Variable pitch control method, system and wind turbine for a wind turbine

Abstract

This disclosure provides a pitch control method, system, and wind turbine generator set. The pitch control method includes: determining the changing trend of the generator speed of the wind turbine generator set in response to the current output power of the wind turbine generator set reaching the rated power; and controlling the blade pitch of the wind turbine generator set based on a control strategy corresponding to the changing trend, wherein different changing trends correspond to different control strategies, and the control strategies include a first control strategy and a second control strategy. This disclosure solves the problem that the pitch reduction schemes of related technologies are difficult to apply to large-megawatt wind turbine generator sets, enabling the unit to effectively reduce load at rated power, ensuring the safety and stability of unit operation.

Description

Technical Field

[0001] This disclosure relates to the field of wind power generation, and more specifically, to a pitch control method, system, and wind turbine generator set. Background Technology

[0002] Wind energy, as an inexhaustible, clean, and pollution-free renewable energy source, has received widespread attention in the energy sector for its development and utilization. With the development of wind power generation technology, the control methods of wind turbine generators have undergone several improvements, including fixed-pitch stall turbines, variable-pitch constant-speed turbines, and variable-speed constant-frequency turbines. Among these, the biggest advantage of variable-speed constant-frequency wind turbine generators compared to stall turbine generators is their stable power output above rated wind speed, making them the mainstream model today. With the increasing demand for wind power generation, the application of large-megawatt wind turbine generators is becoming increasingly widespread, with single-unit capacity exceeding 16 megawatts, blade lengths continuously increasing, and tower heights exceeding 140 meters.

[0003] Specifically, compared to smaller units, large-megawatt wind turbines, while increasing power generation, face more severe challenges in terms of unit safety and grid stability. On one hand, due to the larger blades and towers of large-megawatt units, they are more sensitive to changes in wind conditions, and wind loads have a more significant impact on the loads of critical components. For example, as blade length increases, the swept area becomes larger, absorbing more wind energy. Therefore, the blades are more sensitive to wind speed changes, and the combined fatigue load (especially at the blade root) at the hub center is also greater. Furthermore, the rotor speed is more significantly affected by wind speed changes, further increasing fatigue loads. On the other hand, as the tower rises, the vibration amplitude at the top and bottom of the tower increases with wind speed changes, significantly increasing tower fatigue loads and potentially severely impacting tower lifespan. On the other hand, large-megawatt units have greater output power. Compared to smaller units, large-megawatt units will have a higher maximum output power for the same percentage power fluctuation. For example, for a 7500kW unit with a rated power, a 15% power fluctuation range is ±1125kW; while for a 16MW large-megawatt unit, the power fluctuation range is ±2400kW. Therefore, large-megawatt units will experience greater impacts on the unit's converter and even the grid side.

[0004] Large-megawatt wind turbine generators have greater requirements for output power stability and fatigue load reduction of key components compared to small-power generators. Therefore, compared to small-power generators, the control strategies for output power and load reduction of key components also need to consider more practical issues.

[0005] However, the pitch reduction schemes in related technologies are all designed for small-power units. They do not take into account the special characteristics of large-megawatt units during the control process. Therefore, they are difficult to apply to large-megawatt units, and even if they are applied to large-megawatt units, it is difficult to ensure the safety and stability of the units. Summary of the Invention

[0006] In view of the problem that the pitch control scheme in related technologies is difficult to apply to large-megawatt wind turbine generator sets, this disclosure provides a pitch control method, system and wind turbine generator set for wind turbine generator sets.

[0007] The first aspect of this disclosure provides a pitch control method for a wind turbine generator set. The pitch control method includes: determining the changing trend of the generator speed of the wind turbine generator set in response to the current output power of the wind turbine generator set reaching the rated power; and controlling the blade pitch of the wind turbine generator set based on a control strategy corresponding to the changing trend. Different changing trends correspond to different control strategies. The control strategies include a first control strategy and a second control strategy. The first control strategy includes: using a preset power as a control target for the output power of the wind turbine generator set to control the blade pitch. The second control strategy includes: using a preset torque as a control target for the torque of the generator of the wind turbine generator set to control the blade pitch.

[0008] Optionally, the blade pitch of the wind turbine generator can be controlled in the following ways: in response to an upward trend, the blade pitch is controlled based on the second control strategy; in response to a downward trend, the blade pitch is controlled based on the first control strategy.

[0009] Optionally, the pitch control method further includes: in response to the change in the trend, switching between the first control strategy and the second control strategy by adjusting preset minimum torque coefficient, maximum torque coefficient and switching power coefficient, wherein the minimum torque coefficient and the maximum torque coefficient are used to determine the control target of the generator torque, and the switching power coefficient is used to determine the control target of the wind turbine generator output power.

[0010] Optionally, the first control strategy can be switched by adjusting the minimum torque coefficient to be within the minimum coefficient range, adjusting the maximum torque coefficient to be within the maximum coefficient range, and adjusting the switching power coefficient to a preset power coefficient, wherein the minimum torque coefficient is less than the maximum torque coefficient.

[0011] Optionally, the second control strategy is executed by adjusting both the minimum torque coefficient and the maximum torque coefficient to a preset torque coefficient, and adjusting the switching power coefficient to be within the power coefficient range, wherein the lower limit of the power coefficient range is greater than the preset power coefficient, the preset torque coefficient is greater than or equal to the upper limit of the minimum coefficient range, and less than or equal to the lower limit of the maximum coefficient range.

[0012] Optionally, the pitch control method further includes: in response to the current output power of the wind turbine being less than a preset power limit, performing the step of determining the changing trend of the generator speed of the wind turbine; in response to the current output power of the wind turbine being greater than or equal to the power limit, controlling the blades to pitch based on the first control strategy, wherein the power limit is determined based on the switching power coefficient and the rated power of the wind turbine.

[0013] Optionally, the trend of the generator speed of the wind turbine generator set is determined by: comparing the current measured generator speed with the preset generator speed to determine the speed difference; determining the speed difference change rate based on the speed difference; determining the speed change rate by combining the speed difference and the speed difference change rate; and determining the trend of the generator speed based on the speed change rate.

[0014] Optionally, the trend of the generator speed change is determined by: determining that the generator speed is on an upward trend in response to the rate of change of the speed meeting a preset condition; determining that the generator speed is on a downward trend in response to the rate of change of the speed not meeting the preset condition, wherein the preset condition includes: the rate of change of the speed exceeding a preset value, and the duration for which the rate of change of the speed exceeds the preset value exceeding a preset duration.

[0015] Optionally, the wind turbine generator set is a large-megawatt wind turbine generator set, the single unit capacity of the wind turbine generator set is greater than or equal to 6 megawatts, the blades of the wind turbine generator set are long flexible blades, the length of the long flexible blades is greater than or equal to 85 meters, and the rotor diameter of the wind turbine generator set is greater than or equal to 175 meters.

