METHOD FOR CONTROLLING A WIND POWER PLANT TO PROTECT BIRDS AND BATS

Description

[0001] The present invention relates to a method for controlling a wind turbine and to a corresponding wind turbine.

[0002] Wind turbines have a rotor with multiple blades. To generate electrical power from wind, the wind sets the rotor in motion. Due to the large size of such a rotor, which often has a diameter of over 100 meters, and frequently even over 150 meters, speeds of up to 300 km / h can occur at the outer edge of the rotor, and thus at the tips of the blades.

[0003] Such high speeds can pose a danger to birds and bats, because even fast-flying birds cannot properly judge such high speeds and can therefore be injured or even killed by a rotor blade moving so quickly.

[0004] It is particularly problematic when wind turbines are to be erected and operated in the habitat of endangered bird or bat species. If no solution is found to protect such endangered species, the construction of a wind turbine may be completely prohibited.

[0005] Ultimately, for the well-known reasons, wind turbines are environmentally friendly compared to conventional power plants, and therefore every effort should be made to install a wind turbine while protecting endangered species in other ways.

[0006] One way to protect endangered species is to only operate wind turbines located near the habitat of endangered species when the endangered animals are not nearby.

[0007] It is known that bats do not fly under unfavorable conditions (too cold, too much rain, too stormy or too bright), so that at such times the wind turbine can be operated without endangering the bats.

[0008] For birds, and this can also be applied to bats, systems are now available that can automatically detect whether an animal is getting too close to a wind turbine. Such systems are even capable of identifying the species of animals flying into an area near the wind turbine.

[0009] This makes it possible to identify an animal flying near a wind turbine and, based on this identification, to stop the turbine before the animal can reach it. Such systems work quite well, but still frequently lead to unnecessary shutdowns, because very few animals that approach a wind turbine to a certain distance actually fly towards it. For those animals that do fly towards the turbine, stopping the turbine is correct and important. In all other cases, however, this results in an unnecessary loss of energy yield.

[0010] The state of the art is reflected in the documents DE 10 2019 220 281 B3, EP 3 123 025 B1, EP 2 673 502 B1 and EP 2 017 470 A1.

[0011] The present invention therefore aims to address at least one of the aforementioned problems. In particular, it seeks to propose a solution in which a wind turbine poses as little risk as possible to endangered species of birds and bats, while simultaneously achieving the highest possible yield. At the very least, it aims to propose an alternative to existing solutions.

[0012] According to the invention, a method according to claim 1 is proposed. This method is thus a method for controlling a wind turbine that has a rotor with rotor blades adjustable in their blade angle and with a rotor diameter. The rotor, and thus the wind turbine as a whole, can be operated at a variable rotor speed. The area in which the rotor blades move constitutes a danger zone for birds and bats. Starting from this premise, the method proceeds according to the following steps.

[0013] In one step, a bird or bat approaching the wind turbine is assessed to determine if it is a vulnerable species. For the sake of simplicity, birds and bats will subsequently be referred to as "birds," and if one of these animals approaches the wind turbine, specifically in flight, it will be classified as a vulnerable species. Similarly, a bat approaching the wind turbine will also be referred to as a vulnerable species for the same reason. While it is understood that a bat is not a bird, the solutions proposed here have been recognized as also being applicable to bats. Any special considerations will be explicitly noted.

[0014] A further step, once a vulnerable bird has been identified, is to record its current position. This focuses particularly on the distance at which the vulnerable bird is located, but additional information can be considered, such as the specific direction from which the bird approached the wind turbine. The bird's altitude at that moment can also provide further information about its position.

[0015] The next step proposes controlling the rotor speed based on the bird's position relative to the wind turbine. The rotor speed would be reduced in several stages or continuously as the bird's distance from the turbine decreases.

[0016] The exact distance of the bird's position, i.e., the distance of the endangered bird to the wind turbine, is taken into account, and the rotor speed is reduced accordingly; the closer the endangered bird is to the wind turbine, the greater the reduction.

[0017] For example, to illustrate this, the rotor speed can be lower the closer the endangered bird is to the wind turbine. However, this is just one example, and there doesn't necessarily have to be a proportional, i.e., linear, relationship between distance and rotor speed; various other criteria can also be taken into account, as will be explained below.

[0018] Ideally, the rotor speed is continuously controlled based on the distance to the bird's position, but a stepwise reduction is also possible. For example, ten distances can be defined, each with a predefined rotor speed. Such a multi-step reduction of the rotor speed is very similar to a continuous reduction, because even with stepwise reduction, the speed reduction often occurs in practice continuously, as a rotational speed cannot be changed abruptly. However, a target rotational speed can be changed abruptly.

[0019] The underlying principle is that a wind turbine requires a certain amount of time to reduce its rotational speed to zero, or at least to a speed that is safe for the endangered bird. As long as the endangered bird is far enough away from the wind turbine that it cannot reach it during this time, the wind turbine can continue to operate normally. However, if the endangered bird gets too close to the wind turbine, the rotational speed can be reduced accordingly to zero or to a low speed that does not endanger the bird.

[0020] However, it was recognized that the endangered bird does not necessarily continue flying towards the wind turbine after falling below such an initial critical distance. If the bird turns around, for example, or flies in a different direction, it is sufficient to simply reduce the rotor speed slightly.

[0021] The underlying principle here is that reducing the rotor speed to a level from which it could be further reduced to zero or a safe speed within a reasonable timeframe if the bird continues flying towards the wind turbine. The closer the vulnerable bird is to the wind turbine, the less time it would need to reach it. Consequently, the wind turbine has less time to reduce its rotor speed to zero or a safe speed. In this sense, the rotor speed is adjusted to the bird's position. The closer the vulnerable bird is to the wind turbine, the lower the rotor speed, ensuring it can still be reduced to zero or a safe speed before the bird reaches the turbine.

[0022] One aspect of the proposal is that the endangered bird should be identified by its species or other category. This would allow for species-level identification, particularly to provide targeted protection for endangered and strictly or specially protected species. This naturally includes, in the case of a bat, at least classification as a bat and, if possible, species identification. However, another category, such as size classification (e.g., small, medium, and large), could also be considered.

[0023] It is further proposed that a response zone around the wind turbine be defined depending on the identified bird species. This response zone has a defined boundary and is defined by the wind turbine's ability to reduce its rotor speed to a spin speed, a safety speed, or zero before the endangered bird of the identified species is expected to reach the danger zone from the boundary of the response zone. It is further proposed that the rotor speed be reduced as soon as the endangered bird enters the response zone, and that the rotor speed be reduced further as the endangered bird approaches the danger zone, without shutting down or stopping the wind turbine.

[0024] If the endangered bird is outside the response area, the wind turbine can be operated normally. However, if the endangered bird approaches the edge of the area from the outside, the protective control system activates and reduces the rotor speed as the endangered bird gets closer to the danger zone.

[0025] The reaction zone, and especially its boundary, is designed so that the identified bird species cannot reach the danger zone before the rotor speed has been reduced to a safe level, provided the endangered bird is outside the reaction zone, i.e., at least the distance between the boundary and the danger zone. However, it was recognized that the wind turbine requires a certain amount of time to reduce the rotor speed accordingly, and that an endangered bird can fly a different distance during this time, depending on the species. The reaction zone is adjusted accordingly.

[0026] It should also be noted that the danger zone does not necessarily have to be a circle in a horizontal plane, but rather defines the area in which the rotor blades move. In a top view, this can be an area that is slightly larger than the rotor diameter perpendicular to the rotor axis, but significantly shorter along the rotor's longitudinal axis.

[0027] In any case, the reaction range will be chosen to be larger the faster an endangered bird of the identified bird species can fly.

[0028] If the bird flies into the reaction area, the rotor speed is reduced, but not automatically to zero or a safe speed, but only as much as is necessary due to the remaining distance of the endangered bird to the danger area.

