阅读说明：本技术 运行风能设备的方法、运行风能设备的控制设备、风电场 (Method for operating a wind energy installation, control device for operating a wind energy installation, wind farm ) 是由 斯特凡妮·博特 阿尔琼·布吕克 于 2021-06-16 设计创作，主要内容包括：一种运行具有转子的第一风能设备的方法,转子具有能以桨距角调节的转子叶片,第一风能设备产生电功率,在至少一个尾流风向的情况下,在第一风能设备的尾流中存在第二风能设备,方法包括步骤：在不受尾流影响的正常运行中,以第一桨距特征曲线运行第一风能设备；以及在受尾流影响的尾流运行中,以第二桨距特征曲线运行第一风能设备,其中与电功率相关地,第一桨距特征曲线代表桨距角的第一变化曲线,而第二桨距特征曲线代表桨距角的第二变化曲线,对于电功率的至少一个范围,第二桨距特征曲线的桨距角大于第一桨距特征曲线的桨距角。方法在遵守辅助条件如遵守最大推力系数或影响尾流的湍流强度的情况下致力于第二风能设备的年能源产量最大化。(A method of operating a first wind power plant having a rotor with rotor blades adjustable with a pitch angle, the first wind power plant generating electrical power, in the case of at least one wake direction, a second wind power plant being present in the wake of the first wind power plant, the method comprising the steps of: in normal operation, which is not influenced by the wake, the first wind power installation is operated with a first pitch characteristic curve; and operating the first wind energy plant in a wake operation affected by the wake with a second pitch characteristic curve, wherein in relation to the electrical power the first pitch characteristic curve represents a first change of the pitch angle and the second pitch characteristic curve represents a second change of the pitch angle, the pitch angle of the second pitch characteristic curve being larger than the pitch angle of the first pitch characteristic curve for at least one range of electrical power. The method aims at maximizing the annual energy production of the second wind energy plant while observing auxiliary conditions, such as observing a maximum thrust coefficient or influencing the turbulence intensity of the wake.)

1. A method for operating a first wind energy plant (100a) having a rotor (106) with rotor blades (108) adjustable with a pitch angle (114), the first wind energy plant generating electrical power and in the wake of which, in the case of at least one wake wind direction (W), a second wind energy plant (100b) is present, comprising the steps of:

-operating the first wind energy plant (100a) with a first pitch characteristic (204) in normal operation substantially unaffected by the wake and operating the first wind energy plant (100a) with a second pitch characteristic (208) in wake operation affected by the wake,

-wherein the first pitch characteristic curve (204) represents a first variation of the pitch angle (114) with respect to the electrical power and the second pitch characteristic curve (208) represents a second variation of the pitch angle (114) with respect to the electrical power,

-wherein for at least one range of the electrical power, a pitch angle (114) of the second pitch characteristic curve (208) is larger than a pitch angle (114) of the first pitch characteristic curve (204).

2. The method according to claim 1, wherein the first pitch characteristic curve (204) and the second pitch characteristic curve (208) substantially coincide with each other up to a first power threshold (207) of the electrical power, and a pitch angle (114) of the second pitch characteristic curve (208) is larger than a pitch angle (114) of the first pitch characteristic curve (204) for electrical power exceeding the first power threshold (207).

3. A method according to claim 1 or 2, wherein for electric power smaller than the first power threshold (207), the pitch angle (114) of the first pitch characteristic curve (204) and the pitch angle (114) of the second pitch characteristic curve (208) are substantially the same, and/or wherein until the first power threshold (207) is exceeded the change curve of the first pitch characteristic curve (204) and/or the change curve of the second pitch characteristic curve (208) have substantially no slope.

4. Method according to any of the preceding claims, wherein the first wind energy plant (100a) has a maximum allowed thrust coefficient in relation to the wind speed, wherein the pitch angle (114) of the second pitch characteristic (208) has a variation curve such that the thrust coefficient occurring at the first wind energy plant (100a) does not substantially exceed the maximum allowed thrust coefficient.

5. Method according to any of the preceding claims, wherein the first wind energy plant (100a) has a maximum allowed turbulence intensity related to the wind speed, wherein the pitch angle (114) of the second pitch characteristic (208) has a variation curve such that the turbulence intensity generated at the first wind energy plant (100b) does not substantially exceed the maximum allowed turbulence intensity.

