A wind-rectifying system and method for a single-point mooring offshore floating wind turbine based on independent variable-pitch control

Abstract

The application discloses a single-point mooring offshore floating wind turbine wind-rectifying system and method based on independent variable-pitch control, which measures the deviation angle between the inflow wind direction angle and the platform first-rolling angle in real time, combines platform motion state parameters, and generates independent variable-pitch instructions by using a PID and fuzzy logic combined control algorithm of a controller to drive differential variable-pitch of each blade, actively generate a rectifying torque, and make the single-point mooring floating wind turbine improve the wind-rectifying efficiency and eliminate the wind-rectifying deviation angle. The application solves the problems of low wind-rectifying efficiency and large yaw angle deviation of the single-point mooring floating wind turbine under wind-wave-flow different directions, and improves the wind energy capturing efficiency by independent variable-pitch control while retaining the original structure and equipment of the floating wind turbine system.

Description

Technical Field

[0001] This invention belongs to the field of floating wind power technology, specifically relating to a single-point mooring offshore floating wind turbine wind steering system and method based on independent pitch control. Background Technology

[0002] While traditional stationary offshore wind turbines are well-established in nearshore waters, their application is limited by the dramatic increase in construction and maintenance costs as water depth increases. Floating offshore wind turbines, on the other hand, do not rely on seabed foundations and can be deployed more flexibly in deep-sea areas. Connected to the seabed via floating platforms and mooring systems, they reduce requirements on terrain and water depth, making them a crucial option for deep-sea wind energy development and representing a cutting-edge field of wind energy research. However, frequent failures of traditional turbine nacelle yaw systems not only reduce power generation efficiency but also lead to extremely high operation and maintenance costs. The reliability of yaw control systems has gradually become a major bottleneck for floating offshore wind turbines. In recent years, single-point mooring technology has been increasingly applied to floating wind turbines. By eliminating the traditional nacelle yaw system, the floating platform can spontaneously and passively adjust its direction according to changes in wind, waves, and currents. However, due to the influence of complex wind, wave, and current conditions, single-point moored turbines have lower wind efficiency. Furthermore, in complex marine environments, single-point moored floating offshore wind turbines often fail to fully align with the wind direction due to the inflow angle between wind, waves, and currents. Therefore, improving the wind-correcting and navigation capabilities of single-point moored offshore floating wind turbines is an urgent problem to be solved. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a single-point mooring offshore floating wind turbine wind steering system and method based on independent pitch control. By generating steering torque through differentiated independent pitch control, it achieves rapid and accurate wind steering while maintaining maximum power generation, effectively replacing the traditional yaw system, reducing operation and maintenance costs and improving system reliability.

[0004] To achieve the above objectives, the present invention provides the following solution: A single-point moored offshore floating wind turbine wind correction system based on independent pitch control includes: a deviation angle measurement subsystem, a control system, and a pitch execution subsystem; the deviation angle measurement subsystem is used to measure the deviation angle between the inflow wind direction angle and the platform's roll angle; the controller generates wind turbine pitch command signals using a control algorithm based on the deviation angle and the platform's motion state; the pitch execution subsystem is used to execute the commands, driving differentiated pitch control of each blade to generate a correction torque.

[0005] Preferably, the real-time deviation angle measurement subsystem includes an anemometer mounted on the top of the nacelle and a gyroscope mounted inside the platform compartment; wherein, the anemometer is used to measure the inflow wind direction angle. Gyroscopes and accelerometers are used to measure... Initial rocking angular velocity .

[0006] Preferably, the controller is based on the wind deviation angle. The system monitors the platform's motion status and uses a dual-mode control algorithm combining PID and fuzzy logic to calculate the target pitch angle compensation value for each blade in real time, and then outputs control commands.

[0007] Preferably, the pitch control subsystem includes: pitch controller, pitch bearing, reduction gearbox, servo motor, encoder and backup power supply, which independently adjusts the pitch angle of each blade after receiving instructions from the control system.

[0008] As a preferred option, when the deviation angle When the thrust is greater than 0, the blades reduce the pitch angle to increase thrust when they are in the right half of the rotor disk, and increase the pitch angle to decrease thrust when they are in the left half of the rotor disk, generating a leftward steering torque. When the deviation angle When the pitch angle is less than 0, the blades increase the pitch angle to reduce thrust when they are in the right half of the rotor disk, and decrease the pitch angle to increase thrust when they are in the left half of the rotor disk, generating a rightward steering torque.

