Claims:We claim:

1. A method of controlling at least one wind turbine (10), wherein at least one parameter value of the wind turbine (10) is determined or received, characterized by the following steps:

• determining wind speed values and/or wind shear values from the at least one parameter value of the wind turbine (10);

• entering the wind speed values and/or wind shear values, and optionally at least one parameter value of the wind turbine (10) as entry values into a simulation software, which, based on said entry values, calculates load values, in particular load consumption values of the wind turbine (10), preferably for a time domain; and

• controlling the at least one wind turbine (10) based on the calculated load values.

2. The method according to claim 1, characterized in that the calculated load values are compared to predefined load values allowed, preferably for the time domain, and that the at least one wind turbine (10) is controlled based on comparison values.

3. The method according to claim 1 or 2, characterized in that, based on the calculated load values, the wind turbine (10) is controlled to run in an overrated operational mode or in a de-rated operational mode.

4. The method according to any one of claims 1 to 3, characterized in that the at least one parameter value of the wind turbine (10) is determined by measuring the at least parameter using a sensor or by deducing the at least one parameter from a sensed parameter.

5. The method according to any one of claims 1 to 4, characterized in that, as the at least one parameter value, the power and/or the rotational speed and/or the pitch angle and/or the wind direction and/or the air density and/or the blade moments is/are determined.

6. The method according to any one of claims 1 to 5, characterized in that the simulation software comprises a Multi-Body System, and that the determined wind speed values and/or wind shear values, and optionally at least one parameter value of the wind turbine are entered as entry values into said Multi-Body System.

7. The method according to any one of claims 1 to 6, characterized in that a control device (19) is allocated to said at least one wind turbine (10), wherein calculation of the load values is performed in said control device (19) and wherein, optionally the calculated load values are stored in a storage device.

8. The method according to any one of claims 1 to 7, characterized in that the method is performed for a windfarm (20) having two or more wind turbines (10) and a central-windfarm control device (21), which controls the wind turbines (10), wherein calculation of the load values for the wind turbines (10) is performed in said central-windfarm control device (21), or wherein said central-windfarm control device (21) receives load values from each wind turbine (10).

9. The method according to claim 8, characterized in that in an evaluation step, the central-windfarm control device (21) evaluates the calculated load values for each wind turbine (10) against calculated load values of the other wind turbines (10) and that the central-windfarm control device (21) controls the loads distribution to the wind turbines (10) based on the evaluation step.

10. A computer program product, which enables a data processing device, once the computer program product is executed on the data processing device, and is preferably stored in a storage device of the data processing device, to perform a method of controlling at least one wind turbine based on calculated load values, in particular load consumption values, according to any one of claims 1 to 9.

11. A control device (19; 21) of a wind turbine, said control device (19; 21) comprising a device for determining at least one parameter value of the wind turbine (10) and/or an interface for receiving at least one parameter value of the wind turbine (10), a device for determining wind speed values and/or wind shear values from the at least one parameter value of the wind turbine (10); a simulation software running on said control device (19; 21), said simulation software being provided for calculating load values, in particular load consumption values of the wind turbine (10), preferably for a time domain, based on entry values defined by said wind speed values and/or wind shear values, and optionally at least one parameter value of the wind turbine (10), and a control unit for controlling the at least one wind turbine (10) based on the calculated load values.

12. The control device according to claim 11, characterized in that the control device (19; 21) is provided in such a way that it is capable of executing the method according to anyone of claims 1 to 9, and/or that the control device (19; 21) comprises a data processing device or an interface to an external data processing device, wherein a computer program product according to claim 10 is executed on said data processing device.

13. A wind turbine (10), said wind turbine (10) comprising a tower (12), a nacelle (11) being mounted on top of the tower (12), said nacelle (11) incorporating a drive train of the wind turbine (10), and a rotor (14) being mounted to the nacelle (11), said rotor (14) comprising a number of rotor blades (16, 17, 18), characterized in that the wind turbine (10) further comprises a control device (19; 21) according to claim 11 or 12, or that the wind turbine (10) comprises means for performing the method according to any one of claims 1 to 9.

