Method of operating multi-rotor wind turbine and related system

Abstract

A multi-rotor wind turbine, and a method, a control system and a computer program product for controlling a multi-rotor wind turbine are disclosed. The wind turbine comprises a plurality of energy generating units and may be operated in a full operating state, a partial operating state, or a non-operating state. A cumulative amount of operation of the wind turbine in the partial operating state is determined when the wind turbine is operating in the partial operating state or conditions are suitable to switch operation to the partial operating state. If the cumulative amount of operation in the partial operating state is below the partial operating threshold, the wind turbine is allowed to operate in the partial operating state. If the cumulative amount of operation in the partial operating state is above the partial operating threshold, the wind turbine is constrained not to operate in the partial operating state.

Description

Technical Field

[0001] The present invention relates generally to multi-rotor wind turbines and, more particularly, to a method of minimizing the impact on the operational life of a multi-rotor wind turbine of allowing the multi-rotor wind turbine to operate in a partial operating state. Background Art

[0002] Wind turbines use renewable resources to generate electrical energy without burning fossil fuels. Typically, wind turbines convert kinetic wind energy into mechanical energy, and then convert mechanical energy into electrical energy. A common type of wind turbine is a single-rotor upwind horizontal-axis wind turbine. This type of wind turbine typically includes a tower, a nacelle at the top of the tower, and a single rotor having a central hub and one or more blades (e.g., three blades) mounted on the hub and extending radially from the hub. The rotor is supported by the nacelle and positioned in front of the nacelle so that the rotor faces the upwind direction of its supporting tower. The rotor is operably coupled to a generator housed inside the nacelle and is configured to convert the mechanical energy of the rotor into electrical energy.

[0003] Wind turbine manufacturers continually strive to increase the electricity production (electricity generation) of wind turbines. In this regard, the design of the wind turbine generally plays an important role in the electrical output generated from the wind. For example, the energy obtained from the wind is generally proportional to the swept area of ​​the wind turbine blades. Since the blade tips of longer blades track a larger area than shorter blades, the swept area of ​​the rotor can be increased by using longer wind turbine blades. Therefore, all else being equal, a single-rotor wind turbine with longer blades can extract more energy from a given amount of wind than a single-rotor wind turbine with shorter blades. However, the continued increase in wind turbine blade length has certain practical limitations and presents significant design challenges to wind turbine manufacturers.

[0004] Therefore, as an alternative to increasingly larger single-rotor wind turbines, wind turbine manufacturers have turned their attention to multi-rotor wind turbines. Multi-rotor wind turbines typically combine multiple rotors on a single supporting tower and provide a potential way to increase energy capture and electricity production because the increase in the number of rotors effectively increases the swept area of ​​the wind turbine. It should be recognized that there are different types of multi-rotor wind turbines. For example, one type of multi-rotor wind turbine is a coplanar multi-rotor wind turbine. In a coplanar wind turbine, the multiple rotors are arranged so that the individual wind turbine blades on each rotor are generally located in the same plane. The support structure typically includes a horizontal support arm connected to the tower so that the coplanar rotors are separated enough to operate simultaneously.

[0005] The energy generating units of a multi-rotor wind turbine may sometimes experience different operating conditions, for example due to wind shear, local turbulence from the wake of another wind turbine, fault detection in the rotor nacelle assembly, component wear or failure, or any other reason. These different conditions may require the controller to operate one or more of the energy generating units in a mode different from one or more of the other energy generating units. For example, one of the energy generating units may stop operating while the other energy generating units continue to generate electricity. When only a portion of the energy generating units in a wind turbine are in operation, the wind turbine is said to be in a partially operating state.

[0006] When a wind turbine is in a partially operational state, the thrust generated by different energy generating units may be more unequal than the thrust generated when the wind turbine is in a fully operational state (all energy generating units are producing electricity) or a non-operating state (all energy generating units are not producing electricity). For example, when two energy generating units on opposite sides of a supporting tower are both in operation, the thrust on the energy generating units is generally approximately equal. Similarly, when both energy generating units are in a non-operating state, the thrust on the energy generating units is generally also approximately equal. Under both operating conditions, the thrust from the two energy generating units will largely cancel each other, thereby generating a relatively low yaw moment. In contrast, when one of the two energy generating units is in an operational state and the other is in a non-operating state, the thrust difference between the energy generating units will generally generate a relatively large yaw moment. Therefore, when a wind turbine is operating in a partially operational state, the cumulative thrust generated by the energy generating units tends to be more asymmetric about the tower axis, and therefore tends to generate a larger yaw moment than when the wind turbine is operating in a fully operational state or a non-operating state.

[0007] These unequal thrusts may introduce higher than normal loads in the wind turbine, in particular in the support structure carrying the energy generating unit and the yaw mechanism.

[0008] When operating conditions at one of the energy generating units of a multi-rotor wind turbine necessitate that energy generating unit to be taken out of operation, it is generally preferred that the remaining energy generating units continue to produce electricity. While allowing a wind turbine to operate at a partial operating state may increase the annual power generation of the wind turbine, it may also shorten the operational life of the wind turbine due to the increased load.

[0009] Therefore, wind turbine manufacturers and operators seek improved methods of operating wind turbines in a partial operation state (eg, in a wind park) that minimize the impact of the partial operation on the operational life of the wind turbine. Summary of the invention

[0010] To address these and other disadvantages, in a first aspect of the invention, a method of controlling a wind turbine comprising a plurality of energy generating units is disclosed. The wind turbine is preferably operable in a fully operational state in which all of the plurality of energy generating units are operating, in a partially operational state in which only a subset of the plurality of energy generating units are operating, and in a non-operating state in which none of the plurality of energy generating units are operating. The method comprises determining that the wind turbine is operating in a partially operational state or that conditions are suitable for switching operation to a partially operational state, and determining a cumulative amount of operation of the wind turbine in the partially operational state over a period of time. In response to the cumulative amount of operation in the partially operational state being lower than a partially operational threshold, the method causes the wind turbine to operate in the partially operational state. In response to the cumulative amount of operation in the partially operational state being higher than a partially operational threshold, the method constrains the wind turbine from operating in the partially operational state.