6. Method according to any of the preceding claims, wherein for electric power exceeding the first power threshold (207) and being smaller than a second power threshold, the pitch angle (114) of the first pitch characteristic curve (204) is substantially constant and the pitch angle (114) of the second pitch characteristic curve (208) increases, preferably continuously, particularly preferably linearly.

7. Method according to the preceding claim, wherein for electric power exceeding the second power threshold the first pitch characteristic (204) has a positive slope preferably smaller than the slope of the second pitch characteristic (208).

8. A method according to any of the preceding claims, wherein the pitch angle (114) of the second pitch characteristic curve (208) is substantially constant and preferably takes a value between 4 ° -8 °, in particular between 6 ° -7 °, for electrical power exceeding a third power threshold value larger than the first power threshold value (207).

9. The method according to any of the preceding claims, wherein the first power threshold (207) is between 70% and 80% of the rated power of the first wind energy device (100 b).

10. A control device for operating a first wind power plant (100b) having a rotor (106) with rotor blades (108) which can be adjusted with a pitch angle (114), which first wind power plant generates electrical power and in the wake of which, in the case of at least one wake direction, a second wind power plant is present, wherein the control device is set up to,

-operating the first wind energy plant (100a) with a first pitch characteristic (204) in normal operation substantially unaffected by the wake and with a second pitch characteristic (208) in wake operation affected by the wake,

-wherein the first pitch characteristic curve (204) represents a first variation of the pitch angle (114) with respect to the electrical power and the second pitch characteristic curve (208) represents a second variation of the pitch angle (114) with respect to the electrical power,

-wherein for at least one range of the electrical power, a pitch angle (114) of the second pitch characteristic curve (208) is larger than a pitch angle (114) of the first pitch characteristic curve (204).

11. Wind farm having a first wind energy installation (100a) with a rotor (106) having rotor blades (108) which can be adjusted with a pitch angle (114), which first wind energy installation generates electrical power and in the wake of which, in the case of at least one wake direction, a second wind energy installation is present, wherein

-said wind farm is configured for implementing a method according to any one of claims 1 to 9, and/or

-comprising a control device according to claim 10.

Technical Field

The invention relates to a method for operating a wind energy installation, in the wake of which a second wind energy installation is present in the case of at least one wake direction; a control device for operating the wind power installation; and a wind farm having a first wind energy device and a second wind energy device.

Background

Wind power installations are known in principle, which generate electrical power from the wind. Wind power installations generally relate to horizontal-axis wind power installations, in which the rotor axis is oriented substantially horizontally and the rotor blades sweep a substantially vertical rotor surface. In addition to the rotor arranged at the nacelle, the wind energy installation usually also comprises a tower on which the nacelle with the rotor is arranged rotatably about a substantially vertically oriented axis. The rotor typically includes three rotor blades. Rotor blades are elongate components, which are usually manufactured from fibre-reinforced plastic.

Wind power installations are not usually built individually, but rather with at least one further wind power installation, in particular with a plurality of wind power installations, in a composite structure. This collection of wind energy installations is also referred to as a wind farm. The wind energy installations of the wind farm may influence each other. This is for example the case: one wind energy installation is aerodynamically shielded by another wind energy installation.

An aerodynamic blockage is achieved if the wind energy installation located in the Lee side (Lee) is in the wind shadow of the wind energy installation located in the windward side (Luv). This wind shadow is also known as Wake (Wake) or Wake (Nachlauf). Wind energy installations in the wake do not usually provide the power that is usual for a specific wind speed. It also generally occurs that a wind power installation in the wake does not reach its rated power, or does not reach its rated power until later than the undisturbed wind speed.

The power of the wind farm should therefore be determined taking into account the individual power of the wind energy installation, wherein the wake effect should be taken into account. Thus, the aim is not generally to optimize individual wind energy installations in terms of their power individually, but rather to optimize such wind farms. Therefore, the optimization problem on which it is based should primarily maximize the power of the wind farm.

In this maximization problem, a series of boundary conditions are to be taken into account, in particular the increased load of one wind energy installation in the wake of another wind energy installation due to the increased turbulence. In particular, the loads occurring at a plurality of wind energy installations are taken into account such that they do not exceed a maximum design load.