14. The wind turbine according to claim 13, characterized in that the wind turbine (10) comprises at least one sensor for determining at least one parameter value of said wind turbine (10), in particular for determining the power and/or the rotational speed and/or the pitch angle and/or the wind direction and/or the air density and/or the blade moments.
, Description:FIELD OF THE INVENTION

The present invention generally relates to a wind turbine. More particularly, the present invention relates to a method of controlling a wind turbine. Furthermore, the present invention is directed to a computer program product, to a control device of a wind turbine and to a wind turbine itself.

BACKGROUND

Wind turbines of the horizontal type, which means that the wind turbines comprise a horizontal rotor axis and a rotor being directed towards the wind, are known. Such wind turbines generally comprise a nacelle incorporating a drive train. In general, the drive train comprises at least a generator device. The nacelle is mounted to a tower. The rotor with a number of rotor blades, particularly with three rotor blades, is connected to the drive train via a hub, to which the rotor blades are mounted. The rotor rotates around its rotational rotor axis. According to one type of wind turbines, the rotor blades are adjustably mounted to the hub. This is realized by means of respective pitch drives, said pitch drives being part of a pitch system. The pitch system, which is generally known in the prior-art, participates in the control of the rotor speed to given set points. In particular, the rotor speed is controlled by the electrical load of the generator device and by the pitch angle. By means of the pitch drives, the rotor blades may be moved about rotor blade axes into different pitch positions.

Quite often, wind turbines are operated as parts of a windfarm, which comprises a plurality of such wind turbines. The output of each turbine is determined and one or more wind turbines are controlled in such a way that the output power of one or more wind turbines is reduced if the total output exceeds the rated output of the windfarm. However, at a given time, not all of the wind turbines may be operating at full capacity. Some may be shut down for maintenance and some may be experiencing less than ideal wind conditions. For that reason, it might be desirable to at least temporarily boost the output of one or more of the wind turbines to increase the total output of the windfarm. However, such boosting risks damaging the wind turbines, due to fatigue phenomena for example.

When a wind turbine is manufactured, it normally gets certified and the life cycle of the wind turbine is fixed according to its certificate. The wind turbine design is based on fatigue calculations. Such fatigue calculations are made once for wind turbine certification and results of the calculations are included in the certificate. Some wind turbines cannot operate over rated power, because the damage contribution cannot be estimated, although the certified fatigue loads are usually higher than the wind turbines are exposed to on-site. According to the certificate, the life cycle of the wind turbine is fixed, no matter what damage the wind turbine has actually experienced. Therefore, the possible allowable damage for which the wind turbine is certified, is not exhausted in most cases.

As discussed, if one or more wind turbines in a windfarm have to be shut-down, for maintenance reasons for example, or de-rated, other wind turbines might need to be boosted on windfarm level. A temporal additional damage on single wind turbine level by uprating can be compensated, if the accumulated damage of the wind turbine has been taken into account. Outages for example have favorable mitigations on fatigue. Some wind turbines do have less damage than others and can be preferably overrated or just less de-rated in a certain timeframe and still may not cause much damage in a given life cycle of the wind turbine for which that wind turbine is designed for. Some wind turbines are running de-rated as power limit at grid for windfarm may be less than sum of rated power that all wind turbines in the windfarm can deliver.

In order to avoid any damages on a wind turbine due to overrating, it might be an option to conservatively dimension said wind turbine. Even though such an approach may solve the abovementioned problems, it leads to disadvantages in the form of higher costs.

A known solution, which is disclosed in WO 2013/044925 A1 describes a windfarm, which comprises a plurality of wind turbines, each having a rated output and being under the control of a windfarm controller. The windfarm also has a rated output which may be over-rated under certain circumstances.

OBJECT OF THE INVENTION

Starting from the aforementioned general prior-art, it is the object of the present invention to provide a solution in the field of wind turbines, which avoids the aforementioned drawbacks. In particular, it is the object of the present invention to provide an easy solution of controlling a wind turbine based on an individual, in particular real time, load estimation.
According to the present invention, the object is solved by the method with the features according to independent claim 1, which is the first aspect of the invention, by the computer program product with the features according to independent claim 10, which is the second aspect of the invention, by the control device with the features according to independent claim 11, which is the third aspect of the present invention, and by the wind turbine with the features according to independent claim 13, which is the fourth aspect of the invention. Further features and details of the invention become apparent from the dependent claims, from the description as well as from the drawings. Therein, features and details which are described in connection with one aspect according to the invention also apply with respect to this disclosure in their entirety to the other aspects according to the invention, so that any statements made with respect to one aspect of the invention also apply to their full extent to the other aspects of the invention, and vice versa.

