Wind turbine ice protection

Abstract

A pitch controlled wind turbine has a tower, a nacelle mounted on the tower, a hub rotatably mounted on the nacelle, and at least three blades. The wind turbine comprises at least three blade connection members, each extending between adjacent blades. The wind turbine has at least three pretension members, each connected to one of the blade connection members and connected to the hub via a tensioning device providing radial movement of the pretension member as a result of extension / retraction of the tensioning device, each pretension member thereby providing pretension in its connected blade connection member. A de-icing system is coupled to one or more of the tensioning devices and configured to control extension or retraction of the one or more tensioning devices in order to energize at least some of the wind turbine blades, blade connection members and / or pretension members in order to remove ice therefrom.

Description

Technical Field

[0001] This invention relates to a pitch-controlled wind turbine with a de-icing system. Background Technology

[0002] Wind turbines are typically deployed in areas with low temperatures and severe weather conditions, which causes ice to form on various components of the turbine structure.

[0003] Ice buildup on wind turbine components presents several significant challenges. First, it increases the overall weight of the turbine, potentially leading to imbalances and mechanical stresses on critical components, as well as aerodynamic effects that can result in reduced efficiency and costly maintenance. Furthermore, ice buildup can cause structural damage, impacting the wind turbine's lifespan. This is particularly problematic in pitch-controlled wind turbines with blade load-sharing connection members, which include various additional components designed to support larger blades. These components are prone to icing, and if left unmitigated, can degrade the wind turbine's performance and structural integrity.

[0004] Therefore, de-icing systems designed to remove accumulated ice are important for ensuring the reliable and continuous operation of wind turbines in cold climates. Summary of the Invention

[0005] A first aspect of the invention provides a pitch-controlled wind turbine, comprising a tower, a nacelle mounted on the tower, a hub rotatably mounted on the nacelle, and at least three wind turbine blades, wherein each wind turbine blade extends between a root end and a tip end connected to the hub via a pitch mechanism; the wind turbine further comprises at least three blade connection members, each blade connection member extending from a connection point on one wind turbine blade toward a connection point on an adjacent wind turbine blade, wherein the connection point on a given wind turbine blade is arranged at a distance from the root end of the wind turbine blade and... The components include: at least three pretensioning members, each connected to one of the blade connecting members and connected to the hub via a tensioning device, the tensioning device providing radial movement of the radially inner end of the pretensioning member relative to the axis of rotation of the hub due to the extension or retraction of the tensioning device, thereby providing pretension in the blade connecting member to which each pretensioning member is connected; and a de-icing system coupled to one or more tensioning devices and configured to control the extension or retraction of the one or more tensioning devices to excite at least some of the wind turbine blades, blade connecting members and / or pretensioning members to remove ice from them.

[0006] It should be understood that, in this context, the term "excitation" refers to the initiation or generation of vibration in the corresponding component.

[0007] Providing a de-icing system can protect the essential components of pitch-controlled wind turbines with blade load-sharing connection members from ice buildup. It should be understood that the term "ice" as used herein refers to frozen water, including, for example, ice, snow, sleet, hail, slush, etc. Reducing or removing ice buildup on such components helps avoid problems such as increased mechanical stress, reduced power generation efficiency, potential damage from ice spillage, and increased downtime and maintenance.

[0008] Controlling tensioning devices to remove ice from wind turbine blades, blade connecting members, and / or pre-tensioning members utilizes pre-existing equipment to mitigate the negative effects of icing, providing a simple means of minimizing the impact of ice accumulation. In some arrangements, the use of pre-existing equipment enables retrofitting of existing arrangements through simple updates, such as software updates to the control system.

[0009] The de-icing system can be configured to control one or more tensioning devices to move in a substantially step manner between an extended state and a retracted state in order to change the tension in the corresponding pre-tensioned member in a substantially step manner.

[0010] A substantially abrupt change in tension within a pretensioning member can cause sudden oscillations or vibrations in the pretensioning member, one or more blade connection members attached thereto, and one or more wind turbine blades. These sudden vibrations can help remove ice from the corresponding wind turbine blades and / or blade connection members and / or pretensioning members.

[0011] The term "essentially step" refers to the limitations of the equipment in achieving completely instantaneous changes in the state of the tensioning device. It should be understood that changes in the state of the tensioning device are intended to be as instantaneous as the equipment allows.

[0012] The de-icing system can be configured to control one or more tensioning devices to apply tension to a corresponding pre-tensioned member. The tension can be at least 80% of the maximum tension that the tensioning device can produce, preferably between 80% and 90% of the maximum tension that the tensioning device can produce.

[0013] It has been found that increasing the tension in the pretensioning member before releasing the tension when moving to the retracted state increases sudden oscillations or vibrations in the corresponding pretensioner, thereby further aiding in the removal of ice from the corresponding wind turbine blades and / or blade connecting members and / or pretensioning members.

[0014] The de-icing system can be configured to control one or more tensioning devices to extend and retract cyclically in order to generate oscillations in at least some of the wind turbine blades, blade connecting members, and / or pre-tensioning members.

[0015] Oscillations generated in wind turbine blades, blade connecting components, and pretensioning components provide continuous motion on surfaces where ice may be present, thereby increasing the removal of ice from those surfaces.

[0016] Preferably, the frequency of the oscillation is the same as or similar to the natural frequency (or characteristic frequency) of the blade (depending on the blade pitch) in the edge direction or the front-back direction.

[0017] The de-icing system can be configured to control at least two tensioning devices to extend and retract synchronously or in a phase relationship.

[0018] The cyclic extension and retraction of the two tensioning devices allow oscillations to be applied to multiple pre-tensioned members, and thus to multiple blade connection members and multiple wind turbine blades.

[0019] Using phase relationships helps to target oscillations to specific wind turbine blades (i.e., blades between two corresponding pretensioned members), increasing blade motion and thus increasing ice removal from the blades.

[0020] The de-icing system can be configured to control the first and second tensioning devices to extend and retract synchronously in a cyclic manner, and to control the third tensioning device to extend and retract in a cyclic manner out of phase with the first and second tensioning devices.

[0021] This arrangement can simultaneously stimulate multiple wind turbine blades, further increasing ice removal and improving the efficiency of the de-icing system.

[0022] The de-icing system can be configured to control one or more tensioning devices to extend and retract cyclically in order to generate oscillations in the flapping or edge directions in at least some of the wind turbine blades.

[0023] The direction of oscillation on wind turbine blades can be adjusted based on the position of ice on the corresponding blade surface, thereby further improving the efficiency of the de-icing system.

[0024] The de-icing system can be configured to control one or more tensioning devices to cyclically extend and retract at a frequency substantially equal to the natural frequency of the corresponding wind turbine blade, blade connection member, or pre-tensioning member.

[0025] It has been found that operating at such a frequency can increase the excitation in the flapping or edge direction of the corresponding wind turbine blades. In this way, a higher level of de-icing can be achieved, and less energy is required to induce vibration.

[0026] The de-icing system can be coupled to the pitch mechanism and can be configured to control the pitch mechanism to cyclically change the pitch of the corresponding wind turbine blades in order to remove ice from the wind turbine blades.

[0027] In this way, the de-icing system utilizes pre-existing mechanisms to further aid in de-icing. It has been found that utilizing pitch variations while simultaneously exciting the wind turbine blades can further improve de-icing on them. Furthermore, the pitch of the wind turbine blades can be adjusted to maximize the impact of the excitation. This arrangement is particularly advantageous when the rotor is stationary (e.g., because changing the pitch would affect the blade rotational speed if the turbine is running).

[0028] The de-icing system can be coupled to the pitch mechanism and configured to control the pitch mechanism to change the pitch of the corresponding wind turbine blades, so that the wind turbine blades are essentially stalled.

[0029] It has been found that this arrangement increases the level of excitation in wind turbine blades. This is particularly advantageous when oscillations in the edge direction are generated in wind turbine blades.

[0030] Furthermore, in a preferred embodiment, the blade connecting members and / or pretensioning members can be configured to provide damping, which reduces the level of oscillations acting on the rotor in the lateral direction. Therefore, the risk of rotor damage is significantly reduced compared to the rotor of a standard wind turbine (i.e., without blade connecting members and / or pretensioning members). In this way, large oscillations in the lateral direction can be generated in the wind turbine blades without posing a significant risk of rotor damage.

[0031] The de-icing system may include one or more electric heating elements and / or a fluid heating system.

