WO2012048743A1

WO2012048743A1 - Current-transmitting device for a wind power plant

Info

Publication number: WO2012048743A1
Application number: PCT/EP2010/065344
Authority: WO
Inventors: Peter Steimer; Stephan Ebner
Original assignee: Abb Schweiz Ag
Priority date: 2010-10-13
Filing date: 2010-10-13
Publication date: 2012-04-19

Abstract

For a wind power plant (10), current originating directly from generators (20) of the wind turbines (14) is transmitted to a central station (12) without a transformer being connected therebetween.

Description

POWER TRANSFER DEVICE FOR ONE

WIND POWER PLANT

Technical area

The invention relates to the field of power generation from wind. In particular, the invention relates to an electric power transmission device for a wind power plant, a wind turbine, in particular an offshore wind turbine, the use of the power transmission device in the wind turbine, and a method for transmitting electrical power to a wind turbine For example, a large-scale transmission network.

State of the art

Wind turbines, such as so-called wind farms, serve to generate electrical energy from wind power. These plants are becoming increasingly important as they generate their energy from a renewable energy source, unlike most conventional power plants. Large-scale wind turbines, which are used to generate electrical energy for the nationwide power grid, typically have a plurality of wind turbines. These wind turbines are usually distributed over a large area and can be several 100 m or up to several kilometers apart. Frequently, the wind turbines are built in the sea, such a wind turbine is therefore also called offshore facility. Usually For example, a wind turbine may include a tower on which there is a nacelle equipped with a generator and a rotor attached to the shaft of the generator. The generator is designed to convert mechanical energy from the rotor, whose rotor blades are driven by wind, into electrical energy.

The wind turbine further includes a transformer that transforms the electrical power generated by the generator to the voltage of a first power transmission network that transmits electrical energy from the individual wind turbines to a central point or central station where the electrical energy of the wind turbines then travel the mains voltage of another second large-scale transmission network is transformed, which transmits the electrical energy to the consumers.

This arrangement had the disadvantage that each wind turbine has a transformer. This not only makes the individual wind turbines expensive, but also leads, if one of these components fails or works incorrectly, that a maintenance technician in the worst case in the gondola of a tower several hundred meters high in the sea and possibly even spare parts are transported there which can lead to a considerable maintenance and maintenance costs.

DESCRIPTION OF THE INVENTION It is the object of the invention to reduce the procurement and maintenance costs for a wind power plant.

This object is solved by the subject matter of the independent claims. Further embodiments of the invention will become apparent from the dependent claims.

A first aspect of the invention is a wind turbine.

According to one embodiment of the invention, the wind turbine comprises at least a first wind turbine with a first generator and a second wind turbine with a second generator. It should be understood that the wind turbine may include not only two wind turbines but a large number of wind turbines, or a plurality of wind turbines, each having at least one generator. As already stated, the individual wind turbines may comprise a tower which may be several hundred meters high and may in turn be spaced from one another up to several kilometers apart and from a central station of the wind turbine.

According to one embodiment of the invention, the wind turbine comprises a power transmission device having a power transmission network for transmitting an electric power from the first generator to a central station of the wind turbine and a second electric power from the second generator to the central station. In other words, the plurality of wind turbines are connected to the central station via the power transmission network and thus also the generators are connected to the central station via the power transmission network. The power transmission network can thus include power lines that can be from a few hundred meters to several kilometers long.

In principle, the power transmission network may include a first power line for the first power from the first generator and a second power line for the second power from the second power rato ns, which may be merged before or at the second power station , It is conceivable that the power transmission network has, for example, a star-shaped topology, in which the individual power lines are brought together by the wind turbines or generators only at the central station, or even that the power lines from the wind turbines or from the generators to one or several manifolds are connected. The arrangement with one or more busbars is sometimes referred to as "daisy-chain" topology, and multiple busbars may be merged in front of or at the central station, but it is also possible that only a single bus is present.

The power transmission network and the power lines are usually designed for the transmission of multiphase AC or DC and can have multiple individual conductors. For example, the power transmission network or the power lines for transmitting three-phase current, for example three-phase current, or else carried out by multi-phase current. Normally, a power line for transmitting three-phase three-phase current has four individual conductors.