The present invention is generally directed to a solution of controlling at least one wind turbine, preferably a windfarm, based on calculated loads, in particular on a calculated load consumption, preferably in the field of fatigue. According to a preferred embodiment, the present invention is provided in the field of load consumption control in at least one wind turbine, preferably in a windfarm. An individual real time load estimation of a wind turbine maximizes the energy output within the given load limits during the wind turbine’s life. The present invention can optimize the usage of the wind turbines based on the respective damage level.

According to one preferred embodiment, the present invention is used in connection with a single wind turbine. According to another preferred embodiment, the present invention is used in connection with a windfarm, said windfarm comprising a number of wind turbines.

Normally, load levels cannot be compared. However, with the present invention, boundary conditions are fed back into the same model, on which the certification loads are based.

In particular, the underlying concept of the present invention is a load consumption control, preferably of lifetime fatigue, on wind turbine control level or on windfarm control level using, among other features, a wind estimation and a simulation procedure, said simulation procedure preferably being based on a Multi-Body System simulation. For realizing this solution no additional measurement hardware is required. Instead, the load consumption is calculated by use of a computer implemented simulation procedure, which is performed by a simulation software incorporating at least one suitable simulation algorithm, said simulation software running in a data processing device. With this respect, the simulation can be seen as some kind of a virtual sensor for virtually sensing at least one load relevant component, preferably all load relevant components, at the wind turbine.

According to one basic principle of the present invention, the wind is estimated from at least one parameter value of the wind turbine. The estimated wind is fed into simulation software which preferably includes a Multi-Body System. During a simulation procedure, load values are determined which may not, otherwise, get measured in the field. This will be described in more detail further below. Those load values that have been determined are used for controlling the wind turbine or a windfarm comprising a number of such wind turbines.

Common approaches measuring with sensors in drivetrain and machinery components will give a loads spectrum for instant in highly loads spectra differing a lot to simulation routine. Furthermore, loads retrieved from measuring comes with calibration of loads which are underlying assumptions that cannot be fully validated completely or only with a certain accuracy.

The approach according to the present invention provides the greatest possible comparability of load levels in the fleet and design loads, which the certifications are based on. The only source of discrepancy to compare the loads to the certified model is reduced to estimated wind input utilized for the turbine model. Following force and moment flows through drivetrain and machinery components and other structural components, for example mainframe and tower, are subjected to the same structural model and control model as in the certification. Accordingly, the approach offers a much higher comparability to control the consumed loads according to the designed loads from certification.

SUMMARY OF THE INVENTION

The present invention according to its four aspects is directed to the technical field of wind turbines, in particular to the technical field of horizontal wind turbines. Such wind turbines are generally known in the prior-art.

According to a preferred embodiment, the wind turbine comprises a nacelle which incorporates a drive train. The drive train transmits the rotor speed to the generator where it is converted into electric energy. In particular, the drive train is the mechanical energy transmitting line starting from the hub of the rotor right up to the generator. The wind turbine comprises a rotor being connected to said drive train, said rotor preferably comprising a hub and a number of rotor blades, preferably three rotor blades, said rotor blades being mounted to said hub. The rotor, which is directed towards the wind, is pivotally mounted around a rotational rotor axis to the drive train. In order to transform the rotational energy of the rotor into electric energy, the drive train, to which the rotor of the wind turbine is mounted, comprises a number of different components. One of these components is a generator device. The generator device generates electric energy. For this purpose, the generator device preferably comprises a stator component and a rotor component, said rotor component being coupled to the generator shaft. The nacelle is mounted at the top of a tower of said wind turbine. At its lower base end, the tower is anchored to the ground by means of a foundation.

