A method and system for suppressing the flutter of a wind turbine blade based on piezoelectric drive

Abstract

The present invention relates to the technical field of wind turbines, and specifically relates to a method and system for suppressing the flutter of wind turbine blades based on piezoelectric drive, which includes: obtaining the characteristic deformation amounts at multiple sites in the length direction of the blade, where the characteristic deformation amount refers to the deformation displacement magnitude of the blade surface in its vertical direction; calculating at least one characteristic frequency from the deformation displacement, and the at least one characteristic frequency includes one or more of the following: the first-order flap vibration mode frequency, the first-order flutter mode frequency, and the first-order torsion mode frequency; using a first adjustment rule to output a set of adjustment signals for at least one rigid adjustment unit through a rigid adjustment model, and the set of adjustment signals includes: at least one input voltage; the rigid adjustment unit includes: two support plates and a piezoelectric ceramic, and both ends of the piezoelectric ceramic are respectively arranged in the hole positions of the two support plates. The present invention can simplify the blade design structure and reduce the suppression cost.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbines, and particularly to a method and system for suppressing blade flutter of a wind turbine based on piezoelectric drive. Background Art

[0002] In the operation of actual wind farms, it is found that, especially after extreme weather such as typhoons, the flexible blades have varying degrees of structural damage caused by blade flutter. The damage of a single flexible blade may result in an economic loss of up to millions of yuan. Generally, the classical flutter of a wind turbine is a self-excited vibration of the coupling of the structure and the air flow at a certain specific wind speed and angle of attack. The deformation caused by the coupling of the flapping motion, the pitching motion and the torsional motion occurs. At the same time, the aerodynamic drag continuously decreases with the increase of the wind speed until it becomes negative, the drive system diverges, and the structure is damaged.

[0003] For the existing wind turbine blades to solve the flutter problem, the following main methods are adopted:

[0004] I. Avoiding the critical wind speed

[0005] The main method is to avoid the critical wind speed of flutter in the design. Generally, during the design, the critical wind speed of stall flutter of the wind turbine blade is determined. Once the speed exceeds this value during operation, the blades are feathered and the machine is shut down to take protective measures.

[0006] For example, the patent application CN113945357A discloses a method and device for predicting the critical wind speed of flutter of a wind turbine blade. This method can predict the critical wind speed of flutter of a wind turbine blade through the measured force data of a wind tunnel test. However, the above method only has a good effect on stall flutter, and lacks effective active control means for classical flutter.

[0007] II. Using hydraulic control to change the blade mass distribution

[0008] For example, the patent application CN116822308A discloses a method for constructing a flutter suppression pipe network for a hundred-meter-class wind turbine blade based on the bionic principle. This method changes the blade mass distribution through the liquid circulation in the bionic pipe network, and then changes the natural frequency of the blade to make the natural frequency deviate from the flutter frequency of the blade. However, this mass distribution adjustment scheme is very complex in the pipeline structure design, which will greatly increase the blade structure design difficulty and production cost. Moreover, the real-time control of the change of its blade mass distribution also has very high requirements for the performance of the computer system. Therefore, this scheme for changing the blade mass distribution is extremely difficult to implement in the actual application process.

[0009] III. Using piezoelectric materials to suppress flutter

[0010] The existing technical path 1 is: using piezoelectric materials to control the change in the rotation angle of the blade. For example, patent application CN107559154A discloses an intelligent pitch system for suppressing the flap flutter of a wind turbine based on piezoelectric feedback. Its working mechanism is that when the blade undergoes flap flutter, the pitch mechanism causes the angle of the wind turbine blade to change. However, this control angle change scheme will result in a loss of power generation.

[0011] The existing technical path 2 is: converting mechanical energy into electrical energy through piezoelectric power generation to reduce the deformation of the blade. For example, CN105804944A discloses a dual-generation intelligent adaptive vibration damping wind turbine, whose actuator is a hyperbolic damping piezoelectric generator. Its working mechanism is that when the blade deforms, the deformation of the hyperbolic damping piezoelectric generator converts mechanical energy into electrical energy through piezoelectric power generation to reduce the deformation of the blade. However, the size of the actuator required for this energy conversion scheme is necessarily large, which is likely to occupy the position of the structural beam of the wind turbine blade, and is not conducive to the blade structure design.

[0012] The existing technical path 3 is: using piezoelectric materials to apply a force in the direction opposite to the flutter direction. For example, CN202431443U discloses an active vibration control system for wind turbine blades, and its control principle is to apply a force in the direction opposite to the deformation direction of the blade. However, in fact, when the blade deforms, its deformation is periodic. And the blade deformation is highly correlated with the rotation period of the blade, which requires the actuator to be able to generate a periodic force, making it difficult to measure and test. Even more, once the period of the force is not cancelled but coupled, it is very likely to amplify the flutter.

[0013] Therefore, there is an urgent need for a flutter suppression scheme with a simple structure, precise control and low application cost. Summary of the Invention

[0014] The purpose of the present invention is to provide a method and system for suppressing the flutter of wind turbine blades based on piezoelectric drive, which can partially solve or alleviate the above deficiencies in the prior art, simplify the blade design structure and reduce the suppression cost.