The central station, which may normally be a building or a platform, which may be located either on land or, in the case of an offshore installation, also on the sea, may be used to connect the wind turbine to a large (another) Power transmission network serve. In this case, the central station is the interface between the (first) power transmission network from the wind turbines to the (second) large-scale transmission network, which in turn can transport the electrical energy over many 1000 km and includes, for example, the transmission line of an electricity supplier. The central station may be located at least several 100 meters from each of the wind turbines, but also several kilometers away,

According to one embodiment of the invention, in the power transmission network for transmitting the electrical power from the generators to the central station, there is no voltage transformation of the first and second electrical currents from a generator voltage to a transmission voltage in front of the central station. In other words, in a wind turbine directly from wind turbine generators power is passed without the interposition of a transformer to the central station. It should be understood that the (first) power transmission network may include other electrical components such as inverters and switches. However, it is possible that the power transmission network does not include a transformer in front of the central station. For example, only a central transformer is arranged in the central station. Alternatively, it is also possible that a plurality of central transformers are arranged in the central station, for example for each wind turbine one.

If the power transmission network includes other electrical components, such as an inverter or a plurality of inverters or switches, it is possible that the power transmission network does not include a transformer between these further electrical components and the wind turbine. The transformer can be arranged only after these electrical components.

Since there is no voltage transformation in the power transmission network in front of the central station, the electric power is conducted from the wind turbines to the central station with the voltage generated by the wind turbines. So with the voltage generated by the generators of the wind turbines. In this case, it is possible for the power transmission network to transmit alternating current or direct current to a first voltage of, for example, 13.8 kV. Such an arrangement of the components of the transmission network can be made possible in that high-power semiconductor modules are scaled in terms of power and voltage, which can be realized inexpensively and relatively low maintenance. As a result, it is possible to use generators for the wind turbines which supply a higher voltage, which can now also be processed directly without voltage transformation by electrical components of the transmission network, such as converters.

According to one embodiment of the invention, the power transmission device comprises a central transformer, which is designed to transform the first and the second current to a network voltage of a further (second) power transmission network. In other words, the central transformer performs a voltage transformation from the first voltage (that is, the generator voltage of the first transmission network) to a second voltage (that is, the mains voltage of the large-area second power transmission network). For example, this voltage transformation can be a transformation from 13.8 KV to 150 kV.

In the above-mentioned star-shaped topology of the (first) power transmission network, the first and second power lines of the first and the first generator may be commonly connected to the transformer, that is, the central transformer for the two generators or the plurality of generators , but can also be used for all generators of the wind power plant for planting. It is also possible that the transformer in the above-mentioned "daisy-chain" arrangement or topology is connected to one of the manifolds or also to all busbars, so that it is possible that the entire wind turbine only a central transformer, which is responsible for the voltage transformation of all wind turbines includes.

According to one embodiment, the central transformer is arranged in the central station or associated with a centrally located wind turbine or turbine. A Wind turbine can also include the central station. In this way, the transformer can be easily installed and maintained.

According to one embodiment of the invention, the power transmission device or the power transmission network comprises further electrical components such as a Umrichtvorrichtung or switch for disconnecting the wind turbines or their generators and / or connected thereto power lines from the wind turbine. According to one embodiment of the invention, the converter device is designed to convert the first current to a mains frequency of the power transmission network and to convert the second current to the network frequency of the power transmission network. In other words, it is possible that the frequency of the electric current in the power transmission network or the power transmission device changes, but not the voltage of the current. Inverting may be changing the frequency of an alternating current, but may also be transforming a direct current into an alternating current or a direct current into alternating current. It is possible that the line frequency of the (first) power transmission network is also the line frequency of the (second) further large-scale power transmission network, for example 50 or 60 Hz.

According to one embodiment of the invention, the converter device is arranged in the central station of the wind power plant or in a centrally located wind turbine or turbine. In other words, the converter device can be a central converter device. Overall, it is thus possible, on the one hand to arrange the transformers or even just a central transformer and a central Umrichtvorrichtung in the central station of the wind turbine. Overall, therefore, locally arranged transformations in the wind turbines and locally arranged inverter can be omitted in the wind turbines, which on the one hand reduces the procurement costs for the entire wind turbine, but also can help to reduce maintenance costs.

