Individual pitch control with unavailable blade load sensors

Abstract

The invention relates to a pitch adjustable rotor blade of a three-bladed wind turbine for pitch actuation in case one blade load sensor is not available. Based on blade load signals (L1, L2, L3) and an availability signal (v1, v2, v3) for each of the blade load signals, a combined load signal is constructed based on the available blade load signals. The determination of the combined load signal is based on applying a high-pass filter to the blade load signals and transforming (T1) the blade load signals to an intermediate coordinate system, wherein in the transformation the unavailable blade load signal is replaced by an estimation signal. Using the combined load signal a control action (CA) is performed and the resulting pitch correction signal (Δθ1, Δθ2, Δθ3) is applied to the pitch actuator.

Description

Technical Field

[0001] The present invention relates to pitch actuation in the event that a blade load sensor is unavailable. Background Technology

[0002] As is well known, a wind turbine consists of a tower that supports the nacelle and a rotor with multiple pitch-adjustable rotor blades.

[0003] For large wind turbines, controlling the blade pitch is often beneficial for reducing loads, such as mitigating asymmetrical loads on the rotor and excessive loads on the blades in the flapping or edge directions. In particular, excitation on the blades in the edge directions is generally undesirable because the damping in that direction is typically weak.

[0004] It is well known that individual pitch control is based on signals from blade load sensors (such as blade load sensors mounted in the root section of the blade). Individual pitch control typically relies on the availability of measurements from all three blade sensors. If one sensor goes offline and becomes unavailable, the wind turbine may de-split in a safe mode to ensure operation within its design load envelope. This results in reduced turbine operating efficiency, negatively impacting energy capture. Summary of the Invention

[0005] An improved approach to blade pitch control based on blade load sensor signals is advantageous. In particular, it is beneficial to provide a control system with a certain level of fault tolerance when the blade load sensor becomes unavailable.

[0006] Therefore, in a first aspect, a rotor control system is provided for actuating pitch-adjustable rotor blades of a three-bladed wind turbine, the rotor control system including a pitch actuation unit for determining a pitch correction signal to be applied to a pitch actuator so as to actuate the pitch of the pitch-adjustable rotor blades if one of the blade load signals is unavailable.

[0007] The pitch actuator unit is arranged as follows:

[0008] Receive the blade load signal of each of the pitch-adjustable rotor blades, and the availability signal of each of the blade load signals;

[0009] A combined load signal is constructed based on the available blade load signal, wherein the combined load signal is represented as a first signal component (A) and a second signal component (B) along a first reference direction and a second reference direction, respectively, in the reference frame;

[0010] Perform control actions (CA) on the first signal component and the second signal component; and

[0011] The pitch correction signal (Δθ1, Δθ2, Δθ3) is applied to the pitch actuator;

[0012] The combined load signal is constructed in the following manner:

[0013] A high-pass filter is applied to the blade load signal;

[0014] The blade load signal is transformed to an intermediate coordinate system using a first coordinate transformation (T1), wherein each of the associated components of the load signal in the intermediate coordinate system is orthogonal to each other, and wherein, in the transformation, the unavailable blade load signal is replaced with an estimated signal.

[0015] The first intermediate component is set as the first component of the transformed blade load signal generated by the first coordinate transformation (T1); and

[0016] The second intermediate component is set as the second component of the transformed blade load signal generated by the first coordinate transformation (T1);

[0017] Rotate the first intermediate component and the second intermediate component so that they are aligned with the reference system along the first reference direction and the second reference direction; and

[0018] The first signal component (A) and the second signal component (B) are respectively set as the first intermediate component and the second intermediate component after rotation.

[0019] In one embodiment, the pitch actuation unit may perform the above steps sequentially, or it may perform other steps between the above steps.

[0020] This invention provides a rotor control system that uses a pitch correction signal to actuate pitch-adjustable rotor blades to reduce blade load when a blade load sensor signal is unavailable. Embodiments of this invention enable the turbine to maintain normal operation, actively reducing load via pitch control even when one blade load signal is lost (and therefore only two blade load signals are available).