[0011] In one embodiment, the accumulated operating amount may include at least one of: an amount of time, an amount of movement of the wind turbine, an amount of energy generated by the wind turbine, an amount of load on the wind turbine, an amount of fatigue on the wind turbine, an amount of wear on the wind turbine, and an amount of damage to the wind turbine.

[0012] In another embodiment, the amount of movement may include at least one of: a rotation of the yaw mechanism about the tower axis, a rotation of the rotor about the rotation axis, and a rotation of the blade about the pitch axis.

[0013] In another embodiment, determining the accumulated operating quantity may include setting a partial operation flag when the wind turbine is operating in a partial operation state; clearing the partial operation flag when the wind turbine is not operating in a partial operation state; and filtering the partial operation flag to generate the accumulated operating quantity.

[0014] In another embodiment, filtering the partial operation flag may include at least one of: applying a low pass filter to the operation flag or applying a moving average filter to the partial operation flag.

[0015] In another embodiment, the time period may be a moving time window having a set duration and ending at the current moment, or a time window extending from a fixed point in time to the current moment.

[0016] In another embodiment, the accumulated operating quantity may be weighted based on at least one of: an amount of load on the wind turbine, an amount of vibration of a rotor nacelle assembly of the wind turbine, and a wind speed at the wind turbine.

[0017] In another embodiment, the load may include a thrust load, a torque load, or both a thrust load and a torque load acting on a yaw mechanism of the wind turbine.

[0018] In another embodiment, the accumulated operating amount may be a first accumulated operating amount over a first time period, the partial operation threshold may be a first partial operation threshold, and the method may further include determining a second accumulated operating amount of the wind turbine in the partial operation state over a second time period. In this embodiment, in response to the first accumulated operating amount being lower than the first partial operation threshold and the second accumulated operating amount being lower than the second partial operation threshold, the wind turbine may be operated in the partial operation state, and in response to the first accumulated operating amount being higher than the first partial operation threshold or the second accumulated operating amount being higher than the second partial operation threshold, the wind turbine may be constrained from operating in the partial operation state.

[0019] In another embodiment, the plurality of energy generating units may include a left energy generating unit and a right energy generating unit, the first accumulated operating amount may be accumulated only when the wind turbine operates in a partial operating state in which the right energy generating unit is not operating, and the second accumulated operating amount may be accumulated only when the wind turbine operates in a partial operating state in which the left energy generating unit is not operating.

[0020] In another embodiment, the first time period may be coextensive (coincidental, identical) with the second time period.

[0021] In another embodiment, the first time period may be a time window extending from a fixed point in time to the current moment, and the second time period may be a moving time window having a set duration and ending at the current moment.

[0022] In another embodiment, the method may further include reducing or resetting the accumulated operating volume of the wind turbine in response to maintenance being performed on the wind turbine.

[0023] In another embodiment, the method may further include increasing the portion of the operational threshold in response to maintenance being performed on the wind turbine.

[0024] In another embodiment, the method may further include determining a wind speed at the wind turbine, and in response to the wind speed being within the constrained range, constraining the wind turbine from operating in the partial operating state.

[0025] In another aspect of the invention, a control system for controlling a wind turbine including a plurality of energy generating units is disclosed. The system includes one or more processors, and a memory coupled to the one or more processors. The memory includes program code, which, when executed by the one or more processors, causes the control system to: determine that the wind turbine is operating in a partial operating state in which only a subset of the plurality of energy generating units is operating or that conditions are suitable for switching operation to a partial operating state, and determine a cumulative amount of operation of the wind turbine in the partial operating state over a period of time. In response to the cumulative amount of operation in the partial operating state being lower than a partial operating threshold, the program code causes the control system to operate the wind turbine in the partial operating state. In response to the cumulative amount of operation in the partial operating state being higher than the partial operating threshold, the program code causes the control system to constrain the wind turbine from operating in the partial operating state.

[0026] In another aspect of the invention, a wind turbine including a plurality of energy generating units and a control system is disclosed. The control system is configured to determine that the wind turbine is operating in a partial operation state in which only a subset of the plurality of energy generating units is operating or that conditions are suitable for switching operation to the partial operation state, and to determine a cumulative amount of operation of the wind turbine in the partial operation state over a period of time. The control system is further configured to operate the wind turbine in the partial operation state in response to the cumulative amount of operation in the partial operation state being lower than a partial operation threshold, and to constrain the wind turbine from operating in the partial operation state in response to the cumulative amount of operation in the partial operation state being higher than the partial operation threshold.

[0027] In another aspect of the invention, a computer program product for operating a multi-rotor wind turbine having a plurality of energy generating units is disclosed. The computer program product includes a non-transitory computer-readable storage medium and a program code stored on the non-transitory computer-readable storage medium. The program code is configured such that when executed by one or more processors, it causes the one or more processors to determine that the wind turbine is operating in a partial operation state in which only a subset of the plurality of energy generating units is operating or that conditions are suitable for switching operation to a partial operation state, and to determine a cumulative operation amount of the wind turbine in the partial operation state over a period of time. In response to the cumulative operation amount in the partial operation state being lower than a partial operation threshold, the program code causes the one or more processors to operate the wind turbine in the partial operation state. In response to the cumulative operation amount in the partial operation state being higher than the partial operation threshold, the program code causes the one or more processors to constrain the wind turbine from operating in the partial operation state. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the general description of the invention given above and the detailed description given below, serve to explain the invention.