According to one embodiment of the invention, the converter device can have a first converter for converting the first current and a second converter for converting of the second stream. The first inverter and the second converter can be two separate devices that can operate both electrically and spatially separated from each other. For example, the first converter may be arranged in the first power line from the first generator and the second converter in the second power line from the second generator. In addition, the two inverters can be connected together with the central transformer.

According to one embodiment of the invention, the first converter is arranged in the first wind turbine. It may also be possible that the second converter is arranged in the second wind turbine. If the two converters are each arranged in the wind turbines assigned to them, it may be possible for the first and the second power line to be brought together or connected to one another before the central station, since it is possible for the electric current to already be present at this point the right frequency and also the right phase has been redirected.

According to one embodiment of the invention, the first inverter is arranged in the central station. It may also be possible for the second converter to be arranged in the central station. If the two inverters are arranged in the central station, power lines run from the individual wind turbines to the central station and it is possible that the above-mentioned star-shaped topology for the transmission network arises.

Overall, it is possible that the inverter either at the beginning of the power lines, that is, the respective generator or in the wind turbine, or even at the end of the power lines, that are located at the central station or in the central station. But it is also possible that is arranged at a part of the wind turbine, the inverter at the wind turbine, for example in the wind turbines, which are relatively close to the central station, but also in another part of the wind turbines, the associated inverter near or is located in the central station.

The wind turbine may, in addition to the power transmission network described so far, include at least one further power transmission network, which is not the previously has described star-shaped topology. This further transmission network may be a DC transmission network and may include other inverters that are part of the Umrichtvorrichtung. According to one embodiment of the invention, the converter device comprises a first rectifier for rectifying the first current into a first direct current and the second rectifier for rectifying the second current into a second direct current, the converter device comprising a converter for generating an alternating current from the first and second direct current includes. In other words, it is possible that the conversion device is an indirect converter, which comprises a plurality of rectifiers, but only one associated power converter or inverter. In this case, a rectifier may be a device that converts an alternating current into a direct current and a converter or inverter in turn a device that converts a direct current into an alternating current.

The rectifiers can be active or passive rectifiers. In this case, an active rectifier may be a rectifier whose function can be controlled, for example, via semiconductor switches, such as transistors or thyristors. By a passive rectifier, for example, a diode rectifier can be understood. Such a passive rectifier can also be combined, for example, with passive fill and compensation networks, in particular with capacitors, in series or shunt circuit (shunt circuit).

According to one embodiment of the invention, the first rectifier is arranged in a first wind turbine and the second rectifier in a second wind turbine. That is, the first rectifier is arranged at the beginning of a first power line and the second rectifier at the beginning of a second power line. Thus, it may be possible for direct current to be transmitted through the power transmission network. According to one embodiment of the invention, the converter connected to the two rectifiers can be arranged as a central power converter in the central station. Overall, it is therefore possible that the (first) power transmission network is also a power transmission network that transmits a high-voltage direct current. According to an embodiment of the invention, the wide transmission network comprises a common power line for transmitting a first and a second current to which a first generator and a second generator are connected, the converter device comprising a common converter for converting the first and second currents which is arranged in the common power line. For example, the generator can be ASM generators (asynchronous generators), which are already synchronized by their structure with the mains frequency. The first and the second power line can therefore be connected together with a common converter, which is arranged, for example, in the central station. Thus, it is possible to provide only one inverter for two or a plurality of generators.

The common power line or the common converter can in turn be connected to the central transformer or one of the central transformers.

According to one embodiment of the invention, the wind turbine comprises a plurality of wind turbines, of which a part of the wind turbines is each connected to a separate inverter and another part is connected to a common converter.

According to one embodiment of the invention, the converter device comprises a direct converter. A direct converter may be a converter which directly generates an alternating current of different frequency from the phases of the alternating current from one or more of the generators without the intermediation of an intermediate circuit with direct voltage. A direct converter may be, for example, a matrix converter. It is possible for the first and / or the second converter and / or also the common converter to be a direct converter.

According to one embodiment of the invention, the converter device comprises an indirect converter. The indirect converter can be a converter which generates a direct current from the phases of the alternating current from the generators with a rectifier and in turn generates an alternating current of different frequency from this direct current with an inverter connected to the rectifier via an intermediate circuit. According to one embodiment of the invention, the further power transmission network is designed to transmit direct current to the central station. This is possible, for example, if one or more inverters are arranged in the wind turbines and one of the central stations is arranged. However, it is also possible that the power network transmits direct current only in sections, for example when the distributor does not operate in the power transmission network between the wind turbines and the wind energy converter central station are arranged. A DC transmitting power transmission network may have a star or daisy chain topology. Advantage of a DC power transmission network may be that with a star topology no synchronization of power phases is necessary, but the lines can be easily connected. Another advantage may be that only one potential-carrying line can be used, in contrast to multi-phase alternating current, where a separate line is usually present for each phase.

