EP3437171A1 - Method for feeding electrical power into an electricity supply network with a wind park and wind park with black start - Google Patents

Abstract

The invention relates to a method for feeding electrical power into an electricity supply network (1) by means of at least one wind park (WP1) respectively connected to the supply network by means of a network connection point (12), the supply network (1) being operated with a network frequency, and each wind park (WP1) comprising a plurality of wind energy facilities (100), said method comprising the following steps: determining whether the electricity supply network (1) is in operation; starting the at least one wind park (WP1) in a black-start mode in order to produce electrical power for feeding into the supply network (1) when the supply network (1) is not in operation; and operating the at least one wind park (WP1) in a black-start operation, in which electrical power is fed into the supply network (1), thereby operating the supply network (1), the network frequency being pre-defined, in the black-start mode and/or in the black-start operation, by the feeding of the electrical power.

Description

 METHOD FOR POWERING ELECTRIC POWER INTO AN ELECTRIC SUPPLY NETWORK WITH A WIND FARM AND A WIND FARM WITH A BLACK START

The present invention relates to a method for feeding electrical power into an electrical supply network by means of at least one wind farm. Moreover, the present invention relates to a wind farm and the present invention also relates to a control device for carrying out a method according to the invention and a control device for controlling a wind farm according to the invention.

It is known to feed electric power through wind turbines into an electrical supply network, in particular by several combined in a park wind turbines, which feed via a common grid connection point in the electrical supply network. Feeding in with several wind farms in the same electrical supply network at different grid connection points is also known.

Such methods basically require that the network is in operation. Although there are also known methods in which disturbances in the network are also taken into account by wind turbines, the electrical supply network is nevertheless in operation, 5 even if there is a short-term disturbance. Even if a complete voltage dip should be present for a short time, the electrical supply network returns regularly and the wind turbines or wind farms can continue their feed-in.

Thus, for example, international application WO 2005/031941 A1 describes a method in which a wind energy plant remains connected to the grid when a fault occurs in the electrical network and, at the end of the fault, feeds significantly higher power into the grid in order to power the grid support. But here, too, only an existing network, which is in operation and has also returned to a separate operation without interference, supported. 5 These concepts are based on the basic idea that an electrical supply network is at least supplied and managed by a large power plant. In this case, a very large synchronous generator is regularly coupled directly to the network, which takes over this management task and thereby also specifies a network frequency. Can do that Then the decentralized feeders as well as wind turbines or wind farms are oriented.

Island grids, which are thus small and self-contained, in particular if they are actually arranged on a (small) island, then regularly have a so-called network generator. This may for example be a synchronous generator, which is driven by an internal combustion engine, especially a diesel engine. Such a system is described in the published patent application DE 100 44 096 A1. Thus, ultimately, the network is also guided through a directly coupled synchronous generator.

It can be problematic if the electrical supply network is completely precipitated, especially after a blackout, and must be put back into operation.

 The same applies to a first commissioning of an electrical supply network, and this case can hardly occur nowadays, with the exception of small isolated islands, which are not in this application but. In such a restart, in principle, the large power plant by its synchronous generator resume 15 operation. For this purpose, the one or more large power plants will be started up again and then successively connected consumers at appropriate network switching points.

However, such a system can not function if such large power stations with synchronous generators are not connected to the electrical supply network to be put back into operation. Such a problem can also occur for a larger disconnected subnet if, for example, a local blackout has occurred.

One possibility could be to provide network formers for such cases, as is the case with island networks. However, this would have the disadvantage that such network builders would only have to be provided for such recommissioning and thus usually not be needed, because such recommissioning or a first commissioning occurs quite rarely.

The German Patent and Trademark Office has in the priority application for the present application the following prior art research: DE 103 20 087 A1, EP 1 965 483 A1, EP 1 909 371 A2, EP 2 632 012 A1, US 2015/0042092 A1, CN 104953616A, DE 100 30 44 096 A1, WO 2005/031941 A1. The invention is therefore based on the object to address at least one of the above problems. In particular, a solution is to be created to take an electrical supply network or a part thereof without using a large power plant with directly coupled synchronous generator in operation or to put back into operation. At least an alternative solution should be proposed over previously known solutions.

According to the invention, a method according to claim 1 is thus proposed. This procedure is based on a wind farm that is connected to the grid via a grid connection point and that is to feed electrical power into the grid via this grid connection point. This electrical supply network, or simply supply network is to operate at a grid frequency, such as 50 Hz or 60 Hz. It can also be provided to feed with multiple wind farms, each wind farm has multiple wind turbines and a wind farm each via its own network connection point to the Supply network is connected and feeds about it.

The method now proposes that it is first determined whether the electrical supply network is in operation. This determination can be made in particular by the at least one wind farm and, for this purpose, a central control of the wind farm can be present and used. It is also possible, especially if several wind farms are involved, to use a higher-level control device.

