Offshore semi-submersible wind turbine foundation and wind turbine generator set

Abstract

The present invention provides an offshore semi-submersible wind turbine foundation and a wind turbine generator set, comprising a main buoy, an oblique brace, a transverse brace and a heave plate. A plurality of main buoys are provided, and the main buoys are arranged along the vertex positions of a regular polygon. Adjacent main buoys are connected by oblique braces and transverse braces, and the heave plate is coaxially arranged at the bottom end of the main buoy. The cross section of the main buoy and the heave plate are both super elliptical. The extension lines of the major axes of the cross sections of the main buoy and the heave plate pass through the geometric center of the regular polygon. The main buoy of the offshore semi-submersible wind turbine foundation of the present invention can effectively reduce the stress concentration coefficient at the connection between the main buoy and the oblique brace and the transverse brace, thereby reducing the thickness of the main buoy, and achieving the effect of reducing the weight of the floating foundation.

Description

Technical Field

[0001] The invention belongs to the technical field of wind power generation, and in particular relates to an offshore semi-submersible wind turbine foundation and a wind power generator set. Background Art

[0002] With the continuous expansion of wind energy resource development, especially in deep sea, the research of floating wind turbines has attracted much attention. Commonly used floating foundations include Spar foundation, TLP foundation and semi-submersible foundation. The water depth in coastal areas of China is relatively shallow. Considering the water depth applicability of the platform and the cost of the mooring structure, the semi-submersible wind turbine foundation has received extensive attention in China due to its good stability, manufacturability and easy wet-tow installation.

[0003] Usually, the size of the main buoy of a semi-submersible platform needs to be designed to be larger, relying on a large draft to ensure that the natural period of heave is much larger than the wave period. Setting up a heave plate under the main buoy of a semi-submersible platform can avoid resonance between the platform and the waves, so that the platform has good motion performance. The additional mass increased by the heave plate can increase the natural period of heave of the platform and keep it away from the frequency band where wave energy is concentrated; and the additional damping provided can effectively reduce the dynamic response of the platform and improve the platform's motion performance.

[0004] like Figure 1 As shown, the place where the main buoy (1) of the semi-submersible platform foundation is connected to the cross brace (4) and the diagonal brace (3) will experience a local increase in stress (stress concentration). Stress concentration can cause fatigue cracks in an object and can also cause static load fracture of parts made of brittle materials. In engineering, the stress concentration factor SCF (Stress Concentration Factor) is used to indicate the degree of stress concentration. The SCF value can be calculated by dividing the maximum stress when stress concentration occurs by the average stress, and the SCF value is greater than 1. Engineering experience shows that the more drastic the change in cross-sectional dimensions, the greater the SCF value.

[0005] Therefore, when designing the main buoy of a semi-submersible floating wind turbine, the shape with right angles and sharp corners should be avoided as much as possible. At present, the design scheme basically adopts a cylindrical shape. However, the SCF value of the main buoy (1) designed according to the cylindrical design at the connection with the cross brace (4) and the diagonal brace (3) is still relatively large, generally reaching 3 to 5. Since the wall thickness of the main buoy (1) is very sensitive to the SCF value, in order to make the design of the main buoy meet the strength requirements, the existing cylindrical design still needs to thicken the wall thickness of the cross brace and diagonal brace, resulting in an increase in the mass of the main buoy.

[0006] Considering that the SCF value directly affects the wall thickness at the connection between the main buoy and the diagonal brace, it is necessary to design a main buoy structure that can reduce the SCF value under the existing process level, so as to reduce the wall thickness and reduce the weight of the floating foundation. Summary of the invention

[0007] In order to solve the problems existing in the prior art, the present invention provides an offshore semi-submersible wind turbine foundation and a heave plate, which can reduce the SCF of the connection between the main buoy and the cross brace and the diagonal brace, and reduce the weight of the foundation structure.

[0008] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: an offshore semi-submersible wind turbine foundation, including a main buoy, a diagonal brace, a transverse brace and a vertical swing plate. There are multiple main buoys, which are arranged along the vertex positions of a regular polygon, and adjacent main buoys are connected by diagonal braces and transverse braces. The vertical swing plate is coaxially arranged at the bottom end of the main buoy; the cross-section of the main buoy and the vertical swing plate are both super-elliptical; the extension lines of the major axes of the cross-sections of the main buoy and the vertical swing plate pass through the geometric center of the regular polygon.