According to one embodiment of the invention, the converter device comprises a modular multi-level converter (MMLC). A modular multi-level converter (MMLC), also known as an M2LC converter / inverter / inverter, is an inverter with a large number of series-connected phase modules Such an MMLC power converter can be used as an (active) rectifier, but also as an inverter, for example, the aforementioned rectifiers or inverters or also the first, the second converter or the common converter can use an MMLC converter. An MMLC inverter may be a direct MMLC converter, for example an MMLC matrix converter or an indirect MMLC converter in which separate rectifiers and inverters exchange their energy via a direct current circuit electrical components of the power transmission device carried out, the Mains voltage of the power transmission device to process. In particular, these electrical components include the switches, the wires and the inverters. For example, the inverters include high power switches, such as transistors or thyristors, which are designed to switch the mains voltage. In addition, the Inverter further high performance electrical components, such as diodes and capacitors include, which are designed to process the mains voltage or to stand this. In particular, a wind power plant may be an offshore wind turbine, that is to say at least a part of the wind turbines is arranged in the sea. According to one embodiment of the invention, the wind turbine has a power transmission device as described above and below.

Another aspect of the invention relates to a method of transmitting electrical power to a wind turbine in a power transmission network.

According to an embodiment of the invention, the method comprises the steps of: transmitting a first electrical current from the first generator to a central station of the wind turbine; Transmitting a second electrical current from the second generator to the central station; wherein there is no voltage transformation of the first and second electrical currents from a generator voltage to a transmission voltage in front of the central station.

It should be understood that method steps described with respect to the embodiments of the power transmission device or wind turbine may also be embodiments of the method, and vice versa. Embodiments of the invention will now be described in detail with reference to the accompanying drawings.

Brief description of the drawings

Fig. 1 shows schematically a wind turbine according to an embodiment of the invention. Fig. 2 shows schematically a wind turbine according to an embodiment of the invention.

Fig. 3 shows schematically a wind turbine according to an embodiment of the invention.

Fig. 4 shows schematically a wind turbine according to an embodiment of the invention. Fig. 5 shows schematically a wind turbine according to an embodiment of the invention.

Fig. 6 shows schematically a wind turbine according to an embodiment of the invention.

7 shows a flow chart for a power transmission method according to an embodiment of the invention.

Fig. 8 shows a circuit diagram for a converter according to an embodiment of the invention.

9 shows a circuit diagram for a converter according to an embodiment of the invention. 10 shows a circuit diagram for a converter according to an embodiment of the invention.

Fig. 1 1 shows a circuit diagram of an embodiment of a module for an MMLC converter.

Fig. 12 shows a circuit diagram of an embodiment of a module for an MMLC converter. Fig. 13 shows an embodiment of an MMLC converter.

Fig. 14 shows a circuit diagram of an embodiment of a block for a matrix converter.

Fig. 15 shows a circuit diagram for an embodiment of a matrix converter.

The reference numerals used in the figures and their meaning are listed in summary form in the list of reference numerals. Basically, identical or similar parts are provided with the same reference numerals.

Ways to carry out the invention

1 schematically shows an exemplary embodiment of a wind power plant 10. The wind power plant 10 comprises a central station 12 and wind turbines 14 arranged therefrom. Between the wind turbines 14 and the central station 12, a power transmission network 16 is arranged which comprises a plurality of power lines 18.

Each of the wind turbines 14 includes a generator 20, which is connected to a respective one of the power lines 18. The generator 20 may be, for example, a synchronous motor or motor with permanent magnets that generate, for example, a current 13.8 kV AC voltage during operation. It is also possible for the generators 20 or wind turbines 14 to have series compensation.

