METHOD FOR CONTROLLING A WIND TURBINE

Description

[0001] The present invention relates to a method for controlling at least one wind turbine. The present invention also relates to a corresponding wind turbine and to a wind farm comprising a plurality of such wind turbines. The present invention also relates to a wind energy system comprising at least one wind farm and at least one solar power system.

[0002] Wind turbines are well known and are fundamentally designed to extract energy from the wind and feed it into the electrical grid as electricity. In addition to this basic function, wind turbines are also increasingly performing tasks to support the electrical grid.

[0003] This increasing importance of grid support is partly due to the increasing share of decentralized energy suppliers, which include not only wind turbines but also photovoltaic systems in particular. Therefore, it is desirable that decentralized energy suppliers can also contribute to supporting the grid, or at least that some of these decentralized suppliers can make such a contribution.

[0004] A frequently cited problem with supporting the electrical grid using wind turbines is that their ability to supply additional power to support the grid depends on the current weather conditions. In other words, one problem is that wind turbines can supply little or no additional power when there is little or no wind.

[0005] In fact, a similar problem is also mentioned for photovoltaic systems, which can naturally only generate electricity during the day, especially when the sun is shining.

[0006] Wind turbines fundamentally have the potential to store kinetic energy, particularly in their rotors, in order to be able to provide instantaneous reserves, for example. However, even such a provision of positive instantaneous reserves from the aforementioned kinetic energy will only be possible if the rotor of the wind turbine in question is also rotating. When the rotor of the wind turbine is rotating, it is then possible to provide instantaneous reserves, i.e., to increase the power fed into the grid in the short term. Such feed-in of instantaneous reserves is not known for photovoltaic systems, however. It could at best be achieved through precautionary curtailment or the provision of an energy storage system.

[0007] The German Patent and Trademark Office has searched the following prior art in the priority application for the present application: DE 10 2011 081 795 A1, DE 10 2013 101 099 A1, DE 10 2013 203 540 A1, DE 10 2014 101 809 A1, US 2011 / 0057445 A1, US 2016 / 0065115 A1, WO 2014 / 118059 A1, DE 10 2009 037 239 A1 and DE 297 15 248 U1.

[0008] The present invention is therefore based on the object of addressing at least one of the above-mentioned problems. In particular, the invention is based on the object of improving the grid integration of renewable energies. Where possible, instantaneous reserve provision should be realized at any time in the grid. In particular, the highest possible coverage ratio for electricity generation from renewable energy sources should be achieved or at least enabled. In particular, a grid-technical upper limit on the expansion of renewable energy sources due to a lack of grid support should be avoided. At the very least, an alternative solution to previous solutions should be proposed.

[0009] According to the invention, a method according to claim 1 is proposed. The method thus relates to the control of at least one wind turbine for generating electrical energy from wind for feeding into an electrical grid. The method for controlling a wind turbine is analogously transferable to the control of multiple wind turbines. In particular, each wind turbine preferably controls its operating point independently, but can receive specifications for coordination, which can be coordinated and provided, in particular, by a higher-level control unit, such as a wind farm controller for controlling a wind farm.

[0010] The wind turbine features an aerodynamic rotor with adjustable blade pitch. In principle, a single rotor blade could be sufficient, but this has proven to be fundamentally unsuitable today. Furthermore, the rotor can be operated at a variable rotor speed. Particularly in the partial load range, when the wind speed has not yet reached the nominal wind speed, the rotor speed can depend on the selected operating point. However, the rotor speed is generally variable and preset within reasonable limits.

[0011] A generator is coupled to the aerodynamic rotor, which produces generator power.

[0012] It is proposed that the wind turbine be operated in a normal mode, in which it feeds available wind power up to a rated power into the electrical grid. As long as the wind is so weak that it cannot deliver rated power, the available wind power, and thus as much power as possible, is harvested from the wind in this normal mode and fed into the electrical grid. If the wind speed reaches or exceeds the rated wind speed, the power must be limited to the rated power to protect the wind turbine components. This normal mode is usually also assigned an operating point that depends on the wind speed.

[0013] It is also proposed that the wind turbine switch from normal mode to support mode depending on the operating situation of at least one solar system feeding into the same grid. The wind turbine can therefore also be operated in a support mode that differs from normal mode. It is proposed here that this support mode takes place depending on a solar system feeding into the same grid. This is particularly recommended for photovoltaic systems in which the power fed in fluctuates practically instantaneously with the incoming solar power and which usually have virtually no energy storage. Photovoltaic systems in particular therefore have the problem that they are not suitable for providing an instantaneous reserve. However, they can also support other solar systems.

[0014] Specifically, it is intended that the wind turbine in the backup mode feeds in, can feed in, or at least offers more instantaneous reserve than in its normal mode. However, it is also conceivable that in this backup mode the wind turbine otherwise makes a greater contribution to supporting the electrical grid than in normal mode.

[0015] In particular, it is proposed that this support mode be selected when the at least one photovoltaic system feeding into the same electrical supply network, which can also be referred to simply as the grid, feeds comparatively large amounts of electrical power into the grid, particularly when feeding in at its rated power. In other words, the support mode of the at least one wind turbine is proposed here when there is a high level of solar radiation.

[0016] The invention has recognized that there is regularly a correlation between high solar radiation, and thus a high level of solar power fed into the grid, on the one hand, and weak wind, and thus a low level of solar power fed into the grid, on the other. To this end, it is now proposed that, in such a case, the at least one wind turbine be provided to make a comparatively large contribution to supporting the electrical grid. In particular, in such a situation, a wind turbine can practically take over the provision or at least offering of instantaneous reserve for the at least one photovoltaic system feeding into the grid.

