METHOD FOR OPERATING A WIND TURBINE WITH INCREASED POWER

Description

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

[0002] Wind turbines are known for generating electrical power from wind. If the wind speed is below a nominal wind speed, the turbine operates in partial load mode. During this partial load mode, the turbine attempts to operate optimally, extracting as much power from the wind as possible.

[0003] However, if the wind speed reaches the nominal wind speed and even rises above it, full load operation occurs and the wind turbine is operated in such a way that overloading is avoided, which could otherwise lead to damage to the wind turbine and / or reduce its service life. For this purpose, the wind turbine is designed to operate at a nominal speed and a nominal power from the nominal wind speed. The speed is thus limited to the nominal speed and the power is limited to the nominal power. The speed can also be referred to synonymously as the rotor speed. The power here can refer to the generator power delivered by the generator or the system power specified by the wind turbine. Especially for stationary operation, these two power outputs are essentially the same and differ only in power loss.In the following, it is sufficient to consider one of these two services.

[0004] In order to further increase the yield of the wind turbine, it would be desirable to be able to generate slightly more power than the rated power when there is sufficient wind.

[0005] The underlying idea here is that although the wind turbine is designed for its rated power and rated speed, this design may be based on assumptions that are subject to change. In particular, the temperature of components is a limiting factor. If components overheat, they and thus the wind turbine may be damaged, or the service life of the wind turbine may be reduced. Therefore, increasing the turbine output above its rated power may be considered, provided that temperature limits are not exceeded. It is particularly conceivable that the output may be increased above its rated power when outside temperatures are low, so that the components are cooled more effectively overall.

[0006] However, components can also be damaged for reasons other than overheating, and not every component can be monitored for temperature. Operating the wind turbine at a higher power output than rated and / or at a higher speed than rated is therefore a risk that should be avoided or reduced.

[0007] A method for operating a wind turbine above a rated power is disclosed in US 2018 / 171978 A1. The present invention is therefore based on the object of addressing at least one of the aforementioned problems. In particular, a solution is to be proposed in which the yield of the wind turbine can be increased. In particular, a solution is to be proposed in which the wind turbine can be operated at a higher power than the rated power without risking damage or an undesirable reduction in the operating time of the wind turbine.

[0008] According to the invention, a method according to claim 1 is proposed. Thus, a method is proposed for controlling a wind turbine with an aerodynamic rotor operable at a variable speed, with rotor blades adjustable in their blade angle, and with a generator for generating generator power, wherein the wind turbine is characterized by a rated speed, a rated power, and a rated wind speed at which the rated speed and the rated power are reached. The speed of the aerodynamic rotor can also be referred to as the rotor speed. During partial load operation, the speed and power increase depending on the wind speed until they have reached the rated speed and rated power at the rated wind speed.

[0009] It is now proposed that for wind speeds above the nominal wind speed, the wind turbine be operated at a power output above the nominal power. The power output is then an additional power above the nominal power. Power specifically refers to a system power output for which the nominal power is also intended. The power is then an additional power above the nominal power. However, the generator power can also be used as a basis, which can be slightly below the system power, whereby the generator can accordingly be characterized by a generator nominal power that is correspondingly slightly below the nominal power, i.e. the nominal power of the wind turbine, i.e. the nominal power of the system power. In any case, the aim is that whichever of the two is considered, the power output is an additional power above the applicable nominal power by the amount of the additional power.

[0010] The wind turbine is therefore operated at a higher power output than intended. However, the wind turbine is operated in such a way that the impact torque remains below a predetermined limit torque. Furthermore, it is intended that the current power loss does not exceed a predetermined power loss limit. The impact torque, which can also be referred to as the blade impact torque, refers to a torque at the blade root of the rotor blade in question, which is basically directed towards the pressure side of the rotor blade, i.e. perpendicular to the blade chord. At a blade angle of 0°, it is directed in the axial direction of the rotor axis; at a blade angle of 90°, it is directed in the direction of rotation of the rotor. In other words, this is a force that the wind exerts on the rotor blade in the specified direction. This force can be distributed across the rotor blade and leads to a bending moment at the blade root, where the blade is attached to a rotor hub, which creates this impact torque.This bending moment, or impact moment, can also be considered a torque, although no rotation occurs in this direction because the rotor blade is firmly connected to the hub there. To put it simply, the impact moment leads to a bending moment acting on the rotor axis. The effect of the impact moment on the rotor axis depends on the blade angle.

[0011] It was particularly recognized here that this mechanical load is an important factor that needs to be limited when the turbine is operated at a power output above the rated power. It was also recognized here that this impact torque, and its effect, i.e. the bending in the direction of the rotor axis, depends to a large extent on the current blade angle. This impact torque can be maximum at rated wind speed because at rated wind speed there is a comparatively strong wind, namely rated wind, while the rotor blades, and therefore each individual rotor blade in question, are not yet turned out of the wind. Only as the wind speed increases, i.e. above the rated wind speed, are the rotor blades turned out of the wind. This reduces the load on the blades in the direction of the rotor axis.

[0012] It was therefore recognized that a thermal analysis cannot reflect this situation. If the wind speed continues to increase, this impact torque can be reduced by rotating the rotor blades out of the wind. However, this does not reduce other loads on the wind turbine. Particularly when the wind turbine is operating at or above rated power, the thermal load depends primarily on the power generated. The change in impact torque and thus the directly related mechanical load can hardly be derived from the temperature of the components.

[0013] However, power generation also results in power loss, and this should not exceed a predetermined power loss limit. Considering power loss also includes ensuring that excessive thermal loads do not occur. If the power is increased above the rated power, power loss also increases. Power loss is therefore an indicator of the electrical power and thus the electrical load on the wind turbine. The thermal load on the wind turbine can also be indirectly assessed via power loss. Considering power loss allows for an overall assessment of the thermal load, rather than a selective assessment of individual thermal loads through temperature monitoring of components.

[0014] These suggestions allow the wind turbine to be operated continuously above its rated power, as long as the verified criteria are met. Care must therefore be taken to keep the impact torque below a predetermined limit and to prevent the current power loss from exceeding a predetermined power loss limit. This makes it possible to increase yield without shortening or significantly reducing the service life, and especially without causing damage to the wind turbine.

[0015] According to one aspect, it is proposed that, provided the wind speed is sufficiently high, the wind turbine is operated continuously at a power above the nominal power, in particular over a period of at least 10 minutes, in particular at least one hour. Additionally or alternatively, it is proposed that the increased power be at least 1% of the nominal power, preferably at least 5% and in particular at least 8%. An increase of 1% is already considered significant, considering the high investment costs. If the wind turbine is operated with just 1% more nominal power, this would correspond to an additional hour in four days. Preferably, however, the increased power is at least 5% higher than the nominal power. With a typical operating time of 20 years, this would mathematically correspond to an additional year of operation.In particular, it is proposed that the boost power be at least 8% of the rated power. It has been recognized that even an 8% increase is possible if the impact load is not excessive and the power loss is not excessive, i.e., both of these limits are met.

[0016] In particular, it was recognized that not only a very short-term increase, which could be considered, for example, to support a grid demand, is possible, but also a longer-term increase lasting at least 10 minutes, and in particular, even more than an hour. Of course, this always requires sufficient wind. Thus, yield can be significantly increased through such a permanent, or at least long-term, increase in power.

[0017] According to one aspect, it is proposed that while the wind turbine is operating at a power above the rated power, the speed be regulated to the rated speed. Here, it was particularly recognized that even a very high speed can place a strain on the wind turbine, but that operation at increased power is also possible without increasing the speed. Strains that can occur due to a high speed are taken into account by ensuring that the speed does not rise above the rated speed.

