Toe angle control for multirotor wind turbines

Abstract

The invention relates to a multi-rotor wind turbine comprising at least two rotor nacelle assemblies mounted on a support device by respective yaw systems, and a toe angle control system for controlling a toe angle of the rotor nacelle assemblies relative to the support device; wherein the toe angle control system is configured to operate in a first mode in which the rotor nacelle assemblies are maintained in a positive toe angle when the wind turbine is generating electricity in a primary production mode; wherein the toe angle control system is further configured to monitor an operating mode of the wind turbine and to switch to a second mode in which the yaw systems of the rotor nacelle assemblies are operated to reduce the toe angle of the rotor nacelle assemblies if a trigger condition based on the operating mode has been met.

Description

Technical Field

[0001] This invention relates to a control system for a multi-rotor wind turbine, including a multi-rotor wind turbine with such a control system, and a method for controlling a multi-rotor wind turbine. Background Technology

[0002] The general trend in the wind power industry is to use increasingly larger wind turbines with larger rotors to maximize power output from each turbine, thereby reducing the cost of electricity production.

[0003] One approach to providing large, cost-effective wind turbines is the multi-rotor wind turbine (MR wind turbine). Figure 1 An example is illustrated schematically. The MR wind turbine 1 includes multiple rotor nacelle assemblies (RNAs) 3, each of which includes a rotor 4 and a generator housed within a nacelle 5 and configured for generating electricity. Each RNA 3 is mounted on a common tower 2 via a support device 6, which includes one or more RNA support elements, such as arms 8, extending outward from the tower 2 in opposite directions. Figure 1 A turbine with four RNAs arranged in a single layer is shown, but other arrangements using two or more RNAs are also feasible.

[0004] The support device 6 can be mounted on the tower via a central yaw system 9, which is configured to change the yaw angle of the support device 6 relative to the tower 2, thereby aligning the RNA3 mounted thereon with the prevailing wind direction. The central yaw system 9 can be an active system configured to move the support device 6 relative to the tower 2, or a passive system configured to use wind power to control the angle of the support device 6, as described in US2018023543 and US2019048847.

[0005] EP3339631 describes a multi-rotor wind turbine in which a pair of upwind / downwind facing RNAs are additionally mounted on a common beam by separate yaw systems configured to yaw the RNAs relative to the beam in order to individually adjust the alignment of the RNAs with the prevailing wind direction.

[0006] The toe angle of RNA3 can be defined as the angle A in the horizontal plane between the plane 4' where the rotor 4 is located and the support device 6, such as... Figure 2As shown. It should be understood that the plane 4' of rotor 4 is the plane in which the rotor rotates, that is, the plane perpendicular to the axis of rotation of the rotor. In some cases, the lead angle of RNA 3 can be measured relative to the longitudinal direction of the arm 8 on which RNA 3 is mounted. However, when the support arm 8 does not extend in a common vertical plane, for example, when the support arm 8 is angled in the windward direction, the lead angle of RNA 3 is preferably measured relative to the plane 6' of the entire support device 6, which is a vertical plane passing through the mounting point of RNA 3 or the yaw axis.

[0007] In some cases, the blades of rotor 4 can be arranged at a conical angle such that the longitudinal axis of the blades is not perpendicular to the rotation axis of rotor 4. For example, the blades of rotor 4 can be angled away from the support device 6 in the windward direction to increase the clearance between the blade tips and the support device 6. (It should be understood that in this case, the plane 4' of rotor 4 is still perpendicular to the rotation axis of rotor and is not affected by the conical angle of the blades.)

[0008] To ensure sufficient end gap between the blade tip and support device 6, RNA 1 can also be manipulated to be at a positive toe angle, such as... Figure 2 As shown. (It should be understood that this is for illustrative purposes only.) Figure 2 The positive toe angle was exaggerated. Choosing a positive toe angle further increased the end clearance. However, the resulting increase in yaw error between the rotor 4 axis and the prevailing wind direction may also lead to increased loads on rotor 4, support 6, and tower 2 under strong wind conditions.