[0029] Figure 1 is a front plan view of a multi-rotor wind turbine;

[0030] Figure 2 is a schematic top view of a wind park with a plurality of multi-rotor wind turbines, wherein the wind is directed from the prevailing wind direction W p issue;

[0031] Figure 3 yes Figure 2 A schematic top plan view of adjacent wind turbines in the wind direction W p The top plan view illustrates a downwind wind turbine located within a critical wake region of an upwind wind turbine operating in a wind emanating from a generally vertical direction, and an energy generating unit of the downwind wind turbine is in a non-electricity generating mode (non-power generating mode);

[0032] Figure 4 yes Figure 3 a schematic top plan view of adjacent wind turbines in FIG. 1 , the top plan view illustrating a downwind wind turbine located within a critical wake region of an upwind wind turbine, and the downwind wind turbine being in a partially operational state;

[0033] Figure 5 is a schematic diagram of a control system that can be used to implement an operation management solution for a multi-rotor wind turbine according to an embodiment of the present invention;

[0034] Figure 6 is another schematic diagram of a control system that can be used to implement an operation management solution for a multi-rotor wind turbine according to another embodiment of the present invention;

[0035] Figure 7 It can be used to implement Figure 5 or Figure 6 A schematic diagram of a controller of a control system;

[0036] Figure 8 is a flow chart of a process for controlling operation of a multi-rotor wind turbine according to an embodiment of the present invention; and

[0037] Fig. 9 It is a depiction Figure 1-4 A graphical view of the power output and thrust of a wind turbine's energy generating unit as a function of wind speed. DETAILED DESCRIPTION

[0038] Figure 1An exemplary multi-rotor wind turbine 20 is depicted, which includes a plurality of energy generating units 22 and a support structure 24 supporting the energy generating units 22. The wind turbine 20 may, for example, be configured as a coplanar multi-rotor wind turbine. However, it should be understood that other multi-rotor arrangements may also benefit from aspects of the present invention. Therefore, the present invention should not be limited to the exemplary embodiments shown and described herein. The support structure 24 includes a tower 26 and a plurality of support arms 28 mounted to the tower 26 for carrying the energy generating units 22. The tower 26 may be coupled to the ground by a foundation 30 at its lower end to define a substantially vertical tower axis 32. The foundation 30 may be a relatively large mass formed of concrete, steel, etc., which transfers the forces acting on the wind turbine 20 to the ground. Alternatively, the foundation 30 may be a pile or other structure located at an offshore location to which the wind turbine 20 is attached. Each support arm 28 has a proximal end adjacent to tower 26 and a distal or terminal end extending generally outwardly from tower 26 to be spaced apart from tower 26. Each support arm 28 may include various beams and / or lattice structures sufficient to accommodate one or more energy generating units 22 a distance from tower 26 and tower axis 32.

[0039] For example, in one embodiment, the support arms 28 may include beams having a circular or other suitable cross-section and may extend outwardly from the tower 26 a distance that depends on the size of the energy generating unit 22. The support arms 28 may be formed of steel or any other suitable material and extend from the tower 26 in a substantially vertical manner or at an angle other than 90 degrees. For example, the support arms 28 may extend in a generally upward direction (as shown), a downward direction, or a forward direction. Each support arm 28 may extend from the tower 26 at substantially the same angle as the other support arms 28, or may extend from the tower 26 at a different angle than one or more of the other support arms 28. One or more cables or guy wires may also be associated with each support arm 28 to provide additional support.

[0040] Each of the support arms 28 may be operably coupled to the tower 26 via a yaw mechanism 34 that allows the support arm 28 and the energy generating unit 22 attached thereto to rotate about the tower axis 32. The yaw mechanism 34 may thereby direct the energy generating unit 22 into the wind. The yaw mechanism 34 may include one or more yaw bearings and one or more yaw actuators (not shown) that enable the support arm 28 to rotate relative to the tower 26 about the tower axis 32. For example, two or more support arms 28 may be coupled to the same yaw mechanism 34, and the wind turbine 20 may include one or more yaw mechanisms 34 distributed vertically along the height of the tower 26.

[0041] The depicted wind turbine 20 includes a lower yaw mechanism 34a and an upper yaw mechanism 34b. The lower yaw mechanism 34a operably couples the left support arm 28a and the right support arm 28b to the tower 26. The corresponding energy generation units 22a, 22b can be coupled to the vicinity of the terminal end of each support arm 28a, 28b. In a similar manner, the upper yaw mechanism 34b operably couples the left support arm 28c and the right support arm 28d to the tower 26, and the corresponding energy generation units 22c, 22d can be coupled to the vicinity of the terminal end of each support arm 28c, 28d. Therefore, the exemplary multi-rotor wind turbine 20 includes four energy generation units 22a, 22b, 22c, 22d supported on the same tower 26. However, it should be understood that embodiments of the present invention are not limited to this arrangement, and multi-rotor wind turbines 20 having other configurations and numbers of energy generation units 22 can also be operated using any operation management scheme disclosed herein.

[0042] The energy generation unit 22 refers to the portion of the wind turbine 20 that converts wind energy into electrical energy, and each support arm 28 can be configured to carry at least one energy generation unit 22 at a substantially fixed distance from the tower 26. Each energy generation unit 22 generally includes a rotor 36, a nacelle 38, and a generator (not shown). The rotor 36 may include a central hub 40 and one or more blades 42 (e.g., three blades) extending radially from the hub 40. The generator is operably coupled to the hub 40, such as by a transmission system including a gear device interconnecting the rotor 36 and the generator. A large portion of the generator and the transmission system can be located within the nacelle 38. Although the energy generation unit 22 is depicted as being located near the terminal end of each support arm 28, it should be appreciated that the energy generation unit 22 can be located at other locations along the support arm 28, and each support arm 28 can carry more than one energy generation unit 22. The arrangement of the energy generation units 22 on the tower 26 is configured to prevent the blades 42 of adjacent rotors 36 from contacting each other during operation. Therefore, the energy generating units 22 are sufficiently spaced apart from each other to avoid such contact. The wind turbine blades 42 are configured to interact with the free stream airflow (wind) to generate lift that causes the rotor 36 to turn or rotate generally within a plane defined by the wind turbine blades 42. Thus, the energy generating units 22 are able to generate electricity from the airflow through the swept area 44 of each rotor 36.

