Full-submersible fan platform with high-stability mooring system

Abstract

The invention discloses a full-submersible type fan platform with a high-stability mooring system, and relates to the technical field of full-submersible type fan platforms, the full-submersible type fan platform comprises a platform, a fan and a hollow supporting table, and the supporting table is fixedly connected to the top of the platform; the electric push rod is controlled to work, the electric push rod can achieve rapid installation of the draught fan, meanwhile, the draught fan system is a full-submersible draught fan, compared with a conventional floating draught fan, a floating body of the full-submersible draught fan does not float on the sea surface but is submerged below the sea surface by a certain depth, and the submerged depth of the floating body avoids a sea wave action area; therefore, the influence of sea waves can be avoided to the greatest extent, and the load effect of the waves can be weakened during dynamic analysis. In addition, compared with a conventional floating type fan, due to the fact that the length of an anchor chain of a mooring system is reduced, the structural form of the floating type platform is simplified, and the construction investment cost is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of full-submersible wind turbine platform, and particularly relates to a full-submersible wind turbine platform with high-stability mooring system. BACKGROUND

[0002] In the prior art, there are mainly two kinds of offshore wind turbine platforms, namely fixed platform and floating platform. From the economic point of view, the former is only suitable for shallow water, and the latter is suitable for deep sea. According to the investigation, the reserves and stability of wind energy in the open sea are much higher than those in the near sea. Therefore, with the continuous development of offshore wind power research, it is inevitable for the wind turbine to move from the near sea to the open sea. The floating platform is more widely used in the design scheme of the foundation platform in the deep sea area because of the lower requirement for the geological conditions of the seabed and the flexible installation construction position.

[0003] The offshore floating wind turbine system is usually composed of an upper wind turbine, a tower, a floating foundation platform and a mooring system. The upper wind turbine, as the core of energy conversion, is composed of a wind wheel and a cabin to convert wind energy into electric energy. The tower is a connecting support structure designed in a steel cylinder. The floating foundation platform is a buoyancy carrier mainly used to carry the upper structure, resist wave load and maintain system stability. The mooring system restricts the platform displacement through the synergistic effect of anchor chain and anchoring device. Unlike the fixed wind turbine, the floating wind turbine faces complex marine environment, and in addition to wind load, the wind turbine system is also subjected to wave load and flow load. The wind turbine foundation platform with excellent hydrodynamic performance can effectively resist wave load and maintain the stability of the floating wind turbine during operation to ensure the power generation efficiency. Therefore, it is of great significance to develop a wind turbine foundation platform structure with excellent motion performance for offshore floating wind turbine.

[0004] The floating wind turbine is usually semi-submersible or Spar type. Although the operation conditions and construction techniques of different types of wind turbines are different, the floating foundation platforms of all types of wind turbines are out-of-water structures. In actual engineering application, the floating platform is subjected to the action of wind, wave and flow load for a long time. In order to ensure that the wind turbine equipment can operate stably on the sea for a long time, the coupling effect of wind, wave and flow should be considered when designing and dynamically analyzing all types of floating wind turbine systems. In addition, the wind turbine is not convenient to position.

[0005] Therefore, the present application provides a full-submersible wind turbine platform with high-stability mooring system to solve the above problems. SUMMARY

[0006] The present application aims to provide a full-submersible wind turbine platform with high-stability mooring system to solve the problems raised in the background.

[0007] To achieve the above object, the present application provides the following technical scheme: a fully-submerged fan platform with a high-stability mooring system, comprising a platform and a fan, the fully-submerged fan platform further comprising: a hollow support table fixedly connected to the top of the platform; an outer shell fixedly connected to the top of the support table; a hollow connecting seat fixedly connected to the bottom of the fan and movably connected to the outer shell; two clamping plates slidably connected to the inner wall of the bottom of the outer shell, and each clamping plate is in contact with the outer wall of the connecting seat, and the bottom of each clamping plate extends into the support table; the outer shell is provided with a mounting mechanism, and the top of the support table is provided with an auxiliary mechanism.

[0008] Preferably, the mounting mechanism comprises a gear, a rotating column and two racks, the gear is rotatably connected to the inner wall of the top of the support table, the rotating column is rotatably connected to the top of the gear and extends into the outer shell, the two racks are symmetrically slidably connected to the inner wall of the top of the support table and are in engagement with the gear, and the top of each rack is fixedly connected to the bottom of the adjacent clamping plate.

