JP2003501000A - Wind power plant and control method - Google Patents

Abstract

(57) Abstract: At least one wind power generation housing a wind turbine, a generator driven by the wind turbine (1) and an alternating voltage connection (30) connecting a transmission or distribution network (31) and a wind farm. A wind power plant comprising a power plant (29), wherein a frequency converter (34) is connected in an alternating voltage connection (30) on the network side of the plant, and the frequency of the connection between the wind power plant and the converter is networked. And a frequency converter is provided to convert the low frequency in this connection according to the high frequency of the network. Furthermore, the invention also includes a corresponding control method.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION

The present invention relates to a wind turbine plant having a wind turbine, a generator driven by the turbine and at least one wind farm containing an AC voltage connection connecting the power transmission network or the distribution network with the wind farm. The present invention also relates to a control method in such a wind power plant.

The invention is preferably intended for use in such cases as installing a cable underwater in the connection between a generator and a transmission or distribution network. That is, as a result, in a facility in which one or more wind turbines with associated generators are deployed on the sea or on a lake, the cabling extends to a transmission or distribution network arranged on land. is there. While the advantages of the invention described below are discussed in connection with wind turbine installations at sea or lake,
The present invention shows similar effects when a wind turbine and a generator are installed on land,
In that case, the connections do not necessarily have to be constituted by cables, but instead may be in the form of overhead lines or cables, connecting a plurality of wind turbines / generators to the transmission or distribution network.

[0003]

BACKGROUND OF THE INVENTION AND PRIOR ART

In order to realize wind power generation at sea, it is required to set up a huge wind power plant cluster within the restricted area in consideration of economic efficiency. Wind power generation at sea requires a relatively large wind power plant (3 MW or more), and it is expected that the total system power of 50-100 MW will be commensurate with it. To date, such wind power plant plans have envisioned power transmission via conventional AC transmission via a three-phase AC voltage submarine cable system. In that case, the generator is most often a three-phase asynchronous generator. It is true that there are examples of using synchronous generators directly connected to the network, but even in these cases, in principle, generators are used to dampen the power fluctuations caused by wind load fluctuation characteristics. Inevitably requires the installation of complex mechanical spring suspensions between the engine and the engine house. This is because the mechanical action of the rotor motive force of the synchronous generator acts like a spring on a strong alternating voltage network, whereas the asynchronous generator acts like a damper.
A conventional 3 MW output asynchronous generator could possibly generate about 3-6 kV and could be connected in series with a transformer stepping up to, for example, 24 kV in the first stage. If it is a wind power plant with 30-40 wind farms, it will be further equipped with a central transformer that boosts the voltage to 130 kV. The advantage of such a system is that it is inexpensive and does not require complicated accessory systems. The disadvantage is that it is technically difficult to realize long-distance power transmission with a high-voltage AC cable. This is due to the fact that capacitive reactive power is generated as the cable length increases. Therefore, the current flowing through the cable shield and the conductor increases excessively, and it becomes impossible to realize a cable extending over a long distance. Another drawback is that varying wind loads cause voltage changes on the transmission line that can affect nearby electricity consumers. This happens when the network is "weak", ie when the short circuit power is low. "Weak" due to the above-mentioned technical problem of cable length transmission distance
It is required to connect a wind power generation facility (Wind Park) to the network. According to some criteria, the voltage regulation should not be more than 4%. Different countries have different rules, but in principle, the lower the voltage level on a transmission line, the looser the rules. Depending on the time of day, how to handle the voltage fluctuation may be different.
Rapid voltage changes are regulated by rules such as "flicker"
A phenomenon, that is, a blinking light.