[0017] This makes it possible to feed in a large amount of photovoltaic power during strong solar radiation, while simultaneously providing a high level of backup potential, especially instantaneous reserve, that the photovoltaic solar systems themselves could not provide. This allows photovoltaic systems and wind turbines to complement each other advantageously, with the photovoltaic systems feeding in power and supporting the wind turbines during strong solar radiation.

[0018] In principle, however, at least one wind turbine can also switch to support mode if it can also feed in some or even a lot of wind power itself. While it has been recognized that there is a correlation between high solar radiation and low wind, the proposed solution can also be applied in the rare cases where there is high solar radiation and high wind simultaneously.

[0019] It is therefore preferably proposed that the wind turbine can provide more instantaneous reserve in the support mode than in the normal mode.

[0020] According to one embodiment, it is proposed that an instantaneous reserve power PM is fed into the electrical supply grid as a function of a frequency change df / dt of a grid frequency f detected in the electrical supply grid, wherein different dependencies of the instantaneous reserve power PM on the frequency change df / dt are provided between the normal mode and the support mode such that, for the same frequency change df / dt, the amount of the instantaneous reserve power PM is greater in support mode than in normal mode. An instantaneous reserve that is fed into the electrical supply grid as a function of the frequency change serves in particular to counteract frequency changes. Such counteraction should occur as quickly or immediately as possible. For this reason, the term instantaneous reserve power or, more simply, instantaneous reserve is also used, and this term instantaneous reserve is also used synonymously with instantaneous reserve power below.

[0021] Feeding in such an instantaneous reserve is suitable for supporting the electrical supply grid and is therefore desirable. However, it should be noted that feeding in such an instantaneous reserve can also place a strain on the wind turbine feeding in. In particular, a rapid increase in the fed-in power, especially if this increase approaches design limits, can place strain on the components. Furthermore, this can also result in performance losses because the wind turbine thereby departs from its optimal operating point, at least for a short time. In particular, the use of kinetic energy from the rotating rotor of the wind turbine causes this rotor to decelerate, which can, on the one hand, lead to the aerodynamically optimal operating point being departed from, but on the other hand, can also lead to mechanical stress on the turbine.

[0022] Feeding in an instantaneous reserve is therefore not necessarily desirable for the operator of the wind turbine.

[0023] It is therefore proposed that less instantaneous reserve be fed in or offered in normal mode than in backup mode. The feeding in of an instantaneous reserve regularly depends on the detection of a frequency change in the voltage of the electrical supply grid, namely the frequency change df / dt. It is now proposed that the response to a frequency change in normal mode be less than in backup mode. Accordingly, for a frequency change of the same magnitude, less instantaneous reserve is provided, i.e., fed in, in normal mode than in backup mode.

[0024] Preferably, the instantaneous reserve power PM can be calculated using the following formula: P M = k · df / dt

[0025] Here, k forms a dependency factor which is greater in magnitude in support mode than in normal mode. The dependency factor k thus determines the relationship between the instantaneous reserve power PM to be fed in and the frequency change df / dt and can be set to different values ​​for normal mode and support mode. Its magnitude is set to be larger for support mode. Since instantaneous reserve should be fed in for support when the frequency is reduced, i.e. when df / dt is negative, the dependency factor k will usually have a negative value. Instead of the dependency factor k, a function can be used, for example, or other criteria can be included, such as taking limit values ​​or initial values ​​into account. Boundary conditions can also be taken into account, for example that a limit value of an absolute frequency deviation must first be exceeded in terms of magnitude.Preferably, the dependency factor k is at least twice as large in the backup mode as in the normal mode. According to one embodiment, the dependency factor k is 0 in the normal mode, so that no instantaneous reserve is fed into the normal mode.

[0026] It is therefore also conceivable that normal mode and backup mode differ primarily in this different level of instantaneous reserve. It is also conceivable that the actual operating point does not differ between normal mode and backup mode. It is therefore conceivable that the wind turbine is fundamentally operated at its optimal operating point in both modes, as long as an instantaneous reserve is not called upon, i.e., as long as the frequency change df / dt is small enough, for example, or if the absolute frequency deviations from the normal grid frequency, especially the nominal frequency, only occur within a small, particularly negligible range.

[0027] According to one embodiment, it is proposed that a support power, in particular an instantaneous reserve power, is offered to support the electrical supply grid, which can be called up for feeding into the electrical supply grid or which can be fed in depending on a grid behavior, wherein the at least one wind turbine offers a higher support power in support mode than in normal mode. Here, too, it is taken into account that feeding in an instantaneous reserve to support the electrical supply grid is advantageous for the grid, but not necessarily advantageous for the operator of the wind turbine. It is therefore proposed that an instantaneous reserve is not offered in normal mode or is offered with a lower amplitude than in support mode.

[0028] Here, too, as with the different frequency change dependence described above, the underlying idea is that offering or feeding in a higher instantaneous reserve is particularly advantageous when the photovoltaic systems feeding into the same grid are feeding in high power. Here, too, it can be provided that at least one wind turbine is operated at the same operating point in both normal mode and support mode, as long as no instantaneous reserve or other support power is required. However, it is also possible, as explained below, for the wind turbine to be deliberately operated at a different operating point.

[0029] Preferably, according to one embodiment, the wind turbine in support mode feeds at least partially less power into the electrical supply grid than in normal mode, or that it draws power from the electrical supply grid in order to thereby provide an increased instantaneous reserve.

