzten Spannung abzugeben, und wobei der AC-AC-Wandler (18) dafür ausgelegt ist, die mit der hochgesetzten Spannung vom Aufwärtstransformator (16) abgegebene elektrische Energie umzuwandeln.


     
    2. System (40) nach Anspruch 1, wobei der Generator (14) dafür ausgelegt ist, elektrische Energie in einem Spannungsbereich von ungefähr 690 V bis ungefähr 13 KV abzugeben, und wobei der Aufwärtstransformator (16) dafür ausgelegt ist, elektrische Energie in einem Spannungsbereich von ungefähr 13 KV bis ungefähr 72 KV abzugeben.
     
    3. System (40) nach Anspruch 1, wobei der AC-AC-Wandler (18) dafür ausgelegt ist, elektrische Energie mit einer festen niedrigen Frequenz in einem Bereich von ungefähr 16 Hz bis ungefähr 20 Hz abzugeben.
     
    4. System (40) nach Anspruch 1, ferner umfassend:

    mehrere gleichartige Anordnungen, die die erste Anordnung einschließen; und

    eine oder mehrere Zuleitungen (22), die ein Offshore-Niederfrequenzsammelnetz (20) umfassen;

    wobei jede Zuleitung (22) dafür ausgelegt ist, die elektrische Energie, die vom AC-AC-Wandler (18) abgegeben wird, von jeder Anordnung zu sammeln, die mit der Zuleitung (22) verbunden ist.


     
    5. System (40) nach Anspruch 4, wobei das Offshore-Niederfrequenzsammelnetz (20) eine Unterstation (30) mit einem gemeinsamen Aufwärtstransformator (28) aufweist, welcher dafür ausgelegt ist, die von einer oder mehreren Zuleitungen (22) gesammelte elektrische Energie hochzusetzen und entsprechend elektrische Energie mit einer hochgesetzten Spannung für die Übertragung an ein Offshore-Stromnetz (38) über ein Niederfrequenz-Hochspannungs-Übertragungssystem (32) abzugeben.
     
    6. System (40) nach Anspruch 4, wobei jede Zuleitung (22) für paralleles Sammeln der elektrischen Energie, die von denjenigen Anordnungen der mehreren Anordnungen, die mit der Zuleitung verbunden sind, abgegeben wird.
     
    7. Verfahren zum Gewinnen von elektrischer Energie von einem Offshore-Windturbinenpark, umfassend:

    mechanisch eine variable erste Drehgeschwindigkeit einer Windturbine (8) in eine höhere variable zweite Drehgeschwindigkeit umzuwandeln;

    elektrische Energie mit einer variablen ersten Frequenz über einen Generator (14) zu erzeugen, der eine elektrische Nennfrequenz für Vollleistungsabgabe in einem Bereich von ungefähr 50 Hz bis ungefähr 150 Hz aufweist und mit der variablen zweiten Drehgeschwindigkeit angetrieben wird;

    die elektrische Energie, die vom Generator (14) abgegeben wird, in elektrische Energie mit einer festen niedrigen Frequenz zur Offshore-Sammlung mit der festen niedrigen Frequenz umzuwandeln, wobei die feste niedrige Frequenz niedriger als eine Versorgungsnetzfrequenz ist, und

    eine Spannung der elektrischen Energie, die vom Generator (14) mit einer variablen ersten Frequenz abgegeben wird, über einen Transformator (16) mit einer elektrischen Nennfrequenz entsprechend der elektrischen Nennfrequenz des Generators (14) hochzusetzen, um elektrische Energie mit einer hochgesetzten Spannung und mit der variablen ersten Frequenz zu gewinnen, und

    wobei der Schritt des Umwandelns der elektrischen Energie, die vom Generator (14) abgegeben wird, in elektrische Energie mit der festen niedrigen Frequenz umfasst, die elektrische Energie mit der hochgesetzten Spannung und mit der variablen ersten Frequenz in die elektrische Energie mit der festen niedrigen Frequenz umzuwandeln.


     
    8. Verfahren nach Anspruch 7, ferner umfassend, elektrische Energie mit der festen niedrigen Frequenz in gleichartiger Weise von mehreren Windturbinen (8) zu gewinnen und derartige elektrische Energie mit der festen niedrigen Frequenz von den mehreren Windturbinen über eine oder mehrere Zuleitungen (22), die als Offshore-Niederfrequenzsammelnetz fungieren, zu sammeln.
     