[0021] This can be achieved by providing an input signal to the controller that performs the control action, where the input signal is based on the load signal from an available load sensor. This is achieved by constructing a combined load signal based on the available blade load signals and using the combined signal in the control action.

[0022] The combined load signal is constructed by applying a high-pass filter to the blade load signal and using a first coordinate transformation to transform the two available blade load signals to an intermediate coordinate system, wherein each of the associated components of the load signals in the intermediate coordinate system is mutually orthogonal, and wherein, during the transformation, the unavailable blade load signals are replaced with estimated signals. Thus, the blade load signal values ​​initially obtained in a rotating coordinate system with axes 120 degrees apart are transformed into signal values ​​in an intermediate coordinate system where the axes are mutually normal.

[0023] By applying a high-pass filter and combining the estimated signals as unavailable signals, an accurate representation of all three load signals can be obtained in an intermediate coordinate system. In this system, the slapping (slapping) torque approximately corresponds to the thrust measurement, and the edge torque approximately corresponds to the torque measurement. In both cases, the variations in these signals are typically low-frequency. Therefore, by applying a high-pass filter, the influence of unavailable sensors can be filtered out, thus allowing for high-precision estimation of the unavailable signals.

[0024] In one embodiment, the estimated signal is a superposition of two available blade load signals. This can be achieved by constructing the estimated signal as a linear combination of the two available signals and offsetting it by a constant.

[0025] For a three-bladed turbine, three pairs of available blade load measurements can be performed: AB blade load pair, AC blade load pair, and BC blade load pair, where the three blades are named A, B, and C, respectively. If a sensor signal is unavailable, only one pairing is valid, where the specific pairing depends on the unavailable sensor signal; for example, if the sensor for blade C is unavailable, the only valid pairing will be the AB blade pair. A first intermediate component is set as the first component of the transformed blade load signal generated by the first coordinate transformation, and a second intermediate component is set as the second component of the transformed blade load signal generated by the first coordinate transformation. These intermediate components form a vector, which is then rotated to align with the reference frame along the first and second reference directions and applied as input to the control element to execute control actions operating in the stationary frame.

[0026] As input to the rotor control system, it receives the blade load signal and the availability signal of each of the blade load signals for each of the pitch-adjustable rotor blades. In this regard, if the blade load signal becomes unavailable, the blade load signal from the unavailable sensor will not be received; instead, an empty signal or a damaged signal will be received. If the signal is unavailable, the rotor control system will ignore any signal components still received from the corresponding load sensor.

[0027] Based on the input, a combined load signal is constructed. The combined load signal is represented in a reference frame along a first reference direction and a second reference direction, thereby providing a first signal component and a second signal component. The reference frame is the frame in which the control action is applied. In an embodiment, the reference frame is a fixed frame along the yaw moment direction and the tilting moment direction. The reference frame can also be a fixed frame along the rotor rotation direction. The control action is applied in the reference frame, thereby providing the generated first signal component and the generated second signal component. The controlled signal can be transformed back into the rotating frame to be applied as a pitch correction signal to the pitch actuator. This can be achieved by applying an m-blade coordinate transformation to the generated first signal component. The m-blade coordinate transformation can be an inverse Coleman transformation.

[0028] A key feature of this invention relates to coordinate transformation. Generally, coordinate transformation involves transforming a signal represented in a first coordinate system to a second coordinate system. A coordinate system can also be called a reference system. This coordinate transformation can be an m-blade transformation, also known in the art as a multi-blade transformation. Examples of coordinate transformations include the Clarke transform and the Coleman transform. However, other transformations can also fall into the category of coordinate transformations, namely the so-called DQ transform and the Park transform or similar transformations. Those skilled in the art can determine an alternative transformation, which may not strictly be a specific transformation, but can operate in an equivalent manner.