In particular, each rotor blade is adjustably mounted on the hub. This is realized by means of a pitch drive, said pitch drive being part of a pitch drive unit, which in turn is part of a pitch system. The pitch system, which is generally known in the prior-art, participates in the control of the rotor speed to given set points. In particular, the rotor speed is controlled by the electrical load of the generator device and by the pitch angle. By means of the pitch drives, the rotor blades may be moved about rotor blade axes into different pitch positions, said rotor blade axes extending in an axial direction of the rotor blade. A rotor blade having an adjustable pitch can be particularly understood in such a manner, that the angle of attack of the rotor blade, which may be defined as the pitch angle, can be adjusted or is provided in an adjustable manner, during a pitch-offset for example.

Quite often, such a wind turbine is part of a windfarm. A windfarm, which can be denoted as a wind park as well, comprises a group of wind turbines, which are generally arranged in the same location, said windfarm being used to produce electricity. Each wind turbine may comprise its own individual control device. In addition, or as an alternative the windfarm may comprise one central-windfarm control device. The present invention is not limited to a specific number of wind turbines for a windfarm. Nevertheless, a windfarm comprises at least two wind turbines.

The present invention will now be explained in detail and with reference to the different aspects of the present invention.

According to the first aspect of the present invention, the object is solved by a method comprising the features of independent claim 1.

According to the first aspect, the invention is directed to a method of controlling at least one wind turbine. For that reason, it is preferred that the at least one wind turbine is allocated to a control device, said control device being described in more detail with regard to the third aspect of the invention further below. Therefore, at this point, full reference is also made to the disclosure of the third aspect as well. According to a preferred embodiment, the control device of the wind turbine is individually allocated for controlling one wind turbine only. According to a different embodiment, if the wind turbine is part of a windfarm and the windfarm comprises one central-windfarm control device, the central-windfarm control device is provided for controlling all of the wind turbines of the windfarm.

According to this method, in a first step, which is a first determination step, at least one parameter value of the wind turbine is determined. According to a preferred embodiment, the at least one parameter value is directly determined by use of a suitable device for determining parameter values, a suitable sensor for example. According to a different embodiment the at least one parameter value is received from a remote location. In this case, a suitable interface is provided for receiving the at least one parameter value.

In particular, a parameter value according to the present invention is a value being characteristic for the wind turbine, in particular for at least one component of the wind turbine, or characterising the wind turbine, in particular at least one component of the wind turbine. The present invention is not limited to specific types of parameter values. According to preferred embodiments, the power of the wind turbine, in particular the power which is generated by the generator device of the wind turbine and/or the rotational speed of the rotor and/or the pitch angle of the rotor blades and/or the wind direction and/or the air density and/or the blade moments of the rotor blades and/or any combination of the aforementioned parameter values is/are determined, preferably measured, as the at least one parameter value.

According to this first step, at least one parameter value of the wind turbine is determined. However, the present invention is not limited to a specific number of parameter values, which are determined. Therefore, for performing the method according to the present invention, two or more parameter values can simultaneously be determined as well.

The determination of the at least one parameter value can be performed in different ways. According to a preferred embodiment, the at least one parameter value of the wind turbine is determined by measuring the at least parameter using a sensor. A wind turbine generally comprises a number of different sensors which are used in connection with the general operation of the wind turbine. In particular, such sensors are used further for measuring values of the specific wind turbine parameters as mentioned above. Preferably, the sensed parameter values are transmitted from the sensors to a control device, where the further progress of the method takes place. In such a case, the control device preferably comprises at least one interface for receiving such parameter values measured by the respective sensors.

According to a different preferred embodiment, the at least one parameter value of the wind turbine is determined by deducing or calculating the at least one parameter value from a sensed parameter. This is preferably performed in a control device of the wind turbine. In such a case the parameter value is preferably generated during a computer implemented calculation procedure by means of a suitable determination algorithm.

According to a preferred embodiment, the parameter values is determined by use of at least one blade sensor. Such blade sensors cover loads which can be converted in an overlapping moment, around nick and tilt axes for example,

The method according to the present invention is further characterized by the following steps:

In a next step, which is a second determination step, wind speed values and/or wind shear values are determined from the at least one parameter value of the wind turbine. In particular, these values get calculated or deduced from the at least one parameter value. In particular, this step is performed in a state estimator device, a state estimator device of a model predictive control for example, and/or a wind estimator device and/or a shear estimator device respectively, which is/are preferably part of a control device of the wind turbine. In such a case, the wind speed values and/or the wind shear values are preferably generated or estimated during a computer implemented determination procedure by means of a suitable determination software and/or algorithm.