[0029] A rotor speed of zero is therefore a safe speed. A spin speed can also be a safe speed. A spin speed is a speed that the wind turbine can reach during spin operation, where the rotor blades are set at a spin angle. This spin angle can be around 60°. At this spin angle, the rotor blades are turned so far out of the wind that they no longer function as an aerodynamic profile in which a laminar airflow flows along a suction side and a pressure side of the rotor blade, exerting a suction or pressure force. Nevertheless, the wind can still exert a partial pressure force on the rotor blades, resulting in a slight movement, namely rotation of the rotor.

[0030] A spin speed is typically in the range of 1 to 3 revolutions per minute.

[0031] A protective speed can also be provided, which is a speed at which the specific rotor poses no danger to the endangered bird. Such a protective speed can depend in particular on the size of the rotor, i.e., rotor diameter or blade length, because the longer a rotor blade is, the higher the circumferential speed at its tip. Preferably, the protective speed is predetermined depending on the identified bird species.

[0032] According to one aspect, it is proposed that the number of birds or bats approaching the wind turbine be identified as the number of endangered birds, and that the control of the wind turbine, in particular the control of the rotor speed, be carried out depending on the identified number of endangered birds.

[0033] It was recognized that some birds exhibit flocking behavior, and a course of action can be derived from this. It is also conceivable that a higher risk can be tolerated if only a few endangered birds are present, so that, depending on the species, a reduction in rotational speed is implemented later or not at all. It is preferably proposed that the wind turbine be controlled based on the identified number of endangered birds, in accordance with the same principles as those proposed for control based on the identified bird species or other categories.

[0034] This allows an identified number of endangered birds to be categorized as small, medium or large, and the rotational speed to be controlled accordingly.

[0035] Thus, the identified number of endangered birds, which can be synonymously referred to as the bird count, can also serve as a trigger criterion. It is proposed that several targets, i.e., several birds, be monitored simultaneously. It is suggested that the control system, particularly for triggering a stop, should focus on the individual closest to the turbine or on the individual with the highest probability of a collision. Here, too, speed, flight direction, and other criteria can be used as a basis. Preferably, a reduction or shutdown of the system should be implemented for flocks of five or more birds within a predetermined distance of the wind turbine site.

[0036] According to the invention, the rotor speed is predetermined by a speed-distance function, where the speed-distance function defines a rotational speed as a function of the distance between the endangered bird and the danger zone. This is the distance between the bird's position and the danger zone. The required rotational speed can thus be precisely determined by the speed-distance function as a function of the distance between the endangered bird and the danger zone. To implement this, only the bird's position needs to be determined, from which the distance between the endangered bird and the danger zone can be calculated. Based on this determined distance, the corresponding rotational speed, namely the rotor speed, can then be read from the speed-distance function. The expected rotor speed is thus precisely predetermined, resulting in a highly reproducible method.

[0037] Furthermore or alternatively, it is proposed that the rotor speed and / or the speed-distance function be set or selected depending on a season and / or a time of day and / or the identified bird species.

[0038] This allows for consideration of the specific behaviors of each endangered bird. It has been particularly observed that birds behave differently during the breeding season than outside of it. During the breeding season, a distinction must be made between the period of nest building, the actual incubation of the eggs, and the rearing of the hatched chicks. The general breeding season differs from other periods in that the birds remain close to the nest or nest being built. Nest building involves a high level of activity in gathering building materials, which can lead to different behaviors than during incubation, when usually one bird does not leave the nest while the other searches for food for itself or its mate. Once the chicks have hatched, there is a high level of activity in the search for food to raise them.

[0039] The time of day can also play a role, as different feeding patterns usually occur at different times of day. For example, insects, if they are the food source for the endangered bird, are less likely to be seen at midday. Some birds, especially vultures and large birds of prey, use thermals for flight, so their behavior differs during strong thermals, and thus particularly in the midday heat, compared to, for example, the morning hours.

[0040] Accordingly, the behavior of birds also depends on their species, as already illustrated by the example of birds that utilize strong thermals for flying.

[0041] Accordingly, it is proposed to adjust the rotor speed, because the different behavior of birds according to season, time of day and / or bird species also leads to a different potential approach behavior of the bird in question to the wind turbine, i.e. to the danger zone.

[0042] According to one aspect, it is suggested that the rotor speed is increased again when the endangered bird moves away from the danger zone and is still within the reaction area.

[0043] It was particularly evident here that increasing the rotor speed does not require waiting until the endangered bird has completely left the reaction zone. The method used to reduce the rotor speed as the bird's distance from the danger zone decreases can also be applied in reverse when the bird moves away from the wind turbine. It was recognized that, here too, a bird farther away requires more time to reach the wind turbine than one that is closer. The wind turbine therefore has more time to reduce its rotor speed to a safe level, if necessary, and can thus increase the rotor speed, potentially leading to a higher power output.

[0044] One aspect of the proposal is that the wind turbine should operate at a safety speed and generate power as long as the endangered bird is within the danger zone. The safety speed, as explained above, is a speed considered safe for the endangered bird, even if it is within the danger zone. Specifically, it is therefore proposed that the safety speed be determined based on the identified bird species.

[0045] Such a protective rotor speed is a comparatively low rotor speed, selected so that the blade tip speed is preferably less than 120 km / h, particularly less than 60 km / h, and further, especially less than 30 km / h (8.3 m / s). It was recognized that birds, particularly depending on their species, are only endangered by wind turbine rotors if they rotate too fast. Birds are generally accustomed to flying in such a way that they do not collide with other moving objects, as long as these are not moving too fast.

[0046] This finding was put to good use here, and it was recognized that the wind turbine, even at such a slow safety speed, can still be operated in a way that generates power. This power output will be lower than what could be generated if the wind turbine did not have to be reduced to the safety speed. However, it was recognized that at least some power can be generated.

[0047] The protective rotor speed depends primarily on the identified bird species. In particular, the faster the bird itself can fly, the higher the protective rotor speed can be. It has been observed that birds can accurately judge the speed and movement of an object as long as it moves at approximately the same speed as the bird itself. It has also been found that visual acuity can play a role. Specifically, a higher protective rotor speed is chosen for birds of prey than for non-birds of prey and for bats.

[0048] According to one aspect, it is proposed that the rotor speed be reduced to the protection speed, which is considered safe for the endangered bird if the endangered bird enters the reaction zone. The rotor speed is further reduced to zero or a spin speed if the endangered bird enters a reduced approach danger zone, which has a boundary that lies within the reaction zone but outside the danger zone. The rotor speed is reduced to the point where it reaches the spin speed, or the system is stopped before the endangered bird reaches the danger zone.

[0049] It is further proposed that the wind turbine continue to operate at this protective speed, and in particular to generate power, until the bird reaches the danger zone. It is therefore explicitly proposed that, despite the endangered bird being in the danger zone, the turbine continue to operate while generating power, albeit at a reduced level.

[0050] Here too, it is proposed to specify the reaction speed and / or the protection speed depending on the species of the endangered bird.

[0051] This aspect thus provides for a simplified control system that essentially distinguishes between three rotor speeds: a normal rotor speed, a protection speed, and a spin speed or the value 0. If the endangered bird flies into the reaction zone, the rotor speed is reduced to the protection speed in one step. This is therefore slower than the normal rotor speed, i.e., slower than the rotor speed at which the wind turbine was operating before the bird entered the reaction zone.

[0052] If the bird continues to approach the danger zone, the reduction in rotational speed continues, namely until it reaches spin speed or zero, once it has entered the danger zone. In this further step, this final reduction occurs without necessarily having to precisely monitor the bird's distance from the danger zone. This simple, step-by-step procedure is advantageous because it avoids shutting down the wind turbine, or at least preventing premature shutdown or stopping.

[0053] Conversely, the wind turbine can then be quickly returned to normal operation once the endangered bird has left the response area.