[0032] It has been found that providing such heating elements and / or systems can further improve the efficiency of de-icing systems, because if the ice is at least partially melted, it can be more easily removed from the corresponding wind turbine components in response to the excitation.

[0033] Electric heating elements provide precise and controlled temperature rise to melt ice. They can generate heat quickly and efficiently, rapidly melting ice and restoring the function of wind turbine components. Fluid heating systems are an effective means of providing heat to melt ice.

[0034] Each tensioning device may include an actuator having a first portion coupled to a hub and a second portion movable relative to the first portion and coupled to a corresponding pre-tensioning member, wherein the tensioning device is configured to extend and retract by movement of the second portion relative to the first portion.

[0035] The actuator provides an easily controlled means of actuating at least some of the wind turbine blades, blade connection components, and pretensioning components.

[0036] The actuator can be a linear actuator, such as a hydraulic actuator, an electric actuator, or a mechanical actuator. The actuator can have a cylinder and a rod that can be moved into and out of the cylinder. A first part of the actuator may include the cylinder, and a second part of the actuator may include the rod.

[0037] The actuator may be a rotary actuator. The actuator may include a motor and a tensioning element, wherein the radially distal end of the tensioning element is connected to the radially inner end of a pre-tensioned member, and the radially inner end of the tensioning element is wound around a drum connected to a rotatable shaft of the motor. A first portion of the actuator may include a motor, and a second portion of the actuator may include the tensioning element.

[0038] The de-icing system may include one or more sensors in or on one or more of the blade connecting members or pretensioning members for detecting ice accumulation.

[0039] Providing sensors can improve control of the de-icing system and provide operators with up-to-date information on the presence of ice. The energy requirements of the de-icing system can be reduced because the system operates only when needed (e.g., when a predetermined amount of ice has accumulated, or when weather conditions indicate that ice has accumulated), rather than continuously.

[0040] Blade connection components enable wind turbine blades to support each other. The significance of this is that the load on the wind turbine blades, especially the load in the edge direction and to some extent the load in the flapping direction, is "shared" between the wind turbine blades.

[0041] The connection point on the wind turbine blade can be arranged at a distance from the root end between 10% and 60% of the length of the wind turbine blade from the root end to the tip end, preferably at 50% of the radial inner side of the corresponding wind turbine blade length from the root end, and more preferably at 45% of the radial inner side of the corresponding wind turbine blade length from the root end.

[0042] Connection points on wind turbine blades can be located at positions where the thickness-chord ratio of the wind turbine blade is between 20% and 50%.

[0043] Each wind turbine blade may include an inner portion containing the root end and an outer portion containing the tip end. The inner and outer portions may be connected to each other at a separated position. The inner portion may be connected to the outer portion via a connector. The connector may include a connector.

[0044] Connectors can be metal components, preferably cast or machined. Connectors can be composite components. Connectors can be co-cured or co-bonded components. Providing such connectors improves the ease of manufacturing and provides lightweight, high-strength connectors.

[0045] A connector can be coupled to transfer load between the spar cap portion of the inner section of the blade and the spar cap portion of the outer section of the blade. The connector can be arranged to transfer the load from the blade connecting member to the spar cap portion of the inner section of the blade. This can improve the load transfer efficiency of the turbine blade because the spar cap portion can be designed to withstand higher loads than the blade casing. The connector may include connection points for the blade connecting member.

[0046] Each wind turbine blade may include a leading edge, a leading edge extension, and a blade shell, wherein the leading edge extension extends in front of the leading edge, and the connection point of the corresponding wind turbine blade is located on the leading edge extension in front of the leading edge, and each wind turbine blade also includes a corresponding fairing extending at least on the leading edge extension.

[0047] The leading edge extension can be integrally formed with the connector. The fairing can cover the connection joint. The fairing can be secured to the connector. The connector can extend beyond the profile of the blade housing at the connection joint. This can improve load transfer across the connection joint, but may require a larger fairing.

[0048] Each wind turbine blade can be coupled to two blade connection members. Each of these two blade connection members extends from a corresponding connection point of a blade. The connection points of a wind turbine blade can be adjacent to each other on the same leading edge extension. Each blade connection member can move independently at its respective first and second connection points. The connection points may include bearing structures.

[0049] Wind turbines can be upwind wind turbines.

[0050] A second aspect of the invention provides a method for de-icing a pitch-controlled wind turbine, the pitch-controlled wind turbine comprising: a tower, a nacelle mounted on the tower, a hub rotatably mounted on the nacelle, and at least three wind turbine blades, wherein each wind turbine blade extends between a tip end and a root end connected to the hub via a pitch mechanism; at least three blade connection members, each blade connection member extending from a connection point on one wind turbine blade toward a connection point on an adjacent wind turbine blade, wherein the connection points on a given wind turbine blade are arranged in relation to the wind turbine blade... The blades have root ends spaced apart and tip ends spaced apart; and at least three pretensioning members, each pretensioning member connected to one of the blade connecting members and connected to the hub via a tensioning device, the tensioning device providing radial movement of the radially inner end of the pretensioning member relative to the axis of rotation of the hub due to the extension or retraction of the tensioning device, thereby providing pretension in the blade connecting member to which each pretensioning member is connected; the method includes controlling one or more tensioning devices to extend or retract in order to excite at least some of the wind turbine blades, blade connecting members and / or pretensioning members to remove ice from them.

[0051] The method may include controlling one or more tensioning devices to move in a substantially step manner between an extended state and a retracted state in order to change the tension in the respective pre-tensioned member in a substantially step manner.

[0052] The method may include controlling one or more tensioning devices to apply tension to a corresponding pre-tensioned member. The tension may be at least 80% of the maximum tension that the tensioning device is capable of producing, preferably between 80% and 90% of the maximum tension that the tensioning device is capable of producing.

[0053] The method may include controlling one or more tensioning devices to cyclically extend and retract in order to generate oscillations in at least some of the wind turbine blades, blade connecting members, and / or pretensioning members.

[0054] The method may include controlling at least two tensioning devices to extend and retract synchronously or in a phase relationship in a cyclical manner.

[0055] The method may include controlling the first and second tensioning devices to extend and retract synchronously in a cyclic manner, and controlling the third tensioning device to extend and retract in a cyclic manner out of phase with the first and second tensioning devices.

[0056] The method may include controlling one or more tensioning devices to cyclically extend and retract in order to generate oscillations in the flapping or edge directions in at least some of the wind turbine blades.

[0057] The method may include controlling one or more tensioning devices to cyclically extend and retract at a frequency substantially equal to the natural frequency of the respective wind turbine blade, pretensioning member, or blade connection member.

[0058] The method may include controlling a pitch mechanism to cyclically change the pitch of the corresponding wind turbine blades in order to remove ice from the corresponding wind turbine blades.

[0059] The method may include controlling a pitch mechanism to change the pitch of the corresponding wind turbine blades, so that the wind turbine blades are in a substantially stalled state.

[0060] The pitch-controlled wind turbine may include one or more electric heating elements and / or fluid heating systems, and the method may further include controlling the one or more electric heating elements and / or fluid heating systems to de-ice the pitch-controlled wind turbine.

[0061] Pitch-controlled wind turbines may include a de-icing system comprising one or more electrically heated elements and / or fluid heating systems. In this case, the method may further include the steps of: detecting ice accumulated on at least a portion of the wind turbine blades, blade connecting members, and / or pretensioning members; and activating the one or more electrically heated elements and / or fluid heating systems to weaken the connection between the ice and the at least a portion of the wind turbine blades, blade connecting members, and / or pretensioning members. The one or more tensioning devices are then controlled to extend or retract to excite at least some of the wind turbine blades, for example, by one or more methods described below, to release at least a portion of the accumulated ice from the wind turbine blades, blade connecting members, and / or pretensioning members. This method has been found particularly advantageous because using tensioning devices to shake ice off the wind turbine as soon as the connection between the ice and the wind turbine is weakened by heating, rather than waiting for the ice to completely melt, saves significant time and allows for a substantial increase in power generation time under icing conditions.

[0062] A pitch-controlled wind turbine may include one or more sensors, located in or above one or more of the blade connection members or pretensioning members, for detecting ice accumulation, and the method may include controlling the extension or retraction of the one or more tensioning devices in response to signals from the one or more sensors.