If it is determined that the utility grid is not in operation, the at least one wind farm is started in a black start mode to generate electrical power and feed it into the utility grid. The at least one wind farm started in the black start mode is now operated in a black start mode. In this black start operation, electrical power is fed into the supply network and thereby operated the supply network, in particular, put back into service. In this black start mode or black start mode, the mains frequency is predetermined by the input of the electrical power. The grid frequency is thus predetermined by the at least one feeding wind farm. The proposed method thus provides a way to take back an electrical supply network that is not in operation, which is so black in particular, without requiring a large-scale power plant, in particular without requiring a large power plant, the one directly with the Network-coupled synchronous generator has, which specifies the network frequency. The wind farm, possibly several, thus recognizes that the network is not in operation and drives it up independently.

Under an electrical supply network is not understood island network, but an electrical supply network that is not isolated and in particular does not have the one or more wind farms and possibly other decentralized generating units as the only producers. The electrical supply network, which is the basis here, is coupled in normal operation with at least one large power plant, which feeds into this electrical supply network. This may also mean that the electrical supply network that has been determined to be out of service is not coupled to a large power plant at the moment because one has disconnected from the electrical supply network and / or with another subnetwork is connected and this subnet has disconnected from the electrical supply network, which has been determined to be inoperative. In this case, after the starting of the electrical supply network and the commissioning or recommissioning of this electrical supply network, a connection with the said subnetwork and / or the said large power plant can later be made, in order ultimately to restore the normal operation of the electrical supply network.

The electrical supply network considered here can form, for example, a part of the European interconnected network.

The method thus creates a possibility to be put into operation automatically without such a large power plant and this has the advantage that such a commissioning without a corresponding large-scale power plant can be performed on the one hand. It can therefore be put into operation when a connection to a large power plant is disconnected at the moment. But it also has the advantage that commissioning, in particular restarting, if necessary, can be made faster than would be the case with one or more large power plants. This is particularly due to the fact that wind turbines can regulate the use of inverters very quickly and flexibly. If an electrical supply network has failed, this is regularly classified as a serious disorder. Such a disturbance often results in many or all large power plants feeding into this electrical supply network being switched off. Correspondingly, in order to restart the electrical supply network, these large-scale power plants, at least part of them, would first have to be put back into operation or power plants specially designed for black start would have to be started. The recommissioning by means of a wind farm, which is proposed here, can thus possibly provide an improved solution, in particular achieve a faster restart. According to one embodiment, it is proposed that the wind farm is connected via the respective grid connection point to the supply network, wherein the supply network is not in operation before connecting, in particular has no grid frequency and the supply network after connecting the grid frequency by feeding through the at least one wind farm having. The supply network is thus initially not in operation. In particular, it has no network frequency, which can also be used as an indicator for the extent that the supply network is not in operation. Only connecting to the wind farm and feeding electrical power through the wind farm with the appropriate frequency, which thus dictates the wind farm, resulting in that the power grid then has a grid frequency. Preferably, in the black start mode, a frequency generator generates a frequency signal and optionally also a phase signal. This can be made available to the at least one wind farm as a pilot signal and the at least one wind farm then sets the frequency and possibly the phase based on this pilot signal. In particular, such a frequency generator is part of the at least one wind farm, which takes the electrical supply network back into operation here. When using multiple wind farms for commissioning of an electrical supply network, this frequency generator can provide the frequency signal and optionally the phase signal as a pilot signal to all wind farms involved. Especially in this case, it is proposed to provide the frequency generator as a higher-level control means for the multiple wind farms. The local arrangement of the frequency generator, or this higher-level control means, may be in one of the wind farms.

According to one embodiment, it is proposed that one of the wind turbines for the specification of the frequency and optionally for the specification of the phase works as a master system and the other wind turbines adapt to it, in particular sync with it. In addition or alternatively, it is proposed that when using multiple wind farms, a wind farm for the specification of the frequency and optionally for the specification of the phase works as a master park and the other wind farms adapt to it, in particular synchronize with it. In this way, a frequency as a master frequency and optionally a phase can be specified as the lead phase in a simple manner. The master system or the master park can work insofar as a frequency generator or higher-level control means. In that regard, the advantages and features of the above-described frequency generator can be transferred to this master system or this master Park mutatis mutandis. Preferably, electrical energy from an energy store is used to start the at least one wind farm. Optionally, energy from the energy store is also used to feed at least part of the electrical power to be fed in.

Accordingly, an energy storage is provided, which may be arranged centrally in the wind farm, for example. If this energy storage device is comparatively small or has a comparatively low charge, it can be useful to use the energy only for starting the at least one wind farm, ie as energy for the operating devices such as blade pitch drives and in each case an excitation current for exciting the rotor field of a separately excited synchronous generator each of a wind turbine. Also, control processors, including an inverter, can be powered by such energy from an energy store.