The solution according to the invention to the above-mentioned problem of increasing the distance of cables is to transmit electric power by high voltage DC. This allows the cable to connect directly to the network. Another advantage is that DC transmission has lower loss than AC transmission.
From a technical point of view, the cable distance can be infinite. High voltage direct current (HVDC
The link consists of a rectifier station, a transmission line (cable or overhead line), an inverter station and a filter that removes harmonics generated during conversion. An older form of high voltage direct current (HVDC) link that uses a thyristor for rectification and reverse conversion. The thyristor can be switched on but not switched off. Zero-crossing of voltage determined by AC voltage
Because of commutation at, this type of converter is a line commutator.
tating) type. The drawback with this technique is that the converter consumes reactive power, causing the network to send out current harmonics. More recent DC voltage solutions use IGBTs instead of thyristors in converters. I
GBT (Insulated Gate Bipolar Transisto)
r) both switch-off and switch-on are effective, and high switching frequency (H
high switch frequency). This shows that a converter based on a completely different principle called a self-excited commutation converter is possible. In summary, the advantage of a self-excited commutation converter is that it can not only consume but also supply reactive power, thus enabling active compensation of voltage levels on the network side when the network is weak. As a result, this forms a converter which is superior to the prior art so that it can be connected to network elements located close to wind power. The high switching frequency also reduces the problem of harmonics compared to conventional HDVC. However, the disadvantage is that the loss in the conversion station is as high as the price. Self-excited commutation converters are characterized in that the voltage generated by the converter is built up by an abrupt pulse sequence. The potential difference between the pulse array and the sinusoidal voltage of the network is more than the inductance on the network side. Voltage source VSI (Voltage source inverter)
r)) and current source CSI (Current Source Inverter (Current Source)
There are two types of self-excited commutation inverters with slightly different characteristics. The VSI with at least one capacitor on the DC side provides the best power regulation.

For completely different reasons, ie to realize variable rotational speeds of individual wind farms, several experimental wind farms were constructed using a technology similar to the HDVC format. Wind turbine generators are isolated from the network by low voltage level DC links, typically 400V or 600V. In general, the variable rotational speed of the turbine produces an energy gain at the same time that the rotational speed change can be used to eliminate the sudden increase or decrease in power that causes "flicker". But, of course,
It is not possible to eliminate the slow power changes of the natural wind load. The moment of inertia of the turbine can be said to act as an intermediate store of mechanical energy. Asynchronous generators require more expensive and complex rectifiers,
In such a system, a synchronous generator would not be particularly inconvenient, but rather suitable. Direct drive generator (Direct drive generator)
tor) and, consequently, the omission of the gear unit between the turbine and the generator, the generator must be synchronous because of the large number of poles. That is, the direct drive generator is a DC intermediate link (DC-inter).
mediation link) is required. In this configuration, when using a controlled rectifier, the moment can also be actively adjusted by changing the angle of the trigger. In most configurations with variable rotational speed, the pitch control (Pitc) is also used to change the blade mounting angle on the turbine.
External active rotation speed control (External ac
A live rotation control) is provided. The disadvantage of the variable rotation speed by these forms is that the required power generation system price and maintenance of the power generation system at sea are difficult and expensive.

[0006]

[Purpose of the present invention]

An object of the present invention is to deviate from the DC voltage connection described above, and to enable long-distance power transmission and lower loss than the conventional AC voltage wiring, an AC voltage between a wind power generation facility on the sea and an onshore power distribution or transmission network. It is not only to realize the connections, but also to create the possibility at sea to operate at variable rotational speeds without any power electronics. This is extremely meaningful as all maintenance at sea is expensive and difficult to implement. A further object of the present invention is the conventional HVD.
It is to enable the same good reactive power adjustment as the C system.

[0007]

SUMMARY OF THE INVENTION First of all, an object of the present invention is to fix the frequency of a connection between a wind power plant and a converter to be equal to or lower than a network frequency, and convert a low frequency in this connection according to a high frequency of the network. This is accomplished by connecting the frequency converter deployed in the plant to an AC voltage connection on the network side of the plant. Thus, the expression "network side of the plant" means that the frequency converter is located relatively close to the transmission or distribution network, whereas the essence of the connection is between the frequency converter and the wind farm, for example undersea. It means to extend in the form of a cable. This therefore means that the transmission of power during the connection takes place essentially at low frequencies, resulting in longer distance transmission and lower loss requirements than conventional AC voltage connections at constant network frequencies. Indicates. Current network frequencies are typically at levels of 50-60 Hz. If the low frequency of the alternating voltage connection between the frequency converter and the wind farm is, for example, 10 Hz, the voltage is the same as in a 50 Hz network, whereas the capacitive current of the cable is reduced by a factor of 5. . This shows that, for example, a submarine cable can connect a distance five times as long.

