Controllers for wind turbines

Abstract

A controller (100) for a wind turbine (1) comprises a power controller unit (101) for controlling the power output of a generator (10) included in the wind turbine (1). The power controller unit (101) operates the generator (10) according to a speed reference value (211, 213) and a power reference value (212, 214), the speed reference value (211, 213) and the power reference value (212, 214) being selected along a linear operating trajectory (204, 205) in a power versus speed diagram (200), the linear operating trajectory (205) comprising points (210) corresponding to a nominal power (212) and a nominal generator speed (211). The power controller unit (101) comprises a slider command (103) for selecting an angular position of the linear operating trajectory (204, 205) in the power versus speed diagram (200).

Description

Technical Field

[0001] The present invention relates to the field of controlling the operation of a wind turbine. Background Art

[0002] A wind turbine controller has several objectives; it must maximize power production, reduce and limit structural and electrical loads, and also reduce and limit acoustic noise emissions. Typically, a wind turbine controller comprises multiple controllers that are used to achieve the control objectives by individually controlling actuators for yaw direction, generator power (or torque) and blade pitch angle.

[0003] When operating in a subsidy-based market, a wind turbine is operated more or less at the highest possible electricity production. In the future, wind turbines will be sold to non-subsidy-based markets, where alternative uses of the turbines are expected to be relevant. The turbine may, for example, be operated at a curtailed level to be ready to quickly ramp up power in a balanced service configuration. A wind turbine may also be operated at a curtailed level because the electricity production is higher than the previous day's provision submitted. In this case, a fast ramp-up rate may not be required. The ability to ramp up to maximum production is closely related to the rotor speed of the turbine. If a fast ramp-up rate is required, the speed must be maintained at or close to the optimal operating point, i.e. the nominal speed, to avoid first accelerating the rotor before being able to produce optimal power.

[0004] In cases where a fast ramp-up rate is not required, it would be beneficial to reduce the rotor speed to get some load reduction, since for example tower fatigue loads are more closely related to rotor speed than power.

[0005] Therefore, there is a need for an improved way of controlling a wind turbine which can be operated at the highest possible power production or at a curtailed level. Summary of the invention

[0006] This need is met by the subject matter according to the independent claims. Advantageous embodiments of the invention are described by the dependent claims.

[0007] According to a first aspect of the invention, a controller for a wind turbine is provided, the controller comprising a power controller unit for controlling the power output of a generator included in the wind turbine, the power controller unit operating the generator according to a speed reference value and a power reference value, the speed reference value and the power reference value being selected along an operating trajectory in a power versus speed diagram, the operating trajectory comprising points corresponding to a nominal power and a nominal generator speed, wherein the power controller unit comprises a slider command for selecting an angular position of the operating trajectory in the power versus speed diagram.

[0008] In this context, the term "slider command" may be any command of mechanical type (e.g. a button) or electrical type (e.g. a switch) or electronic (e.g. a programmable logic circuit or block) or telegram / message via a communication network, which can be used to change the angular position of the operating trajectory in the power versus speed diagram. The slider is used to adjust the degree to which the speed reference varies as a function of power reduction.

[0009] According to a second aspect of the invention there is provided a method of controlling operations in a wind turbine, the method comprising:

[0010] operating the generator according to a speed reference and a power reference, the speed reference and the power reference being selected along an operating trajectory in a power versus speed diagram, the operating trajectory including points corresponding to a nominal power and a nominal generator speed,

[0011] Select the angular position of the operating trajectory in the power versus speed plot.

[0012] According to an embodiment of the present invention, the operation track may be linear, and the slider is used to adjust the slope of the linear track.

[0013] According to an embodiment of the present invention, the linear operating trajectory is movable between a vertical operating trajectory and an inclined operating trajectory in a power versus speed diagram, an angle is provided between the vertical operating trajectory and the inclined operating trajectory, and the value of the angle can be selected between 0° and 90° through a slider command of the power controller unit.

[0014] When the linear operating trajectory is selected as the vertical operating trajectory, a power ramp rate is generated to be applied to the generator to reach the nominal power of the generator at the nominal generator speed. When the linear operating trajectory is selected as the inclined operating trajectory, the resulting ramp rate is lower due to the need to accelerate the rotor before the power ramp. The operating point can be moved along the inclined operating trajectory to reach the nominal power of the generator at the nominal generator speed.

[0015] The invention makes it possible to select between configurations providing a fast power ramp rate (vertical operating trajectory) or a slower power ramp rate and load reduction at reduced generator speed (sloped operating trajectory).

