DESC:FIELD OF THE INVENTION

The present invention generally relates to a wind turbine. More particularly, the present invention relates to a solution of controlling a wind turbine based on changing external conditions.

The present invention relates to a method of controlling a wind turbine, in particular for controlling said wind turbine on power and/or on torsion and/or on pitch, based on changing external conditions. 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

The present invention is directed to the technical field of wind turbines, in particular to 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. 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.
For controlling the wind turbine, conventional controllers are often used, such as PD-controllers, PID-controllers, PI-controllers and the like. Such controllers are used for controlling the power/rotational speed and/or the torque/rotational speed and/or the pitch/rotational speed for example.

Common power-rotational speed controllers or torque-rotational speed controllers or pitch-rotational speed controllers adjust themselves to target-values, which result from external conditions such as the energy in the wind, power/torque specifications derived from controller-parameters and the like.

Power, torque and rotational speed always run after the energy of the wind turbine. Therefore, there is always a delay in controlling the wind turbine, if the external conditions, for example the wind or power/rotational speed specifications, change. Due to this fact, periodical and non-periodical variations and overloads resulting therefrom can be intercepted insufficiently and delayed only.

For addressing some of the drawbacks mentioned before, EP 3 109 461 A1 describes a method for operating a wind turbine wherein an inflow power of the wind turbine is determined. Based on this inflow power, a pitch angle of at least one rotor blade of the rotor of the wind turbine is derived. Even though this known solution deals with the problem that using an output power of the wind turbine as a basis for deriving the optimum pitch angle, which might lead to a delay in the control of the wind turbine, the known solution still has a number of drawbacks.

The known solution is directed to a wind turbine which is operated under full load and it is the aim of this known solution to reduce peak loads. Any oscillations and vibrations, which result during partial load operation, cannot get compensated with the known solution, as the pitch angle is nearly constant in partial load. The known solution is directed to the adjustment of the pitch only, but it is not possible to properly address fatigue loads. Furthermore, in order to perform the known solution, it is required to use a power-pitch -table.

OBJECT OF THE INVENTION

Starting from the aforementioned 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 and universal solution of controlling different parameters of a wind turbine, such as power, torques or pitch, based on changing external conditions.

According to the present invention, the object is solved by the method of controlling a wind turbine using power and/or torsion and/or pitch, based on changing external conditions as described in the first aspect of the invention, by the computer program product as described in the second aspect of the invention, by the control device with the features as described in the third aspect of the present invention, and by the wind turbine with the features as described in 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 apply with respect to their disclosure in their entirety also 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 rotor acceleration-based control, in particular to a rotor acceleration-based speed control.

In contrast to the solution disclosed in EP 3 109 461 A1, the control procedure of the present invention is not dependent on a power-pitch-table. Instead the present invention is based on a function dependent of the rotational speed of the rotor of a wind turbine and/or based on functions based on an amplification or a gain schedule of a common pitch.

The present invention leads to reduced fatigue and extreme loads for tower and blade, for example blade extreme, tower fatigue, hub loads. Furthermore, a reduction of speed and power fluctuations and tower deflection fluctuations can be achieved.

The underlying concept of the present invention is that due to the consideration of the moments of inertia of the wind turbine and of the acceleration of the rotor a replacement-state, in particular a replacement-torque, a replacement-rotational speed or a replacement-power gets determined. The replacement-state chronologically precedes the adjusting actual-state of the wind turbine. Therefore, the future actual-state of the wind turbine can get estimated. If the estimated state is considered during the control procedure, any fluctuations and variations of the rotational speed, of the power and of the torque, as well as any loads being coupled thereto, in particular in the drive train, tower rotor, rotor blades of the wind turbine, can get reduced.

In particular, the present invention provides a solution for controlling a wind turbine using power and/or torsion and/or pitch. This particularly means that the control procedure is performed with respect to power and/or torsion and/or pitch. However, the control procedure is not dependent on a determined power, instead, according to the present invention an additional torque or a term including such an additional torque is determined, which can be used universally to control different parameters of the wind turbine. This will be described in more detail further below.