Disclosure of Invention

It is therefore an object of the present invention to provide a method for operating a wind power installation, a control device for operating a wind power installation, and a wind farm with a first wind power installation and a second wind power installation, which reduce or eliminate one or more of the disadvantages mentioned. The object of the invention is, inter alia, to propose a solution for improving the electric power of a wind farm.

According to a first aspect, the object mentioned at the outset is achieved by a method for operating a first wind power installation having a rotor with rotor blades which can be adjusted with a pitch angle, which first wind power installation generates electrical power and in the wake thereof, in the case of at least one wake wind direction, a second wind power installation is present, comprising the following steps: in a normal operation substantially unaffected by the wake, the first wind energy plant is operated with a first pitch characteristic curve, and in a wake operation affected by the wake, the first wind energy plant is operated with a second pitch characteristic curve, wherein the first pitch characteristic curve represents a first variation of the pitch angle with respect to the electrical power and the second pitch characteristic curve represents a second variation of the pitch angle with respect to the electrical power, wherein for at least one range of the electrical power the pitch angle of the second pitch characteristic curve is larger than the pitch angle of the first pitch characteristic curve.

The present invention is therefore particularly concerned with the realization that wind energy installations which are in the wake are not operated in a manner which differs from previous strategies, but rather that the wind energy installation which causes the wake is operated in a manner which differs from previous strategies. The method thus enables a maximization of the annual energy production of the second wind energy plant, in particular in compliance with auxiliary conditions, such as compliance with a maximum thrust coefficient or the intensity of turbulence affecting the wake.

The second wind energy installation is in the wake of the first wind energy installation if wind blows from at least one wake direction. The wake wind direction is preferably defined as a wind direction range, e.g. a wind direction range comprising about 15 degrees, wherein the wind direction range may depend on the model used. The wake is characterized in particular by: the second wind power installation is aerodynamically influenced, in particular shielded, by the first wind power installation.

Thus, the second wind energy plant is in the wake of the first wind energy plant if wind blows from at least one wake wind direction. If the second wind energy installation is in the wake of the first wind energy installation, the aerodynamic conditions at the second wind energy installation change compared to the flow situation unaffected by the first wind energy installation. If the second wind energy installation is not substantially in the wake of the first wind energy installation, the state is said to be unaffected by the wake (nachlauffrei). If the second wind energy installation is in the wake of the first wind energy installation, the state is said to be affected by the wake (nachlaufbelastet).

In normal operation, which is substantially unaffected by the wake, the first wind power installation is operated with the first pitch characteristic. If the second wind power installation is influenced by the wake, i.e. is in the wake of the first wind power installation, the first wind power installation is operated with the second pitch characteristic in wake operation.

The first pitch characteristic curve represents a first curve of change of pitch angle with respect to electrical power. Preferably, the pitch characteristic curve comprises a defined pitch angle for each value of electrical power. Similarly, the second pitch characteristic curve represents a second curve of the pitch angle with respect to the electrical power. Thus, the second pitch characteristic curve associates each electrical power with a defined pitch angle similar to the first pitch characteristic curve. The correlation is preferably determined for a defined span of electrical power, in particular for each electrical power which can occur during operation of the wind energy installation, for example between 0kW and the rated power.

Preferably, the first pitch characteristic curve and the second pitch characteristic curve substantially coincide with each other up to a first power threshold of the electrical power, and the pitch angle of the second pitch characteristic curve is greater than the pitch angle of the first pitch characteristic curve for electrical power exceeding the first power threshold.

Thus, preferably up to the first power threshold of the electric power, the first pitch characteristic and the second pitch characteristic substantially coincide with each other. Mutually consistent means, in particular, that the pitch angle of the first pitch characteristic curve and the pitch angle of the second pitch characteristic curve are substantially the same for substantially arbitrary electrical power below the power threshold. In other embodiments, the first pitch characteristic and the second pitch characteristic may also be different from each other over the full range.

Substantially mutually identical means, in particular, that for a defined electrical power the pitch angles differ from one another by less than 30%, 20% or 10% of the first pitch characteristic curve and the second pitch characteristic curve. This is in contrast to the practice used today in some wind farms, which generally proposes that the pitch angle in wake operation affected by the wake is substantially increased overall in order to reduce the load caused by the eddy currents. For example, the pitch angles are set to 5 °, 6 ° or 6.5 ° in total and/or increased by more than 2 °, 3 ° or 4 °. However, in this way, in the range below the first power threshold value, the power of the wind energy installation is not unnecessarily reduced, so that the power of the wind farm is not unnecessarily reduced.