[0015] In order to solve the above-mentioned technical problems, the present invention specifically adopts the following technical solutions:

[0016] In a first aspect of the present invention, there is provided a method for suppressing flutter of a wind turbine blade based on piezoelectric drive. A plurality of rigid adjustment units are distributed along the length direction of the blade. The rigid adjustment unit includes: at least two support plates and piezoelectric ceramics. The at least two support plates are spaced apart along the length direction, and the sides of the at least two support plates are connected to the blade. At least one hole position is respectively arranged on the support plates, and both ends of the piezoelectric ceramics are respectively arranged in the corresponding hole positions. When the length of the piezoelectric ceramics changes, the length of the rigid adjustment unit also changes accordingly, so as to be able to change the inherent rigidity of the blade. Among them, at least one of the rigid adjustment units is arranged adjacent to the tip of the blade, and at least one of the rigid adjustment units is arranged adjacent to the root of the blade. Correspondingly, the method includes the steps:

[0017] S101 Obtain the characteristic deformation amounts at a plurality of positions of the blade in the length direction. The characteristic deformation amount refers to the deformation displacement size of the blade surface in the vertical direction of the blade;

[0018] S102 Calculate at least one characteristic frequency through the deformation displacement. The at least one characteristic frequency includes one or more of the following: the first-order flap vibration mode frequency, the first-order edgewise vibration mode frequency, and the first-order torsion mode frequency;

[0019] S103 Output an adjustment signal set of at least one of the rigid adjustment units through a rigid adjustment model by using a first adjustment rule. The adjustment signal set includes: at least one input voltage. Among them, the rigid adjustment model includes:

[0020] The first sub-model: , ;

[0021] The second sub-model: , ;

[0022] The third sub-model: , ;

[0023] Among them, is the inherent flap frequency, is the edgewise natural frequency, is the torsional natural frequency, is the first-order flap vibration mode frequency, is the first-order edgewise vibration mode frequency, is the first-order torsion mode frequency; , , They are the first difference threshold, the second difference threshold, and the third difference threshold respectively. m is the number of the rigid adjustment units. X, Y, and Z are the inherent flapping rigidity coefficient, the inherent lead-lag rigidity coefficient, and the inherent torsional rigidity coefficient corresponding to the positions where the rigid adjustment units are located respectively. is the input voltage corresponding to the rigid adjustment unit;

[0024] The first adjustment rule requires that the output adjustment signal set satisfies the first sub-model, the second sub-model, and the third sub-model.

[0025] In some embodiments, it further includes the steps:

[0026] S104 Adjust the inherent rigidity of the blade through the rigid adjustment unit by using the adjustment signal set in the first time period;

[0027] S105 Continuously monitor the characteristic deformation amount in the first time period, and calculate the characteristic deformation acceleration of the blade at multiple moments in the first time period through the characteristic deformation amount;

[0028] S106 Judge whether a new adjustment signal set needs to be output through the characteristic deformation acceleration by using the first determination rule; wherein, the first determination rule includes:

[0029] When the characteristic deformation acceleration gradually increases in the first time period, then use the second adjustment rule to output the new adjustment signal set of at least one of the rigid adjustment units through the rigid adjustment model; the second adjustment rule requires that the output new adjustment signal set satisfies the first sub-model and only satisfies one of the second sub-model or the third sub-model.

[0030] In some embodiments, it further includes the steps:

[0031] Adjust the inherent rigidity of the blade through the rigid adjustment unit by using the new adjustment signal set output in S106 in the second time period;

[0032] Continuously monitor the characteristic deformation amount in the second time period, and calculate the characteristic deformation acceleration of the blade at multiple moments in the second time period through the characteristic deformation amount; wherein,

[0033] When the characteristic deformation acceleration gradually increases or remains constant in the second time period, then send a prompt signal to the user; otherwise, continue to adjust the inherent rigidity of the blade by using the current new adjustment signal set.

[0034] In some embodiments, before entering S102 or S103, it further includes the steps:

[0035] Obtain the current operating speed of the wind turbine and the wind force in the current environment; use the second determination rule to determine whether to enter S102 or S103; wherein, the second determination rule requires that when the operating speed is less than a preset speed threshold and the wind force is less than a preset wind force threshold, enter S102 or S103 is allowed.

[0036] In some embodiments, before S103, the method further includes the steps of:

[0037] S107 When the statistical index of the characteristic deformation amount of the blade belongs to a preset first threshold, the third adjustment rule is used to pre-adjust the blade in the third time period, wherein the statistical index includes any one of the following: maximum value, average value, and the third adjustment rule is to enable at least one of the rigid adjustment units near the blade tip to adjust the natural frequency at the blade tip;

[0038] S108 Obtain the characteristic deformation acceleration of the characteristic deformation amount of the blade in the third time period;

[0039] S109 When the characteristic deformation acceleration gradually decreases, enter S103 is allowed.

[0040] In some embodiments, 3-5 piezoelectric ceramics are arranged in the rigid adjustment unit.

[0041] In some embodiments, at least one acceleration sensor is arranged on the blade, and the acceleration sensor is used to detect the deformation acceleration of the blade surface in three coordinate directions in the space coordinates.

[0042] In some embodiments, the rigid adjustment units are uniformly arranged in the length direction.

[0043] In some embodiments, the rigid adjustment unit is arranged inside the blade.

[0044] The present invention also provides a wind turbine blade flutter suppression system based on piezoelectric drive. A plurality of rigid adjustment units are distributed along the length direction of the blade. The rigid adjustment unit includes: at least two support plates and piezoelectric ceramics; the at least two support plates are arranged at intervals along the length direction, and the sides of the at least two support plates are connected to the blade. At least one hole is arranged on each support plate, and both ends of the piezoelectric ceramic are respectively arranged in the corresponding holes. When the length of the piezoelectric ceramic changes, the length of the rigid adjustment unit also changes accordingly, and thus the natural rigidity of the blade can be changed; wherein, at least one of the rigid adjustment units is arranged adjacent to the blade tip, and at least one of the rigid adjustment units is arranged adjacent to the blade root. Correspondingly, the system further includes:

[0045] A displacement monitoring module that obtains characteristic deformation amounts at multiple sites of the blade in the length direction, where the characteristic deformation amount refers to the magnitude of the deformation displacement of the blade surface in its vertical direction;

[0046] A characteristic frequency calculation module for calculating at least one characteristic frequency through the deformation displacement, where the at least one characteristic frequency includes one or more of the following: the 1st flap vibration mode frequency, the 1st lead-lag vibration mode frequency, and the 1st torsion mode frequency;

[0047] A signal output module for outputting an adjustment signal set of at least one of the rigid adjustment units through a rigid adjustment model using a first adjustment rule, where the adjustment signal set includes: at least one input voltage; wherein, the rigid adjustment model includes:

[0048] The first sub-model: , ;

[0049] The second sub-model: , ;

[0050] The third sub-model: , ;

[0051] Wherein, is the natural flap frequency, is the natural lead-lag frequency, is the natural torsion frequency, is the 1st flap vibration mode frequency, is the 1st lead-lag vibration mode frequency, is the 1st torsion mode frequency; , , are the first difference threshold, the second difference threshold, and the third difference threshold respectively, m is the number of the rigid adjustment units, X, Y, and Z are the natural flap rigidity coefficient, the natural lead-lag rigidity coefficient, and the natural torsion rigidity coefficient corresponding to the positions of the rigid adjustment units respectively, is the input voltage corresponding to the rigid adjustment unit;

[0052] The first adjustment rule requires that the output adjustment signal set satisfies the first sub-model, the second sub-model, and the third sub-model.

[0053] Beneficial technical effects:

[0054] Moreover, to ensure the effectiveness of flutter suppression, that is, to ensure the best coordinated suppression effect at multiple points, the present invention comprehensively selects three typical frequencies, namely, the first-order flap vibration mode frequency, the first-order lead-lag vibration mode frequency, and the first-order torsion mode frequency, as key evaluation indicators, and then comprehensively calculates a set of adjustment signals suitable for collaborative operation by integrating different types of modal frequencies and the suppression effects at different positions on the blade.

[0055] It should be noted that the solution of the present invention for collaborative operation of different longitudinal forces based on multiple points has, on the one hand, a simpler structural design, only requiring multiple piezoelectric ceramics to be arranged along the length direction of the blade (the application cost is lower and it will not overly affect the structural design of the blade itself); on the other hand, on the basis of comprehensively considering the overall collaborative effect, only a limited number of signal calculation factors are selected (the type differences of modal frequencies and the effect differences at different positions), and the effect differences at different positions can be confirmed at the beginning of blade design. Therefore, the real-time calculation pressure of the rigid adjustment model is relatively small, which is more conducive to application and implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale. Obviously, the following-described drawings are some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings according to these drawings without creative efforts.

[0057] Figure 1 Schematic diagram of the wind turbine blade structure in an exemplary embodiment of the present invention;

[0058] Figure 2 Schematic diagram of the first structure of the rigid adjustment unit in an exemplary embodiment of the present invention;

[0059] Figure 3 Schematic diagram of the second structure of the rigid adjustment unit in an exemplary embodiment of the present invention;

[0060] Figure 4 Schematic diagram of the signal input structure of the piezoelectric ceramic in an exemplary embodiment of the present invention;

[0061] Figure 5 Schematic diagram of the method flow in an exemplary embodiment of the present invention;

[0062] Figure 6 Schematic diagram of the system module structure in an exemplary embodiment of the present invention.

[0063] Summary of the identification of reference numerals:

[0064] 1 is the blade, 2 is the rigid adjustment unit, 3 is the acceleration sensor, 21 is the piezoelectric ceramic, 22 is the support plate, and 23 is the hole position. Detailed implementation manners

[0065] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0066] In this document, suffixes such as "module", "component", or "unit" used to represent elements are only for the convenience of describing the present invention, and they have no specific meaning in themselves. Therefore, "module", "component", or "unit" can be used interchangeably.

[0067] In this document, terms such as "upper", "lower", "inner", "outer", "front", "rear", "one end", "the other end", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation on the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0068] In this document, unless otherwise clearly defined and limited, terms such as "installed", "provided with", "connected", etc. shall be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0069] In this document, "and / or" includes any and all combinations of one or more of the listed related items.

[0070] In this document, "a plurality of" means two or more, that is, it includes two, three, four, five, etc.

[0071] It should be noted that in this text, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising that element.

[0072] As used in this specification, the term "about" typically means + / - 5% of the stated value, more typically + / - 4% of the stated value, more typically + / - 3% of the stated value, more typically + / - 2% of the stated value, even more typically + / - 1% of the stated value, and even more typically + / - 0.5% of the stated value.

[0073] In this specification, certain embodiments may be disclosed in a format that is within a certain range. It should be understood that this description of "within a certain range" is merely for convenience and brevity and should not be construed as a rigid limitation on the disclosed range. Therefore, the description of the range should be considered to have specifically disclosed all possible sub-ranges and the individual numerical values within that range. For example, the description of the range 1 - 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as the individual numbers within that range, such as 1, 2, 3, 4, 5, and 6. The above rules apply regardless of the breadth of the range.

[0074] With the rapid development of wind power applications, the number of wind turbines has been increasing sharply, and the power generation capacity of the turbines has also been continuously increasing. Larger wind turbines also require larger blades. Nowadays, the length of many wind turbine blades often exceeds 100 meters. For example, the length of the MySE292 super-large blade reaches 143 meters.

[0075] Such ultra-long blades can absorb more wind energy, but once flutter occurs and cannot be effectively suppressed, it will also bring extremely high economic losses.

[0076] To reduce the damage of flutter to the blade and at the same time reduce the installation and control difficulty of the suppression system. Refer to Figures 1-5 As shown, contrary to the traditional technical route (such as applying a reverse force to suppress flutter), the present invention proposes a new technical route: by adjusting the inherent rigidity of the local position of the blade through longitudinal forces, and then suppressing the flutter of the blade through the collaborative change of rigidity at multiple sites.

[0077] Embodiment 1

[0078] Refer toFigure 5 As shown in Figure 5 , the present invention provides a method for suppressing the flutter of a wind turbine blade based on piezoelectric drive. A plurality of rigid adjustment units are distributed along the length direction of the blade. The rigid adjustment unit includes: at least two support plates and piezoelectric ceramics. The at least two support plates are arranged at intervals along the length direction, and the sides of the at least two support plates are connected to the blade. At least one hole position is respectively arranged on the support plates, and both ends of the piezoelectric ceramics are respectively arranged in the corresponding hole positions. When the length of the piezoelectric ceramics changes, the length of the rigid adjustment unit also changes accordingly, so as to be able to change the inherent rigidity of the blade.