[0018] According to one aspect, it is proposed that when operating the wind turbine with a power above the rated power, the power loss limit is determined as a function of a cooling power, wherein in particular the cooling power is estimated or calculated using a calculation rule and / or the cooling power for the generator and / or for other electrical components, in particular an electrical drive train, is determined.

[0019] The cooling capacity provides information about the thermal load exerted on components. This particularly applies to the cooling capacity that must be actively generated to cool components, e.g., by fans or circulation pumps in liquid, particularly water, cooling systems. If such cooling capacity increases, it is recommended to reduce the power loss limit. On the one hand, this can prevent excessive thermal load from occurring at the same power loss. On the other hand, there is also the risk that operating the wind turbine at increased power will result in an increase in the power required for active cooling, to the point where this required cooling capacity matches or even exceeds the power additionally generated by the increased power.

[0020] The cooling capacity can be estimated overall or calculated using a calculation rule. The key here is that the power used for cooling, such as the power consumption of a fan, does not necessarily have to be taken into account; rather, the cooling capacity can be read off from other values. For example, when cooling with a cooling medium, the temperature of the cooling medium before it reaches the component to be cooled can be compared with the temperature that this cooling medium has after it has passed the component to be cooled. Together with the volume of the flow of this cooling medium, a good conclusion can then be drawn about the cooling capacity. An estimate can be used here, for example by using a state observer, or direct calculation rules can be applied, which, for example,Based on the above example, the cooling capacity can be calculated directly from the two temperatures of the cooling medium and its volume flow.

[0021] Additionally or alternatively, it is proposed that the cooling capacity be determined for the generator. The generator may be the element of the wind turbine that generates the most power loss. If the cooling capacity is therefore determined for the generator, this often determines the largest proportion of the cooling capacity. Furthermore, calculations and estimates of cooling capacity based on the element that requires the most cooling capacity are the least susceptible to failure. From the cooling capacity for the generator, for example based on empirical values ​​or pre-recorded reference tables, the overall cooling capacity can be deduced, i.e. by including other elements that require cooling capacity. Information on such elements, e.g. temperature or power consumption of an electrical component of an inverter, can be stored in the reference table.

[0022] In addition, or in addition, it is suggested that other components be considered for which the cooling capacity is determined. This can improve the result. In particular, it is suggested that electrical components of an electrical drive train be considered. The electrical drive train refers to everything that is electrically present from the generator to the feed-in point, i.e., through which current flows. This includes, in particular, a rectifier, an inverter, and the cables connecting these two elements. A line choke, provided it is not considered an element of the inverter, can also be added, as can a transformer if it is part of the wind turbine.

[0023] Power losses also occur here. The rectifier and / or inverter, in particular, may have active cooling, especially with a fan. Based on this, the respective cooling capacity can be determined. A connecting cable is not usually actively cooled, but it can still provide information about the power losses that occur in such a connecting cable. It is also generally possible to consider a small portion of the cooling capacity for the cable. The cable can dissipate heat and may indirectly contribute to cooling capacity by cooling the interior of the wind turbine, to which it dissipates the heat.

[0024] According to one aspect, it is proposed that the operation of the wind turbine with a power above the rated power is carried out in such a way, in particular the boosted power is selected such that a generator torque does not exceed a predeterminable generator limit torque, and / or the generator torque is set such that the generator limit torque is not exceeded, and in particular the generator limit torque is set depending on operating settings and / or ambient conditions.

[0025] It was particularly recognized here that torque can also be a limiting factor and can be particularly critical. At rated speed, which should ideally be maintained, power above the rated power is only possible with a generator torque above the rated torque. Therefore, the generator torque is generally set to a very high value. In principle, the generator can also be operated with a generator torque above the rated torque, and taking thermal values ​​into account prevents damage to the generator.

[0026] However, it was recognized here that additional generator protection or explicit consideration of the generator torque increases protection against overloads. In particular, it was recognized that a load problem can arise from a generator alternating load. A high generator alternating load can arise if the system must be suddenly shut down while operating above rated power. In this case, the aerodynamic torque can be reduced to a maximum, so that the generator and thus the aerodynamic rotor are braked to a maximum. This can lead to high loads, e.g., mechanical vibrations, on the system, which are even higher because the braking generator torque exceeds the rated torque.

[0027] High generator cycling loads can also occur, especially when generator power must be reduced suddenly. In this case, the generator torque can drop to zero, so that the aerodynamic torque suddenly no longer has any counter-torque, which can lead to severe mechanical stress on the rotor and, particularly due to vibrations, to further mechanical stress on the wind turbine.

[0028] Therefore, it is particularly recommended to adjust the maximum generator torque depending on operating settings and / or ambient conditions. These could be settings for grid support, for example, which provide for a rapid response to a grid fault. This makes it possible to determine whether a rapid power reduction is to be expected. Ambient conditions such as rain, temperature, and storm conditions allow conclusions to be drawn as to whether a turbine shutdown is to be expected to prevent a bird and / or bat collision.

[0029] According to one aspect, it is proposed that when operating the wind turbine at a power above the rated power, the power loss is kept constant, in particular at the value of the power loss limit. Furthermore, or alternatively, it is proposed that the power loss limit be determined as a power loss dependent on the speed.

[0030] This is based on the knowledge and assumption that the monitored impact torque remains below the preset torque limit. This is therefore continuously monitored, and as long as this is the case, the wind turbine can be controlled or regulated to a constant power loss value. In particular, the wind turbine can be controlled or regulated so that the power loss corresponds to the power loss limit. In other words, the power loss is then regulated to the value of the power loss limit.

[0031] This allows for maximum performance increase. It has been recognized that, especially at wind speeds only slightly above the rated wind speed, the impact load, i.e., the impact torque, can be very high and can be the limiting factor. However, as wind speeds continue to increase, the blades are gradually turned out of the wind, reducing the impact torque. Especially then, the power loss can become the limiting factor. The turbine can then be regulated to the power loss limit.

[0032] In particular, it is proposed that the power loss limit be determined as a power loss dependent on the speed. Preferably, the speed will constantly remain at the value of the rated speed at high power, i.e. when the power is increased above the rated power. Nevertheless, it is also sensible to determine the power loss limit as a function of the speed because, although the speed is essentially known and predictable, it is still present as a variable in the system control. The control method can therefore consider this speed as an input variable. Although the speed may be known, it has a major influence on the power loss and also on the system load in general, so that it can be an important variable for determining the power loss limit. Furthermore, it may still happen that the speed does not necessarily or always correspond to the rated speed, even with the proposed power increase.

[0033] In particular, the power loss limit can be determined depending on several variables, especially the cooling capacity and the speed simultaneously. In this case, even if the speed remains constant at the rated speed, the power loss limit can still vary, namely due to variations in the cooling capacity.

[0034] In addition or alternatively, it is proposed that the power loss limit is determined as a function of at least one of the variables wind speed, outside temperature, rotational speed, air pressure and air density and in addition or alternatively the power loss limit is specified as a function of an aging profile of the wind turbine, in particular as a power loss profile and / or as a function of a residual dielectric strength.

[0035] Determining the power loss limit as a function of wind speed is based on the realization that wind speed itself leads to different cooling effects. At the same outside temperature but stronger wind, greater cooling occurs than at the same outside temperature but with less wind. Accordingly, the power loss limit can be set higher at higher wind speeds, because the wind itself dissipates more power.

[0036] Likewise, a lower outside temperature can allow a higher power loss limit because in this case, too, a higher power loss dissipation can be achieved due to the low outside temperature.

[0037] Air pressure and / or air density can also influence the cooling and therefore make a changed power loss limit useful.

[0038] Preferably, the aging process of the wind turbine is determined, so the current aging rate of the wind turbine is always taken into account. The aging process can be identified and tracked by recording and appropriately considering variables that impact the wind turbine. These can include special situations that are stressful and are appropriately recorded, such as a storm, an emergency shutdown, or an unusual gust of wind. Aging may be accelerated or delayed if such situations do not occur or occur less frequently than expected.