[0009] Further, the mounting mechanism moves by controlling the racks, at this time, the racks can control the gear to rotate synchronously, and when the gear rotates, the gear can control the rotating column to rotate, thereby assisting in positioning the connecting seat through the rotating column.

[0010] Preferably, the left inner wall of the support table is fixedly connected with an electric push rod, and the output end of the electric push rod is fixedly connected to the left side of the left rack.

[0011] Further, by arranging the electric push rod, the output end of the electric push rod can control the rack to move horizontally.

[0012] Preferably, the auxiliary mechanism comprises two extension plates, two sliding blocks, two connecting rods and an auxiliary ring, the two extension plates are symmetrically slidably connected to the inner wall of the bottom of the outer shell and extend out of the outer shell away from each other, the two sliding blocks are symmetrically slidably connected to the top of the support table and are fixedly connected to the sides of the two extension plates away from each other, the two connecting rods are rotatably connected to the front sides of the adjacent sliding blocks, and the auxiliary ring is fixedly sleeved on the outer wall of the fan and rotatably connected to the top of the two connecting rods.

[0013] Further, the auxiliary mechanism moves by controlling the extension plates, when the extension plates move, the extension plates can push the sliding blocks to move, with the movement of the sliding blocks, the sliding blocks can pull the connecting rods to move, when the connecting rods move, the connecting rods can pull the auxiliary ring to descend.

[0014] Preferably, the two extension plates are fixedly connected with driving plates on the side close to each other, and the two driving plates are arranged in an up-down manner, and the side away from each other of the two driving plates is fixedly connected with the outer wall of the adjacent clamping plate.

[0015] Further, when the clamping plate moves, the clamping plate can control the driving plate to move synchronously, so as to control the extension plate to move through the driving plate.

[0016] Preferably, the top of the support table is symmetrically provided with two sliding rails, and the two sliding blocks are slidingly connected with the adjacent sliding rails.

[0017] Further, by arranging the sliding rails, the sliding rails can assist the sliding blocks to move horizontally.

[0018] Preferably, the outer wall of the rotating column is fixedly connected with two limiting plates, and the two limiting plates are fixedly connected with the inner wall of the bottom of the connecting seat.

[0019] Further, when the limiting plate rotates with the rotation of the rotating column, the limiting plate can be in contact with the inner wall of the bottom of the connecting seat, so as to lock the connecting seat.

[0020] Preferably, the front side of the sliding block and the front side of the auxiliary ring are provided with rotating shafts, and the two ends of the connecting rod are fixedly connected with the inner wall of the adjacent rotating shaft.

[0021] Further, by arranging the rotating shafts, the rotating shafts can reduce the friction of the rotating connecting rod, so as to increase the service life of the connecting rod and facilitate work.

[0022] In summary, the technical effects and advantages of the present application are: 1. The connecting seat connected with the fan is inserted into the shell, at this time the electric push rod works to fix the connecting seat, thereby realizing the effect of installing the fan; 2. By pulling the auxiliary ring to descend, the auxiliary ring exerts a downward pressure on the fan, thereby ensuring the stability of the installation, adapting to the sea environment, and facilitating work; 3, Based on the steel consumption and RAO response of the platform, three kinds of shallow draft Spar type platforms are compared to select the structure of the full-submersible wind turbine platform, the RAO response of embodiment 1 is optimal in the pitch direction (the amplitude is significantly reduced), and the steel consumption is the most economical (1822.5t), and finally it is determined as the structure selection of the full-submersible wind turbine platform; through the cut-in, rated and cut-out wind speed of the 5MW wind turbine, combined with the wind speed-period joint distribution table of the selected working sea area, the calculation conditions of the present application are designed; in determining the negative buoyancy value of the submersible platform, the negative buoyancy value range is set as 5‰-14‰ of the total displacement, a total of 10 groups, the influence of different negative buoyancies on platform motion response and natural period under different working conditions is analyzed, and finally it is found that: when the negative buoyancy is less than 8‰ of the total displacement, increasing the negative buoyancy can significantly reduce the longitudinal response amplitude, but when the negative buoyancy exceeds 10‰ of the total displacement, it will lead to nonlinear growth of the anchor chain pretension, and instead intensify the pitch motion, finally the optimal negative buoyancy value of the full-submersible wind turbine platform in the present application is determined as 8‰ of the total displacement, at this time the anchor chain length is 503.53m, and the pretension is 1027621.438N.