[0016] A second aspect of this disclosure provides a control system for a wind turbine generator set, the control system comprising: at least one processor; and at least one memory storing computer-executable instructions, wherein the computer-executable instructions, when executed by the at least one processor, cause the at least one processor to perform a pitch control method for a wind turbine generator set as described in embodiments of this disclosure.

[0017] A third aspect of this disclosure provides a wind turbine generator set, the wind turbine generator set including a control system for the wind turbine generator set according to embodiments of this disclosure.

[0018] A fourth aspect of this disclosure provides a computer-readable storage medium that, when instructions in the computer-readable storage medium are executed by a processor of an electronic device, enables the electronic device to perform a pitch control method for a wind turbine generator according to embodiments of this disclosure.

[0019] A fifth aspect of this disclosure provides a computer program product including computer-executable instructions that, when executed by at least one processor, implement the pitch control method for a wind turbine generator according to embodiments of this disclosure.

[0020] According to the pitch control method, system, and wind turbine generator set disclosed herein, when the current output power of the wind turbine generator set reaches the rated power, different control strategies can be adopted according to the changing trend of the generator speed to control the blades of the unit to pitch. The control strategy may include a first control strategy that takes a preset power as the control target of the output power and a second control strategy that takes a preset torque as the control target of the generator torque. In this way, different control strategies can be adopted under different generator speed conditions, avoiding the problem of poor control effect of a single control strategy. By switching different control strategies, the unit can effectively reduce the load under the rated power, ensuring the safety and stability of the unit operation. Attached Figure Description

[0021] Figure 1 This is a schematic flowchart illustrating a pitch control method for a wind turbine generator set according to an exemplary embodiment of the present disclosure.

[0022] Figure 2 This is a timing diagram illustrating the output power of a wind turbine generator set under constant power control and constant torque control according to an exemplary embodiment of the present disclosure.

[0023] Figure 3 This is a timing diagram illustrating the tower base load of a wind turbine generator under constant power control and constant torque control according to an exemplary embodiment of the present disclosure.

[0024] Figure 4A This is a schematic block diagram illustrating a pitch control method for a wind turbine generator set according to an exemplary embodiment of the present disclosure.

[0025] Figure 4B This is a schematic diagram illustrating the determination of the speed change rate in a pitch control method for a wind turbine generator according to an exemplary embodiment of the present disclosure.

[0026] Figure 5 This is a schematic diagram illustrating the selection of optimal parameters for the timing of the output active power of a wind turbine generator set according to an exemplary embodiment of the present disclosure.

[0027] Figure 6 This is a schematic diagram illustrating the selection of optimal parameters for a wind turbine generator set by comparing the timing of the load at the base of the turbine tower, according to an exemplary embodiment of the present disclosure.

[0028] Figure 7 This is a schematic diagram illustrating the selection of the optimal power factor by comparing the output active power timing of a wind turbine generator set according to an exemplary embodiment of the present disclosure.

[0029] Figure 8 This is a schematic diagram illustrating the selection of the optimal power factor for a wind turbine generator set by comparing the timing of the load at the base of the turbine tower, according to an exemplary embodiment of the present disclosure.

[0030] Figure 9A , Figure 9B and Figure 9C This is a timing diagram illustrating a comparison example of the output active power of a wind turbine generator using a pitch control method, a constant power control method, and a constant torque control method according to exemplary embodiments of the present disclosure.

[0031] Figure 10A , Figure 10B and Figure 10C This is a timing diagram illustrating a comparison example of tower base load using a pitch control method, a constant power control method, and a constant torque control method for a wind turbine generator set according to exemplary embodiments of the present disclosure.

[0032] Figure 11 This is a schematic diagram illustrating comparative examples of tower base fatigue loads using a pitch control method, a constant power control method, and a constant torque control method for a wind turbine generator set according to exemplary embodiments of the present disclosure.

[0033] Figure 12A , Figure 12B , Figure 12C and Figure 12D This is a timing diagram illustrating a comparison example of hub center load using a pitch control method, a constant power control method, and a constant torque control method for a wind turbine generator set according to exemplary embodiments of the present disclosure.

[0034] Figure 13 This is a schematic diagram illustrating a comparative example of fatigue loads on key components of a wind turbine generator set employing a pitch control method, a constant power control method, and a constant torque control method according to exemplary embodiments of the present disclosure. Detailed Implementation

[0035] The following detailed embodiments are provided to aid the reader in gaining a comprehensive understanding of the methods, apparatus, and / or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will become apparent upon understanding this disclosure. For example, the order of operations described herein is merely illustrative and is not limited to those orders set forth herein, but may be changed as will become clear upon understanding this disclosure, except for operations that must occur in a specific order. Furthermore, for clarity and conciseness, descriptions of features known in the art may be omitted.

[0036] The features described herein may be implemented in different forms and should not be construed as limited to the examples described herein. Rather, the examples described herein are provided only to illustrate some of the many feasible ways of implementing the methods, apparatus, and / or systems described herein, which will become clear upon understanding the disclosure of this application.

[0037] As used herein, the term “and / or” includes any one of the associated listed items and any combination of any two or more.

[0038] Although terms such as “first,” “second,” and “third” may be used herein to describe various components, assemblies, regions, layers, or parts, these components, assemblies, regions, layers, or parts should not be limited by these terms. Rather, these terms are used only to distinguish one component, assembly, region, layer, or part from another. Thus, without departing from the teaching of the examples described herein, the first component, first assembly, first region, first layer, or first part referred to as the first component, first assembly, first region, first layer, or first part may also be referred to as the second component, second assembly, second region, second layer, or second part.

[0039] In the specification, when an element (such as a layer, region, or substrate) is described as being "on" another element, "connected to," or "bonded to" another element, the element may be directly "on" another element, directly "connected to," or "bonded to" the other element, or one or more other elements may be present in between. Conversely, when an element is described as being "directly on" another element, "directly connected to," or "directly bonded to" another element, no other elements may be present in between.

[0040] The terminology used herein is for the purpose of describing various examples only and is not intended to limit disclosure. Unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well. The terms “comprising,” “including,” and “having” indicate the presence of the described features, quantities, operations, components, elements, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.

[0041] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains upon understanding this disclosure. Unless expressly defined herein, terms (such as those defined in a general dictionary) shall be interpreted as having a meaning consistent with their meaning in the context of the relevant field and in this disclosure, and shall not be interpreted in an idealized or overly formalistic manner.

[0042] Furthermore, in the description of the examples, detailed descriptions of well-known related structures or functions will be omitted when it is believed that such detailed descriptions would lead to a vague interpretation of this disclosure.

[0043] As mentioned earlier, the pitch reduction schemes in related technologies are all designed for small-power units. They do not take into account the special characteristics of large-megawatt units during the control process. Therefore, they are difficult to apply to large-megawatt units, and even if they are applied to large-megawatt units, it is difficult to ensure the safety and stability of the units.