[0039] However, normal turbine operation also influences aging and can be taken into account. This includes, in particular, how often and / or for how long the wind turbine was operated and at what wind speeds. Wind turbulence intensity can also be considered and influence aging.

[0040] This also makes it possible to assess at a given point in time whether the aging of the wind turbine has progressed faster or slower than planned at that time. If the aging is less advanced, the power can be increased above the rated power, if necessary. This can be taken into account by changing the power loss limit—in this example, by increasing it. If the aging is more advanced than expected at the current point in time, the power loss limit can be reduced to protect the wind turbine accordingly.

[0041] According to one aspect, it is proposed that in order to operate the wind turbine in a transition range for wind speeds from a lower transition wind speed, which is below the nominal wind speed, to an upper transition wind speed, which is above the nominal wind speed, a transition operating characteristic is specified, wherein the transition operating characteristic specifies a blade angle as a function of a detected power, the blade angle increases with increasing detected power, and the wind turbine is operated using the transition operating characteristic until the detected power reaches a switching power value which corresponds to a sum of the nominal power and the boost power.

[0042] The lower transition wind speed can be in the range of 80% to 90% of the rated speed, in particular 80% or 90%. The upper transition wind speed can be in the range of 110% to 120% of the rated speed, in particular 110% or 120%. Here, the blade angle is adjusted depending on the detected power. The power can be determined from a speed-power characteristic curve, where the power is adjusted depending on the detected speed.

[0043] Depending on the wind speed, a speed is established at which a power output is set, which in turn influences the speed. This allows a stable and therefore stationary operating point to be found. In addition, but only when the wind speed approaches the nominal wind speed, the blade angle is adjusted in order to reduce the mechanical load on the turbine, in particular to reduce the impact torque. It was particularly recognized here that reducing the mechanical load can be useful even at wind speeds below the nominal wind speed. The recorded power, i.e. the recorded generated power, is a good indicator of how high the load is and is a good parameter to be taken into account in operational management.

[0044] The proposed operation with the transitional operating characteristic curve is carried out up to a power output that exceeds the rated power. At this point, the turbine has already turned its blades slightly out of the wind and can therefore absorb more mechanical load. This also favors operation at a higher power output than the rated power.

[0045] It is specifically proposed that when the sensed power reaches the switching power value, the power is no longer increased and the blade angle is adjusted by the speed control, which controls the speed by adjusting the blade angle. This allows the operation control to seamlessly transition from using the transient operating characteristic to using the speed control.

[0046] It is preferably proposed to consider the increase power, the current power loss and / or the predetermined power loss limit as a load criterion.

[0047] Building on this, it is proposed to adjust the transient operating characteristic curve depending on the load criterion and / or to select it from several default operating characteristics.

[0048] It was recognized here that different loads can occur even at the same average wind speed, as described above and below. In particular, taking the increased power into account not only takes different loads into account, but also adapts the transitional operating characteristic curve to the subsequent operation with the speed control. The speed control essentially starts when the maximum power, which is above the rated power, is reached. This can vary depending on the load on the wind turbine, and therefore the speed control then starts at different power levels. The result is a continuous curve of power that is dependent on the wind speed. The variation in the transitional operating characteristic curve can ensure that the different power levels are achieved with different blade angles.

[0049] Preferably, an increase in speed above the rated speed is permitted in the transition range. This allows for higher power without excessive torque. It has also been found, and is taken into account, that the overall load can be lower at higher speeds.

[0050] Furthermore, in the transition range, a speed-power characteristic curve is preferably used in addition to the transition operating characteristic curve, which adjusts the power as a function of a detected speed. This allows the wind turbine to be operated effectively in conjunction with the transition operating characteristic curve, as described above.

[0051] Preferably, the speed-power characteristic curve is set depending on the load criterion and / or selected from several preset speed-power characteristic curves. Optionally, the transitional operating characteristic curve is set depending on the selected speed-power characteristic curve and / or selected from several preset operating characteristics. This allows both characteristics to be well coordinated.

[0052] According to one aspect, it is proposed that the power loss limit, the boosted power, and / or operating settings for operating the wind turbine at a power above the rated power be determined as a function of a stator temperature of a stator of the generator. In particular, this is additionally proposed as a function of a predetermined reference stator temperature and a specific thermal coefficient of the generator, in particular of the stator. Furthermore or alternatively, it is proposed to determine the power loss limit, the boosted power, and / or operating settings as a function of the magnetic saturation of the generator.

[0053] Here, it was particularly recognized that the condition of the stator can be a limiting factor for increasing the power above the rated power. This can be taken into account by determining the power loss limit and / or the increased power as a function of the stator, namely the stator temperature and / or the magnetic saturation of the generator.

[0054] It was also recognized here that the stator temperature, in particular, should be limited, as it also influences the air gap between the rotor and stator of the generator. Therefore, if the stator temperature rises too sharply or is too high in absolute terms, the boosted power should be limited or reduced accordingly. This can be achieved by immediately setting or reducing the boosted power accordingly, or by lowering the power loss limit, which then leads to the power loss reaching the power loss limit earlier, which also limits or reduces the boosted power.

[0055] With regard to the magnetic saturation of the generator, it was particularly recognized that when this saturation power is reached, much more power loss is generated in the generator, which must be avoided because it is ineffective on the one hand and can also lead to an undesirably high temperature in the generator on the other.

[0056] All this can also be taken into account by adapted operating settings, so that for the operating settings, in addition or alternatively, it is proposed to determine and then adjust them depending on the stator temperature and / or depending on the magnetic saturation of the generator.

[0057] According to one aspect, it is proposed that the current power loss be determined and the operation of the wind turbine at a power above the rated power be controlled depending on the determined current power loss, wherein the current power loss is determined or estimated, in particular, using a calculation rule. It was recognized here that the current power loss can be a good reference variable for controlling the wind turbine when the power feed-in exceeds the rated power. It is important that the power loss be available with reliable values, and for this purpose, this calculation or estimation is proposed.

[0058] According to one aspect, it is proposed that the current power loss is determined as a function of operating parameters that describe states of operation of the wind turbine, furthermore or alternatively as a function of properties of relevant components that characterize the power loss, in particular a temperature of the relevant component, and furthermore or alternatively as a function of environmental parameters that describe states in an environment of the wind turbine, in particular wind speed, outside temperature, air humidity and / or air pressure.

[0059] It was particularly recognized here that the current power loss can be determined very accurately and then used further if suitable parameters or other variables are taken into account. The current power loss can be determined particularly from operating parameters that describe the operating conditions of the wind turbine. Such operating parameters can include, in particular, the current speed, power, and set blade angle. In particular, the generator power output by the generator and the system power output by the system can be used simultaneously as operating parameters that describe the operating conditions of the wind turbine. The power loss can be determined particularly from the difference between the generator power and the system power.

[0060] In addition to or on its own, properties of relevant components that characterize power loss can be considered. The temperature of relevant components is of particular importance here. Relevant components are those that each account for more than 10% of the power loss. The generator, rectifier, and inverter are particularly relevant components. The connecting cable, particularly the cable between the rectifier and inverter, may also be considered if the rectifier and inverter are located separately, i.e., the rectifier is located in the nacelle near the generator, and the inverter is located in the base of the tower. Obviously, the higher the temperature of relevant components, the higher the power loss. This can be evaluated both qualitatively and quantitatively.