The present invention provides a functional solution which is independent from the load area, and which can handle non-cyclic or cyclic vibrations and oscillations. The acceleration-based control according to the present invention works for full load area and partial load, where it is interesting. The present invention can be used for achieving any mitigation of vibrations. It is not only used for load limitations. Nevertheless, the present invention can be used for limiting loads as well, such as tower loads and blade loads.

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 blade, 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.

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 of controlling a wind turbine, in particular for controlling said wind turbine using power and/or torsion and/or pitch, based on changing external conditions.

According to the first aspect the invention is provided a method of controlling a wind turbine based on changing external conditions.

In any case the wind represents the input for the method. Due to the wind and due to any wind change, the energy of the wind turbine, in particular the energy of the rotor, changes due to the rotor acceleration. This results in a different rotational speed of the rotor. Resulting therefrom is a different power value or a different pitch angle. Power, torque and rotational speed always run after the energy of the wind turbine. Therefore, there is always a delay in controlling the wind turbine, if the external conditions, for example the wind or power/rotational speed specifications, change. Due to this fact, periodical and non-periodical variations and overloads resulting therefrom can be intercepted insufficiently and delayed only. However, information relating to wind energy, wind speed but also to over-speeding is earlier available, if the rotor acceleration is considered and used. It is a principle of the present invention that this has been taken into account for controlling the wind turbine.

The method according to the first aspect is particularly directed to the field of controlling a wind turbine using power and/or torsion and/or pitch, based on changing external conditions.

The method is characterized by the following steps:

In a first step, the moment of inertia of the wind turbine and/or the rotor acceleration is determined. This can be achieved by measuring and/or by calculating and/or by estimating both parameters in a suitable way.

According to the present invention the moment of inertia, which is denoted by the character “J” throughout the specification, in particular is a moment of inertia with respect to the rotor axis, in particular of components with a degree of freedom with respect to the rotor axis or parallel to the rotor axis. According to the present invention, the rotor acceleration, which is denoted by the term ? ? throughout the specification, particularly is the angular acceleration of the rotor.

In a next step, a replacement-state of the wind turbine is determined based on the moment of inertia of the wind turbine and/or on the – angular - rotor acceleration. According to a preferred embodiment, as a replacement-state of the wind turbine, a replacement-torque, a replacement-rotational speed, or a replacement-power is determined.

Since the method is based on the moment of inertia of the wind turbine and/or on the angular - rotor acceleration, the aforementioned replacement-state chronologically precedes the actual-state of the wind turbine which adjusts due to the changing external conditions. That means that in the order of time the replacement-state of the wind turbine is earlier available than the actual-state of the wind turbine, if external conditions change. According to a preferred embodiment, the actual-state of the wind turbine, which changes and which therefore can be described as the future actual-state of the wind turbine is a different rotational speed of the rotor, a different power value or a different pitch angle of at least one rotor blade of the rotor.

In particular, a future actual-state of the wind turbine is estimated on the basis of the determined replacement-state of the wind turbine.

According to a final step of the method, the wind turbine is controlled on a control element by considering the replacement-state. This control element can be of different nature. For example, the wind turbine is controlled on a control element “power”, which means that the control element addresses the electrical power output of the wind turbine. Alternatively, or in combination, the wind turbine is controlled on a control element “pitch”, which means that the control element addresses the pitch, in particular the pitch angle, of at least one rotor blade of the rotor of the wind turbine.

As described further above, it is the general concept of the present invention that an additional torque or a term including such an additional torque is determined, which is used universally to control different parameters of the wind turbine. This will now be described in more detail.

According to a preferred embodiment, for determining the replacement-state of the wind turbine, an additional moment according to the formula J* ? ? is determined or estimated or calculated, wherein J is the moment of inertia and ? ? is the angular acceleration. The moment of inertia is mainly composed from different components, for example from the moment of inertia of the rotor with respect to the rotor axis, from the moment of inertia of the rotating parts with regard to the generator device and, if a gear device is used, from the gear ratio. The moment of inertia may be composed from other components of the drive train as well. The angular acceleration particularly represents the acceleration of the rotational speed of the rotor.