[0054] This aspect therefore proposes two easily implementable steps that nevertheless allow for greater yield than a variant in which the wind turbine is immediately stopped after a bird enters the reaction area.

[0055] One aspect proposes that, as long as the wind turbine is not operating at rated speed and power, i.e., particularly during partial load operation, it should be operated with a characteristic curve that specifies electrical or mechanical power or generator torque as a function of rotor speed. A standard characteristic curve is used as the operating curve when no endangered bird approaching the wind turbine is detected. It is further proposed that a bird protection characteristic curve be used as the operating curve, which, compared to the standard characteristic curve, exhibits higher power or generator torque values ​​for the same rotor speed, or, for the same power or generator torque, a reduced rotational speed if an endangered bird approaching the wind turbine is detected.Furthermore, or alternatively, the use of the bird protection curve is suggested if a threatened bird is detected in an area outside the response zone. It is also suggested, or alternatively, that a bird protection curve be used if there is a high probability that a threatened bird will enter the response zone. This is particularly suggested when there is an above-average probability of this occurring.

[0056] This aspect therefore assumes that the wind turbine operates with a specific operating characteristic curve during partial load operation. Such an operating characteristic curve can also be described as a speed-power curve or a speed-torque curve.

[0057] During partial load operation, the wind speed is below the rated wind speed, so the wind turbine cannot generate its rated power. In this case, a wind turbine is usually operated in such a way that an ideal tip speed ratio is achieved.

[0058] Accordingly, the wind turbine is controlled so that the rotational speed also increases with increasing wind speed, because the tip speed ratio is the quotient of rotational speed and wind speed or of the rotational speed of a blade tip and the wind speed.

[0059] For this purpose, a correspondingly optimal speed-power curve or speed-torque curve is specified, which is referred to here as the standard curve. Control, using the speed-power curve as an example, works by detecting the rotational speed and setting a power output according to the curve. The speed-power curve thus indicates the required power output as a function of the rotational speed. If, for example, the set rotational speed is lower than the power that is being extracted from the wind by the rotor at that moment, the rotational speed increases. Accordingly, a higher power value can then be derived from the speed-power curve, because the speed-power curve is a curve that increases with rotational speed, and this continues until the set power value corresponds to the power that can be extracted from the wind at that moment. At that point, a stable operating point is reached.

[0060] In this sense, a speed-torque characteristic curve is also controlled, which specifies a torque to be set depending on the detected speed.

[0061] The bird protection curve exhibits higher power values ​​or higher generator torque values ​​at the same rotational speed. This means that the maximum power extractable from the wind is already achieved at lower rotational speeds, thus reaching the stable operating point, resulting in a reduced rotational speed for the bird protection curve compared to the standard curve.

[0062] It was found that using a different operating characteristic curve, namely the bird protection curve instead of the standard curve, does reduce the rotational speed, but does not necessarily result in a significant reduction in power. A reduction in power only occurs to the extent that the bird protection curve is less optimal than the standard curve. Therefore, a lower power output can be expected, but it will only be slightly below the power achievable with the standard curve.

[0063] This revealed that a reduction in rotational speed can be achieved without a significant reduction in power output. With this reduced rotor speed, a vulnerable bird can approach the wind turbine more closely before the turbine's rotational speed needs to be further reduced to protect the bird.

[0064] However, such a bird protection characteristic curve does not allow the rotational speed to be reduced arbitrarily while maintaining approximately the same power output. Firstly, this results in an increasingly less aerodynamic operating point, which poses a particular risk of flow separation.

[0065] On the other hand, the same power output at a reduced rotor speed can only be achieved by a correspondingly increased generator torque. However, the generator torque cannot be increased arbitrarily in a generator. It has been recognized, however, that in partial load operation the generator is usually not yet operating at maximum torque, and therefore there is often still the possibility of increasing the generator torque and thus reducing the rotor speed according to the bird protection curve without significantly reducing the power output.

[0066] This approach is particularly recommended when a vulnerable bird approaching the wind turbine has been detected. The bird protection curve can be selected even before the bird has reached its reaction zone. It has been recognized that such a reduction in rotational speed, which barely reduces power output, can also be implemented preventively.

[0067] Therefore, according to one variant, it is also proposed that the bird protection curve be used if a vulnerable bird has been detected in an area outside the response range.

[0068] It is also suggested as a preventative measure to select the bird protection curve if there is a high, especially above-average, probability that a threatened bird will enter the response area. Specifically, it could be planned that the wind turbine operates with a normal curve at night and with the bird protection curve during the day. If no bats are expected, the opposite approach could be proposed. For example, to prevent the return of a bird, a threatened bird is not expected at night. During the day, the probability is therefore higher, and calculated over a 24-hour period, the probability of a threatened bird entering the response area is above average.

[0069] Preferably, it is proposed that the response range be adjusted depending on the bird protection curve. This is based on the understanding that the bird protection curve generally leads to a reduced rotational speed, thus allowing a vulnerable bird to approach the wind turbine to a closer distance before the rotor speed needs to be reduced further. This can be taken into account by adjusting the response range.

[0070] One proposal suggests that if a vulnerable bird approaching the wind turbine is detected, the rotor speed should be reduced by increasing the generator torque. Alternatively, or in addition, the speed could be reduced by adjusting the blade pitch of the rotor blades.

[0071] Increasing the generator torque directly brakes the rotor, thus reducing its speed. This allows for a rapid reduction in speed. Consequently, with a time delay, the power output decreases because the speed is reduced, and power is proportional to the product of speed and torque. The power output can also be increased, which is effectively achieved by increasing the generator torque. Essentially, this results in electrical braking by the generator. This electrical braking is primarily intended as a temporary speed reduction and is limited by the electrical constraints of the wind turbine, particularly in terms of height and, to some extent, duration.

[0072] This reduction in rotor speed is particularly useful when a bird only causes a brief decrease. For longer-term reductions in rotor speed, it is recommended to also adjust the blade pitch. This allows for a sustained reduction. Initially, braking can be achieved electrically, and then, if necessary, supplemented by adjusting the rotor blades.

[0073] Especially when electrical limits and / or the current operating point do not allow an increase in generator torque, it may be possible to adjust the rotor blades only and / or immediately, i.e., to turn them out of the wind.

[0074] Additionally, the rotor blades can be adjusted in their angles. This is particularly useful when the rotor speed needs to be significantly reduced, especially to a safety speed, as simply controlling the generator may not be sufficient, and adjusting the blade angle can further reduce rotor speed.

[0075] According to one aspect, it is proposed that the reduction of the rotor speed be set depending on a detected flight speed of the detected endangered bird and / or a typical, in particular maximum, flight speed of the bird species of the detected endangered bird and / or a flight direction of the detected endangered bird and / or an estimated minimum approach time that the detected endangered bird is expected to need from its current position to reach the danger zone.

[0076] It is therefore proposed to specifically include the recorded and / or expected movement of the identified endangered bird.

[0077] From the recorded flight speed of the bird, it is possible to calculate how fast it needs to overcome the current distance to the danger zone.

[0078] Alternatively, or in addition, a typical, and especially a maximum, flight speed can be considered, which is known based on the identified species of the endangered bird. This essentially allows the minimum time the bird might need to reach the danger zone to be calculated. Using the maximum flight speed is the most reliable method for determining this minimum time. However, if, for example, it is known that the maximum flight speed is not usually reached, or not in the vicinity of a wind turbine, a typical flight speed can be used.

[0079] Furthermore, or additionally, it is suggested that the bird's flight direction be taken into account. For example, if the bird flies quickly into the reaction zone, but in a direction that does not point towards the danger zone, the rotor speed may not need to be reduced, or at least not as drastically.