[0061] Environmental parameters, such as wind speed, outside temperature, humidity, and / or air pressure, can be evaluated in addition. From these environmental parameters, boundary conditions that influence power loss can be derived. This allows calculations to be improved based on operating parameters and / or properties of relevant components. However, it is also possible to infer power loss from such environmental parameters alone. This is especially useful if a good simulation for the wind turbine is available or can be created. Ultimately, the operation of the wind turbine depends almost exclusively on such environmental parameters.Environmental parameters, especially wind speed, can be used to determine how the wind turbine would behave, including its power loss. Power loss can also be influenced by the outside temperature; the lower the outside temperature, the better the cooling effect, and vice versa. Humidity and air pressure can also play a role, and these particularly influence the operation of the wind turbine. The same wind speed at different air humidity and / or different air pressure leads to different operation of the wind turbine. All of this could be considered in a simulation, and if this takes into account the turbine behavior, including the proposed power increase, the power loss can be determined.

[0062] Preferably, however, operating parameters, properties of relevant components and environmental parameters are considered together to determine the power loss.

[0063] This means that the power loss is available with good accuracy and the power increase can be controlled or regulated depending on this power loss, so that the greatest possible power increase is possible without setting too high a power loss, i.e. without endangering the system.

[0064] An example calculation formula for the maximum power loss is given below and is also applicable here. The existing power loss is recorded.

[0065] According to one aspect, it is proposed that the current power loss and / or a component temperature be determined as a function of the air gap thickness of the generator. Here, it was particularly recognized that the power loss influences the temperature of the generator. Other temperatures, i.e. component temperatures of other components, also result from the power loss. Although the power loss of the generator does not directly influence the temperature of other components, if, for example, the generator experiences an increase in temperature due to an operating situation and depending on environmental parameters, a temperature increase is to be expected in other components as well. This makes it possible to draw conclusions about the temperature of other components from the generator. The component temperature, however, also includes the temperature of the generator as a possibility.

[0066] Therefore, the current power loss and / or a component temperature, including the temperature of the generator, can be determined from the behavior of the generator. It has been particularly recognized that the rotor and stator of a generator expand to different degrees depending on the temperature. This is due, on the one hand, to the fact that the stator and / or generator are cooled to different degrees or dissipate heat to different degrees. It is also due to the fact that even at the same temperature, different expansion rates can occur.

[0067] This leads to temperature-dependent variations in air gap thickness. If the generator is designed as an internal rotor, an increase in temperature can lead to better cooling of the stator, thus causing less expansion, and more expansion of the rotor, causing the air gap thickness to decrease with increasing temperature. The respective effects, especially in quantitative terms, must be considered individually for each generator type and system type.

[0068] In any case, the current power loss and / or at least one component temperature can be determined in a simple manner by determining the air gap thickness of the generator only at one point.

[0069] According to one aspect, it is proposed that operating parameters of several components of the wind turbine be taken into account to determine the current power loss limit, and in particular, the power loss limit is determined such that the operating parameters taken into account do not exceed predetermined parameter limits. Such operating parameters can be, in particular, temperatures, but also magnetization, a generated electromagnetic force, or a vibration amplitude. Such operating parameters are taken into account, and the current power loss limit is determined accordingly, namely such that the operating parameters taken into account do not exceed predetermined parameter limits.

[0070] It is also possible to implement this through a control system that takes the operating parameters into account and, if they are too high, especially if at least one of these operating parameters is too high, reduces the power loss limit. If all operating parameters are lower than a permissible limit, the power loss limit can be increased.

[0071] In particular, it is proposed that one, several or all of the operating parameters from the following list be taken into account, which includes the following operating parameters: a generator temperature, a temperature of a feed-in unit, a temperature of an electrical line, in particular a line between the generator and the feed-in unit for transmitting electrical power from the generator to the feed-in unit, a temperature of an electrical choke, a temperature of a secondary circuit of an active cooling system, a magnetization of the generator, wherein a magnetic saturation is used as a predetermined parameter limit, an electromagnetic force generated in the generator, and a vibration amplitude of a mechanical vibration caused by the operation of the wind turbine.

[0072] A generator temperature should not be too high, and a temperature limit can be 155°C. This can be a temperature limit for the generator temperature, but also for other elements, particularly the temperature of an electrical cable and the temperature of an electrical choke. This temperature can be related to the permissible temperature of electrical insulation.

[0073] This temperature limit can also apply to the temperature of a power supply unit, but a measurable temperature can have a lower limit for the temperature of a power supply unit. This is because a power supply unit generates high temperatures inside the component due to the switching processes, particularly in its semiconductor switches in the internal boundary layers. The external temperature of such a semiconductor component should therefore be kept below a limit that simultaneously prevents the temperature inside the semiconductor component from becoming too high. Here, too, the power loss limit can be lowered if the temperature of a power supply unit becomes too high.

[0074] The temperature of an electrical cable, especially a cable between the generator and the feed-in unit for transmitting electrical power from the generator to the feed-in unit, should also at least comply with a maximum temperature specified by the electrical insulation, as explained above. When considering the electrical cable, it must be considered that it often has to withstand high tensile loads due to its own weight when suspended in the tower. The connection of the electrical cable from the generator to the feed-in unit can also involve the connection of an active rectifier, located adjacent to the generator, to the inverter, which may be located in the base of the tower.

[0075] An electrical choke can also be a relevant component, and its temperature, like the previously mentioned elements, is highly dependent on the power, as this is fed through the electrical choke. Electrical insulation can also limit the maximum temperature of the electrical choke.

[0076] The temperature of a secondary circuit in an active cooling system provides information about the temperature in the component being cooled. This particularly applies to a primary cooling circuit that cools a component to be cooled using a first cooling medium, and this first cooling medium transfers heat to a second cooling medium in the secondary circuit via a heat exchanger. Simulations or previously conducted studies can then be used to draw conclusions about the higher temperature of the component being cooled based on the lower temperature of the secondary circuit.

[0077] Magnetization of the generator occurs, particularly in the stator, due to the stator current. Such magnetization can be measured if sensors are installed in the generator. However, this is often not the case, and the magnetization can then be inferred from, or in addition to, knowledge of the generator—i.e., its structure and materials—the operating state of the generator, especially its speed, and the stator current.

[0078] It was particularly recognized here that operating the generator in magnetic saturation should be avoided. Magnetic saturation is a material property and can therefore be determined in advance, or at least known for each generator during its development, and this should be taken into account here for controlling or regulating the power increase.

[0079] The electromagnetic force generated in the generator should also not be excessive to prevent mechanical damage or at least limit stress. The electromagnetic force generated in the generator can also be derived from knowledge of the generator, its operating state, in particular the speed, and the stator current. It should be noted that the magnetization is by no means proportional to the generated electromagnetic force, and therefore it is proposed to consider these two operating parameters separately. The magnetic force can also depend on the air gap thickness, so it is proposed to consider this air gap thickness when considering the magnetic force.

[0080] The vibration amplitude of a mechanical vibration caused by the operation of a wind turbine depends on its excitation frequency and thus on the generator's speed, but the amplitude can also be influenced by temperature. For example, a change in temperature can slightly change the expansion of a mechanical component, which can lead to a change in friction if, for example, a corresponding bearing is affected by this thermal expansion. This can amplify vibrations or even cause them to occur. A vibration amplitude can also be related to a magnetic force. If an electromagnetic force between the electromagnetic rotor (i.e., a runner) and the stator becomes too large, it can lead to vibration due to the rotation of the runner.

[0081] All of this has been recognized, and therefore it is proposed to consider the vibration amplitude. If it is too large or threatens to become too large, it is suggested to reduce the power dissipation limit.

[0082] According to one aspect, it is proposed that the boost power, the current power loss and / or the power loss limit and / or the limit torque for the impact torque is determined depending on one, several or all of the following criteria, which can be referred to as determination criteria.

[0083] One determining criterion is the location of the wind turbine. Such a location can be particularly characterized by environmental parameters such as air pressure, average temperature, and average turbulence intensity. Air pressure depends particularly on the altitude of the installation site, while average temperature depends, among other things, on the geographical latitude. The location of the wind turbine can particularly influence whether the wind turbine is subject to comparatively high or low loads, and accordingly, the boosted power, which also represents a load for the wind turbine, can be more or less significant.