    9. Verfahren nach Anspruch 8, ferner umfassend, eine Spannung der elektrischen Energie, die über die eine oder mehreren Zuleitungen (22) gesammelt wird, hochzusetzen, um elektrische Energie mit einer hochgesetzten Spannung und mit der festen niedrigen Frequenz für die Übertragung an ein Offshore-Stromnetz (38) über ein Niederfrequenz-Hochspannungs-Übertragungssystem (32) abzugeben.
     
    10. Verfahren nach Anspruch 8, ferner umfassend, für jede Zuleitung (22) der ein oder mehreren Zuleitungen parallele elektrische Verbindungen für jede Windturbine (8), die mit der Zuleitung (22) verknüpft ist, zu verwenden.
     
    11. System (40), das dafür ausgelegt ist, elektrische Energie in einem Offshore-Windturbinenpark zu gewinnen, welcher mehrere Windturbinen (8) aufweist, wobei das System umfasst:

    eine Anordnung (10), die jeder Windturbine (8) entspricht, wobei jede Anordnung umfasst:

    ein Getriebe (12), das dafür ausgelegt ist, mechanisch eine variable erste Drehgeschwindigkeit der Windturbine (8) in eine entsprechende höhere variable zweite Drehgeschwindigkeit umzuwandeln;

    einen Generator (14) mit einer elektrischen Nennfrequenz für Vollleistungsabgabe in einem Bereich von ungefähr 50 Hz bis ungefähr 150 Hz und dafür ausgelegt, von dem Getriebe (12) mit der variablen zweiten Drehgeschwindigkeit angetrieben zu werden und dadurch elektrische Energie mit einer variablen ersten Frequenz abzugeben; und

    einen AC-AC-Wandler (18), der dafür ausgelegt ist, elektrische Energie vom Generator (14) in elektrische Energie umzuwandeln, die vom AC-AC-Wandler (18) mit einer festen niedrigen Frequenz abgegeben wird, die niedriger als eine Versorgungsnetzfrequenz ist;

    einen Aufwärtstransformator (16), der zwischen den Generator (14) und den AC-AC-Wandler (18) geschaltet ist, und wobei der Aufwärtstransformator (16) eine elektrische Nennfrequenz aufweist, die der elektrischen Nennfrequenz des Generators (14) in eben dieser Anordnung (10) entspricht, und dafür ausgelegt ist, eine Spannung der elektrischen Energie, die vom Generator (14) abgegeben wird, hochzusetzen und dadurch elektrische Energie mit einer hochgesetzten Spannung und mit der variablen ersten Spannung abzugeben, und

    wobei die elektrische Energie, die vom AC-AC-Wandler (18) mit der festen niedrigen Frequenz abgegeben wird, aus der elektrischen Energie, die vom Aufwärtstransformator (16) abgegeben wird, gewonnen wird, und

    ein Offshore-Niederfrequenzsammelnetz (20), umfassend eine oder mehrere Zuleitungen (22), wobei jede Zuleitung mit einer oder mehreren der Anordnungen (10) verknüpft und dafür ausgelegt ist, die elektrische Energie, die von den verknüpften Anordnungen mit der festen niedrigen Frequenz abgegeben wird, zu sammeln.


     
    12. System (40) nach Anspruch 11, wobei das Offshore-Niederfrequenzsammelnetz (20) einen Aufwärtstransformator (28) aufweist, welcher dafür ausgelegt ist, die von den ein oder mehreren Zuleitungen (22) gesammelte elektrische Energie hochzusetzen und dadurch elektrische Energie mit einer hochgesetzten Spannung und mit der festen niedrigen Frequenz zur Übertragung an Onshore-Ausrüstung (36) über ein Niederfrequenz-Hochspannungs-Übertragungssystem (32) abzugeben.
     
    13. System (40) nach Anspruch 11, wobei das Offshore-Niederfrequenzsammelnetz (20) eine Unterstation (30) mit einem gemeinsamen Aufwärtstransformator (28) aufweist, welcher dafür ausgelegt ist, die von einer oder mehreren Zuleitungen (22) gesammelte elektrische Energie hochzusetzen und entsprechend elektrische Energie mit einer hochgesetzten Spannung für die Übertragung an ein Offshore-Stromnetz (38) über ein Niederfrequenz-Hochspannungs-Übertragungssystem (32) abzugeben.
     