[0029] The coordinate transformations used in this paper can be applied either as is (i.e., without prefixes) or in reverse form. In this respect, signals can be measured, corrected, and actuated in the same or different coordinate systems. Specifically, the coordinate transformation can take a signal measured in a rotating reference or coordinate system, i.e., a signal obtained on the rotating blade, and transform that signal to a fixed reference system consisting of two components. The inverse m-blade transformation takes the two signal components and transforms them back to the rotating system to provide the signal components (pitch correction signals) that can be applied to the three pitch actuators.

[0030] In another aspect, the present invention relates to a wind turbine including a rotor control system according to the first aspect. In yet another aspect, the present invention relates to a method for actuating pitch-adjustable rotor blades of a wind turbine and a computer program product. The computer program product may be provided on a computer-readable storage medium or downloadable from a communication network. The computer program product includes instructions that, when loaded onto a data processing system, will cause the data processing system (e.g., in the form of a controller) to execute the instructions.

[0031] Generally, the rotor control system can be implemented on a single unit or a set of functional units, the unit including one or more processors, input / output interfaces, and a memory capable of storing instructions that can be executed by the processor.

[0032] Generally, various aspects of the present invention can be combined and coupled in any possible manner within the scope of the invention. These and other aspects, features, and / or advantages of the invention will become apparent from the embodiments described below and will be elucidated with reference to the embodiments described below. Attached Figure Description

[0033] Embodiments of the invention will be described by way of example only, with reference to the accompanying drawings, wherein:

[0034] Figure 1 An example of a wind turbine is illustrated in the diagram.

[0035] Figure 2 This is a schematic diagram illustrating one embodiment of a feedback speed controller;

[0036] Figure 3 An embodiment of the pitch actuator is schematically illustrated; and

[0037] Figure 4 The diagram illustrates the application. Figure 3 The illustrated embodiment simulates a load signal. Detailed Implementation

[0038] Figure 1 An example of a wind turbine 1 is illustrated schematically. The wind turbine 1 includes a tower 2, a nacelle 3 mounted atop the tower, and a rotor 4 operatively coupled to a generator housed within the nacelle 3. In addition to the generator, the nacelle houses various components necessary for converting wind energy into electrical energy, as well as various components required for operating, controlling, and optimizing the performance of the wind turbine 1. The rotor 4 of the wind turbine includes a central hub 5 and three blades 6 extending outward from the central hub 5. Furthermore, the wind turbine includes a control system. This control system can be located within the nacelle, on the tower, or distributed across multiple locations inside (or outside) the turbine and is communicatively connected. The rotor blades are pitch-adjustable. The rotor blades can be adjusted according to a collective pitch setting, where each blade is set to the same pitch value. Additionally, the rotor blades can be adjusted according to individual pitch settings, where each blade is set to an individual pitch setpoint.

[0039] In embodiments of the invention, blade load signals of each of the pitch-adjustable rotor blades are used. These blade load signals can be measured at the blade root 9 using blade load sensors positioned at the root of each blade in a manner that allows the sensor to detect the load on the blade. Depending on the location and type of the sensor, the load can be detected in the flapping direction 10 (in-plane / out-of-plane) or in the edge direction 8 (in-plane). In embodiments, such sensors can be strain gauge sensors or optical Bragg sensors. Because the sensors are placed on the rotating blades, these load signals of each of the pitch-adjustable rotor blades are measured in the rotor's rotational reference frame.

[0040] Figure 2 This diagram schematically illustrates one embodiment of a feedback speed controller, implemented according to an embodiment of the invention, for determining a separate pitch actuation signal capable of reducing blade load. In the illustrated embodiment, the speed controller compares the actual rotor speed ω with a reference rotor speed ω. ref The speed error between (ω-ω) ref Minimize in order to output the requested power P (in the form of a power setpoint) and the collective pitch reference θ. col The speed controller, based on the collective pitch reference determined by the rotor speed, can also incorporate more sensor values ​​(in... Figure 2 The measurement set (ms) input to the speed controller is taken into account. The feedback speed controller can be implemented using PI, PID, or similar control schemes. In one embodiment, the speed controller can instead be a model predictive controller, which is arranged based on minimizing a cost function to determine the collective pitch reference and / or power reference.