[0023] The application works by controlling the electric push rod, which can realize the rapid installation of the wind turbine. Compared with the conventional floating wind turbine, the full-submersible wind turbine is submerged to a certain depth below the sea surface, and the submerged depth avoids the wave action area, so it can maximize the avoidance of the influence of the sea waves, and thus achieve the weakening of the wave load during dynamic analysis. In addition, compared with the conventional floating wind turbine, the full-submersible wind turbine reduces the anchor chain length of the mooring system and simplifies the structure of the floating platform, thereby greatly reducing the construction investment cost. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a structural section view of the embodiment of the application; Figure 2 It is a structural three-dimensional view of platform 1 of the embodiment of the application; Figure 3 It is a structural three-dimensional view of platform 2 of the embodiment of the application; Figure 4 It is a structural three-dimensional view of platform 3 of the embodiment of the application; Figure 5 It is a structural top view of the slide rail and the sliding block of the embodiment of the application; Figure 6 It is a structural top view of the clamping plate, the driving plate and the extension plate of the embodiment of the application; Figure 7 It is a structural three-dimensional view of the gear, the rotating column and the limiting plate of the embodiment of the application; Figure 8 It is a mooring scheme setting diagram of platform 1 of the embodiment of the application; Figure 9 mooring arrangement for platform 2 of the embodiment of the present application; Figure 10 mooring arrangement for platform 3 of the embodiment of the present application; Figure 11 RAO surge of the embodiment of the present application; Figure 12 RAO heave of the embodiment of the present application; Figure 13 RAO pitch of the embodiment of the present application; Figure 14 submersible platform size of the embodiment of the present application; Figure 15 anchor chain length corresponding to different negative buoyancy of the embodiment of the present application; Figure 16 pre-tension corresponding to different negative buoyancy of the embodiment of the present application; Figure 17 submersible wind turbine surge corresponding to different negative buoyancy of the embodiment of the present application; Figure 18 submersible wind turbine heave corresponding to different negative buoyancy of the embodiment of the present application; Figure 19 submersible wind turbine pitch corresponding to different negative buoyancy of the embodiment of the present application; Figure 20 influence of different negative buoyancy on the motion response of the submersible wind turbine and the anchor chain tension under LC5 working condition of the embodiment of the present application; Figure 21 influence of different negative buoyancy on the motion response of the submersible wind turbine and the anchor chain tension under LC6 working condition of the embodiment of the present application; Figure 22 influence of different negative buoyancy on the motion response of the submersible wind turbine and the anchor chain tension under LC7 working condition of the embodiment of the present application; Figure 23 mooring arrangement of the embodiment of the present application; Figure 24 mooring arrangement and anchor chain numbering of the embodiment of the present application; Figure 25 steel consumption comparison of three platforms of the embodiment of the present application.

[0025] In the figure: 1, platform; 2, support table; 3, outer shell; 4, electric push rod; 5, rack; 6, gear; 7, rotating column; 8, connecting seat; 9, wind turbine; 10, clamping plate; 11, driving plate; 12, extension plate; 13, slide rail; 14, sliding block; 15, connecting rod; 16, auxiliary ring. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application. Embodiment 1

[0027] Reference Figures 1-25 The present embodiment provides a full-submersible wind turbine platform with a high-stability mooring system, which comprises a platform 1 and a wind turbine 9. The full-submersible wind turbine platform further comprises: An internally hollow support table 2 is fixedly connected to the top of the platform 1. An outer shell 3 is fixedly connected to the top of the support table 2. An internally hollow connecting seat 8 is fixedly connected to the bottom of the wind turbine 9, and the connecting seat 8 is movably connected to the outer shell 3. Two clamping plates 10 are slidably connected to the inner wall of the bottom of the outer shell 3, and the two clamping plates 10 are in contact with the outer wall of the connecting seat 8. The bottom of the two clamping plates 10 extends into the support table 2. The outer shell 3 is provided with a mounting mechanism, and the top of the support table 2 is provided with an auxiliary mechanism.