The advantage of this idea is that the result is to place the frequency converter close to the transmission or distribution network, that is to say usually on land, which significantly reduces the cost of maintenance and management and the interruption of service in case of power failure. Is also to reduce.

According to a preferred embodiment of the invention, a plurality of wind power plants equipped with asynchronous generators are connected in parallel with an AC voltage connection. The appropriate frequency and the voltage of the AC voltage connection are determined by the size of the wind power plant and the distance from the land, but for a 50 MW wind power plant, a frequency of 130 kV and 10-20 Hz is suitable.

According to an embodiment of the invention, the frequency converter constitutes a DC voltage intermediate link with a variant of an AC / DC converter and an inverter. As a result, it becomes possible to set the variable frequency in the low frequency AC voltage connection similarly to the variable voltage. In particular, a DC / DC converter is preferably formed on the DC voltage intermediate link. In the preferred embodiment, the valves of the frequency converter are composed of IGBTs connected in series, although other types of valves can be used.
In addition, frequency converters other than static converters, that is, rotary frequency converters (rotary frequency c).
Similar to an inverter, other types of frequency converters without a DC link can also be used in the present invention, for example a direct converter called a "Cyclo converter". According to an embodiment which will be described in more detail below, in order to reduce the voltage of the alternating voltage connection between the generator and the frequency converter to a suitable generator voltage level, at least 1 is connected to the generator side of the connection. You may deploy one transformer. In that case, each of the current generators may be equipped with a transformer and, in addition or as a supplement or alternative, a common transformer for all generators. As a result, such a transformer makes it possible to raise the voltage of the alternating voltage connection to a higher level than in conventional generators. The disadvantage of such a transformer is that it is associated with additional costs and a reduction in the overall efficiency of the system. Similarly, since such transformers contain transformer oil that can leak in the event of a power failure or damage, there is also a fire hazard and environmental concern.

With the technology of today's generators involved in wind farms, it is possible to create generators that can handle up to 10 kV, but those that support higher voltages are desirable. Moreover, conventional insulation technology for stator windings is sensitive to temperature changes, humidity, and salinity experienced by wind turbine generators.

According to a particularly preferred embodiment of the invention, a solid insulator is used for at least one winding of the generator, preferably insulated according to claim 14. The winding more particularly comprises the features of a high voltage cable. The generator produced in this way meets the requirements of achieving significantly higher voltages than conventional generators.
It can be realized up to 400 kV. Moreover, such winding insulation systems are less susceptible to changes in salinity, humidity and temperature. It shows that the high output voltage allows the transformer to be completely eliminated, thus avoiding the above mentioned drawbacks of increased cost, reduced efficiency, fire risk and environmental hazards. The latter is because conventional transformers contain oil.

A generator with a winding formed by a cable can be made by passing the cable through a slot formed in the stator for this purpose, the flexibility of the winding cable facilitating this task. To be able to do.

The two semiconductor layers of the insulation system have a potential compensation function (Potential com).
have a penetration function, and as a result reduce the risk of surface heating. The inner semiconductor layer should be in electrical contact with the conductor or part thereof located inside the layer in order to obtain the same potential as this semiconductor layer. The inner layer is firmly fixed to the solid insulator located outside it, and likewise fixes the outer semiconductor layer to the solid insulator. The outer semiconductor layer serves to limit the electric field within the solid insulator.

The semiconductor layer and the solid insulator have essentially the same coefficient of thermal expansion to ensure adhesion between the insulating layer and the solid insulator even when the temperature changes.

The semiconductor layer outside the insulation system is connected to earth potential or a relatively low potential.

The generator has a number of features which have already been mentioned above and are clearly different from the prior art in order to achieve a considerably higher voltage output. The dependent claims define further features, which are explained below.