[0044] Specifically, in large-megawatt wind turbines, the blades are longer, with rotor diameters reaching 175m or even over 200m. Due to the longer blades, their flexibility is more pronounced; therefore, long, flexible blades are typically used in large-megawatt wind turbines. These blades are usually manufactured using a carbon-glass hybrid process. Long, flexible blades are more sensitive to wind speed; under the same wind speed variation, the load variation of long, flexible blades is greater than that of short blades, and this large load can severely impact the blade's lifespan. Furthermore, the towers of large-megawatt wind turbines are much taller, reaching over 170m. With the increased tower height, tower vibration, especially at the top, is greater, resulting in a significant increase in tower load and also severely affecting the lifespan of tall towers. Therefore, large-megawatt wind turbines require more attention to load management during operation compared to smaller turbines.

[0045] In addition, large-megawatt units have a larger installed capacity. Due to the larger base, compared with the small-power units of the past, the power fluctuation range of large-megawatt units is larger under the same power fluctuation percentage, which has a greater impact on the power grid and will seriously affect the grid adaptability.

[0046] Therefore, when large-megawatt wind turbine generators operate above the rated wind speed, it is necessary to ensure that the output power above the rated power point is stable and avoids fluctuations to improve grid friendliness; at the same time, it is necessary to keep the load on the key components of the unit within a controllable range to reduce the fatigue load on the unit and help extend the unit's lifespan.

[0047] However, in related technologies, variable speed constant frequency wind turbines mainly adopt variable pitch control technology. That is, when the wind speed is too high, the pitch angle is adjusted to change the power angle of the airflow on the blades, thereby changing the aerodynamic torque obtained by the unit, so as to keep the power output of the unit stable and reduce the wind load. However, it does not fundamentally propose how to reduce the load on the key components of the unit while ensuring the stable output power of large megawatt-level units.

[0048] In some control strategies, once the wind speed reaches the rated wind speed, the unit enters full-load operation. At this time, the pitch angle can be dynamically controlled to ensure that the unit operates stably at the rated speed, and the dynamic rated power output can be maintained according to constant power or constant torque control methods.

[0049] In the embodiments of this disclosure, through simulation calculations, it is found that constant power control and constant torque control each have their own advantages and disadvantages when the output power reaches or exceeds the rated power. For example, the output power of the unit is more stable under constant power control, while the load on the key components of the unit is smaller under constant torque control.

[0050] Specifically, when the on-site wind speed reaches the designed full-load wind speed of the wind turbine generator set, theoretically, both the rotational speed and power output are in a stable state. The basic control strategy for wind turbine generator sets can be: below the rated wind speed, speed control is achieved by controlling the generator torque to maintain the rotor speed at the optimal tip speed ratio, thus enabling the unit to capture wind energy with maximum efficiency; above the rated wind speed, the rotor speed is maintained at the rated speed by controlling the blade pitch angle, ensuring constant power output. This is because of the relationship T = Kopt × n. 2 Where T is the generator torque; n is the generator's current speed; and Kopt is the optimal gain value of the wind turbine generator set. Assuming stable power output, the generator speed is inversely proportional to the torque. Therefore, when the wind speed is above the rated wind speed, the unit is operating at full capacity, and constant power control or constant torque control can be used.

[0051] In constant power control, the rated power can be used as the control target, and the pitch angle can be adjusted by proportional-integral (PI) control, with torque T = P. rated / ω m , where P rated For output power, ω m This refers to real-time speed. In this control mode, the unit maintains a relatively constant output power at different speeds: at low speeds, the generator torque is higher; at high speeds, the generator torque decreases to maintain constant power. Therefore, under this control mode, the unit's output active power is relatively stable with less fluctuation, which is more friendly to the unit's converter and the power grid. However, since the unit uses stable power as the control objective, the torque fluctuation is relatively large, which increases the fatigue load on the unit and shortens its lifespan.

[0052] Constant power control is typically suitable for loads that need to maintain constant power over a wide speed range, or for scenarios with stricter grid connection requirements where large power fluctuations are not allowed and grid safety must be ensured.

[0053] In constant torque control, the rated speed can be used as the control target, and the pitch angle can be adjusted by pitch PI control, where torque T = P. rated / ω r , where ω r This refers to the rated speed. The generator set maintains a constant output torque at different speeds: theoretically, at low speeds, the output power decreases, while the generator torque increases according to P = K × ω × T. The control objective of constant torque control is relatively stable torque, meaning that regardless of the speed, the torque required by the generator load is the same. This results in smaller torque fluctuations, a lower load, and is more favorable for generator fatigue loads, thus extending the generator's lifespan. Under constant torque control, the proportion of problems with key components is lower. However, due to large power fluctuations, power may be over-generated, exceeding the rated power significantly. However, because the power grid has stricter requirements for generator output power, most generator sets employ constant power control.

[0054] Because constant power control and constant torque control each have their own shortcomings, they may not be able to meet the requirements of large megawatt units to achieve safe load reduction while ensuring stable power output.

[0055] In view of the above problems, this disclosure provides a pitch control method for a wind turbine generator set, a pitch control system for a wind turbine generator set, a wind turbine generator set, a computer-readable storage medium, and a computer program product to solve or at least alleviate the above problems.

[0056] According to a first aspect of an exemplary embodiment of the present disclosure, a pitch control method for a wind turbine generator is provided. This pitch control method can be executed by a computer device with computing capabilities, for example, by a computer device in the pitch control system of the wind turbine generator. The computer device executing the pitch control method can be, for example, a terminal device or a server, wherein the terminal device can be such as a tablet computer, a laptop computer, a digital assistant, etc.; the server can be a standalone server, a server cluster, a cloud computing platform, or a virtualization center.

[0057] Here, computer equipment can be installed at the wind turbine generator or wind farm, for example, and can be communicatively connected to the measuring device or data center of the wind turbine generator or wind farm, so as to obtain the data required to perform the above method.

[0058] In embodiments according to this disclosure, the pitch control method for wind turbine generator sets can be applied to large-megawatt wind turbine generator sets.

[0059] Here, large-megawatt wind turbine generators can differ from ordinary generators in terms of single-unit capacity, rotor diameter (or blade length), and tower height. For example, the single-unit capacity of a wind turbine generator can be greater than or equal to 6 megawatts, the blades of the wind turbine generator can be long flexible blades, the length of the long flexible blades can be greater than or equal to 85 meters, and the rotor diameter of the wind turbine generator can be greater than or equal to 175 meters.

[0060] In large-megawatt wind turbine generators, long flexible blades can be used, with lengths exceeding 100 meters. These blades can be made of a composite material of carbon fiber and glass fiber. Compared to traditional short blades, long flexible blades are more flexible, have less damping, and are more sensitive to wind loads. Even small changes in wind speed can cause large load fluctuations and deformation. Therefore, this control method is particularly suitable for generators with long flexible blades.