[0009] The outer contour line of the super-elliptical cross section of the main buoy satisfies the following formula: The cross-sectional outer contour of the heave plate connected to the main buoy satisfies the following formula: Among them, x and y represent the coordinate values ​​of any point on the contour line on the x-axis and y-axis of the local coordinate system respectively, a1 represents 1 / 2 of the width of the outer contour line of the main pontoon cross-section on the x-axis, and b1 represents the height of the outer contour line of the main pontoon cross-section on the y-axis; a2 represents 1 / 2 of the width of the outer contour line of the vertical swing plate cross-section on the x-axis, and b2 represents the height of the outer contour line of the vertical swing plate cross-section on the y-axis. a1 / a2=b1 / b2, m1=n1, m2=n2, and m1, n1, m2 and n2 are all in the interval [1.50, 2.20].

[0010] The heave plate is welded to the main buoy.

[0011] The connection between the heave plate and the main buoy has a smooth transition.

[0012] The number of main buoys is 3-6.

[0013] The thickness t of the heave plate is 25-60mm.

[0014] Reinforced ribs are provided at the connection between the main buoy and the heave plate.

[0015] The surfaces of the main buoy, diagonal braces, transverse braces and heave plates are all provided with an anti-corrosion layer.

[0016] An offshore semi-submersible wind turbine generator set adopts the offshore semi-submersible wind turbine foundation of the present invention, wherein a tower is arranged on the central axis of the foundation, and the bottom of the tower is connected to a main buoy through diagonal braces and transverse braces.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: the main buoy and the heave plate are both elliptical, and the design of the main buoy and heave plate of the offshore semi-submersible wind turbine foundation of the present invention can effectively reduce the stress concentration coefficient at the connection between the main buoy and the diagonal brace and the transverse brace, and reduce the wall thickness of the main buoy, thereby reducing the weight of the main buoy and reducing the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0019] Figure 1 A three-dimensional schematic diagram of a semi-submersible wind turbine foundation is shown in the present invention.

[0020] Figure 2 is a schematic diagram illustrating a super elliptic function curve according to an exemplary embodiment of the present invention.

[0021] Figure 3 A schematic top view of a semi-submersible wind turbine foundation is shown in the present invention.

[0022] Figure 4 The present invention shows a three-dimensional schematic diagram of a main buoy and a heave plate of a semi-submersible wind turbine foundation.

[0023] Figure 5a A schematic front view of a main buoy and a heave plate of a semi-submersible wind turbine foundation that can be implemented in the present invention.

[0024] Figure 5b A schematic side view of a main buoy and a heave plate of a semi-submersible wind turbine foundation that can be implemented in the present invention.

[0025] Figure 5c A schematic top view of a main buoy and a heave plate of a semi-submersible wind turbine foundation that can be implemented in the present invention.

[0026] In the attached drawings, 1-main buoy, 2-tower, 3-diagonal brace, 4-transverse brace, 5-heave plate. DETAILED DESCRIPTION

[0027] Embodiments of the present invention are described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.

[0028] refer to Figure 3 and Figure 4 The present invention provides a main buoy and a heave plate of an offshore floating wind turbine foundation which can reduce the SCF of the connection between the main buoy 1 and the transverse brace 4 and the diagonal brace 3 and reduce the structural weight; an offshore semi-submersible wind turbine foundation, comprising a main buoy 1, a diagonal brace 3, a transverse brace 4 and a heave plate 5, wherein a plurality of main buoys 1 are provided, and adjacent main buoys 1 are connected by the diagonal brace 3 and the transverse brace 4, and the heave plate 5 is provided at the bottom end of the main buoy 1; the main buoy 1 and the heave plate 5 are both elliptical,

[0029] The cross-sectional outer contour of the main buoy 1 satisfies the following formula: The cross-sectional outer contour of the heave plate 5 connected to the main buoy 1 satisfies the following formula: Among them, x and y represent the coordinate values ​​of any point on the contour line on the long axis of the x-axis and the short axis of the y-axis of the local coordinate system respectively. The local coordinate system is a coordinate system within the cross-sectional range of the main pontoon 1, with the center of the cross-sectional center as the origin, the long axis of the ellipse as the x-axis, and the short axis as the y-axis. a1 represents 1 / 2 of the width of the outer contour line of the cross-sectional area of ​​the main pontoon 1 on the x-axis, and b1 represents the height of the outer contour line of the cross-sectional area of ​​the main pontoon 1 on the y-axis; a2 represents 1 / 2 of the width of the outer contour line of the cross-sectional area of ​​the heaving plate 5 on the x-axis, and b2 represents the height of the outer contour line of the cross-sectional area of ​​the heaving plate 5 on the y-axis.