[0009] As a preferred option, the wind speed-direction instrument uses an ultrasonic sensor; the gyroscope uses a fiber optic gyroscope; the central controller S142 uses an industrial-grade PLC; and the pitch actuator subsystem uses an electric pitch mechanism.

[0010] This invention also provides a method for single-point mooring offshore floating wind turbines to navigate and correct wind direction based on independent pitch control, comprising: Measure the deviation angle between the inflow wind direction angle and the platform's initial roll angle; If the absolute value of the deviation angle is greater than the preset threshold (usually 5°), the pitch angle of each blade is adjusted differently according to the sign of the deviation angle and the blade azimuth angle to generate a steering torque; the deviation angle is brought close to zero through closed-loop control.

[0011] As a preferred method, the specific way to adjust the pitch angle differentially is as follows: when the deviation angle is positive (the downstream of the inflow is biased towards the left half of the rotor disk), decrease the pitch angle of the blades on the right half of the rotor disk and increase the pitch angle of the blades on the left half of the rotor disk; when the deviation angle is negative (the downstream of the inflow is biased towards the right half of the rotor disk), increase the pitch angle of the blades on the right half of the rotor disk and decrease the pitch angle of the blades on the left half of the rotor disk.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Simplified structure and reduced cost: The steering is achieved through independent pitch control and single-point mooring, eliminating the need for a traditional yaw system, reducing engine room weight, and lowering manufacturing and maintenance costs.

[0013] 2. Dynamic response and improved accuracy: The closed-loop control of the floating body motion parameters improves the convergence speed of the wind deviation angle, especially under the condition of wind-wave-current anisotropy, effectively converging the final wind deviation angle, with significant advantages.

[0014] 3. Power generation efficiency optimization: Maintain the power balance pitch angle benchmark during navigation correction to ensure that the wind energy capture efficiency loss is controlled within 5%, thereby achieving synergistic optimization of navigation correction and power generation.

[0015] 4. Strong robustness: The dual-mode control strategy adapts to complex sea state changes, and the system can operate stably under turbulent wind conditions below 20%. Attached Figure Description

[0016] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the single-point mooring offshore floating wind turbine wind steering system based on independent pitch control according to the present invention. Figure 2 A flowchart for wind-correction control; Figure 3 This is the controller signal processing logic diagram; Figure 4 This is a schematic diagram illustrating the time-series changes of the three blades of a wind turbine under the control method of the present invention; Figure 5 This diagram illustrates the wind resistance effect of the method of the present invention compared to that of the conventional method. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1As shown, this invention provides a single-point mooring offshore floating wind turbine wind correction system based on independent pitch control, comprising: a deviation angle measurement subsystem, a control system, and a pitch execution subsystem; the deviation angle measurement subsystem is used to measure the deviation angle between the inflow wind direction angle and the platform's pitch angle; the controller generates wind turbine pitch command signals using a control algorithm based on the deviation angle and the platform's motion state; the pitch execution subsystem is used to execute the command, driving differentiated pitch control of each blade to generate correction torque.

[0021] Furthermore, the real-time deviation angle measurement subsystem includes an anemometer mounted on the top of the nacelle and a gyroscope mounted inside the platform compartment; wherein, the anemometer measures the inflow wind direction angle. Gyroscopes and accelerometers are used for measurement. Initial rocking angular velocity The aforementioned inflow wind direction angle With the platform's first angle The difference forms the wind deviation angle .

[0022] Furthermore, the controller is based on the wind deviation angle. The system monitors the platform's motion status and uses a dual-mode control algorithm combining PID and fuzzy logic to calculate the target pitch angle compensation value for each blade in real time, and then outputs control commands.

[0023] Furthermore, the pitch control subsystem includes: pitch controller, pitch bearing, reduction gearbox, servo motor, encoder and backup power supply, which independently adjusts the pitch angle of each blade after receiving commands from the control system.

[0024] An example of a wind-alignment system for a single-point moored offshore floating wind turbine based on independent pitch control is applied to a 5MW single-point moored floating wind turbine S1. The single-point moored floating wind turbine includes: a rotor S15, a nacelle S14, a tower S13, a platform S11, and a single-point mooring point S12. When the wind direction changes, the rotor S15, subjected to uneven aerodynamic loads, will passively yaw to align with the wind direction. However, the rotational efficiency is low, and when the wind, waves, and currents are in opposite directions, it often cannot completely align with the wind direction. The active yaw system consists of a gyroscope S111, a wind speed-direction instrument S141, a control system S142, and a pitch control execution subsystem S151.