[0043] According to exemplary operating scenarios, wind turbine 20 may be operated in a partial operating state. Figure 2 A plurality of multi-rotor wind turbines 20 are depicted arranged in a multi-dimensional array that defines an exemplary wind park 50. The rows R1-R3 of wind turbines 20 may be oriented so that they are substantially perpendicular to the prevailing wind W at the wind park 50. pThe multi-dimensional array includes a spacing S1 between wind turbines 20 in the same row that prevents contact between rotors 36 of adjacent wind turbines 20, and a spacing S2 between rows that is sufficient to allow the wake region to be passively dissipated before the airflow of the dominant wind strikes the downwind wind turbines 20. In other words, the spacing S2 between wind turbines 20 in adjacent rows R1-R3 may be a distance greater than the length of a critical wake region of the wind turbines 20.

[0044] Under certain conditions, wind turbine 20 may be placed in a non-operating state. Figure 3 An exemplary situation is depicted when the rotor 36 of the downwind wind turbine 20b is in the critical wake region 52 of the upwind wind turbine 20a, for example due to the wind W from a direction other than the prevailing wind direction W. p This may happen when the wind is blowing from a direction other than the wind direction. In the non-operating state, all energy generating units 22 of the wind turbine 20 are placed in a non-electricity generating mode (i.e., stopped operating), as represented by each X. The non-electricity generating mode may include, but is not limited to, an idle mode, a stop mode, a motor mode, etc.

[0045] Figure 4 Depicted Figure 3 , wherein the wind W is offset such that only one of the rotors 36 of the downwind wind turbine 20b is located in the critical wake region 52 of the upwind wind turbine 20a. Under these exemplary operating conditions, the downwind wind turbine 20b may be placed in a partially operational state. In the partially operational state, the energy generating units 22 of the wind turbines 20b within the critical wake region 52 have been placed in a non-power generating mode (i.e., stopped operating), while the energy generating units 22 of the downwind wind turbines 20b that are not located within the critical wake region 52 are still in a power generating mode (e.g., still in operation). The power generating mode may include a normal operating mode, a derated operating mode, or any other mode in which the energy generating units generate power.

[0046] It should be appreciated that wind turbine 20 may be placed in a partial operation state for reasons other than one of energy generating units 22 being in a critical wake region. For example, wind turbine 20 may be placed in a partial operation state in response to detecting a fault condition (e.g., component failure, rotor imbalance, blade pitch error, etc.) in a subset (i.e., at least one but not all) of energy generating units 22 that requires those units to be placed in a non-electrical power generating mode. Partial operation may also occur during maintenance activities that affect only a subset of energy generating units 22 of wind turbine 20, or due to any other condition or reason that requires some but not all of energy generating units 22 of wind turbine 20 to be placed in a non-electrical power generating mode. Thus, aspects of the present invention are not limited to the specific scenarios depicted in the figures, but are generally applicable to a variety of situations in which operation of a wind turbine in a partial operation state may occur.

[0047] Figure 5 An exemplary embodiment of a control system 60 is illustrated for operating one or more wind turbines 20 of a wind park 50 according to the above-described operation management scheme. In the depicted embodiment, the control system 60 may follow a distributed control model that is implemented on each of a plurality of wind turbines 20 in the wind park 50. The control system 60 includes a plurality of wind turbine controllers 62 (one shown), each wind turbine controller 62 being associated with a respective wind turbine 20 of the wind park 50. The wind turbine controller 62 may be configured to implement a control strategy for the wind turbine 20 that may optimize the performance of the wind turbine 20, for example, maximizing the energy production of the wind turbine 20. The wind turbine controller 62 may be configured to control the operation of the wind turbine 20 associated therewith and communicate with the yaw mechanism 34 and the energy generation unit 22 of the wind turbine 20.

[0048] The control system 60 may include one or more sensors 54 that communicate with the wind turbine controller 62 to facilitate monitoring and / or operation of the wind turbine 20. For example, the one or more sensors 54 may include one or more wind sensors for determining information about the oncoming wind, such as wind direction, wind speed, turbulence level, etc. In addition, the one or more sensors 54 may include one or more position sensors for determining, for example, the yaw position of the rotor 36 of the energy generating unit 22 of the wind turbine 20. In addition, the one or more sensors 54 may include a large number of other sensors, such as pressure sensors, temperature sensors, load sensors, stress sensors, strain sensors, vibration sensors, or other sensors, each of which is operably coupled to the wind turbine controller 62 to facilitate the operation of the wind turbine 20 and the implementation of one or more operation management schemes. Such sensors 54 and methods of processing signals generated by the sensors 54 to determine the amount of load, fatigue, wear, or damage to the wind turbine 20 or its components are well known in the wind turbine industry. Therefore, for the sake of brevity, further description of the one or more sensors 54 or methods of processing the signals generated thereby is not provided herein.

[0049] Figure 6 Another exemplary embodiment of a control system 60 is illustrated, which is used to operate the wind turbines 20 of the wind park 50 according to any of the above-mentioned operation management schemes. In this embodiment, the control system 60 can be a centralized control model and implemented at the wind park level rather than on a single wind turbine 20. In this centralized model, the control system 60 includes a wind park supervisory controller 64 that communicates with each of a plurality of wind turbine controllers 62. The supervisory controller 64 can be configured to implement a system-wide control strategy for the plurality of wind turbines 20 that make up the wind park 50, thereby optimizing the collective performance of the wind park 50.

[0050] As described above, the wind turbine controller 62 is configured to control the operation of the wind turbine 20 associated therewith and to communicate with the yaw mechanism 34 and the energy generation unit 22 associated with the wind turbine 20. The control system 60 may also include one or more additional sensors 56 in communication with the supervisory controller 64, which facilitate the operation of the wind turbines 20 of the wind park 50 and the implementation of the operation management scheme at the wind park level. For example, the one or more sensors 56 may provide data related to the conditions of the wind park 50 as a whole (rather than individual wind turbines 20). For example, the one or more sensors 56 may include one or more wind sensors for determining information about the oncoming wind, such as wind direction, wind speed, turbulence level, etc. In this embodiment, for example, the one or more sensors 56 may be separate from the plurality of wind turbines 20 that make up the wind park 50 and communicate directly with the supervisory controller 64.