[0009] It is against this backdrop that the present invention was designed. Summary of the Invention

[0010] A first aspect of the invention provides a multi-rotor wind turbine including at least two rotor nacelle assemblies mounted on a support via corresponding yaw systems, and a toe angle control system for controlling the toe angle of the rotor nacelle assemblies relative to the support; wherein the toe angle control system is configured to operate in a first mode, in which the rotor nacelle assemblies are maintained at a positive toe angle when the wind turbine is generating electricity in a primary production mode; wherein the toe angle control system is further configured to monitor the operating mode of the wind turbine and switch to a second mode if a triggering condition based on the operating mode is met, wherein in the second mode, the yaw system of the rotor nacelle assemblies is operated to reduce the toe angle of the rotor nacelle assemblies.

[0011] By maintaining the nacelle assembly at a positive toe angle in the first mode, the toe angle control system ensures sufficient end clearance between the blade tips and the support structure when the wind turbine is operating in its primary production mode and generating electricity. However, by switching to a second mode in which the toe angle of the nacelle assembly is reduced, the toe angle control system also allows the yaw error of each nacelle assembly to be minimized under certain operating conditions, such as at high wind speeds. In this way, the present invention reduces the load on the wind turbine under extreme weather conditions, thereby reducing the weight and cost of various components of the wind turbine, including the blades.

[0012] According to embodiments of the present invention, various different operating mode-based triggering conditions can be set to switch the toe angle control system to a second mode, thereby reducing the toe angle of the rotor nacelle assembly. For example, the operating mode-based triggering conditions may include any one or more of the following: a) the wind turbine has exited the main production mode, b) the wind turbine has entered a derating production mode or a high-wind production mode, c) the wind turbine has entered a cut-out mode or an idling mode due to high wind speeds, and d) the wind turbine has entered a shutdown mode or a disconnect mode, wherein the wind turbine is disconnected from the power grid.

[0013] In some embodiments, the toe angle control system may be configured to automatically switch to the second mode as long as one or more of the above-described operating modes or modes have been detected. However, in other embodiments, the triggering conditions based on the operating mode may also include further requirements, wherein at least some of the requirements may not be directly related to the operating mode or production status of the wind turbine.

[0014] For example, the triggering conditions based on the operating mode can additionally include wind speed-related requirements, which could cause the toe angle control system to switch to the second mode only under certain wind conditions. In this case, the toe angle control system can be configured to calculate or receive measured or estimated wind speeds, compare the measured or estimated wind speeds with a wind speed threshold, and switch to the second mode only if the wind speed threshold is exceeded. In one specific example, the wind speed threshold could be equal to the cut-out speed of the wind turbine. However, in other embodiments, a higher wind speed threshold can be set.

[0015] Alternatively or additionally, the triggering conditions based on the operating mode may include one or more requirements related to the operating state of a single rotor nacelle assembly. For example, the requirements for the operating state of the rotor nacelle assembly may include any one or more of the following: for at least one rotor nacelle assembly, the power output has dropped below a threshold level, the rotor speed has dropped below a threshold level, the rotor has stopped, and the blades have been feathered beyond a threshold position. In this case, the toe angle control system may be configured to switch to the second mode only if one or more rotor nacelle assemblies have met certain predetermined operating criteria, or to apply the second mode only to rotor nacelle assemblies that have met certain predetermined operating criteria.

[0016] The toe angle control system can be configured to maintain at least substantially constant toe angle of the rotor nacelle assembly when operating in the first mode. In this way, the toe angle control system can have a particularly simple and reliable design. However, the control system can also be configured to adjust the yaw angle via the yaw system of the rotor nacelle assembly, for example, in response to rapid changes in wind direction, when the toe angle control system is operating in the first mode.

[0017] The toe angle control system can be configured to maintain a positive toe angle of at least 2 degrees for the rotor nacelle assembly when operating in the first mode, preferably in the range of 2 to 8 degrees. In one specific embodiment, the toe angle control system can be configured to maintain a positive toe angle of approximately 6 degrees when operating in the first mode, but other values ​​are also possible.

[0018] The toe angle control system can be configured to maintain at least substantially constant toe angles of approximately 0 degrees for the rotor nacelle assembly when operating in the second mode. It should be understood that a 0-degree toe angle also corresponds to a 0-degree yaw error (provided the support structure is aligned with the prevailing wind direction). Generally, once the toe angle control system has been switched to the second mode, it is advantageous to keep the toe angle of each rotor nacelle assembly as close to 0 degrees as possible to maintain a yaw error as close to 0 degrees as possible for each rotor nacelle assembly, thereby minimizing the load on the wind turbine. However, it should be understood that small positive or negative toe angles may still exist, for example, toe angles in the range of -1 to 1 degree.