[0063] A third aspect of the invention provides a tensioning device for de-icing a pitch-controlled wind turbine. The pitch-controlled wind turbine includes a tower, a nacelle mounted on the tower, a hub rotatably mounted on the nacelle, and at least three wind turbine blades, wherein each wind turbine blade extends between its tip and its root end, which is connected to the hub via a pitch control mechanism. The wind turbine further includes: at least three blade connection members, each blade connection member extending from a connection point on one wind turbine blade toward a connection point on an adjacent wind turbine blade, wherein the connection point on a given wind turbine blade is arranged at a distance from the root end and a distance from the tip end of the wind turbine blade; at least three pretensioning members, each pretensioning member connected to one of the blade connection members and connected to the hub via a tensioning device, wherein the tensioning device provides radial movement of the radially inner end of the pretensioning member relative to the axis of rotation of the hub due to the extension or retraction of the tensioning device, thereby providing pretension in the blade connection member to which each pretensioning member is connected; and a de-icing system coupled to one or more tensioning devices and configured to control the extension or retraction of the one or more tensioning devices to excite at least some of the wind turbine blades, blade connection members and / or pretensioning members to remove ice therefrom. The concept of using a tensioning device in a pitch-controlled wind turbine with blade connecting members to shake off ice allows for the omission of electric heating elements and / or fluid heating systems, thus simplifying the construction of this particular type of wind turbine.

[0064] While the simpler design of pitch-controlled wind turbines with blade connecting members, lacking electric heating elements and / or fluid heating systems, has advantages, in some cases, pitch-controlled wind turbines with blade connecting members can be equipped with electric heating elements and / or fluid heating systems. In such cases, de-icing of pitch-controlled wind turbines using tensioning devices can be particularly effective because ice can be removed from the wind turbine more quickly by forcibly agitating a portion of the wind turbine using one or more tensioning devices, for example by one or more methods described below, to release at least a portion of the ice from the wind turbine blades, blade connecting members, and / or pre-tensioning members without completely melting the ice. Attached Figure Description

[0065] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 A front view of a wind turbine based on the first example is shown; Figure 2 A side view of a wind turbine is shown; Figure 3 A partial side view of the de-icing system components near the hub of a wind turbine is shown; Figure 4A schematic diagram of a de-icing system based on an example is shown; Figure 5A A schematic diagram of a blade connection member or pretensioning member according to the first example is shown; Figure 5B A schematic diagram of a blade connection member or pretensioning member according to the second example is shown; Figure 6 The image shows a wind turbine blade; Figure 7 An exploded view of the connection joint is shown; Figure 8 The turbine blades with fairings are shown; Figures 9A to 9D An example of a wind turbine controlled by a de-icing system is shown. Detailed Implementation

[0066] In this specification, terms such as leading edge, trailing edge, pressure surface, suction surface, thickness, and chord length are used. Although these terms are well known and readily understood by those skilled in the art, definitions are provided below to avoid ambiguity.

[0067] The term leading edge is used to refer to the blade edge that will be located at the front of the blade when the blade rotates in the normal direction of rotation of the wind turbine rotor.

[0068] The term trailing edge is used to refer to the edge of a wind turbine blade that is located at the rear of the blade when the blade rotates in the normal direction of rotation of the wind turbine rotor.

[0069] The chord length of a blade is the straight-line distance from the leading edge to the trailing edge in a given cross section perpendicular to the blade's span. The term chord direction is used to refer to the direction from the leading edge to the trailing edge or vice versa.

[0070] The pressure surface (or windward surface) of a wind turbine blade is the surface between the leading and trailing edges. When the blade is in use, the pressure on the pressure surface is higher than that on the suction surface of the blade.

[0071] The suction side (or lee side) of a wind turbine blade is the surface between the leading and trailing edges. When the blade is in use, the pressure acting on the suction side will be lower than the pressure on the pressure side.

[0072] The thickness of a wind turbine blade is measured perpendicular to the blade chord length and is the maximum distance between the pressure and suction surfaces in a given cross section perpendicular to the blade span direction.

[0073] The term spanwise refers to the direction from the root tip to the tip tip of a wind turbine blade, or vice versa. When wind turbine blades are mounted on a wind turbine hub, the spanwise and radial directions will be essentially the same.

[0074] The term "outer side" refers to the radial direction from the blade hub towards the blade tip. The term "inner side" refers to the radial direction from the blade tip towards the hub.

[0075] A view perpendicular to both the spanwise and chordwise directions is called a planar shape view. This view is taken along the thickness dimension of the blade.

[0076] The term web or shear web is used to refer to the longitudinally, generally spanwise, reinforcing member of a blade that can transfer the load from one side of the windward and leeward sides of the blade to the other side.

[0077] Figure 1 and Figure 2 A pitch-controlled wind turbine 1 according to a first example is shown. Figure 1 This is the front view of wind turbine 1, and Figure 2 This is a side view of a wind turbine 1. The wind turbine 1 includes a tower 2 and a nacelle 3 mounted on the tower 2. A hub 4 is rotatably mounted on the nacelle 3 and carries three wind turbine blades 5 projecting outward from the nacelle 3. Although Figure 1 and Figure 2 The example wind turbine 1 shown has three blades 5a, 5b, and 5c, but it should be understood that other numbers of blades 5 are also possible. When wind blows towards the wind turbine 1, the wind turbine blades 5 generate lift, which causes a generator (not shown) inside the nacelle 3 to generate electricity.

[0078] It should be understood that the wind turbine 1 depicted can be any suitable type of wind turbine 1. The wind turbine 1 shown is an upwind wind turbine, but it should be understood that the wind turbine 1 can be a downwind wind turbine. The wind turbine 1 can be an onshore wind turbine, such that the foundation is embedded in the ground, or the wind turbine 1 can be offshore installed, in which case the foundation will be provided by a suitable offshore platform.

[0079] Blade connection members 6 interconnect adjacent wind turbine blades 5 between connection points 7a, 7b on the wind turbine blades 5. In the illustrated arrangement, three blade connection members 6a, 6b, 6c are provided (i.e., one blade connection member per blade 5). The connection members 6 are cables, such as metal (e.g., steel) or polymer (e.g., including ultra-high molecular weight polyethylene - UHMWPE) cables. In some examples, each wind turbine blade 5 is coupled to two blade connection members 6. Every two blade connection members 6 extend from a corresponding connection point 7a, 7b on one of the blades 5. Each blade connection member 6 can move independently at its corresponding first and second connection points 7a, 7b to which it is attached. Connection points 7a, 7b may include bearing structures.

[0080] The pretensioning members 8 are arranged from each of the blade connecting members 6 at a common point 25 at or near the hub 4 (see Figure 3 (Extended.) Figure 1 and Figure 2 In the example shown, the pretensioning member 8 extends to the hub 4. The pretensioning member 8 is configured to provide pretension in the blade connection member 6. The pretensioning member 8 is typically a cable, such as a metal or polymer cable. In the arrangement shown, three pretensioning members 8a, 8b, and 8c are provided (i.e., one pretensioning member per blade 5).

[0081] The pretensioned member 8 is coupled to the hub 4 via a corresponding tensioning device 9. Each tensioning device 9 provides radial inner end of the pretensioned member 8 relative to the axis of rotation 10 of the hub (see [link to tensioning device 9]) due to the extension or retraction of the tensioning device 9. Figure 3 The radial movement of the pretensioning member 8. Each pretensioning member 8 thus provides pretension in the blade connecting member 6 to which it is connected. In the figures, three tensioning devices 9a, 9b, 9c are provided (i.e., one tensioning device for each pretensioning member 8).

[0082] The wind turbine blade 5 has a root end 11 near the hub 4, the root end 11 being adapted to pass through the pitch mechanism 50 (see...). Figure 3 The blade 5 is connected to the hub 4 and has a tip 12 away from the hub 4. The blade 5 includes a leading edge 13 and a trailing edge 14 extending between the respective root end 11 and tip 12. Each blade 5 includes a suction side 15 and a pressure side 16 (see Figure 5). The thickness dimension of the blade 5 extends between the suction side 15 and the pressure side 16.

[0083] Connection points 7a and 7b are located between the root end 11 and the tip end 12 of the respective blade 5 (i.e., at a distance from the root end 11 and at a distance from the tip end 12). Connection points 7a and 7b can be located between 10% and 60% of the radial length of the wind turbine blade 5 from the root end 11 to the tip end 12, but preferably radially inward at 50% of the radial length of the wind turbine blade 5 from the root end 11 to the tip end 12, more preferably radially inward at 45% of the radial length of the wind turbine blade 5 from the root end 11 to the tip end 12, for example, approximately 30-40%. It should be understood that connection points 7a and 7b can be adjacent to each other. Alternatively, connection points 7a and 7b can be spaced apart from each other.