[0016] The operating point may be moved through a plurality of inclined operating trajectories. According to one embodiment of the invention, the inclined operating trajectory is selected so as to provide a constant torque measured on the generator. According to another embodiment of the invention, the operating trajectory is selected so as to provide a maximum power of the generator at each speed reference value.

[0017] The present invention provides an improved level of flexibility in controlling a wind turbine. If a turbine is curtailed and a high ramp rate is not required, it is possible to obtain load shedding. Load shedding may be used to achieve a power upgrade of the turbine, or to extend the life, or to overpower the turbine at a later time.

[0018] The controller and control method of the present invention may be used for a single wind turbine or at a wind farm comprising a plurality of wind turbines. A fixed configuration may be used depending on the operating mode of the wind farm controller. For example, balancing control or frequency support may have one configuration with a fast ramp rate, while avoiding curtailment of excessive production may have another configuration with a slow ramp rate. The wind farm function may also assign different trade-off / slide settings to different turbines and periodically switch the slider command settings between the turbines in order to balance the load effects on the turbines.

[0019] Note that embodiments of the invention have been described with reference to different subject matters. In particular, some embodiments have been described with reference to method type claims, while other embodiments have been described with reference to device type claims. However, a person skilled in the art will appreciate from the above and following description that, unless otherwise stated, any combination of features relating to different subject matters, in particular a combination of features of a method type claim and features of a device type claim, in addition to any combination of features belonging to one type of subject matter, is part of the disclosure of this document.

[0020] The above defined aspects and further aspects of the present invention become apparent from the examples of embodiments to be described hereinafter and are explained with reference to the examples of embodiments. The present invention will be described in more detail below with reference to the examples of embodiments. However, it is expressly pointed out that the present invention is not limited to the exemplary embodiments described. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic cross-sectional view of a wind turbine including a controller according to the invention is shown.

[0022] Figure 2 The operating traces of power versus rotational speed of the control system according to the present invention are shown.

[0023] Figure 3 A schematic cross-sectional view of a wind turbine park including a controller according to the invention is shown. DETAILED DESCRIPTION

[0024] The illustration in the figures is schematically. It is noted that in different figures, similar or identical elements are provided with the same reference signs or with reference signs which differ only within the first digit.

[0025] Figure 1A wind turbine 1 according to the invention is shown. The wind turbine 1 comprises a tower 2 mounted on a foundation (not depicted). A nacelle 3 is arranged on top of the tower 2. A yaw angle adjustment device (not shown) is provided between the tower 2 and the nacelle 3, which is able to rotate the nacelle around a vertical yaw axis. The wind turbine 1 further comprises a wind rotor 5 (in the form of a rotor) having two, three or more blades 4. Figure 1 Only two blades 4 are visible in the perspective view of the wind turbine 1). The wind rotor 5 is rotatable about an axis of rotation Y. When not specified differently, the terms axial, radial and circumferential in the following text are made with reference to the axis of rotation Y. The blades 4 extend radially relative to the axis of rotation Y. Each rotor blade 4 is mounted to the wind rotor 5 so as to be pitched about a respective pitch axis (pitch axe) X. This improves the control of the wind turbine 1 and in particular the rotor blades 4 by modifying the possibility of the direction in which the wind strikes the rotor blades 4. The wind turbine 1 comprises a generator 10. The wind rotor 5 is driven by a rotatable main shaft 9 and a gearbox ( Figure 1 The main shaft 9 is provided in a manner that the main shaft 9 is held in place by the main rotor 5. ... shaft 9. The main shaft 9 is provided in a manner that the main shaft 9 is held in place by the main shaft 9. The main shaft 9 is provided in a manner that the main shaft 9 is held in place by the main shaft 9. The main shaft 9 is provided in a manner that the main shaft 9 is held in a manner that the main shaft 9 is held in place by the main shaft 9. The main shaft 9 is provided in a manner that the main shaft 9 is held in a manner that the main shaft 9 is held in place by the main shaft 9. The main shaft 9 is provided in a manner that the main shaft 9 is held in a manner that the main shaft 9 is held in place by the main shaft 9. The main shaft 9 is provided in a manner that the main shaft 9 is held in a manner that the main shaft 9 is held in a manner that the main shaft 9 is held in a manner that the main