If a correspondingly large energy store is provided, its energy can also be used for direct feeding. This can be achieved that a restart of the electrical supply network is also possible if little wind or even no wind in the moment in which the electrical supply network is to be put into operation again. As electrical energy storage come especially as a direct electrical energy storage battery storage into consideration. But there are also electrical energy storage into consideration, which store the energy in a different form, but especially save this energy as electrical see energy, so can deliver. For this purpose, especially gas storage are considered. Electrical capacitors can supplement the electrical storage, especially in electrical battery storage. It is also considered as a particularly preferred embodiment to combine battery storage and other memory and possibly additionally capacitor storage. This can be done by the different memory different speed electrical services are provided. Different properties in terms of the speed of the energy supply on the one hand and the storage capacity in terms of amount of energy on the other hand can be combined so advantageous. According to one embodiment, it is proposed that, before starting the at least one wind farm, a grid impedance is detected at at least one of the respective grid connection points in order to check an operability of the supply grid. Thus, on the one hand between the determination of whether the electrical supply system is in operation, additionally checked the operability. By detecting the network impedance, it can be detected in particular whether there is still a network short circuit or whether the network connection point at which the network impedance is detected is disconnected from the electrical supply network or from a large part of the electrical supply network, or if there is another interference. Preferably, at least one earlier point in time, especially when the electrical supply network was in operation, ie without interference, a comparison impedance or comparison network impedance has been recorded. A comparison of the network impedance now recorded at the grid connection point with such a comparison grid impedance can provide information on whether the grid impedance now detected indicates a problem, in particular suggesting that operability could not exist. Additionally or alternatively, it is proposed that the start in the black start mode be adapted to the detected network impedance. In particular, it can depend on how much power and / or reactive power is initially fed in, how quickly the voltage which is fed in is increased, and in particular also how stable the regulation of the feed is designed. In particular, it is proposed to provide a control reserve depending on the detected network impedance. A control reserve is understood here as the relative, ie percentage, distance of the fed-in power or power to be fed in to the calculated feed-in power at which a stability limit was calculated at which the feed would thus become unstable.

Preferably, the wind farm is not started, if it results from the detected network impedance that a serviceability of the supply network is not given. This is especially the case when the network impedance is particularly large or very small. But it can also qualitatively indicate the network impedance that an operability is not present or at least problematic. That can be, for example be the case when the network impedance has a very high or very low resistive component.

Preferably, at or immediately after starting the at least one wind farm in the black start mode, at least one consumer connected to the utility grid is switched on to serve as a load for the power fed into the utility grid so that an electrical current can flow to that at least one consumer in the utility grid ,

Such a consumer may be an artificial consumer, that is to say one which is provided solely for network support, in particular the starting in black start mode described here. This can be, for example, an electric motor and / or resistor banks for dissipating electrical energy. Preferably, this load is designed to be tolerant to voltage fluctuations, frequency fluctuations and variations in available power.

Particularly preferred may be provided as a load, a rotary electric machine, in particular with flywheel, which can operate in both engine and generator mode. This electric machine can then serve as a load, absorb power and convert this power into a rotational movement. This initially fed-in power or the energy that integrates over time can accelerate this electric rotary machine so that the electrical energy is stored as a kinetic rotational energy. This rotational energy can later be released back into the network and would thus, at least in part, not lost. In addition, such a rotary electric machine can deliver the energy again when needed, when the wind farm is still operating in the black start mode and / or black start mode.

Preferably, a wind turbine of another wind farm and / or another wind farm forms the switchable load. The use of the wind energy plant or the wind farm as a load has the advantage that this wind energy plant or this wind farm can thereby be raised at the same time. This wind energy plant or this other wind farm then initially supports the commissioning of the electrical supply network as a load, but then can work faster as a generating unit or units as soon as it is needed. This may be needed especially when other consumers are switched to this electrical supply network in the black start mode. Preferably, the start in the black start mode is triggered by an external signal of an operator of the electrical supply network or by an external signal of a central control unit. This external signal can thus also be used to determine whether the electrical supply network is in operation, ie to determine that the electrical supply network is not in operation. Additionally or alternatively, such an external signal can be used to determine the operability of the electrical supply network. Accordingly, the network operator and / or the central control unit can determine whether the electrical supply network is operational. According to a preferred embodiment, it is proposed that, before starting in the black start mode, a subsystem of the supply network connected to the network connection point be disconnected in order to be started and operated independently of the remaining part of the supply network. In addition, it is proposed as a supplementary option that in a further step, the separated and operated in the black start operation subnet with the remaining part of the supply network, or a part thereof, synchronized and then reconnected.

Thus, a subnetwork that can be powered up independently of the remainder of the utility network is disconnected from an entire electrical utility network, such as the European Network. The remaining electrical supply network can also be powered up and otherwise. The at least one wind farm thus only needs to start this separate subnet. Preferably, an impedance detection was carried out for this subnet before, when the electrical supply network was still essentially in an optimal state. In this case, it is also possible to extrapolate from an impedance measured in the non-separated subnetwork to an impedance that would result if the subnetwork were separated accordingly.