[0041] Figure 2 The diagram further illustrates the blade load reduction control block, referred to as the pitch actuation unit (PAU). In the pitch actuation unit, the pitch correction signals (Δθ1, Δθ2, Δθ3) are determined based on input signals, which include the blade load signals. Figure 3 An embodiment of one implementation of a pitch actuator (PAU) is illustrated.

[0042] The PAU control unit determines the pitch correction signal (Δθ1, Δθ2, Δθ3) for each rotor blade. These signals are superimposed on the collective pitch reference to provide the resulting pitch correction signal (θ) that can be individually applied to the pitch actuator of the rotor blade. A ,θ B ,θ C ).

[0043] exist Figure 2In the illustrated embodiment, a collective pitch reference for the pitch-adjustable rotor blades is determined based on the rotor speed, and the resulting pitch correction signal is applied to the pitch-adjustable rotor blades. The generated pitch correction signal is then applied individually to each pitch-adjustable rotor blade; for each individual blade, the generated pitch correction signal is based on the collective pitch reference signal and the individual pitch correction signal. In one embodiment, the individual pitch correction signals are applied cyclically.

[0044] Therefore, based on the pitch correction signal of each rotor blade, a pitch-adjustable rotor blade is determined to produce a pitch actuation signal.

[0045] Figure 3 An embodiment of a pitch actuation unit (PAU) that determines pitch correction signals (Δθ1, Δθ2, Δθ3) based on blade coordinate transformations (T1, T2) is schematically illustrated.

[0046] Three blade load signals (L1, L2, L3) are acquired as sensor input signals; these can be blade load signals along the flapping direction or along the edge direction. These three blade load signals (L1, L2, L3) are acquired in a rotating reference frame and used as input. These blade load signals are transformed back to the reference frame by applying a first coordinate transformation T1, and the desired control action (CA) is applied to the signals in the reference frame. To bring the corrected signal back to the rotating frame for use as a pitch actuation signal, a second transformation T2 is applied, which is typically in the form of an inverse Coleman transform. In this way, the rotor load is affected in a way that reduces the measured rotor load.

[0047] In an embodiment of the invention, a rotor control system is provided that is capable of operating according to the general scheme defined above even when one of the blade load signals is unavailable (typically due to a failure of the blade load sensor).

[0048] In addition to the three blade load signals (one for each of the blades (L1, L2, L3), availability signals (v1, v2, v3) are also received or determined. If one of the blade load signals is unavailable, the pitch actuator will implement a combined load signal based on the available blade load signals. The combined load signal is determined to provide a first signal component (A) and a second signal component (B), upon which control actions can be performed to reduce the measured blade load.

[0049] Control actions can be applied to the first and second signal components to provide the generated first signal component (A') and the generated second signal component (B'). An inverse Coleman transform (T2) can be performed on the generated first and second signal components to obtain pitch correction signals (Δθ1, Δθ2, Δθ3). These pitch correction signals are then applied to the pitch actuator.

[0050] The combined load signals are determined in such a way that the rotor control system can operate with only two available blade load signals. The combined load signals are obtained in the first transformation T1, which is advantageously divided into several steps.

[0051] Key steps include applying a high-pass filter to the blade load signal, replacing the unusable blade load signal with an estimated signal, and using a first coordinate transformation (T1) to transform the remaining usable and valid blade load signals to an intermediate coordinate system, where each of the associated components of the load signal in the intermediate coordinate system is mutually orthogonal.

[0052] By applying a high-pass filter and combining the estimated signal as an unavailable signal, an accurate representation of all three load signals can be obtained in the intermediate coordinate system.

[0053] Transforming coordinate values ​​from a rotating coordinate system with axes 120 degrees apart (due to the blade position) to each mutually orthogonal coordinate system can be done using known transformations in electrical engineering, such as the Clarke transformation.

[0054]

[0055] Where (L1, L2, L3) are the three-blade load signals, and (v α ,v β ,v γ ) is the component of the associated component of the load signal in the intermediate coordinate system.

