Control method for an offshore floating tower wind turbine and control system and wind turbine using the control method

Abstract

The present invention relates to a control method for controlling an offshore floating tower wind turbine (1) and various systems and wind turbines (1) using said control method. The invention is primarily based on controlling the pitch angle of the blades (3) of the wind turbine (1) with power levels different from the rated power depending on the moving conditions the wind turbine (1) is subjected to at sea, for wind speeds above the rated operating conditions. By the method described, the invention allows the movements subjected to the wind turbine (1) to be reduced in order to make more efficient use of its energy performance, without compromising its service life.

Description

[Technical field]

[0001] The present invention is within the field of marine wind energy generation technology. In particular, the present invention relates to a control method for controlling offshore floating tower wind turbines. The present invention also relates to a system and a wind turbine using or implementing said method. [Background technology]

[0002] The potential for the global development of offshore wind energy is promising: significant improvements in the efficiency of this technology will make its role in the future global energy "mix" very relevant.

[0003] In comparison with onshore wind turbine installations, offshore wind turbine installations present greater technical and access difficulties, but have three major advantages: on the one hand, the greater wind resources found at sea as opposed to on land, and on the other hand, the greater the amount of available space for installing wind turbines, without any easily perceptible social impact. Finally, the fact that these spaces are very close to the main electricity consumption centres is also relevant, since most of the population residing in the plants is found in areas close to the coast.

[0004] Offshore wind energy generation technologies can then be divided into two broad groups: wind turbines mounted on fixed structures, also called bottom-fixed structures, attached or supported on the seabed, and wind turbines mounted on floating structures.

[0005] The behavior of wind turbines on bottom-fixed structures is logically similar to that of land-based turbines. The technology has progressed rapidly towards cost improvement and is now being used in significant quantities in Europe and other parts of the world, with favorable energy costs. The most recent contracts awarded in European awards were for less than 50 Euro per MWh of energy produced.

[0006] However, the case of offshore wind is different: the technology is not yet commercially available and there are only a handful of prototype and pre-serial installations worldwide. One of the most important technical aspects to be solved in this field is the control of the turbine on a moving structure, which is different from the case of onshore wind energy or offshore bottom-fixed wind energy, where the wind turbine operates on a fixed structure. The float thereby induces a movement in the turbine and the turbine induces a movement in the float. Controlling this movement efficiently is a technical challenge and this is the field to which the present invention applies.

[0007] One of the main challenges facing the industry in this regard is the phenomenon known as negative damping.

[0008] Aerodynamic damping is a very relevant and beneficial aspect for reducing the movements and / or stresses on wind turbines and the structures that support them. In very simple terms, aerodynamic damping is based on the variation of aerodynamic forces due to which the movement of the wind turbine has a tendency to resist and / or slow down said movement. That is, when the wind turbine is displaced against the wind, the relative wind speed on the rotor increases. Thereby, the thrust of the movement against the wind increases, thus contributing to slow down said movement. Similarly, when the wind turbine is displaced in the opposite direction, in the same direction as the wind, the relative wind speed on the rotor drops and the thrust of the wind in the direction of the movement decreases, which contributes to the reduction or damping of said movement. This is a positive damping phenomenon.

[0009] However, in modern wind turbines, where the blade pitch angle "A" is adjusted (see FIG. 1), above a certain wind speed, called rated wind speed (Vr), the control system acts on the blade pitch angle "A" (see FIG. 2b) to prevent the power from exceeding the rated output of the wind turbine (see FIG. 2a) and to mitigate the maximum stresses that the machine and structure must withstand. As a result of this form of control, used in almost all modern multi-megawatt wind turbines on fixed structures, for wind speeds greater than Vr (a situation commonly known as above-rated operation), the relationship between the thrust on the wind turbine and the wind speed is reversed, as can be observed in FIG. 2c, for the purpose of keeping the power constant and approximately equal to the rated output of the wind turbine. Thus, with conventional control devices at rated operation, an increase in wind speed does not result in an increase, but rather a decrease, of the thrust on the rotor, and a decrease in wind speed does not result in a decrease, but rather an increase, of the thrust on the rotor. For the rated operating conditions, this results in the above-mentioned positive damping effect being reversed, resulting in a negative damping phenomenon, which may include an increase in undesirable movements and stresses to which the wind turbine and its components are subjected. Simply put, the reason behind said negative damping phenomenon is that as the turbine moves into the wind, it generates an apparent or relative "additional wind". Since the turbine is already operating above its full or rated power, the controller increases the pitch angle "A" with the aim of keeping the power constant, which causes a reduction in the wind thrust on the blades and rotor. A side effect is that this thrust on the blades is reduced, which helps to slow down the forward motion of the turbine. In contrast, when the turbine stops moving forward and starts moving backward, the apparent wind decreases, and as a result of the lower wind, the turbine controller decreases the blade pitch angle "A" so that the blades generate more thrust and torque on the rotor in order to maintain the power despite the lower apparent wind. By generating more thrust, they intensify the backward movement of the turbine.

[0010] The detrimental effects of this phenomenon are greater the more motion the wind turbine undergoes, and therefore it is particularly important in the design and operation of floating wind turbines. This behavior of traditional controls, which maximize the production of fixed wind turbines and minimize the loads on the fixed wind turbines, therefore creates undesirable, and often unacceptable, motions in offshore floating turbines.

[0011] Solving the movements generated in offshore floating turbines caused by negative damping induced by wind changes, by waves as well as by the turbine operation itself has been the subject of various solutions known in the state of the art.

[0012] The basic premise in most of these solutions is to add data corresponding to the turbine position or speed to the turbine control data, through the movement of the tower, in order to attempt to introduce some form of correction to the data related to the blade pitch angle.

[0013] Thus, for example, US Pat. No. 6,299,633 describes a turbine control system that includes a wind flow estimator that provides wind flow, tower position, and tower speed to calculate a desired pitch angle.

[0014] US Pat. No. 5,399,433 describes a turbine control system including a control system, which uses tower tilt information to modify a reference turbine rotation speed of a wind turbine to achieve a stabilizing effect in a floating system.

[0015] US Patent No. 5,393,633 describes a control system for a turbine which uses an accelerometer in the turbine to detect vibrations in the turbine's tower and thereby modifies the pitch angle to prevent vibration modes in the tower.

[0016] US Pat. No. 5,399,633 describes a system for damping the tilt of a floating turbine by acting on the rotor pitch and rotational speed based on turbine acceleration information.

[0017] US Pat. No. 5,399,633 describes a control system for a floating turbine that acts on the pitch depending on the motion of the turbine in the stopping phase, in the starting phase and when the turbine is not producing energy in order to stabilize the turbine.

[0018] Nevertheless, the above known solutions for mitigating the harmful effects of negative damping reduce, but generally do not eliminate, said damping. Moreover, they have the additional problem that they allow said reduction or mitigation of negative damping at the expense of energy losses compared to the performance offered by wind turbines of fixed structure. Basically, what they do is that the blades capture less wind so that they leave room to abandon or at least to a certain extent depart from the behavior described for the control of onshore turbines that generate negative damping.