Preferably, in a further step, the separated and operated in the black start operation subnet with the remaining part of the supply network, or a part thereof, synchronized and then reconnected. Thus, multiple, at least two, subnetworks can be powered up independently, especially until they operate stably. Then, synchronization and reconnection of these subnets, which are initially booted separately, can take place. The supply network preferably has at least one consumer and one conventional generating unit. In particular, the electrical supply network has very many consumers. Accordingly, the use of an essentially standard supply network is proposed here. Preferably, the conventional generation unit has a rated output of more than 200 MW. It is thus provided a conventional generating unit, which is also referred to here as a large power plant. In addition or alternatively, the conventional generating unit has a synchronous generator coupled directly to the supply network. It is thus assumed that a supply network with a basically conventional generator, namely a generator other than a wind turbine or a wind farm. This conventional generation unit is thus constructed to have a synchronous generator directly coupled to the network. Such a synchronous generator would also be able to specify a frequency in the network.

It is envisaged that this conventional generating unit is disconnected from the supply network when the supply network is not in operation. Such an electrical supply network is thus restarted by one or more wind farms, but not by the conventional generating unit.

According to one embodiment, it is proposed that at least two wind farms are provided and these wind farms are started synchronously, in particular start up synchronously, wherein they are matched at least in their frequency and phase relationship, preferably one of the wind farms works as a master park and the other Park or the other parks after this master park. As a result, the re-operation of the electrical supply network by means of two or more wind farms can be made in a simple manner. These at least two wind farms can thus already be supplemented in terms of their deliverable power, ie active power, as well as their deliverable reactive power. Insofar as these at least two wind farms are also located at a distance from one another, a certain homogenization with regard to the wind supply can also be made. If these wind farms are far enough apart, wind changes, especially gusts, can at least partially clear out. This advantage is particularly useful when using more than two, especially significantly more than two, wind farms to fruition.

By providing a wind farm as a master park, the coordination of several wind farms can be implemented in a simple manner. Preferably, multiple wind farms are used and the wind farms exchange data with each other to prepare for a common start in the black start mode, the wind farms at least exchange data on their available power and / or power required in the supply network, and depending on the start in Control black start mode with subsequent operation in black start mode and / or deduce whether it is possible to start in black start mode with subsequent operation in black start mode.

Thus, a data communication between the wind farms is provided. In particular, data about the available power and / or power required in the supply network are exchanged here. The available power of a wind farm depends especially on how strong the prevailing wind in the park is. But there are also other information into consideration, such as whether all wind turbines can be put into operation in the park, or whether one or more wind turbines are in a repair mode, to name just one example. With this data, the commissioning or recommissioning of the electrical supply network can be better planned and coordinated. It also comes into consideration that it turns out in evaluation of these data that a start-up or recommissioning of the electrical supply network is currently not possible.

Preferably, power available to a determination will account for the prevailing wind, expected wind, and / or properties and size of existing storage facilities in the park.

The importance of prevailing wind has already been explained, and the prevailing wind has a major impact on how much power can be taken from the wind at all and thus provided for feeding. When considering expected wind, a weather forecast is preferably taken into account. This can be obtained from a central meteorological institute, such as in Germany the Federal Maritime and Hydrographic Agency. Another possibility is that the wind farm itself determines a prediction, especially from recorded weather data such as the change in air pressure, the temperature and the prevailing wind. Preferably, this meteorological data of several wind farms are evaluated. Preferably also meteorological data of wind farms are used, which are not involved in the commissioning of this electrical supply network. For the determination of available power, characteristics and size of storage devices existing in the park can also be taken into account. Depending on such storage devices can be assessed how fast the park can be started up and / or how much energy and thus power can be fed directly from the storage devices, how much feedable electrical energy so wind is independent.

Incidentally, such electrical storage devices need not be arranged directly in the wind farm, with an arrangement in the park is a preferred embodiment. According to the invention, a control device for controlling the feeding of electrical energy into an electrical supply network is also proposed. The supply takes place here by means of at least one each connected via a grid connection point to the supply network wind farm and the supply network is, as described above, operated at a mains frequency, in particular 50 Hz or 60 Hz. Each wind farm has multiple wind turbines and the control device includes Detection means for determining whether the electrical supply network is in operation. The detection means is provided in particular for measuring or evaluating corresponding measured values as to whether there is a frequency on the network, that is to say it can be recognized. Furthermore, the control device has a signal generator, which can generate and transmit a start signal. Such a start signal is intended to start the at least one wind farm, which is to feed into the supply network, in a black start mode. In this, the wind farm generates electrical power and feeds it into the supply network. Such a start signal is given when the supply network is not in operation, ie when the detection means has determined that the electrical supply network is not in operation.