[0080] According to a supplementary or alternative proposal, a minimum approach time is estimated, representing the minimum time the detected endangered bird is expected to need from its current position to reach the danger zone. Such an estimate of the minimum approach time can consider the previously mentioned criteria, such as recorded flight speed, maximum flight speed, and recorded flight direction. However, other criteria can also be used, such as a detected acceleration or reduction in the flight speed of the detected endangered bird. In addition to flight direction, changes in flight direction can also be considered. For example, if the bird is flying in a circle, this can be taken into account when estimating the minimum approach time. Alternatively, the minimum approach time can be calculated with a high degree of certainty based on the most unfavorable conditions.

[0081] It should also be noted that reducing the rotor speed based on the detected flight speed does not mean that the exact time until the danger zone is reached is calculated and only then does the rotor speed reach the safety speed. Safety margins can also be incorporated. For example, the safety speed may be reached one, two, or five seconds before the bird is expected to enter the danger zone.

[0082] According to one aspect, it is proposed that the wind turbine be operated with a variable safety speed, which is a speed constantly adjusted to the current position of the bird. The safety speed is selected such that the rotor speed can be reduced from the safety speed to the protection speed or a spin speed within the time that the endangered bird is expected to need to travel from its current position to reach the danger zone. In particular, it is proposed that the safety speed be selected such that the reduction of the rotor speed from the safety speed to the protection speed or spin speed is ensured without emergency braking and with continued operation and power generation.

[0083] This allows the rotor speed to be optimally adjusted to the bird's position at all times. In other words, the safety speed is continuously reduced as the bird approaches the danger zone, while it can be continuously increased as the bird moves further away from the danger zone.

[0084] The underlying principle here is that the bird often doesn't fly directly into the danger zone, although this possibility cannot be ruled out. Therefore, the system always calculates how long it might take, should the bird change direction from its current position and head towards the danger zone, before reaching it. This ensures that the safety speed or spin speed can be reached in time. However, as long as the bird maintains a sufficient distance, the speed can be set higher. The safety speed is thus the maximum speed that can be selected without endangering the bird.

[0085] It was particularly noted that the wind turbine can continue operating at this reduced speed, namely the safety speed. Power can still be generated, which only needs to be reduced if the bird behaves in such a way that the safety speed must be lowered, and this cannot be done without reducing power output. It is specifically proposed that the safety speed be set so low that, in the event of the bird flying directly towards the danger zone, the protective speed or spin speed can be reached without emergency braking. In other words, the safety speed is set lower than a speed from which the protective speed or spin speed could only be reached with emergency braking.

[0086] The underlying principle here is that although a lower safety speed is chosen than would absolutely be necessary, the wind turbine can then continue to operate continuously.

[0087] It was particularly noted that an insufficiently set safety speed, which could only be reduced to the protection speed or spin speed by emergency braking, would automatically necessitate such emergency braking if the detected endangered bird suddenly flies towards the danger zone. This emergency braking would therefore have to be initiated even if the bird subsequently does not continue its flight towards the danger zone.

[0088] However, if the safety speed is chosen so that an emergency stop is not necessary, the rotor speed can simply be reduced slightly in the latter case while the wind turbine continues to operate. If the bird then changes its flight path, the wind turbine remains at a stable operating point and can, moreover, easily increase the rotor speed again should the bird move further away from the danger zone.

[0089] According to one aspect, it is proposed that the rotor speed, the speed-distance function, the protection speed and / or the reaction range be selected depending on at least one of the following criteria.

[0090] One criterion is visibility in the vicinity of the wind turbine, particularly within the turbine's reaction zone. In poor visibility, it is possible that the endangered bird will not be detected in time. However, if it is detected in time, for example, by using appropriate technical equipment such as radar, it is possible that the bird will fly correspondingly slower.

[0091] Another criterion is agricultural activity in the vicinity of the wind turbine, particularly within a radius of up to 10 kilometers, and especially within a radius of up to 5 kilometers. This radius can therefore be a circle with a diameter of up to 20 kilometers, or up to 10 kilometers, around the wind turbine, with the turbine at its center. It has been observed that many birds follow agricultural activities such as harvesting or plowing because these activities disturb prey. Such agricultural activity thus influences the behavior of birds.

[0092] Another criterion is thermal activity in the vicinity of the wind turbine, particularly within a radius of up to 10 kilometers, and especially within a distance of 5 kilometers. Such thermal activity also influences the behavior of some bird species, as described above.

[0093] Another criterion is the preferred flight direction of the endangered bird. It is particularly relevant here that the endangered bird is a migratory bird, which therefore flies primarily in one direction and does not deviate from it, possibly depending on the time of day. If such a migratory bird—or, more often, many such migratory birds occur simultaneously—flies in its preferred flight direction and would not fly directly towards the wind turbine, it is unlikely that it would change course and reach the danger zone. Accordingly, measures can be taken, for example, by foregoing a reduction in rotor speed altogether or by choosing a smaller reduction.

[0094] Another criterion is the position of the wind turbine in relation to the habitat and / or hunting grounds of the endangered bird. Particular caution is required if the wind turbine is located between the habitat and the hunting grounds. If the wind turbine is not precisely between the habitat and the hunting grounds, but rather at the edge, it is not to be expected that the bird would take a detour via the wind turbine between these two areas.

[0095] Therefore, it is possible to select the rotor speed depending on visibility, agricultural activity, thermals, preferred flight direction and / or the position of the wind turbine.

[0096] It is also proposed to select the rotational speed-distance function depending on visibility, agricultural activity, thermals, preferred flight direction and / or the position of the wind turbine.

[0097] It is also proposed to select the guard rotation speed depending on visibility, agricultural activity, thermals, preferred flight direction and / or the position of the wind turbine.

[0098] It is also possible to select the reaction range depending on visibility, agricultural activity, thermals, preferred flight direction and / or the position of the wind turbine.

[0099] One aspect proposes that the behavior of endangered birds be recorded during the operation of the wind turbine, behavioral patterns be derived from the recorded behavior, particularly for each identified bird species, and the wind turbine be controlled based on the derived behavioral pattern. Specifically, the rotor speed, the speed-distance function, the guard speed, and / or the response range can be controlled based on the derived behavioral pattern.

[0100] Essentially, all the aforementioned criteria for bird behavior can be considered as recorded behavior. This includes the direction of flight, speed, and how much the birds change direction and / or speed. The direction from which they approach and the direction they are flying are also considered behavioral factors. Criteria such as time of day, season, and bird species can be included. Furthermore, the previously explained criteria such as visibility, agricultural activity, thermals, preferred flight direction, and the position of the wind turbine in relation to habitat and / or hunting grounds can be taken into account.

[0101] Behavioral patterns can be derived from this, for example, the time of day a bird moves between its habitat and hunting grounds. Another example is determining which flight paths a threatened bird of a particular species takes through the wind turbine's response area at different times of the year and / or day. All such behavioral patterns can be recorded, and the wind turbines can be controlled accordingly.For example, if a behavioral pattern has been recorded that a bird of a certain species, or perhaps even a specifically identifiable bird, always takes a certain flight path through the reaction area of ​​the wind turbine without ever coming close to the danger zone of the wind turbine, then it may be planned not to reduce the rotor speed, even if the endangered bird flies into the reaction area, which would normally lead to a reduction in rotor speed.

[0102] It should be noted that this does not necessarily mean that not reducing the rotor speed will endanger the bird should it exceptionally change its flight path towards the danger zone. It could also mean that it is still possible to reduce the rotor speed in time, albeit in the undesirable manner of an emergency stop. However, the risk of such an emergency stop can be accepted if, based on the inferred behavioral pattern, such a stop is highly unlikely and therefore extremely rare or perhaps never occurs.

[0103] According to one aspect, it is proposed that reductions in rotor speed be recorded, particularly with regard to number, amplitude and / or duration, and that a lifetime calculation of the wind turbine be carried out or adjusted depending on the recorded reductions.

