A floating wind turbine dynamic positioning assisted mooring system with triggering cooperation function

Abstract

This invention discloses a floating wind turbine dynamic positioning auxiliary mooring system with trigger-assisted positioning function, comprising a floating wind turbine, a low-strength mooring system, and a dynamic positioning system; the floating wind turbine includes a wind turbine generator and a semi-submersible platform; the mooring system includes anchor chains and anchoring foundations; the dynamic positioning system includes a measurement system and a propulsion system connected to the control system; when the wind turbine generator is operating, if the motion response of the floating wind turbine exceeds a preset value, the trigger module sends an activation signal to the propulsion system, triggering the propulsion system to perform cooperative positioning to improve the positioning capability and accuracy of the floating wind turbine; when the wind turbine generator is shut down, if the maximum tension of a certain anchor chain exceeds a preset safety limit, the trigger module sends an activation signal to the propulsion system, triggering the propulsion system to perform cooperative positioning, which can reduce the stress on the anchor chain, prevent anchor chain breakage, and also reduce the design strength of the mooring system and reduce the cost of the anchor chain.

Description

Technical Field

[0001] This invention relates to the field of offshore floating wind turbine positioning technology, specifically to a floating wind turbine dynamic positioning auxiliary mooring system with triggering and cooperating functions. Background Technology

[0002] With the ever-increasing demand for energy and concerns about natural issues such as global warming, people's demand for and interest in renewable energy are constantly growing, and wind power has become increasingly popular in recent years. There are two types of wind power: onshore wind power and offshore wind power. Offshore wind power has significant advantages over onshore wind power. Offshore wind speeds are higher, and wind energy resources are abundant; sea surface friction is lower, resulting in higher quality wind energy; sea winds have a stable dominant direction, allowing wind turbines to operate stably for longer periods; offshore wind turbines have larger single-unit capacity and higher energy output; the development of offshore wind power has less negative environmental impact, does not occupy valuable land resources, and has less impact on residents' lives. Therefore, with the gradual improvement of offshore wind turbine installation technology, offshore wind power is a foreseeable development trend.

[0003] Currently, floating wind turbines are positioned using mooring systems, relying on the restoring force provided by the anchor chains to balance the environmental forces acting on the turbine, keeping it fixed within a certain range. This system offers advantages such as low investment, ease of use, and convenient maintenance. However, as wind power development moves towards deeper waters, deep-water mooring systems require excessively redundant anchor chain length and strength to withstand complex and extreme sea conditions. This leads to a dramatic increase in anchor chain weight, making installation more complex and difficult, and drastically increasing costs. To address these issues, a dynamic positioning system, unaffected by water depth, has been proposed for the floating wind turbine platform. The dynamic positioning system uses the thrust generated by the propeller to automatically maintain the floating wind turbine at the target position and heading. Its basic principle is to obtain the deviation between the floating wind turbine's current real-time position and the target position, calculate the thrust and torque required for the turbine to return to the target position using the control system, and then use the propulsion system to deliver the required thrust, thus resisting external environmental forces and maintaining the floating wind turbine near the target position. While the dynamic positioning system offers flexible output and high positioning accuracy, it requires continuous operation, resulting in extremely high power consumption. Summary of the Invention

[0004] The purpose of this invention is to propose a floating wind turbine dynamic positioning auxiliary mooring system with a trigger-cooperative function. This system enables positioning using only the mooring system under calm sea conditions, without energy consumption, significantly reducing the design strength of the mooring system and effectively lowering the cost and installation difficulty of the anchor chain. Under extreme sea conditions, it triggers the dynamic positioning system for cooperative positioning, improving the positioning capability and accuracy of the floating wind turbine, reducing the working time of the dynamic positioning system, lowering power consumption, and improving the economic efficiency of the floating wind turbine.