[0061] According to embodiments of this disclosure, the pitch control method may include the following steps:

[0062] like Figure 1 As shown, in step S110, the trend of the change in the generator speed of the wind turbine can be determined in response to the current output power of the wind turbine reaching the rated power.

[0063] As mentioned above, constant power control and constant torque control each have their own shortcomings, which may prevent them from meeting the requirements of large megawatt units to achieve safe load reduction while ensuring stable power output.

[0064] Simulation calculations were performed using a certain land-based turbine platform. The sub-condition (12-g condition) of the DLC12 operating mode with a wind speed of 14 m / s was selected. Taking the unit's output active power and the tower base load My as examples, the relationship between the timing diagram of the pitch control after reaching rated power and the generator speed is shown below. Figure 2 and Figure 3 As shown.

[0065] Depend on Figure 2 and Figure 3 It can be seen that by comparing the generator speed timing and output power timing and tower bottom load timing under the same operating conditions, it is found that when the generator speed increases or decreases, the unit output power and tower bottom load My fluctuate greatly, and the difference between the two is more obvious under constant power control and constant torque control.

[0066] Based on the above findings, in the embodiments of this disclosure, when the current output power of the wind turbine generator reaches its rated power, the changing trend of the generator speed of the wind turbine generator can be determined, thereby enabling targeted load reduction and power stabilization pitch control during periods of generator speed variation. Here, the changing trend can include both upward and downward trends.

[0067] In step S110, in one example, generator speed data from multiple moments within a predetermined time period (e.g., 3 seconds) prior to the current moment can be acquired. This generator speed data can be filtered to remove abrupt data points, resulting in filtered speed data. The generator's speed difference between each pair of adjacent data in the filtered speed data can be used to determine whether the generator is in an increasing or decreasing state within the predetermined time period. For example, if the speed difference is always greater than 0, the speed can be considered to be on an increasing trend; if the speed difference is always less than 0, the speed can be considered to be on a decreasing trend.

[0068] In another example, the trend of the generator speed of a wind turbine can also be determined by comparing the current measured generator speed with the preset generator speed to determine the speed difference; based on the speed difference, determining the rate of change of the speed difference; combining the speed difference and the rate of change of the speed difference to determine the speed change rate; and based on the speed change rate, determining the trend of the generator speed.

[0069] Here, the preset generator speed can be, for example, the rated generator speed, and the speed difference can be, for example, the overspeed percentage. Correspondingly, the rate of change of the speed difference can be, for example, the rate of change of the overspeed percentage. The overspeed percentage can be expressed as: Overspeed percentage = (Measured generator speed - Rated generator speed) / Rated generator speed × 100%. However, the embodiments of this disclosure are not limited to this, and the speed difference and its rate of change can also be expressed in other ways.

[0070] As an example, such as Figure 4A As shown, the measured generator speed can be compared with the preset generator speed. For example, the overspeed percentage can be obtained, and the overspeed percentage can be differentiated to obtain the rate of change of the overspeed percentage.

[0071] Fuzzy control, for example, can be used to determine whether the engine speed is increasing based on the overspeed percentage and the rate of change of the overspeed percentage. As an example, the logic design of fuzzy control could include: taking the overspeed percentage and the rate of change of the overspeed percentage as inputs to the fuzzy controller, and outputting the speed change rate to determine the trend of speed change. Figure 4B A schematic diagram of fuzzy control logic is shown. Input 1 and Input 2 of the fuzzy control are the overspeed percentage and the rate of change of the overspeed percentage, respectively. When either the overspeed percentage or the rate of change of the overspeed percentage (or the acceleration of the overspeed percentage) is less than 0, the rate of change of rotational speed is strictly equal to 0. Figure 4B As shown, the greater the percentage of overspeed and the rate of change of the percentage of overspeed, the greater the rate of change of rotational speed.

[0072] In one example, when both the overspeed percentage and its rate of change are greater than 0, it can be assumed that the rotational speed is trending upward.

[0073] In another example, the trend of generator speed change can be determined as follows: in response to the speed change rate meeting a preset condition, the generator speed is determined to be on an upward trend; in response to the speed change rate not meeting the preset condition, the generator speed is determined to be on a downward trend, wherein the preset condition includes: the speed change rate exceeds a preset value, and the duration of the speed change rate exceeding the preset value exceeds a preset duration.

[0074] Specifically, in this example, the engine speed change rate is considered to be in an upward trend only when it exceeds a preset value k and the duration exceeds a certain time, and a corresponding control logic switching signal is output.

[0075] In addition, to reduce unnecessary switching actions and protect the pitch actuator by minimizing pitch changes, dead-zone protection can be implemented on the speed change rate output by fuzzy calculation, limiting the speed change rate to a preset rate range (i.e., the aforementioned dead zone). For example, when multiple speed change rates are obtained in a time sequence, data outside the rate range can be removed, and the speed change rates within the rate range can be further judged, for example, compared with a preset value, to determine the speed change trend.

[0076] Furthermore, in the above example, the measured generator speed can be subjected to an asymmetric moving average filter, and the filtered speed data can be compared with the preset generator speed.

[0077] Furthermore, in the above example, to prevent abnormal calculation results due to other reasons, saturation calculations can be performed on the initial overspeed percentage and overspeed change rate (e.g., Figure 4A The saturation calculations 1 and 2 in the code can be used as inputs to the fuzzy control logic toolbox. Here, saturation calculation refers to a method of limiting the result to the maximum and minimum values ​​within a preset range when the result exceeds this range. This method avoids data overflow and ensures the correctness of the calculation results. For example, corresponding limit ranges can be preset for the overspeed percentage and the rate of change of the overspeed percentage. When the overspeed percentage or the rate of change of the overspeed percentage exceeds the corresponding limit range, the data can be corrected to that range.

[0078] However, the methods for determining the trend of speed change are not limited to the examples above; other mathematical or statistical methods can also be used to determine the trend of speed change.

[0079] In step S120, the blade pitch of the wind turbine can be controlled based on a control strategy corresponding to the changing trend.

[0080] In the examples disclosed herein, different trends of change can be distinguished, and different control strategies can be adopted. Here, for each trend of change, a corresponding control strategy can be preset.

[0081] Specifically, the control strategy may include a first control strategy and a second control strategy. The first control strategy may include: using a preset power as the control target for the output power of the wind turbine generator set, and controlling the blade pitch; for example, the first control strategy may be, but is not limited to, the existing constant power control. The second control strategy may include: using a preset torque as the control target for the torque of the wind turbine generator set, and controlling the blade pitch; for example, the second control strategy may be, but is not limited to, the existing constant torque control.