[0051] Figure 7 An exemplary controller 66 is illustrated that can be used to provide one or more components of the control system 60, such as the wind turbine controller 62 and the supervisory controller 64. The controller 66 includes a processor 68, a memory 70, and an input / output (I / O) interface 72. The processor 68 may include one or more devices that perform operations on data based on internal logic or operating instructions stored in the memory 70. The memory 70 may include a single memory device or multiple memory devices capable of storing data. Computer program code embodied as one or more computer software applications, such as the application 74 residing in the memory 70, may have instructions executed by the processor 68. One or more data structures 76 may also reside in the memory 70 and may be used by the processor 68 or the application 74 to store or manipulate data. The I / O interface 72 may provide a machine interface that operably couples the processor 68 to other devices and systems, such as the sensors 54, 56, the supervisory controller 62, the wind turbine controller 64, the yaw mechanism 34, and the energy generation unit 22. Thus, the application 74 may work in conjunction with external devices and systems by communicating via the I / O interface 74 to provide the various features, functions, applications, processes or modules that make up an embodiment of the present invention.

[0052] When wind acts on the rotor 36 of the energy generation unit 22, the rotor 36 applies thrust to the energy generation unit 22 as it rotates. This thrust causes force to be transmitted to the support structure 24 of the wind turbine 20 through the energy generation unit 22. For a multi-rotor wind turbine, the rotor thrust of each energy generation unit 22 may be different. The difference in the force applied to the support structure 24 by different energy generation units 22 may be caused by different wind conditions (for example, due to wind shear) or differences in the operating mode of the energy generation unit 22. Specifically, the amount of thrust applied by the rotor 36 to the energy generation unit 22 may vary depending on the amount of electricity generated by the energy generation unit 22. Therefore, on the same wind turbine 20, operating some energy generation units 22 in an electricity generation mode and operating other energy generation units 22 in a non-electricity generation mode will result in relatively large differences between the forces applied to the support structure 24 by different energy generation units 22.

[0053] Since the energy generating units 22 on the same wind turbine 20 can be operated in both a power production mode and a non-power production mode when the wind turbine is in a partially operational state, the wind turbine 20 may be subject to higher force imbalances than normal in a fully operational or non-operating state. Counteracting these force imbalances between the different energy generating units 22 may subject the support structure 24 to higher than normal loads. These higher than normal loads may in turn cause accelerated wear and fatigue of various components of the support structure 24, such as the tower 26, the support arm 28, and the yaw mechanism 34.

[0054] Therefore, it may be desirable to implement strategies to mitigate the effects of these higher than normal loads in a multi-rotor wind turbine 20 operating in a partial operating state. These strategies can reduce wear or damage caused by load cycling (i.e., fatigue) and overload (i.e., failure). One such strategy is to limit the amount of time that the wind turbine 20 is allowed to operate in a partial operating state to a portion of the operating period, such as a predetermined percentage of a year. This type of limitation can be implemented by, for example, tracking the time the wind turbine spends in a partial operating state. Limitation of operation in a partial operating state can also be implemented by tracking the movement, generated energy or load, fatigue, wear, vibration, or damage of the wind turbine 20 or its components. In response to the tracked parameter exceeding the partial operating threshold, the wind turbine can be prohibited from further operation in the partial operating state.

[0055] Figure 8A flow chart of a process 80 for controlling a multi-rotor wind turbine 20 is depicted, which process 80 may be implemented to operate the wind turbine 20 according to the general operating principles described above. The process 80 may be performed by one or more of the wind turbine controller 62, the supervisory controller 64, or any other suitable computing device. Although the cumulative operating quantities are described primarily in terms of cumulative time quantities below, it should be understood that other operating parameters may be accumulated to generate the cumulative operating quantities. These operating parameters may include one or more of the following: an amount of motion of the wind turbine 20 (e.g., rotation of the yaw mechanism 34 about the tower axis 32, rotation of the rotor 36 about its rotation axis, rotation of the blades 42 about the pitch axis, etc.), an amount of energy generated by the wind turbine 20, or an amount of load, fatigue, wear, vibration, or damage to the wind turbine 20 or its components.

[0056] In block 82, process 80 may determine whether partial operation of the wind turbine is indicated. For example, partial operation may be indicated if the rotor 36 of at least one energy generating unit 22 of the wind turbine 20 is located within the critical wake region 52 of another energy generating unit 22, and the rotor 36 of at least one other energy generating unit 22 of the wind turbine 20 is not within the critical wake region 52 of any energy generating unit 22. Other examples of indicating partial operation may include detection of a fault condition, a maintenance window, or any other condition that causes a subset of the energy generating units 22 to be placed in a non-electrical power generating mode.

[0057] If partial operation is not indicated ("No" branch of decision block 82), process 80 may proceed to block 84 and cause wind turbine 20 to enter a non-partial operation state, such as a fully operational state (if all energy generating units 22 are not placed in a non-electrical power generation mode) or a non-operational state (if all energy generating units 22 are placed in a non-electrical power generation mode). Process 80 may also disable accumulator functionality, as described in more detail below.

[0058] If partial operation is indicated (the "yes" branch of decision block 84), the process 80 may proceed to block 86 and determine the cumulative amount of operation of the wind turbine 20 in the partial operation state. The cumulative amount of operation may be determined, for example, by accumulating the amount of time that the wind turbine 20 has been operating in the partial operation state over a previous time period. The previous time period may be, for example, a moving time window having a set duration (e.g., one year) and ending at the current time. As another example, the previous time period may extend from a fixed point in time (e.g., when the wind turbine 20 was placed in service or last serviced) to the current time. The time period extending from the time the wind turbine 20 was placed in service to the current time may be referred to as the useful life of the wind turbine 20.