[0084] The wind turbine 1 includes a de-icing system 17. The de-icing system 17 is configured to protect one or more of the blade connection members 6, pretensioning members 8, or wind turbine blades 5 from ice accumulation. The de-icing system 17 can be configured to remove or reduce ice accumulation on a given component of the wind turbine 1. It should be understood that the term "ice" as used herein refers to frozen water, including, for example, ice, snow, sleet, hail, slush, etc.

[0085] Providing a de-icing system can protect the fundamental components of pitch-controlled wind turbines with blade load-sharing connections from ice buildup. Reducing or removing ice buildup on such components helps avoid problems such as increased mechanical stress, reduced power generation efficiency, and increased downtime and maintenance.

[0086] The de-icing system 17 is coupled to one or more tensioning devices 9. Figure 3 Only one tensioning device 9 is indicated in the text, but it should be understood that in some arrangements, the de-icing system 17 may be coupled to multiple tensioning devices 9a, 9b, 9c. The de-icing system 17 is configured to control one or more tensioning devices 9 to extend or retract in order to excite at least some of the wind turbine blades 5, blade connection members 6, and / or pre-tensioning members 8. Excitation of any of these components can cause any ice accumulated on it to be removed from it (i.e., in response to motion induced at the surface, ice is thrown or falls from the corresponding surface), thereby reducing the presence of ice on the surface of the component.

[0087] The de-icing system 17 may be in the form of a control system that can send signals to the corresponding tensioning device 9 to instruct the tensioning device 9 to extend and / or retract in order to excite the corresponding wind turbine 1 component. The extension and / or retraction of the tensioning device 9 can induce movement in the corresponding pre-tensioning member 8, which in turn can induce movement (e.g., induce excitation) in one or more corresponding blade connection members 6 and one or more wind turbine blades 5.

[0088] refer to Figure 3 The image generally illustrates the hub 4 of a wind turbine. The hub 4 may include a hub member 57 extending substantially from the hub along a direction defined by the hub's axis of rotation 10. A pretensioning member 8 may be connected to the hub member 57. It can be seen that a tensioning device 9 is connected at its radially inner end to or toward a common area or common point 25. The common point 25 may provide a pivotal connection for each tensioning device 18. Figure 3 In this configuration, the common point 25 is located on a protrusion 37 extending in the upwind direction of the wind turbine 1 in front of the hub 4. The protrusion 37 may be a frame or structure rigidly coupled to the hub 4. A fairing 29 may be coupled to the hub to cover the radially inner portion of each tensioning device 9. The fairing 29 may shield the common point 25. In this way, the fairing 29 can be considered an important component providing protection for the radially inner portion of each tensioning device 9.

[0089] The tensioning device 9 may include an actuator 51 having a first portion 53 coupled to the hub 4 and a second portion 54 movable relative to the first portion 53 and coupled to a corresponding pretensioning member 8. The tensioning device 9 extends and retracts by the movement of the second portion 54 relative to the first portion 53. The extension and retraction of the tensioning device 9 changes the tension in the pretensioning member 8. In this arrangement, the de-icing system 17 may be coupled to the actuator 51 to control the movement of the second portion 54 relative to the first portion 53, thereby inducing movement in the corresponding pretensioning member 8.

[0090] Actuator 51 may be a linear actuator having a cylinder and a rod that can move into and out of the cylinder. Actuator 51 may be, for example, hydraulic or electromechanical. The cylinder may be a first part 53, and the rod may be a second part 54.

[0091] Actuator 51 may be a rotary actuator. Although not shown, actuator 51 may include a motor and a tensioning element, wherein the radially distal end of the tensioning element is connected to the radially inner end of the pre-tensioned member 8, and the radially inner end of the tensioning element is wound around a drum connected to a rotatable shaft of the motor. A first portion 53 of actuator 51 may include a motor, and a second portion 54 of actuator 51 may include the tensioning element.

[0092] It should be understood that the tensioning device 9 can be any suitable form to induce excitation in at least some of the wind turbine blades 5, blade connecting members 6 and pretensioning members 6.

[0093] De-icing system 17 Figure 3 The diagram is schematically shown and can be configured to control one or more tensioning devices 9 to induce excitation and de-icing in a target area of ​​the wind turbine 1, or to increase the excitation effect in de-icing.

[0094] The de-icing system 17 can be configured to control one or more tensioning devices 9 to move between an extended state and a retracted state. In the retracted state, the tensioning device 9 can apply tension to the corresponding pre-tensioned member 8. In the extended state, the tensioning device can release or reduce the tension in the pre-tensioned member 8.

[0095] The de-icing system 17 can be configured to control one or more tensioning devices 9 to move in a substantially stepwise manner between an extended state and a retracted state, thereby changing the tension in the corresponding pre-tensioned member 8 in a substantially stepwise manner. In other words, the de-icing system 17 can control one or more tensioning devices 9 to retract to create tension in the corresponding pre-tensioned member 8, and then extend the tensioning device 9 to cause a sudden release or reduction of tension. Controlling the tensioning devices 9 in this manner may be preferred when the wind turbine is idling (i.e., when the blades 5 are not rotating and the wind turbine 1 is not generating electricity). This reduces the area from which ice is ejected from the blades 5.

[0096] The term "essentially step" refers to the limitations of the device in achieving completely instantaneous changes in the state of the tensioning device. It should be understood that the changes in the state of the tensioning device are intended to be as instantaneous as the device allows (e.g., via actuator 51).

[0097] In some arrangements, the de-icing system 17 can be configured to control one or more tensioning devices 9 to extend or retract until the tensioning device 9 reaches its mechanical limit or endpoint. Upon reaching such a limit, the tensioning device 9 can no longer extend or retract and thus will abruptly decelerate and stop. In this way, a sudden change in tension is induced in the corresponding pre-tensioning member 8. Utilizing the mechanical limit of the tensioning device 9 allows for more abrupt tension changes in the corresponding pre-tensioning member 8 (e.g., compared to a motor or hydraulic system that implements abrupt changes in tensioning device 9), thereby improving de-icing of the wind turbine 1.

[0098] A step change in the tensioning device 9 between its extended and retracted states causes a sudden oscillation or vibration in the pre-tensioning member 8 connected to the tensioning device 9. This can further induce such vibration in one or more blade connecting members 6 connected to the pre-tensioning member 8, and consequently in the blades 5 connected to each blade connecting member 6. For example, refer to Figure 1 The essentially abrupt change in tensioning device 9a from its extended to its retracted state can cause sudden oscillations in pretensioning member 8a, which in turn cause sudden oscillations in blade connecting member 6a. This can then lead to sudden oscillations in at least wind turbine blades 5a and 5b (i.e., either end of the corresponding blade connecting member 6a). The sudden movements in blades 5a and 5b, pretensioning member 8a, and / or blade connecting member 6a can help remove ice from the surfaces of the various components.

[0099] In the example arrangement, the de-icing system 17 can be configured to control multiple or all of the tensioning devices 9 (e.g., in...). Figure 1 In this arrangement, all three devices (9a, 9b, and 9c) can simultaneously move between extended and retracted states in a substantially stepwise manner. This can simultaneously induce sudden oscillations or vibrations in multiple pre-tensioned members 8a, 8b, 8c, blade connecting members 6a, 6b, 6c, and wind turbine blades 5a, 5b, 5c, thereby increasing de-icing from multiple components of the wind turbine 1. The substantially stepwise change from the extended to the retracted state can be repeated as needed, for example, by repeatedly inducing sudden oscillations or vibrations in the corresponding wind turbine 1 components until sufficient de-icing occurs.

[0100] The de-icing system 17 can be configured to control one or more tensioning devices 9 to cyclically extend and retract, thereby generating oscillations in at least some of the wind turbine blades 5, blade connecting members 6, and / or pre-tensioning members 8. In this way, the repeated extension and retraction of the tensioning devices 9 results in repetitive oscillations or vibrations in the pre-tensioning members 8 connected to the tensioning devices 9, and consequently in the corresponding blade connecting members 6 and wind turbine blades 5. The continuous movement on the surfaces of the pre-tensioning members 8 and / or blade connecting members 6 and / or wind turbine blades 5 can lead to effective removal of ice from said surfaces. Controlling the tensioning devices 9 in this manner may be preferred when the wind turbine is stopped or idling (i.e., when the blades 5 are not rotating or are rotating very slowly).