[0030] The number of the main buoys 1 is 3-6.

[0031] The main buoy 1 is arranged along the vertex position of the regular polygon; the extension lines of the major axes of the cross sections of the main buoy 1 and the heave plate 5 both pass through the geometric center of the regular polygon.

[0032] The connection between the heave plate 5 and the main buoy 1 is smoothly transitioned, and the lower end of the main buoy 1 can be set as a bell mouth, and the lower end surface of the main buoy is welded to the heave plate 1.

[0033] The thickness t of the heave plate 5 is 25-60 mm.

[0034] As an optional embodiment, a reinforcing rib is provided at the connection between the main buoy 1 and the heave plate 5 .

[0035] The surfaces of the main buoy 1, the diagonal brace 3, the transverse brace 4 and the heave plate 5 are all provided with an anti-corrosion layer.

[0036] In the implementation of the present invention, the offshore semi-submersible wind turbine foundation is used for an offshore semi-submersible wind turbine generator set, the bottom of the tower 2 is connected to the foundation, the tower 2 is arranged on the central axis of the foundation, and the tower 2 is connected to the main buoy 1 through the diagonal brace 3 and the transverse brace 4.

[0037] The present invention provides a main buoy and a heave plate of an offshore floating wind turbine foundation, a main buoy 1 and a heave plate 5 of an offshore semi-submersible wind turbine foundation, and the cross-sectional outer contour line of the main buoy 1 satisfies the following formula:

[0038]

[0039] The cross-sectional outer contour of the heave plate 5 connected to the main buoy 1 satisfies the following formula:

[0040]

[0041] Wherein, x and y represent the coordinate values ​​of any point on the contour line on the local coordinate system x-axis (major axis) and y-axis (minor axis), respectively; a1 represents the 1 / 2 value of the width of the outer contour line of the cross section of the main buoy 1 on the x-axis, and b1 represents the height value of the outer contour line of the cross section of the main buoy 1 on the y-axis; a2 represents the 1 / 2 value of the width of the outer contour line of the cross section of the heave plate 5 on the x-axis, and b2 represents the height value of the outer contour line of the cross section of the heave plate 5 on the y-axis. In the formulas satisfied by the main buoy, a1 / a2=b1 / b2, m1=n1, m2=n2 and all are satisfied in the interval [1.50,2.20].

[0042] The present invention optimizes the shapes of the main buoy 1 and the heave plate 5 provided on the offshore semi-submersible wind turbine foundation to minimize the stress, thereby achieving the purpose of reducing the SCF value.

[0043] A rectangular coordinate system XO'Y is established with the cross-sectional outer contour of the main buoy and the heave plate and the center O' as the origin, and the horizontal axis and the vertical axis are defined as the X axis and the Y axis respectively.

[0044] Here, if Figure 2 The superelliptic function is shown below:

[0045] (x / a) m +(y / b) n =1

[0046] The superelliptic function is a new shape function based on the elliptic function. Through two variables m and n, a family of curves including ellipses can be drawn. The curve drawn according to the superelliptic function is called a superelliptic curve. When m=n=2, the superelliptic curve degenerates into an elliptic curve; when m=n=1, the superelliptic curve degenerates into a straight line. Due to the introduction of variables m and n, the scope of the design domain becomes larger, and the purpose of reducing the SCF value is achieved by setting appropriate m and n values.

[0047] When m and n respectively satisfy: 1.50≤m≤2.20, 1.50≤n≤2.20, the main buoy designed according to the above shape function formula 1 can effectively reduce the stress concentration factor SCF, thereby reducing the thickness of the tower at the position of the main buoy, reducing the overall weight of the tower, and reducing the production cost.