According to the embodiments of the present invention, the above-mentioned features and other essential features of the generator and thus of the wind power plant are as follows. The windings of the magnetic circuit are formed by a cable containing one or more permanently insulated conductors with a conductor layer and a semiconductor layer outside the solid insulator.
A typical cable of this kind is a cable with cross-linked polyethylene or ethylene-propylene insulation, which has also been developed for the purposes of conductor strands and insulation system features. Cables with a circular cross-section are preferred, but cables with other cross-sectional shapes can be used, for example to achieve a more suitable packing density. Such a cable makes it possible to construct a laminated core of a magnetic circuit in a new and optimal way with respect to slots and teeth. Preferably, the winding is made by gradually increasing the insulator or optimally utilizing the laminated iron core. Preferably, a winding is created, such as a coaxial cable winding that can reduce the number of coil end crossings. Corresponds the slot shape to the cross section of the winding cable so that the shape of the slot extends vertically and / or parallel to the outside of each other and is in the shape of multiple cylindrical openings with compression sections between the stator winding layers Let The shape of the slot corresponds to a given cable cross section and varying thickness of the insulation of the winding. The gradually changing thickness of the insulator makes it possible to have a substantially constant tooth width regardless of the position in the radial direction with respect to the electromagnetic core. The above improvements to the iron core include winding conductors composed of multiple layers combined,
That is, it is not necessary that the insulated stranded wires be accurately transposed and non-insulated and / or insulated from each other. The improvements mentioned above with respect to the outer semiconductor layer show that the outer semiconductor layer is cut into suitable cable lengths and each cut length is directly connected to ground potential.

Using a cable of the type described above makes it possible to maintain the outer semiconductor layer of the cable along its entire length and also to the rest of the plant at ground potential. An important advantage is that the electric field is close to zero in the area of the coil termination outside the outer semiconductor layer. It is not necessary to control the electric field by bringing the outer semiconductor layer to earth potential. This indicates that there is no local concentration in the core, in the coil end regions, or in the transition section between them.

Eddy current losses are low due to a mixture of densely insulated and / or non-insulated strands or transposed strands. The outer diameter of the cable is about 10-40 nm,
The conductor area is about 10-200 mm ² .

According to a further embodiment, a variable transformer is provided on the high voltage side of the inverter.
mer with variable transmission) is arranged.

[0022]

Detailed Description of the Preferred Embodiments

With the supplement of FIGS. 1-3, the construction of a preferred generator 1 in an embodiment of the invention will first be described. FIG. 1 is a schematic view of a sector of the stator 2 in the axial direction.
The generator rotor is shown at 3. Stator 2 is formed from a laminated core in a conventional manner. FIG. 1 shows a sector of a generator corresponding to a pole pitch. The yoke portion (yoke secti) of the iron core located at the outermost portion in the radial direction.
on), a plurality of teeth 5 extend radially inward toward the rotor 3, and these teeth are partitioned by slots 6 in which stator windings are arranged. The cable 7 forming this stator winding is of substantially the same type as that for power distribution, ie PE
It is a high voltage cable that can be formed from an X cable (PEX is cross-linked polyethylene).
The cable of the present invention differs in that it has at least one semiconductor layer on both sides of the conductor and insulating layers, omitting the mechanical external protective PVC layer and usually the metal protective equipment surrounding the distribution cable. . Cables 7 are shown in the schematic diagram of FIG. 1 showing only the center conductor or coil side of each cable. Each slot 6 has a curved cross section with alternating wide portions 8 and narrow portions 9. The wide portions 8 are substantially circular and surround the cable, and the recesses between the wide portions form the narrow portions 9. The dimples serve to fix the radial position of each cable. The cross section of the slot 6 narrows radially inward. The voltage of the cable portion decreases as it approaches the innermost position of the stator 1 in the radial direction. Therefore, a thin cable can be used on the inside, whereas a thick cable is needed on the outside. In the example shown, cables of three different sizes and arranged in three parts 10, 11, 12 of the corresponding slot 6 are used. A winding 13 for auxiliary power is arranged at the outermost part of the slot 6.

FIG. 2 shows a stepwise cut-away view of a high voltage cable used in a generator. The high voltage cable 7 comprises a plurality of stranded wires 15 each and houses one or more conductors 14 having a generally circular cross section. For example, the conductor can be made of copper. The conductors 14 are arranged in the middle of the high-voltage cable 7, and in the embodiment shown, a partial insulation 16 surrounds each conductor. However, it is possible to omit one of the conductors 14, the partial insulator 16. In the embodiment shown, the first semiconductor layer 17 surrounds the conductor 14. Around the first semiconductor layer 17, there is an insulator layer 18 surrounded by a second insulator layer 19, for example a PEX insulator layer. As a result, the concept of "high voltage cable" in this application is that it is not necessary to have a metal protector or an outer protective layer of the type surrounding the distribution cable.