[0019] In view of the above technical problems and limitations, it is necessary to provide a new control method for controlling a floating wind turbine, which allows the undesirable effects of negative damping to be reduced to a greater extent. The present invention makes it possible to meet said need as a result of a new control method for controlling a floating wind turbine, which may not only improve the reduction of the negative damping effect, but also eliminate the negative damping effect or provide a certain positive damping effect, even in the above-mentioned rated operating conditions, all while minimizing the energy losses with respect to those suffered by the fixed structure, or even leading to a certain increase in the production of energy. Summary of the Invention [Problem to be solved by the invention]

[0020] In order to overcome the above-mentioned shortcomings of the state of the art, the object of the present invention is to provide a novel control method for controlling a wind turbine, designed to reduce the loads in the wind turbine and supporting structure with low or zero loss of energy production capacity by minimizing, eliminating or even reversing the undesirable negative damping effects for wind speeds greater than the rated speed "Vr" (above rated operation). [Means for solving the problem]

[0021] In order to better describe the present invention, specific definitions and explanations of certain terms that are intended to be within the scope of the present invention and its preferred embodiments are provided below.

[0022] Wind turbine rated power (P rated): The rated power of a wind turbine is a value that forms part of the technical characteristics of a particular wind turbine model and is essentially one of the important parameters in the sale of wind turbines and is therefore reflected in virtually all documents containing technical and / or sales characteristics of modern wind turbines. Often, but not always, the rated power of a wind turbine even forms part of the name used to refer to a particular model. Thus, for example, the rated power of the AW3000 wind turbine from the manufacturer Acciona Windpower is 3000kw, the rated power of the SWT-3.6-107 model from the manufacturer SIEMENS is 3.6MW and the rated power of the 2.75-120 model from the manufacturer GE is 2.75MW, to take a few examples. In general, the rated power corresponds to the maximum power at which the wind turbine operates in suitable wind conditions. In conventional control systems, the rated power is generally the upper power threshold above which the control system begins to apply an increase to the blade pitch angle "A" in order to keep the wind turbine's power output generally below or not exceed said threshold. This does not mean that the rated power is the actual or design limit capacity of the wind turbine, nor does it prevent the wind turbine from operating in certain cases at a power level greater than the rated power under certain and / or temporary conditions. For example, if a very sudden increase in the speed of the wind turbine is generated, this may result in a temporary increase in power output because the response time of the controller in adjusting the blade pitch angle to reduce the power output is not instantaneous. Or, for example, the singular point of transition between below-rated and above-rated operation may include a momentary condition of power output slightly greater than the rated power output. In either case, conventional control methods are designed to attempt to keep the wind turbine operating at a power output not greater than the rated power output.

[0023] Blade Pitch Angle (A): Blade pitch angle "A" refers to the position or rotation of the blade along an axis substantially coinciding with the longitudinal axis of the blade, as seen diagrammatically in Figure 1. It is common to have wind turbines in the state of the art that are capable of varying the pitch angle of the blades, a process that is largely controlled by a control system or controller, which performs functions based on a set of control algorithms.

[0024] There is a particular pitch angle of the blade that maximizes the aerodynamic exposure of the blade to the incident wind and thus maximizes the horizontal thrust energy and production capacity exerted by the wind. By convention, said position is usually defined as the minimum pitch angle "A" position of the blade and is assigned a value of A=0 degrees to said position. As the blade rotates, often in what is by convention referred to as a rotation that increases the blade pitch angle "A", the exposure to the incident wind decreases and so does the torque generated by the wind on the rotor, the power generated, and / or the horizontal thrust exerted by the wind on the rotor. When said angle "A" reaches its maximum value, equal to or close to 90 degrees, the blades are in a position that minimizes or eliminates the torque and thrust generated by the wind, a position commonly known as "feathered blades" (see FIG. 1b). This is the convention of values ​​and signs of the blade pitch angle "A" commonly used in the wind turbine industry and will be used for the description of the present invention, where it is of course possible to use other possible conventions of values ​​or signs without departing from the scope of the present invention.

[0025] The blade pitch angle "A" used at each moment is established by a control system for controlling the wind turbine and depends, among other things, on the speed of the incident wind, which usually takes the rotational speed of the rotor and / or generator, which in turn depends on the speed of the incident wind, as a control parameter which is easier and more reliably monitored.

[0026] Wind speed (Vw): This is the speed at which the wind strikes the rotor of the wind turbine. Obviously, said speed is generally not the same at all points in the plane of the rotor, so the value assigned to Vw is an average and / or representative value.

[0027] It is appropriate and relevant to distinguish between absolute wind speed, measured relative to a fixed point in space, and apparent or relative wind speed with respect to the rotor. When the wind turbine is stationary or fixed, both speeds are the same, but when the wind turbine undergoes motion experiments, the absolute wind speed is different from the relative speed at which the wind hits the rotor (see FIG. 4). Thus, when the wind turbine moves against the wind, the apparent or relative speed increases and is greater than the absolute wind speed, whereas when the wind turbine moves in the same direction as the wind, the relative wind speed decreases and is less than the absolute wind speed. Throughout the description of this invention, unless otherwise indicated, the wind speed Vw refers to the apparent or relative speed with respect to the rotor.

[0028] Wind turbine speed (Va): A wind turbine may undergo movements, especially as a result of the displacement or deformation of the substructure that supports it. As a convention used throughout the description of this invention, when the wind turbine moves in the direction against the wind direction, its speed is understood as positive (Va>0) (see FIG. 3a), and when the wind turbine moves in the same direction as the wind direction, its speed is negative (Va<0) (see FIG. 3b). Obviously, if the wind turbine is completely stationary, Va=0.

[0029] It will be appreciated that the movement of a wind turbine is periodic, such that cycles with Va>0, hereinafter referred to as "forward movement cycles", are intercalated with cycles with Va<0, hereinafter referred to as "backward movement cycles" or backward movement.

[0030] The motion and speed of a wind turbine is generally not perfectly aligned with the wind direction, nor perfectly perpendicular to the plane of the rotor. Throughout the description of this invention, Va is referred to as the overall speed component of the wind turbine projected onto the shaft of the rotor. Va is therefore determined from a speed vector decomposition, providing the corresponding vector component of the speed along said shaft of the rotor.

[0031] Note that the above criteria or conventions for the definition of Va apply equally to upwind wind turbines (with rotors positioned upwind) or downwind wind turbines (with rotors positioned downwind). Of course, other conventions for the direction of movement and / or sign of Va are possible without departing from the scope of the invention.

[0032] Having established certain definitions, the description of the present invention will now proceed. The assumption or criterion underlying control systems known in the art is that when the turbine is above its rated operating mode, the power produced is greater than the rated power P of the turbine. rated Therefore, the conventional controller has a restriction that the threshold P rated The system is designed and programmed to attempt to prevent and / or correct for outputs exceeding

[0033] In this context, the present invention provides a P rated The present invention uses a control method for controlling a turbine that uses adjustments to the power output with deliberate variations that may be both above and below the rated power output P. The variations in power output are applied in a specific manner designed to prevent or reduce the negative damping phenomenon. Furthermore, the power output is adjusted to be less than the rated power output P for short periods of time. rated Although the demand, stress and / or requirements on the generator and electrical system may be intentionally exceeded, the method is rated This allows the average power output to be maintained substantially similar to the rated power output, similar to what would exist under conditions of approximately constant and equal power output.

[0034] To this end, during a forward movement or forward movement cycle of the wind turbine (Va>0), when the wind Vw (apparent wind) the turbine "sees" tends to increase, the control method according to the invention causes the turbine to increase its power and produce a power above its rated power, and in contrast, when the turbine moves backwards (backward movement cycle with Va<0), the control method causes the turbine to reduce its power and produce a power below said rated power.