[0048] If m and n are outside the above range, the above effect cannot be achieved. In detail, when m and n are less than 1.50, the shape of the main pontoon approaches a rhombus, so that the main pontoon has obvious sharp edges and corners, which increases the stress concentration factor SCF at the corresponding position, resulting in an increase in the wall thickness of the main pontoon at the corresponding position, an increase in the overall weight of the main pontoon, and an increase in production costs. When m and n are greater than 2.20, the shape of the main pontoon approaches a rectangle with corners, which increases the stress concentration factor SCF at the corresponding position, resulting in an increase in the wall thickness of the main pontoon at the corresponding position, an increase in the overall weight of the main pontoon, and an increase in production costs.

[0049] The parameters of the main buoy of the super elliptical function are used to compare the main buoy designed by the super elliptical function according to the present invention with the main buoy designed by the standard circle in the prior art. Specifically, the shape of the main buoy according to the present invention is designed by the super elliptical function when m1=1.80 and n1=1.90, and the shape of the existing cylindrical main buoy is designed by the standard elliptical function (m=2, n=2).

[0050] Table 1 below shows the SCF calculation results of the main buoy designed with a super elliptical function formula according to the present invention and the main buoy designed with a standard elliptical function formula in the prior art.

[0051] Table 1

[0052]

[0053] It can be seen that compared with the existing main buoy designed with a standard elliptical function, the main buoy designed with a super elliptical function according to the present invention reduces the maximum stress concentration factor by 7.19%. From the results, compared with the main buoy in the traditional standard elliptical shape, the main buoy in the super elliptical shape according to the present invention is more conducive to reducing the stress concentration factor SCF. Therefore, under the existing process conditions, the optimization design of the main buoy shape by using a super elliptical function can effectively reduce the SCF value, thereby reducing the thickness of the main buoy, and achieving the effect of reducing the weight of the floating foundation.

[0054] While the invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the claims.

Claims

1. An offshore semi-submersible wind turbine foundation, characterized in that: The invention comprises a main buoy (1), a diagonal brace (3), a transverse brace (4) and a heave plate (5), wherein a plurality of main buoys (1) are provided, the main buoys (1) are arranged along the vertex positions of a regular polygon, adjacent main buoys (1) are connected by diagonal braces (3) and transverse braces (4), and the heave plate (5) is coaxially arranged at the bottom end of the main buoy (1); the cross section of the main buoy (1) and the heave plate (5) are both super elliptical; the extension lines of the major axes of the cross sections of the main buoy (1) and the heave plate (5) pass through the geometric center of the regular polygon; the outer contour line of the super elliptical cross section of the main buoy (1) satisfies the following formula: , the cross-sectional outer contour line of the heave plate (5) connected to the main buoy (1) satisfies the following formula: ,in, x , y Respectively represent any point on the contour line in the local coordinate system x Axis and y The coordinate values ​​on the axis, a 1 represents the outer contour line of the cross section of the main buoy (1) x 1 / 2 value of the width on the axis, b 1 represents the outer contour line of the cross section of the main buoy (1) y Height value on the axis; a 2 represents the outer contour line of the cross section of the heave plate (5) x 1 / 2 value of the width on the axis, b 2 represents the outer contour line of the cross section of the heave plate (5) y The height value on the axis is a1 / a2=b1 / b2, m1=n1, m2=n2, and m1, n1, m2 and n2 are all within the range of [1.50, 2.20]; the heave plate (5) is welded to the main buoy (1); the connection between the heave plate (5) and the main buoy (1) is smoothly transitioned; the number of main buoys (1) is 3-6; the thickness of the heave plate (5) is t The thickness of the main buoy (1) and the heave plate (5) is 25-60 mm; reinforcing ribs are provided at the connection between the main buoy (1) and the heave plate (5); and the surfaces of the main buoy (1), the diagonal brace (3), the transverse brace (4) and the heave plate (5) are all provided with an anti-corrosion layer.

2. An offshore semi-submersible wind turbine generator set, characterized in that: The offshore semi-submersible wind turbine foundation according to claim 1 is adopted, wherein the tower (2) is arranged on the central axis of the foundation, and the bottom of the tower (2) is connected to the main buoy (1) through a diagonal brace (3) and a transverse brace (4).

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