[0104] The underlying principle here is that a wind turbine is designed for a certain lifespan. This lifespan can be reached, for example, after 20 years of typical operation. However, the lifespan depends heavily on the actual load. The 20-year lifespan of the wind turbine is based on an average load.

[0105] However, reducing the rotor speed, especially if this is not done as an emergency stop but rather in a continuous and gentle manner, can reduce the stress on the wind turbine. Such a reduction in rotor speed is initially undesirable because it results in less power generation and thus a lower yield. However, it has now been recognized that this reduction in rotor speed can also have the advantage of increasing the turbine's lifespan.

[0106] If these reductions in rotor speed are recorded and the turbine's lifespan can be reliably recalculated, the wind turbine can then be operated for a correspondingly longer period. While the annual yield of the wind turbine, which may have decreased due to the reduction in rotor speed, cannot be increased, some compensation can be achieved by allowing the wind turbine to operate for perhaps six months or a full year longer, during which time a yield can naturally be generated.

[0107] According to the invention, a wind turbine is also proposed which has a rotor with rotor blades adjustable in their blade angle and with a rotor diameter, wherein the rotor can be operated at a variable rotor speed, and an area in which the rotor blades move forms a danger zone for birds and bats, wherein the wind turbine is prepared to carry out a method comprising the following steps: Checking for a bird or bat approaching the wind turbine as a vulnerable bird, and, if a vulnerable bird has been detected, recording a bird position as the current position of the detected vulnerable bird and controlling the rotor speed depending on the bird position in relation to the wind turbine, reducing the rotor speed in several stages or continuously as the distance of the bird position to the wind turbine decreases.

[0108] The wind turbine is therefore equipped to carry out such a procedure. In particular, it has a suitable control unit on which the procedure steps can be implemented.

[0109] To detect endangered birds, which also includes bats, a bird detection device may be used. Such bird detection devices are generally known. They can detect birds or bats optically and / or via infrared and / or ultrasound and / or radar. This allows them to determine the bird's position. By recording several positions at different times, speed, direction, changes in speed, and changes in direction can be derived and thus detected. Furthermore, bird detection devices are being proposed that can also identify a bird species, including a bat or bat species. Such identification can be carried out particularly via the shape, flight behavior, including wingbeat frequency, as well as colors and other physical characteristics of the bird and, if necessary, also via the sounds of the bird or bat.

[0110] Such a bird detection device is in particular connected to the control unit, so that part of the evaluation and / or the derivation of a change in the control of the wind energy plant can be carried out on the control unit.

[0111] According to one aspect, it is therefore proposed that the wind turbine be equipped with a bird detection device for recording birds or bats, in particular by position and / or species. Recording by species thus means recording a bird species, which includes recording a bat species or even simply recognizing that the flying animal is a bat.

[0112] Furthermore, or alternatively, the wind turbine thus has a control device, and this control device can be prepared to execute a procedure according to one of the embodiments described above.

[0113] The invention will now be explained in more detail using exemplary embodiments and with reference to the accompanying figures. Figure 1 shows a wind turbine in a perspective view. Figure 2 shows various relevant areas around a wind turbine, illustrated by circles. Figure 3 shows a top view of a wind turbine to illustrate the possible shapes of areas around the wind turbine. Figure 4 shows a flowchart of a proposed procedure.

[0114] Figure 1 Figure 1 shows a wind turbine 100 with a tower 102 and a nacelle 104. A rotor 106 with three rotor blades 108, each with a blade root 109, and a spinner 110 is mounted on the nacelle 104. During operation, the wind sets the rotor 106 into rotation, thereby driving a generator in the nacelle 104.

[0115] A bird detection device 120, coupled to a control unit 122, is arranged on the nacelle 104 as an example. The control unit 122 is specifically designed to control the wind turbine, in particular its rotational speed, power output and / or torque, as well as the blade pitch of the rotor blades 108. For clarity, the control unit 122 is shown at the base of the tower, but it can also be located in the nacelle 104, namely near the bird detection device 120 and also near other actuators such as a blade pitch control device.

[0116] This arrangement is merely an example, and other configurations are possible. Tower mounting, i.e., mounting on the tower, as well as free-standing installation on a mast in a wind farm, for example, for high-performance radars or camera arrays, are preferred options. The sensors are preferably installed outside the rotor area to avoid hindering detection. These configurations differ from the one described in [reference missing]. Figure 1 depicted.

[0117] Connection to a park or wind energy system control system and power supply can then be made via an underground cable. The evaluation unit can, for example, also be located in a transfer station, a technical container, or a control room and connected to a SCADA infrastructure via a network.

[0118] The bird detection device 120 thus detects any birds or bats and can identify the species of bird or bat, determine their position, and track them in real time. This data is then transmitted to the control unit, which can adjust or modify the control of the wind turbine accordingly. The control unit 122 can also derive further information from the received data, such as flight direction and speed. In particular, the control unit 122, together with the bird detection device 120, is designed to carry out a procedure such as the one described in [reference to relevant document]. Figure 4 will be explained.

[0119] Figure 2 This illustrates a Wind Energy Plant 200, which can also be called WT, located in Figure 2 only forms the center of the areas explained below.

[0120] A circle with radius R min is drawn directly around wind turbine 200, illustrating a danger zone 202. This danger zone 202 is located directly around wind turbine 200, and its radius R min corresponds to the radius of the wind turbine's rotor, which is shown in Figure 2 but is not shown. Figure 1 Figure 1 shows a rotor 106, the radius of which can be used here. Preferably, the radius R min of the danger zone 202 is slightly larger than the radius of the wind turbine rotor, i.e., the aerodynamic rotor of the wind turbine. It can be, for example, 10% or 20% larger, or even 50% larger.

[0121] Danger zone 202 and also the other areas explained below. Figure 2 are represented as circles for simplicity's sake. Figure 3 A sensible deviation is explained further below.

[0122] It is now planned that the wind turbine 200 will be controlled in such a way as to ensure that its rotor speed is reduced to a protective speed before a bird or bat enters the danger zone 202.

[0123] The danger zone 202 is surrounded by the reaction zone 204. The reaction zone 204 is defined by the radius RRe. If a bird or bat reaches the reaction zone, it is proposed to react by reducing the rotor speed. This can be done gradually, or ideally continuously, depending on the distance to the danger zone 202. This is illustrated by the radius R1. R1 can thus be understood as the decision boundary beyond which the speed reduction is initiated. For the sake of simplicity, this radius R1, like the other radii, is referenced to the wind turbine 200 or to a center point of the wind turbine 200. The radius R1 can therefore vary between the radius Rmin, which defines the danger zone 202, and the radius RRe, which denotes the radius of the reaction zone 204. The circle with radius R1 is thus located within the reaction zone 204.Reference symbol 204 should therefore not indicate that the reaction area is within the circle with radius R 1, but rather that it extends to the circle with radius R Re .

[0124] According to one variant, the radius R 1 can mark a boundary of a danger zone.

[0125] Furthermore, a detection area 206 is illustrated. The detection area is thus defined by the outermost circle with the rotor radius RDet. Within this detection area 206, a bird detection device, such as the one shown in Figure 1 The bird detection device 120 shown can detect and identify a bird or bat. This allows a bird or bat to be detected before it reaches the reaction area 204 or the circle with radius R Re.

[0126] In the Figure 2 Several illustrative flight paths of an exemplary bird 208 are shown.

[0127] On the first flight route 211, bird 208 enters detection area 206. Bird 208 is then identified, and its position is continuously recorded. Additionally, it may be planned that, as a precaution, an initial reduction in rotational speed is initiated, during which the wind turbine changes its operating characteristic curve, i.e., its rotational speed-power curve or rotational speed-torque curve. This allows the rotational speed to be reduced without a significant reduction in the power output. Such a reduction in rotational speed without a significant reduction in power output is, of course, not arbitrarily possible, but it can be implemented depending on the operating situation. Power losses then only occur within the scope of the resulting deviation from the optimal operating point.