[0079] In some embodiments, at least one of the rigid adjustment units is disposed adjacent to the tip of the blade, and at least one of the rigid adjustment units is disposed adjacent to the root of the blade.

[0080] Correspondingly, the method includes the steps of:

[0081] S101 Obtain the characteristic deformation amounts at a plurality of positions of the blade in the length direction. The characteristic deformation amount refers to the magnitude of the deformation displacement of the blade surface in the vertical direction thereof.

[0082] Wherein, the vertical direction refers to the direction perpendicular or approximately perpendicular to the blade surface. In other words, the angle between the vertical direction and the blade surface is approximately 90°.

[0083] S102 Calculate at least one characteristic frequency from the deformation displacement. The at least one characteristic frequency includes one or more of the following: the first-order flap vibration mode frequency, the first-order edgewise vibration mode frequency, and the first-order torsion mode frequency.

[0084] For example, in some embodiments, the corresponding characteristic frequency can be calculated by using the fast Fourier transform method.

[0085] S103 Output an adjustment signal set of at least one of the rigid adjustment units through a rigid adjustment model by using a first adjustment rule. The adjustment signal set includes: at least one input voltage. Wherein, the rigid adjustment model includes:

[0086] The first sub-model: , ;

[0087] The second sub-model: , ;

[0088] The third sub-model: , ;

[0089] Wherein, is the inherent flapping frequency, is the inherent flapping frequency, is the inherent torsional frequency, is the first-order flapping vibration mode frequency, is the first-order flapping mode frequency, is the first-order torsional mode frequency; , , are the first difference threshold, the second difference threshold, and the third difference threshold respectively, m is the number of the rigid adjustment units, and X, Y, and Z are the inherent flapping rigidity coefficient, the inherent flapping rigidity coefficient, and the inherent torsional rigidity coefficient corresponding to the positions where the rigid adjustment units are located respectively, is the input voltage corresponding to the rigid adjustment unit;

[0090] Among them, each difference threshold can be set by the user himself, and each rigidity coefficient can be determined in advance by the user during the blade design process.

[0091] The first adjustment rule requires that the output adjustment signal set satisfies the first sub-model, the second sub-model, and the third sub-model.

[0092] Correspondingly, when the adjustment signal set is input into each rigid adjustment unit, the longitudinal forces with different positions and different magnitudes can be used to jointly adjust the inherent rigidity of the blade, so that the vibration frequency of the blade is far from its inherent frequency.

[0093] In this embodiment, a method for suppressing flutter by changing the inherent rigidity of the blade through longitudinal force is proposed.

[0094] Moreover, in order to ensure the effectiveness of flutter suppression, that is, to ensure the best coordinated suppression effect at multiple points, the present invention comprehensively selects three typical frequencies, namely the first-order flapping vibration mode frequency, the first-order flapping mode frequency, and the first-order torsional mode frequency, as key evaluation indicators, and then fuses different types of modal frequencies and the suppression effects at different positions on the blade to comprehensively calculate the adjustment signal set suitable for collaborative operation.

[0095] It should be noted that the scheme of collaborative operation of different longitudinal forces based on multiple points proposed by the present invention is, on the one hand, simpler in structural design, only requiring multiple piezoelectric ceramics to be arranged along the length direction of the blade (the application cost is lower and it will not overly affect the structural design of the blade itself); on the other hand, on the basis of comprehensively considering the overall collaborative effect, only a limited number of signal calculation factors are selected (the type differences of modal frequencies and the effect differences at different positions), and the effect differences at different positions can be confirmed at the beginning of blade design. Therefore, the real-time calculation pressure of the rigid adjustment model is relatively small, which is more conducive to application and implementation.

[0096] For example, in some embodiments, refer to Figures 1-4 As shown, a plurality of rigid adjustment units 2 are sequentially arranged on the blade 1 along its length direction (i.e., the longitudinal direction). Among them, the rigid adjustment unit 2 includes: two support plates 22, the edges of the support plates 22 are connected to the inner blade surface of the blade 1; opposite holes 23 are respectively arranged on the two support plates 22, and both ends of the piezoelectric ceramic 21 pass through the holes 23 respectively to be indirectly fixed on the blade.

[0097] And both ends of the piezoelectric ceramic are respectively electrically connected with wires to control the input voltage of the piezoelectric ceramic through the wires. The length of the piezoelectric ceramic will change under different input voltages, and this length change will correspondingly generate a tensile force on the blade in the longitudinal direction.

[0098] Correspondingly, when at least one position area of the blade is subjected to tensile forces of different magnitudes and / or in different directions in the longitudinal direction, the rigidity of this position area also changes accordingly.

[0099] Furthermore, adopting the above rigid adjustment model is also beneficial to flexibly adjust the signal input scheme. In some embodiments, it further includes steps:

[0100] S104 Use the adjustment signal set to adjust the inherent rigidity of the blade through the rigid adjustment unit within the first time period;

[0101] S105 Continuously monitor the characteristic deformation amount within the first time period, and calculate the characteristic deformation acceleration of the blade at multiple moments within the first time period through the characteristic deformation amount;

[0102] S106 Use the first determination rule to determine whether to output a new adjustment signal set through the characteristic deformation acceleration; wherein, the first determination rule includes:

[0103] When the characteristic deformation acceleration gradually increases within the first time period, then use the second adjustment rule to output the new adjustment signal set of at least one of the rigid adjustment units through the rigid adjustment model; the second adjustment rule requires that the output new adjustment signal set satisfies the first sub-model and only satisfies one of the second sub-model or the third sub-model.

[0104] On the contrary, it preliminarily indicates that the adjustment signal set output by S103 has a reliable adjustment effect.