Furthermore, a guide unit is provided as part of the control device, which leads the at least one wind farm in a black start operation. In this black start operation, electrical power is fed from the at least one wind farm into the supply network, thereby operating the supply network. The guide unit can guide the at least one wind farm at least in such a way that it can specify the active power to be fed in, the reactive power to be fed in and / or its relationship to one another. Additionally or alternatively, it may have the at least one wind farm lead such that it specifies the voltage level with which in the black start mode and the black start mode is fed. For example, it can increase such a voltage value slowly or guide the wind farm so that it receives specifications to increase the voltage accordingly. Thus, also in this black start mode or black start mode, the grid frequency is first predetermined by the feeding of the electrical power through the at least one wind farm.

Preferably, the control device is prepared to carry out a method according to at least one of the embodiments described above or to lead a wind farm, or several wind farms, so that it or they according to a method according to one of the embodiments described above electrical power into the electrical supply network feeds.

Accordingly, it is proposed that the control device coordinates the black start of the electrical supply network. In addition, the invention proposes a wind farm with several wind turbines, which is prepared to execute a method according to at least one of the embodiments described above or to participate in such a method. Accordingly, the wind farm can perform such a method even without the said control device or even without such a control device participate in carrying out the method. For example, the wind farm or one of the wind farms can take over the coordination.

Additionally or alternatively, such a wind farm is prepared to be functionally coupled to a control device according to at least one of the embodiments described above. In particular, this wind farm is prepared to receive the start signal from the control device and also or alternatively to be guided by the guide unit of the control device in the black start operation. The wind farm is thus adapted to the control device both in terms of interfaces and in terms of functional compatibility.

According to the invention, a wind turbine is also proposed, which is prepared for operation in a wind farm according to an embodiment described above. Such a wind turbine can thus participate, which required accordingly electrical values. In particular, it can contribute a portion of the active power to be fed and / or reactive power. Preferably, it may have a ratio of active to reactive power equal to the ratio that the wind farm feeds in total. Additionally or alternatively, it may provide its voltage level corresponding to the respective predetermined value in the black start mode and the black start mode, respectively. This also includes providing such a voltage that takes into account a transmission ratio of one or more transformers connected between it and the grid connection point.

Additionally or alternatively, it is proposed that the wind energy installation include a control device according to one of the embodiments described above. Thus, such a control device may be provided in a wind turbine of the wind farm. For example, a wind farm may include a plurality of wind turbines, some of which are suitable and prepared for a black start mode, but one of which has a described controller and thereby may take the lead of the black start mode. It is particularly advantageous that communication units and connections and possibly communication lines of the wind turbines can also be used for the guidance or coordination of such a black start by means of the control device.

The invention will be described in more detail below by means of embodiments by way of example with reference to the accompanying figures.

Fig. 1 shows a wind turbine in a perspective view.

Fig. 2 shows a wind farm in a schematic representation.

Fig. 3 shows schematically an electrical supply network for illustrating a Wiederbetriebbetriebs.

FIG. 4 shows schematically in a diagram simplified profiles for a voltage U and a power factor coscp for a black start operation.

FIG. 1 shows a wind turbine 100 with a tower 102 and a nacelle 104. The nacelle 104 has a rotor 106 with three rotor blades 108 and a spinner 1 10 arranged. The rotor 106 is set in rotation by the wind in rotation and thereby drives a generator in the nacelle 104 at.

2 shows a wind farm 1 12 with, for example, three wind turbines 100, which may be the same or different. The three wind turbines 100 are thus representative of basically any desired number of wind turbines of a wind farm 1 12. The wind turbines 100 provide their power, namely, in particular, the generated power via an electric parking net 1 14. In this case, the respective generated currents or outputs of the individual wind turbines 100 are added up and usually a transformer 1 16 is provided, which transforms the voltage in the park, to then at the feed point 1 18, which is also commonly referred to as PCC, in the supply network 120th feed. Fig. 2 is only a simplified representation of a wind farm 1 12, for example, shows no control, although of course there is a controller. Also, for example, the parking network 1 14 be designed differently, in which, for example, a transformer at the output of each wind turbine 100 is present, to name just another embodiment.

Fig. 3 shows a supply network 1 in a schematic representation. The electrical supply network 1 contains in this illustration three subnetworks N1, N2 and N3, which can be separated from each other by the switches S2 and S4. In the illustration of FIG. 3, however, these two switches S2 and S4 are closed and these three subnetworks N1-N3 thus form, together with further elements, the electrical supply network 1. The electrical supply network 1, as illustrated in FIG , may also be coupled with other parts, in particular with an overall comprehensive network, such as the European interconnected network, which should be illustrated by the continuation symbol K1. It should be emphasized that Fig. 3 is in many ways only a schematic and illustrative representation. In particular, the symbolized subnetworks N1-N3 can also be connected to one another more strongly, that is to say for example via a plurality of connection points and not just via a switch S2 or S4. Finally, switching elements, transformers, consumers and generators, to name but a few examples, also belong to a supply network or sub-network. Some of these elements will be described below in their meaning for the supply network 1. In the embodiment according to FIG. 3, a first and a second wind farm WP1 or WP2 are provided, which feed into the electrical supply network 1, namely via the switch S3 and the transformer T3 into the subnetwork N2 or via the switch S5 and the transformer T5 in the subnet N3. In the situation shown, the two switches S3 and S5 are closed, the two wind farms WP1 and WP2 are thus connected to the electrical supply network 1 and can feed.