[0019] When operating in the second mode, the toe angle control system can be configured to maintain the toe angle of each rotor nacelle assembly less than the minimum toe angle allowed by the toe angle control system when operating in the first mode.

[0020] In some embodiments, when the current toe angle control system is operating in the first toe angle control mode and / or the second toe angle control mode, the yaw system of the rotor nacelle assembly can be locked by a locking system to ensure that the rotor nacelle assembly does not deviate from the expected toe angle.

[0021] The toe angle control system may include at least one data structure, such as a lookup table, defining multiple toe angle reference values, and may be configured to select a toe angle reference value for each component in the nacelle assembly based on the wind turbine's operating mode (and optionally further, additional requirements). The toe angle reference value may be defined relative to the plane of the support structure, or alternatively, relative to a default yaw position, such as the yaw position used by the wind turbine during primary production mode operation. The control system may be configured to forward the selected toe angle reference value to the yaw actuator of the yaw system of the corresponding nacelle assembly, which may use closed-loop control to maintain the nacelle assembly at the required toe angle.

[0022] The wind turbine may also include a central yaw system (in addition to a separate yaw system for the rotor nacelle assembly), which is configured to change the yaw angle of the support structure relative to the base of the wind turbine. The central yaw system can be an active or passive system.

[0023] The central yaw system can be the primary yaw system used to align the rotor nacelle assembly with the prevailing wind direction. In this case, when the current toe angle control system enters the second mode, the individual yaw system of the rotor nacelle assembly can primarily be used to reduce the toe angle of the rotor nacelle assembly relative to the support structure. However, as mentioned above, the individual yaw system of the rotor nacelle assembly can also perform additional yaw angle adjustments, such as in response to rapid changes in wind direction.

[0024] It should be understood that the present invention can be applied to many different types and configurations of multi-rotor wind turbines. For example, the wind turbine may be an onshore or offshore wind turbine and may include any suitable number of rotor nacelle assemblies, such as 2, 4, 6 or more. In one specific embodiment, the rotor nacelle assembly may be mounted to the tower via one or more common support structures, each common support structure comprising a pair of arms extending outward from the wind turbine tower in opposite, generally horizontal directions, but other configurations are also possible.

[0025] Another aspect of the present invention provides a method for operating a multi-rotor wind turbine, the multi-rotor wind turbine including at least two rotor nacelle assemblies mounted on a support device via corresponding yaw systems, the method comprising: operating the wind turbine in a primary production mode, in which the rotor nacelle assemblies are used for power generation; maintaining the rotor nacelle assemblies at a positive toe angle while the wind turbine is operating in the primary production mode; monitoring the operating mode of the wind turbine; and operating the yaw system of the rotor nacelle assemblies to reduce the toe angle of the rotor nacelle assemblies based on the satisfaction of triggering conditions based on the operating mode.

[0026] The method may generally include any steps related to the normal operation of the aforementioned multi-rotor wind turbine. Attached Figure Description

[0027] To provide a more complete understanding, the invention will now be described by way of example only with reference to the following figures, in which:

[0028] Figure 1 A multi-rotor wind turbine to which the invention can be applied is schematically illustrated according to a feasible embodiment;

[0029] Figure 2 schematically shown Figure 1 The plan view of the wind turbine shown;

[0030] Figure 3 schematically shown Figure 1 The system-level architecture of the wind turbine is shown.

[0031] Figure 4 The formation is schematically shown. Figure 1 The toe angle control system is part of the overall control system of the wind turbine shown.

[0032] Figure 5 A simplified example of a lookup table that can be used according to a feasible embodiment of the present invention is shown;

[0033] Figure 6a and Figure 6b The diagram schematically illustrates operation under different toe angle control modes. Figure 1 A plan view of a wind turbine; and

[0034] Figure 7a and 7b A schematic plan view of another multi-rotor wind turbine to which the invention can be applied under different toe angle control modes is shown. Detailed Implementation

[0035] Figures 1 to 3 An example of a multi-rotor wind turbine suitable for use with embodiments of the present invention is illustrated schematically. However, it should be understood that the invention can also be applied to wind turbines with... Figures 1 to 3 Many other types of multi-rotor wind turbines with different configurations are shown and described below.