According to a preferred embodiment, for determining the replacement-state of the wind turbine, the additional moment as mentioned before is linked with, in particular is multiplied with, the angular speed of the rotor, which is denoted by the character ? throughout the specification. According to the term J*? ?*?. The angular speed of the rotor particularly represents a speed which is proportional to the rotational speed of the rotor. As an alternative, where the angular speed is not considered as a term of the function as explained in the aforementioned way, an amplification factor, which will be described further below, is used, said amplification factor being dependent on the angular speed of the rotor. Thus, said amplification factor, which is denoted as A(?) throughout the specification, is a function of the angular speed of the rotor.

According to yet another preferred embodiment, for determining the replacement state of the wind turbine, the additional moment or the aforementioned term is linked with, in particular is multiplied with, an amplification factor A. In particular, the amplification factor A is a factor, by means of which the additional moment or the aforementioned term gets expanded.

According to a preferred embodiment, the amplification factor A is dependent on the rotational speed of the rotor, and therefore on the angular speed of the rotor. In this case the amplification factor A is a function of the rotational speed of the rotor. Such an amplification factor is denoted as “A(?)” throughout the specification.

According to a different embodiment, as an alternative or in addition to the aforementioned embodiment, the amplification factor A is dependent on the pitch angle. In this case the amplification factor A is a function of the common pitch angle of at least one rotor blade of the rotor. Such an amplification factor is denoted as “A("Tc" )” throughout the specification.

In such a case the amplification factor A is dependent on the pitch itself, by means of a gain schedule for example, or by the rotational speed of the rotor. If the amplification factor A is dependent on the rotational speed, such an amplification factor A(?) will increase with increasing speed relation. If the amplification factor A is dependent on the pitch angle, such an amplification factor A("Tc") particularly considers the following context: The higher the pitch angle, the more sensitive the turbine is to changes in pitch angles. Moreover, this amplification is curtailed to upper and lower limits.
According to yet another preferred embodiment, the amplification factor A itself can be independent from the rotational speed of the rotor and/or of the pitch angle. In this case the amplification factor is a general amplification factor, which is denoted by the character “A” throughout the specification, in particular a constant, which is denoted as “Ac” throughout the specification.

In the following, different preferred embodiments of controlling a wind turbine in the sense as explained further above are described in more detail.

According to a preferred embodiment, for determining the replacement-state of the wind turbine, an additional moment ?T according to the formula ?T = J* ? ? is determined or estimated or calculated, wherein J is moment of inertia and ? ? is the angular acceleration of the rotor. For determining the replacement state of the wind turbine, as generally described further above, the additional moment ?T is linked with, in particular is multiplied with an amplification factor A, said amplification factor in particular being dependent on the rotational speed A(?) and/or on a common pitch angle A("Tc" ) and/or being a general amplification factor A, in particular a constant Ac.

Based on these considerations, it is preferably provided, that the replacement-state of the wind turbine, which temporarily precedes the actual-state of the wind turbine, is used for controlling the wind turbine on a control element “delta power ?P” and/or on a control element “delta pitch ?"T" ”.

In the following, a preferred embodiment will be described, wherein the replacement-state of the wind turbine is used for controlling the wind turbine on a control element “delta power ?P”. Preferably the control element “delta power ?P” is determined by linking the additional moment with, in particular by multiplying the additional moment with, the angular speed ? of the rotor according to the term J* ? ?* ?. The corresponding equation is ?P = * ? ?* ?. In particular a general amplification factor A, in particular a constant, can be linked, in particular multiplied, according to the equation ?P = A * J* ? ?* ?. According to a different embodiment, the control element “delta power ?P” is determined by linking the additional moment with, in particular by multiplying the additional moment, with an amplification factor A(?), which is dependent on the rotational speed of the rotor.