In addition, a large power plant 2 is shown, which could feed via a switch S1 and a transformer T1 in the electrical supply network 1, namely in the subnetwork N 1. In the situation shown, however, the switch S1 is open and the large power plant 2 is thus not fed in the situation shown. Incidentally, the large-scale power plant 2 is only representative of other large-scale power plants, especially those which would feed via a synchronous generator coupled directly to the supply network 1. In that regard, the open switch S1 is representative of the fact that in the situation shown in Fig. 3, no large power plant 2 is currently fed into the electrical supply network.

In addition, an industrial consumer 4 is shown by way of example, which could draw power from the electrical supply network 1 from the electrical supply network 1 via the transformer T6 and the switch S6. In the situation shown, however, the switch S6 is open, thus indicating that in the situation shown the exemplary industrial consumer 4 does not draw power from the electrical supply network 1.

Also symbolically illustrated is a city network 6 which is representative of many individual non-industrial consumers, especially those grouped in a low-voltage network. This urban network 6 could also draw power from the electrical supply network 1, namely via the transformer T7 and the switch S7. In the illustrated situation, however, the switch S7 is open and the urban network 6 thus does not draw any power from the electrical supply network 1 in the situation shown. The exemplary industrial consumer 4 also symbolizes a consumer who also purchases inductive power, at least with a significantly higher proportion as this is the case with the urban network 6. In the situation illustrated in FIG. 3, only the two wind farms WP1 and WP2 are thus currently coupled to the electrical supply network 1. At the moment, they are not feeding any power. In that regard, the two switches S3 and S5 could also be open. It is therefore assumed that the illustrated electrical supply network 1, which can be referred to only as a supply network 1 for the sake of simplicity, has failed, which can also be referred to as black fallen here. The electrical supply network 1 is thus currently not in operation.

It is now measured at the measuring point 8 to determine whether the electrical supply network 1 is in operation. The measurement result is given to the control device 10 and evaluated there. In the control device 10 it is now determined that the electrical supply network 1 is not in operation. This can be particularly determined by the fact that no voltage and / or frequency is detected (although measurement errors can be excluded).

The control device 10 recognizes this and decides whether it is expedient to start the two exemplary wind farms WP1 and WP2 in the black start mode. For this purpose, the control device 10 evaluates further information, namely both information about the state of the electrical supply network 1 and the state of the two wind farms WP1 and WP2.

The state of the electrical supply network 1 can also be detected at the measuring point 8, at least that which is illustrated as illustrated. In particular, a detection of the network impedance at the respective grid connection point is proposed. However, these details are not shown in FIG. 3 and a measurement of the network impedance or detection of the network impedance would respectively relate to the grid connection point or in particular be made there. Insofar, the wind farm WP1 feeds via the grid connection point 12 into the electrical supply network 1, which may locally correspond to the measuring point 8. The second wind farm WP2 feeds into the supply network 1 via the grid connection point 14.

Via communication links 16, the control device 10 communicates with the first and second wind farms WP1 and WP2. Thereby, the control device can obtain information from the respective wind farm and judge whether a start in the black start mode can now be appropriate. Such information is, in particular, how much power and / or reactive power the respective wind farm could currently provide and thus feed. The information about the electrical supply network, in particular the respective network impedance related to the grid connection point 12 or 14, the control device 10 could also receive from the respective wind farm WP1 or WP2. In principle, the measuring point 8 can also be omitted if all information is provided by the relevant wind farm.

This information, that is, in particular information about the network status as well as the current state and the current performance of the two wind farms WP1 and WP2, are now evaluated in the control device 10 and the control device 10 can then give a start signal to the two wind farms WP1 and WP2 to let them start in black start mode.

The two wind farms WP1 and WP2 can then feed in particular first reactive power, partly or later but also active power. In this case, the two wind farms WP1 and WP2 are performed by the control device 10 with respect to a particular frequency and phase so that they feed with a fixed frequency, in particular the nominal frequency of the electrical supply network, and thus pretend this in the electrical supply network. The two wind farms WP1 and WP2 are synchronized with each other. Of course, it also comes into consideration that, in another embodiment, only feeds a wind farm and alone dictates the frequency. Thus, the wind farm or wind farms are not geared to an existing frequency in the grid, but instead provide it.

At the same time, the two wind farms WP1 and WP2 can be managed in such a way that they in particular start up the grid voltage.