[0028] In the present embodiment, the mounting mechanism comprises a gear 6, a rotating column 7 and two racks 5. The gear 6 is rotatably connected to the inner wall of the top of the support table 2. The rotating column 7 is rotatably connected to the top of the gear 6, and the top of the rotating column 7 extends into the outer shell 3. The two racks 5 are symmetrically slidably connected to the inner wall of the top of the support table 2, and the two racks 5 are in mesh with the gear 6. The top of the two racks 5 is fixedly connected to the bottom of the adjacent clamping plate 10. The mounting mechanism moves by controlling the rack 5. At this time, the rack 5 can synchronously control the gear 6 to rotate. When the gear 6 rotates, the gear 6 can control the rotating column 7 to rotate, thereby assisting in positioning the connecting seat 8 through the rotating column 7.

[0029] In the present embodiment, an electric push rod 4 is fixedly connected to the left inner wall of the support table 2, and the output end of the electric push rod 4 is fixedly connected to the left side of the left rack 5. By arranging the electric push rod 4, the output end of the electric push rod 4 can control the rack 5 to move horizontally.

[0030] In the embodiment, the auxiliary mechanism comprises two extension plates 12, two sliding blocks 14, two connecting rods 15 and an auxiliary ring 16, the two extension plates 12 are symmetrically and slidingly connected to the inner wall of the bottom of the shell 3, and the sides away from each other of the two extension plates 12 extend to the outside of the shell 3, the two sliding blocks 14 are symmetrically and slidingly connected to the top of the support table 2, and the sides close to each other of the two sliding blocks 14 are fixedly connected to the sides away from each other of the two extension plates 12, the two connecting rods 15 are rotationally connected to the front sides of the adjacent sliding blocks 14, the auxiliary ring 16 is fixedly sleeved on the outer wall of the fan 9, and the front side of the auxiliary ring 16 is rotationally connected to the top of the two connecting rods 15, the auxiliary mechanism moves by controlling the extension plates 12, when the extension plates 12 move, the extension plates 12 can push the sliding blocks 14 to move, with the movement of the sliding blocks 14, the sliding blocks 14 can pull the connecting rods 15 to move, and when the connecting rods 15 move, the connecting rods 15 can pull the auxiliary ring 16 to descend.

[0031] In the embodiment, the sides close to each other of the two extension plates 12 are fixedly connected with driving plates 11, and the two driving plates 11 are arranged in an up-down mode, and the sides away from each other of the two driving plates 11 are fixedly connected with the outer walls of the adjacent clamping plates 10, when the clamping plates 10 move, the clamping plates 10 can synchronously control the driving plates 11 to move, so as to control the extension plates 12 to move through the driving plates 11.

[0032] In the embodiment, the top of the support table 2 is symmetrically provided with two sliding rails 13, and the two sliding blocks 14 are slidingly connected with the adjacent sliding rails 13, and the sliding rails 13 play an auxiliary role in the transverse movement of the sliding blocks 14.

[0033] In the embodiment, the outer wall of the rotating column 7 is fixedly connected with two limiting plates, and the two limiting plates are fixedly connected with the inner wall of the bottom of the connecting seat 8, when the limiting plates rotate with the rotation of the rotating column 7, the limiting plates can be in contact with the inner wall of the bottom of the connecting seat 8, so as to lock the connecting seat 8.

[0034] In the embodiment, the front side of the sliding block 14 and the front side of the auxiliary ring 16 are provided with shafts, and the two ends of the connecting rod 15 are fixedly connected with the inner walls of the adjacent shafts, the shafts can reduce the friction of the rotation of the connecting rod 15, so as to increase the service life of the connecting rod 15 and facilitate work. Embodiment 2

[0035] In order to determine the excellent platform shape, the hydrodynamic performance of the fan platform with the following three shapes is compared, and the reference Figures 2-4The selected platform 1, platform 2 and platform 3, in order to only compare the influence of its structure shape on the hydrodynamic performance, so in addition to the shape, the basic parameters of each platform are kept consistent as much as possible, through the scaling of the same proportion, their displacement is controlled at about 18000t, the platform manufacturing material is alloy steel with a density of 7850kg / m³, the wall thickness is uniformly designed as 50mm, at the same time, the mass of each platform counterweight is adjusted, so that the total mass of each platform is as consistent as possible, the ballast material uses concrete with a density of 2392kg / m³, for the estimation of the centroid and inertia moment of the platform, the Static Structural module in Solidworks or ANSYS Workbench can be used for calculation, according to the designed platform structure size, a three-dimensional model is established in the modeling software, and the material properties and wall thickness parameters of each component are defined, then, using the built-in mass analysis function of the software, the centroid coordinates and inertia moment data of the wind turbine platform can be calculated:

[0036] The steel consumption accounts for 20%-30% of the total investment of the floating wind turbine, which is the key parameter to measure the platform economy, the steel consumption of the submersible wind turbine platform affects the platform economy, structural performance and construction feasibility, reasonable steel consumption can reduce the manufacturing cost, at the same time ensure the safety and stability of the platform in complex marine environment, the steel consumption of the three platforms is compared as shown in Figure 25 The steel consumption of platform 1 is the least, only 1822.5 tons, and the steel consumption of platform 3 is the most, which is 3001.7 tons, because the structure is the most complex.

[0037] In order to exclude the influence of mooring system on the dynamic performance of different structure platforms, the same mooring mode is used for the three platforms as much as possible, the mooring scheme of different platforms is shown, and the mooring radius is 500m, the guide hole is set at 6m below the horizontal plane.

[0038]

[0039] When calculating the RAO of the three platforms, the calculation environment condition is set as water depth 100m, regular wave frequency range 0.1-2.0rad / s, step 0.1rad / s, the draft of the three platforms is 50m, that is, the full immersion state, the RAO calculation results of the three platforms are shown in Figures 11-13 .

[0040] The hydrodynamic performance of the three platforms can be preliminarily judged by comparing and analyzing the three-degree-of-freedom response amplitude operators (RAOs) of the platforms under different wave frequencies and different wave direction angles. In the surge direction, the change laws of the three platforms are consistent, and the RAOs of the platforms decrease first with the increase of the wave frequency. In the heave direction, the change laws of platform 1 and platform 2 are basically the same, and the RAOs decrease first, then increase, and finally decrease again with the increase of the wave frequency, while the RAO of platform 3 increases first and then decreases with the increase of the frequency. In the pitch direction, the RAOs of the three platforms increase first and then decrease with the increase of the wave frequency, but the values have a relatively obvious difference. The pitch angle of platform 1 is the smallest, and that of platform 2 is the largest. The relatively large values of the RAOs of the three platforms are mainly concentrated in the low-frequency wave region. This is because the natural frequency of the column type platform in the three degrees of freedom is low, and the three new types of shallow draught Spar type platforms essentially belong to the column type structure category, so they are also prone to resonance with low-frequency waves, and thus the relatively large values of the RAOs are concentrated in the low-frequency band.

[0041] By comparing the total steel consumption and the RAO response of the three fan platforms, it can be found that the responses of the three platforms in the surge and heave directions are basically the same, but the difference in the pitch direction is relatively obvious. Platform 1 has the least steel consumption, and the RAO in the pitch direction performs best. Therefore, the subsequent fully submerged fan platform is designed with the shape structure of platform 1 as a reference, and the base size of the fully submerged fan platform is finally determined. Since the subsequent discussion of the negative buoyancy and the value of the diving depth of the fully submerged platform will affect the mass, displacement and moment of inertia parameters of the fully submerged fan platform, only the shape size of the fully submerged fan platform is given here, as shown in FIG. 8. The draught depth is temporarily set to 60+Dm. Figure 14

[0042] The negative buoyancy is a key parameter in the design of the fully submerged fan, which increases the pre-tension of the mooring system to provide a larger restoring moment to suppress the surge and pitch motion, especially when the wave period is close to the natural frequency of the platform to avoid resonance. However, the size of the negative buoyancy also directly affects the anchor chain pre-tension. Excessive negative buoyancy may cause the anchor chain to be at risk of breaking, so it is necessary to balance the relationship between motion suppression and mooring fatigue life. From the economic point of view, excessive negative buoyancy requires greater anchor chain tension to balance, increasing the weight and cost of the anchor chain. Too small may not effectively reduce the wave load, and the critical value needs to be found through optimization design.