Furthermore, it is preferably provided that the pitch angle of the second pitch characteristic curve is greater than the pitch angle of the first pitch characteristic curve if the electrical power of the first wind energy installation exceeds the first power threshold value. This means that for a specific electrical power which is greater than the first power threshold value, the pitch angle in wake operation which is influenced by the wake is greater than the pitch angle to be set in normal operation which is not influenced by the wake. If the second wind energy installation is, for example, substantially unaffected by the wake, the first wind energy installation is operated with the first pitch characteristic. In this case, for example, a pitch angle of 2 ° can be set at 1500kW of power, wherein this of course depends on the rated power of the wind energy installation and other design parameters.

However, if the second wind energy installation is in the wake of the first wind energy installation, the first wind energy installation is operated with the second pitch characteristic curve. In this case, for the same exemplary wind energy installation, a pitch angle of approximately 4 ° is set, for example, at a power of 1500 kW. It is evident therefrom that at an electrical power exceeding the first power threshold, the pitch angle of the second pitch characteristic curve is larger than the pitch angle of the first pitch characteristic curve.

In this way, it is possible to adjust the second wind power installation in the normal operation of the first wind power installation, since the turbulence caused by the first wind power installation in the windward side is so strong that the second wind power installation is adjusted from a specific electrical power and/or from a specific wind speed. This is taken into account by the second pitch characteristic. In the range of lower electrical power and/or lower wind speeds, such regulation is generally not required, since the turbulence occurring at the second wind energy plant does not generally exceed the maximum permissible design turbulence.

A preferred embodiment variant of the method provides that, for electrical power below the first power threshold value, the pitch angle of the first pitch characteristic curve and the pitch angle of the second pitch characteristic curve are substantially identical, and/or wherein the change curve of the first pitch characteristic curve and/or the change curve of the second pitch characteristic curve have substantially no slope until the first power threshold value is exceeded.

For example, in the range below the first power threshold, the first pitch characteristic curve defines a pitch angle of 2 ° for 500kW of electrical power. In this case, the second pitch characteristic likewise has a pitch angle of 2 ° for 500kW of electrical power in the range below the first power threshold.

The change curve of the first pitch characteristic curve without slope is characterized in particular in that the pitch angle remains substantially constant even when the electrical power is increased. The pitch angle may be, for example, 2 °. The same basically applies for the second pitch characteristic curve.

According to a further preferred embodiment of the method, it is provided that the first wind power installation and/or the second wind power installation have a maximum permissible thrust coefficient as a function of the wind speed, wherein the pitch angle of the second pitch characteristic curve has such a profile that the thrust coefficient occurring at the wind power installation does not substantially exceed the maximum permissible thrust coefficient. The maximum thrust coefficient may for example be derived from the turbulence intensity affected by the wake. In other words, the second pitch characteristic has a profile such that the coefficient of thrust exerted by the wind energy installation in the windward side is not higher than the maximum coefficient of thrust from the wind energy installation in the leeward side, which is thus influenced by the wake, which is limited by the turbulence intensity.

It is furthermore preferred that the second wind power installation has a maximum permissible turbulence intensity as a function of the wind speed, wherein the pitch angle of the second pitch characteristic curve has such a profile that the turbulence intensity occurring at the wind power installation does not substantially exceed the maximum permissible turbulence intensity.

Maximum permissible turbulence intensity TI_maxDetermined according to IEC standard 61400-1:

TI_WKthe wind types are classified into A, B and C types, in relation to the wind type. TI_WKFor example, it may be 0.12, 0.14 and 0.16. For wind energy installations affected by the wake, the velocity v is calculated by means of a wake model, for example, the wake model of Jensen, Qian, Port-Agel. The wake model generally requires the thrust coefficient of the installation in the windward side, which can be calculated, for example, by means of Blade Element Momentum Theory (BEM). Therefore, as a boundary condition for maximizing the electric power of the wind farm, it is generally established: the turbulence at the wind energy installation affected by the wake is less than the maximum permissible turbulence TI_max。

The invention is based on the recognition, inter alia, that the turbulence-related auxiliary conditions are equivalent to the thrust coefficient of the wind power plant affected by the wake being smaller than the maximum permissible thrust coefficient. Depending on the model, other variables should be considered for the evaluation, and the tip speed ratio may be contained in an inequality, for example.