[0084] One determining factor can be the wind direction. The wind direction can be considered in conjunction with the installation location and can provide information about whether more or less stressful winds can be expected, as more turbulent winds can be expected from some wind directions due to obstacles. Humidity and / or temperature can also depend on the wind direction, and possibly also on the time of day and / or season.

[0085] The time of day and / or season can also be a determining factor, independent of wind direction—in other words, quite generally. For example, a higher load may be expected in summer than in winter because higher temperatures are expected in summer, which can be more critical for operation at excessive power. However, it's also possible that in particularly cold locations, the temperature may be so low in winter that the material is so brittle that this doesn't allow for excessive power increase, or at least not to an excessive degree.

[0086] Turbulence intensity is another determining criterion and also influences the mechanical load on the wind turbine, especially on the rotor blades. Preferably, the limit torque can be reduced at high turbulence intensity, thereby allowing only a lower impact torque.

[0087] It should be noted that a maximum impact torque is a characteristic of the wind turbine; among other things, it is designed for this purpose. However, the limiting torque is specified in such a way that a tolerance is also maintained so that variations in the impact torque, particularly due to changes in the wind, especially gusts, do not lead to an excessive increase. Depending on the situation, particularly the wind conditions—i.e., whether the wind is gusty or strong, and / or exhibits strong or small changes in direction—a larger or smaller tolerance may be sufficient, allowing different values ​​for the limiting torque to be used.

[0088] Wind shear is another determining factor. Wind shear indicates that the wind field is not homogeneous, but rather that different wind speeds occur at different locations, especially at different heights, and can therefore lead to asymmetrical loads on the blades and / or rotor. Accordingly, wind shear also influences the overall load on the wind turbine, and in cases of strong wind shear, the boost power may be lower than in cases of weak wind shear.

[0089] One determining factor can be the ambient temperature. As already mentioned above, the ambient temperature can have a particularly strong influence on the cooling of the wind turbine, allowing for better dissipation of power losses and keeping the temperature inside the wind turbine lower. This would then allow for a greater increase in power output.

[0090] Air pressure is another determining criterion and different air pressures can lead to different loads on the rotor blades, so it is suggested that this be taken into account here.

[0091] Humidity can also be a determining factor. Humidity also influences the force that the wind can exert on a rotor blade at the same wind speed. Simply put, humid air is heavier and can therefore lead to stronger forces.

[0092] According to one aspect, it is proposed that, in order to operate the wind turbine with a power above the rated power, operating settings, in particular the blade angle, are set as a function of the current wind speed and as a function of the boost power, the current power loss and / or the power loss limit and / or the operating settings are determined by a calculation rule.

[0093] It is therefore proposed to explicitly consider the wind speed when adjusting the operating settings, particularly the blade angle. Additionally, the boosted power, the current power loss, and / or the power loss limit are taken into account. A control system is thus provided that selects or changes operating settings based on these values, in particular determining the blade angle based on these variables. The blade angle is thus adjusted based on the current wind speed and also based on the boosted power, the current power loss, and / or the power loss limit. This allows an operating point to be directly specified and adjusted. This prevents vibrations from occurring due to closed-loop control. Mechanical overloads on the structure are also reduced.

[0094] According to one aspect, it is proposed that for operating the wind turbine in storm operation, when the wind speed is above a predeterminable storm wind speed, a storm characteristic curve is provided which specifies a relationship between speed and power, wherein for controlling the wind turbine in a transition from full-load operation to storm operation, when the wind turbine is operated in full-load operation with a power above the rated power, a transition storm characteristic curve is provided which specifies a relationship between speed and power that differs from the relationship according to the storm characteristic curve, wherein in particular the transition characteristic curve assigns higher power values ​​to the same speed values ​​compared to the storm characteristic curve.

[0095] The storm characteristic curve and the transition characteristic curve can be viewed as operating characteristics. They each assign a power value to a speed. In particular, it can be provided that this storm characteristic curve or transition characteristic curve is implemented in such a way that a speed is recorded and, depending on this, a power is set. In particular, it can be provided that the wind speed is recorded and, depending on the wind speed, the speed is first set by adjusting the rotor blades and then the power is adjusted accordingly, or that, depending on the wind speed, the speed and power are specified according to the characteristic curve by setting the power, in particular by correspondingly controlling the generator, and the rotor blades are adjusted so that the desired speed is then achieved.

[0096] In any case, both the storm characteristic curve and the transition characteristic curve assign power values ​​to speed values. The characteristic curve can therefore be represented by a variety of speed-power pairs. The transition characteristic curve is intended to differ from the storm characteristic curve. The transition characteristic curve is intended for the case where the wind turbine is operated at full load with a power above the rated power. This particularly applies to an operating point where the wind speed is already quite high, almost just before reaching storm wind speed.

[0097] It was particularly recognized here that the storm characteristic curve is designed to reduce the power below the rated power and the speed below the rated speed starting at storm wind speed. The idea behind this is that at the transition point, when storm wind speed is present, the power must be reduced below the rated power as the wind speed continues to increase in order to protect the turbine. At storm wind speed, the rated power is therefore the maximum permissible power. It was therefore recognized that if the wind turbine is operated at full load with a power above the rated power, this leads to an operating point at storm wind speeds that differs from the operating point, i.e. from the combination of speed and power according to the storm characteristic curve. The storm characteristic curve specifies the rated power for the storm wind speed, which is the point at which the storm characteristic curve begins.

[0098] It is proposed here not to make a sudden change from the increased power at the moment of storm wind speed to the rated power according to the storm characteristic curve, but instead to provide a transition characteristic curve. This transition characteristic curve can transition into the storm characteristic curve at wind speeds exceeding the storm wind speed. However, the storm characteristic curve and the transition characteristic curve preferably differ beyond the storm wind speed, and in particular even across the entire storm range. The transition characteristic curve then specifies a relationship between speed and power for part of or the entire storm range, independent of and deviating from the storm characteristic curve.

[0099] In addition to the aspect of avoiding the aforementioned jump, this is also based on the knowledge that even in the event of a storm, higher power can be drawn than is provided for by the storm characteristic curve. Here, too, the load on the system can be checked in addition to operation with the transition characteristic curve. In particular, when operating with the transition characteristic curve, it can be checked that impact loads and power loss do not become too great, although the power loss cannot become too great on its own since the power is reduced anyway. However, if this load check reveals that the planned speed and / or power are too high according to the transition characteristic curve, an adjustment of the transition characteristic curve can be provided.

[0100] According to the invention, a wind turbine is also proposed, which is designed as explained above and has a control device for controlling the wind turbine. Furthermore, the wind turbine is configured to carry out a method for controlling a wind turbine according to at least one of the embodiments described above. In particular, the control device is configured to carry out such methods.

[0101] The control device can be designed as a process computer and coupled to the corresponding elements of the wind turbine. Furthermore, a connection to an external weather forecast and / or external sensors for detecting environmental parameters can be provided.

[0102] The method can in particular be implemented on such a process computer, in particular via a program code which carries out the corresponding method steps when executed on a computer.

[0103] This makes it possible to propose a wind turbine that can achieve increased yield while avoiding unnecessary overloads.

[0104] The invention will now be described below by way of example using embodiments with reference to the accompanying figures. Figure 1 shows a perspective view of a wind turbine. Figure 2 shows a power / impact torque-wind speed diagram illustrating the previous behavior of a wind turbine. Figure 3 shows a power-wind speed diagram illustrating the invention. Figure 4 shows a blade angle-wind speed diagram illustrating the invention. Figure 5 shows a impact torque-wind speed diagram illustrating the invention. Figure 6 schematically shows a control structure illustrating the invention.