[0030] Such a measure can particularly increase the possible backup power, and in particular the possible instantaneous reserve. To do this, the wind turbine leaves its optimal operating point because the provision or at least offering of instantaneous reserve is then the focus. In particular, this can ensure that such a large instantaneous reserve or other backup power is provided or at least offered that it is sufficient for at least one photovoltaic system feeding into the same grid. By leaving an optimal operating point, less power is usually fed into the grid. However, it is also possible that another operating point is found at which no, or not significantly less, power is fed into the grid, but that switching to this new operating point temporarily means a reduction in power feed-in.This is especially true for a new operating point that has a higher speed, where accelerating to this higher speed results in a power loss for the rotor for the duration of the acceleration. It may still be possible to deliver a similar amount of power at this higher speed as at the optimal operating point, but perhaps with a greater turbine load or other disadvantages.

[0031] According to one embodiment, it is proposed that the support mode comprise a spin operation in which the rotor of the wind turbine rotates due to the wind drive, without generating power. Such a spin of the wind turbine can be provided in particular when there is only little wind. The wind turbine is then regularly not put into operation because the available wind energy is not sufficient to generate the power required to operate the wind turbine, so that ultimately no power can be fed in. Here, it is therefore proposed to deliberately allow this spin operation and not to switch the wind turbine off. The normal mode in this case would be to switch the turbine off, and the proposed support mode is that the turbine is switched on in this spin operation. The rotor of the wind turbine therefore rotates at least somewhat and can, if necessary,This also provides an instantaneous reserve if needed, at least for a short time.

[0032] According to a further variant, it is proposed that the support mode comprise high-speed operation, in which the wind turbine is operated at the highest possible speed without feeding in any power, or with only a small amount of power being fed in, namely less power than would be possible at the speed in normal mode. Here, too, the wind turbine changes its operating point from normal mode to support mode. The optimal speed at which maximum power can be generated is no longer set, but rather the highest possible speed is set. The highest possible speed is in this respect a speed that can be achieved due to the prevailing wind, whereby speed limits are of course taken into account. By setting this high, or at least increased, speed, an operating point with high kinetic energy, i.e. high rotational energy, is selected. This high rotational energy can then be used as an instantaneous reserve if required.This also makes it possible to provide a high instantaneous reserve, which can exceed the level that the wind turbine would normally provide or would have to provide given the wind conditions present at that time.

[0033] According to one embodiment, it is proposed that the support mode relates to zero-power operation, in which the speed is increased up to the maximum speed without any power being fed in. This partially corresponds to the previously described operation with the highest possible speed. However, here it is expressly proposed to bring the speed up to the maximum speed, i.e. in particular up to the nominal speed, and deliberately not to feed in any power. This also includes the case where the turbine is now operating at nominal speed and could still feed in power but does not. This case particularly applies to the situation in which there is sufficient wind to operate the wind turbine at this maximum speed. This means that, at least taking wind fluctuations into account, the speed may increase even further, although this is prevented by control technology in this case.In particular, the wind turbine is maintained at this maximum speed. For this purpose, a blade adjustment system is provided, in which the rotor blades are adjusted and continuously adjusted by the control system to maintain this maximum speed. However, it is conceivable that the wind turbine generates enough power to be self-sufficient. The wind turbine then generates its own electricity consumption and does not feed into the grid, but can feed in immediately if necessary.

[0034] According to a further embodiment, it is proposed that the support mode comprise motor operation in which the rotor of the wind turbine is driven by electrical power from the electrical grid. This electrical power for driving the wind turbine should not exceed the solar power currently fed into the electrical grid by the solar power system. Otherwise, the solar power systems would ultimately be unable to contribute to the grid. However, it can generally be assumed that in support mode, particularly when there is a lot of solar radiation, the solar power systems feed significantly more power into the electrical grid than is necessary for this motor operation.Here, too, the underlying idea is that the aforementioned solar systems feed in a lot of power, and a small amount of this power is used to operate the wind turbines in motor mode, but essentially at idle. The rotor blades are adjusted to create as little drag as possible when rotating. However, this low power required to drive the wind turbines allows the rotation of the wind turbine rotors to provide a high instantaneous reserve.

[0035] Photovoltaic systems, in particular, which generate electricity directly from solar radiation, can be supported by wind turbines using the proposed variants. Such photovoltaic systems can fluctuate directly and essentially instantly in their feed-in power when solar radiation fluctuates accordingly. This not only makes it difficult for such photovoltaic systems to support the grid, but when solar radiation fluctuates, they can also contribute to fluctuations in the electrical supply grid themselves if they are sufficiently dominant. This, too, is intended to be taken into account by the invention and compensated for by the behavior of the wind turbines.

[0036] According to one embodiment, it is proposed that the switch to support mode depends on the prevailing wind speed. This switch to support mode is particularly suitable in light wind conditions. In strong wind conditions, it may be advantageous to operate the wind turbine at an optimal operating point, where the wind turbine itself feeds in a high amount of power and thus, as a result, also has an operating point where it also has a high support potential.

[0037] Additionally or alternatively, it is proposed that one property of the support mode be dependent on the prevailing wind speed. For example, at low wind speeds, it may be planned to deliberately provide a high speed in the support mode, thus changing the operating point to a higher speed. At high wind speeds, it may be planned not to change the operating point, but at least to offer a high instantaneous reserve.

[0038] It is preferably proposed that the switch to the support mode and, additionally or alternatively, at least one property of the support mode depend on at least one grid state of the electrical supply grid or on at least one variable representative thereof. This may make it possible to anticipate whether a support mode, namely in particular a support power or instantaneous reserve, might be needed and to what extent it might be needed. The grid states explained below can be taken into account directly in terms of the physical variable or also by means of a value representative of them. The latter is particularly suitable if the respective variable, i.e. the respective grid state, is not directly recorded by the wind turbine.