[0035] As a result of said deliberate and specific adjustments to the operating power, it is possible to adopt values ​​of the blade pitch angle A which reduce or eliminate the negative damping effect.

[0036] The control of negative damping with specific criteria regarding the variation of the generated power output, according to the present invention, offers considerable advantages over the current state of the art.

[0037] During said rated operation, not only is negative damping reduced, but also positive and / or active damping can be generated. Current systems reduce the negative damping generated by typical onshore turbine controls. These systems do not eliminate negative damping, but rather only reduce it. The turbine continues to move more than it should due to the floating characteristics, the waves, the variable thrust of the wind. With a through-power control system, the negative damping disappears completely and becomes positive damping. As a result, the turbine dramatically reduces its movement, with a corresponding reduction in loads, float, and floating moorings on different elements of the turbine, which may improve the safety and / or economy of the wind turbine as a whole. With the control system according to the invention, the unavoidable movements of a floating wind turbine result in fluctuations in the applied power during said rated operation, but said fluctuations contribute to reducing the movements, and by reducing the movements, the fluctuations that need to be applied are in turn smaller, with a virtuous circle of reduced movements, thereby reducing the required fluctuations in the generated power.

[0038] - it results in an increase in the energy generated over the energy losses in the current negative damping mitigation systems. That is, the current systems are based on letting some wind through to prevent the negative damping generated by the typical control software of onshore turbines when the turbine is operating in strong winds close to the turbine rated power. Thus, to a certain extent, less energy is generated than that generated by the same wind turbine located on a fixed structure. In contrast, the proposed control method based on a specific induced variation of power combines the moment that the wind is left to pass in the backward movement cycle with the moment that more wind is captured in the forward movement cycle, so that when forward movement occurs, the turbine generates more and when backward movement occurs, the turbine generates less. Thus, the total energy generation does not decrease, it may even increase. In fact, since the generation is proportional to the cube of the wind speed, the increase in generation when the turbine moves forward can be greater than the generation loss when the turbine moves backward.

[0039] - The control system has simplified programmability, i.e. it may be programmed in a variety of ways, taking into account different available inputs. An example of possible simple programming is to use a logic similar to the current control logic for the above-mentioned rated situations in onshore or bottom fixed turbines, where a logic is introduced that modifies the parameters of the power to be generated with inputs for the induced speed and / or acceleration of the turbine / tower caused by the floating forward and backward movements, which modifies the maximum and / or target power upwards at the moment the turbine moves forward and reduces it in situations where the turbine moves backward. This power modification algorithm may take into account a number of variables, including among them the temporary difference between the apparent wind incidence and the correction of the rotor speed, which is not instantaneous due to the rotor rotational inertia and / or the bending of the blades.

[0040] Thus, if there is a change in the actual wind speed, without any backward movement of the turbine, the control system continues to operate normally and increases the pitch angle similarly to how a conventional controller known in the art would do. However, if the speed Va of the wind turbine exceeds a certain threshold, the control system selectively modifies parameters of the maximum power to be generated and / or the target power output upwards and / or downwards depending on Va in order to appropriately damp those movements of the wind turbine.

[0041] The variations or deliberate power adjustments according to the method of the invention may be made, for example, by varying the rotational speed of the rotor or by varying the torque of the generator or by a combination of both. In a preferred embodiment of the method according to the invention, the variations in power are applied by varying the torque of the generator, whereas the speed of the rotor that the control system seeks or attempts to maintain is constant. Said constant rotational speed sought is preferably the rated rotational speed, that is the rotational speed at which the rotor rotates at rated potential if the wind turbine is operating on a fixed structure using its standard or conventional controller. In said embodiment, when applying variations in power according to the method of the invention, which maintains an approximately constant rotational speed of the rotor, the algorithm for adjusting the pitch angle A can be similar to the algorithm used in conventional control algorithms that generally operate by maintaining an approximately constant rotational speed of the rotor.

[0042] In another possible embodiment, in addition to the relative turbine movement induced by the turbine movement, additional data such as the actual measured wind in front of the turbine can be captured in order to program the control method according to the invention.

[0043] The object of the present invention is therefore preferably achieved by a control method for controlling an offshore floating tower wind turbine, said wind turbine comprising: o Includes a rotor with multiple blades. ○ The speed at which the wind strikes the rotor V, which changes over time w Generate an output P that depends on P, where P rated V w is the rated wind speed V r The rated power output of a wind turbine may be achieved when the o Includes means for adjusting the blade pitch angle A as follows: ■ Specific wind speed V w Given the above, an increase in the blade pitch angle A is accompanied by a decrease in the rotational speed of the rotor and / or in the power P generated and / or in the thrust exerted by the wind on the rotor. ■ Wind speed V w Given the above, a reduction in the blade pitch angle A is accompanied by an increase in the rotational speed of the rotor and / or in the power P generated and / or in the thrust exerted by the wind on the rotor. ■ The blade pitch angle A has a minimum value assigned, by convention a 0 degree blade pitch value. ■ V r Wind speed V greater than w Given, the generated output P is P rated The theoretical pitch angle A of the blade greater than 0° is substantially equal to t There is. o Experiments in at least one operating condition, the movement of the wind turbine generating a velocity Va, which is understood to be positive (Va>0) when the wind turbine is displaced in a direction that is substantially opposite to the direction of the wind, and negative (Va<0) when the wind turbine is displaced in a direction that is substantially in line with the direction of the wind. o Includes a sensor that allows the speed Va of the wind turbine to be monitored directly or indirectly.

[0044] The control method advantageously further comprises carrying out the following steps: ○ At least the wind turbine speed Va is positive (V a >0) and the wind speed Vw is greater than Vr (V w >V r ) During a portion of the time when the blade pitch angle A is A tLess than (A t ) is established, and the generator is rated Output P greater than (P>P rated ) ○ At least the wind turbine speed Va is negative (V a <0) and wind speed V w V r Greater than (V w >V r ) The blade pitch angle A is greater than At only during a portion of the time (A>A t ) is established, and the generator is rated Less than the output P(P <P rated )

[0045] The way in which the control system establishes the pitch angle A may consist of adding a particular value or variation to A until a particular target condition (e.g., a particular rotational speed of the rotor) is reached, or by other methods or algorithms known in the art.

[0046] In a preferred embodiment of the method of the present invention, t (A t ) is established, and the generator operates at a pitch angle of V a >0 if and only if P rated Output P greater than (P>P rated In a preferred embodiment of the method of the present invention, the power output during the forward movement cycle is equal to or greater than the rated power output P rated and more preferably, the power output during the forward movement cycle is greater than 15% above rated power output.

[0047] In a preferred embodiment of the method of the present invention, the variable P max is additionally used, where ○ P max The value of is determined dynamically and can therefore be different at each instant in time. ○ P max As wind speed and / or rotor speed increase, P max If the generator output tends to produce a power greater than P​​max is defined as the upper power threshold P allowed by the control strategy above which action is taken by increasing the blade pitch angle A to prevent and / or correct And here, ○ The variable P max P rated and / or ○ The variable P max P rated is assigned a value equal to

[0048] In another preferred embodiment of the method of the present invention, the variable P min is used, where: ○ P min The value of is established dynamically and can therefore be different at each instant in time. ○ P min is defined as the lower power threshold, above which the control system determines if A>0 and the wind speed and / or rotor speed are decreasing to reduce P min 4. If the generator tends to produce less power than the normal speed, action is taken to reduce the blade pitch angle A by reducing the blade pitch so as to maintain and / or increase the generator power output. And here, ○ The variable P min P rated and / or ○ The variable P min P rated A value less than is assigned.

