FEED-IN METHOD FOR A WIND POWER SYSTEM, AND WIND POWER SYSTEM

Abstract

A method for feeding in electrical power, using a wind power system including a wind farm, into a grid at a grid connection point is provided. The grid has a distribution grid and a further higher portion of the grid lying hierarchically above the distribution grid. The grid connection point is connected to the distribution grid. The method includes detecting an initial feed-in limitation with respect to the grid connection point. The method includes checking whether the farm power that can be generated from wind by the wind farm is limited by the initial feed-in limitation so that the wind farm is throttled in its power output by the initial power limit. The method includes evaluating whether the initial power limit can be increased by a redistribution of the limitation, increasing the initial power limit to an increased power limit and feeding in electrical power above the initial power limit.

Claims

1. A method for feeding in electrical power using a wind power system into an electrical supply grid at a grid connection point, the method comprising: detecting a first feed-in limitation associated with the grid connection point, the first feed-in limitation representing an initial power limit, the wind power system being permitted to feed the electrical power into the electrical supply grid up to the initial power limit, wherein: the wind power system includes at least one wind farm, the electrical supply grid has at least one distribution grid and at least one higher grid portion that is hierarchically above the at least one distribution grid, and the at least one distribution grid is subordinate to the at least one higher grid portion, and the grid connection point is connected to the at least one distribution grid, determining whether farm power that is capable of being generated from wind by the wind farm is greater than the initial power limit such that the wind farm is throttled to a power below the initial power; in response to determining that the wind farm is throttled, determining whether the initial power limit is capable of being increased by at least redistributing the first feed-in limitation; in response to determining that the initial power limit is capable of being increased, increasing the initial power limit to an increased power limit; and in response to increasing the initial power limit to the increased power limit, feeding in the electrical power above the initial power limit.

2. The method as claimed in claim 1, wherein determining whether the first feed-in limitation is redistributable includes determining whether at least one criterion is satisfied from a list of criteria including: the first feed-in limitation is not prescribed by the at least one distribution grid; the first feed-in limitation is prescribed by the at least one higher grid portion; a portion of the electrical supply grid that is not overloaded is detected; no physical limitation of the grid connection point exists, the first feed-in limitation is associated with penalty costs for exceeding the first feed-in limitation; the first feed-in limitation is one of a plurality of feed-in limitations of the at least one distribution grid that are set such that a sum of the plurality of feed-in limitations is below a limitation for the sum of the plurality of feed-in limitations, and the first feed-in limitation is permitted to be increased on a condition that the sum of the plurality feed-in limitations remains the limitation for the sum of the plurality feed-in limitations; at least one further power generator that feeds into the same distribution grid is associated with a second feed-in limitation and the at least one further power generator is not fully utilizing the second feed-in limitation, and a power level by which the at least one further power generator lies below the second feed-in limitation is offered as a tradable capacity to wind power systems fully or partially; and the first feed-in limitation is caused by the at least one higher grid portion and a neighboring distribution grid is capable of taking up power for exceeding the first feed-in limitation.

3. The method as claimed in claim 1, comprising: specifying the increased power limit as a time-based progression; and/or determining a feed-in forecast that provide time-based progression of power to be fed in for a forecast time period.

4. The method as claimed in claim 1, comprising: supplying controllable loads within the wind farm by electrical power, generated by the wind farm from wind, that is not fed in the electrical supply grid in response to reaching the first feed-in limitation.

5. The method as claimed in claim 1, wherein the first feed-in limitation is associated with penalty costs for exceeding the first feed-in limitation.

6. The method as claimed in claim 14, comprising: controlling the feeding in of the electrical power based on a maximum limit that is above the initial power limit, wherein the maximum limit is not to be exceeded.

7. The method as claimed in claim 1, comprising: determining whether the first feed-in limitation is currently applicable or applicable for a future time period.

8. The method as claimed in claim 1, wherein for feeding in the electrical power above the initial power limit, power exceeding the initial power limit is fed at least to a consumer connected in the distribution grid.

9. The method as claimed in claim 1, wherein: for feeding in electrical power above the initial power limit, tradable capacities of other power generators of the at least one distribution grid are used.

10. The method as claimed in claim 1, wherein the wind power system includes: a photovoltaic installation; or batteries configured to store at least an amount of energy equivalent to ten minutes of a rated power of the wind farm.