[0105] For example, in some embodiments, different priorities can be preset for the second sub-model and the third sub-model, that is, when the second adjustment rule is enabled, one of the sub-models with a higher priority can be selected to cooperate with the first sub-model to output a new adjustment signal set.

[0106] Alternatively, in some other embodiments, an acceleration sensor can be used to calculate the flapping deformation amount and the torsional deformation amount in real time, determine the corresponding deformation levels based on the flapping deformation amount and the torsional deformation amount, and select the sub-model associated with the frequency type (such as flapping or torsion) corresponding to the deformation amount with a higher deformation level as the recommended sub-model, so as to jointly calculate the adjustment signal set through the recommended sub-model and the first sub-model.

[0107] For example, according to the magnitude of the flapping deformation amount, it can be at least divided into level one and level two in sequence (for example, if the flapping deformation amount is greater than the first set value, the flapping deformation is set to level one, and if it is less than or equal to the first set value, the flapping deformation is set to level two); according to the magnitude of the torsional deformation amount, it can be at least divided into level one and level two in sequence (for example, if the torsional deformation amount is greater than the second set value, the torsional deformation is set to level one, and if it is less than or equal to the second set value, the torsional deformation is set to level two). For example, when the flapping deformation is at level one and the torsional deformation is at level two, the second sub-model is selected as the recommended sub-model.

[0108] In this embodiment, the adjustment rules of the rigid adjustment model can be flexibly adapted according to different flutter types (or rather, deformation types) to avoid ineffective adjustment.

[0109] Among them, the flapping deformation amount or the torsional deformation amount refers to the displacement of the blade surface in the flapping or torsional direction per unit time.

[0110] That is to say, in this embodiment, the adjustment effect of the adjustment signal set output by S103 can also be monitored in real time. When it is detected that the characteristic deformation acceleration (equivalent to the trend of blade deformation) is not effectively suppressed, the multi-model characteristics of the rigid adjustment model can be used to change the adjustment rules and output a new adjustment signal set.

[0111] It should be noted that the super-large flexible blade has the structural characteristics of an ultra-large slenderness ratio and large flexibility, and its aerodynamic problems have the characteristics of three-dimensional, rotational, and non-linear. Therefore, the non-linear vibration, aeroelastic coupling effect, and flutter law of the large flexible blade are extremely complex.

[0112] In order to simplify the control scheme, the present application proposes a rigid adjustment model with multiple sub-model sets. Therefore, when it is monitored that the adjustment signal set output by the default rule (such as the first adjustment rule) cannot effectively suppress flutter due to coupling or other reasons during collaborative operation, the cooperation mode of different sub-models can also be flexibly adjusted to output a new adjustment signal set and weaken the adverse effect of the coupling effect on the suppression effect.

[0113] In some embodiments, it further includes the steps:

[0114] Adjust the inherent rigidity of the blade through the rigid adjustment unit by using the new adjustment signal set output in S106 during the second period;

[0115] Continuously monitor the characteristic deformation amount during the second period, and calculate the characteristic deformation acceleration of the blade at multiple moments during the second period through the characteristic deformation amount (such as the acceleration of the flapping deformation); wherein,

[0116] When the characteristic deformation acceleration gradually increases or remains constant during the second period, a prompt signal is sent to the user; otherwise, the current new adjustment signal set is used to continue adjusting the inherent rigidity of the blade.

[0117] When effective suppression still cannot be achieved after secondary adjustment, manual intervention can be introduced through a prompt signal.

[0118] In some embodiments, before entering S102 or S103, the following steps are further included:

[0119] Obtain the current operating speed of the wind turbine and the wind force under the current environment; use the second determination rule to determine whether to allow entering S102 or S103; wherein, the second determination rule requires that when the operating speed is less than a preset speed threshold and the wind force is less than a preset wind force threshold, entering S102 or S103 is allowed.

[0120] In this embodiment, in order to reduce the situation of ineffective adjustment, before starting the multi-model adjustment scheme, the operating speed and wind force will also be comprehensively evaluated to ensure that the current operating conditions have good adaptability to the multi-model adjustment scheme.

[0121] In some embodiments, before S103, the following steps are further included:

[0122] S107 When the statistical index of the characteristic deformation amount of the blade belongs to a preset first threshold, pre-adjust the blade during the third period by using the third adjustment rule, wherein the statistical index includes any one of the following: maximum value, average value, and the third adjustment rule is to enable at least one of the rigid adjustment units near the blade tip to adjust the natural frequency at the blade tip;

[0123] S108 Obtain the characteristic deformation acceleration of the characteristic deformation amount of the blade during the third period;

[0124] S109 When the characteristic deformation acceleration gradually decreases, allow entering S103;

[0125] On the contrary, a corresponding prompt signal can be sent to the user to prompt manual intervention.

[0126] In some embodiments, before officially activating the rigid adjustment function, pre-tests will also be carried out through local rigid adjustment at the blade tip to further avoid ineffective adjustment, that is, to reduce the degree of blade damage.

[0127] For example, when the pre-test finds that the inhibitory effect of rigid adjustment on flutter is very limited, the user will be reminded to intervene manually.

[0128] Preferably, in this embodiment, manual intervention can be introduced at key nodes before the official adjustment (i.e., the pre-adjustment link) and after the secondary adjustment, so as to cooperate with computer automated control and manual work to ensure the reliability of the adjustment.

[0129] In some embodiments, 3-5 piezoelectric ceramics are arranged in the rigid adjustment unit.

[0130] In some embodiments, at least one acceleration sensor is arranged on the blade, and the acceleration sensor is used to detect the deformation acceleration of the blade surface in three coordinate directions in the space coordinate.

[0131] For example, in some embodiments, a plurality of acceleration sensors are arranged at intervals along the direction from the blade root to the blade tip of the blade, and the acceleration sensors can measure the vibration acceleration of the blade when the blade vibrates.