[0082] Here, the preset power can be, for example, the rated power of the unit, and the preset torque can be, for example, the torque given according to actual needs.

[0083] In one example, the blade pitch of a wind turbine can be controlled as follows: in response to an upward trend, the blade pitch is controlled based on a second control strategy; in response to a downward trend, the blade pitch is controlled based on a first control strategy. According to embodiments of this disclosure, employing constant torque control during the speed increase and constant power control during the speed decrease can achieve better control performance.

[0084] Under both control strategies, the pitch angle of each blade (e.g., blade 1, blade 2, and blade 3) can be obtained, and a reference pitch angle can be obtained through the pitch loop PID controller, which is then provided to the generator unit for pitch control. In the first control strategy, after pitch control, the measured power can be obtained and compared with the rated power to achieve constant power control; in the second control strategy, after pitch control, the measured generator speed can be obtained to calculate the current generator torque and compare it with the preset torque to achieve constant torque control.

[0085] By combining the advantages of constant power control and constant torque control in the full-load phase of wind turbine generator sets, the adaptive switching between constant power control and constant torque control can be achieved, reducing the fatigue load of wind turbine generator sets in the full-load phase (mainly including tower load and hub center load, which will be described in detail below), and maintaining power stability as much as possible.

[0086] Furthermore, based on the aforementioned adaptive switching control method, in order to optimize the control implementation as much as possible and avoid control response delay or control parameter errors caused by switching control strategies, according to embodiments of this disclosure, a parameter design for switching between different control strategies is also provided.

[0087] Specifically, the pitch control method may further include: in response to a change in the trend of change, switching between a first control strategy and a second control strategy by adjusting preset minimum torque coefficient, maximum torque coefficient and switching power coefficient, wherein the minimum torque coefficient and maximum torque coefficient can be used to determine the control target of the generator torque, and the switching power coefficient can be used to determine the control target of the wind turbine generator output power.

[0088] Here, common control coefficients can be designed for different control strategies, allowing switching between control strategies to be achieved by adjusting the setpoints of these control coefficients. Specifically, this can be done by modifying the propeller loop PID controller and adding three control parameters: minimum torque coefficient P... min Maximum torque coefficient P max and switching power factor P pwdF This enables adaptive adjustment of strategies based on the unit's operating conditions, i.e., switching between constant power and constant torque control.

[0089] As an example, the first control strategy can be switched to as follows: the minimum torque coefficient is adjusted to be within the minimum coefficient range, the maximum torque coefficient is adjusted to be within the maximum coefficient range, and the switching power coefficient is adjusted to the preset power coefficient, wherein the minimum torque coefficient is less than the maximum torque coefficient.

[0090] Specifically, during the constant power control phase, the power control target can be set by adjusting the switching power coefficient to the preset power coefficient. Here, since the embodiments of this disclosure are specifically for large-megawatt wind turbine generator sets, and the blades of large-megawatt generator sets are longer and more flexible, and the towers are higher, the load changes of large-megawatt generator sets are greater under the same wind speed changes, which will seriously affect the fatigue load of the generator set. Therefore, it is necessary to limit the range of generator torque changes and reduce the fluctuation of generator torque.

[0091] According to P = K × ω × T, where P is the real-time power, K is a constant, ω is the real-time speed, and T is the torque, it can be seen that the speed and torque are inversely proportional. When the speed ω increases, the torque T decreases, and similarly, when the speed ω decreases, the torque T increases. In order to avoid T being too small and causing accidents due to being less than the load torque, and to avoid T being too large and causing accidents, it is necessary to set a minimum torque coefficient and a maximum torque coefficient to limit the range of torque.

[0092] Here, the minimum torque coefficient and the maximum torque coefficient can be selected from preset minimum and maximum coefficient ranges, respectively. For example, the lower limit of the generator torque can be set to a preset torque of 'a' times and the upper limit to a preset torque of 'b' times, then the minimum torque coefficient P... min and maximum torque coefficient P max It can satisfy a < P min <P max <b.

[0093] As an example, for large-megawatt units, since the unit operates at full capacity, theoretically the speed and power are at their rated levels, and therefore the torque remains constant. To prevent torque jumps from causing excessive power fluctuations, which could affect the load on key components of the unit, a ±10% fluctuation margin can be reserved based on experience in judging the stability of large-megawatt units. That is, a = 90% to 100% or a = 0.9 to 1, b = 100% to 110% or b = 1 to 1.1.

[0094] Specifically, the minimum coefficient range can be: 0.9 < P min ≤1; the maximum coefficient range can be: 1≤P max <1.1, and P min <P max .

[0095] In embodiments of this disclosure, the switching power factor P can be utilized. pwdF The control target for output power is obtained by weighting the rated power. Here, in the constant power control stage, the control target for output power can be, for example, the rated power. In this case, the power will remain stable, and the switching power coefficient P... pwdF It can be 1, while torque will fluctuate, which can be kept within ±10%, for example, by using the minimum torque coefficient P. min >0.9, maximum torque coefficient P max <1.1.

[0096] In addition, the second control strategy can be implemented by adjusting both the minimum torque coefficient and the maximum torque coefficient to the preset torque coefficient, and adjusting the switching power coefficient to be within the power coefficient range, wherein the lower limit of the power coefficient range is greater than the preset power coefficient, the preset torque coefficient is greater than or equal to the upper limit of the minimum coefficient range, and less than or equal to the lower limit of the maximum coefficient range.

[0097] Specifically, during the constant torque control phase, constant torque control can be achieved by adjusting the minimum torque coefficient and the maximum torque coefficient to the same value, so that the generator torque control target is that value. For example, P can be set... min =P max =1.

[0098] Here, since the embodiments of this disclosure are specifically targeted at large-megawatt wind turbine generators, and large-megawatt generators have a larger installed capacity, their power fluctuation range is greater than that of small-power generators at the same power fluctuation percentage due to the larger base. This will have a greater impact on the power grid and seriously affect grid adaptability. Therefore, it is necessary to limit the power fluctuation range. Therefore, the power factor P can be switched by design. pwdFThis coefficient is equivalent to a safety protection coefficient. It is set to prevent the power grid from being impacted by excessive active power output under gusts of wind when the unit switches to constant torque operation.

[0099] In large-megawatt wind turbine generators, to prevent power surges from impacting the power grid, a +15% upward ripple margin can be reserved based on grid adaptability experience. Specifically, this can satisfy c≤P. pwdF <d, where c = 100% or c = 1, and d = 100% to 115% or d = 1 to 1.15. As an example, the switching power factor P can be set. pwdF =1.1.

[0100] Furthermore, according to embodiments of this disclosure, the pitch control method may further include: in response to the current output power of the wind turbine being less than a preset power limit, performing a step of determining the changing trend of the generator speed of the wind turbine; and in response to the current output power of the wind turbine being greater than or equal to the power limit, controlling the blades to pitch based on a first control strategy. Here, the power limit may be determined based on a switching power coefficient and the rated power of the wind turbine.