11. A wind power system for feeding electrical power into an electrical supply grid, at a grid connection point, comprising: at least one wind farm, the electrical supply grid having at least one distribution grid and at least one higher grid portion that is hierarchically above the at least one distribution grid, the at least one distribution grid being subordinate to the at least one higher grid portion, and the grid connection point being connected to the at least one distribution grid; and a central farm computer configured to: detect a first feed-in limitation associated with the grid connection point, the first feed-in limitation representing an initial power limit, the wind power system being permitted to feed electrical power into the electrical supply grid up to the initial power limit; determine whether farm power that is capable of being generated from wind by the wind farm is greater than the initial power limit such that the wind farm is throttled to a power below the initial power limit; in response to determining that the wind farm is throttled, determine whether the initial power limit is capable of being increased by at least redistributing the first feed-in limitation; in response to determining that the initial power limit is capable of being increased, increase the initial power limit to an increased power limit; and in response to increasing the initial power limit to the increased power limit, feeding in electrical power above the initial power limit.

12. (canceled)

13. The method as claimed in claim 5, comprising determining a level by which the power fed in exceeds the initial power limit.

14. The method as claimed in claim 13, wherein the initial power limit is determined by: setting a penalty cost function, for the penalty costs, based on the level by which the power fed in exceeds the initial power limit; setting a tariff function for a feed-in tariff based on the level by which the power fed in exceeds the initial power limit; and controlling the level by which the power fed in exceeds the initial power limit based on comparing the penalty cost function and the tariff function.

15. The method as claimed in claim 7, wherein determining whether the first feed-in limitation is currently applicable or applicable for the future time period is performed when detecting the first feed-in limitation and/or determining whether the farm power is greater than the initial power limit.

16. The method as claimed in claim 9, wherein the tradable capacities of photovoltaic installations, batteries and/or further wind farms that are connected to the at least one distribution grid.

17. The method as claimed in claim 10, wherein the wind farm and the photovoltaic installation are respectively associated with a rated power and a sum of rated powers of the wind farm and the photovoltaic installation form a total rated power, the grid connection point is limited in a fixed manner to a fixed power value below the total rated power and above a largest rated power of the rated powers.

18. The method as claimed in claim 17, wherein the grid connection point is dynamically limited to a dynamic power value below the largest rated power.

19. The method as claimed in claim 10, wherein the wind farm, the photovoltaic installation and the electrical store are respectively characterized by a rated power and a sum of rated powers of the wind farm, the photovoltaic installation and the electrical store form a total rated power, the grid connection point is limited in a fixed manner to a fixed power value below the total rated power and above a largest of the rated powers.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0079] The invention is explained in more detail below by way of example on the basis of embodiments with reference to the accompanying figures.

[0080] FIG. 1 shows a wind power installation in a perspective representation.

[0081] FIG. 2 shows a wind farm in a schematic representation.

[0082] FIG. 3 schematically shows a wind power system together with part of an electrical supply grid with further generators and consumers.

DETAILED DESCRIPTION

[0083] FIG. 1 shows a wind power installation 100 with a tower 102 and a nacelle 104. Arranged on the nacelle 104 is a rotor 106 with three rotor blades 108 and a spinner 110. During operation, the rotor 106 is set in a rotary motion by the wind, and thereby drives a generator in the nacelle 104.

[0084] FIG. 2 shows a wind farm 112 with, by way of example, three wind power installations 100, which may be the same or different. The three wind power installations 100 are consequently representative of essentially any number of wind power installations of a wind farm 112. The wind power installations 100 provide their power, to be specific in particular the electricity generated, by way of an electrical farm grid 114. In this case, the electricity or power respectively generated by the individual wind power installations 100 is added together and there is usually a transformer 116, which steps up the voltage in the farm in order then to feed into the supply grid 120 at the feed-in point 118, which is also referred to generally as the PCC. FIG. 2 is just a simplified representation of a wind farm 112, which for example does not show any controller, although there is of course a controller. It is also possible for example for the farm grid 114 to be differently designed, in that for example there is also a transformer at the output of each wind power installation 100, to name just one other exemplary embodiment.

[0085] FIG. 3 schematically shows a wind power system 300, specifically essentially in the left half of FIG. 3, and part of an electrical supply grid 302, specifically essentially in the right half of FIG. 3. The wind power system 300 is here by way of example a wind farm 304, which is symbolized by way of example by three wind power installations, also a photovoltaic installation 306 and an electrical store (e.g., battery) 308. Also provided is a central farm computer 310, which can activate the wind farm 304, but also the other elements of the wind power system 300, specifically particularly also the photovoltaic installation 306 and the electrical store 308.