[0039] Thus, a change or a property of the support mode is proposed depending on the grid frequency. For example, a support mode can be particularly useful when the grid frequency is already comparatively low, for example, when it is below the nominal frequency but still above a lower limit.

[0040] A grid frequency change can also provide an indication of whether a support mode appears to be necessary soon. In a particularly quiet grid, i.e., when there are few and / or only minor grid frequency changes, a support mode is less necessary than when the grid is rather unstable in terms of frequency changes.

[0041] Considering a grid frequency change gradient can also be helpful in assessing whether a support mode appears necessary. In this case, a grid frequency change is quantitatively evaluated based on its change amplitude. The frequency of the frequency change is not important. Nevertheless, it can be advantageous to consider both the frequency of the grid frequency change, i.e., how unstable the grid is, and the grid frequency change gradient, i.e., the amplitude of the frequency change.

[0042] Another important network condition is the grid voltage. Especially at a comparatively high voltage, the need for a backup mode is more likely than at a lower voltage. The characteristics of the measuring point for this grid voltage measurement must be considered, as the grid voltage in a complex electrical supply network varies with its location.

[0043] It is also suggested that changes in the grid voltage be taken into account. For example, a falling grid voltage can indicate the need for a backup mode, even if the grid voltage initially remains comparatively high.

[0044] It is also proposed that an external grid status signal be considered, indicating the grid status. The support mode and, if necessary, its properties can be selected based on this. This takes into account the fact that the grid operator, who operates the electrical supply grid, has information about the electrical supply grid, particularly from different grid points. Based on this, better conclusions can be drawn about the needs or expected events of the electrical supply grid.

[0045] According to one variant, it is proposed to consider a frequency converter share, which indicates the ratio of power fed into the electrical grid by frequency converters to the total power fed into the electrical grid. For example, if the share of frequency converters in the grid, i.e., only in relation to the power fed in by them, is greater than 80%, and the share of photovoltaic systems, which also feed into the grid via a frequency converter, is greater than 50%, this can have an impact on the electrical grid.

[0046] One way to identify the frequency converter share could be for the operator of the electrical grid to be aware of this and for this information to be passed on to the wind turbines concerned.

[0047] The choice of a support mode can also depend on whether a grid operator transmits a corresponding request signal for an instantaneous reserve, i.e., whether an instantaneous reserve is requested by a grid operator. This can also mean that such an instantaneous reserve is requested at a certain level based on the power fed in. In this case, such a power-dependent request could be converted into an instantaneous reserve for the wind turbines, taking into account the power feed-in of the photovoltaic systems considered, which would then take over this function for the solar systems.

[0048] According to one embodiment, it is proposed that the at least one wind turbine switch to support mode and increase its speed compared to normal mode when the at least one solar system feeds at least a predeterminable minimum proportion of its rated power, in particular 50% of its rated power, into the electrical grid and, in addition, a need for an instantaneous reserve has been detected. This allows the specific selection of this support mode.

[0049] It is preferably proposed that the at least one wind turbine is permanently operated in the support mode with a rotor speed that is higher than in the normal mode, as long as the at least one solar system feeds at least a predeterminable minimum proportion of its rated power, in particular at least 50% of its rated power, into the electrical supply grid and the prevailing wind is so weak that the at least one wind turbine can feed at most a predeterminable maximum proportion of its rated power, in particular at most 50% of its rated power, into the electrical supply grid.The idea behind this is that the weather situation, namely, to put it simply, lots of sun and little wind, is taken into account and the solar systems are used accordingly to feed in as much power as possible and the wind turbines are essentially used to support the electrical supply grid, at least to be able to provide backup power when needed.

[0050] According to one embodiment, a solution is proposed that is characterized by detecting a requirement for a relative instantaneous reserve, wherein this relative instantaneous reserve indicates an additional power that can be fed in relative to a reference power. Based on this detected requirement for the relative instantaneous reserve and a solar reference power characteristic of the solar system, a solar instantaneous reserve is determined, which is a power that characterizes an instantaneous reserve to be maintained or provided by the solar system. This solar instantaneous reserve is thus a calculated value if the total instantaneous reserve to be provided is distributed equally among the power-feeding generators.

[0051] To this end, it is proposed that at least one wind turbine be operated in a support mode so that it can provide the determined instantaneous solar reserve. Preferably, it can provide this in addition to an instantaneous reserve that it would have to feed in due to its own operation and the relative instantaneous reserve. This makes it possible, in particular, to quantify the size of a standardized instantaneous reserve provision. It is proposed that generators who cannot feed in the instantaneous reserve calculated for them, or who can only do so with great effort, have this provision taken over by suitable wind turbines. The wind turbines can then take over this requirement from the solar plants, particularly in a support mode.

[0052] Preferably, it is proposed that the relative instantaneous reserve indicates the additional power that can be fed into the grid relative to the power currently fed into the electrical grid or a relevant grid section. According to this proposal, the reference power is the power that is currently fed into the electrical grid or that is fed into a relevant grid section.

[0053] Additionally, or alternatively, the solar reference power is the solar power currently fed into the electrical grid by the solar system. Thus, the current actual value is also used here.

[0054] Additionally or alternatively, the at least one wind turbine is then operated in a support mode such that it has a higher speed than its normal mode, thereby providing the instantaneous solar reserve for the solar system. In particular, this allows the provision or feed-in of the instantaneous solar reserve to be achieved.

[0055] Preferably, the instantaneous solar reserve is calculated as the product of the relative instantaneous reserve and the currently fed-in solar power. The relative instantaneous reserve can be a relatively constant value that can be easily multiplied by the currently fed-in solar power, which is generally known, at least for the respective solar system.