[0005] To achieve the above objectives, this application proposes a floating wind turbine dynamic positioning assisted mooring system with a trigger-cooperative function, comprising a floating wind turbine, a low-strength mooring system, and a dynamic positioning system; the floating wind turbine includes a wind turbine generator and a semi-submersible platform; the mooring system includes an anchor chain and an anchoring foundation; the dynamic positioning system includes a measurement system and a propulsion system connected to the control system; the wind turbine generator is installed on the semi-submersible platform, and the semi-submersible platform is connected to the anchoring foundation located on the seabed via the anchor chain; the propulsion system is installed at the bottom of the semi-submersible platform to compensate for the low-frequency movement of the floating wind turbine; the trigger module of the control system determines whether to activate the propulsion system by monitoring the motion response of the floating wind turbine and the maximum tension of the anchor chain: if the motion response of the floating wind turbine or the maximum tension of a certain anchor chain exceeds a preset safety limit, an activation signal is sent to the propulsion system to trigger the propulsion system to perform cooperative positioning.

[0006] Furthermore, the measurement system includes a position sensor and a tension sensor. The position sensor is installed at the bottom of the semi-submersible platform to provide the position and heading of the floating wind turbine in real time, thereby obtaining the motion response. The tension sensor is installed at the top of each anchor chain to obtain the tension of the anchor chain.

[0007] Furthermore, the mapping relationship between the maximum tension of the anchor chain and the position and heading of the floating wind turbine is as follows:

[0008] F Ti =a|DM| i

[0009] In the formula: F Ti |DM| represents the maximum tension of the i-th anchor chain; a represents the mapping coefficient; i This represents the distance between the guide hole and the anchor point of the i-th anchor chain;

[0010] To maximize the positioning capability of the mooring system, the safety limits are set as follows:

[0011] T safe =nT MBL

[0012] In the formula: T safe Indicates safety limits; T MBL This represents the breaking tension of the anchor chain; n represents the safety factor.

[0013] Furthermore, the control strategy module of the control system is used to obtain the total thrust and torque required by the propulsion system, specifically:

[0014]

[0015] In the formula: F controlη represents the control force, i.e., the total thrust and torque required by the propulsion system; η represents the current position and attitude of the floating wind turbine; η d Indicates the desired location and orientation of the positioning point; K p This represents the proportional coefficient, used to control the output relative to (η-η). d The proportional relationship of K; i Represents the integral coefficient, used to control the (η-η) within the operating period of the propulsion system. d Average value; K d This represents the differential coefficient, used for predictive control of the output changes of the propulsion system.

[0016] Furthermore, the thrust distribution module of the control system is used to obtain the thrust and torque of each thruster in the propulsion system, specifically:

[0017]

[0018] In the formula: W i This represents the power required for the i-th thruster to generate thrust. Where K Q K represents the torque coefficient of the thruster. T Let α represent the thrust coefficient of the thruster, D represent the diameter of the thruster, ρ represent the density of seawater, T represent the thrust vector generated by each thruster, and B(α) represent the thruster arrangement matrix. Where, α i Let α ∈ R be the thrust direction of the i-th thruster. 3 For a vector containing all thrust direction values, (l xi , l yi ) represents the coordinates of the i-th thruster in the horizontal plane; s represents the error between the required control force and the actual total thrust generated by the thruster; ΔT i T represents the change in thrust of the i-th thruster; i0 Δα represents the thrust of the i-th thruster at the previous moment; i Q represents the change in the thrust direction of the i-th thruster; i Let Q ∈ R represent the error weight between the required control force in the i-th direction and the actual total thrust generated by the thruster. 3×3 Ω is a matrix containing the weights of all directional errors. i The weight represents the change in the thrust direction of the i-th thruster.

[0019] The first term of the objective function is the sum of the power consumption of each thruster; the second term is a penalty function term constructed based on the deviation s between the required total thrust and the actual total thrust. The diagonal terms in matrix Q have larger values ​​to ensure that the deviation s is as close to zero as possible under any circumstances; the third term is a function constructed for the thruster's angle change rate, where α0 is the thruster's angle in the previous calculation cycle; the fourth term is a weighting coefficient ρ≥0 to prevent singular solutions in the thrust distribution calculation. A larger weighting coefficient can bring better handling performance but will increase the steady-state power consumption. ε>0 is to avoid numerical errors due to the denominator being zero in the calculation.