[0036] Figure 1 The multi-rotor wind turbine 1 shown includes a tower 2 that extends upward from a base in a generally vertical direction. The wind turbine 1 can be an onshore or offshore wind turbine, so the base of the tower 2 can be connected to a land or offshore platform.

[0037] The wind turbine 1 includes an array of rotor nacelle assemblies (RNAs) 3, which comprises four individual RNAs. Each RNA 3 includes an upwind HAWT-type rotor 4, which is rotatably mounted on the housing or nacelle 5 and configured to drive a generator located within the nacelle in a conventional manner, as will be described in detail below.

[0038] RNA 3 is mounted on the tower 2 of the wind turbine 1 by a support device comprising a pair of common support structures 6. The first of the support structures 6 is mounted on the tower 2 adjacent to the upper end of the tower 2, and the second of the support structures 6 is mounted on the tower 2 at a midpoint along the height of the tower 2. Each of the support structures 6 includes: a mounting portion 7 through which the support structure 6 is mounted to the tower 2; and a pair of support elements or arms 8 extending outward from the mounting portion 7 in opposite directions. Each of the arms 8 supports a corresponding one of the RNA 3 located at or near its distal end, thereby mounting the RNA 3 to the tower 2 of the wind turbine 1.

[0039] exist Figure 1 In the diagram, each arm 8 is shown extending outward from the tower 2 in a generally horizontal direction. Furthermore, as... Figure 2 As shown, the arm 8 of each support structure 6 is shown extending in a common vertical plane. However, it should be understood that many other configurations are also possible, as described in more detail below. For example, in other embodiments, the arm 8 may be angled in an upward and / or forward (windward) direction.

[0040] Each of the mounting portions 7 of the support structure 6 is mounted to the tower 2 via a corresponding central yaw system 9, which is configured to change the yaw angle of the support structure 6 relative to the tower 2. The central yaw system 9 provides the main mechanism for aligning the RNA3 with the prevailing wind direction.

[0041] Furthermore, each RNA 3 is mounted on its respective arm 8 via a separate RNA yaw system 10. Each RNA yaw system 10 includes a mounting device that supports the weight of its RNA 3 while allowing pivotal movement about a vertically extending yaw axis, and at least one yaw actuator operable to change the yaw angle of the RNA 3. Thus, the yaw system 10 of the RNA 3 is capable of changing the front beam angle of the RNA 3 relative to the support structure 6, as described in more detail below. In some embodiments, the yaw system 10 may additionally include a locking system configured to physically lock the yaw system 10 to prevent unwanted changes in the front beam angle of the RNA 3.

[0042] Figure 3The system-level architecture of the wind turbine 1 is schematically illustrated. For clarity, only the main components and systems for a single RNA 3 are shown. However, it should be understood that each RNA 3 includes similar components and is configured to operate in a similar manner.

[0043] like Figure 3 As shown, each RNA 3 includes a power generation system 11 comprising a generator 13 housed within a nacelle 5. The generator 13 is coupled to a rotor 4 (optionally via a gearbox 12) and configured to generate electricity when torque is applied to the rotor 4. The output of the generator 13 is connected to a converter system 14, which converts the electricity generated by the generator 13 into a suitable frequency and voltage for continued transmission. The power distribution unit 15 of the wind turbine 1 is configured to receive the electricity generated by each RNA 3 and transmit the generated electricity to an external load 16, such as the local power grid of the power plant where the wind turbine 1 is located.

[0044] The precise configuration of the power generation system 11 and its connection to the external load 16 are not critical to this invention and will therefore not be discussed further. However, it should be understood that other suitable configurations can also be used within the scope of this invention.

[0045] Just like Figure 3 As shown, the wind turbine 1 includes a central controller 30 configured to control the overall operation of the wind turbine 1. Additionally, each RNA 3 also has its own local controller 40 configured to control the operation of its corresponding RNA 3. The central controller 30 and the local controllers together form the overall control system 20 of the wind turbine 1.