[0101] Specifically, when the unit determines that the output power exceeds the power limit (e.g., P), pwdF After reaching the rated power, a forced switch to the first control strategy can be initiated, such as switching to constant power control, to maintain power stability. Afterward, the generator speed can be continuously acquired, and the switch can be re-evaluated based on changes in generator speed; this coefficient remains unchanged after the switch. Therefore, it can be seen that this coefficient P only changes when the unit is in the second control strategy (e.g., constant torque control). pwdF This is what works to prevent power surges that could impact the power grid, for example, when 1 < P. pwdF <1.5.

[0102] As described above, in order to combine the advantages of constant power and constant torque control, the embodiments of this disclosure can employ an adaptive control method of semi-constant power / constant torque control to reduce fatigue load without over-generating the unit's output power. Regarding the implementation of adaptive control, the embodiments of this disclosure design three coefficients to facilitate switching between different control strategies.

[0103] Here, as an example, the advantages of combining constant power control and constant torque control can be achieved by optimizing each coefficient within the aforementioned coefficient range (e.g., minimum coefficient range, maximum coefficient range, and power coefficient range). During the optimization process, separate simulation tests are required for different turbine models. Simulations can be performed on parameters such as blade and tower configurations for each model to obtain the optimal coefficient selection corresponding to each model. Table 1 below provides examples of different combinations of the above three coefficient settings. However, the values ​​of the coefficients in Table 1 are only examples, and the values ​​of one or more of these coefficients can be modified according to actual needs.

[0104] Table 1

[0105]

[0106] According to embodiments of this disclosure, a pitch control method applicable to the full-load range of wind turbine generators and combining the advantages of constant power and constant torque control can be provided. By designing control parameters, adaptive switching between constant power and constant torque control is achieved, avoiding the use of pure constant power or pure constant torque control. Thus, on the one hand, the generator's output active power is more stable and over-generation is reduced compared to single constant torque control, making it more grid-friendly; on the other hand, the fatigue loads on key generator components (especially hub center Mx load, blade root My load, tower top Mx load, yaw Mx load, and tower bottom My load) are lower than with single constant power control, making it more fatigue-resistant. Through these improvements, the control method of the embodiments of this disclosure can reduce fatigue loads on key generator components and extend generator life while ensuring the safety of the generator and the grid.

[0107] Figure 5 and Figure 6 Schematic diagrams comparing output power and tower load under two adaptive switching control methods based on a certain onshore platform are shown. Specifically, based on a certain onshore unit platform, the unit's output active power and tower base load My are compared. Controller parameters are set for the two adaptive switching combinations in Table 1 below, as well as pure constant power control and pure constant torque control. Simulations are conducted under the same normal turbulent wind conditions at a sub-condition of 14 m / s (condition 12-g) in DLC12, and the verification results are as follows. Figure 5 and Figure 6 As shown in the attached figure. The coefficient P mentioned above is... pwdF It is also represented by PF.

[0108] Depend on Figure 5 and Figure 6 Therefore, choosing P min =0.95, P max =1 (i.e., constant torque control is used when the speed increases, and constant power control is used when the speed decreases), compared to P min =1, Pmax =1.06 (that is, constant power control is used when the speed increases and constant torque control is used when the speed decreases), the unit output active power is relatively stable, the over-generation is small, and the My load at the bottom of the tower is better.

[0109] Based on Table 1, regarding parameter P pwdF Similarly, the parameter comparison results are as follows: Figure 7 and Figure 8 As shown.

[0110] Depend on Figure 7 and Figure 8 Therefore, choosing P pwdF =1 (that is, when the unit is under constant torque control and the current output active power equals the rated power, it switches to constant power control), compared to P pwdF =1.2 (that is, when the unit is under constant torque control and the current output active power is 1.2 times the rated power, it switches to constant power control). The unit's output active power is relatively stable, with less over-generation, and the load My at the bottom of the tower is smaller.

[0111] In summary, the constant power / constant torque adaptive switching control parameters can be selected as follows: (1) Minimum torque coefficient P of the unit during operation min =0.95; (2) Maximum operating torque coefficient P of the unit max =1; (3) Power coefficient P for switching control mode in full-load segment pwdF =1.

[0112] It should be noted that the coefficient selection results here are based only on the simulation results of a specific aircraft platform, and the parameter selection conclusions obtained cannot represent all aircraft models. Due to differences in blade and tower configurations among different aircraft models, the optimal parameter selections vary, requiring separate simulation tests for each model. The simulation results are only used as examples to demonstrate that the adaptive switching method according to the embodiments of this disclosure can combine the advantages of constant power / constant torque.

[0113] Furthermore, based on the above parameter selection, simulations were conducted under the same 12-g operating condition and normal turbulent wind conditions to compare the active power output of the unit and the My load at the tower base under constant power, constant torque, and adaptive switching control. Figure 9A , Figure 9B and Figure 9C As shown.

[0114] Figure 9A The diagram shows the output active power timing under constant power, constant torque, and adaptive switching control, respectively. Figure 9A As shown, the adaptive switching control method proposed in this disclosure can reduce over-generation of the unit by relative constant torque control, making the output active power relatively stable and more grid-friendly.

[0115] Here, for all operating conditions of DLC12, from the cut-in wind speed to the cut-out wind speed, the unit's output active power under constant power, constant torque, and adaptive switching control is statistically analyzed, and the results are as follows. Figure 9B and Figure 9C ,in, Figure 9B The maximum active power (DLC12) is shown under constant power, constant torque, and adaptive switching control, respectively. Figure 9C The standard deviation of active power (DLC12) is shown under constant power, constant torque, and adaptive switching control.

[0116] like Figure 9B and Figure 9C As shown, when the unit is under adaptive switching control, at various wind speeds during the full-load range (wind speed between 12m / s and 20m / s), on the one hand, the maximum active power is less than that under constant torque control, and close to that under constant power control; on the other hand, the standard deviation of active power is less than that under constant torque control, and close to that under constant power control. This proves that under adaptive switching control, there is less over-generation and less fluctuation in output power, which is beneficial to unit safety and more grid-friendly, inheriting the advantages of constant power control.

[0117] Furthermore, the load My at the bottom of the tower can be compared under constant power, constant torque, and adaptive switching control. For example... Figure 10A As shown, the adaptive switching control method proposed in this disclosure can reduce the load My at the bottom of the tower compared with constant power control, which is more friendly to the fatigue load of the tower and helps to extend the service life of the tower.