[0020] Furthermore, the constraints of the thrust distribution module are as follows:

[0021]

[0022] T min ≤T0+ΔT≤T max

[0023] ΔT min ≤ΔT≤ΔT max

[0024] α min ≤α0+Δα≤α max

[0025] Δα min ≤Δα≤Δα max

[0026] In the formula: ΔT represents the thrust change vector of each thruster; T0 represents the thrust vector of each thruster at the previous moment; Δα represents the thrust direction change vector of each thruster; α0 represents the thrust direction vector of each thruster at the previous moment;

[0027] The first constraint is to ensure that the total thrust generated by the thrusters equals the required control force; the second constraint is to limit the thrust range generated by each thruster, T. min and T max The first constraint is the vector of the maximum and minimum thrust that each thruster can generate; the second constraint limits the thrust transformation speed of the thrusters; and the third constraint limits the range of thruster rotation angles, given the maximum rotation angle vector Δα. max and the minimum value vector Δα min The fifth constraint is to limit the speed of the thruster's rotation angle change to prevent excessively fast and large azimuth angle changes.

[0028] Furthermore, when the wind turbine is operating, if the motion response of the floating wind turbine exceeds a preset value, the trigger module sends an activation signal to the propulsion system to trigger it; when the wind turbine is shut down, if the maximum tension of a certain anchor chain exceeds a preset safety limit, the trigger module sends an activation signal to the propulsion system to trigger it.

[0029] Furthermore, at any given moment, the floating wind turbine undergoes low-frequency motion under the influence of environmental loads, mooring system, and dynamic positioning system. The measurement system provides the floating wind turbine's motion response in real time. The triggering module determines whether to activate the propulsion system by monitoring the floating wind turbine's motion response and the maximum tension of the anchor chain. When the propulsion system is activated, the control strategy module uses the preset motion response as the positioning point and calculates the total thrust that the propulsion system should provide based on the difference between the floating wind turbine's current motion response and the preset motion response. Subsequently, the thrust distribution module distributes the total thrust to each thruster, and the thrusters then exert force on the floating wind turbine.

[0030] Furthermore, the environmental loads include wind loads, wave loads, and flow loads.

[0031] Furthermore, the mathematical model of the mooring system is expressed as follows:

[0032]

[0033] F x =1.851x 3 -6.947x 2 -97.503x+39.123

[0034] F y =-0.369y 3 -77.19y

[0035] F z =-0.006z 3 +0.409z 2 +42.967z +947.998

[0036]

[0037] M θ =2.644θ 3 -13.126θ 2 -766.159θ-30190.419

[0038] M ψ =0.507ψ 3 -16.094ψ 2 +412.115ψ+11406.958

[0039] In the formula, F x F y F z This represents the restoring force generated by the mooring system along the x, y, and z directions. M θ M ψ This represents the restoring torque generated by the mooring system about the x, y, and z directions.

[0040] Compared with the prior art, the above technical solutions adopted in this invention have the following advantages: 1) The normal sea conditions are used as the design conditions for the mooring system, which ensures that the floating wind turbine can work safely and stably under calm and moderate sea conditions, while also reducing the cost of anchor chains and the area occupied.

[0041] 2) The triggering module of the control system can determine whether to start the propulsion system and trigger or stop the propulsion system by monitoring the motion response of the floating wind turbine and the maximum tension of the anchor chain;

[0042] 3) Installing a propulsion system on a semi-submersible platform can control the low-frequency movement of the floating wind turbine under moderate sea conditions, improving the positioning accuracy of the floating wind turbine; it can also compensate for the environmental forces on the floating wind turbine under extremely harsh sea conditions, prevent anchor chain breakage, improve the positioning capability of the floating wind turbine, and ensure the safety of the floating wind turbine. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be 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.

[0044] Figure 1 A schematic diagram of a floating wind turbine dynamic positioning auxiliary mooring system;

[0045] Figure 2 This is a schematic diagram of a semi-submersible platform structure.