[0056] Optionally, it is suggested that a weighting function be considered, in particular by multiplying it by a positive weighting factor. The instantaneous solar reserve can therefore be additionally modified using a weighting function, in particular by multiplying it by a positive weighting factor, which can be in the range of 0.5 to 2. This makes it possible to readjust the instantaneous solar reserve or to take into account special circumstances, such as the specific location of the grid connection point to which the respective solar system feeds in.

[0057] The above and following descriptions of or in connection with solar systems particularly relate to photovoltaic systems.

[0058] According to one embodiment, it is proposed that the method is characterized in that a provideable instantaneous solar reserve is calculated for the solar system, or for a mixed system comprising at least one solar system and at least one wind turbine. This indicates how much instantaneous reserve the at least one wind turbine can maintain with the support of the at least one solar system when the wind turbine is operated in a corresponding support mode. For this purpose, it is proposed that this provideable instantaneous solar reserve be calculated as a function of the solar power currently fed in, the wind power currently fed in by the at least one wind turbine in normal mode, and the grid status of the electrical supply grid or the variable representative thereof.The available instantaneous solar reserve is therefore something that can be provided and accessed when needed, meaning it is not permanently available or even fed into the grid. It is therefore the value that indicates up to what level an available instantaneous solar reserve should be maintained. This takes into account the solar power currently fed into the grid, as this is to be supplemented by the backup power of the wind turbine. It also includes the normal mode in which the wind turbine could operate if it does not switch to backup mode. The grid status of the electrical supply grid is also taken into account, as this can ultimately determine whether there is any need for backup power at all.

[0059] According to the invention, a wind energy plant is also proposed which can generate electrical energy from wind for feeding into an electrical supply network and wherein the wind turbine has an aerodynamic rotor with rotor blades whose blade angle is adjustable, the rotor can be operated at a variable rotor speed, and the wind turbine has a generator coupled to the aerodynamic rotor for generating generator power, wherein the wind turbine is operated in a normal mode in which it feeds available wind power up to a nominal power into the electrical supply grid, wherein the available wind power refers to power that can be generated from the wind by the wind turbine and fed into the electrical supply grid depending on the wind and technical limits, and the wind turbine changes from a normal mode to a support mode depending on an operating situation of at least one solar system feeding into the same grid.

[0060] In particular, a wind turbine is proposed that is prepared to carry out a method according to at least one embodiment described above. For this purpose, it comprises, in particular, a process computer on which the method is implemented. However, it is also conceivable that it is connected to external computers or has corresponding interfaces in order to be able to take into account external variables necessary for the method. Part of the method can also be executed or controlled on an external process computer.

[0061] Preferably, a weather module is provided for evaluating and / or recording weather data, which can also detect solar radiation in terms of its magnitude. This is based on the understanding that detecting solar radiation at the at least one wind turbine can provide sufficient information about the available photovoltaic power of a nearby photovoltaic system. The weather module can have a photocell for measuring light and / or an interface for receiving external weather data.

[0062] A wind farm with multiple wind turbines is also proposed. The wind farm thus comprises at least two wind turbines as described above, and these at least two wind turbines feed into the electrical grid via a common grid connection point. This allows the method to be used particularly efficiently by using multiple wind turbines, as it can create a large potential for instantaneous reserve or other backup power.

[0063] According to the invention, a wind energy system is also proposed which comprises at least one wind farm described above and at least one solar installation, wherein the at least one solar installation feeds into the same electrical supply grid. This solar installation can preferably feed into the electrical supply grid via a different grid connection point than the wind farm. This ensures that, in principle, both the wind farm and the at least one solar installation can be operated independently of one another. At the same time, a synergy is created in which the wind energy installations, i.e. the wind farm, take on support tasks, in particular the provision of support power or instantaneous reserve, for the solar installation. This occurs because the wind energy installation switches from its normal mode to a support mode depending on the operating situation of the at least one solar installation.

[0064] The invention is explained in more detail below using exemplary embodiments with reference to the accompanying figures. Figure 1 shows a perspective view of a wind turbine. Figure 2 shows a schematic diagram of a wind farm. Figure 3 shows a schematic section of an electrical grid. Figure 4 illustrates possible relationships between instantaneous reserve power and a frequency change in the electrical grid.

[0065] Figure 1 shows a wind turbine 100 with a tower 102 and a nacelle 104. A rotor 106 with three rotor blades 108 and a spinner 110 is arranged on the nacelle 104. During operation, the rotor 106 is set into rotation by the wind and thereby drives a generator in the nacelle 104.

[0066] Figure 2shows a wind farm 112 with, for example, three wind turbines 100, which may be identical or different. The three wind turbines 100 are thus representative of essentially any number of wind turbines in a wind farm 112. The wind turbines 100 provide their power, namely in particular the generated electricity, via an electrical farm grid 114. The currents or power generated by the individual wind turbines 100 are added together, and a transformer 116 is usually provided, which steps up the voltage in the farm and then feeds it into the supply grid 120 at the feed-in point 118, which is also generally referred to as a PCC. Fig. 2is only a simplified representation of a wind farm 112, which, for example, does not show a control system, although a control system is of course present. The farm network 114 can also be designed differently, for example, by also providing a transformer at the output of each wind turbine 100, to name just one other embodiment.

[0067] Figure 3 shows a section of an electrical supply network 2, to which a photovoltaic system 4 and a wind farm 6 with wind turbines 7 are schematically connected. The wind farm 6 can, like the wind farm 112 of the Figure 2 be trained and wind turbines 7 each like the wind turbine 100 of the Figure 1 The electrical supply network 2 can be connected to the electrical supply network 120 of the Figure 2 are equivalent to.