In the following, a preferred embodiment will be described, wherein the replacement-state of the wind turbine is used for controlling the wind turbine on a control element “delta pitch "?T" ”. Preferably the control element “delta pitch ?"T" ” is determined by linking the additional moment with, in particular by multiplying the additional moment, with an amplification factor A ("Tc" ), which is dependent on a common pitch angle "Tc" .

Preferably, the replacement-state of the wind turbine, which temporarily precedes the actual-state of the wind turbine, is used for controlling the wind turbine such that the term J *? ?* ?, in particular with an amplification factor A, is controlled on a control element “delta-power” and/or “delta-pitch”, wherein J is the moment of inertia, ? ? is the angular acceleration, and ? is the angular speed.

The aforementioned control procedure as described in the different embodiments can be performed independently from the regular control procedure of a standard pitch-controller or a standard power-controller or a standard torque-controller, or in addition thereto.

According to a different preferred embodiment, the replacement-state of the wind turbine, which temporarily precedes the actual state of the wind turbine, is, particularly directly, used for controlling the wind turbine such that is in controlled using an replacement-power, in particular a replacement power

P_replacement=P(?)+A*J* ? ?* ?,

or using a replacement-torque, in particular a replacement torque

T_replacement=T(?)+A*J* ? ?,

wherein J is the moment of inertia, ? ? is the angular acceleration with regard to the rotor axis, ? is the angular speed with regard to the rotor axis, A is the amplification factor, P(?) is the power dependent on the rotational speed of the rotor, particularly dependent on the angular speed of the rotor, Preplacement is the replacement-power, T(?) is the torque dependent on the rotational speed of the rotor, particularly dependent on the angular speed of the rotor, and Treplacement is the replacement-torque.

According to yet another preferred embodiment, which is linked to the aforementioned embodiment, the replacement-state of the wind turbine, which temporarily precedes the actual-state of the wind turbine, is used for controlling the wind turbine such that based on the aforementioned replacement-power or based on the aforementioned replacement-torque, by use of a rotational speed-power-curve or by use of a rotational speed-torque-curve, a new rotational speed is determined for controlling the pitch-angle of at least one rotor blade of the rotor. In particular, a replacement-pitch angle difference is used as a control element, in order to control on the target-state of the rotational speed.
According to the second aspect of the present invention the object is solved by a computer program product.

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 further above, and to the description of the other aspects of the invention as disclosed further 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 a wind turbine, in particular for controlling said wind turbine using power and/or torsion and/or pitch, based on changing external conditions, according to the first aspect of the present invention.

According to the third aspect of the invention, the object is solved by the control device.

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 further above, and to the description of the other aspects of the invention as disclosed further above and further below.

According to this third aspect, the invention is directed to a control device of a wind turbine, said control device being provided for controlling the wind turbine, in particular for controlling said wind turbine using power and/or torsion and/or pitch, based on changing external conditions. The control device is provided in such a way that it is capable of executing the method according to the first aspect of the present invention. Alternatively, or in addition, the control device 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 present invention is executed on said data processing device.

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

According to yet another preferred embodiment, the control device comprises a computer program product according to the second aspect of the invention, which is at least temporarily executed in or by the data processing unit of the control device.

Preferably the control device comprises means for performing the method according to the first aspect of the invention.

According to the fourth aspect of the invention, the object is solved by a wind turbine.

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 further above, and to the description of the other aspects of the invention as disclosed further 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 the wind turbine further comprises a control device being provided for controlling the wind turbine, in particular for controlling said wind turbine using power and/or torsion and/or pitch, based on changing external conditions, according to the third aspect of the present. Alternatively, or in addition, the wind turbine comprises means for performing the method according to the first aspect of the present invention.

With the solution according to the present invention, the actual state of the wind turbine can get estimated earlier and therefore, one can react to any changes earlier as well, for example by means of a power control, a torsion control or a pitch control. That means that due to the present invention it is possible to react on changing energy states much earlier, such as variations of the wind, variations in the air-density or in the air-humidity, variations of other weather conditions affecting energy state changes and the like. Thus, load oscillations, tower and blade deflections, peak loads, power fluctuations and rotational speed fluctuations can get minimized.