[0049] In another preferred embodiment of the method of the present invention, the variable P target is used, where: ○ P targetThe value of is established dynamically and can therefore be different at each instant in time. ○ P target is defined as the target output that the control system seeks to produce at a particular instant in time. Variable P target The value of must be at least V a is established depending on the value of And here, ○ The variable P target P rated is assigned a larger value and / or ○ The variable P target P rated A value less than is assigned.

[0050] Variable P target The value of V w The variable P may further be determined depending on the value of the rotational speed of the rotor. target The value of may further be determined depending on the values ​​of the tilt and / or acceleration of the wind turbine, which may be used to determine the control method V a At a future moment, V a It may be possible to predict the value of

[0051] In one embodiment of the method of the present invention, P target =P rated While the wind turbine V a The absolute value of the velocity of a,lim Thus, due to the reduced displacement, the control method can thereby be maintained similar to the method used in standard fashion on a fixed structure, and the displacement increases and the speed of the wind turbine is kept below said threshold value V a,lim , the method according to the invention is used to better damp said movements.

[0052] In another preferred embodiment of the method of the invention, the value of the blade pitch angle A is determined in accordance with the speed V ais established taking into account the value and / or sign of

[0053] In another preferred embodiment of the method of the invention, the value of the blade pitch angle A is defined in two phases. ○ Theoretical pitch angle A t are calculated using rules identical or similar to those used for a standard control system of said wind turbine when operating on a fixed substructure. a second phase of applying a correction to said theoretical pitch value of the blade to establish an actual pitch value to be applied, said correction being established according to at least one of the following rules: ■ If the wind turbine speed is positive, apply a correction to the theoretical pitch value that prevents, reduces or retards the pitch increase. ■ If the wind turbine speed is negative, a correction is applied to the theoretical pitch value which prevents, reduces or delays the reduction of pitch.

[0054] In another preferred embodiment of the method of the present invention, ○ At least the wind turbine speed is positive (V a >0) and V w >V r and / or during a portion of the time when the control system does not allow an increase in the blade pitch angle A; ○ At least when the wind turbine speed is negative (V a <0) and V w >V r During the portion of time when , the control system does not allow a reduction in the blade pitch angle A.

[0055] In another preferred embodiment of the control method of the invention, said control is exerted only in the event of wind turbine movements having certain amplitude and / or speed thresholds.

[0056] In another preferred embodiment of the method of the invention, the method comprises monitoring a temperature in the wind turbine by means of a sensor, the variable Pmax and / or P target The value to which is assigned at each instant depends on the temperature measured at the generator.

[0057] In another preferred embodiment of the method of the invention, the method comprises monitoring the voltage in the wind turbine by means of a sensor, the variable P max and / or P target The value to which is assigned at each instant depends on the voltage measured at the generator.

[0058] In another preferred embodiment of the method of the invention, said method is used on a wind turbine supported by a highly flexible non-floating substructure, the first vibration mode of which has a period of 3 seconds or more.

[0059] A second object of the invention relates to a computer program product implementing instructions for carrying out the method according to any of the embodiments described herein.

[0060] A third object of the present invention relates to a control system for controlling a wind turbine (1), characterized in that it includes one or more monitoring sensors for monitoring physical parameters of the wind turbine and software / hardware means configured to execute the method according to any of the embodiments described herein.

[0061] A fourth object of the invention relates to a wind turbine using a control method or a control system according to any of the embodiments described herein.

[0062] In a preferred embodiment of the present invention, the wind turbine has a rated power P rated and capable of temporarily producing an output P greater than rated The overproduction period (P>P) includes a generator and / or electrical system that is intercalated with a period during which a power output P is generated that is less than P. rated) duration and frequency are determined by the time the wind turbine reaches a positive speed (V a >0), as well as the duration and frequency of phases moving through the wind turbine. Standard wind turbine specifications may generally meet this condition, particularly as a result of periods of overproduction being intercalated with periods of underproduction, as made possible by the method of the present invention.

[0063] The above-mentioned embodiments should not be understood as limiting the protection scope of the present invention, which comprises all technically possible combinations thereof, provided that they are not mutually exclusive.

[0064] The term "substantially" as applied to any of the terms used herein is understood to mean the same or comprised within a margin of variation of 20% above and below.

[0065] The above and other features and advantages will become more apparent from the detailed description of the present invention and from the preferred embodiments referred to in the accompanying drawings. [Brief description of the drawings]

[0066] [Figure 1] 1 shows a representation of the pitch angle A of a wind turbine blade. [Diagram 2] 1 shows graphs of variation of the following magnitudes depending on wind speed Vw using a conventional controller: a) power P vs. wind speed Vw, b) blade pitch angle A vs. wind speed Vw, c) thrust T vs. wind speed Vw. [Figure 3a] Two expressions for the velocity Va of the wind turbine as a result of the motion of the floating structure supporting the wind turbine are shown. [Figure 3b] Two expressions for the velocity Va of the wind turbine as a result of the motion of the floating structure supporting the wind turbine are shown. [Figure 4a]Graphs corresponding to a forward moving cycle (Va>0) and a backward moving cycle (Va<0) are shown, showing how said cycles affect the apparent velocity Vw incident on the rotor compared to a situation where the wind turbine remains substantially stationary. [Figure 4b] Graphs corresponding to a forward moving cycle (Va>0) and a backward moving cycle (Va<0) are shown, showing how said cycles affect the apparent velocity Vw incident on the rotor compared to a situation where the wind turbine remains substantially stationary. [Figure 5a] FIG. 1 depicts a series of graphs showing how different variables or parameters for the operation or control of a wind turbine evolve over time and how some of said parameters differ for a fixed wind turbine or a wind turbine with a conventional controller and when using the method of the present invention. [Figure 5b] FIG. 1 depicts a series of graphs showing how different variables or parameters for the operation or control of a wind turbine evolve over time and how some of said parameters differ for a fixed wind turbine or a wind turbine with a conventional controller and when using the method of the present invention. [Figure 5c] FIG. 1 depicts a series of graphs showing how different variables or parameters for the operation or control of a wind turbine evolve over time and how some of said parameters differ for a fixed wind turbine or a wind turbine with a conventional controller and when using the method of the present invention. [Figure 5d] FIG. 1 depicts a series of graphs showing how different variables or parameters for the operation or control of a wind turbine evolve over time and how some of said parameters differ for a fixed wind turbine or a wind turbine with a conventional controller and when using the method of the present invention. [Figure 6]1 shows graphs of variation of the following magnitudes depending on the wind speed Vw in a first embodiment of the present invention: a) power P vs. wind speed Vw, b) blade pitch angle A vs. wind speed Vw, c) thrust T vs. wind speed Vw. [Figure 7] 1 shows variation graphs for the following magnitudes depending on wind speed Vw for a second embodiment of the invention having variable Pmax and Pmin: a) power P vs. wind speed Vw, b) blade pitch angle A vs. wind speed Vw, c) thrust T vs. wind speed Vw. [Figure 8] 1 shows a flow chart of the method of the present invention according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] A detailed description of the present invention is provided with reference to different preferred embodiments thereof in accordance with the information provided by Figures 1 to 8 herein. The foregoing description is provided for illustrative and non-limiting purposes of the claimed invention.