[0059] In any case, the process 80 may determine the accumulated operating quantities of the wind turbine 20 in the partial operating state, for example, by starting an accumulator function each time the partial operating flag is set and stopping the accumulator function each time the partial operating flag is cleared. The partial operating flag may be set each time the wind turbine 20 enters the partial operating state, and the partial operating flag may be cleared each time the wind turbine exits the partial operating state. The values ​​accumulated by the accumulator function while the wind turbine 20 is in the partial operating state may include an amount of time, an amount of motion, an amount of energy generated, an amount of load, an amount of fatigue, an amount of wear, an amount of vibration, or an amount of damage.

[0060] The accumulator function may include, for example, a timer that counts up when the accumulator function is enabled and stops counting when the accumulator function is disabled, such that the value provided by the timer is equal to the total amount of time that the accumulator function is enabled. In an alternative embodiment, the accumulator function may record the operating state of the wind turbine 20 (e.g., a fully operational state, a partially operational state, and a non-operating state) over time and then sum the time in one or more of these states over a period of time.

[0061] Time may be accumulated as "actual time" or "weighted time" by the accumulator function. Actual time refers to the unweighted time that the wind turbine operates in the state in question, e.g., one second of time is accumulated for each second that the wind turbine operates in a partial operating state. In contrast, weighted time refers to the sum of the time that the wind turbine operates in the state in question multiplied by a weighting factor that varies over time. For example, under conditions that have been determined to cause twice the normal amount of wear, two seconds may be accumulated for each second that the wind turbine operates in a partial operating state under these conditions. For example, the weighting factor may be determined based on sensor signals indicating loads, stresses, or strains on one or more components of the wind turbine 20. The weighting factor may also be based on an amount of load, stress, or strain on one or more components of the wind turbine 20 estimated based on operating conditions of the wind turbine 20 (e.g., wind speed, amount of power generated, pitch setting, yaw setting, etc.). The weighting factor value may be determined empirically based on historical data collected from field wind turbines, based on simulations, or by any other suitable method. Thus, the weighting factors may be used to generate a cumulative operating quantity that reflects a cumulative amount of load, fatigue, wear, or damage to wind turbine 20 or a component thereof.

[0062] The weighting factor may also be determined based on an amount of vibration (e.g., bending and / or torsional vibration) in the tower 24, the yaw mechanism 34, the rotor 36, the nacelle 38, the rotor 36 and the nacelle 38 as an assembly (a rotor and nacelle assembly), or any other component of the wind turbine 20. Specifically, an amount of torsional vibration experienced by the yaw mechanism 34 may be determined and a weighting factor generated based thereon.

[0063] In an alternative embodiment, the process 80 may determine the cumulative operating amount of the wind turbine 20 in the partial operating state by filtering the output of the partial operating flag (e.g., through a low pass filter). The filter may be configured to have a time response so that the rise time of the filter output corresponds to the cumulative operating amount exceeding the partial operating threshold. In a manner similar to the accumulator-based determination described above, the output of the partial operating flag may be weighted. Such weighting of the filter input may increase or decrease the time required for the filter output to reach a level indicating a particular cumulative operating amount.

[0064] In block 88, process 80 may compare the accumulated operating amount to a partial operating threshold. The partial operating threshold may define a limit on the total amount of time (weighted or unweighted) that wind turbine 20 is allowed to operate in a partial operating state. The partial operating threshold may define a maximum value allowed in terms of total time (e.g., 2500 hours / year or a 20,000 hour lifetime limit), a maximum percentage of time that wind turbine 20 may operate in a partial operating state over a moving time period using a moving average window (25% of the previous year), or any other suitable threshold for determining whether wind turbine 20 is currently allowed to operate in a partial operating state based on the accumulated operating amount in the partial operating state. In the case of a moving average window, operating data for a time period (e.g., the previous 12 months) may be stored and moving averages of different time windows within the time period may be compared. Data used to determine the accumulated operating amount may be stored using non-volatile memory to avoid loss of such data due to power outages.

[0065] In response to the cumulative operating amount exceeding the partial operating threshold (the "yes" branch of decision block 88), process 80 may proceed to block 90. ​​In block 90, process 80 may cause wind turbine 20 to enter a non-operating state and disable the accumulator function if there is an enabled accumulator function. Process 80 may then return to block 82.

[0066] In response to the cumulative operating amount not exceeding the partial operating threshold (the "No" branch of decision block 88), process 80 may proceed to block 92. In block 92, process 80 may cause wind turbine 20 to enter a partial operating state and, if process 80 includes an accumulator function in a disabled state, enable the accumulation function. Then, process 80 may return to block 82.

[0067] Fig. 9 A graph 100 is depicted, which includes an exemplary graph 102 of the relationship between the output power of the energy generation unit 22 and the wind speed, or "power curve", and an exemplary graph 104 of the relationship between the thrust load and the wind speed, or "thrust curve". MIN, the energy generation unit 22 may be in an idle mode during which the rotor 36 does not rotate or rotates only slowly. MIN When the wind speed decreases from the cut-in wind speed W, the rotor 36 of the energy generation unit 22 may begin to rotate, thereby allowing the energy generation unit 22 to begin generating electricity. MIN Further increase to the rated wind speed W R When the cut-in wind speed W is , the blade pitch can be set to maximize the conversion of aerodynamic energy to rotational energy at the energy generating unit 22. MIN and rated wind speed W R The power output of the energy generation unit 22 can increase as the wind speed increases. Once the rated wind speed W is reached R , the energy generation unit 22 can generate electricity at its maximum rated output power. From this point on, as the wind speed increases further, the blade pitch can be adjusted to maintain the speed and torque applied to the energy generation unit 22 at the rated output power. Finally, when the wind speed reaches the cut-out wind speed W C When the blades 42 are feathered, the output power of the energy generation unit 22 can be reduced to zero to prevent damage to the wind turbine 20. As shown in the thrust curve, the thrust load T generated by the energy generation unit 22 L As the wind speed increases from the cut-in wind speed to a certain point (such as the rated wind speed W R ) tends to increase, and tends to decrease as the wind speed increases from the peak thrust load wind speed to the cut-out wind speed. Therefore, the thrust load T L It may be highest at a certain wind speed, such as at rated wind speed W R In the nearby area.