[0068] Representative for other consumers or feeders shows Figure 3a town 8 connected to the electrical grid 2, an industrial consumer 10, which may be a factory, for example, and a large power plant 12 as a further generator.

[0069] The schematically drawn sun 14 and the flaccid windsock 16 are intended to indicate that the Figure 3for the electrical supply grid 2 shown, a general weather situation prevails in which strong solar radiation and little wind prevail. Accordingly, the photovoltaic system 4, which can also be referred to simply as a PV system, generates a lot of electrical power P PV , which is fed into the electrical supply grid 2. The thickness of the arrow and the other arrows described below is intended to at least illustrate the level of power. A lot of PV power P PV is therefore fed into the electrical supply grid, which is divided into the power components P 1 and P 2 , which flow into different areas of the electrical supply grid 2. This is only for illustrative purposes to make it clear that this power P PV generated by the PV system 4 is generally made available to the electrical supply grid 2.

[0070] In addition, a power share P 3 is marked with a thin arrow and should therefore only represent a small proportion of the PV power P PV fed in. This additional power share P 3 is made available to wind farm 6. It should be noted that this is also only for illustrative purposes and this power share P 3 does not necessarily come directly from PV system 4. Rather, the point is that wind farm 6 draws a power share P 3 that is significantly lower than the power P PV fed in by the PV system. This means that the power share P 3 can, at least mathematically, be part of the total PV power P PV fed in.

[0071] In this illustration of the Figure 3It is therefore assumed that the wind farm 6 cannot generate any power from wind in the situation shown. The power component P 3 is then used to set the rotors 18 in rotation 20. The rotors 18 can be used to rotate the rotors 106 according to Figure 1 The rotation 20 is indicated by corresponding arrows in the Figure 3 indicated.

[0072] Thus, the rotors 18 of wind farm 6 are set in rotation and are maintained in this rotational movement. The power component P 3 can be used for this purpose. The wind turbines 7 of wind farm 6 and thus also wind farm 6 as such are thus in a support mode. In the situation shown, Figure 3 In a situation where there is no wind, the normal mode would be for the wind turbines to be switched off or at most kept in standby mode.

[0073] Because these rotors 18 are each set in a rotation 20, each wind turbine 7 exhibits kinetic energy in the form of rotational energy of the respective rotor 18. The wind farm 6 thus exhibits a high amount of rotational energy overall. As a precautionary measure, it should be noted that only four wind turbines 7 are shown schematically in the wind farm 6, but that significantly more wind turbines may be present in the wind farm and operated as described, e.g., more than 20, more than 50, or even more than 100 wind turbines 7.

[0074] This available rotational energy can be fed in as instantaneous reserve power PM to support the electrical supply grid 2 if necessary. A wide, broken arrow is drawn for illustrative purposes. This is intended to demonstrate that this instantaneous reserve power PM can be fed in if necessary, but that it is not fed in continuously, but only in brief moments when appropriate support of the electrical supply grid 2 is necessary. In such cases, however, a large backup power PM can also be fed in.

[0075] Such a feed-in of such support power PM may be necessary, for example, when the industrial consumer 10 is connected to the electrical supply network 2, or when a large amount of power is suddenly drawn in the city 8.

[0076] The Figure 3illustrates a type of support mode for a special situation in which there is no wind at all. However, other variants are also conceivable, such as where there is sufficient wind to feed at least some power into the electrical supply grid 2 via the wind farm 6. According to one variant, the wind farm 6 and thus the wind turbines 7 would be operated at an optimal operating point in which, in particular, the speed of the rotors 18 has an optimal value for the prevailing wind. This operating point can be retained for the selection of the support mode. Nevertheless, a high value of instantaneous reserve power PM is offered. This can mean that a different dependency is used for a frequency change-dependent feed-in of the instantaneous reserve power PM than in normal mode.

[0077] Such a situation is in the Figure 4In the diagram of the Figure 4 An instantaneous reserve power PM is plotted as a function of the frequency change df / dt for two cases. The instantaneous reserve power PM is normalized to a maximum instantaneous reserve power P Mmax that can be fed in, which is the same for both operating modes. The frequency change of the electrical supply network df / dt is also normalized, namely to a maximum df / dt. In addition, -df / dt is plotted. The diagram of the Figure 4 thus generally shows negative values ​​of the frequency change df / dt. The normalized abscissa ranges from 0 to -1.

[0078] As an example, two dependency functions for the instantaneous reserve power PM are shown, namely the instantaneous reserve power P MS for the support mode and the instantaneous reserve power P MN for the normal mode.

[0079] In this illustrative example, the gradient of the instantaneous reserve power P MS for the backup mode is twice as large as the gradient of the instantaneous reserve power P MN for the normal mode. Furthermore, in the backup mode, the instantaneous reserve power P MS is also called up earlier, i.e., at a smaller frequency change df / dt, than is the case for the instantaneous reserve power P MN, which, in this example, is only called up at a frequency change df / dt that is twice as large.

[0080] To the extent that the instantaneous reserve power PM is understood as a function of the frequency change that exceeds an initial limit, the instantaneous reserve power P MS of the backup mode always provides a value twice as large as the instantaneous reserve power P MN of the normal mode. For example, the instantaneous reserve power P MS of the backup mode has a standardized power value of slightly more than 0.4 for a standardized frequency change of 0.4, i.e., 0.2 above its initial value. In contrast, the instantaneous reserve power P MN of the normal mode has a standardized power value of approximately 0.2 for a standardized frequency change of 0.6, i.e., 0.2 above its initial value. This is half the corresponding value of the instantaneous reserve power P MS of the backup mode.