In the central station 12, a converter device 22 is arranged, which has a plurality of inverters 24, each of which is connected via one of the power lines 18 directly to one of the generators 20. In addition, in the central station 12, a plurality of switches 26 are arranged, which are connected to one of the inverter 24 and serve to separate the inverter 24 and the associated line 18 and the respective generator 20 from the central generator 28. Also, a central transformer 28 is located in the central station 12 and is connected via the switches 26 to the inverters 22. On its other side, the central transformer 28 is connected to a main supply line 30 of another second large-area transmission network 32.

For reasons of clarity, only one of the power lines 18, the generators 20, the converter 24 and the switch 26 is designated by a reference numeral in FIG. 1 and also in the following figures. These components 18, 20, 24, 26 may be constructed identically, but may also have a different construction.

If the wind turbine is in operation, mechanical wind energy is converted into electrical energy by the wind turbines 14. In this case, each of the generators 20 are electrical alternating current with a voltage of, for example, 13.8 kV, which then passes over the lines 18 of the power transmission network 16 to the central station 12 wi rd. The U m judge 24 direct the com coming from the generators AC to the mains frequency and the phase of the transmission network 32. Subsequently, the transformer 28 transforms the 13.8 kV to, for example, 150 kV, which is used in the large-area transmission network 32.

The fact that each of the wind turbines 14 is individually connected to the central station 12, resulting in a star-shaped topology for the power transmission network 1 6. For example, the wind turbines 14 may be arranged in a star shape at substantially the same distance from the central station 12 around the central station.

FIG. 2 shows a further exemplary embodiment of a wind power plant 10 having a power transmission network 16 with a star-shaped topology. Unlike the wind turbine of FIG. 1, in the wind turbine of FIG. 10, each of the inverters 24 is disposed at the wind turbine 14. The wind power plant of FIG. 10 thus has a (decentralized) converter device 22 distributed over the entire wind turbine.

FIG. 3 shows a further exemplary embodiment of a wind power plant 10 having a power transmission network 16 with a star-shaped topology. Analogous to the wind turbine 1, a generator 20 is arranged in each of the wind turbines 14. However, in contrast to the wind turbines of FIGS. 1 and 2, the wind turbine 10 has an inverter device 22 with a common converter 34. Such an arrangement is possible when the generators 20 are, for example, asynchronous generators that are already synchronized with the network 32. The common converter 34 can take on the task of carrying out a speed compensation for the generators in weak wind or of ensuring that the wind turbine 10 fulfills so-called "grid codes" specified by the grid operators However, these tasks can also take over the inverter 24 in the other embodiments.

In addition, the wind turbine 10 in the central station 12 still a central switch 36, with which the inverter 34 and the generators 20 can be separated from the network 32 and the central transformer 28 together.

4 shows a further embodiment of a wind turbine 10 in a schematic form. The wind turbine of Fig. 4 corresponds to the electrical circuit of the individual components of the wind turbine of Fig. 2, but the switches 26 are arranged in the wind turbine 14 and the electrical lines 18 are connected to a common line 38 a or a common line 38 b, the be merged at the central station 12. The common lines 38a and 38b are connected to the central transformer 28 in the central station. Instead of arranging a local converter 24 in each of the wind turbines 14, it is also possible in the wind power plant of FIG. 4 to provide a central common converter 34 analogously to FIG.

4, the wind turbines 14 are daisy-chained via the lines 18 to one another on one of the common lines 38a, 38b, so that the current transmission network 16 of FIG a "daisy-chain topology."

5 shows schematically another embodiment of a wind turbine 10 with a power transmission network 16 with daisy-chain topology. In each of the Wind turbines 14 of the wind turbine 10 of FIG. 5, a switch 20 and a rectifier 40 are arranged.

With the switch 26 in one of the wind turbines 14, the rectifier 40 can be separated from the respective generator 20. Each of the rectifiers 40 serves to rectify a generator-derived alternating current of, for example, 13.8 kV into a 13.8 kV direct current. For example, the rectifier 40 may be a passive rectifier, such as a diode rectifier or an active rectifier, such as an MMLC converter.

In contrast to the power transmission networks illustrated in FIGS. 1 to 4, the power transmission network of FIG. 5 transmits DC power to the central station 12. The common lines 38a and 38b are connected to a common central inverter 42 which receives the direct current from the rectifiers 40 in an alternating current of the same voltage but with the power frequency of the large-scale transmission network 32 transforms. Via a central switch 36, the inverter 42, the transmission network 16, the rectifiers 40, the switches 26 and the generators 20 can be separated from the transformer 28 and the power transmission network 32. In other words, the switch 36 serves to separate all electrical components of the wind turbine 10, which are upstream of the transformer 28, from this.