[0025] Furthermore, the anemometer S141 uses an ultrasonic sensor (accuracy ±0.5°) and is installed at the windward position on the top of the nacelle S14. The gyroscope S111 uses a fiber optic gyroscope (accuracy ±0.1° / s) and is installed in a compartment near the center of gravity of the platform S11. The control system S142 uses an industrial-grade PLC with a control cycle of 10ms. The pitch actuator subsystem S151 uses an electric pitch mechanism and is equipped with a supercapacitor as a backup power source to ensure continuous operation for 30 minutes in the event of a power grid failure.

[0026] The control system S142 is located inside the nacelle, receives signals from the anemometer S141 and gyroscope S111, and transmits the output signals to the pitch control subsystem via a wired cable. The active yaw process is as follows: Figure 2 As shown, it includes the following steps: Step S1: Real-time acquisition of wind deviation angle Platform first angle Platform initial rocking velocity ; Step S2: If | |> If the preset threshold is 5°, then navigation correction control will be activated; Step S3: According to The positive and negative values ​​and blade azimuth angles are used to balance the pitch angle for power. Adjust the blade pitch angle based on the basic differentiation : when >0 (left-hand wind deflection): When the blades are in the right half of the rotor disk, the pitch angle decreases to increase thrust, and when they are in the left half of the rotor disk, the pitch angle increases to decrease thrust, generating a leftward steering torque; when <0 (wind deflection to the right disk): When the blades are in the right half of the rotor disk, the pitch angle is increased to reduce thrust, and when they are in the left half of the rotor disk, the pitch angle is decreased to increase thrust, generating a rightward correction torque; Step S4: The control signal is transmitted to the pitch control system. According to the pitch control command, the pitch motor of the corresponding blade is started, driving the blade (usually a three-bladed blade) to perform pitch control and generate the corresponding steering torque.

[0027] Step S5: Dynamically optimize the adjustment amount using PID and fuzzy logic algorithms until... →0.

[0028] The dual-mode control algorithm logic of the central controller is as follows: Figure 3 as follows: The main inputs to the controller include the inflow wind direction angle θ measured by the anemometer. w θ measured by a gyroscope inside the platform cabin Y The wind deviation angle, E, is calculated. θ =θ w -θ Y E θ >0 indicates that the wind direction is to the left of the platform (viewing towards the wheel hub), requiring a leftward steering torque; E θ A value less than 0 indicates a need for rightward correction. The controller employs a dual-mode structure combining PID control and fuzzy logic control, switching modes based on the magnitude of the deviation to balance dynamic response speed, steady-state accuracy, and robustness.

[0029] Mode switching threshold: Set a deviation threshold E switch (e.g., 10°).

[0030] PID control mode (coarse adjustment mode): Trigger condition: |E θ | ≥ E switch .

[0031] Control objective: When the deviation is large, the PID control is used to quickly reduce the deviation amplitude by taking advantage of its fast response and ability to provide a large initial control quantity, thereby achieving "coarse adjustment" of the wind process.

[0032] Fuzzy logic control mode (fine-tuning mode): Trigger condition: |E θ | <E switch .

[0033] Control objective: When the deviation is small, switch to fuzzy logic control. This mode can better handle system nonlinearity and platform motion coupling disturbances, and suppress oscillations that may be caused by pure PID control, achieving smooth, overshoot-free "fine-tuning" and making E... θ It converges stably to near zero.

[0034] Switching logic: A switching strategy with hysteresis is employed to prevent frequent mode jumps. For example, when switching from PID mode to fuzzy logic mode, it is necessary to wait for |E... θ Slightly greater than E switch (e.g. E) switch It only switches back to PID mode when the temperature reaches +1°.

[0035] In PID control mode, the controller will E θ As the primary controlled variable, the steering torque command M _cmd_PID Calculated using the following discrete PID formula: M cmd_PID (k) = K p E θ (k) + K i ∑E θ (j) Ts + K d [E θ (k) - E θ [(k-1)] / Ts - K damp dθ Y Where: k is the current control period; K p , K i, K d These are the proportional, integral, and differential gains, respectively; K damp The additional differential (damping) gain is based on the platform's initial roll angular velocity to suppress initial roll oscillation; Ts is the controller sampling period (e.g., 10ms); ∑E θ (j) Ts is the integral term of the deviation.