[0081] This is also just an explanatory example and it is also possible, for example, that the two starting values ​​of the normal mode and the support mode are identical and / or zero.

[0082] It was therefore recognized that if a high proportion of electricity generation is covered by renewable energies, there may be a need for the provision of instantaneous reserves by converter-based generation systems. It was recognized that PV systems can only realize instantaneous reserves through the integration of additional storage. To this end, it is now proposed that wind turbines also be used to provide instantaneous reserves when the wind is not blowing but a large proportion of PV electricity is fed into the grid as a result of solar radiation. One suggestion for this is to use the wind turbines' motors to speed them up in order to support the grid from rotor energy or rotational energy when instantaneous reserves are required. This is also based on the recognition that if a high proportion of electricity demand is covered by PV, at least statistically speaking, hardly any wind energy is fed into the grid and therefore the capacities of the wind turbine converters are hardly utilized.However, there are also other possibilities for implementation, as explained above.

[0083] The proposed invention also aims to improve the grid integration of renewable energy sources in general. Since instantaneous reserve provision may be required at any time in the grid, one idea is to implement this using wind turbines. It was recognized that wind turbines are generally very well suited for instantaneous reserve provision because the rotor mass, in particular the moment of inertia of each rotor, is very high relative to the installed power.

[0084] This can improve the grid integration of renewable energies in general, and especially for wind turbines and photovoltaic systems, thus achieving a high proportion of electricity generation from renewable energy sources. Conventional power plants can also be replaced by wind turbine-based power plants. Furthermore, a grid-related upper limit on the expansion of renewable energy sources, which could be imposed due to a lack of grid support or which already exists, can be avoided or at least increased. In principle, the proposed solutions also enable fully converter-fed grids, or at least make them more achievable.

[0085] One proposed solution is motor operation or spin operation of the wind turbines to provide instantaneous reserve using the rotor's kinetic energy. A key advantage of the invention is the avoidance of rotating phase shifters or the installation of storage devices in photovoltaic (PV) systems to provide instantaneous reserve. This not only reduces the costs of grid integration of renewable energies in general, but the proposed solution also offers wind turbine operators the opportunity to offer an additional system service. Such functionality is particularly suitable for implementation in the turbine or wind farm control system.

[0086] According to the invention, the following embodiment 1 is also proposed, which can be combined with all other described embodiments, in particular with the subject matter of all claims: Embodiment 1:Method for controlling at least one wind energy plant (7) for generating electrical energy from wind for feeding into an electrical supply network (2), wherein the wind turbine (7) has an aerodynamic rotor (18) with rotor blades whose blade angle can be adjusted, the rotor (18) can be operated at a variable rotor speed, and the wind turbine (7) has a generator coupled to the aerodynamic rotor (18) for generating generator power, wherein the wind turbine (7) is operated in a normal mode in which it feeds available wind power up to a nominal power into the electrical supply grid (2), wherein the available wind power designates a power which, depending on the wind and technical limits, can be obtained from the wind by the wind turbine (7) and fed into the electrical supply grid (2), and the wind turbine (7) changes from a normal mode to a support mode depending on an operating situation of at least one solar system feeding into the same electrical supply grid (2).

Claims

1. A method for controlling at least one wind power installation (7) for generating electrical energy from wind for infeed into an electrical supply network (2), wherein - the wind power installation (7) has an aerodynamic rotor (18) with rotor blades which can be adjusted in respect of their blade angle, - the rotor (18) can be operated at a variable rotor rotational speed, and - the wind power installation (7) has a generator, which is coupled to the aerodynamic rotor (18), for generating a generator power, wherein - the wind power installation (7) is operated in a normal mode in which it feeds available wind power up to a rated power into the electrical supply network (2), wherein the available wind power indicates a power which can be obtained from the wind and fed into the electrical supply network (2) depending on the wind and technical limitations of the wind power installation (7), and - the wind power installation (7) changes over from a normal mode to a support mode depending on an operating situation of at least one solar installation which feeds into the same electrical supply network (2), wherein - the wind power installation (7) can provide more instantaneous reserve in the support mode than in the normal mode.

2. The method as claimed in claim 1, characterized in that an instantaneous reserve power PM is fed into the electrical supply network (2) depending on a change in frequency df / dt of a network frequency f which is detected in the electrical supply network (2), wherein different dependencies of the instantaneous reserve power PM on the change in frequency df / dt are provided between the normal mode and the support mode in such a way that, in the case of the same change in frequency df / dt, the magnitude of the instantaneous reserve power PM in the support mode is greater than in the normal mode, in particular the instantaneous reserve power PM is calculated using the formula PM=k*df / dt, where k is a dependency factor and, in respect of magnitude, is greater in the support mode than in the normal mode.

3. The method as claimed in one of the preceding claims, characterized in that, for the purpose of supporting the electrical supply network (2), a support power, in particular an instantaneous reserve power, is offered, which support power can be called up for the purpose of infeed into the electrical supply network (2), or which support power can be fed in depending on a network behavior, wherein the at least one wind power installation (7) offers a higher support power in the support mode than in the normal mode.

4. The method as claimed in one of the preceding claims, characterized in that, in the support mode, the wind power installation (7) at least temporarily feeds less power into the electrical supply network (2) than in the normal mode or draws power from the electrical supply network (2) in order to provide an increased instantaneous reserve in this way.