    Revendications

    1. Un système (40) configuré pour obtenir de l'électricité dans un parc éolien en mer et comportant un premier agencement (10) qui comprend :

    un multiplicateur (12) configuré pour convertir mécaniquement une première vitesse de rotation variable d'une éolienne (8) en une deuxième vitesse de rotation variable plus élevée ;

    une génératrice (14) ayant une fréquence électrique nominale à pleine puissance de sortie dans une gamme d'environ 50 Hz à environ 150 Hz, et configurée pour être entraînée à la deuxième vitesse de rotation variable par une sortie du multiplicateur (12) et pour produire ainsi de l'électricité à une première fréquence proportionnellement variable ; caractérisé en ce qu'il comprend en outre

    un convertisseur CA-CA (18) configuré pour convertir l'électricité issue de la génératrice (14) en électricité délivrée depuis le convertisseur CA-CA (18) à une basse fréquence fixe pour collecte en mer à la basse fréquence fixe, la basse fréquence fixe étant inférieure à une fréquence de réseau électrique, et

    un transformateur élévateur (16) ayant une fréquence électrique nominale correspondant à la fréquence électrique nominale de la génératrice (14), le transformateur élévateur (16) étant branché entre la génératrice (14) et le convertisseur CA-CA (18), le transformateur élévateur (16) étant configuré pour augmenter une tension de l'électricité délivrée depuis la génératrice (14), et délivrer ainsi de l'électricité à une tension accrue, et le convertisseur CA-CA (18) étant configuré pour convertir l'électricité délivrée à la tension accrue depuis le transformateur élévateur (16) .


     
    2. Le système (40) de la revendication 1, dans lequel la génératrice (14) est configurée pour délivrer de l'électricité dans une gamme de tension d'environ 690 V à environ 13 kV et dans lequel le transformateur élévateur (16) est configuré pour délivrer de l'électricité dans une gamme de tension d'environ 13 kV à environ 72 kV.
     
    3. Le système (40) de la revendication 1, dans lequel le convertisseur CA-CA (18) est configuré pour délivrer de l'électricité à une basse fréquence fixe dans une gamme d'environ 16 Hz à environ 20 Hz.
     
    4. Le système (40) de la revendication 1, comprenant en outre :

    une pluralité d'agencements similaires, incluant le premier agencement ; et

    une ou plusieurs lignes d'alimentation (22) constituant un réseau de collecte à basse fréquence en mer (20) ;

    chaque ligne d'alimentation (22) étant configurée pour collecter l'électricité délivrée depuis le convertisseur CA-CA (18) de chaque agencement qui est couplé à la ligne d'alimentation (22).


     
    5. Le système (40) de la revendication 4, dans lequel le réseau de collecte à basse fréquence en mer (20) comporte un poste électrique (30) ayant un transformateur élévateur commun (28) qui est configuré pour augmenter l'électricité collectée par une ou plusieurs des lignes d'alimentation (22), et pour délivrer parallèlement de l'électricité à une tension accrue pour transmission à un réseau électrique à terre (38) par le biais d'un système de transmission haute tension à basse fréquence (32).
     
    6. Le système (40) de la revendication 4, dans lequel chaque ligne d'alimentation (22) est configurée pour une collecte parallèle de l'électricité délivrée par les agencements parmi la pluralité d'agencements qui sont couplés à la ligne d'alimentation.
     
    7. Un procédé d'obtention d'électricité à partir d'un parc éolien en mer comprenant :

    la conversion mécanique d'une première vitesse de rotation variable d'une éolienne (8) en une deuxième vitesse de rotation variable plus élevée correspondante ;

    la production d'électricité à une première fréquence variable par le biais d'une génératrice (14) ayant une fréquence électrique nominale à pleine puissance de sortie dans une gamme d'environ 50 Hz à environ 150 Hz et entraînée à la deuxième vitesse de rotation variable ;

    la conversion de l'électricité délivrée depuis la génératrice (14) en électricité à une basse fréquence fixe pour collecte en mer à la basse fréquence fixe, la basse fréquence fixe étant inférieure à une fréquence de réseau électrique ; et

    l'augmentation d'une tension de l'électricité délivrée depuis la génératrice (14) à la première fréquence variable par le biais d'un transformateur (16) ayant une fréquence électrique nominale correspondant à la fréquence électrique nominale de la génératrice (14), pour obtenir de l'électricité à une tension accrue et à la première fréquence variable, et dans lequel ladite étape de conversion de l'électricité délivrée depuis la génératrice (14) en électricité à la basse fréquence fixe comprend la conversion de l'électricité à la tension accrue et à la première fréquence variable en l'électricité à la basse fréquence fixe.