According to a preferred embodiment with regard to this second determination step, the wind, in particular the wind speed, is estimated, by use of a wind estimator for example. Alternatively, or in addition, the shear, in particular the wind shear, is estimated, by use of a shear estimator for example. Both, estimated wind speed and direction, are integral part of a state estimation. In particular, wind shear, which is sometimes referred to as the wind gradient, occurs when there is a change in the direction and/or speed of wind at a given distance, usually at short distances.

According to the aforementioned second determination step, the at least one parameter value, the power and/or rotational speed and/or pitch angle and/or wind direction and/or air density and/or the blade moments for example, is/are determined on the wind turbine. Based on these measurements, a wind speed, which preferably corresponds to the effective rotor equivalent wind speed, and/or the wind shear is determined, preferably deduced. According to a preferred embodiment, using an existing blade sensor system, the local wind velocity gradient, for example the vertical and horizontal shear, is determined.

According to a next step, which is a simulation step, the state values, in particular the wind speed values and/or wind shear values, and optionally at least one parameter value of the wind turbine are entered as entry values into a simulation software. The simulation software comprises at least one simulation algorithm. By use of the simulation software, a computer implemented simulation procedure is performed, said simulation procedure using the aforementioned entry values as starter values for the simulation. A suitable simulation procedure is described in more detail further below. According to a preferred embodiment, the second determination step, during which wind speed values and/or wind shear values are determined or estimated, can be performed by said simulation software as well. The simulation software, in particular the simulation algorithm being responsible for performing the simulation procedure, calculates, based on the entered entry values, load values, in particular load consumption values of the wind turbine, preferably for a defined time domain. Herein, the time domain is the analysis of mathematical functions, physical data or other types of data with respect to time.

Simulation software products as mentioned before are generally known in the prior-art. Common software products such as FLEX5, FAST, HAWC, BLADED and the like do have an aerodynamic routine and Multi-Body Systems. For example, the aerodynamic routine processes wind velocity distribution over the rotor and is connected to a Multi-Body System. This Multi-Body System returns speed performance and pitch angle and additionally load in all machine and component relevant coordinate systems used for design and dimensioning of the wind turbine.

As a result, the equipment of the wind turbine with sensors can be saved. Preferably, the simulation software should match to the software obtained for the wind turbine certificate.

Using the measurements and deduced values as virtual input for an online simulation allows the instantaneous calculation of the loads in time domain, in particular for respective periods of time, for a given time or time period and for the total duration of the wind turbine installation.

According to a preferred embodiment, the loads, the damage for example, can be determined using a classic loss calculation such as rainflow counting, Markov or load duration distribution and the like.

By use of a simulation software, loads of the wind turbine can get determined or estimated which cannot be measured in the field.

According to this simulation step, the determined wind speed values and/or wind shear values get implemented in the simulation software. Then, the simulation software performs a load simulation. In particular, loads get calculated. For example, a fatigue calculation takes place.

In a final step, which is a control step, the at least one wind turbine is controlled based on the calculated load values. Controlling of the wind turbine can take place in different ways. Some preferred embodiments are described in more detail further below.

According to a preferred embodiment, the calculated load values are compared to predefined load values, which are preferably allowed for the time domain, wherein the at least one wind turbine is controlled based on the comparison values. In particular, the calculated load values are compared to allowed loads, to allowed damages for example, with regard to the lifetime of the wind turbine. The load, the damage for example, is determined for the respective periods of time and for the total duration of the wind turbine installation. It is compared with the load, the damage for example, allowed for this operating period / lifetime so far. If the allowed load is not reached, the wind turbine can be operated with a higher rated output.

According to a preferred embodiment, based on the calculated load values, the wind turbine is controlled to run in an overrated operational mode, or in a de-rated operational mode. Generally, a wind turbine runs in standard rated, or in overrated, or in reduced rated (also referred to as de-rated) load operation. In particular, according to the method according to the present invention, a possible boosting/overrating or de-rating is calculated.