[0086] The central farm computer 310 has for this a detecting unit 311, a checking unit 312, an evaluating unit 313 and a changing unit 314. These four units may be respectively provided as a microprocessor and are therefore referred to as μ.sub.1, μ.sub.2, μ.sub.3 and μ.sub.4. The central farm computer 310 can activate the wind farm 304, the photovoltaic installation 306 and the electrical store 308, which may be formed as a battery store, and also receive information from there, which is respectively indicated by a double-headed arrow.

[0087] The communication of the central farm computer 310 with the wind farm 304 may particularly also take place individually with corresponding feeding-in devices (e.g., inverters) 316. Each of the wind power installations may have such a feeding-in device 316, which can particularly generate an electrical three-phase alternating current that can be fed in. This is indicated by the symbol of a semiconductor circuit. FIG. 3 only clearly shows such a feeding-in device 316 for one of the three symbolically represented wind power installations, and for the others such a feeding-in device 316 is only indicated. Particularly, the changing unit 314 may be connected to the feeding-in devices 316, in order to transmit to them a signal for changing the electrical power to be fed in.

[0088] The wind power installation of the wind farm 304 and also the photovoltaic installation 306 and possibly the electrical store 308 feed into a first distribution grid 324 at a grid connection point 332 via a farm disconnecting switch 318 and a farm transformer 320. They then also feed into the electrical supply grid 302, of which the first distribution grid 324 is part.

[0089] The central farm computer 310 also communicates with an external control center 326, which can be operated particularly by a grid operator responsible for the electrical supply grid 302 or part of it. Here, too, information can be exchanged in both directions. In particular, the receiving unit (e.g., receiver or transceiver) 311 may communicate with the external control center 326 and also obtain an initial feed-in limitation from there as information. Furthermore, the central farm computer 310, in particular the receiving unit 311, may also obtain information on the origin or cause of such an initial feed-in limitation. Such an initial feed-in limitation is in this case given with respect to the grid connection point 322.

[0090] The external control center (e.g., controller) 326 may in this case also transmit further initial feed-in limitations to other feeders, in particular to a symbolically represented second photovoltaic installation 328. The second photovoltaic installation 328 is not part of the wind power system 300, but feeds in independently, and therefore may also have an independent switch. The second photovoltaic installation 328 could also feed into the electrical supply grid 302 via a transformer, which for the sake of simplicity is not shown here.

[0091] Many switches, similar to the farm switch 318, are in any case symbolically depicted in the electrical supply grid 302 of FIG. 3, particularly intended to illustrate that there is the possibility of disconnection at various points. The grid operator may possibly also activate such switches from its external control center 326, and enquire their position, which is respectively indicated by corresponding double-headed arrows. Simply for the purpose of allowing them to be seen better, all of the switches similar to the farm switch 318 are shown in FIG. 3 as open. The normal operating case is that all of these switches are closed.

[0092] Apart from the first distribution grid 324, a second distribution grid 330 and a third distribution grid 332 are shown. These three distribution grids 324, 330 and 332 may have the same hierarchical level and, in particular, also the same voltage level, even though that is not an absolute requirement.

[0093] Also depicted is a higher portion of the grid 334, lying above the first distribution grid 324 and consequently also above the second and third distribution grids 330 and 332. This higher portion of the grid 334 is in this case connected inter alia via a high-voltage transformer 336 and a grid disconnecting switch 338 to the first distribution grid 324.

[0094] Also symbolically shown is a settlement (populated area) 340, which is connected to the second distribution grid 330. Furthermore, a factory 342 is connected as an industrial consumer to the third distribution grid 332. For illustrative purposes, a conventional power plant 344 is also connected to the third distribution grid 332 via a high-voltage transformer 346. This representation may however also illustrate a situation in which the conventional power plant 344 is connected to a portion of the grid of a higher order. Particularly, the power plant may for example also be connected directly to the higher portion of the grid 334.

[0095] In principle, the distribution grids 324, 330 and 332, the higher portion of the grid 334, the consumers 340 and 342 and also the feeders 328 and 344 that are shown can be seen as part of the electrical supply grid, in any event from the viewpoint of the wind power system 300. From another viewpoint, the wind power system 300 itself could be understood as part of the electrical supply grid.

[0096] On the basis of this schematic representation of a setup of an electrical supply grid 302 with the wind power system 300, at least part of the idea can be explained. If the central farm computer 310, particularly the receiving unit 311, receives an initial feed-in limitation from the control center 326, this can initially be established by the detecting unit 311. This information may be passed on to the checking unit 312. The checking unit can then check on this basis whether the farm power that can be generated from wind by the wind farm is limited by this initial feed-in limitation. In other words, the checking unit 312 can particularly check whether there is sufficient wind in the first place for such an initial feed-in limitation to have any influence at all on the current feeding-in state of the wind farm.