The present invention according to its four aspects has a number of effects and advantages, which are particularly as follows:

Reduced fluctuations in rotational speed, torque, power
Reduced oscillations of the tower
Reduced rotor blade loads
Reduced costs of the wind turbine generator and reduced costs of energy due to load reductions, fatigue reductions and extreme load reductions
Reduced material costs
Extended life of the wind turbine
Improved power quality at the power take off point due to better control performance
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 drawing figures:

BRIEF DESCRIPTION OF THE INVENTION

Figure 1 shows a schematic view of a wind turbine incorporating the principles of the present invention;
Figure 2 shows a control-block diagram of a method of controlling a wind turbine according to a first embodiment;
Figure 3 shows a control-block diagram of a method of controlling a wind turbine according to a second embodiment;
Figure 4 shows a control-block diagram of a method of controlling a wind turbine according to a third embodiment;
Figure 5 shows an amplification factor depending on angular rotor speed for controlling a wind turbine; and
Figure 6 shows an amplification factor depending on a common pitch angle for controlling a wind turbine.

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. The 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.

Figure 2 depicts a control-block diagram of a method of controlling a wind turbine according to a first preferred embodiment of the invention. According to this embodiment, the replacement-state of the wind turbine, which temporarily precedes the actual-state of the wind turbine, is used for controlling the wind turbine.
In the upper part of Figure 2 it is shown, how the wind turbine is controlled on a control element “delta power”. In a first step (20), the rotational speed of the rotor is determined. The rotor speed can be obtained from the generator speed for example, and from a gearbox ration if applicable. In a second step (21), the angular rotor acceleration of the rotor is derived from the rotational speed of the rotor. An additional moment ?T = J*? ? is determined or estimated or calculated. The moment of inertia J is mainly composed from different components (22), for example from the moment of inertia of the rotor with respect to the rotor axis, from the moment of inertia of the generator and other rotational drive train components with respect to the rotational axis of the drive train and, if a gear device is used, from the gear ratio and/or from the gearbox inertia itself. The additional moment ?T is linked with, in particular is multiplied with, an amplification factor A (?), which is dependent on the rotational speed of the rotor. This amplification step is denoted by reference numeral (27) in Figure 2. This amplification factor A(?) will increase with increasing speed relation as shown in Figure 5.

Optionally, the additional moment can get filtered in a filtering step (23) for smoothing down the signals.

In the lower part of Figure 2 it is shown, how the wind turbine is controlled on a control element “delta pitch”. Starting point is a common pitch angle "Tc" (24). A replacement-state is determined by means of a gain schedule (25), which is limited by a maximum gain (26). An amplification factor A can be used which is dependent on the common pitch angle and which therefore is a function of the pitch angle. Such a gain schedule can be a formula, a function a table or the like. Such an amplification factor A("Tc") considers the following context: The higher the common pitch angle, the more sensitive the turbine is to additional changing pitch angles. In particular, gain scheduling reduces P-factor for higher pitch angles. Moreover, this amplification is curtailed to upper and lower limits. A course of the amplification factor A("Tc") in relation to the pitch angle "Tc " is schematically shown in Figure 6.

The control procedure according to Figure 2 results in common pitch angle offset and/or a power offset (28).

In accordance with the embodiment according to Figure 2 the following equations are considered:

Additional moment: "?" T= (J*" " ? ? );
“Delta Power”: "?" P= A(?)*(J*" " ? ? ), in particular "?" P= A *(J*" " ? ? )* ?
“Delta Pitch”: ?T= A("Tc" )*A(?)*(J*" " ? ? ), in particular ?T= A *(J*" " ? ? )* ?

wherein, as defined in the general description of the present invention further above

J is the moment of inertia;
(? ) ?is the angular acceleration, which particularly represents the acceleration of the rotational speed of the rotor;
? is the angular speed, which particularly represents a speed which is proportional to the rotational speed of the rotor;
A is the amplification factor;
T is the torque;
P is the power;
"T" is the pitch angle for a control element;
"Tc" is the pitch angle of a common pitch.