As explained above, the present invention is not limited to specific types of simulation software products. According to a preferred embodiment, the simulation software comprises a Multi-Body System, wherein the determined wind speed values and/or wind shear values, and optionally at least one parameter value of the wind turbine, are entered as entry values into said Multi-Body System. A general function of such a Multi-Body System has already been explained above. In particular, a Multi-Body System is the study of the dynamic behaviour of interconnected rigid or flexible bodies, each of which may undergo large translational and/or rotational displacements. A system to be analysed, the wind turbine or a component of the wind turbine in the present case, is subdivided into a number of bodies, the movement of which in relation to each other is described via joints, force elements, constraints and the like. As an important feature, Multi-Body System formalisms usually offer an algorithmic, computer-aided way to model, analyse, simulate and optimize the arbitrary motion of interconnected bodies. Multi-Body Systems per se are well known in prior-art.

The method according to the present invention can be used in connection with one single wind turbine only. In such a case, the wind turbine either stands alone or it is controlled independently from other wind turbines. Such a solution can be addressed as an isolated application for example. According to such an embodiment it is preferably provided, that a control device is allocated to said at least one wind turbine, wherein calculation of the load values is performed in said control device and wherein, optionally the calculated load values are stored in a storage device.

However, as explained above, the method according to the present invention can be used in connection with a windfarm as well, said windfarm comprising a plurality of wind turbines. In such a case, the method is preferably performed for a windfarm having two or more wind turbines and a central-windfarm control device which controls the wind turbines.

According to a preferred embodiment, the calculation of the load values for the wind turbines is performed in said central-windfarm control device. Or, according to a different preferred embodiment, said central-windfarm control device receives load values from each wind turbine. In both cases, the central-windfarm control device may perform a load management, a damage management for example, on windfarm level. Due to the calculation of loads for the different wind turbines, the central-windfarm control device may boost/overrate or de-rate different wind turbines of the windfarm regarding loads, preferably consumed loads, consumed damages for example, of each wind turbine. Optionally, the calculated load values are stored in a storage device being allocated to said central-windfarm control device.

In an evaluation step of the latter embodiment, the central-windfarm control device preferably evaluates the calculated load values for each wind turbine against calculated load values of the other wind turbines, and the central-windfarm control device controls the loads distribution to the wind turbines based on this evaluation step. The load information received by the central-windfarm control device for a wind turbine is available for the windfarm controller to evaluate it against experienced loads of other wind turbines of the windfarm. Based on the currently maximum permitted nominal load of the wind turbines in the windfarm, the windfarm controller optimizes the load distribution, the damage distribution for example, to the wind turbines within the windfarm.

According to the second aspect of the present invention the object is solved by the computer program product according to independent claim 10.

With regard to the configuration, to the performance and to the function of the computer program product according to the second aspect, full reference is also made to the general description of the invention above, and to the description of the other aspects of the invention as disclosed above and further below.

According to this second aspect, the invention is directed to a computer program product, which enables a data processing device, once the computer program product is executed on the data processing device, and is preferably stored in a storage device of the data processing device, to perform a method of controlling at least one wind turbine based on calculated load values, in particular load consumption values, in accordance with the method according to the first aspect of the invention.

According to the third aspect of the invention, the object is solved by the control device comprising the features of independent claim 11.

With regard to the configuration, to the performance and to the function of the control device according to the third aspect, full reference is also made to the general description of the invention above, and to the description of the other aspects of the invention as disclosed above and further below.

According to this third aspect, the invention is directed to a control device of a wind turbine, said control device comprising a device for determining at least one parameter value of the wind turbine and/or an interface for receiving at least one parameter value of the wind turbine, a device for determining wind speed values and/or wind shear values from the at least one parameter value of the wind turbine, a wind estimator or shear estimator of example; a simulation software running on said control device, said simulation software being provided for calculating load values, in particular load consumption values of the wind turbine, preferably for a defined time domain, based on entry values defined by said wind speed values and/or wind shear values, and optionally at least one parameter value of the wind turbine, and a control unit for controlling the at least one wind turbine based on the calculated load values.