[0132] For example, a three-dimensional rectangular space coordinate system is created. The three-dimensional rectangular coordinate system is to make three mutually perpendicular number axes passing through a fixed point O in space. These three number axes are respectively called the x-axis (horizontal axis), y-axis (vertical axis), and z-axis (vertical axis). Correspondingly, the acceleration sensor can be used to monitor the vibration acceleration of a certain point on the blade surface in the x, y, and z axes. Furthermore, the displacement of this point can be calculated through the vibration acceleration. Correspondingly, in this embodiment, the displacement is used to characterize the deformation amount (or deformation degree) of the blade.

[0133] For example, the flapping direction refers to the direction perpendicular or approximately perpendicular to the blade surface. Correspondingly, the displacement in the flapping direction can be considered as the flapping deformation amount.

[0134] In some embodiments, the characteristic frequency calculation process is as follows:

[0135] Calculate the deformation displacement in the characteristic direction (such as the flapping direction, pitching direction, or torsion direction) within a period of time; in other words, obtain the change relationship between the displacement and time, that is, the time-domain signal;

[0136] Use FFT (Fast Fourier Transform) to convert the time-domain signal into a frequency-domain signal, that is, obtain the characteristic frequency of vibration generated in the corresponding characteristic direction.

[0137] In some embodiments, the rigid adjustment units are uniformly arranged in the length direction.

[0138] In some embodiments, the rigid adjustment unit is disposed inside the blade.

[0139] Taking a specific embodiment as an example, the technical solution of the present invention will be further described below:

[0140] If the blade length of the wind turbine is L, five acceleration sensors are respectively arranged inside at 1 / 5L, 2 / 5L, 3 / 5L, 4 / 5L, and L of the blade length (i.e., the distance from the blade root). At the same time, piezoelectric stack modules are arranged at five cross-sections at the same positions of the blade, and there are 3 to 5 piezoelectric ceramics in each piezoelectric stack module according to the cross-sectional shape.

[0141] After the suppression system is powered on, the acceleration sensors start to work. When it detects that the blade generates flutter deformation, it transmits the deformation signal to the control computer. The control computer calculates the anti-waveform electrical signal, and according to this electrical signal, drives the piezoelectric ceramics to actuate and generate the corresponding longitudinal force.

[0142] f a =X 1 *E 1 + X 2 *E 2 + X 3 *E 3 + X 4 *E 4 + X 5 *E 5 ；

[0143] f b =Y 1 *E 1 + Y 2 *E 2 + Y 3 *E 3 + Y 4 *E 4 + Y 5 *E 5 ；

[0144] f c =Z 1 *E 1 + Z 2 *E 2 + Z 3 *E 3 + Z 4 *E 4 + Z 5 *E 5 ；

[0145] ;

[0146] Among them, X 1 -X to 5 are the inherent flapping rigidity coefficients at different positions, Y 1 - Y to 5 are the inherent lagging rigidity coefficients at different positions, Z 1 -Z to 5 are the inherent torsion rigidity coefficients at different positions, E 1 –E to 5 are the input voltages adopted at different positions.

[0147] is the strain of the piezoelectric material; is the elastic compliance coefficient; is the stress of the piezoelectric material; is the piezoelectric strain constant; is the applied electric field strength.

[0148] Among them, , are the natural frequencies of the piezoelectric ceramics after being designed, which remain unchanged during use. Mainly by changing to achieve changes. can be changed by changing the input voltage signal.

[0149] Among them, 5 acceleration sensors measure the vibration displacement of the blade in real time during blade vibration. By transmitting it to the computer, the computer calculates its main vibration modal frequencies, mainly the 1st order flapping vibration modal frequency f 1, the 1st order lagging modal frequency f 2 and the 1st order torsion modal frequency f 3.

[0150] Five piezoelectric ceramic actuators are installed at 1 / 5L, 2 / 5L, 3 / 5L, 4 / 5L, and L of the blade, which are respectively denoted as the 1st position, the 2nd position, the 3rd position, the 4th position, and the 5th position. Mainly by applying force between the longitudinal orifice plates of the blade to change the inherent rigidity of the blade, so that the inherent flapping frequency of the blade f a is far from f 1, the inherent lagging frequency f b is less than f 1, the inherent torsion frequency f c is far from f 3.

[0151] Among them, the inherent flapping rigidity coefficient, inherent lagging rigidity coefficient, and inherent torsion rigidity coefficient at each position can be obtained through experimental tests or can be determined at the time of blade structure design.

[0152] Alternatively, in some other embodiments, power supplies are connected to both sides of each piezoelectric ceramic. By controlling the voltage magnitude and change frequency of the connected power supplies, the single piezoelectric ceramic can be elongated or shortened. When the deformations of multiple piezoelectric ceramics in the same cross-section are inconsistent, the blade can be driven to generate torsional deformation or lagging deformation.

[0153] Embodiment 2

[0154] See Figure 6 As shown, the present invention also correspondingly provides a flutter suppression system for a wind turbine blade based on piezoelectric drive. A plurality of rigidity adjustment units are distributed along the length direction on the blade. The rigidity adjustment unit includes: at least two support plates and piezoelectric ceramics; the at least two support plates are spaced along the length direction, and the sides of the at least two support plates are connected to the blade. At least one hole position is respectively arranged on the support plates, and both ends of the piezoelectric ceramic are respectively arranged in the corresponding hole positions. When the length of the piezoelectric ceramic changes, the length of the rigidity adjustment unit also changes accordingly, and thus the inherent rigidity of the blade can be changed; among them, at least one of the rigidity adjustment units is arranged adjacent to the tip of the blade, and at least one of the rigidity adjustment units is arranged adjacent to the root of the blade. Correspondingly, the system further includes:

[0155] A displacement monitoring module, which acquires the characteristic deformation amounts at multiple positions of the blade in the length direction. The characteristic deformation amount refers to the deformation displacement magnitude of the blade surface in the vertical direction of the blade;

[0156] A characteristic frequency calculation module, which is used to calculate at least one characteristic frequency through the deformation displacement. The at least one characteristic frequency includes one or more of the following: the 1st flapping vibration mode frequency, the 1st lagging vibration mode frequency, and the 1st torsion vibration mode frequency;