Figure 3 depicts a control-block diagram of a method of controlling a wind turbine according to a second preferred embodiment of the invention. According to this embodiment the control takes place by means of a direct implementation in power.

In the upper part of Figure 3 it is shown, that in a first step (20), the rotational speed of the rotor is determined. The rotor speed can be obtained from the generator speed for example. In a second step (21), the rotor acceleration is derived from the rotational speed. Optionally, the derivation can get filtered in a filtering step (23) for smoothing the signals. Such a filtering step preferably takes place before the derivation step. An additional moment is determined or estimated or calculated. The moment of inertia is mainly composed from different components (22), for example from the moment of inertia of the rotor with respect to the rotor axis, from the moment of inertia of the generator and, if a gear device is used, from the gear ratio. The additional moment ?T is linked with, in particular is multiplied with, an amplification factor A, which is dependent on the rotational speed or on the pitch angle or a constant, and which is denoted with reference numeral (27) in Figure 3. The control procedure according to Figure 3 results in common power offsets (28).

The lower part of Figure 3 shows a common way of deriving a power from the rotational speed of the rotor. In such a case the determined value of the rotational speed is compared with a rotational speed-power-curve (30), from which a power (31) gets derived.

In accordance with the embodiment according to Figure 3 the following equations are considered:

Power:P_res=Power_speedcurve (?)+"A"*(J*" " ? ? )

The variable amplification factor A can be dependent on either the angular speed ? of the rotor and/or on a common pitch angle "Tc" .

In particular,

P_res=Power_speedcurve (?)+A *(J*" " ? ? )* ?

wherein A is an amplification factor. The meaning of the parts of the equations corresponds to the definitions as mentioned further above.

Figure 4 depicts a control-block diagram of a method of controlling a wind turbine according to a third preferred embodiment of the invention. The embodiment according to Figure 4 corresponds to the embodiment according to Figure 3. Therefore, with regard to the general description of the embodiment according to Figure 4, full reference is made to the description of Figure 3 first.

According to the embodiment depicted in Figure 4, the replacement-state of the wind turbine, which temporarily precedes the actual-state of the wind turbine, is used for controlling the wind turbine such that based on the replacement-power or on the replacement-torque, by use of a rotational speed-power-curve (32) or by use of a rotational speed-torque-curve, a new rotational speed (33), for a PID Pitch control for example, is determined. In the end, the control procedure according to Figure 4 results in a new pitch angle.

In accordance with the embodiment according to Figure 4 the following equations are considered:

Power:P_res=Power_speedcurve (?)+ "A"*(J*" " ? ? )
The amplification factor A can be dependent on either the angular speed ? of the rotor and/or on the common pitch angle "Tc" .

In particular

P_res=Power_speedcurve (?)+A *(J*" " ? ? )* ?

The meaning of the different parts of the equations corresponds to the definitions as mentioned further above.

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
20 First step
21 Second step
22 Moment of inertia of the components
23 Filtering step
24 Common pitch angle
25 Gain schedule
26 Maximum gain
27 Additional amplification
28 Power offset/output and/or common pitch angle offset
29 Amplification factor
30 Rotational speed-power-curve
31 Power
32 Rotational speed-power-curve
33 New rotational speed

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.
,CLAIMS:We claim:

A method of controlling a wind turbine (10), in particular for controlling said wind turbine (10) using power and/or torsion and/or pitch, based on changing external conditions, said method being characterized by the following steps:

Determining the moment of inertia of the wind turbine (10), in particular the moment of inertia with respect to the rotor axis, and/or the rotor acceleration, in particular the angular rotor acceleration;

Based on the moment of inertia of the wind turbine (10) and/or on the rotor acceleration, determining a replacement-state of the wind turbine (10), said replacement-state chronologically preceding the actual-state of the wind turbine (10) which adjusts due to the changing external conditions.