[0105] Fig. 1shows a schematic representation of a wind turbine according to the invention. The wind turbine 100 has a tower 102 and a nacelle 104 on the tower 102. An aerodynamic rotor 106 with three rotor blades 108 and a spinner 110 is provided on the nacelle 104. During operation of the wind turbine, the aerodynamic rotor 106 is set in rotation by the wind and thus also rotates an electrodynamic rotor or rotor of a generator, which is directly or indirectly coupled to the aerodynamic rotor 106. The electric generator is arranged in the nacelle 104 and generates electrical energy. The pitch angles of the rotor blades 108 can be changed by pitch motors at the rotor blade roots 109 of the respective rotor blades 108.

[0106] The wind turbine 100 has an electrical generator 101, which is indicated in the nacelle 104. Electrical power can be generated by means of the generator 101. A feed-in unit 105, which can be designed particularly as an inverter, is provided for feeding in electrical power. This allows a three-phase feed-in current and / or a three-phase feed-in voltage to be generated according to amplitude, frequency, and phase for feeding into a grid connection point PCC. This can be done directly or jointly with other wind turbines in a wind farm. A system controller 103 is provided for controlling the wind turbine 100 and the feed-in unit 105. The system controller 103 can also receive default values ​​from external sources, in particular from a central farm computer.

[0107] Figure 2shows a diagram in which the power P and the impact torque mS are plotted as a function of wind speed. The wind speed is plotted in m / s along the abscissa, and the power and impact torque, each normalized to nominal values, are plotted along the ordinate.

[0108] The diagram assumes a nominal wind speed of approximately 10 m / s. Up to this point, the wind turbine operates at partial load. At the nominal wind speed, the wind speed P reaches its maximum value, namely the nominal power, and thus 100%. From the nominal wind speed, the power is maintained at the nominal power.

[0109] The impact torque also increases with increasing wind speed in the partial load range, but reaches its maximum value, i.e., 100%, earlier—in the example shown, at a wind speed of 8 m / s. This ensures that the certified loads are not exceeded. The increasing wind load as the wind speed continues to rise is compensated for by adjusting the rotor blades, so that the impact torque initially remains at its maximum value of 100%.

[0110] At a nominal wind speed of 10 m / s in the example, the rotor blades are adjusted more to maintain the power at their nominal value, i.e., 100%. This means that, starting at the nominal wind speed, the impact torque decreases as the wind speed continues to increase.

[0111] It was recognized that this decrease in the impact torque with increasing wind speed above the rated wind speed opens up the possibility of increasing the power output beyond the rated power. At least this mechanical loading of the impact torque allows this. It was particularly recognized that the impact torque decreases quite sharply. This possibility for increasing power output should be exploited, although other limiting criteria must be taken into account.

[0112] Figure 3shows a power curve as a function of wind speed, showing the normal power P 0 and the increased power PB. Both power curves are identical up to the nominal wind speed at the example 10 m / s. From there, the increased power can assume larger values, so that the increased power PB increases slightly from the nominal wind speed. However, it soon reaches a plateau, which is primarily due to the fact that other limitations must be considered, particularly electrical and / or thermal limitations related to the power.

[0113] Nevertheless, the Figure 3 that performance increases of 5% and more are achievable. Figure 3 It also illustrates that the power increase is not only possible for a small range, but can be considered for the entire full-load range. And in this respect, the diagram of the Figure 3and thus also the area of ​​increased power up to approximately the end of the full load range, followed by a storm area, which is not shown in this diagram.

[0114] Figure 4 shows the progression of a blade angle as a function of the wind speed, whereby a normal blade angle progression α 0 and a blade angle curve α B for increased performance. It can be seen that both blade angle curves are consistent up to the nominal wind speed of the example 10 m / s.

[0115] From the nominal wind speed, the blade angle is adjusted according to the blade angle α B for the increased performance initially increased less than the normal blade angle α 0 .However, above a certain wind speed, which in this example is 12 m / s, both blade angle curves run parallel to each other. They run parallel to each other starting at the wind speed at which the increased power has also reached a plateau, and thus the increased power runs parallel to the non-increased power, i.e., parallel to the nominal power value.

[0116] In both cases, the rotor blades are rotated further out of the wind as the wind speed increases, thus reducing the load accordingly. α B For the increased performance, the blade angle values ​​are slightly lower, so that the blades are turned slightly less out of the wind than with the normal blade angle α 0 .

[0117] Figure 5shows a diagram in which the blade pitching moment is plotted as a function of wind speed. Here, too, the normal curve is compared with the curve for increased power. The normal curve thus shows the blade pitching moment m S , and the curve for increased power shows the pitching moment m SB .

[0118] The course of the normal impact moment m S therefore also corresponds to the course of the impact moment according to Figure 2 .

[0119] The impact torque mSB corresponding to increased power also decreases with increasing wind speed from the nominal wind speed, but not as sharply. Nevertheless, it decreases significantly, so the increase in power underlying the impact torque mSB does not pose a load problem for the impact torque.

[0120] Figure 6shows schematically a control structure 600 with a schematically indicated wind turbine 602, which also feeds into an electrical supply network 604, only schematically indicated.

[0121] The structure illustrates that the wind turbine 602 is basically controlled by having a power setpoint PS and a blade angle setpoint α S The blade angle is the result of a speed control with speed controller 606. The speed controller 606 receives a speed difference, which is formed at the first summing point 608 from the target speed, which is specified here as the nominal speed n N, and the actual speed ni. The resulting control error e is thus input into the speed controller 606 and, depending on this, a blade angle to be set α S A common application can also be designed so that instead of an absolute blade angle α S a blade angle adjustment rate is output. For this purpose, the blade angle α S be representative.

[0122] To control the power increase, it is preferable to increase only the power and not the speed. The speed controller shown can therefore continue to operate normally even if the power is increased beyond the rated power. However, different values ​​for the blade angle will result because increasing the power, which will be explained shortly, slows down the speed, so the blade angles need to be adjusted less to maintain the same speed.

[0123] Power control is basically done by specifying a desired power output as power PS, i.e. as target power. This power target can be specified in an operational control system, which for the sake of simplicity is Figure 6is not shown. However, during full-load operation, before storm operation, the nominal power PN is specified as the target power. In this case, if no power increase is proposed, the target power PS corresponds to the nominal power PN.

[0124] The power increase block 610 is provided for increasing the power. The power increase block 610 thus calculates a possible increase in power P +< , which is added to the specified power, in this case the nominal power PN, in the second summing point 612. This can result in a higher value for the target power PS than the nominal power PN.

[0125] To calculate this increase in power P +<, a maximum impact torque m SM is taken into account, which thus forms a limiting moment for the impact torque. This value is symbolically represented in the Figure 6entered into the power increase block 610. Since this value can be a fixed value, it can also be implemented in a fixed manner, which is intended to be included in this symbolic representation of the input of the maximum impact torque m SM.

[0126] In addition, a predetermined power loss limit P VL is taken into account. This power loss limit, which specifies a maximum value for the power loss, can be variable, and its calculation is explained below.

[0127] To take these two maximum values, i.e., the maximum impact torque m SM and the power loss limit P VL, into account, the corresponding measured values ​​or recorded values ​​are considered and also entered into the power increase block 610. Thus, the current impact torque m S and the current power loss PV are entered into the power increase block 610.

[0128] The power increase block 610 takes this into account accordingly, namely so that the current impact torque m S does not exceed the maximum impact torque m SM. Furthermore, the increase power P +< is specified so that the current power loss PV does not exceed the power loss limit P VL.

[0129] A determination block 614 is provided for determining the current impact torque m S and the current power loss PV. This determination block 614 can receive many values ​​that were recorded at the wind turbine. These can include various component temperatures, for which the temperature T i stands symbolically and representatively here. In addition, the determination block 614 can receive the current power P, the current torque of the generator m and various other variables of the generator, for which a generator variable G is symbolically shown. Further values ​​can also be recorded, such as the operating states of auxiliary devices such as a fan of a cooling system or a circulating pump of a cooling circuit with a liquid medium. All of these variables, and in particular the recorded speed ni, are entered in this determination block 614.