Overall, the wind turbines shown schematically in FIGS. 1 to 5 are to say that they are only exemplary embodiments of the fact that no voltage transformation takes place in front of the central station 12. For example, it is possible to combine the wind turbines 10 shown in FIGS. 1 to 5. For example, the power transmission network 16 illustrated in FIG. 5 could have a star-shaped topology, or the same as FIG. 1 to 3 provided power transmission networks 16 could be combined. For example, a plurality of wind turbines analogous to the wind turbine 10 of FIG. 3 could be interconnected with a further number of wind turbines analogous to FIGS. 1 and 2. Another example would be to connect the voltage transmission network 16 shown in FIG. 4 to another star-shaped voltage transmission network 16 analogous to FIGS. 1 and 2 or 3. It would then be such that instead of the connection to the transformer 28, as well it is shown in Figs. 1 to 3, the corresponding connection point is connected to one of the common lines 38a or 38b.

FIG. 6 shows schematically and by way of example how a wind turbine 14, in particular that of an offshore installation, can be constructed. The wind turbine 14 has a base 44 which may be anchored in such a system on the seabed. On the base 44, a tower 46 is mounted, which may have several 100 m in height. At the upper end of the tower 46 is a nacelle 48 which is rotatable relative to the tower 46 and in which a generator 20 is arranged which is mechanically connected to a rotor 52. The electrical energy generated by the generator 20 upon rotation of the rotor 52 is transmitted via the line 18 in the direction of the central station 12. High-performance devices or electrical components 50, such as the switches 26, the rectifiers 40, the inverters 24, etc., are located in the door 48, in the door 46, or in the door sill 44.

FIG. 7 shows a flowchart for a transmission method of electrical energy from the wind turbines 14 into the large-area transmission network 32.

In a step S10, electric power generated by a plurality of generators 20 by wind power is input to the transmission network 16. The electrical energy can be transmitted via electrical lines 18, which form a power transmission network 16 with star-shaped or daisy-chain topology. The electrical energy or the electric current from the generators 20 is not voltage-transformed in front of a central station 12, which is located as an interface between the first transmission network 16 and a second further large-area transmission network 32. For example, the electrical voltage in the entire transmission network 16 can be 13.8 kV.

Optionally, in a step S12, which alternatively can also be carried out before step S10, the electric current can be redirected into power transmission network 16, that is to say the electrical current can also be converted or converted from an alternating voltage into direct voltage or into an alternating voltage of different frequency , For this purpose, an inverter device 22 may be located in the power network 16. The conversion device 22 can be a plurality of local converters 24 in the wind turbines 14, a plurality of inverters 24 in the central station 12 or a common inverter 34 in the central station 12. Furthermore, it is also possible for the converter device 22 to comprise a combination of these converters. Overall, the electric current originating from the generators 20 is converted to a frequency of the large-area transmission network 32, for example 50 or 60 Hz.

In addition, it is possible for the inverter device 22 to include a plurality of local rectifiers in the wind turbines 14 and a central inverter 42 in the central station 12. Thus, it can be achieved, for example, that the transmission of the electrical energy from the wind turbines to the central station takes place in step S10 substantially in the entire power transmission network 16 in direct current. In a subsequent step S14, the current transmitted by the power transmission network 16 is transformed by a central transformer 28 from the voltage in the transmission network 1 6 into the power transmission network 32, for example from 13.8 kV to 150 kV. FIGS. 8 to 10 are circuit diagrams of various possible embodiments of the various inverters 24, 34 shown in FIGS. 1 to 6.

FIG. 8 shows a converter 24, 34, which has a rectifier 40 and an inverter 42. The rectifier 40 is connected to the generator 20 and generates from the AC voltage of the generator 20 DC for a DC circuit 54, which can then be converted by the inverter 42 again in an AC voltage of different frequency, but the same voltage. Between the switch 26 and the AC or power converter 42, a throttle 56 is also arranged. The inverter 24, 34 shown in FIG. 8 is an indirect converter because of the internal DC circuit 54. The rectifier 40 may be a passive rectifier or an active rectifier. For example, it would be possible to use for the rectifier 40 and the inverter 42 each an MMLC power converter, as will be described below. A combination of a passive rectifier 40 with an MMLC inverter 42 is also possible.