[0097] If it has been found that the initial feed-in limitation is relevant for the wind farm, the evaluating unit 313 can then evaluate whether nevertheless this initial power limitation can possibly be increased. If this is the case, the changing unit 314 can possibly increase the initial power limit that has been prescribed by the initial feed-in limitation, and thereby also correspondingly determine a value of the increase or a new value after the increase for the power to be fed in. It can then pass the result to the feeding-in devices 316, so that the wind power installations of the wind farm 304 can behave correspondingly. Otherwise, the wind power installations may also have been informed in this way of the previously prescribed, and then possibly initially also implemented, initial feed-in limitation.

[0098] Various redistributions of the limitation come into consideration, some of which are now to be explained by way of example on the basis of the illustrated setup of FIG. 3.

[0099] A variant that also serves well for purposes of illustration is that the grid operator, represented by its control center 326, desires a power limitation for the transmission of power into the higher portion of the grid 334. The higher portion of the grid 334 is otherwise shown in FIG. 3 for purposes of illustration with a further disconnecting sub-line 350, which is intended to indicate that the higher portion of the grid 334 may also be part of a transmission grid, or leads to a transmission grid. This desired limitation, given by way of example, may particularly also come into consideration for reasons of protecting or controlling such a transmission grid, specifically a limitation of the power which, to be clear, is intended to be transmitted via the high-voltage transformer 336. The grid disconnecting switch 338 is of course closed in this case.

[0100] This limitation may therefore have been distributed uniformly among the feeders, particularly among the regenerative feeders, specifically the wind power system 300 and the second photovoltaic installation 328.

[0101] For the wind power system 300, it has been found that this initial feed-in limitation actually limits the feeding in; here specifically the wind farm 304 must or should reduce its generated power. The reason for this may be, to be clear, inclement fall weather with strong wind and little sunshine. In this case, however, the second photovoltaic installation 328, which may for example be greater with regard to its rated power than the photovoltaic installation 306 of the wind power system 300, lies far below the feed-in limitation prescribed for it. If the wind power system 300 knows that, specifically because the evaluating unit 313 particularly has evaluated it, the wind power system 300 can correspondingly feed in more power than the initial feed-in limitation prescribed for it has dictated. This is so because the power limitation actually provided for the high-voltage transformer 336 is then nevertheless observed.

[0102] Otherwise, this example that has been given also comes into consideration whenever, unlike the situation illustrated in FIG. 3, the second photovoltaic installation 328 is not connected to the second distribution grid 330, but to the same distribution grid 324.

[0103] Also coming into consideration as a further variant, which may also be combined with those mentioned above, is that it is known that the symbolically represented factory 342, that is to say a large consumer, needs a very large amount of power, or even has announced an increased power requirement. Such information may be provided for example by the factory 342 or some other large consumer to the external control center 326. The latter can pass on this information to the central farm computer 310, so that this information finally also arrives at the evaluating unit 313.

[0104] If, therefore, this high or even increased power requirement of the factory 324 is known, there is likewise the possibility that the wind power system 300 exceeds the actually prescribed initial feed-in limitation. This increased power then flows however, at least partially, directly to the large consumer, that is to say here to the factory 342, without this power having to pass the high-voltage transformer 336. To this extent, this also constitutes a redistribution, because the initial feed-in limitation, which has its cause in the higher portion of the grid 334, can be distributed differently, in that the excess power is as it were made to bypass the problem point. Also to this extent, the high-voltage transformer 336 is mentioned for reasons of better illustration, without it actually having to be the problem. This high-voltage transformer 336 may to this extent be understood as the transmission point to the higher portion of the grid 334.

[0105] Other redistributions of the limitation also come into consideration, specifically using quite generally the two further distribution grids, that is to say the second distribution grid 330 and the third distribution grid 332. It may also come into consideration here that each of these distribution grids is for its part connected via another connection point to the higher portion of the grid 334 and in this way the power flows can consequently be changed.

[0106] To this extent, the redistribution of the limitation, which applies to any embodiments, may also be referred to synonymously as a redistribution of the power.