[0046] Figure 3 A schematic diagram of the mooring system layout;

[0047] Figure 4 A schematic diagram of the thruster arrangement;

[0048] Figure 5 The open-water characteristic curve of the AU5-50 propeller;

[0049] Figure 6 This is the envelope diagram of the horizontal motion response of the mooring system.

[0050] Figure 7This is a schematic diagram of the coordinate system and platform motion. Specific implementation methods

[0051] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the application; that is, the described embodiments are only a part of the embodiments of this application, and not all of them.

[0052] like Figure 1-6 As shown, this embodiment provides a floating wind turbine dynamic positioning assisted mooring system with triggering cooperation function, including a floating wind turbine, a low-strength mooring system, and a dynamic positioning system; the semi-submersible platform is equipped with a mooring system with lower strength than the traditional mooring system. This mooring system reduces the number and length of anchor chains in the traditional mooring design, can provide sufficient mooring restoring force in calm sea conditions, and at the same time reduces installation costs and difficulty and anchor chain footprint, as shown in the table below;

[0053] Table 1 Comparison of Design Parameters for Mooring Systems

[0054]

[0055] The dynamic positioning system includes a control system, a measurement system, and a propulsion system. The dynamic positioning system uses the three-degree-of-freedom low-frequency motion response (sway, pitch, and bow) of the floating wind turbine in the horizontal plane as the control variable, and maintains the position and heading of the floating wind turbine through thruster output. The control system includes a trigger module, a control strategy module, and a thrust distribution module. The propulsion system consists of three thrusters installed at the bottom of the semi-submersible platform, and the thrust distribution module determines the output of each thruster to compensate for the low-frequency motion of the floating wind turbine. The measurement system includes position sensors, tension sensors, and a position reference system.

[0056] Specifically, the position reference system includes:

[0057] (1) Geodetic coordinate system, taking any point on the sea surface as the origin O. E X E The axis points due north, Y E The axis points due east, Z E The axis points to the Earth's center. The direction of motion of the floating wind turbine is positive along the positive direction of the coordinate axis. The incident direction of wind, wave, and current loads is defined as 0° when it is along the positive direction of the x-axis.

[0058] (2) Platform coordinate system, with the origin O at the center of the plane where the still water surface intersects the platform. B X B Axis direction as Figure 7 Direction shown, Y BAxis direction as Figure 7 As shown, the ZB axis points towards the seabed.

[0059] The dynamic model of a floating wind turbine is established in the platform coordinate system, and it is necessary to transform the platform's motion state to the earth coordinate system. The six-degree-of-freedom motion vector of the floating wind turbine in the platform coordinate system can be expressed as v = [uvwpqr]. T The pose vector and its derivative in a fixed coordinate system can be expressed as: The transformation relationship between the two sets of vectors above can be described as follows:

[0060]

[0061]

[0062] In the formula:

[0063]

[0064]

[0065] Combining equations (1) and (2) yields the following expression:

[0066]

[0067] Where R(η) is the rotation transformation matrix and is expressed as:

[0068]

[0069] The dynamic positioning system only considers the platform's motion in the horizontal plane, i.e., the three degrees of freedom of sway, roll, and pitch, with the state vector being v = [uvr]. T η = [xy ψ] T The rotation transformation matrix for a 3-DOF motion can be expressed as:

[0070]

[0071] The dynamic equation of the floating wind turbine can be expressed as:

[0072]

[0073] In the formula: M represents the system inertial mass matrix; D represents the damping matrix, with only linear damping considered when the velocity is close to 0; G represents the generalized restoring force matrix; η represents the current position and attitude of the floating wind turbine; F wind F represents the wind force and moment generated by wind load; wave F represents the second-order wave force and moment generated by the wave load; current F represents the flow force and moment generated by the flow load; moorF represents the restoring force and torque generated by the mooring system. control This refers to the control force, which is the total thrust and torque actually generated by the propulsion unit.