     
    8. Le procédé de la revendication 7, comprenant en outre l'obtention d'électricité à la basse fréquence fixe d'une manière similaire à partir d'une pluralité d'éoliennes (8) et la collecte de cette électricité à la basse fréquence fixe issue de la pluralité d'éoliennes, par le biais d'une ou plusieurs lignes d'alimentation (22) fonctionnant comme un réseau de collecte en mer à basse fréquence.
     
    9. Le procédé de la revendication 8, comprenant en outre l'augmentation d'une tension de l'électricité, telle que collectée par le biais de la ou des lignes d'alimentation (22), pour délivrer de l'électricité à une tension accrue et à la basse fréquence fixe, pour transmission à un réseau électrique à terre (38) par le biais d'un système de transmission haute tension à basse fréquence (32).
     
    10. Le procédé de la revendication 8, comprenant en outre, pour chaque ligne d'alimentation (22) parmi la ou les lignes d'alimentation, l'utilisation de branchements électriques parallèles pour chaque éolienne (8) associée à la ligne d'alimentation (22).
     
    11. Un système (40) configuré pour obtenir de l'électricité dans un parc éolien en mer qui comporte une pluralité d'éoliennes (8), le système comprenant :

    un agencement (10) correspondant à chaque éolienne (8), chaque agencement comprenant :

    un multiplicateur (12) configuré pour convertir mécaniquement une première vitesse de rotation variable de l'éolienne (8) en une deuxième vitesse de rotation variable plus élevée correspondante ;

    une génératrice (14) ayant une fréquence électrique nominale à pleine puissance de sortie dans une gamme d'environ 50 Hz à environ 150 Hz, et configurée pour être entraînée par le multiplicateur (12) à la deuxième vitesse de rotation variable et produire ainsi de l'électricité à une première fréquence variable ; et

    un convertisseur CA-CA (18) configuré pour convertir l'électricité issue de la génératrice (14) en électricité délivrée depuis le convertisseur CA-CA (18) à une basse fréquence fixe qui est inférieure à une fréquence de réseau électrique ;

    un transformateur élévateur (16) branché entre la génératrice (14) et le convertisseur CA-CA (18), et le transformateur élévateur (16) ayant une fréquence électrique nominale correspondant à la fréquence électrique nominale de la génératrice (14) dans ce même agencement (10) et étant configuré pour augmenter une tension de l'électricité délivrée depuis la génératrice (14) et délivrer ainsi de l'électricité à une tension accrue et à la première fréquence variable, et l'électricité délivrée depuis le convertisseur CA-CA (18) à la basse fréquence fixe étant obtenue à partir de l'électricité délivrée depuis le transformateur élévateur (16), et

    un réseau de collecte en mer à basse fréquence (20) comprenant une ou plusieurs lignes d'alimentation (22), chaque ligne d'alimentation associée à un ou plusieurs des agencements (10) et configurée pour collecter l'électricité délivrée depuis les agencements associés à la basse fréquence fixe.


     
    12. Le système (40) de la revendication 11, dans lequel le réseau de collecte en mer à basse fréquence (20) comprend un transformateur élévateur (28) configuré pour augmenter l'électricité collectée par la ou les lignes d'alimentation (22) et délivrer ainsi de l'électricité à une tension accrue et à la basse fréquence fixe, pour transmission à un équipement à terre (36) par le biais d'un système de transmission haute tension à basse fréquence (32).
     
    13. Le système (40) de la revendication 11, dans lequel le réseau de collecte en mer à basse fréquence (20) comporte un poste électrique (30) ayant un transformateur élévateur commun (28) qui est configuré pour augmenter l'électricité collectée par une ou plusieurs des lignes d'alimentation (22), et pour délivrer parallèlement de l'électricité à une tension accrue pour transmission à un réseau électrique à terre (38) par le biais d'un système de transmission haute tension à basse fréquence (32).
     




    Drawing

















    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description