[0157] A signal output module, which is used to output an adjustment signal set of at least one of the rigidity adjustment units through a rigidity adjustment model by adopting a first adjustment rule. The adjustment signal set includes: at least one input voltage; among them, the rigidity adjustment model includes:

[0158] The first sub-model: , ;

[0159] The second sub-model: , ;

[0160] The third sub-model: , ;

[0161] Among them, is the inherent flapping frequency, is the inherent pitching frequency, is the inherent torsion frequency, is the 1st order flapping vibration mode frequency, is the 1st order pitching mode frequency, is the 1st order torsion mode frequency; , , are the first difference threshold, the second difference threshold and the third difference threshold respectively, m is the number of the rigid adjustment units, and X, Y, and Z are the inherent flapping rigidity coefficient, the inherent pitching rigidity coefficient and the inherent torsion rigidity coefficient corresponding to the positions where the rigid adjustment units are located respectively, is the input voltage corresponding to the rigid adjustment unit;

[0162] The first adjustment rule requires that the output adjustment signal set satisfies the first sub-model, the second sub-model and the third sub-model.

[0163] In some embodiments, the system further includes:

[0164] A first adjustment module, configured to adjust the inherent rigidity of the blade through the rigid adjustment unit within a first time period by using the adjustment signal set;

[0165] A first judgment module, configured to continuously monitor the characteristic deformation amount within the first time period, and calculate the characteristic deformation acceleration of the blade at multiple moments within the first time period through the characteristic deformation amount; judge whether a new adjustment signal set needs to be output through the characteristic deformation acceleration by using a first judgment rule; wherein, the first judgment rule includes: when the characteristic deformation acceleration gradually increases within the first time period, then a second adjustment rule is used to output at least one new adjustment signal set of the rigid adjustment units through a rigid adjustment model; the second adjustment rule requires that the output new adjustment signal set satisfies the first sub-model and only satisfies one of the second sub-model or the third sub-model.

[0166] In some embodiments, it further includes: a second adjustment module, configured to adjust the inherent rigidity of the blade through the rigid adjustment unit within a second time period by using the new adjustment signal set output by the first judgment module;

[0167] Continuously monitor the characteristic deformation amount within the second time period, and calculate the characteristic deformation acceleration of the blade at multiple moments within the second time period through the characteristic deformation amount; wherein,

[0168] When the characteristic deformation acceleration gradually increases or remains constant during the second period, a prompt signal is sent to the user; otherwise, the current new set of adjustment signals is used to continue adjusting the inherent rigidity of the blade.

[0169] In some embodiments, before entering the signal output module or the characteristic frequency calculation module, the method further includes the steps of:

[0170] Obtaining the current operating speed of the wind turbine and the wind force under the current environment; using a second determination rule to determine whether to allow entry into the signal output module or the characteristic frequency calculation module; wherein, the second determination rule requires that when the operating speed is less than a preset speed threshold and the wind force is less than a preset wind force threshold, entry into the signal output module or the characteristic frequency calculation module is allowed.

[0171] In some embodiments, it further includes: a third adjustment module, configured to, when the statistical index of the characteristic deformation amount of the blade belongs to a preset first threshold, perform pre-adjustment on the blade during a third period by using a third adjustment rule, where the statistical index includes any one of the following: maximum value, average value, and the third adjustment rule is to enable at least one of the rigidity adjustment units near the blade tip to adjust the natural frequency at the blade tip; obtaining the characteristic deformation acceleration of the characteristic deformation amount of the blade during the third period; when the characteristic deformation acceleration gradually decreases, entry into the signal output module is allowed.

[0172] It should be noted that in this article, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device including a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including that element.

[0173] Through the description of the above embodiments, those skilled in the art can clearly understand that the above-described embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course, they can also be implemented by hardware, but in many cases, the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes several instructions for causing a computer terminal (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0174] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative rather than restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit of the present invention and the scope protected by the claims. All of these fall within the protection scope of the present invention.

Claims

1. A method for suppressing wind turbine blade flutter based on piezoelectric drive, characterized in that: A plurality of rigidity adjustment units are distributed along the length direction of the blade, and the rigidity adjustment units include: at least two support plates and piezoelectric ceramics; the at least two support plates are spaced apart along the length direction, and the sides of the at least two support plates are connected to the blade, and at least one hole is respectively provided on the support plates, and the two ends of the piezoelectric ceramics are respectively provided in the corresponding hole positions, and when the length of the piezoelectric ceramics changes, the length of the rigidity adjustment unit also changes accordingly, thereby being able to change the inherent rigidity of the blade; wherein at least one rigidity adjustment unit is provided adjacent to the tip of the blade, and at least one rigidity adjustment unit is provided adjacent to the root of the blade, and correspondingly, the method includes the steps of: S101 obtaining characteristic deformation amounts of the blade at multiple locations along the length direction, and the characteristic deformation amount refers to the deformation displacement magnitude of the blade surface of the blade in its vertical direction; S102: obtaining at least one characteristic frequency through the deformation displacement calculation, wherein the at least one characteristic frequency includes one or more of the following: a first-order flapping vibration modal frequency, a first-order swing vibration modal frequency, and a first-order torsional modal frequency; S103: outputting a set of adjustment signals of at least one of the rigidity adjustment units through a rigidity adjustment model using a first adjustment rule, wherein the set of adjustment signals includes: at least one input voltage; wherein the rigidity adjustment model includes: First sub-model: , ; Second sub-model: , ; The third sub-model: , ; in, is the natural flapping frequency, is the natural frequency of oscillation, is the torsional natural frequency, is the first-order flapping vibration mode frequency, is the first-order shimmy modal frequency, is the first-order torsional mode frequency; , , are the first difference threshold, the second difference threshold and the third difference threshold respectively, m is the number of the rigidity adjustment units, X, Y, and Z are the inherent flapping rigidity coefficient, the inherent swing rigidity coefficient, and the inherent torsional rigidity coefficient corresponding to the position of the rigidity adjustment unit, respectively. is the input voltage corresponding to the rigidity adjustment unit; The first adjustment rule requires that the output adjustment signal set satisfies the first sub-model, the second sub-model and the third sub-model.