[0036] In fuzzy logic control mode, with E θ and θ Y As input, the steering torque command M is obtained through fuzzy reasoning. cmd_Fuzzy .

[0037] Wind deviation angle E θ The domain of discourse is [-E] switch E switch The fuzzy subset is defined as: {Negative Large (NB), Negative Medium (NM), Negative Small (NS), Zero (ZO), Positive Small (PS), Positive Medium (PM), Positive Large (PB)}. The membership function is triangular or Gaussian.

[0038] Platform initial angular velocity θ Y The universe of discourse is set according to the platform's motion characteristics. The fuzzy subset is defined as: {Negative Large (NB), Negative Small (NS), Zero (ZO), Positive Small (PS), Positive Large (PB)}.

[0039] Output variable: Navigation torque command M cmd_Fuzzy The fuzzy subset is defined as: {Negative Large (NB), Negative Medium (NM), Negative Small (NS), Zero (ZO), Positive Small (PS), Positive Medium (PM), Positive Large (PB)}.

[0040] Fuzzy rule base: Based on expert experience and system dynamics design, its core principle is: DeviationE θ The sign of the torque determines the direction of the torque.

[0041] DeviationE θ The magnitude of the torque is determined by the size of the torque.

[0042] angular velocity θ Y Used to provide damping: if the angular velocity direction is the same as the desired correction direction (i.e., the platform is rotating in the direction of correcting the deviation), the torque command is appropriately reduced to prevent overshoot; if it is in the opposite direction (the platform motion exacerbates the deviation), the torque command is increased.

[0043] Example rules: IF E θ is PB AND θ Y is ZO, THEN M cmdThis is NB. (The deviation is large and the platform hasn't moved; a large torque needs to be applied.) IF E θ is PS AND θ Y is NS, THEN M cmd is NS. (Small deviation and the platform is rotating in the correct direction, apply a small torque damping.) IF E θ is ZO AND θ Y is ZO, THEN M cmd It is ZO (aligned and stationary, not outputting torque). Inference and Defuzzification: Mamdani-type inference and the Center of Gravity (CoG) method are used for defuzzification, converting the fuzzy output into a precise M value. cmd_Fuzzy .

[0044] The allocation strategy for pitch angle compensation values: Regardless of whether it comes from PID mode or fuzzy logic mode, the final generated steering torque command M _cmd Each blade needs to be allocated according to a certain strategy, which is then converted into a differentiated pitch angle compensation value Δβ. cmd_i .

[0045] Distribution principle: According to aerodynamic principles, the thrust generated by the blades is closely related to their pitch angle (angle of attack). In order to generate a torque around the tower axis (yaw axis), a thrust difference needs to be generated on both sides of the rotor's plane of rotation.

[0046] Assignment function: For the i-th blade, its pitch angle compensation value Δβ cmd (i) Calculate using the following formula: Δβ cmd (i) = -K a M cmd sin(ψ i ) Where: ψ i K represents the azimuth angle of the i-th blade (0° points directly upwards; clockwise or counterclockwise rotation must be defined in accordance with the control system convention). a To allocate the gain coefficient, the torque command is mapped to the pitch angle change, the value of which is calibrated through aerodynamic simulation or experiment.

[0047] Coordination with power generation control: Calculated Δβ cmd (i) Dynamically superimposed onto the power generation reference pitch angle β ref (i) Above. Under strong navigational requirements, Δβ cmd (i) It may temporarily dominate the blade angle, prioritizing wind protection; when the deviation approaches zero, M cmd and Δβcmd (i) also approaches zero, and the blade pitch angle is completely changed from the original generator controller β. ref (i) Determine to achieve optimal recovery of power generation efficiency.

[0048] The aforementioned control signals, combined with azimuth commands, are distributed to each blade.

[0049] After receiving the command, the pitch controller drives the servo motor to operate. Through a reduction gearbox, the motor's high speed and low torque are converted to low speed and high torque, which in turn drives the pinion gear meshing with the internal gear ring of the pitch bearing. Ultimately, this drives the entire blade to rotate around its axis to the target angle. Encoders installed at the non-drive end of the motor and at the blade root provide real-time feedback on the actual blade angle, comparing it with the target value. The controller continuously adjusts the motor output based on the error signal until the actual pitch angle matches the target value, forming a high-precision closed-loop position control. Throughout the process, the pitch actions of each blade are independent yet coordinated, generating differentiated aerodynamic thrust at different azimuth angles, ultimately synthesizing a steering torque that aligns the wind turbine platform with the wind direction.