[0101] The de-icing system 17 can be configured to control at least two tensioning devices 9 to cyclically extend and retract, thereby generating oscillations in multiple pre-tensioned members 8. This can promote oscillations in multiple blade connection members 6 and multiple wind turbine blades 5, thereby increasing the removal (or shedding) of ice from the wind turbine 1.

[0102] The de-icing system 17 can be configured to control at least two tensioning devices 9 to extend and retract synchronously or in a phase relationship. Controlling the synchronous extension and retraction of the tensioning devices 9 results in two or more tensioning devices 9 being simultaneously extended and simultaneously retracted. In this way, the pre-tensioning members 8 connected to each tensioning device 9 can oscillate synchronously with each other. Synchronization operation may include the tensioning devices 9 applying and releasing the same tension (i.e., the same force) to the pre-tensioning members 8 in their respective extended and retracted states. In some arrangements, different tensions may be applied to different pre-tensioning members 8.

[0103] Controlling the extension and retraction of tensioning devices 9 in a phase relationship causes two or more tensioning devices to oscillate asynchronously with each other. In some arrangements, the phase relationship may include one tensioning device 9 being extended while another tensioning device 9 is retracted, resulting in asynchronous oscillations in the corresponding pretensioning members 8 with a phase shift of approximately 180°. It should be understood that in some arrangements, the pretensioning members 8 may operate with any phase shift, such as less than 180°.

[0104] Controlling the tensioning device to extend and retract cyclically in a phase relationship can enhance the de-icing system's ability to more effectively de-ic specific wind turbine blades. For example, refer to... Figure 1The de-icing system can control the tensioning devices 9a and 9c (i.e., either side of blade 5a) to cyclically extend and retract in a phase relationship. In some arrangements, tensioning device 9a can be extended when tensioning device 9c is retracted, and vice versa, causing pretensioning members 8a and 8b to oscillate asynchronously to define a phase shift of approximately 180°. This will generate similar phase oscillations in blade connecting members 6a and 6c, which will therefore cause blade 5 to be cyclically pulled and released by blade connecting members 6a and 6c on either side. In this way, oscillations can be generated primarily in the targeted wind turbine blade 5a, rather than in other wind turbine blades 5. In this arrangement, tensioning device 9b can be inactive, meaning that no oscillations are generated directly in pretensioning member 8b or blade connecting member 6b (although it should be understood that residual oscillations will occur due to the interconnection of blade connecting members 6a, 6b, and 6c).

[0105] Once sufficient ice has been removed from blade 5a, or once oscillation has occurred for a predetermined amount of time, the de-icing system 17 can be configured to repeat the process for other blades. For example, tensioning devices 9a and 9b can be controlled to extend and retract cyclically in a phase relationship to generate oscillations on blade connecting members 6a and 6b and on blade 5b. Tensioning devices 9b and 9c can be controlled to extend and retract cyclically in a phase relationship to generate oscillations on blade connecting members 6b and 6c and on blade 5c.

[0106] The de-icing system 17 can be configured to control the cyclic extension and retraction of all tensioning devices 9. In some arrangements, the de-icing system 17 is configured to control two tensioning devices 9 to cyclically extend and retract synchronously, and to control another tensioning device 9 to cyclically extend and retract out of phase with the two synchronous tensioning devices 9. This arrangement helps to simultaneously excite multiple wind turbine blades 5, improving the efficiency of the de-icing system 17.

[0107] In the example layout, refer to Figure 1 The de-icing system 17 can be configured to control the tensioning devices 9a and 9b to extend and retract synchronously with each other, and to control the tensioning device 9c to extend and retract synchronously with respect to the tensioning devices 9a and 9b in a phase relationship (i.e., asynchronously). This arrangement can cause the pre-tensioning members 8a and 8b to oscillate synchronously with each other, while the pre-tensioning member 8c oscillates synchronously with respect to the pre-tensioning members 8a and 8b. This configuration has been found to induce oscillations in wind turbine blades 5a and 5c, resulting in targeted de-icing of multiple blades 5. In some arrangements, the de-icing system 17 controls the tensioning device 9 such that the pre-tensioning member 8c is asynchronous with the pre-tensioning members 8a and 8b, with a phase shift of approximately 180°. It should be understood that in some arrangements, the pre-tensioning member 8 can operate with any phase shift, for example, less than 180°.

[0108] In some arrangements, the tension generated by the tensioning device 9 in the corresponding pre-tensioning member 8 (i.e., in the extended state) can be the maximum tension that the tensioning device 9 can generate and / or the maximum tension that the pre-tensioning member 8 can withstand. This arrangement maximizes the amplitude of the oscillations or vibrations induced in the corresponding pre-tensioning member 8 and / or the oscillations generated in the corresponding pre-tensioning member, thereby increasing the removal of ice from the wind turbine 1 components.

[0109] In some arrangements, the tension generated by the tensioning device 9 in the corresponding pre-tensioning member 8 (i.e., in the retracted state) can be less than the maximum tension that the tensioning device 9 is capable of generating. For example, the tension can be at least 70%, preferably at least 75%, preferably at least 80%, preferably at least 85%, preferably at least 90%, preferably at least 95% of the maximum tension that the tensioning device 9 is capable of generating. In some arrangements, the generated tension can be between 80% and 90% of the maximum tension that can be generated. Operating at a tension below the maximum tension that can be generated reduces the risk of damage to the wind turbine components 1 (e.g., the tensioning device 9, the pre-tensioning member 8, the blade connection member 6) if they are always operated at their maximum capacity.

[0110] In some arrangements, the maximum tension that the tensioning device 9 can generate in the pre-tensioning member 8 is in the range of 100 kN to 600 kN, preferably in the range of 200 kN to 400 kN, preferably in the range of 250 kN to 350 kN, and preferably in the range of 275 kN to 325 kN. In some arrangements, the maximum tension that can be generated may be 300 kN.

[0111] In some arrangements, the tension generated by the tensioning device 9 in the corresponding pre-tensioned member 8 can be lower. For example, the tensioning device 9 can be moved towards the extended state to reduce the tension in the corresponding pre-tensioned member 8. Reducing the tension in the corresponding pre-tensioned member 8 can promote an increase in the vibration amplitude of the corresponding wind turbine component (e.g., when excited). The increased vibration amplitude may be more conducive to inducing strain and cracking in ice present on the corresponding component. In this way, ice removal from the corresponding component can be improved.

[0112] It should be understood that the de-icing system 17 can be configured to control one or more tensioning devices 9 to apply varying tension to the pre-tensioned member 8 based on various inputs, such as from a user or sensor arrangement. The de-icing system 17 can be configured to control each tensioning device 9 to apply a different tension to each corresponding pre-tensioned member 8.

[0113] The de-icing system 17 can be configured to control one or more tensioning devices 9 to cyclically extend and retract in order to generate oscillations in the flapping direction or the edge direction in at least some of the wind turbine blades 5. The term "oscillation in the flapping direction" refers to oscillations occurring in the flapping direction of the corresponding blade 5, i.e., in a direction perpendicular to the plane defined by the turbine rotor 1 (i.e., the rotating blades). The term "oscillation in the edge direction" refers to oscillations occurring in the edge direction of the corresponding blade 5, i.e., in a direction parallel to the plane defined by the turbine rotor 1. This arrangement can facilitate adjusting the oscillation direction of the corresponding blade 5 based on, for example, the position of ice on the blade 5.

[0114] In some arrangements, the de-icing system 17 is configured to control one or more tensioning devices 9 to cyclically extend and retract at a frequency substantially equal to the natural frequency of the corresponding wind turbine blade 5. This arrangement causes the pre-tensioning member 8 and / or the blade connecting member 6 to oscillate at a frequency substantially equal to the natural frequency of the corresponding wind turbine blade 5. It has been found that operating in this manner increases the excitation of the wind turbine blade 5, increases de-icing, and requires less energy to induce oscillations. In some arrangements, the de-icing system 17 is configured to control one or more tensioning devices 9 to cyclically extend and retract at a frequency substantially equal to the natural frequency of the corresponding pre-tensioning member 8 or the blade connecting member 6. In this manner, the corresponding pre-tensioning member 8 and / or the blade connecting member 6 oscillates at a frequency substantially equal to the natural frequency of the pre-tensioning member 8 or the blade connecting member 6. The natural frequency can be in the edge direction or the flapping direction. The natural frequency can be known to the de-icing system 17 (e.g., stored in the memory of the de-icing system 17). In some arrangements, the de-icing system 17 can be configured to control the tensioning device 9 to cyclically extend and retract at a frequency substantially equal to the harmonics of the wind turbine blades (e.g., first harmonic, second harmonic, or higher).