[0074] The wind load is obtained as follows:

[0075]

[0076] In the formula: ρ a U is the density of air. T,z C represents the wind speed at height z within the average time period T; z C is the height coefficient of the wind-receiving structure. s To construct the shape coefficient; C DD A is the drag coefficient; n S is the windward area of ​​the wind-receiving component; S is the swept area of ​​the wind turbine, which is 7.5% of the swept area when the turbine is stopped.

[0077] The wave load is obtained as follows:

[0078]

[0079] In the formula: ω i and ω j ζ is the frequency of the incident wave. i and ζ j ε is the amplitude of the incident wave; i and ε j The phase angle is random; P ij Q ij , It is a QTF matrix.

[0080] The method for obtaining the flow load is as follows:

[0081]

[0082] In the formula: ρ is the density of seawater; C d A is the drag coefficient; c The frontal area of ​​the floating wind turbine platform; u c This refers to the relative flow velocity.

[0083] The mathematical model of the mooring system can be expressed as:

[0084] F x =1.851x 3 -6.947x 2 -97.503x+39.123

[0085] F y =-0.369y 3 -77.19y

[0086] Fz =-0.006z 3 +0.409z 2 +42.967z +947.998

[0087]

[0088] M θ =2.644θ 3 -13.126θ 2 -766.159θ-30190.419

[0089] M ψ =0.507ψ 3 -16.094ψ 2 +412.115ψ+11406.958

[0090] In the formula, F x F y F z This represents the restoring force generated by the mooring system along the x, y, and z directions. M θ M ψ This represents the restoring torque generated by the mooring system about the x, y, and z directions.

[0091] The time-domain simulation of the above-mentioned floating wind turbine dynamic positioning assisted mooring system with triggering cooperation function is as follows:

[0092] The first step is to obtain the environmental forces and mooring restoring forces acting on the floating wind turbine at the initial moment, given the initial motion response of the floating wind turbine, using the environmental load and the mathematical model of the mooring system.

[0093] The second step is to determine whether to activate the propulsion system based on the initial motion response of the floating wind turbine and the maximum tension of the anchor chain. When the motion response and the maximum tension of all anchor chains are less than the preset values, the propulsion system is not activated. If the motion response of the floating wind turbine or the maximum tension of a certain anchor chain exceeds the preset safety limit, the propulsion system is activated. The control module calculates the control force by the difference between the current motion response of the floating wind turbine and the preset motion response, and then uses the thrust distribution module to obtain the thrust magnitude and direction of each thruster and the actual total thrust.

[0094] The third step involves using the floating wind turbine dynamics model to derive the floating wind turbine's motion response at the next moment based on the environmental forces, mooring restoring forces, and actual total thrust (this item is not present when the propulsion system is not activated), thereby forming a closed-loop control system.