[0068] Figure 1 shows diagrammatically how the pitch angle (A) of the blades (3) can be varied: Figure 1a shows the minimum pitch angle (A=0) situation, which maximizes the exposure of the blades (3) to the wind and therefore the production capacity of the wind turbine (1), whereas Figure 1b shows the maximum pitch angle (A=approximately 90 degrees) situation, which places the blades (3) in a feathered position and minimizes their exposure to the wind (see also the definition of the pitch angle A of the blades (3) contained in the previous section).

[0069] To vary the pitch angle (A) of the blades, the wind turbine (1) includes regulation means, usually consisting of a series of bearings and hydraulic actuators (not shown in FIG. 1) controlled by a control system for controlling the wind turbine (1).

[0070] Figure 2 shows a series of three curves describing the behavior of a conventional controller or control method, such as those typically used for wind turbines operating on a fixed structure. Figures 3a, 3b, and 3c respectively show how the power output (P), the blade pitch angle (A), and the horizontal thrust (T) exerted by the wind on the rotor (2) vary depending on the wind speed (Vw).

[0071] For low wind speeds below a reference value "Vr" called "rated wind speed", a minimum blade pitch angle A (A=0) is maintained to maximize production (see FIG. 2b). In said situation, the power generated is less than the rated power "P rated " because the wind speed "Vw" is less than "Vr" (see Figure 2a).

[0072] When the wind speed reaches a value Vr, the wind turbine (1) can start generating electricity at its rated power. When the wind speed Vw exceeds Vr (Vw>Vr), the control system that controls the wind turbine (1) increases the pitch angle A of the blades (3), so that the production power P increases to "P rated " (see Figures 2a and 2b).

[0073] Therefore, for a particular theoretical value At of the blade pitch angle (At>0), the generated power P is equal to or exceeds the rated power P rated For each wind speed Vw>Vr, the theoretical pitch angle At1 of the blades (3) corresponds to a production power P equal to the rated power of the turbine (1) (P=P rated ).

[0074] The horizontal thrust T exerted by the wind on the rotor (2) increases with the wind speed while Vw < Vr (positive curve slope, see Figure 2c). However, when Vw > Vr and pitch starts to act, the situation reverses, and a higher wind speed Vw results in a lower thrust T (negative curve slope, see Figure 2c). This latter situation leads to the negative damping phenomenon in the Vw > Vr situation already described in the previous background section.

[0075] The operation with Vw > Vr is called the above-rated operation, while the operation with Vw < Vr is called the below-rated operation. The value of Vr may vary depending on the model (1) of the wind turbine. A common value of Vr is about 12 m / s.

[0076] Figures 3a and 3b schematically show the possible movements that the wind turbine (1) may undergo. The wind turbine (1), in this case, is supported by a floating substructure (4), which generally enhances said movements. Figure 3(a) shows a movement substantially opposite to the wind direction (Va > 0), while Figure 3(b) shows a movement substantially coinciding with the wind direction (Va < 0). Said movements and / or speeds are basically caused by changes in the inclination of the floating substructure (4), but they may also be caused, at least in part, for example, by the horizontal displacement of the substructure (4) or the deformations undergone by the substructure (4).

[0077] Figure 3a shows, as an example, a floating substructure (4) formed by two bodies, but the present invention also applies to wind turbines supported by other types of substructures.

[0078] The control method according to the invention offers considerable advantages for wind turbines that undergo significant movements and is therefore particularly suitable for floating wind turbines. However, it may also be advantageously used for wind turbines mounted on other highly mobile and / or highly flexible substructures without departing from the scope of the invention. For example, the control system according to the invention may also be used for wind turbines mounted on very flexible towers whose deformations generate significant movements in the wind turbine (1). For example, what are commonly known as soft towers are towers that have high natural oscillation periods, usually exceeding values ​​of 3s (higher than the rotation period of the rotor (2)), with associated deformations, negative effects which may be prevented or mitigated by the invention.

[0079] The movements undergone by the wind turbine (1) are generally cyclical, such that movement cycles with Va>0, referred to herein as forward movement cycles, are intercalated with movement cycles with Va<0, referred to herein as backward movement cycles. This is shown diagrammatically in Figure 4b, where it can be seen how the speed Va of the wind turbine (1) evolves over time and how the forward and backward movement cycles generally intercalate with each other.

[0080] Figure 4a shows how the wind speed Vw is affected by the movement of the turbine (1). The red curve in the graph of Figure 4a shows how the absolute wind speed evolves over time when exposed to natural disturbances or fluctuations, said red curve representing the wind speed Vw for a completely fixed wind turbine (1). The green curve in the same graph then represents the apparent or relative wind speed Vw with respect to the rotor (2) when the rotor (2) is not fixed but rather moves at a speed Va as shown in Figure 4b. During the backward movement cycle (Va<0), the apparent or relative wind speed Vw decreases with respect to the absolute wind speed, whereas during the forward movement cycle (Va>0), the apparent or relative wind speed Vw increases with respect to the absolute wind speed shown in the red graph.

[0081] Looking at the graph in Figure 4(b), it can be considered that when the curve of the speed Va of the wind turbine (1) crosses the x-axis, a new forward or backward moving cycle begins. The wind speed Vwi (see Figures 4a and 4b) measured at the moment when a particular cycle i begins can be a parameter used in the algorithm that controls the control method according to the invention, as will be explained below.

[0082] Figure 5 represents a series of graphs showing how different variables or parameters of the operation or control of a wind turbine (1) evolve over time. To better explain and understand the invention, on the one hand, a typical behavior of a conventional controller (1) with a fixed turbine is shown using a red curve, and on the other hand, a typical behavior of a controller or control method according to the invention in the case of a floating turbine (1) subjected to movements is shown using a green curve. The graphs correspond to a situation above rated operation (Vw>Vr) and show different magnitudes of evolution over time. The x-axis of all graphs is on the same scale and represents the same time period.

[0083] Figures 5a and 5b are similar to Figures 4a and 4b, but in the case of Figure 5, in order to make it easier to explain and illustrate it, it has been assumed in a simplified way that the absolute wind speed is constant over time. Thus, the graph of Figure 5a shows, with a red horizontal curve, the absolute wind speed, which affects a completely stationary wind turbine (1), in this case having a constant value and equal to Vw1. Then, in the same graph, a green discontinuous curve shows the wind speed Vw applied to a moving wind turbine (1) according to the speed curve of the wind turbine (1) shown in Figure 5b. The corresponding intercalated forward and backward moving cycles can be observed.

[0084] In order to eliminate or reduce the effects of negative damping and / or movements experienced by the wind turbine (1) and / or to increase or improve the positive damping of said movements and / or to increase energy production in the wind turbine (1), the control method according to the invention performs operations as shown in Figures 5c and 5d (for the wind speeds and wind turbine (1) conditions shown in Figures 5a and 5b).

[0085] Figure 5d shows the variation of the pitch angle of blade A over time. The horizontal red line represents the case of a fixed wind turbine (1), which adopts a theoretical value At1 for the pitch angle of the blades, following a curve such as the one shown in Figure 2b, for a wind speed Vw1>Vr. The theoretical value At1 corresponds to the rated power P rated The constant and P that exists in a fixed wind turbine (1) with a conventional controller rated is represented by the horizontal red line in FIG. 5c.