[0118] Here, for the DLC12 operating conditions, from the cut-in wind speed to the cut-out wind speed, the load My at the base of the unit under constant power, constant torque, and adaptive switching control is statistically analyzed, and the results are as follows: Figure 10B and Figure 10C ,in, Figure 10B The maximum load value of My at the bottom of the tower (DLC12) is shown under constant power, constant torque, and adaptive switching control, respectively. Figure 10C The standard deviation of the load My at the bottom of the tower is shown (DLC12) under constant power, constant torque, and adaptive switching control.

[0119] like Figure 10B and Figure 10CAs shown, when the unit is under adaptive switching control, at various wind speeds during full-load operation (wind speed between 12 m / s and 20 m / s), on the one hand, the maximum value of the tower base load My is smaller than that under constant power control, and is close to that under constant torque control; on the other hand, the standard deviation of the tower base load My is smaller than that under constant power control, and is close to that under constant torque control. This proves that the tower base load My is smaller and fluctuates less under adaptive switching control, which is more favorable for tower fatigue load, helps extend the unit's lifespan, and can inherit the advantages of constant torque control.

[0120] Furthermore, the results of comparing the fatigue load of the tower base My under constant power, constant torque, and adaptive switching control can be as follows: Figure 11 As shown. Figure 11 As shown, based on the current parameters of the blades and tower, the constant power / constant torque adaptive switching control proposed in this disclosure can reduce the fatigue load of the tower bottom My by about 5%.

[0121] Figure 12A The diagram shows the timing sequence of the load Mx at the hub center under constant power, constant torque, and adaptive switching control, respectively. Figure 12A As shown, the adaptive switching control, compared with constant power control, can reduce the load on the hub center Mx, which is more friendly to the hub fatigue load and helps to extend the spindle life.

[0122] Here, for all operating conditions of DLC12, from the cut-in wind speed to the cut-out wind speed, the load Mx at the turbine hub center under constant power, constant torque, and adaptive switching control is statistically analyzed, and the results are as follows: Figures 12B to 12D As shown, where, Figure 12B The maximum load (DLC12) at the hub center is shown under constant power, constant torque, and adaptive switching control. Figure 12C The average load (DLC12) at the hub center Mx is shown under constant power, constant torque, and adaptive switching control, respectively. Figure 12D The standard deviation of the load Mx at the hub center (DLC12) is shown under constant power, constant torque, and adaptive switching control, respectively.

[0123] like Figures 12B to 12DAs shown, when the unit is under adaptive switching control, at various wind speeds during full-load operation (wind speed between 12m / s and 20m / s), firstly, the maximum value of the hub center Mx load is less than that under constant power control, and close to that under constant torque control; secondly, the mean value of the hub center Mx load is less than that under both constant power and constant torque control; and thirdly, the standard deviation of the hub center Mx load is less than that under constant power control, and close to that under constant torque control. This demonstrates that the hub center Mx load is smaller and fluctuates less under adaptive switching control, which is more favorable for hub fatigue load, helps extend spindle life, and inherits the advantages of constant torque control.

[0124] Figure 13 A comparison of fatigue loads on key components of the unit under constant power / constant torque / adaptive switching control is shown. Figure 13 In the red box (hub center Mx, blade root My, tower top Mx, yaw Mx, tower bottom My), the load reduction effect is more obvious. In addition, it also has a load reduction effect in other directions.

[0125] Specifically, taking the fatigue load My at the bottom of the tower as an example, the fatigue load My at the bottom of the tower is compared under constant power, constant torque, and adaptive switching control, such as... Figure 13 As shown in the last figure, based on the current parameters of the blades and tower, the constant power / constant torque adaptive switching control method proposed in this disclosure can reduce the fatigue load My at the bottom of the tower by about 5%.

[0126] As mentioned above, choose P. min =0.95, P max =1 (i.e., constant torque control is used when the speed increases, and constant power control is used when the speed decreases), compared to P min =1, P max =1.06 (i.e., constant power control is used when the speed increases, and constant torque control is used when the speed decreases), the unit's output active power is relatively stable, over-generation is small, and the load at the tower bottom My is better. Additionally, P is selected. pwdF =1 (When the unit is under constant torque control and the current output active power equals the rated power, switch to constant power control), compared to P pwdF =1.2 (When the unit is under constant torque control and the current output active power is 1.2 times the rated power, it switches to constant power control). The unit's output active power is relatively stable, with less over-generation, and the load My at the tower base is smaller. Furthermore, in the above simulation results diagram, the intention is to compare the differences between different control strategies; therefore, the specific units or values ​​of each horizontal and vertical axis are not indicated.

[0127] As can be seen from the above simulation analysis, switching between constant power and constant torque when the speed changes can prevent the wind turbine from outputting too much active power, which could lead to over-generation or even damage to the converter, and improve grid friendliness. At the same time, it can reduce the fatigue load on key components of the unit and extend the life of the unit. It combines the advantages of constant power control and constant torque control. Furthermore, by modifying the controller to set three sets of coefficients and setting the action range of the parameters, the constant power / constant torque adaptive switching of the unit can be achieved.

[0128] According to a second aspect of the embodiments of the present disclosure, a control system for a wind turbine generator is provided, the control system comprising: at least one processor; and at least one memory storing computer-executable instructions, wherein the computer-executable instructions, when executed by the at least one processor, cause the at least one processor to perform a pitch control method for a wind turbine generator as described in the embodiments of the present disclosure.

[0129] The control system may include computer equipment; specifically, the pitch control method of the wind turbine generator described above can be executed by computer equipment.

[0130] As an example, a computer device can be a PC, tablet, personal digital assistant, smartphone, or other device capable of executing the aforementioned set of instructions. Here, a computer device is not necessarily a single electronic device, but can be any collection of devices or circuits capable of executing the aforementioned instructions (or instruction sets) individually or in combination. A computer device can also be part of an integrated control system or system manager, or can be configured to interface with a portable electronic device locally or remotely (e.g., via wireless transmission).

[0131] In computer devices, a processor may include a central processing unit (CPU), a graphics processing unit (GPU), a programmable logic device, a dedicated processor system, a microcontroller, or a microprocessor. By way of example and not limitation, a processor may also include an analog processor, a digital processor, a microprocessor, a multi-core processor, a processor array, a network processor, etc.

[0132] The processor can execute instructions or code stored in memory, which can also store data. Instructions and data can also be sent and received over a network via a network interface device, which can employ any known transport protocol.

[0133] Memory can be integrated with the processor; for example, RAM or flash memory can be housed within an integrated circuit microprocessor. Alternatively, memory can comprise a separate device, such as an external disk drive, storage array, or other storage device that can be used by any database system. Memory and processor can be operatively coupled, or can communicate with each other, for example, via I / O ports, network connections, etc., enabling the processor to read files stored in the memory.

[0134] In addition, computer equipment may include video displays (such as liquid crystal displays) and user interaction interfaces (such as keyboards, mice, touch input devices, etc.). All components of a computer device may be interconnected via buses and / or networks.