[0095] In this application, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0096] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A floating wind turbine dynamic positioning assisted mooring system with triggering cooperation function, characterized in that, The system includes a floating wind turbine, a mooring system, and a dynamic positioning system. The floating wind turbine includes a wind turbine generator and a semi-submersible platform. The mooring system includes anchor chains and anchoring foundations. The dynamic positioning system includes a measurement system and a propulsion system connected to the control system. The wind turbine generator is installed on the semi-submersible platform, which is connected to the anchoring foundations located on the seabed via anchor chains. The propulsion system is installed at the bottom of the semi-submersible platform to compensate for the low-frequency movement of the floating wind turbine. The trigger module of the control system monitors the motion response of the floating wind turbine and the maximum tension of the anchor chains to determine whether to activate the propulsion system. If the motion response of the floating wind turbine or the maximum tension of a certain anchor chain exceeds a preset safety limit, an activation signal is sent to the propulsion system to trigger the propulsion system for cooperative positioning. The mapping relationship between the maximum tension of the anchor chain and the position and heading of the floating wind turbine is as follows: In the formula: Indicates the first The maximum tension of the anchor chain; Indicates the coefficients of the mapping relationship; Indicates the first The distance between the guide hole and the anchor point of the anchor chain; To maximize the positioning capability of the mooring system, the safety limits are set as follows: In the formula: Indicates safety limits; Indicates the breaking tension of the anchor chain; Indicates the safety factor; The control strategy module of the control system is used to obtain the total thrust and torque required by the propulsion system, specifically: In the formula: This represents the control force, which is the total thrust and torque that the propulsion system needs to generate; This indicates the current position and attitude of the floating wind turbine; Indicates the desired location and orientation of the positioning point; This represents the proportional coefficient, used to control the output and... proportional relationship; This represents the integral coefficient, used to control the propulsion system during its operating period. average value; This represents the differential coefficient, used for predictive control of the output changes of the propulsion system; When the wind turbine is working, if the motion response of the floating wind turbine exceeds the preset value, the triggering module sends an activation signal to the propulsion system to trigger it; when the wind turbine is stopped, if the maximum tension of a certain anchor chain exceeds the preset safety limit, the triggering module sends an activation signal to the propulsion system to trigger it. At any given moment, the floating wind turbine undergoes low-frequency motion under the influence of environmental loads, mooring system, and dynamic positioning system. The measurement system provides the floating wind turbine's motion response in real time. The trigger module determines whether to activate the propulsion system by monitoring the motion response of the floating wind turbine and the maximum tension of the anchor chain. When the propulsion system is activated, the control strategy module uses the preset motion response as the positioning point and calculates the total thrust that the propulsion system should provide based on the difference between the current moment of the floating wind turbine and the preset motion response. Then, the thrust distribution module distributes the total thrust to each thruster, and the thrusters output force to act on the floating wind turbine.

2. The floating wind turbine dynamic positioning assisted mooring system with triggering cooperation function according to claim 1, characterized in that, The measurement system includes a position sensor and a tension sensor. The position sensor is installed at the bottom of the semi-submersible platform to provide the position and heading of the floating wind turbine in real time, thereby obtaining the motion response. The tension sensor is installed at the top of each anchor chain to obtain the tension of the anchor chain.

3. The floating wind turbine dynamic positioning assisted mooring system with triggering cooperation function according to claim 1, characterized in that, The thrust distribution module of the control system is used to obtain the thrust and torque of each thruster in the propulsion system, specifically: In the formula: Indicates the first The power required for each thruster to generate the thrust. ,in This indicates the torque coefficient of the thruster. Indicates the thrust coefficient of the propulsion unit. Indicates the diameter of the thruster. Indicates the density of seawater; This represents the thrust vector generated by each thruster; This represents the arrangement matrix of the thrusters. ,in, For the first The thrust direction of each thruster is defined. This is a vector containing all thrust direction values. Indicates the first The coordinates of each thruster in the horizontal plane; This indicates the error between the required control force and the actual total thrust generated by the thruster. Indicates the first The thrust variation of each thruster; Indicates the previous moment. The thrust of each propeller; Indicates the first The change in the thrust direction of each thruster; Indicates the first The error weights between the required control force in each direction and the actual total thrust generated by the thruster are defined. It is a matrix containing the weights of all directional errors; Indicates the first Weights of the changes in thrust direction of each thruster; constants .

4. The floating wind turbine dynamic positioning assisted mooring system with triggering cooperation function according to claim 1, characterized in that, The constraints of the thrust distribution module are as follows: In the formula: This represents the thrust variation vector for each thruster; This represents the thrust vector of each thruster at the previous moment; This represents the vector of the change in thrust direction for each thruster; This represents the thrust direction vector of each thruster at the previous moment; and A vector of the maximum and minimum thrust that each thruster can produce; and for The vectors of maximum and minimum corner values.

5. The floating wind turbine dynamic positioning assisted mooring system with triggering cooperation function according to claim 1, characterized in that, The environmental loads include wind loads, wave loads, and flow loads.

6. The floating wind turbine dynamic positioning assisted mooring system with triggering cooperation function according to claim 1, characterized in that, The mathematical model of the mooring system is expressed as follows: In the formula, , , This represents the restoring force generated by the mooring system along the x, y, and z directions. , , This represents the restoring torque generated by the mooring system about the x, y, and z directions.

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