By considering the replacement-state, controlling the wind turbine (10) on a control element “power” and/or on a control element “pitch”.

The method according to claim 1, characterized in that on the basis of the determined replacement-state of the wind turbine (10), a future actual-state of the wind turbine is estimated.

The method according to claim 1 or 2, characterized in that, as a replacement-state of the wind turbine (10), a replacement-torque, a replacement-rotational speed, or a replacement-power is determined.

The method according to anyone to claims 1 to 3, characterized in that the future actual-state of the wind turbine (10) is a different rotational speed of the rotor (14), a different power value or a different pitch angle of at least one rotor blade of the rotor (14).

The method according to anyone to claims 1 to 4, characterized in that for determining the replacement-state of the wind turbine (10), an additional moment ?T according to the formula ?T = J* ? ? is determined or estimated or calculated, wherein J = moment of inertia and ? ? = angular acceleration of the rotor.

The method according to claim 5, characterized in that for determining the replacement state of the wind turbine (10), the additional moment ?T is linked with, in particular is multiplied with an amplification factor A, said amplification factor in particular being dependent on the rotational speed A(?)and/or on a common pitch angle A("Tc" ) and/or being a general amplification factor A, in particular a constant A(c).

The method according to claim 5 or 6, characterized in that the replacement-state of the wind turbine (10), which temporarily precedes the actual-state of the wind turbine (10), is used for controlling the wind turbine (10) on a control element “delta power ?P” and/or on a control element “delta pitch ?"T\"" .

The method according to claim 7, characterized in that the control element “delta power ?P” is determined by linking the additional moment with, in particular by multiplying the additional moment with, the angular speed ? of the rotor according to the term J* ? ?* ?, in particular by linking, particularly by multiplying, an amplification factor A, or that the control element “delta power ?P” is determined by linking the additional moment with, in particular by multiplying the additional moment, with an amplification factor A(?), which is dependent on the rotational speed of the rotor.

The method according to claim 7 or 8, characterized in that the control element “delta pitch ?"T" ” is determined by linking the additional moment with, in particular by multiplying the additional moment, with an amplification factor A("Tc" ), which is dependent on a common pitch angle "Tc" .

The method according to anyone of claims 5 to 9, characterized in that the replacement-state of the wind turbine (10), which temporarily precedes the actual state of the wind turbine (10), is used for controlling the wind turbine (10) such that it is controlled using a replacement-power, in particular a replacement power P_replacement=P(?)+A*J* ? ?* ?, or using a replacement-torque, in particular a replacement torque T_replacemenet=T(?)+A*J* ? ?, wherein J = moment of inertia, ? ? = angular acceleration, ? = angular speed, A = amplification factor, P = power, Preplacement = replacement-power, T = torque, Treplacement = replacement-torque.

The method according to claim 10, characterized in that the replacement-state of the wind turbine (10), which temporarily precedes the actual-state of the wind turbine (10), is used for controlling the wind turbine (10) such that based on the replacement-power or based on the replacement-torque, by use of a rotational speed-power-curve or by use of a rotational speed-torque-curve, a new rotational speed is determined for controlling the pitch-angle of at least one rotor blade of the rotor.

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 a wind turbine (10), in particular for controlling said wind turbine (10) using power and/or torsion and/or pitch, based on changing external conditions, according to anyone of claims 1 to 11.

A control device of a wind turbine (10), said control device being provided for controlling the wind turbine (10), in particular for controlling said wind turbine (10) using power and/or torsion and/or pitch, based on changing external conditions, said control device being provided in such a way that it is capable of executing the method according to anyone of claims 1 to 11, and/or that the control device comprises a data processing device or an interface to an external data processing device, wherein a computer program product according to claim 12 is executed on said data processing device.

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 being provided for controlling the wind turbine (10), in particular for controlling said wind turbine (10) using power and/or torsion and/or pitch, based on changing external conditions, according to claim 13, or that the wind turbine (10) comprises means for performing the method according to anyone of claims 1 to 11.