[0056] For example, the Clarke transform is applicable when the L3 signal is unavailable and is replaced by a linear transform of the available signal for estimating the superposition, for example, set as -(L1+L2)+κ:

[0057]

[0058] v γ The component is omitted because high-pass filtering makes it almost zero and also removes the κ factor from the resulting vector component.

[0059] In the transformation, the unavailable blade load signal is replaced with an estimated signal. Depending on the type of unavailable blade load signal, three cases arise, and three sets of intermediate components can be determined. In one embodiment, the unavailable signal (L...) UA ) was replaced with: L UA =-(L A1 +L A2 )+κ, where subscripts A1 and A2 refer to the first and second available signals, respectively. After passing through a high-pass filter, the constant κ is removed, and the three intermediate components can be determined as follows:

[0060] L3 signal unavailable:

[0061]

[0062] L1 signal unavailable:

[0063]

[0064] L2 signal unavailable:

[0065]

[0066] The transformation is performed using an appropriate representation of the load signal, with the first intermediate component v α The first component of the transformed blade load signal is set as the first component of the transformed signal generated by the first coordinate transformation, while the second intermediate component v β It is set as the second component of the transformed blade load signal.

[0067] It should be noted that when blade load sensors are paired, the two orthogonal components can be calculated via different but equivalent linear combinations.

[0068] To obtain the first signal component (A) and the second signal component (B), the first intermediate component and the second intermediate component are rotated to align with the reference frame along the first reference direction and the second reference direction. In one embodiment, the rotor azimuth angle Φ is used to align the first signal component and the second signal component with the nacelle fixed reference system (commonly referred to as the DQ system or yaw system). In this embodiment, the αβ-vector is obtained by the following rotation matrix:

[0069]

[0070] In the general case of applying a general estimation signal, the first signal component (A) and the second signal component (B) are obtained as described above: by, for example, using a Clarke transform coordinate system to an intermediate coordinate system, and then, as described above, by rotating the intermediate component to align it with the reference system for applying the control action.

[0071] In the specific case where the estimated signal is set as the negative sum of two available blade load signals, performing a coordinate transformation on the intermediate coordinate system, followed by rotating the intermediate components to align with the reference frame used for control actions, is equivalent to, or at least approximately equivalent to, applying a Coleman transform to the relevant set of intermediate components. In this case, the combined load signal can be constructed, thus simplifying the calculation:

[0072] Apply a high-pass filter to the blade load signal;

[0073] Set the unavailable blade load signal as an estimation signal, which is the negative sum of the two available blade load signals: -(L1+L2);

[0074] The Coleman transform is applied to the relevant available load signal and the estimated signal group to obtain the first signal component (A) and the second signal component (B), respectively.

[0075] In one embodiment, in addition to applying a high-pass filter to the blade load signal, a notch filter is also applied at the 3P blade passage frequency. In particular, notch filtering at the 3P blade passage frequency may be beneficial when the blade load signal is a blade load signal in the flapping direction. Generally, the notch filter can be applied at the frequency where the loads of all three blades are synchronized, in which case load interference will collectively appear on the blades. Besides the 3P blade passage frequency used for flapping loads, notch filtering can also be applied at frequencies such as 6P and 9P.

[0076] In one embodiment, the cutoff frequency of the high-pass filter is set below the 1P blade passage frequency, such as a decimal place below the 1P blade passage frequency, to ensure sufficient spacing between the cutoff frequency and the 1P frequency. In another embodiment, the cutoff frequency of the high-pass filter is set below the frequency of change in average wind speed. Again, the cutoff frequency can be set a decimal place below the 1P blade passage frequency. The change in average wind speed can be determined based on a predetermined determination prior to turbine installation, thereby based on historical data over a fixed period. The change in average wind speed can also be determined based on repeated determinations of average wind speed.