Preferably, the control device is provided in such a way that it is capable of executing the method according to the first aspect of the invention. Alternatively, or in addition, the control device preferably comprises a data processing device or an interface to an external data processing device, wherein a computer program product according to the second aspect of the invention is executed on said data processing device.

For example, the different components of the control device can be provided as electronic devices, as electronic parts or as software components or as combinations of electronic devices or parts and software components. The different components can be linked in or as a control loop.

According to a preferred embodiment, the control device is provided as a so called ‘industrial computer’ or ‘automation computer’. Such computers, which are commercially available, are ruggedly constructed and can be used in industrial environments. They meet high standards with regard to reliability and long life.

According to the fourth aspect of the invention, the object is solved by a wind turbine, said control device comprising the features of independent claim 13.

With regard to the configuration, to the performance and to the function of the wind turbine according to the fourth aspect, full reference is also made to the general description of the invention above, and to the description of the other aspects of the invention as disclosed above and further below.

According to the fourth aspect, the invention is directed to a wind turbine, said wind turbine comprising a tower, a nacelle being mounted on top of the tower, said nacelle incorporating a drive train of the wind turbine, and a rotor being mounted to the nacelle, said rotor comprising a number of rotor blades. The wind turbine is characterized in that it further comprises a control device according to the third aspect of the invention, or that it comprises means for performing the method according to the first aspect of the invention.

According to a preferred embodiment, the wind turbine comprises at least one sensor for determining at least one parameter value of said wind turbine, in particular for determining the power and/or the rotational speed and/or the pitch angle and/or the wind direction and/or the air density and/or the blade moments. Furthermore, a control device is allocated to said wind turbine, said control device communicating with the at least one sensor, via at least one suitable interface for example.

According to yet another, fifth aspect of the present invention, the object is solved by a windfarm, said wind farm comprising a plurality of two or more wind turbines and a central-windfarm control device. Each wind turbine is configured in a way as described in connection with the fourth aspect of the invention. With regard to the configuration, to the performance and to the function of the windfarm according to this aspect, full reference is also made to the general description of the invention above, and to the description of the other aspects of the invention as disclosed above.

The present invention according to its different aspects has a number of effects and advantages, which are particularly as follows:
• Increase availability,
• Reduction of maintenance through better damage distribution between the various wind turbines within the wind farm,
• Higher energy yield,
• Avoid total loss,
• Reduced material costs,
• Extended life, and
• Improved performance quality at the grid acceptance point due to better controller quality
The invention will now be explained in more detail with respect to exemplary embodiments with reference to the enclosed drawings, wherein the foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view of a wind turbine incorporating the principles of the present invention;
Figure 2 is a schematic view of a windfarm comprising a number of wind turbines; and
Figure 3 is a schematic view showing the procedure of the method according to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 depicts a wind turbine (10) of the horizontal type with a tower (12) and a nacelle (11), which incorporates the principles of the present invention. Nacelle (11) is rotatable mounted to the top of tower (12). At its lower base end, the tower (12) is anchored to the ground by means of a foundation (13). Nacelle (11) incorporates a drive train (not shown), said drive train being mounted inside nacelle (11) and being connected to a rotor (14). Rotor (14) comprises three rotor blades (16, 17, 18) which are mounted to a hub (15). Hub (15) of rotor (14) is connected to a drive shaft of the drive train. Rotor blades (16, 17, 18) are adjustably mounted on the hub (15). This is realized by means of pitch drives (not shown), said pitch drives being part of a pitch system. The pitch system controls the rotor speed to given set points. By means of the pitch drives, the rotor blades (16, 17, 18) may be moved about rotor blade axes such that the pitch of the rotor blades (16, 17, 18) can be changed. This means that the pitch-angles of the rotor blades (16, 17, 18) can be changed such that the orientation of the rotor blades (16, 17, 18) can be varied.

The rotor (14) is rotatably connected to the drive train via its rotational axis. The drive train transmits the rotor speed to a generator device, where it is converted into electric energy. In order to transform the rotational energy of the rotor (14) into electric energy, the drive train may comprise a gear device.

A control device (19) is allocated to said wind turbine (10), said control device (19) being adapted for performing the method according to the present invention, which will be explained in detail in connection with Figure 3 further below.