[0068] Reference again Figure 1 , and continue to refer to Fig. 9 Due to the lateral separation between the energy generating units 22 on the support arms 28 extending from opposite sides of the tower 26, for a partially operational wind turbine 20, the number of energy generating units 22 operating on certain support arms (e.g., support arms 28a, 28c) may be different from the number of energy generating units 22 operating on other support arms (e.g., support arms 28b, 28d). For example, this is Figure 4 Therefore, the thrust load T acting on the support structure 24 of the wind turbine 20 is L ( Figure 4 The arrow A1 in the middle indicates that the thrust load may be unbalanced. This unbalanced thrust load may cause the torque load M L (indicated by arrow A2) acts on the tower 26 about the tower axis 32. L The imbalance and the resulting torque load M Lmust be accommodated by the yaw mechanism 34 associated with the support structure 24. It will be appreciated that if the thrust / torque generated by some operating conditions of the wind turbine 20 becomes too high, the yaw mechanism 34 of the wind turbine 20 may be damaged. To avoid excessive torque loads on the yaw mechanism 34 of the wind turbine 20, for conditions generating thrust / torque greater than T MAX The wind speed at which the thrust load is greater than the wind speed at which the wind turbine 20 is not operated in a partial operation state. Fig. 9 The exemplary energy generating unit 22 represented by the graph 100 of FIG. 1 may reduce a portion of its operating state in a constrained wind speed region 106 between W1 and W2 .

[0069] In one embodiment of the present invention, the curtailment of the partial operation state may include prohibiting the wind turbine 20 from entering the partial operation state at any time when the wind speed is within the constrained wind speed region 106. In an alternative embodiment, the curtailment of the partial operation state may prohibit the wind turbine 20 from entering the partial operation state only when the wind speed is within the constrained wind speed region 106 and the cumulative operation amount is above a lower partial operation threshold. In this embodiment, when the wind speed is outside the constrained wind speed region 106, partial operation will be allowed when the cumulative operation amount is above the lower partial operation threshold but below the upper partial operation threshold, and partial operation will be prohibited at all wind speeds when the cumulative operation amount is above the upper partial operation threshold. That is, above the upper partial operation threshold, the wind turbine 20 will be constrained from operating in the partial operation state regardless of the wind speed.

[0070] Operating wind turbine 20 within the constrained wind speed range may be determined based on a direct measurement of wind speed at wind turbine 20 or energy generating unit 22, or operation within the constrained range may be inferred based on one or more other measured parameters (e.g., estimated or measured thrust, pitch angle, power output, rotor speed, generator speed, etc.).

[0071] For example, if certain characteristics of the oncoming wind are known and the geometry of the energy generation unit 22 is known, the thrust load T of the energy generation unit 22 can be estimated. L。 For example, in one embodiment, the thrust load T of the energy generation unit 22 in the normal operation mode may be estimated according to the following formula: L :

[0072]

[0073] Where ρ is the air density, S w is the wind speed, C t is the thrust coefficient (which is a function of the tip speed ratio λ and the pitch angle θ), and D ris the rotor diameter. The wind turbine 20 and / or the energy generation unit 22 may include various sensors, including blade root bending moment sensors, pitch position sensors, rotor speed sensors (e.g., for blade tip speed ratio λ), and various temperature, pressure, and / or humidity sensors for determining the air density ρ. Therefore, if this information is known, the thrust load T of the energy generation unit 22 can be estimated. L。 Much like determining the wind direction W, one or more sensors 54, 56 associated with the control systems 62, 64 may be configured to provide this information. Thus, in this embodiment, the thrust load T on one or more yaw mechanisms 34a, 34b of the wind turbine 20 may be estimated based on measurements from the one or more sensors 54, 56. L and / or torque load M L .

[0074] The thrust load T on the one or more yaw mechanisms 34a, 34b of the wind turbine 20 L and / or torque load M L It can also be determined by active measurement. In this regard, the one or more sensors 54, 56 of the controllers 62, 64 may include various sensors operably coupled to the yaw mechanisms 34a, 34b for measuring loads. For example, the one or more sensors 56 may include strain gauges, pressure sensors, displacement sensors, or other sensors for indicating thrust loads and / or torque loads. Based on the measurements from these sensors 54, 56, the thrust load T can be determined. L and / or torque load M L Whether it exceeds the predetermined load threshold L T These measurements can also be used to weight the parameters being accumulated to produce a running cumulative volume.

[0075] Allowing the wind turbines 20 of a wind park 50 to operate in a partial operating state can reduce the loss of power production caused by the need to shut down the entire wind turbine each time any energy generating unit 22 encounters a problem, thereby increasing the total power generation of the wind turbines 20 and the annual power generation of the wind park 50. By allowing the wind turbines 20 of a wind park 50 to operate in a partial operating state, care must be taken to ensure that the partial operation does not cause premature wear or damage, thereby erasing any economic benefits of the increased power generation. Controlling the amount of operation of the wind turbines 20 in the partial operating state can allow the annual power generation of the wind turbines 20 (and the wind park 50) to be increased without unnecessarily risking a shortened useful life of the wind turbines 20.

[0076] Although the present invention has been illustrated by the description of various preferred embodiments, and these embodiments have been described in considerable detail, the applicant does not intend to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will be readily apparent to those skilled in the art. Therefore, the various features of the present invention may be used alone or in any combination, depending on the needs and preferences of the user.