[0077] In an advantageous embodiment, the applied control action (CA) is the same regardless of whether all three blade load signals are available or only two blade load signals are available. A key advantage of embodiments of the invention is that its implementation allows the first and second signal components to be independent of the control action. In the event that one blade load signal becomes unavailable, the rotor control system can be implemented according to an embodiment of the invention to enable the first coordinate transformation (T1), while when all blade load sensors are available, the first and second signal components can be acquired in a different manner. For example, if all three available blade load signals are available, a conventional Coleman transform can be used.

[0078] If the load signals of two or three blades become unavailable, the turbine can be operated in a safe mode, such as in derating mode or shut down.

[0079] Figure 4 The diagram shows the application and non-application. Figure 3 The simulated signal of the embodiment. The dashed line in the figure comes from the situation where there are three available blade load sensors and no load reduction control action is applied (i.e., not enabled). Figure 3 The simulation was obtained under the condition of having two available load sensors and applying load reduction control (i.e., enabling PAU). The solid line comes from the simulation under the condition of having two available load sensors and applying load reduction control (i.e., enabling PAU). Figure 3 The simulation was obtained under the condition of PAU.

[0080] The load sensor is a blade load sensor, which takes the form of a blade root load torque sensor. It is arranged to detect the load torque of the blade in the edge direction, that is, the load torque in the line direction between the leading and trailing edges of the blade.

[0081] Figure 4 Figure A illustrates the time trajectory of the edge load signal for one of the rotor blades within the range of 400 to 430 seconds. These two signals overlap to some extent, with one trajectory (dashed line) 40A targeting... Figure 3 With PAU disabled and all three load sensors available, another track (solid line) 41A is for... Figure 3 The PAU is enabled and both load sensor signals are available.

[0082] In display Figure 4 FFT curve of signal A Figure 4In section B, the difference between the two signals can be observed more clearly. Here, signal 40B represents the case where the PAU is not enabled, while signal 41B represents the case where the PAU is enabled and only two load sensor signals are available. Signal components are visible at two frequencies: the rotor blade 1P frequency 42 and the edge frequency 43. As can be seen from the figure, since the rotor frequency remains unchanged, the signal components at the 1P peak are not different, but due to the increased pitch actuation reducing the load, the signal components at the edge frequency are significantly reduced. Therefore, embodiments of the present invention provide a rotor control system that effectively reduces turbine blade edge vibration even when only two load sensors are available.

[0083] Figure 4 C and Figure 4 Figure D illustrates the corresponding diagram for the so-called edge D component. This corresponds to... Figure 3 Signal A, i.e., the first signal component along the first reference direction. From Figure 4 As can be seen in D, in the DQ reference frame, the edge frequency components are divided into forward and backward components. The reduction in load is also clearly visible in this reference frame.

Claims

1. A rotor control system for actuating pitch-adjustable rotor blades of a three-bladed wind turbine, the rotor control system comprising a pitch actuation unit for determining a pitch correction signal to be applied to a pitch actuator so as to actuate the pitch of the pitch-adjustable rotor blades if one of the blade load signals is unavailable. The pitch actuator unit is arranged as follows: Receive the blade load signal of each of the pitch-adjustable rotor blades, and the availability signal of each of the blade load signals; A combined load signal is constructed based on the available blade load signal, wherein the combined load signal is represented as a first signal component along a first reference direction and a second reference direction in the reference frame. A ) and second signal component ( B ); Perform control actions (CA) on the first signal component and the second signal component; as well as The pitch correction signal (Δ) θ 1 , Δ θ 2 , Δ θ 3) Applied to the pitch actuator; The combined load signal is constructed in the following manner: A high-pass filter is applied to the blade load signal; Using the first coordinate transformation ( T1 The blade load signal is transformed to an intermediate coordinate system, wherein each of the associated components of the load signal in the intermediate coordinate system is orthogonal to each other, and wherein, in the transformation, the unavailable blade load signal is replaced with an estimated signal, which is the negative sum of two available blade load signals; Set the first intermediate component as the first coordinate transformation. T1 The first component of the transformed blade load signal generated; and The second intermediate component is set as the second component of the transformed blade load signal generated by the first coordinate transformation (T1); Rotate the first intermediate component and the second intermediate component so that they are aligned with the reference system along the first reference direction and the second reference direction; and The first signal component ( A ) and the second signal component ( B ) are set as the first intermediate component and the second intermediate component after rotation, respectively.