[0043] ​This section determines the platform negative buoyancy based on the platform motion response and mooring chain tension: modify the platform mass property, adjust to the target negative buoyancy by changing the ballast mass (such as concrete blocks), calculate the vertical component of the anchor according to the negative buoyancy, dynamically adjust the initial pretension of the mooring system, ensure that the platform position in the static equilibrium state is consistent with the designed diving depth, in the FAST-AQWA joint simulation, the negative buoyancy is used as the initial condition in the time domain calculation, which affects the platform dynamic response under the action of wind and wave coupling, the range of negative buoyancy is from 5‰ to 14‰ of the total displacement, a total of 10 mooring schemes, the anchor length and pretension change with the negative buoyancy as shown in the figure, when the mooring radius and mooring material are determined, as the negative buoyancy increases, the anchor length needs to be reduced to increase the pretension, and then increase the vertical downward force to balance the negative buoyancy, as the negative buoyancy increases, the pretension also increases, and the curve slope gradually increases, indicating that when the negative buoyancy increases to a certain extent, the growth rate of the pretension will be larger and larger, the wind turbine system mass corresponding to different negative buoyancy and anchor length and pretension are shown in Figures 15-16 .

[0044]

[0045] The environmental load refers to the load caused directly or indirectly by the external environment, generally including wind, wave and current loads. In this paper, the average water depth of the wind turbine operation sea area is 100 m, and the wave energy spectrum characteristics of the selected sea area have high consistency with the JONSWAP spectrum type, so irregular waves are generated by the JONSWAP spectrum. When calculating irregular wave conditions, the actual operation of the wind turbine should be considered, that is, the cut-in wind speed, rated wind speed and cut-out wind speed of the wind turbine should be considered. The wind speed conditions are set to 3 m / s, 11.4 m / s and 25 m / s respectively. Combined with the wind speed-period joint distribution table of the selected sea area in recent years, the following four regular wave conditions and three irregular wave conditions are set for subsequent analysis.

[0046] In the simulation analysis, all design conditions are wind and wave in the same direction. Due to the symmetry of the wind turbine platform, only the condition of wind and wave incident angle of 0° is considered in this chapter, at this time the tension of anchor chain 1 is the largest.

[0047] When the mooring radius and mooring material are constant, as the value of the full-submersible wind turbine platform negative buoyancy increases, the pretension of the wind turbine mooring chain becomes larger, and finally the natural period in the three degrees of freedom directions will gradually decrease, but basically it can avoid the wave period of the selected sea area.

[0048] In order to study the influence of negative buoyancy on the motion response of the fully-submersible wind turbine, simulation and calculation are carried out under the cut-in wind speed condition (LC5), the rated wind speed condition (LC6) and the cut-out wind speed condition (LC7) respectively. The wind wave incidence angle is set to 0°, the mooring radius is kept at 500 m, the position of the fairlead is unchanged, the size of the negative buoyancy of the wind turbine platform is changed by changing the proportion of the negative buoyancy in the total displacement of the platform, the complete dynamic process of 3600 seconds (1 hour) is simulated, the influence mechanism of the negative buoyancy design on the three-degree-of-freedom motion response of the fully-submersible platform is investigated, and the box plot of the influence of different negative buoyancies on the surge, heave, pitch and anchor chain 1 tension response of the fully-submersible wind turbine under the LC5 condition is shown in Figure 21 .

[0049] The box plot of the influence of different negative buoyancies on the surge, heave, pitch and anchor chain 1 tension response of the fully-submersible wind turbine under the LC6 condition is shown in Figure 22

[0050] Under the LC5 and LC6 conditions, the overall trend of the motion response of the fully-submersible wind turbine platform in three degrees of freedom and the tension response of the anchor chain 1 is similar with different negative buoyancies. By analyzing the influence of different negative buoyancies on the surge motion response, it can be found that with the increase of the negative buoyancy of the fully-submersible wind turbine platform, the mean value of the surge motion gradually decreases. Under the LC5 condition, when the proportion of the negative buoyancy increases from 5‰ to 9‰, the mean value decreases more obviously, and after 9‰, the decreasing trend of the mean value weakens, the change of the mean value caused by the negative buoyancy is limited. Under the LC6 condition, when the proportion of the negative buoyancy increases from 5‰ to 10‰, the mean value decreases more obviously, and after 10‰, the decreasing trend of the mean value weakens. For the amplitude of the surge motion, under the LC5 condition, when the negative buoyancy increases from 5‰ to 9‰, the amplitude of the surge motion decreases with the increase of the negative buoyancy, and when it increases from 10‰ to 14‰, the amplitude of the surge motion increases with the increase of the negative buoyancy. Under the LC6 condition, when the negative buoyancy increases from 5‰ to 10‰, the amplitude of the surge motion decreases with the increase of the negative buoyancy, and when it increases from 11‰ to 14‰, the amplitude of the surge motion increases with the increase of the negative buoyancy.