As evident from Figure 2, the wind turbine (10) according to Figure 1 is part of a windfarm (20), said windfarm (20) comprising a number of wind turbines (10). In Figure 2, four wind turbines (10) of the windfarm (20) are shown for explanation purposes. However, the present invention is not limited to a specific number of wind turbines (10) for the windfarm (20). Windfarm (20) further comprises a central-windfarm control device (21). According to one preferred embodiment, control device (19) of each wind turbine (10) communicates with the central-windfarm control device (21), via a suitable interface. According to another preferred embodiment, control device (19) of each wind turbine (10) is implemented in the central-windfarm control device (21).

Figure 3 depicts a procedure of the method according to a preferred embodiment of the invention. The right part of Figure 3 (as delineated by dashed line) depicts the turbine control (30), whilst the left part of Figure 3 depicts the windfarm control (31). During the turbine control (30) the wind turbine (10) gets controlled based on calculated load values, damage values for example. In a first determination step (32), parameter values of the wind turbine (10) are determined. In the embodiment, during the first determination step (32), a measurement of the wind turbine power and/or of the rotational speed of the rotor and/or of the pitch of the rotor blades and/or of the wind direction is/are measured, by means of suitable sensors for example. Furthermore, values of rotor blade sensors may be considered. These parameter values are fed into a simulation module (33), which comprises a simulation software, by means of which a computer implemented simulation procedure is performed. During a second determination step (34), wind speed values and/or wind shear values are estimated by means of a wind estimator or by means of a shear estimator respectively. These evaluated wind speed values and/or wind shear values are implemented, during a simulation step (35), into a Multi-Body System of the simulation software as entry values, whereby the Multi-Body System uses the wind speed values and/or the shear wind values for performing a simulation. During a load simulation step (36), loads of the wind turbine are calculated at component relevant coordinate systems. In a further simulation step (37) a load calculation, a damage or fatigue calculation takes place on a time domain, on a ten-minute time series for example. Furthermore, an accumulated load is calculated. During a subsequent comparison step (38), the calculated load values, calculated damage values for example, for the wind turbine are compared against allowed loads with regard to the lifetime of the wind turbine. During a final calculation step (39), a possible boosting/overrating or de-rating of the wind turbine is calculated. The calculated loads as calculated with respect to the turbine control (30) are used by the central-windfarm control device (21) during the windfarm control (31).

Either the central-windfarm control device (21) receives calculated loads that have been calculated in control devices being allocated to each wind turbine, or the central-windfarm control device (21) acts as a control device for each wind turbine (10). In this case, the loads for each wind turbine are centrally calculated in the central-windfarm control device (21). In the central-windfarm control device (21), a control management (40) is performed for all wind turbines (10), that is wind turbines 1, 2, 3, …n.

During a control step (41), the central-windfarm control device (21) boost/overrates or de-rates each wind turbine (10) or some wind turbines (10) based on the calculated loads, calculated consumed loads, in particular consumed damage, for example. During an evaluation step, the central-windfarm control device (21) preferably evaluates the calculated load values for each wind turbine (10) against calculated load values of the other wind turbines (10), and the central-windfarm control device (21) controls the loads distribution to the wind turbines (10) based on this evaluation step. The load information received by the central-windfarm control device (21) for a wind turbine (10) is available for the central-windfarm control device (21) to evaluate against experienced loads of other wind turbines (10) of windfarm (20). Based on the currently maximum permitted nominal load of the wind turbines (10) in windfarm (20), the central-windfarm control device (21) optimizes the load distribution, the damage distribution for example, to wind turbines (10) within windfarm (20).

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly not limited.

LIST OF REFERENCE NUMERALS

10 Wind turbine
11 Nacelle
12 Tower
13 Foundation
14 Rotor
15 Hub
16 Rotor blade
17 Rotor blade
18 Rotor blade
19 Control device
20 Windfarm
21 Central-windfarm control device

30 Turbine control
31 Windfarm control
32 First determination step
33 Simulation module
34 Second determination step
35 Simulation step
36 Load simulation step
37 Further simulation step
38 Comparison step
39 Calculation step
40 Control management
41 Control step