2. The rotor control system according to claim 1, wherein, The blade load signal is either a blade load signal along the flapping direction or a blade load signal along the edge direction.

3. The rotor control system according to claim 1 or 2, wherein, In addition to applying a high-pass filter to the blade load signal, a notch filter is also applied at the frequency at which the loads of all three blades are synchronized.

4. The rotor control system according to claim 1 or 2, wherein, The cutoff frequency of the high-pass filter is set to be lower than the 1P blade passage frequency.

5. The rotor control system according to claim 1 or 2, wherein, The cutoff frequency of the high-pass filter is set to be lower than the frequency of change of the average wind speed.

6. The rotor control system according to claim 1 or 2, wherein, Using the first coordinate transformation ( T1 Transforming the blade load signal includes applying the Clarke transform.

7. The rotor control system according to claim 1 or 2, wherein, The rotation of the first intermediate component and the second intermediate component is related to the rotation of the rotor azimuth angle.

8. The rotor control system according to claim 1 or 2, wherein, When all blade load signals are available, the first signal component and the second signal component are determined based on the available blade load signals, and the control action (CA) performed on the first signal component and the second signal component is the same as the control action (CA) performed on the first signal component and the second signal component when one of the blade load signals becomes unavailable.

9. The rotor control system according to claim 1 or 2, wherein the turbine operates in a safe mode when two or three blade load signals are unavailable.

10. The rotor control system according to claim 1 or 2, further comprising applying an m-blade coordinate transformation to the first signal component and the second signal component (…). T2 ), to obtain the pitch correction signal (Δ θ 1 , Δ θ 2 , Δ θ 3).

11. The rotor control system according to claim 1 or 2, further comprising: A collective pitch reference for the pitch-adjustable rotor blades is determined, the collective pitch reference being determined based on the rotor speed. The generated pitch correction signal is applied to the pitch-adjustable rotor blade, and the generated pitch correction signal is applied individually to the pitch-adjustable rotor blade. For each individual blade, the generated pitch correction signal is based on the signal of the collective pitch reference and the pitch correction signal.

12. A wind turbine comprising a rotor control system according to any one of claims 1 to 11.

13. A method for actuating pitch-adjustable rotor blades of a three-bladed wind turbine, the wind turbine including a pitch actuator for actuating the pitch-adjustable rotor blades, the method comprising: Receive the blade load signal of each of the pitch-adjustable rotor blades, and the availability signal of each of the blade load signals; A combined load signal is constructed based on the available blade load signal, wherein the combined load signal is represented as a first signal component along a first reference direction and a second reference direction in the reference frame. A ) and second signal component ( B ); Perform control actions (CA) on the first signal component and the second signal component; as well as The pitch correction signal (Δ) θ 1 , Δ θ 2 , Δ θ 3) Applied to the pitch actuator; The combined load signal is constructed in the following manner: A high-pass filter is applied to the blade load signal; Using the first coordinate transformation ( T1 The blade load signal is transformed to an intermediate coordinate system, wherein each of the associated components of the load signal in the intermediate coordinate system is orthogonal to each other, and wherein, in the transformation, the unavailable blade load signal is replaced with an estimated signal, which is the negative sum of two available blade load signals; Set the first intermediate component as the first coordinate transformation. T1 The first component of the transformed blade load signal generated; and Set the second intermediate component as the first coordinate transformation. T1 The second component of the transformed blade load signal is generated; Rotate the first intermediate component and the second intermediate component so that they are aligned with the reference system along the first reference direction and the second reference direction; and The first signal component ( A ) and the second signal component ( B ) are set as the first intermediate component and the second intermediate component after rotation, respectively.

14. A computer program product comprising software code adapted to control a wind turbine when executed on a data processing system, the computer program product being adapted to perform the method of claim 13.

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