Claims

1. A method of controlling a wind turbine comprising a plurality of energy generating units, the wind turbine being operable in a fully operational state in which all of the plurality of energy generating units are in operation, a partially operational state in which only a subset of the plurality of energy generating units are in operation, and a non-operational state in which none of the plurality of energy generating units are in operation, the method comprising: determining that the wind turbine is operating in a partial operation state or that conditions are suitable for switching operation to a partial operation state; Determining the cumulative amount of wind turbine operation in a partial operation state over a period of time; In response to the accumulated operation amount in the partial operation state being lower than a partial operation threshold, operating the wind turbine in the partial operation state, and In response to the accumulated operation amount in the partial operation state being greater than a partial operation threshold, the wind turbine is constrained from operating in the partial operation state.

2. The method according to claim 1, wherein: The accumulated operation amount includes at least one of an amount of time, an amount of movement of the wind turbine, an amount of energy generated by the wind turbine, an amount of load on the wind turbine, an amount of fatigue on the wind turbine, an amount of wear on the wind turbine, and an amount of damage to the wind turbine.

3. The method according to claim 2, wherein: The movement amount includes at least one of the following: rotation of the yaw mechanism around the tower axis, rotation of the rotor around the rotation axis, and rotation of the blade around the pitch axis.

4. The method according to any one of claims 1 to 3, wherein: Determining the cumulative running volume includes: When the wind turbine is operated in a partial operation state, a partial operation flag is set; clearing the partial operation flag when the wind turbine is not operating in the partial operation state; and The partial run flags are filtered to generate the cumulative run amount.

5. The method according to claim 4, wherein: Filtering the partial operation flag includes at least one of: applying a low pass filter to the operation flag or applying a moving average filter to the partial operation flag.

6. The method according to any one of claims 1 to 5, wherein: The time period is either a moving time window having a set duration and ending at the current moment, or a time window extending from a fixed point in time to the current moment.

7. The method according to any one of claims 1 to 6, wherein: The accumulated operating quantity is weighted based on at least one of: an amount of load on the wind turbine, an amount of vibration of a rotor nacelle assembly of the wind turbine, an amount of vibration of a tower of the wind turbine, and a wind speed at the wind turbine.

8. The method according to claim 7, wherein: The loads include thrust loads, torque loads, or both thrust loads and torque loads acting on a yaw mechanism of the wind turbine.

9. The method according to any one of claims 1 to 8, wherein: The cumulative running amount is a first cumulative running amount in a first time period, the partial running threshold is a first partial running threshold, and the method further includes: A second accumulated operation amount of the wind turbine in the partial operation state during a second time period is determined, wherein: In response to the first accumulated operating quantity being below the first partial operation threshold and the second accumulated operating quantity being below a second partial operation threshold, operating the wind turbine in a partial operation state, and In response to the first accumulated operating quantity being greater than the first partial operation threshold or the second accumulated operating quantity being greater than the second partial operation threshold, the wind turbine is constrained from operating in a partial operation state.

10. The method according to claim 9, wherein: The plurality of energy generation units include a left energy generation unit and a right energy generation unit, the first accumulated operating amount is accumulated only when the wind turbine operates in a partial operating state in which the right energy generation unit is not operating, and the second accumulated operating amount is accumulated only when the wind turbine operates in a partial operating state in which the left energy generation unit is not operating.

11. The method according to claim 9 or 10, wherein: The first time period is coextensive with the second time period.

12. The method according to claim 9 or 10, wherein: The first time period is a time window extending from a fixed time point to the current moment, and the second time period is a moving time window having a set duration and ending at the current moment.

13. The method according to any one of claims 1 to 12, further comprising: The accumulated operating volume of the wind turbine is reduced or reset in response to maintenance being performed on the wind turbine.

14. The method according to any one of claims 1 to 13, further comprising: The partial operation threshold is increased in response to maintenance being performed on the wind turbine.

15. The method according to any one of claims 1 to 14, further comprising: Determine wind speed at wind turbines; as well as In response to the wind speed being within the constrained range, the wind turbine is constrained from operating in the partial operation state.

16. A control system for controlling a wind turbine comprising a plurality of energy generating units, the control system comprising: one or more processors; as well as a memory coupled to the one or more processors and comprising program code that, when executed by the one or more processors, causes the control system to: determining that the wind turbine is operating in a partial operating state in which only a subset of the plurality of energy generating units are operating or that conditions are suitable to switch operation to the partial operating state; Determining the cumulative amount of wind turbine operation in a partial operation state over a period of time; In response to the accumulated operation amount in the partial operation state being lower than the partial operation threshold, operating the wind turbine in the partial operation state, and In response to the accumulated operation amount in the partial operation state being greater than a partial operation threshold, the wind turbine is constrained from operating in the partial operation state.

17. A wind turbine comprising: a plurality of energy generation units; as well as A control system configured to: determining that the wind turbine is operating in a partial operating state in which only a subset of the plurality of energy generating units are operating or that conditions are suitable to switch operation to the partial operating state; Determining the cumulative amount of wind turbine operation in a partial operation state over a period of time; In response to the accumulated operation amount in the partial operation state being lower than the partial operation threshold, operating the wind turbine in the partial operation state, and In response to the accumulated operation amount in the partial operation state being greater than a partial operation threshold, the wind turbine is constrained from operating in the partial operation state.

18. A computer program product for controlling a wind turbine comprising a plurality of energy generating units, the computer program product comprising: a non-transitory computer-readable storage medium; as well as The program code stored on the non-transitory computer readable storage medium, when executed by one or more processors, causes the one or more processors to: determining that the wind turbine is operating in a partial operating state in which only a subset of the plurality of energy generating units are operating or that conditions are suitable to switch operation to the partial operating state; Determining the cumulative amount of wind turbine operation in a partial operation state over a period of time; In response to the accumulated operation amount in the partial operation state being lower than the partial operation threshold, operating the wind turbine in the partial operation state, and In response to the accumulated operation amount in the partial operation state being greater than a partial operation threshold, the wind turbine is constrained from operating in the partial operation state.

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