[0046] The central controller 30 and the local controllers 40 each include multiple processing units and storage modules, which may be centrally located at discrete locations or alternatively distributed across multiple locations within the wind turbine. In this embodiment, the central controller 30 is housed in the tower 2 of the wind turbine 1, and the local controller 40 is housed in the nacelle 5 of the corresponding RNA 3. However, in other embodiments, the central controller 30 and the local controllers 40 may be located in other suitable locations. Furthermore, in other embodiments, some or all of the functions of the local controller 40 may be performed by the central controller 30, in which case at least multiple portions of the local controller 40 may be integrated with the central controller 30.

[0047] The central controller 30 is connected and configured to receive input signals from the wind farm controller 50 and multiple sensors associated with the wind turbine 1. These sensors include at least one wind speed sensor 21 and at least one wind direction sensor 22. The wind speed sensor 21 and wind direction sensor 22 may be mounted on the wind turbine 1, for example, on one or more accumulators 3 or near the upper end of the tower 2, or alternatively at another suitable location near the wind turbine 1. Of course, the central controller 30 is also connected to a number of other sensors, including speed sensors and load sensors, etc. However, for clarity, these additional sensors are... Figure 3 The middle part has been omitted.

[0048] The central controller 30 is configured to control the operation of the wind turbine 1 based on received input signals. For example, the central controller 30 is configured to receive a power demand signal from the wind farm controller 50 and control the power output of the wind turbine 1 via the local controller 40 of the RNA 3 to meet the received power demand. Furthermore, the central controller 30 is also configured to receive a signal representing the prevailing wind direction from the wind direction sensor 22 and control the operation of the central yaw system 9 to yaw the support structure 6 relative to the tower 2 so that the RNA 3 is aligned with the prevailing wind direction.

[0049] According to a feasible embodiment of the present invention, the control system 20 of the wind turbine 1 includes a toe angle control system or a yaw control system 100, which is configured to control the toe angle or yaw angle of the RNA3 relative to the support structure 6. Figure 4 The toe angle control system 100 is schematically shown in the figure.

[0050] For clarity, Figure 4 Only a few parts of the overall control system 20 directly involved in controlling the anterior bundle angle of RNA 3 are shown; the remaining sensors and controllers have been omitted. However, it should be understood that the overall control system 20 also includes other controllers and sensors, some of which may be integrated with… Figure 4 One or more components of the toe-in control system 100 shown in the figure communicate with each other.

[0051] like Figure 4As shown, the central controller 30 of the wind turbine 1 includes a production status controller 31. The production status controller 31 is configured to set the operating mode or production mode of the wind turbine 1. Selectable modes may include, for example, a start-up mode, a primary production mode, a derating production mode, a high-wind production mode, a high-wind idling mode, a cut-out mode, a grid shutdown / disconnection mode, and a shutdown / power-off mode. For example, the production status controller 31 is configured to select the primary production mode when the wind turbine 1 has been instructed to generate electricity and the current wind speed is higher than the cut-in wind speed but lower than the cut-out wind speed; and to select the cut-out mode when the wind turbine 1 is turned on and the current wind speed is higher than the cut-out wind speed. The production status controller 31 is also configured to transmit the selected operating mode to other parts of the control system 20, thereby ensuring that the wind turbine 1 operates in the intended mode.

[0052] Just like Figure 4 As shown, the local controller 40 for each RNA 3 includes a front beam angle reference selector 41. Each front beam angle reference selector 41 is configured to receive an indication from the production status controller 31 regarding the current operating mode or production mode, and set a front beam angle reference value for its corresponding RNA 3 according to the transmitted operating mode. Each front beam angle reference selector 41 is also configured to transmit the selected front beam angle reference value to its corresponding RNA yaw system 10, which applies closed-loop control to maintain the RNA 3 at the front beam angle value specified by the front beam angle reference selector 41.

[0053] According to a feasible embodiment of the invention, each pre-beam angle reference selector 41 includes a lookup table 42 configured to set the pre-beam angle of its corresponding RNA3. Figure 5 A simplified example of this lookup table 42 is shown.

[0054] like Figure 5 As shown, each toe angle reference selector 41 is configured to operate in one of two selectable modes: a first mode, or normal toe angle control mode, where the toe angle reference value is fixed at 6 degrees; and a second mode, or reduced toe angle mode, where the toe angle reference value is fixed at 0 degrees. Also as... Figure 5 As shown, each toe angle reference selector 41 is configured to switch between its first mode and second mode, depending on the current operating mode of the wind turbine 1.