[0026] The wind turbine 1 comprises a controller 100 (schematically shown in Figure 1 ). The controller 100 includes a power controller unit 101 and a pitch controller unit 102. The power controller unit 101 is a controller that outputs a power reference value of the generator 10 (i.e., a power value to be output by the generator 10). The pitch controller unit 102 outputs a pitch reference value (i.e., a value of a pitch angle of the blades 4 of the wind turbine 1 around the axis X). The power controller unit 101 operates the generator 10 according to the power reference values ​​212, 214. The speed reference values ​​211, 213 are defined by the power reference values ​​212, 214 along the operating trajectories 203, 204, 205 in the power versus speed diagram 200, as shown below with reference to Figure 2better illustrated. The operating trajectory 203, 204, 205 can be linear or curved (non-linear). For the linear operating trajectory 204, 205, the power controller unit 101 includes a slider command 103 for selecting the angular position of the linear operating trajectory 204, 205 in the power versus speed diagram 200. The turbine power controller unit 101 operates the generator 10 along the operating trajectory until the speed reference value 211, 213 is reached. Once the speed reference value 211, 213 is reached, a controller (e.g., a PI controller) is used to adjust the power to maintain the rotational speed at the speed reference value 211, 213. Once the power reference value 212, 214 at the speed reference value 211, 213 is reached, the pitch controller 102 is used to adjust the blade position to maintain the rotational speed at the speed reference 211, 213. When the power is lower than the power reference value 212, 214 to be achieved, the pitch controller 102 is able to control the blade position.

[0027] Figure 2 A power versus speed diagram 200 is shown, comprising a plurality of operating trajectories 203, 204, 205 implemented by the controller unit 101. In the power versus speed diagram 200, the ordinate 201 represents the power, while the abscissa 202 represents the rotational speed of the generator. The curved operating trajectory 203 is the nominal / optimal operating trajectory, where the power is a function of the speed, until it reaches a nominal speed 211. From there the power is controlled at a fixed speed, for example using a PI controller for reaching a point 210 of the nominal power 212. If the power reaches a saturation value, the speed can be controlled by the pitch controller 102. If the speed reference remains constant at the nominal speed 211, the controller unit 101 operates according to a vertical operating trajectory 204, which comprises a point 210 of the nominal power 212. The vertical operating trajectory 204 provides the fastest ramp-up time, because a high level of kinetic energy is retained in the rotor 12 of the generator 10, i.e. there is no need to accelerate the rotor 12 before the highest possible power can be reached. If the generator 10 is operated along the vertical operating trajectory 204, a first power ramp rate (c1*P) is generated every second, where P is the nominal power 212 and c1 is a constant. The first power ramp rate is applied to the generator 10 to reach the nominal power 212 of the generator 10 at the nominal generator speed 211 along the vertical operating trajectory 204. The value of c1 can be a percentage comprised between 20% and 40%. According to one embodiment of the present invention, c1 is specifically selected to be 25%.

[0028] If the reduced speed 213 is used as the reference speed, the controller unit 101 operates according to the inclined operating trajectory 205, which includes a plurality of points 220, each of which corresponds to a reduced power 214 value (i.e., a power value that is lower than the nominal power 212) and a reduced rotational speed 213 (i.e., a rotational speed value that is lower than the nominal speed 211). The inclined operating trajectory 205 includes a point 210 of the nominal power 212.

[0029] According to an embodiment of the present invention, an inclined operating trajectory 205 may be determined so as to provide a constant torque measured on the generator 10. According to other embodiments of the present invention, the inclined operating trajectory 205 may be selected so as to provide a maximum power of the generator 10 at each speed reference value 211, 213. According to still other embodiments of the present invention, the inclined operating trajectory 205 may be selected so as to avoid operating at a rotational speed corresponding to a structural characteristic value of the wind turbine 1. Along the inclined operating trajectory 205, the power ramp-up time is longer than along the vertical operating trajectory 204. If the generator 10 is operated along the inclined operating trajectory 205, the rotational speed increases as the power increases, which results in a second power ramp-up rate (c2*P) per second, where c2 is a constant lower than c1. The value of c2 may be a percentage included between 1% and 10%. According to one embodiment of the present invention, c2 is specifically selected to be 2%. The lower rotor speed also provides a reduction in load. In the power versus speed diagram 200, an angle α is provided between the vertical operating trajectory 204 and the inclined operating trajectory 205. The value of the angle α is selectable by the slider command 103 (by Figure 2 The swing (schematically represented by the dotted line in FIG. 2 ) is between 0° and 90°, 0° corresponding to the vertical operating trajectory 204, and 90° corresponding to the horizontal line in the power-to-speed diagram 200, which includes a point 210 at a nominal power 212.