[0050] For common wind speed and deflection conditions, a comparison is made of the time-series changes in blade pitch angle between traditional centralized pitch control (CPC) and the control method (IPC) proposed in this invention. Figure 4 As shown, under the control method of this invention, the pitch angle of each blade changes periodically, and the blades alternate and operate in an orderly manner, while in the traditional method, the blades remain at 0°. Compared to the traditional wind-fighting process, the pitch control method of this invention significantly improves the wind-fighting deflection speed of the single-point moored floating wind turbine, such as... Figure 5 As shown, wind efficiency is improved by 55%. In situations where the wind direction is 30° and the flow direction is 0°, traditional single-point mooring cannot effectively align with the wind direction, resulting in an approximately 20° deviation. This leads to a reduction in wind energy conversion efficiency. Using the method of this invention, single-point moored floating wind turbines can quickly align with the wind direction.

[0051] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A single-point mooring offshore floating wind turbine wind steering system based on independent pitch control, characterized in that, include: The system comprises a deviation angle measurement subsystem, a control system, and a pitch execution subsystem. The deviation angle measurement subsystem measures the deviation angle between the inflow wind direction angle and the platform's pitch angle. The controller generates a wind turbine pitch command signal based on the deviation angle and the platform's motion state using a control algorithm. The pitch execution subsystem executes the command, driving differentiated pitch control of each blade to generate a steering torque.

2. The single-point mooring offshore floating wind turbine wind steering system based on independent pitch control as described in claim 1, characterized in that, The real-time deviation angle measurement subsystem includes an anemometer mounted on the top of the nacelle and a gyroscope mounted inside the platform compartment; the anemometer is used to measure the inflow wind direction angle. , Measurement Initial rocking angular velocity .

3. The single-point mooring offshore floating wind turbine wind steering system based on independent pitch control as described in claim 2, characterized in that, The controller is based on the wind deviation angle. The system monitors the platform's motion status and uses a dual-mode control algorithm combining PID and fuzzy logic to calculate the target pitch angle compensation value for each blade in real time, and then outputs control commands.

4. The single-point mooring offshore floating wind turbine wind steering system based on independent pitch control as described in claim 3, characterized in that, The pitch control subsystem includes a pitch controller, pitch bearings, a reduction gearbox, a servo motor, an encoder, and a backup power supply. After receiving commands from the control system, it independently adjusts the pitch angle of each blade.

5. The single-point mooring offshore floating wind turbine wind steering system based on independent pitch control as described in claim 4, characterized in that, When the windward deviation angle When the thrust is greater than 0, the blades reduce the pitch angle to increase thrust when they are in the right half of the rotor disk, and increase the pitch angle to decrease thrust when they are in the left half of the rotor disk, generating a leftward steering torque. When the windward deviation angle When the pitch angle is less than 0, the blades increase the pitch angle to reduce thrust when they are in the right half of the rotor disk, and decrease the pitch angle to increase thrust when they are in the left half of the rotor disk, generating a rightward steering torque.

6. The single-point mooring offshore floating wind turbine wind steering system based on independent pitch control as described in claim 5, characterized in that, The wind speed and direction indicator uses an ultrasonic sensor; the gyroscope uses a fiber optic gyroscope; the central controller S142 uses an industrial-grade PLC; and the pitch actuator subsystem uses an electric pitch mechanism.

7. A method for single-point mooring offshore floating wind turbines to navigate and correct wind direction based on independent pitch control, characterized in that, include: Measure the deviation angle between the inflow wind direction angle and the platform's initial roll angle; If the absolute value of the deviation angle is greater than the preset threshold, the pitch angle of each blade is adjusted differently according to the sign of the deviation angle and the blade azimuth angle to generate a steering torque; the deviation angle is brought close to zero through closed-loop control.

8. The method for single-point mooring offshore floating wind turbines based on independent pitch control as described in claim 7, characterized in that, The specific method for differentially adjusting the pitch angle is as follows: when the deviation angle is positive, decrease the pitch angle of the blades on the right half of the rotor and increase the pitch angle of the blades on the left half of the rotor; when the deviation angle is negative, increase the pitch angle of the blades on the right half of the rotor and decrease the pitch angle of the blades on the left half of the rotor.

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