[0055] For example, if wind turbine 1 is currently operating in the primary production mode, this information is transmitted to the toe angle reference selector 41. Since the primary production mode corresponds to the first toe angle control mode, the toe angle reference selector 41 transmits a toe angle reference value of 6 degrees to the yaw system 10 of RNA 3. This causes the yaw system 10 to maintain RNA 3 at a toe angle of 6 degrees, as... Figure 6a As shown schematically. If the yaw system 10 is equipped with a locking system, the locking system can be engaged to prevent unnecessary changes in the toe angle of the RNA3. In this way, when the wind turbine 1 is operating in the main production mode, the toe angle control system can ensure that sufficient tip clearance is maintained between the blade tip of the RNA3 and the support structure 6.

[0056] However, if the production status controller 31 switches the wind turbine 1 to cut-out mode because the wind speed has exceeded the cut-out wind speed of the wind turbine 1, this information is transmitted to the toe angle reference selector 41. Since the wind turbine 1 has exited the main production mode and entered the cut-out mode, the operating mode-based triggering condition for switching the toe angle control system 100 to the second toe angle control mode is met. Therefore, the toe angle reference selector 41 will operate according to the second toe angle control mode and transmit a 0-degree toe angle reference value to the yaw system 10 of the RNA 3. This causes the yaw system 10 to move the RNA 3 to a state with a reduced toe angle, such as... Figure 6b As shown schematically. In this way, as long as the cutoff wind speed of the wind turbine 1 is exceeded, the toe angle control system 100 can reduce the toe angle of the RNA 3, thereby also reducing the yaw error of the RNA.

[0057] If the yaw system 10 is equipped with a locking system, the locking system can disengage when the current beam angle control system 100 switches from the first beam angle control mode to the second beam angle control mode, and re-engage once the RNA 3 has reached the expected beam angle, thereby preventing unnecessary changes in the beam angle of the RNA 3 while the beam angle control system 100 remains in the second beam angle control mode.

[0058] like Figure 5 As shown, when wind turbine 1 is disconnected from the local or external power grid, and when wind turbine 1 is shut down, the toe angle reference selector 41 is also configured to switch to a second toe angle control mode, thereby reducing the toe angle of each RNA 3. In this case, the operation of the toe angle control system 100 and the RNA yaw system 10 can be powered by an emergency power supply. In this way, it can be ensured that when the wind turbine is shut down, the RNA 3 is in a state of reduced toe angle.

[0059] When the wind turbine 1 returns to the start-up mode or one of its production modes, the toe angle control system 100 then switches back to the first toe angle control mode, in which the toe angle of the RNA is set back to 6 degrees to ensure sufficient end clearance between the blade tip of the RNA 3 and the support structure 6.

[0060] In some cases, the control system 20 of the wind turbine 1 can be configured to suppress the operation of the wind turbine 1 in certain modes until RNA 3 has reached its predetermined yaw angle position. For example, when the wind turbine 1 enters the start-up mode, rotor 4 can be prevented from restarting until RNA 3 has reached a yaw angle of 6 degrees specified for the start-up mode.

[0061] The examples described above have been included for ease of understanding of the invention. However, it should be understood that many modifications and variations can be made within the scope of the appended claims.

[0062] For example, in the above embodiments, each RNA 3 includes a local controller 40, which includes its own front beam angle reference selector 41 configured to set a front beam angle reference value for that RNA 3. However, in other embodiments, the front beam angle control system 100 may not include a separate front beam angle reference selector 41 for each individual RNA 3. For example, the central controller 30 may include a common front beam angle reference selector, which may be configured to set a front beam angle reference value for each RNA 3 and transmit the selected front beam angle reference value to the yaw system 10 of each RNA 3.

[0063] In the above embodiments, the toe angle control system 100 is configured to switch to the second toe angle control mode only when the wind turbine 1 is idling, cut off, disconnected, or shut down. However, in another embodiment, the second toe angle control mode can also be applied when the wind turbine is operating in derating production mode and / or high wind production mode. In this case, Figure 5 The lookup table 42 shown can also specify a 0-degree toe angle reference value for these operating modes.