FIG. 3 shows a wind turbine generator equipped with a magnetic circuit of the type described with reference to FIGS. The wind turbine 20 directly drives the generator 1 via the shaft 21. Although the turbine 20 can drive the generator 1 directly, that is, the shaft of the turbine 20 can be rotatably fixed and connected to the rotor of the generator, but between the turbine 20 and the generator 1. It is also possible to provide the gear device 22. For example, a single step planetary gear for changing the rotation speed of a generator with respect to the rotation speed of a turbine.
ing). The stator 2 of the generator is the above-mentioned cable 7
Holds the stator winding 23 composed of The cable 7 can be bare and connected to the jacketed cable 24 via a cable fitting 25.

In FIG. 4, which illustrates a wind power plant in a simple schematic form, two wind power plants 29 each equipped with a generator 1 and connected in parallel are described. The generator includes a field winding 26 and one (or more) auxiliary power windings 2.
Have 7. In the embodiment shown, the generator is Y-wired and the neutral is grounded via each impedance 28.

In FIG. 4, not only the wind turbine (not shown) but also the two wind farms surrounding the generator 1 are shown as 29. An alternating voltage connection 30 connects the two wind farms 29 to a power transmission or distribution network 31. This is a three-phase type here. Typical frequencies for such networks are 50 or 6
It is 0 Hz. The connection 30 has a submerged cable 33 along the section indicated by 32.
Make up. However, instead of underwater cables, one or more overhead lines / cables may also be covered. The compartment 32 is actually quite long.

On the network side of the plant, the frequency converter 34 is connected to the AC voltage connection 30, the frequency converter fixing the frequency of the connection between the wind farm 29 and the converter 34 below the frequency of the network 31, It is arranged to convert the low frequencies in this connection according to the high frequencies of the.

[0028]   As is apparent from the above description, the generator 1 is asynchronous in the example.

The frequency converter 34 is appropriately arranged at an appropriate power plant on land near the network 31. A wind farm 29 is deployed on a suitable base on the sea or lake. On one of these bases or, in particular, on the base arranged for this purpose, the cables extending out of the generator 1 are connected to one another, for example via bus bars, at the point indicated by 35.

In FIG. 4, a method of providing a circuit breaker 36 between the frequency converter 34 and the network 31 and disposing a disconnector on both sides of the circuit breaker 36 is shown.

In the embodiment according to FIG. 4, the generator 1 is directly coupled to the frequency converter.
This is a result of the assumption that the generator 1 is of the design described above with reference to FIGS. 1 and 2, ie a generator capable of producing extremely high voltages.

In the variant according to FIG. 5, the parallel connection point for the generator 1 and the frequency converter 3
4, there is shown a method of deploying a common transformer 38 for the generator 1 which comprises a high voltage at the connection between the transformer and the frequency converter 34,
The aim is to achieve a relatively low voltage between the transformer 38 and the generator 1. This common transformer 38 is arranged on the wind power side of the connection 30, i.e. near the wind farm 29, so that the main part of the connection 30 lies between the transformer 38 and the frequency converter 34. The transformer 38 is appropriately installed on one of the foundations of the wind farm 29 or, if possible, on a dedicated foundation in a suitable position.

The modification of FIG. 6 explains the modification corresponding to FIG. 5, with the exception that the special transformer 39 is provided for each generator 1. As a result, the wind power plants are interconnected in parallel at contacts 35 only at the next stage of the transformer. In such an embodiment, the transformer 3
8 can be omitted and is described in more detail with reference to FIG. further,
It is also possible to maintain the transformer 38 in two stages, in the first stage via the transformer 39 and then by the common transformer 38 in order to step up the voltage from a single wind farm. Is.