A preferred refinement of the method is characterized in that for electrical power exceeding the first power threshold value and below the second power threshold value, the pitch angle of the first pitch characteristic curve is substantially constant and the pitch angle of the second pitch characteristic curve increases, preferably continuously, particularly preferably linearly, wherein further variation curves are also possible.

Thus, between the first power threshold and the second power threshold, the pitch angle of the first pitch characteristic curve is substantially constant, independent of the electrical power. Between the first power threshold and the second power threshold, the pitch angle of the second pitch characteristic curve increases as the electrical power increases.

A further preferred refinement of the method is characterized in that for electrical power exceeding the second power threshold, the first pitch characteristic has a positive slope which is preferably smaller than the slope of the second pitch characteristic.

In the preferred refinement, the second pitch characteristic curve preferably has a first constant portion of the pitch angle below the first power threshold, a rising portion between the first power threshold and the third power threshold, and also a constant portion from the third power threshold, wherein further variation curves are also advantageous.

It is furthermore preferred that the pitch angle of the second pitch characteristic curve is substantially constant for electrical power exceeding a third power threshold value larger than the first power threshold value, and preferably takes a value between 4-8 °, in particular between 6-7 °.

Furthermore, it is preferred that the first power threshold value is between 70% and 80% of the rated power of the first wind power installation.

In particular, the power threshold value can be identified by a kink in the pitch angle power characteristic curve.

According to a further aspect, the object mentioned at the outset is achieved by a control device for operating a first wind energy installation having a rotor with rotor blades which can be adjusted with a pitch angle, which wind energy installation generates electrical power, and in the wake of which a second wind energy installation is present in the case of at least one wake direction, wherein the control device is set up to operate the first wind energy installation with a first pitch characteristic curve in normal operation substantially unaffected by the wake and with a second pitch characteristic curve in wake operation affected by the wake, wherein the first pitch characteristic curve represents a first variation of the pitch angle with respect to the electrical power and the second pitch characteristic curve represents a second variation of the pitch angle with respect to the electrical power, wherein for at least one range of the electrical power, the pitch angle of the second pitch characteristic is greater than the pitch angle of the first pitch characteristic.

According to a further aspect, the object mentioned at the outset is achieved by a wind farm with a first wind power installation having a rotor with rotor blades which can be adjusted with a pitch angle, which generates electrical power, and in the wake of which a second wind power installation is present in the case of at least one wake wind direction, wherein the wind farm constitutes a method for carrying out the method according to one of the above-described embodiments and/or comprises a control device according to the above-mentioned aspect.

For further advantages, implementation variants and implementation details of further aspects and possible modifications thereof, reference is also made to the above description of corresponding features and modifications of the method for operating the first wind energy installation.

Drawings

Preferred embodiments are exemplarily illustrated in accordance with the accompanying drawings. The figures show:

FIG. 1 shows a schematic three-dimensional view of an exemplary embodiment of a wind energy plant;

FIG. 2 shows a schematic view of an exemplary embodiment of a wind farm;

FIG. 3 shows a schematic variation of a pitch characteristic;

FIG. 4 shows a schematic variation curve of the thrust coefficient;

FIG. 5 shows a schematic variation curve of the thrust coefficient; and

fig. 6 shows an exemplary method.

Detailed Description

In the figures, identical or substantially functionally identical or functionally similar elements are denoted by the same reference numerals.

Fig. 1 shows a schematic representation of a wind energy installation 100. The wind energy installation 100 has a tower 102 and a nacelle 104 on the tower 102. An aerodynamic rotor 106 with three rotor blades 108 and a fairing 110 is provided at the nacelle 104.

During operation of the wind power installation, the aerodynamic rotor 106 is set into rotational motion by the wind, so that an electrodynamic rotor or rotor part of the generator, which is coupled directly or indirectly to the aerodynamic rotor 106, is also rotated. A generator is disposed in nacelle 104 and generates electrical energy. A pitch angle 114 of rotor blade 108 may be changed by a pitch drive 116 at a rotor blade root of the corresponding rotor blade 108.