[0064] Furthermore, in the above embodiments, the toe angle control system 100 is configured to switch between a first toe angle control mode and a second toe angle control mode solely based on the operating mode or production mode of the wind turbine 1. However, in other embodiments, the triggering conditions for entering the second toe angle control mode and thereby reducing the toe angle of the RNA 3 may also include further requirements related to the operating state of the individual RNA 3. For example, the toe angle control system 100 may be configured to enter the second mode only if each RNA 3 has met certain criteria, or to apply the second mode only to RNA 3s that have met certain criteria. Examples of such criteria may include, for example, power output has dropped below a threshold level, rotor speed has dropped below a threshold level, the rotor has stopped, and / or the blades have been feathered beyond a threshold position.

[0065] In some embodiments, the triggering condition for entering the second toe angle control mode may additionally include a wind speed-related requirement to prevent RNA3 from yawing to their reduced yaw angle state unless the wind turbine 1 is experiencing high wind speeds. For example, the toe angle control system 100 may be configured to calculate or receive measured or estimated wind speeds, such as from the wind speed sensor 21, compare the measured or estimated wind speeds with a wind speed threshold, and switch to the second mode only if the wind speed threshold has been exceeded.

[0066] In the above embodiments, the toe angle control system is configured to maintain RNA3 at a fixed toe angle of 6 degrees when operating in the first toe angle control mode, and to maintain the rotor nacelle assembly 3 at a fixed toe angle of 0 degrees when operating in the second toe angle control mode. However, in other embodiments, when the toe angle control system 100 is operating in the first toe angle control mode and / or the second toe angle control mode, the toe angle of RNA3 can also be changed, for example, in response to a change in the operating mode of the wind turbine 1 or in response to a change in operating conditions such as wind speed or wind direction. In this case, the toe angle reference selector 41 can store multiple different toe angle reference values ​​within the first toe angle control mode and / or the second toe angle control mode, which can be selected according to the current operating mode or wind conditions.

[0067] In addition, the pre-beam angle control system 100 may also be configured to reduce the pre-beam angle of the RNA in response to other situations besides those described above, such as during maintenance or when one or more of the RNAs are not functioning.

[0068] In the above embodiments, the invention is applied to a wind turbine 1 comprising an array of four RNAs 3 mounted on a vertical tower 2 by a pair of support structures 6, each support structure comprising a pair of arms 8 extending outward from the tower 2 in a generally horizontal direction within a common vertical plane. However, it should be understood that the invention can also be applied to wind turbines with different numbers of RNAs 3 and / or different support configurations. For example, in other embodiments, the arms 8 may be angled upward or downward as they extend away from the tower 2, or they may be angled in a windward or leeward direction.

[0069] Figure 7a and Figure 7b A schematic plan view of another multi-rotor wind turbine to which the invention can be applied, according to another feasible embodiment of the invention, is shown. Figure 7a and Figure 7b The wind turbine shown in the image is combined with the one above. Figure 1 and Figure 2The wind turbines 1 described are generally similar, therefore the same reference numerals are used to identify the same features of the wind turbines 1. However, as Figure 7a and Figure 7b As shown, the arm 8 of this alternative wind turbine 1 does not extend in a common vertical plane, but is angled in the windward direction. Furthermore, the arm 8 is reinforced by support lines, which helps reduce the pressure exerted on the mounting portion 7 of the support structure 6 and the arm 8. (These support lines are in...) Figure 1 and Figure 2 Not shown, but may be included if necessary. Figure 1 and Figure 2 (in wind turbines)

[0070] although Figure 7a and Figure 7b The configuration of the wind turbine 1 shown in the figure is similar to Figure 1 and Figure 2 The wind turbines shown in the diagram have different configurations, but RNA 3 can still be configured in an equivalent manner, such as... Figure 7a The positive toe angle state shown and as follows Figure 7b The reduced toe angle states shown are selectively switched. However, since the arms 8 of this alternative wind turbine 1 do not extend in a common vertical plane, the toe angle of RNA3 is preferably measured relative to the plane 6' of the support structure 6 (i.e., the vertical plane in which the yaw axis of RNA3 is located) rather than relative to the longitudinal direction of the individual arms 8.

[0071] Other modifications and changes, including other physical configurations of the multi-rotor wind turbine, are also apparent to technicians.