[0115] like Figure 3As shown, in some arrangements, the de-icing system 17 may be coupled to the pitch mechanism 50. The de-icing system 17 may be configured to control the pitch mechanism 50 to change the pitch of one or more corresponding wind turbine blades 5. This arrangement can facilitate the removal of ice from the corresponding blades 5. Adjusting the pitch of the wind turbine blades 5 can improve the removal of ice obtained by generating oscillations in the blades 5. In some arrangements, the de-icing system 17 may be configured to control the pitch mechanism 50 to change the pitch of all blades 5 simultaneously to avoid imbalance of the wind turbine 1. When the wind turbine 1 is not operating (i.e., when the blades 5 are not rotating), using the pitch to influence ice removal is most effective because, if operating, changing the pitch will affect the rotational speed of the wind turbine 1. As used herein, it should be understood that the term "pitch" refers to the angle of the wind turbine blade relative to the oncoming wind in the wind turbine 1. In some arrangements, the de-icing system 17 is configured to control the pitch mechanism 50 to cyclically change the pitch of the corresponding wind turbine blades 5. Cyclicly changing the pitch of blade 5 causes repetitive motion on the blade surface, which can cause ice to be removed from it.

[0116] In the example arrangement, the de-icing system 17 can be configured to control the pitch mechanism 50 to cyclically change the pitch of the wind turbine blade 5 between a pitch angle of approximately 70° and a pitch angle of approximately 90°. It should be understood that the de-icing system 17 can be configured to simultaneously change the pitch angle and control the tensioning device 9 to generate oscillations in the blade 5 (e.g., as discussed in the example above). In some arrangements, the de-icing system 17 is configured to generate such oscillations at the same frequency as the pitch change frequency of one or more blades 5. In this way, the oscillations of the blade 5 are generated at the same frequency as the pitch change of the blade 5, greatly improving the effectiveness of the de-icing system 17 in removing ice from the blade 5.

[0117] The de-icing system 17 can be configured to control the pitch mechanism 50 to change the pitch of the wind turbine blades 5, causing the blades to be in a substantially stalled state. The term "substantially stalled state" refers to a pitch angle at which the wind turbine blades 5 are positioned, resulting in a reduction or cessation of aerodynamic lift. For example, at low wind speeds (e.g., less than 6 ms). -1 The blade 5 can pitch to a more negative angle, such as toward 0° or toward -5°, to achieve a stall state. Some further examples of operating the de-icing system 17 will now be discussed.

[0118] In one example, wind turbine 1 is configured in power generation mode, so wind turbine blades 5 are rotating. De-icing system 17 is configured to control the first and second tensioning devices 9a, 9b to extend and retract synchronously in a cyclic manner, and to control the third tensioning device 9c to extend and retract out of phase with the first and second tensioning devices 9a, 9b in a cyclic manner. De-icing system 17 can control the tensioning devices 9a, 9b, 9c to generate oscillations in the flapping direction within the pre-tensioned members 8a, 8b, 8c, the frequency of which is substantially equal to the natural frequency (e.g., first or second harmonic) of the wind turbine blades 5 in the flapping direction. This arrangement increases the excitation in the blades 5, resulting in improved de-icing performance. The average pitch angle can be between 0° and 25° (e.g., at low wind speeds such as below 6 ms). -1 When the temperature is close to 0°, and at high wind speeds such as 20-25 ms -1 (Between approximately 20° and 25°). This example is in low wind speeds (e.g., below 6 ms). -1 It is particularly effective under these conditions because it avoids high blade loads.

[0119] In another example, the de-icing system 17 is configured to produce the same oscillations as discussed in the previous example. Unlike the pitch angle discussed in the previous example, the de-icing system 17 is configured to control the pitch mechanism 50 to change the pitch of the wind turbine blades 5, causing the blades to be essentially stalled. This arrangement increases the oscillations of the blades in the edge direction, thereby increasing de-icing. In this arrangement, the presence of the blade connecting member 6 and the pretensioning member 8 provides damping, which generally reduces the level of oscillations in the edge direction. In this way, the risk of damaging the wind turbine 1 due to edge-direction oscillations is reduced compared to a standard wind turbine 1 (i.e., without the blade connecting member 6 and the pretensioning member 8).

[0120] refer to Figure 4 A schematic diagram of the de-icing system 17 is shown. As already discussed, the de-icing system 17 is coupled to the tensioning device 9 and the pitch mechanism 50. The de-icing system 17 may include a heating system 18, which may include one or more electric heating elements and / or a fluid heating system. As will be discussed in more detail below, the heating system 18 can provide heat to various locations on the wind turbine 1 to aid in the removal of ice, as ice is easier to remove if it is partially melted.

[0121] The de-icing system 17 may include one or more sensors 19 for detecting ice accumulation. The de-icing system 17 may control one or more tensioning devices 9, pitch mechanism 50, and / or heating system 18 based on data obtained from the one or more sensors 19. See, for example, [link to relevant documentation]. Figure 5A and Figure 5BSensor 19 may be disposed within or on one or more of the blade connection member 6 or pretensioner member 8 (e.g., embedded in or positioned on the cable). In some examples, the one or more sensors 19 may be positioned away from the blade connection member 6 and pretensioner member 8, such as on a portion of the blade or on the nacelle. Sensor 19 may be configured to detect ice accumulation. Sensor 19 may provide the de-icing system 17 with information about the status of the respective blade connection member 6 or pretensioner member 8 or other components of the wind turbine 1. The de-icing system 17 may operate only when the sensor 19 detects ice accumulation. In this way, the energy requirements of the de-icing system 17 can be reduced, as the system may only operate when needed. The de-icing system 17 may be configured such that the sensors supplementally or alternatively provide the system with information about safety aspects of the blade connection member 6 and / or pretensioner member 8, such as changes in creep rate, amplitude and frequency of natural or induced oscillations / vibrations, or overheating, thereby preventing or reducing the risk of breakage of the blade connection member 6 and / or pretensioner member 8. Sensor 19 may be an accelerometer, a temperature sensor, a position sensor, a load sensor, a strain sensor, or a combination thereof. Alternatively, the sensor may be an indirect sensor. For example, the presence of ice may be detected by one or more sensors that record the power generation of a wind turbine, and the presence of ice on the blades may be determined by the reduction in power generation compared to the wind turbine generator power curve when there is no ice (in other words, a reduction in the power output of the wind turbine may indicate the presence of ice).

[0122] Figure 5A and Figure 5B An example blade connection member 6 or pretensioning member 8 (i.e., a cable that can function as either) is schematically shown. It can be seen that a heating system 18 is provided together with the corresponding blade connection member 6 or pretensioning member 8. The heating system 18 may be embedded, attached, or otherwise fixed or coupled to the corresponding blade connection member 6 or pretensioning member 8. Multiple sensors 19 may be provided together with the corresponding blade connection member 6 or pretensioning member 8, for example, as... Figure 5A As shown, the distribution is along the length of the corresponding blade connecting member 6 or pretensioning member 8. Alternatively, a sensor 19 extending substantially the entire length of the corresponding blade connecting member 6 or pretensioning member 8 can be provided, for example, as shown in the figure. Figure 5B As shown.

[0123] The heating system 18 may include one or more electric heating elements. The electric heating elements can be of any suitable type, such as wire heating elements (e.g., nichrome wire), tubular heaters, infrared heating elements, etc. The electric heating elements provide precise, efficient, and controlled temperature rise to melt ice and evaporate water and / or help remove ice from the corresponding surface.

[0124] In one example, the de-icing system 17 can be configured to protect the blade load-sharing components of the wind turbine 1 that form part of the wind turbine blade 5. Figure 6 An example of a wind turbine blade 5 is shown. Blade 5 includes a suction side 15 and a pressure side 16. The thickness dimension of blade 5 extends between the suction side 15 and the pressure side 16. Each blade 5 may have a cross-section with a substantially circular profile near its root tip 11. Blade 5 may transition from a circular profile to an airfoil profile as it moves outward from its root tip 11. Blade 5 may include a "shoulder" 22 outside the root tip 11, which is the widest portion of the blade with the maximum chord length. Blade 5 may have an airfoil profile with a gradually decreasing thickness in the outer portion of the blade. The gradually decreasing thickness may extend from the shoulder 22 to the tip 12.