The wind power installation 100 further comprises a control device 118, which is set up to operate the wind power installation 100 with a first pitch characteristic in normal operation, in which the wind power installation is substantially unaffected by a wake, and to operate the wind power installation 100 with a second pitch characteristic in wake operation, in which the wake is affected. The first pitch characteristic curve represents a first change in pitch angle with respect to electrical power, and the second pitch characteristic curve represents a second change in pitch angle with respect to electrical power. The first pitch characteristic and the second pitch characteristic substantially coincide with each other up to a first power threshold of the electrical power. For electrical power exceeding the first power threshold, the pitch angle of the second pitch characteristic curve is greater than the pitch angle of the first pitch characteristic curve.

Fig. 2 shows a schematic view of an exemplary embodiment of a wind farm 112. Fig. 2 shows a wind farm 112 with three exemplary wind energy installations 100a, 100b, 100 c. The three wind power installations 100a, 100b, 100c represent in principle any number of wind power installations of the wind farm 112. The wind power installations 100a, 100b, 100c are supplied with their electrical power, i.e. in particular the generated current, via the electrical field network 114. The respective generated currents or powers of the individual wind energy installations 100a, 100b, 100c are summed up and, in most cases, a transformer 116 is provided, which up-converts the voltage in the electrical field in order to feed into a supply grid 120 at a feed point 118, also generally referred to as PCC. FIG. 2 is merely a simplified illustration of wind farm 112. The electric field network 114 may be configured differently, for example, as follows: for example, a transformer is also present at the outlet of each wind energy installation 100a, 100b, 100 c.

In the case of the indicated wind direction W, the wind power installation 100b is in the wake of the wind power installation 100 a. In this case, the wind power installation 100a is arranged in the windward side of the wind power installation 100 b. The wind power installation 100a is preferably operated at least temporarily in wake mode under the influence of a wake in which a wind power installation 100b is present in the wake of the wind power installation 100 a. This means, in particular, that the second pitch characteristic is provided for the operation. In the case of the wind direction W, the wind energy installation 100c is also in the wake of the wind energy installations 100a and 100 b.

Without limiting the generality, the wind energy installation 100a is also referred to below as a first wind energy installation 100a and the wind energy installation 100b is also referred to as a second wind energy installation 100 b.

Fig. 3 shows a schematic profile of a pitch characteristic. The electrical power 200 of the wind power installation furthest to the front, i.e. not in the wake, is plotted on the abscissa. The pitch angle 202 of the wind energy installation 100a is plotted on the ordinate. If the wind power installation 100a is in normal operation without wake effects, i.e. if, depending on the wind direction, none of the wind power installations 100b, 100c is in the wake of the wind power installation 100a, a first pitch characteristic is used for the wind power installation 100 a. I.e. in particular if the wind blows from a wind direction different from the wind direction W shown in fig. 2, the first wind energy device 100a is in normal operation unaffected by the wake.

Also in fig. 3, a conventional pitch characteristic 206 for wake operation affected by the wake is provided. The conventional pitch characteristic 206 provides that the pitch angle is generally adjusted to a higher value in order to reduce the thrust coefficient as long as the wind energy installation is in the wake of another wind energy installation.

The effect of the larger pitch angle and the resulting reduction in the thrust coefficient is seen in particular in fig. 4. Fig. 4 shows a variation of undisturbed wind speed 210 on the ordinate, for example in m/s, with respect to thrust coefficient 212 on the abscissa for different pitch angle variation curves. In the following more accurately described diagram of fig. 4, the pitch angle change curve shown below represents such a change curve for a larger pitch angle. As can be seen in particular in fig. 4, the larger the pitch angle, the smaller the thrust coefficient.

Alternatively to the conventional pitch characteristic 206, a second pitch characteristic 208 is shown in fig. 3, which substantially corresponds to the first pitch characteristic 204 up to a first power threshold 207 of the electrical power 200. For electrical power 200 exceeding the first power threshold 207, the pitch angle 202 of the second pitch characteristic 208 is greater than the pitch angle 202 of the first pitch characteristic 204.