[0086] However, since there is movement within the wind turbine (1), the velocity Vw varies as shown by the green curve in Fig. 5a. The conventional controller applies the theoretical pitch angle of the blade (3) to the variation in Vw that enables the generated output to be maintained substantially constant and equal to Prated. The theoretical value At is obtained from a graph such as the one shown in Fig. 2b and is linked to the variation of Vw, and their change over time is shown by the dotted black curve represented in Fig. 5d. Using the value At for the pitch of the blade (3) enables the output to be maintained substantially constant and equal to the rated output, but it results in the undesirable negative damping effect described in the above section. To prevent or reduce the negative damping effect, the control method according to the present invention employs a value of the pitch angle A of the blade (3) as represented by the discontinuous green curve in Fig. 5d. As can be seen from the curve, the value is such that during the forward movement cycle (Va > 0), A (discontinuous green curve) is less than At (dotted black curve) (A < At). Otherwise, in the backward movement cycle, A > At.

[0087] Next, the output obtained from the wind turbine (1) is represented by the discontinuous green curve in Fig. 5c. During the forward movement cycle (Va > 0), the output P generated by the wind turbine (1) is P rated greater than, while during the backward movement cycle (Va < 0), the generated output P is P rated less than.

[0088] It should be indicated that although the rated power is generally a fixed constant value over the useful life of the wind turbine, in certain cases or wind turbine models it may be possible to adjust its value for certain operating conditions or depending on certain parameters, such as the generator voltage, the reactive power generated as required by the network system, or the room and / or generator temperature. Thus, in one embodiment of the invention it is possible to use a correction value for the parameter Prated that, under certain conditions, may differ from the rated power listed in the technical data sheet of the specific wind turbine model, without affecting the operating steps and rules characterizing the method according to the invention and thus remaining within their ranges.

[0089] It should be understood that there are a wide variety of possibilities or strategies for the control algorithm of the method according to the invention. For example, target An algorithm can be used to fix A, and the value of A established or resulting at each instant can be derived from the target output, or else a specific value of A can be established and the output value can be derived from a value of A that can be fixed. Several other possibilities are possible as well that are obvious or known in the art.

[0090] As can be seen in FIG. 5c, the controller or control method according to the invention can also detect other under-production periods (P <P rated ) and intercalated short-lived intermittent over-production phases (P>P rated) compared to the even production situation of a stationary wind turbine (1) (represented by the red line in FIG. 5c), periods of relatively more energy are produced (areas shaded in green in FIG. 5c corresponding to forward moving cycles) alternate with periods of relatively less energy (areas shaded in red in FIG. 5c corresponding to backward moving cycles). In the overall calculation, the under-production periods are offset by periods of overproduction to prevent or reduce possible energy losses. The control method according to the invention can even result in an increase in energy production, since the overproduction is greater than the underproduction. This can be due to the fact that the energy produced is proportional to the cube of the wind speed Vw. This means that for the same change in Vw for the forward and backward moving cycles, the gain for the forward moving cycle is greater than the gain for the backward moving cycle. For example, if Vw increases by 10% during the forward movement cycle and decreases by 10% during the backward movement cycle as well, then 1.1^3+0.9^3=1,331+0.729=2.06>2, thereby generating more energy than by working at constant power. The control method according to the invention thereby provides a way in which part of the energy associated with the movement of the structure can be extracted by the wind turbine (1).

[0091] The periodic and alternating variations in output are an important factor in the control method according to the present invention. In practice, P may vary indefinitely or for long periods of time due to limitations of the generator and / or other components. rated In contrast, when the overproduction periods associated with forward shift cycles are short and intercalated with the underproduction periods associated with backward shift cycles, the use and demand on the generator or other components of the electrical system decreases, resulting in a nearly constant and rated power output P. rated This is similar to what may occur in a production situation with an output equal to

[0092] Furthermore, the shorter duration of the forward and / or reverse cycles, which typically last for a few seconds or tens of seconds, can limit the expected power increase and decrease, since the rotor (2) has a high rotational inertia and therefore a certain time is required for the greater torque of the wind on the rotor (2) to increase its rotational speed or for the lower torque of the wind to decrease its rotational speed. Taking this into account, in a preferred embodiment of the invention, the generated power P above the rated power is at least partially regulated by varying the rotational speed of the rotor (2). Thereby, the increase in power associated with the forward cycle is reduced and / or delayed, since it takes time for the increase in angular momentum associated with the higher rotational speed to be exerted on the rotor (2), and the decrease in power in the reverse cycle is similarly reduced and / or delayed, since it takes time to translate the decrease in torque generated by the wind into a corresponding decrease in the rotational speed of the rotor (2) due to the high rotational inertia of the mass of the rotor (2).

[0093] Using the rotational speed of the rotor (2) as a parameter for adapting the power output in the generator by including the rotational inertia of the rotor (2) and expressing the change in its angular momentum that requires a certain time leads to lower amplitude power oscillations at the rated operation (see FIG. 5c), thereby producing a potentially favorable effect. This can be achieved without departing from the scope of the invention by reducing the forward movement cycle P <P rated The initial part and / or the backward movement cycle P>P rated It also gives rise to certain differences between the output oscillations and the Va oscillations that may be temporarily involved in the initial part of

[0094] Power regulation in accordance with the present invention may also be achieved by varying the generator torque or by a combination of varying the rotor torque and rotational speed.

[0095] There are various specific strategies for establishing the value of the pitch angle A of the blade (3) used without departing from the scope of the present invention. By way of example, FIG. 5d shows the following various cases. - In cycles 1 and 2, a strategy is applied in which the pitch angle A of the blade is maintained constant despite the change in Vw. - In cycles 3 and 4, the pitch angle A is maintained constant until the output threshold is reached, and above the threshold, the pitch angle A begins to change. - In cycle 5, a stepwise change in Ano is applied throughout the cycle.

[0096] Whatever the specific strategy used to establish the exact value of A, the control method according to the present invention ensures that, at least, the value A < At is always established during a portion of the time when Va > 0 (forward movement cycle) which generally coincides with the overproduction period (P > P rated ) and that, at least, the value A > At is always established during a portion of the time when Va < 0 (backward movement cycle) which generally coincides with the underproduction period (P < P rated ).

[0097] By preventing or reducing the increase in A during the forward movement cycle, the control method prevents or limits a possible decrease in the wind thrust that resists movement during the forward movement cycle. Similarly, by preventing or reducing the decrease in A during the backward movement cycle, the control method prevents or limits a possible increase in the wind thrust that amplifies movement during the forward movement cycle. In that sense, the control method according to the present invention limits or eliminates an undesirable negative damping effect and may even generate a positive damping instead during operation above rated, as generally occurs during operation below rated.

[0098] As a non-limiting example, FIG. 6 shows a first embodiment of the control method according to the present invention. FIG. 6b specifically shows the value of the pitch angle of the blade (3) to be adopted during a particular cycle in the situation of operation above rated, whether it is a forward movement cycle or a backward movement cycle. The graph of FIG. 5b shows the following curves. - The red curve shows the value of A depending on Vw adopted by conventional controllers. The curve shows the rated power P for each wind speed Vw>Vr. rated FIG. 1 shows the theoretical pitch angle At of the blades (3) that results in a power output P equal to - a green curve corresponding to the value of the blade pitch angle A that an embodiment of a control method according to the invention establishes for a forward movement cycle (Va>0). It can be observed that the value of A shown in said green curve is always less than or equal to At. - a blue curve corresponding to the value of the blade pitch angle A that an embodiment of the control method according to the invention establishes for the rearward movement cycle (Va<0). It can be observed that the value of A shown by said green curve is always greater than or equal to At.