2. The method for suppressing wind turbine blade flutter based on piezoelectric drive according to claim 1, characterized in that: Also includes the steps: S104: using the adjustment signal set to adjust the inherent rigidity of the blade through the rigidity adjustment unit within a first period of time; S105: continue to monitor the characteristic deformation amount during the first period, and calculate characteristic deformation accelerations of the blade at multiple moments during the first period according to the characteristic deformation amount; S106 uses a first determination rule to determine whether a new adjustment signal set needs to be output based on the characteristic deformation acceleration; wherein the first determination rule includes: When the characteristic deformation acceleration gradually increases within the first time period, a second adjustment rule is used to output the new adjustment signal set of at least one of the rigid adjustment units through the rigid adjustment model; the second adjustment rule requires that the output new adjustment signal set satisfies the first sub-model and only satisfies one of the second sub-model or the third sub-model.

3. The method for suppressing wind turbine blade flutter based on piezoelectric drive according to claim 2, characterized in that: Also includes the steps: Using the new adjustment signal set output in S106, the rigidity adjustment unit adjusts the inherent rigidity of the blade in a second period of time; The characteristic deformation amount is continuously monitored during the second period, and characteristic deformation accelerations of the blade at multiple moments during the second period are calculated using the characteristic deformation amount; wherein, When the characteristic deformation acceleration gradually increases or remains constant during the second time period, a prompt signal is sent to the user; otherwise, the inherent rigidity of the blade is continuously adjusted using the current new adjustment signal set.

4. The method for suppressing wind turbine blade flutter based on piezoelectric drive according to claim 2, characterized in that: Before entering S102 or S103, the following steps are also included: Obtain the current operating speed of the wind turbine and the wind force in the current environment; use the second judgment rule to determine whether to allow entry into S102 or S103; wherein the second judgment rule requires that when the operating speed is less than a preset speed threshold and the wind force is less than a preset wind force threshold, entry into S102 or S103 is allowed.

5. The method for suppressing wind turbine blade flutter based on piezoelectric drive according to claim 1, characterized in that: Before S103, the step further includes: S107, when the statistical index of the characteristic deformation amount of the blade belongs to the preset first threshold, pre-adjusting the blade within a third time period by using a third adjustment rule, wherein the statistical index includes any one of the following: a maximum value and an average value, and the third adjustment rule is to enable at least one of the rigidity adjustment units adjacent to the blade tip to adjust the natural frequency at the blade tip; S108: obtaining a characteristic deformation acceleration of the characteristic deformation amount of the blade in a third time period; S109 When the characteristic deformation acceleration gradually decreases, it is allowed to enter S103.

6. The method for suppressing wind turbine blade flutter based on piezoelectric drive according to claim 1, characterized in that: The rigidity adjustment unit is provided with 3-5 piezoelectric ceramics.

7. The method for suppressing wind turbine blade flutter based on piezoelectric drive according to claim 1, characterized in that: At least one acceleration sensor is arranged on the blade, and the acceleration sensor is used to detect the deformation acceleration of the blade surface in three coordinate directions in space coordinates.

8. The method for suppressing wind turbine blade flutter based on piezoelectric drive according to claim 1, characterized in that: The rigidity adjusting units are evenly arranged in the length direction.

9. The method for suppressing wind turbine blade flutter based on piezoelectric drive according to claim 1, characterized in that: The rigidity adjustment unit is disposed inside the blade.

10. A piezoelectric-driven wind turbine blade flutter suppression system, characterized in that: A plurality of rigidity adjustment units are distributed along the length direction of the blade, and the rigidity adjustment unit includes: at least two support plates and piezoelectric ceramics; the at least two support plates are arranged at intervals along the length direction, and the sides of the at least two support plates are connected to the blade, and at least one hole is respectively arranged on the support plate, and the two ends of the piezoelectric ceramic are respectively arranged in the corresponding hole. When the length of the piezoelectric ceramic changes, the length of the rigidity adjustment unit also changes accordingly, thereby changing the inherent rigidity of the blade; wherein at least one rigidity adjustment unit is arranged adjacent to the tip of the blade, and at least one rigidity adjustment unit is arranged adjacent to the root of the blade. Correspondingly, the system also includes: A displacement monitoring module, for obtaining characteristic deformation amounts of the blade at a plurality of locations in the length direction, wherein the characteristic deformation amount refers to the deformation displacement magnitude of the blade surface in the vertical direction of the blade; A characteristic frequency calculation module, used for obtaining at least one characteristic frequency through the deformation displacement calculation, wherein the at least one characteristic frequency includes one or more of the following: a first-order flapping vibration modal frequency, a first-order swing vibration modal frequency, and a first-order torsional modal frequency; A signal output module, configured to output a set of adjustment signals of at least one of the rigidity adjustment units through a rigidity adjustment model using a first adjustment rule, wherein the set of adjustment signals includes: at least one input voltage; wherein the rigidity adjustment model includes: First sub-model: , ; Second sub-model: , ; The third sub-model: , ; in, is the natural flapping frequency, is the natural frequency of oscillation, is the torsional natural frequency, is the first-order flapping vibration mode frequency, is the first-order shimmy modal frequency, is the first-order torsional mode frequency; , , are the first difference threshold, the second difference threshold and the third difference threshold respectively, m is the number of the rigidity adjustment units, X, Y, Z are the inherent flapping rigidity coefficient, the inherent swing rigidity coefficient and the inherent torsional rigidity coefficient corresponding to the position of the rigidity adjustment unit respectively, is the input voltage corresponding to the rigidity adjustment unit; The first adjustment rule requires that the output adjustment signal set satisfies the first sub-model, the second sub-model and the third sub-model.

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