[0030] According to an embodiment of the invention, the angle α may be varied during the power ramp-up. For example, the rotational speed may be ramped up first, i.e. the operating point is moved to the right in the power versus speed diagram 200, or equivalently, the value of the angle α is reduced. The power may be ramped up with a delay of a few seconds. This mode advantageously exploits the fact that the aerodynamics of the blades 4 are more efficient at higher rotor speeds. According to such an embodiment, the power may be kept constant until a speed reference is reached, after which the power may be ramped up to the power reference value.

[0031] Figure 3A wind farm 300 comprising a plurality of wind turbines 1 is shown. The wind farm 300 comprises a farm level controller 201 which is connected to the controller 100 of each turbine 1 and adjusts the operating trajectory in each turbine 1 of the wind farm 300 based on a farm level operating mode. Alternatively, the farm level controller 201 may be directly connected to each turbine 1. The operating mode may be a curtailment due to, for example, a frequency deviation or due to a trading decision.

Claims

1. A controller (100) for a wind turbine (1), the controller (100) comprising a power controller unit (101) for controlling a power output of a generator (10) included in the wind turbine (1), the power controller unit (101) operating the generator (10) in accordance with a speed reference value (211, 213) and a power reference value (212, 214), the speed reference value (211, 213) and the power reference value (212, 214) being selected along an operating trajectory (204, 205) in a power versus speed diagram (200), the operating trajectory (205) comprising points (210) corresponding to a nominal power (212) and a nominal generator speed (211), wherein the power controller unit (101) comprises a slider command (103) for selecting an angular position of the operating trajectory (204, 205) in the power versus speed diagram (200); Wherein the operation trajectory (204, 205) is linear; in, The linear operating trajectory (204, 205) is movable between a vertical operating trajectory (204) and an inclined operating trajectory (205) in a power versus speed diagram (200), providing an angle (α) between the vertical operating trajectory (204) and the inclined operating trajectory (205), and the value of the angle (α) is selectable between 0° and 90° via a slider command (103) of the power controller unit (101).

2. The controller (100) of claim 1, wherein the ramped operating trajectory (205) is selected to provide a constant torque measured on the generator (10).

3. The controller (100) of claim 1, wherein the inclined operating trajectory (205) is selected so as to avoid operation at a rotational speed corresponding to a structural characteristic value of the wind turbine (1).

4. The controller (100) of claim 1, wherein the inclined operating trajectory (205) is selected to provide a maximum power of the generator (10) at each speed reference value (211, 213).

5. A controller (100) according to any of the preceding claims, wherein the angular position of the operating trajectory (204, 205) is changed before a power reference value (212, 214) and / or a speed reference value (211, 213) is reached on a power versus speed diagram (200).

6. A wind turbine (1) comprising a generator and a controller (100) according to any one of claims 1-4.

7. A wind farm (300) comprising a plurality of wind turbines (1) and a controller (100) according to any one of claims 1-4.

8. The wind farm (300) according to claim 7, wherein: The wind farm (300) comprises a farm level controller (201) for adjusting the operating trajectory in each wind turbine (1) based on a farm level operating mode.

9. A method of controlling operations in a wind turbine, the method comprising: operating the generator (10) according to a speed reference (211, 213) and a power reference (212, 214), the speed reference (211, 213) and the power reference (212, 214) being selected along an operating trajectory (204, 205) in a power versus speed diagram (200), the operating trajectory (204, 205) comprising a point (210) corresponding to a nominal power (212) and a nominal generator speed (211), the angular position of the operating trajectory (204, 205) being selected in the power versus speed diagram (200); wherein the operation trajectory (204, 205) is linear; Wherein the linear operating trajectory (204, 205) is movable between a vertical operating trajectory (204) and an inclined operating trajectory (205) in the power versus speed diagram (200), an angle (α) is provided between the vertical operating trajectory (204) and the inclined operating trajectory (205), and the method includes selecting a value for the angle (α) between 0° and 90°.

10. The method of claim 9, wherein the inclined operating trajectory (205) is selected so as to provide a constant torque measured on the generator (10).

11. The method according to claim 9, wherein the inclined operating trajectory (205) is selected in order to avoid operation at a rotational speed corresponding to a structural characteristic value of the wind turbine (1).

12. The method of claim 9, wherein the inclined operating trajectory (205) is selected to provide a maximum power of the generator (10) at each speed reference value (211, 213).

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