FIG. 9 shows a further possibility for a converter 24 or 34, in which a 12-pole generator 20 is connected to two rectifiers 40 which each rectify a part of the phases of the generator 12. The converter 24, 34 shown in FIG. 9 has in its DC voltage circuit 54 an inverter 42 which converts the current from both rectifiers 40 into AC voltage. The rectifiers 40 and inverters 42 of FIG. 9 may be constructed the same as those of FIG. 8 (active / passive rectifiers, MMLC power converters, etc.).

FIG. 10 shows a further circuit diagram for a converter 24 or 34, which has a direct converter 56. The direct converter 56 may also be an MMLC converter, as will be described below.

1 to 13 show circuit diagrams for a so-called MMLC power converter, as it is also described in DE 101 03 031 A1. In such a power converter, the energy stores (that is, the capacitors) are distributed over a plurality of components, which can provide the advantage that the effective energy content of the power converter can be controlled.

1 1 shows the circuit diagram of a first example of such a device 58. The so-called half-bridge circuit 58 has two diodes 60 and two controllable semiconductor switches 62, which may be transistors 62 and thyristors 62, for example. In addition, in the half-bridge 58, an energy store 64 is arranged in the form of a capacitor. The module 58 also has two outputs X1, X2, via which the module 58 can be connected in series with further modules 58, as described below in FIG. 13. FIG. 12 shows a second building block 58 'of an alternative embodiment of a half bridge 58'. The block 58 'shown in FIG. 12 is essentially constructed like the block 58 from FIG. 11. Only the outputs X1 and X2 are connected to other points of the circuit. Referring now to Figure 13, there is shown a circuit diagram for an MMLC power converter 66 for one phase. A phase of an alternating current is connected to the input L of the MMLC power converter 66. The outputs and inputs P and N of the MMLC power converter 66 are connected to a DC circuit, for example the DC circuit 54 of FIGS. 8 and 9. In the inputs and outputs P and N, the power converter 66 still has a respective throttle 68.

The MMLC power converter 66 includes a plurality of series connected half bridges 58 or 58 '. In principle, it is possible to connect an arbitrary number of half-bridges 58 and 58 'in succession via their outputs X1 and X2 in succession, as shown in FIG. In the embodiment of FIG. 13, the output L is connected to the output P via a half-bridge 58, a half-bridge 58 'coupled to the half-bridge 58, and a choke 68 coupled thereto, and the output L is coupled to two half-bridges 58 coupled thereto and one coupled thereto Throttle 68 is connected to the output N. For the combination of two half-bridges, each of the combinations 58, 58 or 58, 58 'or 58', 58 or 58 ', 58' is possible in both branches to the outputs P or L.

FIGS. 14 and 15 are circuit diagrams for a direct converter 70. The principle of a matrix converter is described, for example, in US Pat. No. 6,900,998 B2.

FIG. 14 shows a circuit diagram for a module 72, a so-called full bridge circuit 72 or full bridge 72. The full bridge 72 comprises four diodes 60 and four switches 62, for example transistors 62 or thyristors 62 and an energy store in the form of a capacitor 64 Full bridge 72 is essentially a combination of two half-bridges 58 or 58 'from FIGS. 11 or 12. FIG. 15 shows a circuit diagram for an MMLC matrix converter 70, which has three phases L1, L2, L3 of a first alternating current in three phases L1 ', L2', L3 'of a second alternating current with a second frequency which may differ from the first frequency of the first alternating current. Of course it is possible that in the Fig. 15 illustrated matrix of three times three phases to any number of phases to expand.

At the crossing points of the matrix, the matrix converter 70 has the full bridges 72, which are connected via their inputs or outputs X1 and X2 to a phase of the first alternating current and to another phase of the second alternating current. As shown in the upper left corner of the matrix, several of the half bridges 72 may also be connected in series via their outputs X1 and X2, with the ends of the series connected respectively to one phase of the first current and another phase of the second current are. In this way, a direct MMLC inverter 70 is created.

In contrast to the circuit shown in FIG. 15, such a matrix converter 70 will generally have an equal number of half-bridge modules 72 at each cross-section. In addition, a throttle 68 is provided at at least one end of the inverter modules 72 at the connection point to the phase of the first alternating current.