[0125] Each blade 5 can be a split blade formed by an inner blade portion 23 and an outer blade portion 24 coupled together. Each blade portion 23, 24 has a blade shell 52, which defines a corresponding leading edge 13a, 13b, trailing edge 14a, 14b, suction side 15a, 15b, and pressure side 16a, 16b.

[0126] The inner portion 23 and the outer portion 24 of each blade 5 can be connected at a joint indicated by the connecting line 40. The connecting line 40 between the inner and outer blade portions 23 and 24 can be spanwise separated and chordally directed. The inner portion 23 of the blade extends from the blade root tip 11 to the connecting line 40. The outer portion 24 of the blade extends from the blade connecting line 40 to the blade tip tip 12.

[0127] It should be understood that the blade 5 may have any number of blade portions 23, 24, with corresponding connecting joints between them. Alternatively, the blade 5 may not be a split blade, but may extend continuously from the root end 11 to the tip end 12 without any connecting joints.

[0128] In some examples, the split blade 5 may include a bolted connection. Figure 7 The diagram illustrates an example connection between the inner and outer blade portions 23 and 24. The blade portions 23 and 24 are coupled via a connection joint including a connector 41. The connector 41 connects a first blade end face 26 of the inner blade portion 23 to a second blade end face 27 of the outer blade portion 24. The connector 41 is adapted to transmit a load between the inner blade portion 23 and the outer blade portion 24.

[0129] Connector 41 can be a metal component, preferably a cast or machined component. Connector 41 can be a composite component. Connector 41 can be a co-cured or co-bonded component. As further described below, the connection points 7a and 7b of the connecting member 6 can be on connector 41 at the connection joint.

[0130] A leading edge extension 42 may extend in front of the leading edge 13 of the blade 5. The leading edge extension 42 may be integrally formed with the connector 41, but it should be understood that, in alternative examples, the leading edge extension 42 may be a separate component from the connector 41. The leading edge extension 42 may include connection points 7a, 7b attached to the connecting member 6. The first and second connection points 7a, 7b may be arranged in front of the leading edge 13 and adjacent to the pressure side 16. This provides additional clearance for the connecting member 6 as the wind turbine blade 5 rotates around the nacelle 3 with the hub 4. In particular, sufficient clearance can be provided between the connecting member 6 and the blade 5 when the blade 5 pitches between approximately -5 degrees and approximately +95 degrees. The connection points on the wind turbine blade 5 may be arranged at locations where the thickness-chord ratio of the wind turbine blade 5 is between 20% and 50%.

[0131] The wind turbine blade 5 may have a fairing 20 extending at least on the leading edge extension 42, such as Figure 8 As shown. The fairing 20 can be secured to the connector 41. In some examples, the connector 41 can extend beyond the profile of the blade housing 52 at the connection joint. This can improve load transfer across the joint, but may require a larger fairing 20. For split blades, the fairing 20 can span the gap between the two blade portions 23, 24 connected by the connector 41 (or any other form of connection). The fairing 20 can extend over the leading edge extension 42 and the connector 41. The fairing 20 can be sealed to the blade housing 52 by any suitable means, such as sealant 46.

[0132] Compared to blades 5 having a leading-edge extension 42 coupled to the blade connection member 6 but without the fairing 20, the fairing 20 is crucial for improving the aerodynamic performance of the split wind turbine blades 5. In some examples, a de-icing system 17 can be configured to protect the fairing 20. For example, oscillations induced in the blade 5 by the de-icing system 17 can be used to remove ice from the fairing 20 located on the blade surface.

[0133] In some examples, the fairing 20 may include a heating system 18, such as... Figure 8 The electric heating element shown. The electric heating element provided to the fairing 20 can be essentially the same as that discussed with respect to the blade connection member 6 or the pretensioning member 8. The electric heating element can be embedded in the fairing 20 or otherwise attached to the surface of the fairing 20. The heating element in or above the fairing 20 helps to remove ice from the fairing 20.

[0134] like Figure 8As shown, the heating system 18 may also include heating elements located in or above the respective wind turbine blades 5. The heating elements can further aid in de-icing from the blades 5.

[0135] While electric heating is the preferred heating method for the de-icing system 17, it is also envisioned that load-sharing components of the wind turbine blades requiring heating could be heated via a fluid heating system. The fluid heating system can transfer heat from a working fluid to the components of the wind turbine 1 that require heating, which are part of the de-icing system 17. The working fluid can be circulated (e.g., by pumping) to transfer heat from a heat source to the components. One advantage of a fluid heating system over an electric heating system is that the working fluid and the conduits used to transport the working fluid can be made of non-conductive materials, thus making them less susceptible to lightning strikes. This avoids the cost and weight associated with lightning protection for at least some components of the anti-icing and / or de-icing system 17. Examples of fluids used in a fluid heating system include: gases, such as dry air; ethylene glycol; ethylene glycol-water mixtures; and brine.

[0136] An example of operating the de-icing system 17 is shown in Figures 9A to 9D As shown in the figure. In the figure, arrows are provided on the pretensioning member 8 to indicate the extension or retraction of the tensioning device 9 connected to the corresponding pretensioning member 8. Arrows are also provided near the corresponding blade 5 to indicate the direction of movement of the blade 5 in response to the extension or retraction of the tensioning device 9.

[0137] exist Figure 9A In this configuration, tensioning device 9a is in the retracted state, while tensioning device 9c is in the extended state. In this way, the tension in pre-tensioning member 8a increases, while the tension in pre-tensioning member 8c is released or reduced. It can be seen that this causes the blade 5a between the two tensioning devices 9a and 9c to move towards the pre-tensioning member 8a with the greater tension. Figure 9B In the opposite case, tensioning device 9c is in the retracted state, and tensioning device 9a is in the extended state. In this case, blade 5a moves toward the pre-tensioning member 8c, which has a greater tension. As will be understood, the cyclical extension and retraction of tensioning devices 9a and 9c, such that one extends while the other retracts (i.e., in phase relationship), will cause blade 5a to... Figure 9A and Figure 9B It oscillates back and forth between the directions shown. This method allows de-icing to be targeted at specific blades.

[0138] refer to Figure 9CTensioning devices 9a and 9b are in the retracted state, thereby applying tension to pre-tensioning members 8a and 8b. Tensioning device 9c is in the extended state, thereby releasing or reducing the tension in pre-tensioning member 8c. In this way, the tension in pre-tensioning member 8c and the corresponding blade connecting member 6c is less than the tension applied to pre-tensioning members 8a, 8b and the corresponding blade connecting members 6a, 6b. As shown, this arrangement causes wind turbine blades 5a and 5c to move toward the pre-tensioning members 8a, 8b with greater tension. Specifically, blade 5a moves toward pre-tensioning member 8a, while blade 5c moves toward pre-tensioning member 8b. Figure 9D In the opposite arrangement, tensioning device 9c is in the retracted state, while tensioning devices 9a and 9b are in the extended state. In this case, blades 5a and 5c move toward the pre-tensioned member 8c with greater tension. As will be understood, the cyclical extension and retraction of tensioning devices 9a, 9b, and 9c, such that two devices 9a and 9b are extended while another device 9c is retracted (i.e., the two devices are synchronized, and the other device is phased with the two devices), will cause blades 5a and 5c to... Figure 9C and Figure 9D The blades oscillate back and forth in the directions shown. This method allows for de-icing in multiple blades.

[0139] The above example can be implemented when the wind turbine 1 is not in power generation mode, so the wind turbine blades 5 do not rotate around the hub 4.

[0140] The de-icing system 17 has been described as providing protection to various components of the wind turbine 1 using various mechanisms. It should be understood that any combination of the above examples can be implemented.

[0141] It should be understood that any references to the electric heating element 18 herein may also apply to fluid heating systems. In this way, the electric heating element 18 in the figures may be replaced by or combined with a fluid heating system; for example, the electric heating element 18 may be used to replace or in combination with a flexible tube carrying the working fluid.