[0135] According to a third aspect of the embodiments of the present disclosure, a wind turbine generator set is provided, the wind turbine generator set including a control system for the wind turbine generator set according to the embodiments of the present disclosure.

[0136] According to a fourth aspect of the embodiments of the present disclosure, a computer-readable storage medium is provided that, when instructions in the computer-readable storage medium are executed by a processor of an electronic device, enables the electronic device to perform a pitch control method for a wind turbine generator according to embodiments of the present disclosure.

[0137] Specifically, the pitch control method for a wind turbine generator set according to embodiments of the present disclosure can be programmed into a computer program and stored on a computer-readable storage medium. When the instructions in the computer-readable storage medium are executed by at least one processor, the at least one processor is caused to perform the pitch control method for the wind turbine generator set according to exemplary embodiments of the present disclosure. Examples of computer-readable storage media include: read-only memory (ROM), random access programmable read-only memory (PROM), electrically erasable programmable read-only memory (EEPROM), random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), flash memory, non-volatile memory, CD-ROM, CD-R, CD+R, CD-RW, CD+RW, DVD-ROM, DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-RAM, BD-ROM, BD-R, BD-R LTH, BD-RE, Blu-ray or optical disc storage, hard disk drive (HDD), solid-state drive (SSD), card storage (such as multimedia cards, secure digital (SD) cards, or ultra-fast digital (XD) cards), magnetic tape, floppy disk, magneto-optical data storage device, optical data storage device, hard disk, solid-state drive, and any other device configured to store a computer program and any associated data, data files, and data structures in a non-transitory manner and to provide the computer program and any associated data, data files, and data structures to a processor or computer so that the processor or computer can execute the computer program. In one example, the computer program and any associated data, data files, and data structures are distributed across a networked computer system, such that the computer program and any associated data, data files, and data structures are stored, accessed, and executed in a distributed manner through one or more processors or computers.

[0138] According to a fifth aspect of the embodiments of the present disclosure, a computer program product is provided, comprising computer-executable instructions that, when executed by at least one processor, implement the pitch control method for a wind turbine generator according to the embodiments of the present disclosure.

[0139] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0140] Furthermore, it should be noted that although several examples of each step have been described above with reference to the specific accompanying drawings, it should be understood that the embodiments of this disclosure are not limited to the combinations given in the examples. The steps appearing in different drawings can be combined, and the execution order of each step can be changed, which will not be exhaustive here.

[0141] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

[0142] The specific embodiments of this disclosure have been described in detail above. Although some embodiments have been shown and described, those skilled in the art should understand that modifications and variations can be made to these embodiments without departing from the principles and spirit of this disclosure, which are defined by the claims and their equivalents. Such modifications and variations should also be within the protection scope of the claims of this disclosure.

Claims

1. A method of pitch control of a wind turbine, characterized in that, The variable pitch control method comprises: in response to the current output power of the wind turbine generator reaching a rated power, determining a change trend of a generator speed of the wind turbine generator; controlling a blade pitch of the wind turbine generator based on a control strategy corresponding to the change trend, wherein different change trends correspond to different control strategies, and the control strategies comprise a first control strategy and a second control strategy, the first control strategy comprises: taking a preset power as a control target of the output power of the wind turbine generator to control the blade pitch, the second control strategy comprises: taking a preset torque as a control target of the torque of the generator of the wind turbine generator to control the blade pitch.

2. The pitch control method of claim 1, wherein, The blade pitch of the wind turbine generator is controlled in the following manner: in response to the change trend being an upward trend, the blade pitch is controlled based on the second control strategy; in response to the change trend being a downward trend, the blade pitch is controlled based on the first control strategy.

3. The pitch control method according to claim 1 or 2, characterized in that, The variable pitch control method further comprises: in response to the change trend changing, switching between the first control strategy and the second control strategy by adjusting preset minimum torque coefficients, maximum torque coefficients and switching power coefficients, wherein the minimum torque coefficients and the maximum torque coefficients are used to determine the control target of the torque of the generator, and the switching power coefficients are used to determine the control target of the output power of the wind turbine generator.

4. The pitch control method of claim 3, wherein, The first control strategy is switched to in the following manner: the minimum torque coefficients are adjusted to be within a minimum coefficient range, the maximum torque coefficients are adjusted to be within a maximum coefficient range, and the switching power coefficients are adjusted to be preset power coefficients, wherein the minimum torque coefficients are less than the maximum torque coefficients.

5. The pitch control method of claim 4, wherein, The second control strategy is executed in the following manner: the minimum torque coefficients and the maximum torque coefficients are both adjusted to be preset torque coefficients, and the switching power coefficients are adjusted to be within a power coefficient range, wherein a lower limit value of the power coefficient range is greater than the preset power coefficients, the preset torque coefficients are greater than or equal to an upper limit value of the minimum coefficient range, and less than or equal to a lower limit value of the maximum coefficient range.

6. The pitch control method of claim 5, wherein, The variable pitch control method further comprises: in response to the current output power of the wind turbine generator being less than a preset power limit value, the step of determining the change trend of the generator speed of the wind turbine generator is performed; in response to the current output power of the wind turbine generator being greater than or equal to the power limit value, the blade is controlled to pitch based on the first control strategy, wherein the power limit value is determined based on the switching power coefficients and the rated power of the wind turbine generator.

7. The pitch control method of claim 1, wherein, The change trend of the generator speed of the wind turbine generator is determined in the following manner: comparing a current measured generator speed with a preset generator speed to determine a speed difference; based on the speed difference, a speed difference change rate is determined; based on the speed difference and the speed difference change rate, a speed change rate is determined; based on the speed change rate, the change trend of the generator speed is determined.

8. The pitch control method of claim 7, wherein, A trend of the generator speed is determined by: in response to the speed change rate satisfying a preset condition, determining that the generator speed is in an ascending trend; in response to the speed change rate not satisfying the preset condition, determining that the generator speed is in a descending trend, wherein the preset condition comprises that the speed change rate exceeds a preset value, and a duration that the speed change rate exceeds the preset value exceeds a preset time length.

9. The pitch control method of claim 1, wherein, The wind turbine generator set is a large-megawatt wind turbine generator set, a single-machine capacity of the wind turbine generator set is greater than or equal to 6 megawatts, a blade of the wind turbine generator set is a long and soft blade, a length of the long and soft blade is greater than or equal to 85 meters, and a impeller diameter of the wind turbine generator set is greater than or equal to 175 meters.

10. A control system for a wind power plant, characterized in that The control system comprises: at least one processor; at least one memory storing computer-executable instructions, wherein the computer-executable instructions, when executed by the at least one processor, cause the at least one processor to perform the variable pitch control method of the wind turbine generator set according to any one of claims 1 to 9.

11. A wind power unit, characterized in that The wind turbine generator set comprises the control system of the wind turbine generator set according to claim 10.

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