For the circuits shown in FIGS. 1 to 15, in particular the diodes 60, switches 62, capacitors 64 and chokes 68, it applies that, as already explained above, they are used in converters which supply electric currents of voltages up to, for example, 13 , 8 kV and several 100 A.

In addition, it should be understood that "comprising" does not exclude other elements or steps and "a" or "an" does not exclude a plurality. "Further, it should be noted that features or steps described with reference to one of the above embodiments also can be used in combination with other features or steps of other embodiments described above, and reference signs in the claims are not intended to be limiting. LIST OF REFERENCE SIGNS

10 wind turbine

12 central station

14 wind turbine

16 power transmission network

18 power line

20 generator

22 converter device

24 inverters

26 switches

28 transformer

30 main supply line

32 large-scale transmission network

34 common inverter

36 central switch

38a, 38b common line

40 rectifiers

42 central inverter

44 sockets

46 tower

48 gondola

50 electrical components

52 rotor

54 DC voltage circuit

56 direct drives

58, 58 'half bridge

60 diode

62 thyristor

64 capacitor

66 MMLC power converters

68 throttle ōštrixumrichter

Claims

1 . Wind power plant (12), u comprehensive:

at least one first wind turbine (14) having a first generator (20) and a second wind turbine (14) having a second generator (20),

a power transmission network (16) for transmitting a first electrical current from the first generator (20) to a central station (12) of the wind turbine (10) and a second electrical power from the second generator (20) to the central station (12), an inverter device (22) comprising a first inverter (24) adapted to convert the first current to a grid frequency of the power transmission network (16) and a second inverter (24) adapted to apply the second current to the grid frequency of the power transmission network (16) to rearrange

a central transformer (28) in a central station (12), the central transformer (28) being adapted to transform the first and second currents from a first voltage to a second voltage of a large scale power transmission network (32).

wherein the first inverter (24) in the first wind turbine (14) and the second inverter (24) in the second wind turbine (14) is arranged or the first inverter (24) and the second inverter (24) in the central station (12 ) are arranged

wherein the first inverter (24) and the second inverter (24) are direct converters.

2. A power plant (1 2) according to claim 1, wherein the power device (16) comprises a modular multi-level inverter (MMLC) (66) or a modular multi-level matrix converter (70) ,

3. Wind power plant (10) according to claim 1 or 2, where the wind turbine is an offshore facility.

Wind turbine (10) according to one of the preceding claims,

wherein the power transmission network comprises a first power line for transmitting the first electrical power from the first generator (20) to the central station (12) and a second power line for transmitting the second electrical power from the second generator (20) to the central station (12) ,

Wind power plant (10) according to claim 4,

wherein the first and second power lines are designed for the transmission of multi-phase alternating current.

Wind turbine (10) according to claim 4 or 5,

wherein the first and second power lines are more than a hundred meters long.

Wind turbine (10) according to one of the preceding claims,

wherein the first and / or the second inverter (24) are adapted to change a frequency of the electrical current from the first and / or the second generator (20) into a frequency of the power transmission network (16).

Wind turbine according to claim 7,

wherein the voltage from the first and / or the second generator (20) is equal to the voltage in the power transmission network (16).

Wind turbine according to claim 7 or 8,

wherein the frequency of the power transmission network (16) is equal to the frequency of the large-capacity power transmission network.

Method for transmitting electrical energy of a wind turbine (10) in a power transmission network (16), wherein the wind turbine (10) comprises at least a first wind turbine (14) with a first generator (20) and a second wind turbine (14) with a second generator (20) and a central station (12),

the method comprising the steps:

Transmitting a first electrical current from the first generator (20) to the central station (12) of the wind turbine (10),

Transmitting a second electrical current from the second generator (20) to the central station (12),

Converting the first stream to a grid frequency of the power transmission network (16) having a first direct converter (24),

Converting the second current to the line frequency of the power transmission network (16) with a second direct converter (24),

Transforming the first and second currents from a first voltage to a second voltage of a large-scale power transmission network (32) to a central transformer (28) in a central station (12),

wherein the first inverter (24) in the first wind turbine (14) and the second inverter (24) in the second wind turbine (14) is arranged or the first inverter (24) and the second inverter (24) in the central station (12 ) are arranged.