The control device 10 can also undertake to connect consumers to the electrical supply network 1 as soon as the electrical supply network has a corresponding stability. This may include closing the switches S6 and S7 shown as examples at suitable times and thus switching on the corresponding consumers, namely the industrial consumers 4 or the city network 6. However, this connection from the control device 10 to the corresponding switches S6 and S7 is not shown for the sake of clarity. The diagram in FIG. 4 now illustrates by way of example how such a startup of the electrical supply network can take place with the aid of the two wind farms WP1 and WP2. The diagram shows the voltage U in the supply network 1 according to FIG. 3, z. At the measuring point 8, as a function of time, and it shows the power factor coscp of the two wind farms WP1 and WP2 in total.

At the time t ₀ , the control device 10 has determined that the electrical supply network is not in operation and determined that a start of the at least one wind farm, in this case the wind farms WP1 and WP2, makes sense. At the time t ₀ , a start signal for starting the two wind farms in a black start mode is thus given by a signal generator of the control device 10 to these two wind farms WP1 and WP2. These two wind farms now enter this black start mode to start and tune into a black start mode. This includes, for example, not being fed immediately with nominal voltage or a similar voltage value.

Accordingly, the voltage U is slowly increased from the time t ₀ with the value 0 on to nominal voltage U _N. At time t ₀ , the abbreviation SSM also indicates that the black start mode is used here.

At the time t-ι then the rated voltage U _{N could be} achieved, which is about mains frequency.

Here, the two wind farms WP1 and WP2 essentially feed in reactive power, especially as no significant consumers have yet been connected. Accordingly, the coscp has a low value close to 0. Thus, a lot of reactive power, but little active power is fed.

At the time t ₂ it is then determined that the voltage U could be maintained at the nominal voltage U _N and now a first stable operation is present. In this case, the industrial load 4 will now be switched on by way of example, in particular in that the switch S6 according to FIG. 3 is closed.

The voltage keeps its value of the nominal voltage U _N , which is to be expected regularly with certain fluctuations, which are not shown here for the sake of simplicity.

In addition, now more active power is fed, so that increases the coscp. Nevertheless, a not very high coscp is still drawn here to indicate that a significant proportion of reactive power is still being fed in. It should also be noted that an industrial consumer regularly requires some reactive power.

Now works the supply network 1 stable with switched on industrial consumers 4, the city network 6 can be switched on at time t ₃ by the switch S7 is closed. Of course, these processes are carried out with coordination in consultation with the consumers concerned, ie with the industrial consumer 4 or an operator of the city network 6, such as with the relevant municipal utilities.

With the connection of city network 6, even more active power is fed in and the reactive power can be slowly reduced.

It can then be assumed at time t ₄ that the supply network with switched on industrial consumer 4 and switched urban network 6 works stably and then also the large power plant 2, and other such power plants, could be switched on. At time t ₄ is therefore proposed to close the switch S1, but only after the large power plant 2 is raised accordingly. Depending on the circumstances, in particular depending on the type of large power plant 2 and depending on whether this has been shut down, or substantially still is in a standby-like mode, the time t ₄ , in which the example of large power plant 2 is switched, are much later than indicated in Fig. 4. In particular, the distances between t- ₁ and t ₂ or t ₂ and t _{3 could} on the one hand be significantly less than the distance between t ₃ and t ₄ .

In any case, the operation of t ₀ , when the wind farms start in the black start mode until the time U, when finally the large power plant 2 is switched on, can be regarded as a black start operation. With this last connection of the large power plant 2, all switches illustrated in FIG. 3, in particular the switches S1, S6 and S7, are finally closed and the electrical supply network 1 is then essentially in a normal state and the black start operation can then be ended or at least considered to be finished. This may mean that the control device 10 withdraws from the guidance of the two wind farms in the black start mode and then basically feed the wind farms normally into the electrical supply network 1.