[0099] The green and blue curves correspond to a particular forward or reverse moving cycle where the wind speed Vw has a value Vwi at the start of the cycle (see Figure 4). Thus, the curves for cycles started at a different speed will be different but similar.

[0100] The method may establish a target value for A according to the rules of the above method such that a value of P results, or the method may establish a target value for P (using the variable Ptarget) such that a value of A results. Other similar or equivalent strategies may be possible for implementing the method of the invention that produces behavior such as that shown in Figure 5 and / or Figure 6.

[0101] The theoretical description of the control method according to the invention concerns the wind speed Vw as a possible control parameter, but in practical application of the method, it may generally be simpler and more efficient to use another parameter that is directly related to Vw, but easier to measure and monitor, such as the speed of the rotor (2) or the generator, as is typical in conventional controllers. Similarly, in practical application of preferred embodiments of the control method according to the invention, the value of Va is not measured directly, but rather is obtained indirectly from measurements of other relevant parameters, such as the tilt and / or acceleration, in particular of the wind turbine (1). In general, the control method according to the invention below can be used by using other control parameters that are directly related to the parameters used in the description of the method, without departing from the scope of the invention. For example, instead of the speed Va, the angular velocity of the floating structure, obtained from the rate of change of the tilt, which is equivalent, can be used as a control parameter, or instead of the wind speed, the rotor speed, which is directly related, can be used for a known generator torque value.

[0102] As explained, the velocity Va is generated by the change in the inclination of the floating support structure, which is generally the most influential parameter, and by other parameters, such as, for example, the horizontal displacement of the floating support structure or the deformation of the floating support structure, which are generally less influential parameters. In a preferred embodiment of the method according to the invention, the velocity Va is determined in an approximate manner only from the change in the inclination of the structure, without taking into account, for example, the horizontal displacement of the structure. This allows the method according to the invention to be particularly effective in damping and / or reducing the movements caused by the inclination of the structure, which is generally the most relevant movement. Naturally, embodiments in which Va is determined from other parameters in addition to or instead of the inclination of the structure are also possible without departing from the scope of the invention.

[0103] Figure 6a shows that the output generated by the wind turbine (1) is a backward movement cycle (blue curve) or a forward movement cycle (green curve) corresponding to the variation curve of the pitch angle A shown in Figure 6b, both for operating conditions above the rated value. P≥P in the forward movement cycle rated and P≤P in the backward movement cycle rated can be seen.

[0104] Similarly, the graph shown in Figure 6c shows what the variation of the thrust T applied by the wind on the rotor (2) is depending on the speed of the acting wind by applying this method in the forward movement cycle (green curve) or the backward movement cycle (blue curve). As can be seen from the green curve, in the forward movement cycle, the thrust T is always increased compared to the value of the cycle start speed Vwi. At the same time, as can be seen from the blue curve, in the backward movement cycle, the thrust T is always decreased compared to the value of the cycle start speed Vwi. Thereby, a change in T that resists the movement (increasing T in the forward movement cycle and decreasing T in the backward movement cycle) is achieved, thereby achieving a preferably positive damping.

[0105] Figure 6c represents the slope S of the curve defining T when Vw > Vwi (in the forward movement cycle) and Vw < Vwi (in the backward movement cycle). The said slope is a function of the curve defining A and / or the P used in the method (such as the method shown in Figures 6b and / or 6a for example). When the said slope S is positive (as in the embodiment of the method shown in Figure 6c), the method is capable of generating an appropriate positive damping for operation above the rated value in a manner similar to that of operation below the rated value where the slope of the curve (red curve for Vw < Vr) is significantly positive. If another embodiment of the method generates a negative slope S, no positive damping is generated, but since the said negative slope is less significant than the slope of the red curve for the same value of Vw, the unfavorable negative damping effect is at least partially reduced.

[0106] 7 shows a diagram similar to that of FIG. 6 for a second embodiment of a control method according to the invention, also for above-rated operating conditions (Vw>Vr). In this case, the control method uses a variable P max and the variable P that establishes the low output value. min and, when a power threshold is exceeded, a value of A is established that prevents exceeding the upper threshold, and when a low power value is exceeded, a value of A is established that prevents output below the lower threshold.

[0107] The control method according to the invention comprises the steps of: determining whether said variable P has a variable value that is established dynamically and / or in real time, taking into account various parameters or circumstances, such as: max and P min Assume the following. - the type of forward or reverse shift cycle in which the turbine (1) is located, i.e. the sign Va. - Generator temperature. - Generator voltage. - the value of the wind speed Vwi at the start of the forward or reverse cycle with the turbine (1).

[0108] As can be seen in FIG. 7a, in this embodiment of the method, P≧P rated (green curve), but to limit excess output and / or production, an upper threshold P max >P rated Similarly, a lower threshold P min =P rated is established in the forward movement cycle (the lower threshold P min is also established in the embodiment shown in FIG.

[0109] As can also be seen in FIG. 7a, in this embodiment of the method, P≦P rated (blue curve), but with a lower threshold P min <P rated Similarly, in the backward movement cycle, an upper threshold P max =Prated is established (the upper threshold is also established in the embodiment shown in FIG. 6).

[0110] Finally, Figure 8 shows a flow chart corresponding to the control algorithm used in the embodiment of the method of the invention shown in Figure 7. On the other hand, Figure 8a shows a flow chart used according to the current state of the art in a conventional controller, which results in a behavior curve like the one represented in Figure 2 in the red curve of Figure 7. In said conventional controller, during above rated operation (Vw>Vr), the power output remains approximately constant, regardless of the direction of the movement (i.e. of the sign of Va) undergone by the wind turbine (1), and P rated is equal to.

[0111] In such a conventional controller, the above threshold Pmax and P min also exists and / or is implicit, and has an equal and constant value (P max =P min =P rated ) applies.

[0112] Conventional controllers according to the prior art are generally designed to prevent the wind turbine (1) from operating at a power output greater than the rated power, which does not necessarily mean that it will generate a power output greater than the rated power at a given time, but the possible situations of operating at a power output greater than the rated power that may occur with controllers known in the art are quite different in form, cause and / or motivation with respect to the situation of overproduction that is intentionally caused by the control method according to the present invention. For example, with conventional controllers, a situation of P>Prated may occur due to the instantaneous ability to adjust the pitch of the blades (3), so that in the event of a sudden increase in wind speed, there may be an increase in the power generated during the short time interval that the control system needs to react and adjust the pitch of the blades (3), the purpose of which is to correct said situation. This situation is obviously quite different from the one that characterizes the control method referred to in the present invention, and is a moment when P>Prated is predicted and is caused by the control algorithm itself, depending on the movements that the wind turbine undergoes, as for example depicted in Fig. 8b.

[0113] Figure 8b shows a flow chart of the control algorithm of the method according to the invention, which establishes, for above rated operation, the pitch angle A and the variables Pmax and Pmin, taking into account the sign of the speed Va of the wind turbine (1), as shown self-explanatory in the figure.