In FIG. 7, a possible embodiment of the frequency converter 34 is described. Here, a DC voltage intermediate link comprising an AC / DC converter 40 and an inverter 41 is included. In the DC voltage intermediate link, the DC / DC converter 42 is well accommodated. The inverter 41 is a voltage type self-commutated inverter. Connect capacitors in parallel beyond the DC link of the inverter. In each phase on the AC voltage side of the inverter 41, the network inductance 44 is connected in series.

[0035]   The inverter 41 appropriately includes an IGBT 45.

The AC / DC converter can be established like the inverter 41 and has an inductance 46 in series with each phase on the AC side network. Converter 4
0 may include an IGBT 47. On the DC side there is a capacitor 48 connected in parallel with the IGBT.

The plant has means (not shown) for measuring the active power from the wind power plant and means for measuring the current wind speed. These measuring means are connected to a control unit which is provided in the frequency converter 34, and the control unit controls the frequency adjustment according to typical measurement values. At that connection, a control unit is arranged to control the frequency of the connection 30 in correspondence with the ideal characteristic of the rotational speed of the wind turbine as a function of wind speed. Such frequency control is indicated as "slow". This is based on the fact that it is preferable that the rotational speed of a wind power plant increases linearly with the wind speed to the maximum rotational speed. As a knowledge of wind speed, a relatively slow frequency control is provided on the connection 30 so that an optimum condition results.

An appropriate control unit is provided to control the frequency of the connection 30 by comparing the ideal characteristic of the rotational speed as a power function with the measured and transmitted active power. Such frequency control is commonly referred to as "fast".
This is done with the aim of a rapid power change, which can be realized by, for example, PI adjustment and generation of the transmission power via the DC link, as described with reference to FIG.

As far as the voltage regulation on the connection 30 is concerned, in the simplest way, the control unit is formed by a main part of the frequency range to control the frequency converter 34 which maintains a fixed specific voltage / frequency of the connection. Adjust the voltage.

The invention is not limited to only the explicitly described embodiments. Changes in multiple items are possible as a result, and will be realized by the parties when they come up with the basic idea. Modifications of multiple items and equivalent embodiments are within the scope of the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS By way of reference to the accompanying drawings, below is described an embodiment in line with the subject matter of the present invention.

FIG. 1 is a schematic view of a stator portion of a generator of a wind power generation plant according to the present invention as viewed from above.

2 is a structural view from the cut end of the cable used in the stator winding according to FIG. 1;

FIG. 3 is a partial schematic diagram of an embodiment of a wind power generator according to the present invention.

FIG. 4 is a schematic diagram showing an embodiment of a wind power generation plant according to the present invention.

FIG. 5 is a schematic diagram illustrating an alternative embodiment of the plant.

FIG. 6 is a modified view similar to FIG.

FIG. 7 is an illustration of a possible embodiment of a frequency converter configured in a plant.

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Claims (34)