Claims

claims 1. A method for feeding electrical power into an electrical supply network (1) by means of at least one in each case via a network connection point (12) to the supply network connected wind farm (WP1), wherein  - The supply network (1) is to operate at a mains frequency and  - each wind farm (WP1) has several wind turbines (100), comprising the steps  - determining whether the electrical supply network (1) is in operation,  - Starting the at least one wind farm (WP1) in a black start mode for generating electrical power for feeding into the supply network (1) when the supply network (1) is not in operation,  - Operating the at least one wind farm (WP1) in a black start operation in which electrical power is fed into the supply network (1) and thereby the supply network (1) is operated,  - In the black start mode and / or in the black start mode, the mains frequency is specified by the supply of electrical power. 2. The method according to claim 1, characterized in that  in the black start mode, the wind farm (WP1) is connected to the supply network (1) via the respective grid connection point (12), wherein  - The supply network (1) is not in operation before connecting, in particular has no network frequency and  - The supply network (1) after connecting the mains frequency by feeding through the at least one wind farm (WP1). 3. The method according to claim 1 or 2, characterized in that  in black start mode, a frequency generator is a frequency signal and optional on Generates phase signal and the at least one wind farm (WP1) as a pilot signal available and sets the at least one wind farm (WP1) frequency and possibly phase based on this control signal. 4. The method according to any one of the preceding claims, characterized in that one of the wind turbines (100) for specifying the frequency and optionally for specifying the phase works as a master system and the other wind turbines adapt to it, in particular synchronize with it and / or that when using multiple wind farms (WP1) a wind farm (WP1 ) for the specification of and optionally for the specification of the phase as Masterpark works and the other wind farms (WP1) adapt to it, in particular synchronize with it. 5. The method according to any one of the preceding claims, characterized in that  for starting the at least one wind farm (WP1) electrical energy is used from an energy storage and that optionally is used for feeding at least a portion of the electrical power energy from the energy storage. 6. The method according to any one of the preceding claims, characterized in that  before starting the at least one wind farm (WP1) at at least one of the respective grid connection points (12) a network impedance is detected to check an operability of the supply network (1) and / or adapt to the start in the black start mode and / or possibly the Wind farm (WP1) not to start, if it follows from the detected grid impedance that a serviceability of the supply network (1) is not given. 7. The method according to any one of the preceding claims, characterized in that  during or immediately after starting the at least one wind farm (WP1) in the black start mode, at least one load connected to the supply network (1) is switched on to serve as a load for the power fed into the supply network (1), so that in the supply network ( 1) an electric current can flow to this at least one consumer. 8. The method according to any one of the preceding claims, characterized in that  the start in the black start mode is triggered by an external signal of a Operator of the supply network (1) or a central control unit (10). 9. The method according to any one of the preceding claims, characterized in that before starting in the black start mode, a subnetwork (N1) of the supply network connected to the network connection point (12) is disconnected in order to be started and operated independently of the remaining part of the supply network (1) and optionally in a further step, the separated and operated in the black start operation subnet (N1) with the remaining part of the supply network (1), or a part thereof, synchronized and then reconnected. 10. The method according to any one of the preceding claims, characterized in that  the supply network (1) has at least one consumer and one conventional generating unit (2), wherein the conventional generating unit (2) has a rated power of more than 200 MW and / or at least one synchronous generator directly coupled to the supply network (1), wherein the conventional generating unit (2) is disconnected from the supply network (1) when the supply network (1) is not in operation. 1 1. A method according to any one of the preceding claims, characterized in that  at least two wind farms (WP1, WP2) are provided and these at least two wind farms (WP1, WP2) are started synchronously, in particular start up synchronously, wherein they are tuned to each other at least in their frequency and phase relationship, preferably one of the wind farms (WP1) works as Masterpark and the other park (WP2) resp. the other parks (WP2) are oriented towards the Masterpark (WP1). 12. The method according to any one of the preceding claims, characterized in that  - several wind farms (WP1, WP2) are used,  - The wind farms (WP1, WP2) exchange data with each other to prepare for a common start in the black start mode, wherein  - the wind farms (WP1, WP2) exchange at least data about their available power and / or power needed in the supply network (1) and  - depending on the start in the black start mode with subsequent operation in the black start mode control and / or derive from whether a start in the black start mode with subsequent operation in the black start mode is possible. 13. The method according to any one of the preceding claims, characterized in that for a determination of available power of the relevant park (WP1)  - the prevailing wind, - expected wind and / or - Properties and size in the park (WP1) of existing storage facilities taken into account. 14. Control device (10) for controlling the feeding of electrical power into an electrical supply network (1) by means of at least one in each case via a network connection point (12) to the supply network (1) connected wind farm (WP1), wherein  - The supply network (1) is to operate at a mains frequency and  - each wind farm (WP1) has several wind turbines (100), and the control device (100)  a detection means for determining whether the electrical supply network is in operation,  a signal generator for generating and transmitting a start signal for starting the at least one wind farm (WP1) in a black start mode for generating electrical power for feeding into the supply network (1) when the supply network (1) is not in operation,  - Guiding unit for guiding the at least one wind farm (WP1) in a black start operation in which electrical power is fed into the supply network (1) and thereby the supply network (1) is operated,  - In the black start mode and / or in the black start mode, the grid frequency by the supply of electrical power through the at least one wind farm (WP1) is specified. 15. Control device (10) according to claim 14, prepared to  to carry out a method according to one of claims 1 to 13, and / or - at least one wind farm (WP1) to guide so that in accordance with a method according to one of claims 1 to 13 electric power into the electrical supply network (1) feeds. 16. Wind farm (WP1) with several wind turbines (100), whereby the wind farm (WP1)  is prepared to carry out a method according to one of claims 1 to 13 or to participate in such a method,  - Has a control device (10) according to claim 14 or 15 and / or - is prepared, with a control device (10) according to claim 14 or 15 to be functionally coupled, in particular to receive the start signal and / or to be guided by the guide unit in the black start mode. 17. Wind turbine (100) prepared for operation in a wind farm (WP1) according to claim 16, and / or comprising a control device (10) according to claim 14 or 15.