5. The method as claimed in one of the preceding claims, characterized in that the support mode of the wind power installation (7) comprises at least one operating mode selected from the list comprising - an idling operating mode in which the rotor (18) of the wind power installation (7) rotates by virtue of being driven by the wind, without generating power, - a high rotational speed operating mode in which the rotor (18) of the wind power installation (7) rotates at high rotational speed, wherein no power or only little power is fed in, and - a zero-power operating mode in which the rotational speed is increased up to the maximum rotational speed without power infeed, and - a motorized operating mode in which the rotor (18) of the wind power installation (7) is driven by electrical power (PPV) from the electrical supply network (2), which electrical power does not exceed the solar power instantaneously fed into the electrical supply network (2) by the solar installation.

6. The method as claimed in one of the preceding claims, characterized in that - the changeover to the support mode depends on the prevailing wind speed and in addition or as an alternative - at least one property of the support mode depends on the prevailing wind speed.

7. The method as claimed in one of the preceding claims, characterized in that - the changeover to the support mode and in addition or as an alternative - at least one property of the support mode depends on at least one network state of the electrical supply network (2) or a variable which represents said network state, selected from the list comprising - a network frequency, - a change in network frequency, - a gradient of the change in network frequency, - a network voltage, - a change in network voltage, - an external network status signal which indicates a network state, - a frequency converter proportion which specifies a ratio of the power which is fed into the electrical supply network (2) by frequency converters to the total power which is fed into the electrical supply network (2), and - a request signal which is transmitted by a network operator for requesting an instantaneous reserve.

8. The method as claimed in one of the preceding claims, characterized in that the wind power installation (7) changes over to the support mode and the rotational speed thereof increases in comparison to the normal mode when - the at least one solar installation feeds at least a prespecifiable minimum proportion of its rated power, in particular 50% of its rated power, into the electrical supply network (2) and - a requirement for an instantaneous reserve has been detected.

9. The method as claimed in one of the preceding claims, characterized in that the at least one wind power installation (7) is permanently operated in the support mode at a rotor rotational speed which is increased in comparison to the normal mode, provided that - the at least one solar installation feeds in at least a prespecifiable minimum proportion of its rated power, in particular at least 50% of its rated power, into the electrical supply network (2) and - the prevailing wind is so weak that the at least one wind power installation (7) can feed at most a prespecifiable maximum proportion of its rated power, in particular at most 50% of its rated power, into the electrical supply network (2).

10. The method as claimed in one of the preceding claims, characterized in that - a requirement for a relative instantaneous reserve is detected, wherein this relative instantaneous reserve identifies a power, which can additionally be fed in, with respect to a reference power, - a solar instantaneous reserve is determined as the power which identifies an instantaneous reserve which is to be kept in reserve or to be provided by the solar installation, based on the detected requirement for the relative instantaneous reserve and a solar reference power which identifies the solar installation, and - the at least one wind power installation (7) is operated in a support mode such that it can provide the determined solar instantaneous reserve.

11. The method as claimed in claim 10, characterized in that - the relative instantaneous reserve specifies the power, which can additionally be fed in, with respect to a power which is instantaneously fed into the electrical supply network (2) or a relevant network section, and / or - the solar reference power specifies the solar power which is instantaneously fed into the electrical supply network (2) by the solar installation, and / or - the at least one wind power installation (7) is operated in a support mode such that it has an increased rotational speed in comparison to its normal mode in order to provide the solar instantaneous reserve for the solar installation in this way.

12. The method as claimed in claim 10 or 11, characterized in that - the solar instantaneous reserve is produced as the product of the relative instantaneous reserve and the instantaneously fed-in solar power, wherein optionally - a weighting function is taken into account, in particular by multiplication of the solar instantaneous reserve by a positive weighting factor.

13. The method as claimed in one of the preceding claims, characterized in that, for the solar installation or for a mixed installation which comprises the at least one solar installation and the at least one wind power installation (7), depending on - the instantaneously fed-in solar power, - the wind power which is instantaneously fed in by the at least one wind power installation (7) in the normal mode, and - the network state of the electrical supply network (2) or of the variable representing said network state, - a solar instantaneous reserve which can be provided is calculated, said solar instantaneous reserve specifying how much instantaneous reserve the at least one wind power installation (7) can keep in reserve with the assistance of the at least one solar installation when the wind power installation (7) is operated in a corresponding support mode.

14. A wind power installation (7) for generating electrical energy from wind for infeed into an electrical supply network (2), wherein - the wind power installation (7) has an aerodynamic rotor (18) with rotor blades which can be adjusted in respect of their blade angle, - the rotor (18) can be operated at a variable rotor rotational speed, and - the wind power installation (7) has a generator, which is coupled to the aerodynamic rotor (18), for generating a generator power, wherein - the wind power installation (7) is operated in a normal mode in which it feeds available wind power up to a rated power into the electrical supply network (2), wherein the available wind power indicates a power which can be obtained from the wind and fed into the electrical supply network (2) depending on the wind and technical limitations of the wind power installation (7), and - the wind power installation (7) changes over from its normal mode to a support mode depending on an operating situation of at least one solar installation which feeds into the same electrical supply network, wherein - the wind power installation (7) can provide more instantaneous reserve in the support mode than in the normal mode.

15. The wind power installation (7) as claimed in claim 14, characterized in that it is primed to execute a method as claimed in one of claims 1 to 13, wherein it has, in particular, a process computer on which the method is implemented.

16. A wind farm (6) comprising at least two wind power installations (7) as claimed in claim 14 or 15, wherein the wind power installations (7) feed into the electrical supply network (2) via a common network connection point.

17. A wind power system comprising at least one wind farm (6) as claimed in claim 16 and at least one solar installation, wherein the at least one solar installation feeds into the same electrical supply network (2), preferably via a different network connection point, and wherein the wind power installations (7), in each case change over from its normal mode to a support mode depending on an operating situation of the at least one solar installation.