[0142] Although the invention has been described above with reference to one or more preferred embodiments, it should be understood that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A pitch-controlled wind turbine (1) comprising a tower (2), a nacelle (3) mounted on the tower (2), a hub (4) rotatably mounted on the nacelle (3), and at least three wind turbine blades (5), wherein, Each wind turbine blade (5) extends between its tip (12) and its root end (11) connected to the hub (4) via a pitch mechanism (50). The wind turbine (1) also includes: At least three blade connecting members (6), each blade connecting member (6) extending from a connection point (7a, 7b) on a wind turbine blade (5) toward a connection point (7a, 7b) on an adjacent wind turbine blade (5), wherein the connection points (7a, 7b) on a given wind turbine blade (5) are arranged at a distance from the root end (11) and at a distance from the tip end (12) of the wind turbine blade (5); At least three pretensioning members (8), each pretensioning member (8) being connected to one of the blade connecting members (6) and connected to the hub (4) via a tensioning device (9), wherein the tensioning device (9) provides radial movement of the radially inner end of the pretensioning member (8) relative to the axis of rotation (10) of the hub (4) due to the extension or retraction of the tensioning device (9), thereby providing pretension in the blade connecting member (6) to which it is connected; and A de-icing system (17) is coupled to one or more tensioning devices (9) and configured to control the extension or retraction of the one or more tensioning devices (9) to excite at least some of the wind turbine blades (5), blade connecting members (6) and / or pre-tensioning members (8) to remove ice from them.

2. The pitch-controlled wind turbine (1) according to claim 1, wherein, The de-icing system (17) is configured to control one or more tensioning devices (9) to move in a substantially step manner between an extended state and a retracted state in order to change the tension in the corresponding pre-tensioned member (8) in a substantially step manner.

3. The pitch-controlled wind turbine (1) according to claim 2, wherein, The de-icing system (17) is configured to control one or more tensioning devices (9) to apply tension to the corresponding pre-tensioned member (8), wherein the tension is at least 80% of the maximum tension that the tensioning device (9) can produce, preferably the tension is between 80% and 90% of the maximum tension that the tensioning device (9) can produce.

4. A pitch-controlled wind turbine (1) according to any one of the preceding claims, wherein, The de-icing system (17) is configured to control one or more tensioning devices (9) to extend and retract cyclically in order to generate oscillations in at least some of the wind turbine blades (5), blade connecting members (6) and / or pre-tensioning members (8).

5. The pitch-controlled wind turbine (1) according to claim 4, wherein, The de-icing system (17) is configured to control at least two tensioning devices (9) to extend and retract synchronously or in phase relationship.

6. The pitch-controlled wind turbine (1) according to claim 4, wherein, The de-icing system (17) is configured to control the first and second tensioning devices (9a, 9b) to extend and retract synchronously in a cyclic manner, and to control the third tensioning device (9c) to extend and retract out of phase with the first and second tensioning devices (9a, 9b) in a cyclic manner.

7. The pitch-controlled wind turbine (1) according to any one of claims 4 to 6, wherein, The de-icing system (17) is configured to control one or more tensioning devices (9) to cyclically extend and retract in order to generate oscillations in the flapping or edge direction in at least some of the wind turbine blades (5).

8. The pitch-controlled wind turbine (1) according to claim 7, wherein, The de-icing system (17) is configured to control one or more tensioning devices (9) to cyclically extend and retract at a frequency substantially equal to the natural frequency of the corresponding wind turbine blade (5), blade connecting member (6) or tensioning member (8).

9. A pitch-controlled wind turbine (1) according to any one of the preceding claims, wherein, The de-icing system (17) is coupled to the pitch mechanism (50) and configured to control the pitch mechanism (50) to cyclically change the pitch of the corresponding wind turbine blade (5) in order to remove ice from the corresponding wind turbine blade.

10. A pitch-controlled wind turbine (1) according to any one of the preceding claims, wherein, The de-icing system (17) is coupled to the pitch mechanism (50) and configured to control the pitch mechanism (50) to change the pitch of the corresponding wind turbine blade (5) so that the wind turbine blade (5) is essentially stalled.

11. A pitch-controlled wind turbine (1) according to any one of the preceding claims, wherein, The de-icing system (17) includes one or more electric heating elements (18) and / or a fluid heating system.

12. A pitch-controlled wind turbine (1) according to any one of the preceding claims, wherein, The de-icing system (17) includes one or more sensors (19) in or above one or more of the blade connection member (6) or the pre-tensioning member (8) for detecting ice accumulation.

13. A method for de-icing a pitch-controlled wind turbine (1), the pitch-controlled wind turbine (1) comprising: The tower (2), the nacelle (3) mounted on the tower (2), the hub (4) rotatably mounted on the nacelle (3), and at least three wind turbine blades (5), wherein each wind turbine blade (5) extends between its tip (12) and its root (11) connected to the hub (4) via a pitch mechanism (50); At least three blade connecting members (6), each blade connecting member (6) extending from a connection point (7a, 7b) on a wind turbine blade (5) toward a connection point (7a, 7b) on an adjacent wind turbine blade (5), wherein the connection points (7a, 7b) on a given wind turbine blade (5) are arranged at a distance from the root end (11) and a distance from the tip end (12) of the wind turbine blade (5); and At least three pretensioning members (8), each pretensioning member (8) is connected to one of the blade connecting members (6) and connected to the hub (4) via a tensioning device (9), wherein the tensioning device (9) provides radial movement of the radially inner end of the pretensioning member (8) relative to the axis of rotation (10) of the hub (4) due to the extension or retraction of the tensioning device (9), thereby providing pretension in the blade connecting member (6) to which it is connected; The method includes controlling the extension or retraction of one or more tensioning devices (9) to excite at least some of the wind turbine blades (5), blade connecting members (6) and / or pre-tensioning members (8) to remove ice from them.

14. The method of claim 13 further comprises controlling one or more tensioning devices (9) to move in a substantially step manner between an extended state and a retracted state in order to change the tension in the respective pre-tensioned member (8) in a substantially step manner.

15. The method of claim 13 further comprises controlling one or more tensioning devices (9) to cyclically extend and retract to generate oscillations in at least some of the wind turbine blades (5), blade connecting members (6) and / or pretensioning members (8).

16. The method according to any one of claims 13 to 15, wherein, The pitch-controlled wind turbine (1) includes a de-icing system (17), which includes one or more electric heating elements (18) and / or a fluid heating system. The method further includes the following steps: Detect ice accumulated on at least a portion of the wind turbine blades (5), blade connecting members (6), and / or pretensioning members (8). Activate the one or more electric heating elements (18) and / or fluid heating system to weaken the connection between the ice and at least a portion of the wind turbine blade (5), blade connection member (6), and / or pretensioning member (8), and Control the extension or retraction of one or more tensioning devices (9) to excite at least some of the wind turbine blades (5) to release at least a portion of the accumulated ice from the wind turbine blades (5), blade connecting members (6) and / or pretensioning members (8).

17. A tensioning device (9) for de-icing a pitch-controlled wind turbine (1), the pitch-controlled wind turbine (1) comprising a tower (2), a nacelle (3) mounted on the tower (2), a hub (4) rotatably mounted on the nacelle (3), and at least three wind turbine blades (5), wherein, Each wind turbine blade (5) extends between its tip (12) and its root end (11) connected to the hub (4) via a pitch mechanism (50), and the wind turbine (1) further includes: At least three blade connecting members (6), each blade connecting member (6) extending from a connection point (7a, 7b) on a wind turbine blade (5) toward a connection point (7a, 7b) on an adjacent wind turbine blade (5), wherein the connection points (7a, 7b) on a given wind turbine blade (5) are arranged at a distance from the root end (11) and at a distance from the tip end (12) of the wind turbine blade (5); At least three pretensioning members (8), each pretensioning member (8) being connected to one of the blade connecting members (6) and connected to the hub (4) via a tensioning device (9), wherein the tensioning device (9) provides radial movement of the radially inner end of the pretensioning member (8) relative to the axis of rotation (10) of the hub (4) due to the extension or retraction of the tensioning device (9), thereby providing pretension in the blade connecting member (6) to which it is connected; and A de-icing system (17) is coupled to one or more tensioning devices (9) and configured to control the extension or retraction of the one or more tensioning devices (9) to excite at least some of the wind turbine blades (5), blade connecting members (6) and / or pre-tensioning members (8) to remove ice from them.

18. The use according to claim 17, wherein, The de-icing system (17) includes one or more electric heating elements (18) and / or a fluid heating system.

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