[0130] The determination block 614 can also receive environmental parameters such as an outside temperature TU or a wind speed VW from a measuring mast 616. However, such and other environmental parameters can also be determined by the wind turbine, for example, by sensors arranged on the nacelle.

[0131] In particular, the determination block 614 can determine the current values ​​of the blade pitch moment ms and the power loss PV. For this purpose, an estimation algorithm can be provided, or a control-engineering estimator, such as a state observer, can be used.

[0132] The power loss limit P VL is also determined in the determination block. This can also depend on many of these measured values ​​of the wind turbine 602.

[0133] The determination block 614 thus determines the current blade pitch torque m S , the current power loss PV , and a maximum power loss P VL , which forms the power loss limit. If, in another embodiment, the maximum blade pitch torque m SM is also to be set variably, in particular depending on the situations or conditions of the wind turbine, it could also be determined by the determination block 614.

[0134] According to the invention, the following was also recognized or the following is proposed.

[0135] It has been recognized that the limiting factors for the maximum possible power in a wind turbine, which can also be abbreviated as WEA, can be summarized in the following three categories: Category 1: Loads: The maximum impact load and maximum torque, in particular, define the loads. They are limited by the certified loads. Category 2: Grid restrictions: The electrical grid may specify a maximum power that can be fed in. This is often defined in advance and depends particularly on the grid connection point. Category 3: Operating parameters: Operating parameters of all components of the wind turbine may require limitations. In particular, speed, magnetic saturation and temperatures of various components, in order to To name just a few examples, limiting operating parameters can be found.

[0136] In order to increase performance, especially regardless of the duration outside the nominal range, the limits in all three categories mentioned above must not be violated.

[0137] The Figure 2 This shows the curve of the blade pitch torque and power versus wind speed for a potential wind turbine according to a simulation. It can be seen that the pitch torque m S , which is therefore a load, reaches its maximum value even before the nominal wind speed, in this case 10 m / s, is reached, and then decreases due to the pitch control that can result from the speed control. This application focuses specifically on the range above the nominal wind speed of 10 m / s. This ensures that the certified loads are not exceeded.

[0138] If it should become apparent that in the wind speed range above the nominal wind speed at which the wind turbine reaches its rated power, a greater than the design torque of the rotor and thus also a higher power than the rated power of the generator is desired under certain circumstances, this can be achieved by a targeted adjustment of the pitch control, which also Figure 2 to illustrate.

[0139] For this purpose, the pitch parameters are changed so that in the range above the nominal wind speed, larger operating angles of attack are driven on the rotor blades, which leads to the result according to Figure 3 This increases the lift and thus the torque of the rotor at the same speed. However, the angle of attack is only increased to the extent that it is ensured that the maximum permissible blade impact loads are not exceeded, which Figure 4is intended to illustrate this. With this approach, the rotor speed generally remains unchanged compared to the standard design.

[0140] The pitch parameters can also be adjusted gradually depending on the required torque and power. The pitch parameters can indicate the set blade angles and can be adjusted via a speed control.

[0141] In order to increase the maximum permissible power to be fed in above the nominal power of the wind turbine, it may be necessary to coordinate this increase with grid operators or other authorities.

[0142] According to the invention, it is specifically proposed to develop an operating system that does not exceed the permissible operating parameters for all relevant components while meeting the conditions of Categories 1 and 2 (loads and grid constraints). This application defines different methods for increasing power without damaging the wind turbine components.

[0143] Different methods or partial approaches are proposed to define the possible control parameters.

[0144] The following method takes into account component efficiency or electrical losses.

[0145] The electrical losses of a wind turbine component, such as the stator of a generator, can be determined by measurement. A predefined maximum permissible power loss can be defined or predetermined depending on wind speed, rotation speed (i.e., rotor speed), atmospheric pressure, and atmospheric density. This information can already be included in an operational control system for standard values ​​of pressure and density and, if necessary, expanded for other values ​​of pressure and density.

[0146] The following method uses a control.

[0147] The real power loss can be determined using the following formula: Pv , max = R real / R 20 − 1 / f + 20 − p / R . ρ / α Pv,max: is the maximum permissible power dissipation of a component, unit [W]; R real: is the measured electrical resistance of the component, unit [ohm]; R20: is the electrical resistance at 20°C, unit [ohm]; f: is a correction factor that can be assumed to be 0.004; p: is atmospheric pressure, unit [Pa]; R: is a gas constant, which for air is 287 J / kg.K ρ : is the air density [kg / m 3< ] α : is a slope factor. Can be determined for a component using simulation or measurement data.

[0148] Various options are suggested for controlling the system: 1. The power loss can be kept constant. 2. A speed-dependent maximum power loss is specified. The maximum permissible power loss can be determined using the following formula: P vr = T st − T ref / α spez with the power loss P vr , the maximum stator temperature T st, the reference temperature T ref , and the specific heat coefficient α spec . T st and αSpec depend solely on the turbine-type-specific configuration and the materials used. 3. A wind speed- and speed-dependent power loss is defined. This is particularly advantageous for components that are partially or completely cooled directly by the outside air, as the generator can tolerate significantly higher power losses with increasing wind speed. 4. A maximum power loss or a power loss profile is defined using an aging formula such as the Arrhenius formula. The aging formulas can be applied based on input data such as the expected temperature distribution in an electrical component and the residual dielectric strength of the insulation after a predefined number of operating hours / years.The dielectric strength of the insulation of an electrical component, especially the generator and choke, to name just a few examples, decreases over time, especially under high or excessive loads, and must not fall below a certain limit, e.g., 60% of the initial value. Thus, the residual dielectric strength can influence or dictate the service life of the component under a specific load profile.

[0149] The following option takes the generator air gap into account.

[0150] One possible solution is to control a temporary power increase based on the air gap between the rotor and stator of the generator. This temporary power increase can also be referred to as a temporary power boost. For this purpose, an optical measuring system can be installed in the generator to continuously determine the air gap size, specifically the distance between the rotor and stator.

[0151] Assuming that the expansion of a body is proportional to the temperature change, the air gap reduces linearly when the generator heats up L rot T = L rot T ref ⋅ 1 + α rot T − T ref L stat T = L stat T ref ⋅ 1 + α stat T − T ref

[0152] Where L is the diameter of the generator, α red , α stat is the coefficient of thermal expansion, T is the temperature of the generator. The indices rot and stat refer to the rotor and stator of the generator, respectively. Ref denotes the reference values.

[0153] This allows you to calculate the air gap to d = L rot − L stat = L rot Tref − L stat T ref + α rot − α stat ⋅ T − T ref

[0154] It is now possible to determine the permissible minimum air gap using simulations, calibration measurements, or the maximum permissible temperatures of the materials. If the measured air gap is exceeded during system operation, the limit of the temporary power boost or temporary power increase is reached, and the generated power must be reduced. It is possible to specify a speed-dependent minimum air gap.

Claims

1. A method for controlling a wind power installation (100; 602) having an aerodynamic rotor (106) which is operable at variable speed and which has rotor blades (108) which are adjustable in terms of their blade angle (αB), and having a generator (101) for generating a generator power, the wind power installation (100; 602) being distinguished by a nominal speed (nN), a nominal power (PN) and a nominal wind speed at which the nominal speed (nN) and the nominal power (PN) are reached, and the method comprises: - for a wind speed above the nominal wind speed, - operating the wind power installation (100; 602) at a power above the nominal power (PN), - the power being above the nominal power (PN) by a boost power (P+), - the wind power installation (100; 602) being operated in such a way that a flapwise torque (ms) remains below a predetermined limit torque, characterized in that - a prevailing power loss (PV) does not exceed a predetermined power loss limit (PVL).