[0128] According to the first flight route 211, the bird, which here also represents a possible bat, does not reach reaction zone 204. Therefore, a reduction in engine speed would not be necessary, and the aforementioned reduction in engine speed by changing the operating characteristic curve is thus only an optional, precautionary measure.

[0129] On the second flight route 212, the bird not only flies into the detection area 206, but also into the reaction area 204. However, since the bird essentially flies past the wind turbine 200 at a great distance, it soon leaves the reaction area 204 again according to this second flight route 212, and also the detection area 206.

[0130] Nevertheless, the rotor speed is reduced as soon as the bird 208 enters the reaction area 204 on the second flight route, or as soon as the bird 208 reaches the circle with radius R Re.

[0131] However, it is only suggested to slightly reduce the rotor speed and observe the further flight path of bird 208. Here it leaves reaction zone 204 again, so the rotor speed can be increased back to the speed that was present before bird 208 reached reaction zone 204.

[0132] The third flight route 213 also shows the case in which the bird 208 flies into the detection area 206, then also into the reaction area 204, but then turns around and leaves the reaction area 204 and then also the detection area 206 again.

[0133] Here, the wind turbine can be controlled in a manner very similar to the example of the second flight route 212. The rotor speed is reduced as soon as the bird 208 reaches the reaction zone 204, and as the bird continues to approach the wind turbine 200 and thus the danger zone 202, the rotor speed can be gradually reduced further. The moment the bird changes direction according to the third flight route and flies further away from the wind turbine 200 and the danger zone 202, the rotor speed can be increased again.

[0134] One option proposes taking into account not only the bird's position, but also its flight direction and speed. This could lead to different behavior of the wind turbine depending on the second and third flight routes.

[0135] On the second flight route 212, it is evident from the direction of flight that the bird is not flying towards the wind turbine 200 or the danger zone 202, so that even with the same distance between the bird's position and the danger zone 202, a smaller reduction in rotor speed may be appropriate.

[0136] Instead, following the third flight path, the bird flies almost directly towards danger zone 202, so it is initially expected that the bird will soon reach danger zone 202. The time it would take to reach the danger zone can be calculated or at least estimated, and within this time, the rotor speed must be able to be reduced to a protective speed. Therefore, the rotor speed is reduced more the closer bird 208 gets to danger zone 202.

[0137] The moment the bird essentially turns away and moves off again according to the third flight route 213, the rotor speed can be increased again.

[0138] Finally, a fourth flight route, 214, is shown, which essentially represents the most dangerous situation for bird 208. Bird 208 flies directly towards wind turbine 200 and thus into danger zone 202, and actually reaches danger zone 202. For clarity only, the dashed arrow illustrating the fourth flight route, 214, ends before danger zone 202. However, this example assumes that the bird flies right into the danger zone and that the rotor speed is controlled, specifically the reduction of the rotor speed, so that it is reduced to the safety speed shortly before bird 208 reaches danger zone 202.

[0139] The wind turbine can then continue to operate at the protective speed as long as the bird remains within the danger zone. Once it moves away, the rotor speed can be increased again. However, if the bird (208) moves away in such a way that it remains within the reaction zone (204), the rotor speed can be further increased depending on its position, i.e., its distance from the danger zone, but not to the speed that was present before the bird entered the reaction zone (204).

[0140] The wind turbine continues to operate, albeit at a fluctuating speed, which is lower than if the bird were outside the reaction zone (alternatively, the wind turbine, which can be abbreviated as WTG, could be shut down despite the pre-reduced speed as soon as it is predicted that the bird is very likely to fly into the danger zone). However, as soon as the bird were to leave the reaction zone again in this example, the wind turbine would resume normal rotor speed. Due to the continuous adjustment of the rotor speed based on the bird's position, it is also easily possible to immediately resume normal rotor speed as soon as the bird has left reaction zone 204.

[0141] The fourth flight route illustrates a further variant, namely when a pre-flight zone is defined and the radius R1 marks the boundary of this zone. In this case, upon reaching the reaction zone, the rotor speed is initially reduced to a reaction speed. However, the aircraft continues flying and reaches the boundary of the pre-flight zone, marked by R1, which leads to a further reduction step where the rotor speed is reduced to the protection speed.

[0142] Figure 3 Figure 300 schematically shows a top view of a wind turbine 300 with rotor blades 308, which define a rotor 306. It was recognized here that an indicated danger zone 302, unlike the illustration in Figure 306, is not actually a wind turbine 300. Figure 2 shown, adapted to rotor 306, and therefore not circular, as in the illustrated example for danger zone 202 in the Figure 2 .

[0143] Thus, a bird approaching the wind turbine 300 in a longitudinal flight direction FL can get closer before reaching the danger zone 302 than would be the case with a transverse flight direction FQ.

[0144] Accordingly, this, and thus the orientation of the wind turbine 300, can be taken into account when controlling the rotor speed depending on the bird's position.

[0145] The reaction area, shown here as reaction area 304, can also be adjusted accordingly. Reaction area 304 has a boundary 305, which is also not circular, but rather oval or elliptical in shape.

[0146] The in Figure 2 The detection area shown, 206, can of course still be circular, as this depends on the range of the bird detection device (see bird detection device 220 of the Figure 1) and ideally, it should have the same range in all directions. However, it is particularly important to consider that, depending on weather conditions, the range of such a bird detection device may not necessarily be the same in all directions.

[0147] Figure 4 Figure 400 illustrates a flowchart of a proposed method for controlling a wind turbine depending on a detected bird or bat.

[0148] The process begins with the detection of a bird according to detection step 402. Detection step 402 attempts to identify a bird. Here, too, the bird also serves as a representative for a bat. Detection step 402 is essentially performed continuously by a bird detection device. In other words, such a bird detection device is constantly searching for birds, or endangered birds.

[0149] In query step 404, the system essentially checks continuously whether a relevant bird has been detected. If not, the loop returns to detection step 402, which is only meant to illustrate that the search for a bird is constantly repeated.

[0150] However, if a bird is detected, the process continues with identification step 406. Detection according to detection step 402 is, of course, continued in parallel to check whether other birds are approaching.

[0151] In identification step 406, the type of bird is first specified. The type can also be referred to synonymously as species.

[0152] After the bird species has been identified in identification step 406, a parameterization is performed in parameterization step 408, depending on this. For this purpose, the reaction range (see reaction range 204 of the Figure 2 and reaction area 304 of the Figure 3The reaction zone is defined. In particular, the distance of the edge of the reaction zone from a danger zone or from the wind turbine is specified. The speed of the bird in question is a key factor here, as it determines how early any necessary reduction in rotational speed must occur. If the identified bird can fly very fast, a larger reaction zone must be defined; otherwise, it can be smaller.

[0153] Furthermore, a function, which will be explained later and which adjusts the rotor speed depending on the position of the bird, can be parameterized depending on the identified bird species.

[0154] The next step, position step 410, involves determining the bird's position. This position can be detected using the bird detection device and can therefore also be recorded in detection step 402. Position step 410 emphasizes that this explicit determination of the bird's position is a crucial element and must be continuously updated.

[0155] Based on the position thus detected, a comparison is made in comparison step 412 between the detected position and the reaction area. In other words, it is checked whether the bird's position has reached the reaction area or not.

[0156] This is evaluated in evaluation step 414. If the bird has not (yet) reached the reaction zone, the procedure proceeds to characteristic curve change step 416. In characteristic curve change step 416, an operating characteristic curve is changed from a normal characteristic curve, which is symbolized there as the speed-power normal characteristic curve nPN, to a reduced operating characteristic curve, namely a bird protection characteristic curve, which is symbolized as the reduced speed-power characteristic curve nPR.