[0107] A further variant of the redistribution of the limitation or redistribution of the power may be that a power limitation is controlled by way of a cost function. For example, a power limitation which is defined such that exceeding this power limitation leads to a cost levy or to a reduction of the feed-in tariff may be prescribed. The wind power system 300 shown may in this case then check whether it is advisable to exceed the initial feed-in limitation and as a result to accept a reduction of the tariffs, or instead to feed power into the electrical store 308, particularly if the limitation is for a limited time. As a result, the control of the wind power system can be indirectly performed from outside.

[0108] It also comes into consideration however that such technically effective controls over costs or tariffs may have different effects for the sum of all those involved, that is to say particularly the feeders and consumers, resulting altogether in stable control. Particularly, prescribing costs for exceeding the initial feed-in limitation may be accompanied by reducing costs for consumers that take power, as is the case for example with so-called off-peak electricity, with which even end consumers such as small households can be supplied with power at more favorable rates at night time than during the day. If therefore the wind power system exceeds the initial feed-in limitation, with the result that the tariff is reduced, in return the households of the settlement 340 for example can be supplied with electricity at more favorable rates, and this offer is then also taken up. Other feeders, such as the conventional power plant 344 shown by way of example, can save primary energy by feeding in less, which is not the case in principle with a wind farm system, unless the wind power system has an electrical store. Correspondingly, it makes more sense for a conventional power plant to comply with a power limitation.

[0109] All of this can have the overall effect that altogether a desired power balance is obtained, because for example, although the wind farm feeds in more power, a conventional feeder feeds in less and a consumer then to some extent consumes more power.

[0110] It has consequently been recognized that it can be assumed that in future a calculation of the use of the grid that is dependent on full grid utilization and grid capacity may be advisable in distribution and transmission grids. Then a variable assessment of the grid connection power particularly comes into consideration, and similarly a dynamic restriction.

[0111] Consequently proposed is a solution for controlling a wind power installation, a wind farm and/or a wind power system in a way corresponding to these boundary conditions.

[0112] Particularly proposed for this are wind farms with a variable grid connection power. This also allows a variable grid charge to be taken into account.

[0113] An increase in the yield of the installations or avoidance of losses of yield can be realized.

[0114] For this purpose, it is taken into account that, in probably the simplest case, in future there may be a simple, temporary and/or dynamic limitation of the grid connection capacity, specifically to a dynamic connection value as an alternative or in addition to feed-in management. It is then also possible consequently to respond to this dynamic connection value by simply restricting the farm power.

[0115] It is however proposed, particularly for income-optimized operation, to check for example at farm level whether the limitation results from the distribution grid or is because of a restriction from the higher levels of the grid.

[0116] It is also proposed to check whether the limitation concerns the current feeding in or future feeding in and whether possible losses of yield may occur.

[0117] If the limitation originates from the higher levels of the grid and cutting back is threatened, there is the chance of secondary marketing of the volumes of electricity in the distribution grid, whereby cutting back can then nevertheless be avoided.

[0118] If there is no possibility of secondary marketing, under some circumstances there is the possibility of also at least partially using temporarily grid connection capacity of other feeders in the vicinity, for example of photovoltaic installations or wind farms with still available grid connection power, or else of wind farms that are currently undergoing maintenance.

[0119] Coming into consideration as a further possibility that can also be added is to use loads within the farm instead of lowering the power generated.

[0120] Only when there is no possibility of increasing the grid connection capacity must the wind farm or the wind power system be cut back.

[0121] It has been recognized that the proposed solutions can additionally also have commercial advantages.

[0122] If specifically for example the dynamic grid connection power not only comprises a fixed limit but is coupled to a price, in a further embodiment the wind power installation or the wind system may carry out a simple cost appraisal. In this case it may be checked, particularly additionally, whether on a price basis the expected feeding in justifies an increase of the grid connection capacity. Here, too, it should be checked whether under some circumstances unused grid connection capacities of neighboring regenerative feeders can be used.

[0123] A further application area for regenerative feeders with a variable grid connection power are combined systems of wind power installations, photovoltaic installations and stores. These can together form a wind power system. For example, the grid connection power of such a wind power system may be limited to 80% of the power of the wind power installations and have for example a 30-percent dynamic component. Consequently, the grid connection power would be variably restricted to a value of 80% to 110% of the rated power of the wind farm of such a wind power system.

[0124] It has however been recognized in this respect that the wind power installations on the one hand and the photovoltaic installations on the other hand usually generate large amounts of power at different times, so that the restriction to a value just a little above the rated value of the wind farm alone may be sufficient. Often, even that value is not reached, which can be taken into account by the dynamic component given by way of example of 30%.