The first pitch characteristic 204 may be, for example, a typical pitch characteristic that presets an increasing pitch angle at least from the nominal power being reached. In other cases, not only the first pitch characteristic 204 but also the second pitch characteristic 208 may be provided with a pitch angle that increases in the partial load range, for example. For example, a linear increase up to the rated power and a non-linear increase from the rated power can be provided.

The second pitch characteristic for operating the first wind power installation 100a, which is caused in the wake operation of the wind power installation 100b, is influenced by the wake, a high electrical power can be generated in the partial load range below the first power threshold 207, since the thrust coefficient is usually small here or a greater thrust coefficient is permitted here. At electric power exceeding the first power threshold 207, and thus generally also at the corresponding wind speed, the pitch angle of the second pitch characteristic curve 208 is increased in order to reduce the thrust coefficient. This makes it possible, for example, to make full use of the still existing thrust reserve of the wind power installation 100b in the wake, i.e. up to the maximum permissible load, which in turn increases the output of the wind power installation 100 b.

Fig. 4 shows a schematic change curve of the thrust coefficient. The wind speed 210 is plotted on the abscissa, for example in m/s. The thrust coefficient 212 is plotted on the ordinate. The maximum allowable thrust coefficient 216 is also plotted. It can be seen here that up to a certain wind speed 210, the maximum thrust coefficient 216 is always greater than the thrust coefficient that occurs for a certain pitch value. That is, nearly arbitrary pitch angles can be adjusted in the low wind speed range, independent of the maximum allowable thrust coefficient, so that the focus can be almost completely put on generating maximum electrical power. However, as wind speed increases, the thrust coefficient set by the power-optimized pitch angle may exceed the maximum thrust coefficient 216. In this case, the pitch angle should be adjusted accordingly, so that the thrust coefficient occurring does not substantially exceed the maximum thrust coefficient.

Fig. 5 shows selected variation curves of the thrust coefficient in fig. 4. Wind speed is plotted on the abscissa, for example in m/s, and thrust coefficient 222 is plotted on the ordinate. Thrust coefficient curve 228 represents an exemplary thrust coefficient for a pitch angle corresponding to pitch characteristic curve 206 of FIG. 3. The thrust coefficient curve 224 for the second pitch characteristic curve 208 shows that a greater thrust coefficient is always achieved in the partial load range. This generally results in greater electrical power being generated. The thrust coefficient curve 224 for the second pitch characteristic curve 208 is just closer to the curve of the maximum allowable thrust coefficient 226 in the part load range.

Fig. 6 shows an exemplary method. In step 300, the first wind power installation 100a and the second wind power installation 100b are each operated with the first pitch characteristic 204 in normal operation without wake effects. In this case, therefore, neither wind power installation 100a, 100b is in the shadow of the other wind power installation. In particular, the wind power installation 100b is not substantially in the shadow of the wind power installation 100a, i.e. in the wake. If the wind is now turning such that the wind energy installation 100b is in the wake of the wind energy installation 100a, in step 302 the first wind energy installation 100a is operated with the second pitch characteristic 208 in wake operation affected by the wake.

Thus, in step 302, first wind energy device 100a is operated with second pitch characteristic curve 208. The second pitch characteristic 208 represents a second curve of the pitch angle with respect to the electrical power, wherein the second pitch characteristic 208 preferably substantially coincides with the curve of the first pitch characteristic 204 up to a first power threshold 207 of the electrical power, whereas the pitch angle of the second pitch characteristic 208 is greater than the pitch angle of the first pitch characteristic 204 in the event of exceeding the first power threshold 207.

List of reference numerals

100a, 100b, 100c wind energy plant

102 tower

104 nacelle

106 rotor

108 rotor blade

110 fairing

112 rotor blade longitudinal axis

114 pitch angle

116 pitch drive

118 control device

200 electric power

202 pitch angle

204 first pitch characteristic curve

206 conventional pitch characteristic curve

207 first power threshold

208 second Pitch characteristic Curve

210 wind speed in m/s

212 coefficient of thrust

214 thrust coefficient curves for multiple pitch angles

216 maximum allowable thrust coefficient

220 wind speed in m/s

Coefficient of thrust 222

224 thrust coefficient curve for the second pitch characteristic curve 208

226 maximum allowable thrust coefficient

228 thrust coefficient curve for conventional pitch characteristic curve 206

W wind direction