[0157] This selects an operating mode with reduced speed, but with only a slight reduction in power. However, such a characteristic curve change step 416 can also be omitted, especially if this is not possible or not stable due to boundary conditions.

[0158] In any case, the procedure then returns to position step 410. This would also happen if the characteristic curve change step 416 were omitted.

[0159] The return to position step 410 is meant to symbolize that the bird's position will continue to be recorded, especially continuously.

[0160] If, in evaluation step 414, it is determined that the bird has entered the reaction zone, the process proceeds to speed adjustment step 418. In speed adjustment step 418, the rotor speed is then adjusted depending on the bird's position. This is illustrated by the equation n=f(Pos). The rotor speed is continuously adjusted as a function of the bird's position. Initially, this means that the rotor speed is reduced when the bird has just entered the reaction zone. However, it can also mean that when the bird moves away from the wind turbine, the rotor speed is increased again.

[0161] The function used depends on the bird species, i.e., the specific bird classification. This is indicated by [Spe]. The function symbolically represented in speed setting step 418 is the one that was set according to parameterization step 408. In other words, this position-dependent speed function was parameterized according to parameterization step 408 based on the detected bird species.

[0162] In particular, such parameterization can mean, depending on the bird species, that the rotor speed n to be set is lower for the same bird position, i.e., the same distance, the faster the bird is according to the identified species.

[0163] After this speed adjustment step 418, a loop returns to position step 410, where the position is continuously recorded and updated. Accordingly, the rotor speed can also be continuously adjusted according to speed adjustment step 418. However, if the bird moves away again, especially if it leaves the reaction area, this is also detected in evaluation step 414, and speed adjustment step 418 is no longer triggered. In this case, the rotor speed is already at its normal value, as it was set to this value the moment the bird reached the edge of the reaction area, in this case from the inside.

[0164] For the sake of clarity, the flowchart 400 no longer includes the fact that only the loop consisting of detection step 402 and query step 404 is executed if the detected bird is even outside the detection range of the bird detection device.

[0165] Within the scope of the invention, the following aspects in particular were identified or are proposed.

[0166] Bird detection systems have a defined range within which they can detect relevant birds. This is specified in Figure 2 denoted by R Det.

[0167] It was recognized that the radius Rmax, which a bird must fall below to enter the reaction zone, depends on the species-specific flight speed or actual flight speed and the time it takes for the wind turbine, sometimes also called a wind power plant, to reach spin mode. This can be expressed by the following formula: R max = v Art ⋅ t trudel + D / 2 in it is v Art the species-specific flight speed t trudel The time until the rotor D slows down / is stopped, the rotor diameter of the system R max also denotes the outer edge of the reaction area and can correspond to the radius R RE of the reaction area 204 described above.

[0168] Previously, it was known to initiate a shutdown of the system upon detection of an endangered bird, particularly with the following steps: The braking process is initiated as soon as the distance between the bird and the wind turbine is less than R max and the wind turbine stops completely.

[0169] Once the bird reaches R min, the leaf tip speed must be less than 30 km / h (8.3 m / s), for example. This is a good example for a red kite, and different values ​​apply to other bird species. R min represents the inner edge of the reaction zone and the outer edge of the danger zone.

[0170] Once initiated, a system shutdown cannot be reversed or aborted during the shutdown process. The wind turbine reduces its rotational speed until it stops and is disconnected from the grid, with corresponding waiting periods before it can be restarted.

[0171] However, the following problem was identified: Birds rarely fly all the way to the wind turbine, but instead turn around within its reaction area and then leave again. The wind turbine still completes the stop fully, meaning that approximately 97% of the stops would be unnecessary.

[0172] To resolve this, an operating mode to prevent system shutdowns is proposed. Specifically, the following is suggested: Instead of initiating a shutdown, a specific operating mode should be selected upon bird detection.

[0173] The operating mode is characterized by the ability to automatically switch back, ideally without delay, from a bird protection mode (which can be termed "OM Species Protection") to the original mode, i.e., a normal mode. Such a normal mode may consist, in particular, of using a standard characteristic curve as the operating characteristic curve and / or not reducing the rotor speed.

[0174] This can prevent downtime and increased loads caused by the stop.

[0175] The direction from which the bird is approaching should preferably be included, so that in the aforementioned formula (4-1) ( R max = v Art · t trudel + D / 2) D = 0, or D approximately 0, applies when the bird flies lengthwise (with or against the wind) towards the wind turbine. This is in Figure 3 illustrated.

[0176] Among other things, two different operating modes are proposed as alternatives: These involve a reduction of R max and R min when a shorter time is reached. t trudel This is based on a fundamental idea. This can be achieved by changing physical properties (inertia, reaction time, pitch speed, etc.) or by using an adapted operating mode.

[0177] As option a), the following is proposed: As soon as a bird enters the reaction zone, the blade tip speed is reduced to a non-critical value (species-specific, in the range of 50-120 km / h or 13.8 m / s to 33.3 m / s), but at least to the cut-in speed. If the bird enters the danger zone, the system switches to a spin mode, which specifies a minimum speed but does not trigger the stop status. In particular, the final braking process occurs with less load and faster than a system stop from nominal speed.

[0178] As variant b), the following is proposed: As soon as a bird enters the reaction zone, the blade tip speed is continuously reduced depending on the bird's distance, i.e., its position relative to the danger zone. If a bird falls below the maximum distance Rmax to the wind turbine and flies towards it at full speed, the wind turbine has a maximum time of t trudel = R max − R min / v Art to achieve a non-critical rotor blade tip speed. From this, and from the first derivative of the relationship between angular position and rotational acceleration, the maximum required rotor acceleration is calculated. α min . ϕ = 1 / 2 ⋅ α ⋅ t 2 + ω nenn ⋅ t + ϕ 0 dϕ / dt = α ⋅ t + ω nenn α min = dϕ / dt − ω nenn / t

[0179] It contains ϕ 0 , ϕ the angular position of the rotor at the beginning / after time t ω name the nominal angular velocity dϕ / dtthe target angular velocity that the wind turbine will reach after a certain period of time t trudel has supposedly achieved α min the necessary (negative) acceleration of the rotor.

[0180] Formula (4-5) yields a characteristic curve with which the rotational speed is successively reduced. Accordingly, the achievable rotational speed depends on... dϕ / dt from the distance of the bird RV to the wind turbine: dϕ / dt = R max − R v ⋅ α min / v Art + ω nenn

[0181] The distance of the bird R v can be determined by the radius R 1 of the Figure 2 This will be illustrated.

[0182] Depending on the quality of the bird detection system or bird detection device and the interface to the system control, it is possible v Art The current flight speed of the bird can be replaced. Alternatively, the maximum flight speed or another typical flight speed of the identified bird species can be used.

[0183] If a rotor can achieve a higher acceleration due to its physical properties, the reaction distance can be reduced via the reverse approach, thus allowing the performance-optimized operation, which can also be referred to as normal operation, to be applied for a longer period of time.

[0184] Combinations of variants a) and b) are possible, for example as follows: Between R max and R 1, stepless control is implemented; between R 1 and R min, a constantly low minimum rotational speed is implemented and / or, at a distance, i.e., a bird position with a distance to the wind turbine of less than R min, a tumbling motion occurs.

[0185] The proposed aspects are suitable for a Operation of the wind turbine at sites with bird protection requirements and an installed bird detection system, and operation of the wind turbine at sites with bat activity, where the wind turbine has previously been shut down on the condition that a detection system is installed.

[0186] The proposed aspects are particularly intended for the following areas: the construction and operation of wind energy plants at locations where approval would not be granted for species protection reasons, or at locations where plant operation would become uneconomical due to high shutdown requirements or downtime.

[0187] Reduction of downtime of the wind turbine when birds approach, and thus Reduction of loads by avoiding frequent stops, reduction of yield losses or increase in the availability of the plant, and faster start-up capability of the wind turbine to reach rated power again.