[Claims] 1. At least one accommodating wind turbine (20), a generator (1) driven by this wind turbine and an alternating voltage connection (30) connecting the transmission or distribution network (31) and the wind farm. A wind power plant comprising a wind power plant (29), in which a frequency converter (34) is connected in an AC voltage connection (30) on the network side of the plant, the connection (30) between the wind power plant and the converter. A) is fixed below the frequency of the network, and a frequency converter is arranged so as to convert the low frequency in this connection according to the high frequency of the network. 2. A frequency converter for changing the frequency and voltage of the wiring (
34) is provided. The plant according to claim 1, wherein the plant is provided. 3. The frequency of the connection (30) is 20 Hz or less, preferably 2-20.
Plant according to claim 1 or 2, characterized in that a frequency converter (34) is provided for fixing in Hz. 4. The plant according to claim 2, characterized in that a frequency converter (34) is provided to fix the voltage value of the connection (30) within 10-400 kV. 5. The frequency converter (34) is an AC / DC converter (40).
Plant according to any one of claims 1 to 4, characterized in that it comprises a DC voltage intermediate link accommodating the inverter and an inverter (41). 6. A plant according to claim 5, characterized in that the DC / DC converter is housed in the DC voltage intermediate link. 7. Inverter (41) is a voltage-source self-commutated inverter and at least one capacitor (43) is connected in parallel over the inverter's DC link. Plant described in. 8. An inverter (41) having a network inductance (44).
The plant according to claim 7, wherein the plant is connected in series to each phase on the AC voltage side of. 9. Plant according to claim 1, characterized in that the valves in the frequency converter (34) consist of IGBTs connected in series. 10. A plurality of generators in cooperation with a corresponding number of wind turbines, interconnected in parallel on the generator side of the connection (30). Plant described. 11. The plant according to claim 1, wherein the generator is an asynchronous type. 12. Plant according to claim 1, characterized in that the wind turbine (20) is connected to the generator (1) via gearing, preferably stepless planetary gearing. . 13. A plant in which the generator (1) comprises at least one winding (7), said winding comprising a solid insulator (18). Plant described in. 14. A winding comprising an insulator system having at least two semiconductor layers (17, 19) each forming a substantially equipotential surface, and a solid insulator () between the semiconductor layers. Plant according to claim 13, characterized in that 18) is arranged. 15. Plant according to claim 14, characterized in that at least one of the semiconductor layers (17, 19) has essentially the same coefficient of thermal expansion as the solid insulator (18). 16. Plant according to any one of claims 13 to 15, characterized in that the winding comprises a high voltage cable (7). 17. The method according to claim 14, characterized in that the innermost part (17) of the semiconductor layer has essentially the same potential as the conductor (14) located inside this layer. Plant. 18. Plant according to claim 17, characterized in that the inner layer (17) of the semiconductor layer is in electrical contact with the conductor (14) or part thereof. 19. Plant according to claim 14, characterized in that the outer layer (19) of the semiconductor layer is connected to a pre-established potential. 20. The plant according to claim 19, wherein the constant potential is a ground potential or a relatively low potential. 21. In order to reduce the voltage of the alternating voltage connection between the generator (1) and the frequency converter (34) to a suitable generator voltage level, at least one on the generator side of the connection (30). 21. Plant according to any of the preceding claims, characterized in that it is equipped with two transformers (38, 39). 22. Plant according to claim 21, characterized in that the transformer (22) is common to all existing generators. 23. Plant according to claim 21, characterized in that each generator is equipped with a specific transformer (39). 24. Each existing generator (1) is connected to each generator (1) by one
1 of the next stage transformer (38) connecting the secondary side to the secondary side and the frequency converter (34)
24. Plant according to claims 21 to 23, characterized in that it has a secondary side of a transformer (39) connected in parallel to the secondary side. 25. The plant according to claim 23, wherein a common transformer (38) is provided for a plurality of generators on the generator side of the connection (30). 26. Plant according to claim 1, characterized in that the connection (30) comprises an underwater cable (33) or an overhead wire or an overhead cable. 27. Means for measuring active power from a wind power plant and means for measuring the current wind speed, the measurement means being connected to a control unit provided in a frequency converter (34), which control unit is generally 27. The plant according to claim 1, wherein the frequency adjustment is controlled by various measured values. 28. Plant according to claim 27, characterized in that a control unit is provided to control the frequency of the connection (30) corresponding to the ideal characteristic via the rotational speed as a function of the wind speed. 29. A control unit is provided for controlling the frequency of the connection by comparing the measured and transmitted active power with the ideal characteristic via the rotational speed as a power function. Or the plant according to 28. 30. A control unit is provided for controlling a frequency converter which maintains a constant specific voltage / frequency of the connection through the main part of the frequency range. Plant. 31. Controlling the operation of a wind power plant comprising at least one wind farm containing a wind turbine and a generator driven by this wind turbine and an electrical connection connecting the generator with a transmission or distribution network. A method of connecting a frequency converter by electrical connection to the network side of a plant using a frequency converter that keeps the frequency of the connection between the wind farm and the converter below the network frequency, and using the frequency converter And converting the low frequencies of this connection to the higher frequencies of the network. 32. The method according to claim 31, characterized in that the frequency value of the connection obtained by comparing the ideal characteristic via the rotational speed as a function of wind speed with the measured wind speed is adjusted. 33. The frequency of the connection using the frequency converter is adjusted on the basis of a comparison between the ideal characteristic via the rotational speed as a power function and the measured active power. Or the method described in 32. 34. The voltage at the connection is adjusted using a frequency converter so as to maintain a constant specific voltage / frequency through the main part of the frequency range. The method described.