Claims

1. A multi-rotor wind turbine, comprising at least two rotor nacelle assemblies mounted on a support via a corresponding yaw system, and a toe angle control system for controlling the toe angle of the rotor nacelle assemblies relative to the support, wherein the toe angle is defined as the angle in the horizontal plane between the plane containing the rotors of the rotor nacelle assemblies and the support; in, The toe angle control system is configured to operate in a first mode, in which the rotor nacelle assembly is maintained at a positive toe angle when the wind turbine is generating electricity in the main production mode, wherein the positive toe angle is formed when the rotor deflects away from the support in the windward direction. The toe angle control system is further configured to monitor the operating mode of the wind turbine and switch to a second mode when the triggering conditions based on the operating mode are met. In the second mode, the yaw system of the rotor nacelle assembly is operated to reduce the toe angle of the rotor nacelle assembly.

2. The wind turbine according to claim 1, wherein, The triggering condition based on the operating mode includes the wind turbine exiting the main production mode.

3. The wind turbine according to claim 1 or 2, wherein, The triggering conditions based on the operating mode include the wind turbine having entered a derated production mode or a high-wind production mode.

4. The wind turbine according to claim 1 or 2, wherein, The triggering conditions based on the operating mode include the wind turbine having entered cut-out mode or idling mode.

5. The wind turbine according to claim 1 or 2, wherein, The triggering conditions based on the operating mode include the wind turbine having entered a shutdown mode or a disconnect mode.

6. The wind turbine according to claim 1 or 2, wherein, The triggering conditions based on the operating mode include requirements related to wind speed.

7. The wind turbine according to claim 6, wherein, The wind speed-related requirements include that the measured or estimated wind speed has exceeded a wind speed threshold.

8. The wind turbine according to claim 1 or 2, wherein, The triggering conditions based on the operating mode include one or more requirements related to the operating status of a single rotor nacelle assembly.

9. The wind turbine according to claim 8, wherein, The operating status requirements of the rotor nacelle assembly include one or more of the following: for at least one of the rotor nacelle assemblies, the power output has dropped below a threshold level, the rotor speed has dropped below a threshold level, the rotor has stopped, and the blades have been feathered.

10. The wind turbine according to claim 1 or 2, wherein, The toe angle control system is configured to maintain at least substantially constant toe angle of the rotor nacelle assembly when operating in the first mode.

11. The wind turbine according to claim 1 or 2, wherein, The toe angle control system is configured to maintain a positive toe angle of the rotor nacelle assembly within the range of 2 to 8 degrees when operating in the first mode.

12. The wind turbine according to claim 1 or 2, wherein, The toe angle control system is configured to maintain at least substantially constant toe angle of approximately 0 degrees for the rotor nacelle assembly when operating in the second mode.

13. The wind turbine according to claim 1 or 2, wherein, The toe angle control system is configured to maintain the toe angle of each rotor nacelle assembly less than the minimum toe angle allowed by the toe angle control system when operating in the second mode.

14. The wind turbine according to claim 1 or 2, wherein, The toe angle control system includes at least one data structure that defines a plurality of toe angle reference values ​​and is configured to select a toe angle reference value for each of the rotor nacelle assemblies based on the operating mode of the wind turbine.

15. The wind turbine according to claim 1 or 2, wherein, The wind turbine also includes a central yaw system configured to change the yaw angle of the support relative to the base of the wind turbine.

16. A method of operating a multi-rotor wind turbine, the multi-rotor wind turbine comprising at least two rotor nacelle assemblies mounted on a support device via corresponding yaw systems, the method comprising: The wind turbine is operated in a primary production mode, in which the rotor nacelle assembly is used to generate electricity. When the wind turbine is operating in the main production mode, the rotor nacelle assembly is kept at a positive toe angle, wherein the positive toe angle is formed when the rotor of the rotor nacelle assembly deflects away from the support device in the windward direction; Monitor the operating mode of the wind turbine; as well as When the triggering conditions based on the operating mode are met, the yaw system of the rotor nacelle assembly is activated to reduce the toe angle of the rotor nacelle assembly; The toe angle is defined as the angle in the horizontal plane between the plane containing the rotor of the rotor nacelle assembly and the support device.

17. A non-transitory computer-readable storage medium comprising computer-readable instructions for a computer processor to execute the method of claim 16.

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