[0188] The following solutions can be achieved with the proposed aspects: Reduction of wind turbine downtime; reduction of load cycles caused by additional turbine stops and starts; increased start capability as soon as the bird leaves the danger / response area; reversal of the wind turbine braking process should the bird leave the reaction area without entering the danger zone.

Claims

1. Method for controlling a wind power installation which has a rotor having rotor blades that are adjustable in terms of their blade angle, and having a rotor diameter, wherein the rotor is able to be operated at a variable rotor rotating speed; and a region in which the rotor blades move forms a danger zone for birds and bats, the method comprising the following steps: - checking whether a bird or bat approaching the wind power installation is an endangered bird; and if an endangered bird has been identified - detecting a bird position as the current position of the endangered bird identified; and - controlling the rotor rotating speed as a function of the bird position in relation to the wind power installation; wherein - the rotor rotating speed is reduced in multiple stages or continuously as the distance of the bird position from the wind power installation decreases, characterized in that - the rotor rotating speed is predefined according to a rotating speed / distance function, wherein the rotating speed / distance function defines a rotating speed as a function of a distance of the endangered bird from the danger zone.

2. Method according to Claim 1, characterized in that - the bird species or another category of the endangered bird is identified; - a response region about the wind power installation is established as a function of the identified bird species or other category, wherein the response region has a regional periphery and the response region is defined in that the wind power installation can reduce the rotor rotating speed to a coasting rotating speed, a protective rotating speed, or to zero, before it is to be anticipated that the endangered bird of the bird species identified reaches the danger zone from the periphery of the response region; - the rotor rotating speed is reduced as soon as the endangered bird flies into the response region; and - the rotor rotating speed is reduced further the closer the endangered bird gets to the danger zone, without the wind power installation being shut down or stopped.

3. Method according to Claim 1 or 2, characterized in that - a number of birds or bats approaching the wind power installation is identified as the number of endangered birds; and - the controlling of the wind power installation, in particular the controlling of the rotor rotating speed, is carried out as a function of the number of endangered birds identified.

4. Method according to one of the preceding claims, characterized in that - the rotor rotating speed and / or the rotating speed / distance function is set or selected as a function of - a season; - a time of day; and / or - a or the bird species identified.

5. Method according to one of the preceding claims, characterized in that - the rotor rotating speed is increased again when the endangered bird removes itself from the danger zone and is still situated in the response region.

6. Method according to one of the preceding claims, characterized in that - the wind power installation is operated at a protective rotating speed and generates output as long as the endangered bird is situated in the danger zone, wherein - the protective rotating speed is a rotor rotating speed which is considered to pose no risk to the endangered bird when the latter is in the danger zone; and wherein in particular - the protective rotating speed is established as a function of the bird species identified.

7. Method according to one of the preceding claims, characterized in that - the rotor rotating speed is reduced to a or the protective rotating speed which is considered to pose no risk to the endangered bird when the endangered bird flies into a or the response region; - the rotor rotating speed is reduced further to zero or to a coasting rotating speed when the endangered bird flies into a reduced preliminary danger zone which has a zone boundary that lies within the response region but outside the danger zone; and - the wind power installation continues to be operated at this protective rotating speed and in particular generates power in the process until the bird reaches the preliminary danger zone; wherein in particular - the response rotating speed and / or the protective rotating speed are / is predefined as a function of the bird species of the endangered bird.

8. Method according to one of the preceding claims, characterized in that - the wind power installation, as long as the latter is not operated at the nominal rotating speed and the nominal output, is operated using an operational characteristic curve in which an electrical output to be set, or a generator torque to be set, is predefined as a function of the rotor rotating speed; wherein - a normal characteristic curve is used as the operational characteristic curve when no endangered bird approaching the wind power installation has been identified; and - a bird-protecting characteristic curve which in comparison to the normal characteristic curve has higher output values or generator torque values at respectively identical rotor rotating speed values is used as the operational characteristic curve when - an endangered bird approaching the wind power installation has been identified; - an endangered bird has been identified in a region outside a or the response region; and / or when - there is a high, in particular higher-than-average, probability that an endangered bird flies into the response region; wherein preferably - the response region is set as a function of the bird-protecting characteristic curve.

9. Method according to one of the preceding claims, characterized in that - the rotor rotating speed, when an endangered bird approaching the wind power installation has been identified, - is reduced by increasing the generator torque; and / or - is reduced by adjusting the blade angles of the rotor blades.

10. Method according to one of the preceding claims, characterized in that - the reduction of the rotor rotating speed is set as a function of - a detected flying speed of the endangered bird identified; and / or - a typical, in particular maximum, flying speed of the bird species of the endangered bird identified; and / or - a detected direction of flight of the endangered bird identified; and / or - an estimated minimum approach time which the endangered bird identified is anticipated to at least need to reach the danger zone from the current position of said bird.

11. Method according to one of the preceding claims, characterized in that - the wind power installation is operated at a variable safe rotating speed which defines a rotating speed that is continually adapted to the current bird position; wherein - the safe rotating speed is chosen such that the rotor rotating speed, proceeding from the safe rotating speed, can be reduced to the protective rotating speed or a coasting rotating speed in the time which the endangered bird is anticipated to need from the current bird position thereof at least to the danger zone; wherein in particular - the safe rotating speed is chosen such that the reduction of the rotor rotating speed from the safe rotating speed to the protective rotating speed or the coasting rotating speed is ensured without emergency braking and with continued operation and continued output generation.

12. Method according to one of the preceding claims, characterized in that - the rotor rotating speed; - a or the rotating speed / distance function; - a or the protective rotating speed; and / or - a or the response region, are / is selected as a function of at least one criterion from the list comprising - a visibility range in the environment of the wind power installation, in particular in the response region of the wind power installation; - an agricultural activity in the environment of the wind power installation, in particular in a range of up to 10 km, in particular up to 5 km, from the wind power installation; - a thermal in the environment of the wind power installation, in particular in a range of up to 10 km, in particular up to 5 km, from the wind power installation; - a preferred direction of flight of the endangered bird; and - a position of the wind power installation in relation to a habitat and / or a hunting ground of the endangered bird.

13. Method according to one of the preceding claims, characterized in that - behaviours of endangered birds are recorded in the operation of the wind power installation; - behavioural patterns are derived from the recorded behaviours, in particular for a respective bird species identified; and - the wind power installation, in particular - the rotor rotating speed; - a or the rotating speed / distance function; - a or the protective rotating speed; and / or - a or the response region, are / is controlled as a function of the derived behavioural pattern.

14. Method according to one of the preceding claims, characterized in that - reductions of the rotor rotating speed are recorded, in particular according to number, amplitude and / or duration; and - a service life computation for the wind power installation is carried out or adapted as a function of the recorded reductions.

15. Wind power installation which has a rotor having rotor blades that are adjustable in terms of their blade angle, and having a rotor diameter, wherein the rotor is able to be operated at a variable rotor rotating speed; and a region in which the rotor blades move forms a danger zone for birds and bats, wherein the wind power installation is prepared to carry out a method comprising the following steps: - checking whether a bird or bat approaching the wind power installation is an endangered bird; and if an endangered bird has been identified - detecting a bird position as the current position of the endangered bird identified; and - controlling the rotor rotating speed as a function of the bird position in relation to the wind power installation; wherein - the rotor rotating speed is reduced in multiple stages or continuously as the distance of the bird position from the wind power installation is reduced, characterized in that - the rotor rotating speed is predefined according to a rotating speed / distance function, wherein the rotating speed / distance function defines a rotating speed as a function of a distance of the endangered bird from the danger zone.

16. Wind power installation according to Claim 15, characterized in that - said wind power installation has a bird detection installation for detecting a bird or a bat, in particular according to the position and / or species; and / or that - the wind power installation, which to this end has in particular a control installation, is prepared to carry out a method according to one of Claims 1 to 14.