[0114] A control method according to the invention has been described which takes into account the sign of Va. It is of course possible to develop further embodiments of the method according to the invention which also take into account the value of Va. For example, the value of Va can be used to determine the variable P targetAlternatively, for example, a method can be used that maintains the conventional algorithm as long as the absolute value of Va does not exceed a certain value or threshold, which only applies the most advanced method according to the invention for high speeds of the wind turbine (1) above a certain threshold. Thus, the conventional method can be maintained as long as the speed Va is small and insufficient to generate a significant negative damping effect.

[0115] The positive aerodynamic damping effect provided by the control method according to the invention can be increased by establishing a decrease in A for the forward moving cycle (Va>0) and / or an increase in A for the rearward moving cycle (Va<0), and one way of achieving said improved damping in the control algorithm according to the invention is to increase P for the forward moving cycle. min >P rated and / or in the backward migration cycle, P max <P rated It consists of establishing [Prior art documents] [Patent documents]

[0116] [Patent Document 1] US Patent Application Publication No. 2006 / 0033338A1 [Patent Document 2] European Patent No. 2063110B1 [Patent Document 3] European Patent Application Publication No. 1719910A1 [Patent Document 4] European Patent No. 3004636B1 [Patent Document 5] European Patent No. 2924280B1 [Explanation of symbols]

[0117] 1. Wind turbine 2. Rotor 3. Blade 4. Substructure

Claims

1. 1. A method for controlling an offshore floating tower wind turbine, comprising: the wind turbine comprises a rotor with a plurality of blades, the wind turbine produces a power output P that varies over time and depends on the relative speed Vw at which the wind strikes the rotor, where P rated is the rated power output of the wind turbine that can be achieved when Vw is equal to or greater than a rated wind speed Vr; the wind turbine is For a given relative wind speed Vw, an increase in the pitch angle of the blades is accompanied by a decrease in the rotational speed of the rotor and / or the power P generated and / or the thrust exerted by the wind on the rotor; For a given relative wind speed Vw, a reduction in the blade pitch angle A is accompanied by an increase in the rotational speed of the rotor and / or the power generated and / or the thrust exerted by the wind on the rotor; ■ the pitch angle of said blade has a minimum value, which by convention is assigned a pitch value of 0 degrees for said blade; ■ Given a relative wind speed Vw greater than Vr, there is a theoretical pitch angle At of the blades greater than 0 degrees such that the power P generated is equal to P rated . an adjustment means for adjusting the pitch angle A of the blade; o the wind turbine is subjected, in at least one operating condition, to a movement which generates a speed Va of the wind turbine, where Va is the total speed component of the wind turbine projected onto the shaft of the rotor, understood to be positive (Va>0) when the wind turbine is displaced in a direction against the wind direction and negative (Va<0) when the wind turbine is displaced in a direction consistent with the wind direction, the wind turbine comprises a sensor enabling the speed Va of the wind turbine to be monitored directly or indirectly, The control method includes: a pitch angle of the blades less than At (A<At) is established and the generator produces a power P greater than P>Prated (P>Prated) at least during a portion of the time when the speed Va of the wind turbine is positive (Va>0) and the relative wind speed Vw is greater than Vr (Vw>Vr); and / or a blade pitch angle (A>At) greater than At is established (A>At) at least during a portion of the time when the speed Va of the wind turbine is negative (Va<0) and the relative wind speed Vw is greater than Vr (Vw>Vr), and the generator produces a power P less than Prated (P<Prated), Control methods.

2. The variable Pmax is additionally used, The value of Pmax is established dynamically and can therefore be different at each instant of time; Pmax is defined as an upper power threshold P, permitted by the control method, such that if the relative wind speed Vw and / or the rotational speed of the rotor increase with a tendency to generate a power output greater than Pmax, action is taken to prevent and / or correct the power output at the generator from becoming greater than Pmax by increasing the pitch angle A of the blades; the variable Pmax is assigned a value greater than P rated at least during a portion of the time when the speed Va of the wind turbine is positive, and / or characterised in that the variable Pmax is assigned a value equal to P rated at least only during a portion of the time when the speed Va of the wind turbine is negative; The control method according to claim 1 .

3. The variable Pmin is used, The value of Pmin is dynamically established and can therefore be different at each instant of time; o Pmin is defined as a lower power threshold above which the control system acts to reduce the pitch angle A of the blades such that if A>0 and the relative wind speed Vw and / or the rotational speed of the rotor are decreasing tending to produce a power output below Pmin, action is taken to reduce the pitch of the blades in order to maintain and / or increase the power output of the generator; the variable Pmin is assigned a value equal to P rated at least during a portion of the time when the speed Va of the wind turbine is positive, and / or characterised in that the variable Pmin is assigned a value less than P rated only during a portion of the time when the speed Va of the wind turbine is negative, The control method according to claim 1 .

4. The variable Ptarget is used, o The value of Ptarget is established dynamically and can therefore be different at each instant in time; Ptarget is defined as the target output that the control system is trying to produce at a particular instant in time. the value of the variable Ptarget is established depending on at least the value of Va, the variable Ptarget is assigned a value greater than Prated at least during a portion of the time when the speed Va of the wind turbine is positive, and / or characterised in that the variable Ptarget is assigned a value less than Prated at least during a portion of the time when the speed Va of the wind turbine is negative; The control method according to claim 1 .

5. 2. The control method of claim 1, wherein the value of the pitch angle at the blades is established taking into account the value and / or sign of the speed Va of the wind turbine.

6. The value of the blade pitch angle is Including a correction to be applied to the theoretical pitch value of said blade to establish the actual pitch value to be applied, ■ if the speed Va of the wind turbine is positive, the correction prevents or limits an increase in pitch; ■ If the speed Va of the wind turbine is negative, the correction prevents or limits a reduction in pitch, such that establishing said correction according to said speed Va of said wind turbine; The control method according to claim 4.

7. o the control system does not allow an increase in the pitch angle A of the blades, at least during a portion of the time when the speed Va of the wind turbine is positive (Va>0) and Vw>Vr, and / or characterised in that, at least during a portion of the time when the speed Va of the wind turbine is negative (Va<0) and Vw>Vr, the control system does not allow a reduction in the pitch angle A of the blades; The control method according to claim 1 .

8. The method of claim 1 , wherein the control is applied only in the event of the wind turbine movement having a particular amplitude and / or speed threshold.

9. 5. A control method according to claim 2 or 4, comprising monitoring the temperature of the generator in the wind turbine by means of a sensor, the value assigned to the variables Pmax and / or Ptarget at each instant in time being dependent on the temperature measured at the generator.

10. 5. A control method according to claim 2 or 4, comprising monitoring the voltage of the generator of the wind turbine by means of a sensor, the value assigned to the variables Pmax and / or Ptarget at each instant in time being dependent on the voltage measured at the generator.

11. 11. The method of claim 1, wherein the method is used in a wind turbine supported by a highly flexible, non-floating structure, the first vibration mode of which has a period of 3 seconds or more.

12. A control system for controlling a wind turbine, characterized in that it comprises one or more sensors monitoring physical parameters of the wind turbine, adjusting means for adjusting the pitch angle A of the blades of the wind turbine, and software / hardware means configured to carry out the method according to any one of claims 1 to 11.

13. A wind turbine using a control method according to any one of claims 1 to 11 or comprising a control system according to claim 12.

14. 14. Wind turbine according to claim 13, characterised in that it comprises a generator and / or an electrical system capable of temporarily producing a power output P greater than its rated power output P rated during first periods having a duration of less than 100 seconds alternating with second periods during which a power output P less than P rated is produced.

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