2. The method as claimed in claim 1, wherein, - provided that the wind speed is sufficiently high, - the wind power installation (100; 602) is continuously operated at a power above the nominal power (PN), in particular over a period of at least 10 minutes, in particular of at least one hour, and / or wherein - the boost power (P+) is at least 1%, preferably at least 5%, in particular at least 8%, of the nominal power (PN).

3. The method as claimed in claim 1 or 2, wherein, - while the wind power installation (100; 602) is being operated at the power above the nominal power (PN), the speed is regulated to nominal speed (nN).

4. The method as claimed in any of the preceding claims, wherein, - during operation of the wind power installation (100; 602) at a power above the nominal power (PN), the power loss limit (PVL) is determined on the basis of a cooling power, in particular - the cooling power being estimated or being calculated using a calculation rule, and / or - the cooling power for the generator (101) and / or further electrical components, in particular an electrical drive train, being determined, and / or - the wind power installation (100; 602) being operated at a power above the nominal power (PN) in such a way, in particular the boost power (P+) being chosen in such a way that a generator torque does not exceed a predeterminable generator limit torque, and / or the generator torque being set in such a way that the generator limit torque is not exceeded, and in particular the generator limit torque being set on the basis of operational settings and / or environmental conditions.

5. The method as claimed in any of the preceding claims, wherein, - during operation of the wind power installation (100; 602) at a power above the nominal power (PN), - the power loss (PV) is kept constant, in particular at the value of the power loss limit (PVL), and / or - the power loss limit (PVL) is determined as power loss (PV) dependent on the speed, - the power loss limit (PVL) being determined on the basis of at least one variable from the list comprising - wind speed, - outside temperature, - speed, - air pressure and - air density, and / or - the power loss limit (PVL) being specified on the basis of an aging characteristic of the wind power installation (100; 602), in particular in the form of a power loss profile, and / or on the basis of a residual dielectric strength.

6. The method as claimed in any of the preceding claims, wherein, - for operating the wind power installation (100; 602) in a transition range for wind speeds from a lower transition wind speed below the nominal wind speed to an upper transition wind speed above the nominal wind speed, a transition operating characteristic curve is specified, - the transition operating characteristic curve specifying a blade angle (αB) as a function of a measured power, - the blade angle (αB) increasing as the measured power increases, and - the wind power installation (100; 602) being operated using the transition operating characteristic curve until the measured power reaches a switching power value which corresponds to a sum of nominal power (PN) and boost power (P+), in particular, - if the measured power reaches the switching power value, the power not being increased any further and the blade angle (αB) being set by a or the speed regulator which regulates the speed by adjusting the blade angle, and / or - the boost power (P+), the prevailing power loss (PV) and / or the predetermined power loss limit (PVL) being considered as a loading criterion, and / or - the transition operating characteristic curve being set on the basis of the loading criterion and / or being chosen from a plurality of default operating characteristic curves, and / or - an increase in the speed to above nominal speed (nN) being permitted in the transition range, and / or - in the transition range, in addition to the transition operating characteristic curve, use being made of a speed-power characteristic curve which sets a power as a function of a measured speed, and / or - the speed-power characteristic curve being set on the basis of the loading criterion and / or being chosen from a plurality of default speed-power characteristic curves and optionally - the transition operating characteristic curve being set on the basis of the chosen speed-power characteristic curve and / or being chosen from a plurality of default operating characteristic curves.

7. The method as claimed in any of the preceding claims, wherein - the power loss limit (PVL), the boost power (P+) and / or operational settings for operating the wind power installation (100; 602) at a power above the nominal power (PN) are / is determined - on the basis of a stator temperature of a stator of the generator, in particular additionally on the basis of a predetermined reference stator temperature and a specific thermal coefficient of the generator, in particular of the stator, and / or - are / is determined on the basis of a magnetic saturation of the generator.

8. The method as claimed in any of the preceding claims, wherein - the prevailing power loss (PV) is determined and the operation of the wind power installation (100; 602) at a power above the nominal power (PN) is controlled on the basis of the determined prevailing power loss (PV), - the prevailing power loss (PV) being determined in particular by means of a calculation rule, or being estimated.

9. The method as claimed in any of the preceding claims, wherein - the prevailing power loss (PV) is determined - on the basis of operational parameters which describe states of operation of the wind power installation (100; 602), and / or - on the basis of properties of relevant components characterizing the power loss (PV), in particular a temperature of the relevant component in each case, and / or - on the basis of environmental parameters which describe conditions in an environment of the wind power installation (100; 602), in particular wind speed, outside temperature, humidity and / or air pressure.

10. The method as claimed in any of the preceding claims, wherein - the prevailing power loss (PV) and / or a component temperature are / is determined on the basis of an air gap thickness of the generator.

11. The method as claimed in any of the preceding claims, wherein, - for determining the prevailing power loss limit (PVL), operational parameters of a plurality of components of the wind power installation (100; 602) are considered, and - in particular the power loss limit (PVL) is determined in such a way that the considered operational parameters do not exceed predetermined parameter limits, - in particular one, a plurality or all of the operational parameters from the following list being considered, said list comprising - a generator temperature, - a temperature of an infeed unit (105), - a temperature of an electrical line, in particular a line between the generator (101) and the infeed unit (105) for transmitting electrical power from the generator (101) to the infeed unit (105), - a temperature of an electrical inductor, - a temperature of a secondary circuit of an active cooling system, - a magnetization of the generator, a magnetic saturation being used as the predetermined parameter limit, - an electromagnetic force generated in the generator (101), and - a vibration amplitude of a mechanical vibration caused by the operation of the wind power installation (100; 602).

12. The method as claimed in any of the preceding claims, wherein - the boost power (P+), the prevailing power loss (PV) and / or the power loss limit (PVL), and / or the limit torque for the flapwise torque (ms), - are / is determined on the basis of one, a plurality or all of the criteria from the list comprising - a site of the wind power installation (100; 602), - a wind direction, - time of day and / or time of year, - a turbulence intensity, - a wind shear, - an environmental temperature, - an air pressure, and - a humidity.

13. The method as claimed in any of the preceding claims, wherein, - for operating the wind power installation (100; 602) at a power above the nominal power (PN), - operational settings, in particular the blade angle (αB), are set on the basis of the prevailing wind speed and - on the basis of the boost power (P+), the prevailing power loss (PV) and / or the power loss limit (PVL), and / or - the operational settings are determined by a calculation rule.

14. The method as claimed in any of the preceding claims, wherein, - for operating the wind power installation (100; 602) in a storm mode when the wind speed is above a predeterminable storm wind speed, a storm characteristic curve which specifies a correlation between speed and power is provided, - for controlling the wind power installation (100; 602) in a transition from full-load operation to storm mode when the wind power installation (100; 602) is operated in full-load operation at a power above the nominal power (PN), a transition characteristic curve which specifies a correlation between speed and power, said correlation differing from the correlation according to the storm characteristic curve, is provided, in particular - the transition characteristic curve assigning higher power values to the same speed values in each case as compared to the storm characteristic curve.

15. A wind power installation (100; 602) having an aerodynamic rotor (106) which is operable at variable speed and which has rotor blades (108) which are adjustable in terms of their blade angle (αB), and having a generator (101) for generating a generator power, the wind power installation (100; 602) being distinguished by a nominal speed (nN), a nominal power (PN) and a nominal wind speed at which the nominal speed (nN) and the nominal power (PN) are reached, and the wind power installation (100; 602) - having a control device for controlling the wind power installation (100; 602), characterized in that the wind power installation - being set up to perform a method for controlling a wind power installation according to one of the preceding claims, in particular - the control device being set up to perform the method.