[0051] By analyzing the influence of different negative buoyancies on the heave motion response under the LC5 and LC6 conditions, it can be found that in the heave direction, the amplitude of the motion response of the fully-submersible platform slightly decreases with the increase of the negative buoyancy, but the change of the negative buoyancy does not affect the mean value of the motion response in two degrees of freedom. Overall, the change of the negative buoyancy has a weak influence on the heave motion response of the fully-submersible wind turbine platform.

[0052] By analyzing the influence of different negative buoyancies on the pitch motion response under the LC5 and LC6 conditions, it can be found that in general, the amplitude of the pitch motion response under the two conditions first decreases and then increases with the increase of the negative buoyancy, and the change under the LC6 condition is more obvious. For the mean value of the pitch motion, the change of the negative buoyancy does not affect the mean value of the motion response in two degrees of freedom.​

[0053] When the wave angle is 0°, the tension of anchor chain 1 is the largest among the three anchor chains, so only the tension response results of anchor chain 1 are shown. The influence of different negative buoyancy on the tension response of anchor chain 1 under the two working conditions is analyzed. With the increase of negative buoyancy, the mean value and amplitude of the tension response of anchor chain 1 will gradually increase, and the growth trend will also become larger and larger. The maximum tension under the rated wind speed working condition is greater than the maximum tension under the corresponding cut-in wind speed working condition.

[0054] The box plot of the influence of different negative buoyancy on the surge, heave, pitch and tension response of anchor chain 1 of the fully-submerged wind turbine under LC7 working condition is shown in FIG. 8. Figure 20

[0055] LC7 working condition is the cut-out wind speed working condition. Under this working condition, the wind turbine is pitched, and the wind load on the upper structure of the fully-submerged wind turbine is greatly reduced. The wave load plays a leading role in the external load. From the influence of different negative buoyancy on the surge motion response under this working condition, it can be found that, unlike the working condition, with the increase of the negative buoyancy of the fully-submerged wind turbine platform, the amplitude of the surge motion gradually increases from 8‰, while the corresponding mean value of the surge motion changes little.

[0056] The analysis of the influence of different negative buoyancy on the heave motion response under LC7 working condition is the same as the previous two working conditions. Different negative buoyancies have little influence on the amplitude and mean value of the heave motion response.

[0057] The analysis of the influence of different negative buoyancy on the pitch motion response under LC7 working condition shows that, under the cut-out wind speed working condition, the wave has a large wave height and period, and the wave load generated is also large. At this time, increasing the negative buoyancy of the fully-submerged wind turbine platform will make the anchor chain pre-tension too large. Under the large wave load, the amplitude of the pitch motion response will increase with the increase of the negative buoyancy, but since the influence of the wind load is small, the mean value of the pitch motion response is near 0°.

[0058] For the fully-submerged wind turbine system, a reasonable negative buoyancy setting can resist external loads and effectively improve the surge and pitch motion responses of the wind turbine system, but has limited influence on the heave motion response. If the negative buoyancy is too small, the platform surge displacement will increase, the load resistance will weaken, and the system will be prone to instability. If the negative buoyancy is too large, the anchor chain pre-tension will be too large, which may cause damage to the anchor chain or excessive constraint of the platform, resulting in an increase in the pitch motion response and overall instability of the system. Therefore, the best negative buoyancy of the platform in this paper is determined to be 8‰ of the total displacement by combining the platform motion response and the anchor chain tension under the three working conditions.

[0059] When designing the mooring system, the horizontal displacement of the platform should be considered to avoid breaking of the power cable due to large displacement during platform operation. At present, there is no clear specification to limit the horizontal displacement limit value for offshore wind turbine platforms. Generally, the provisions of traditional oil and gas platforms are referred to:​

[0060] Different from oil and gas platforms, offshore wind turbine platforms usually have no production and living facilities, so the horizontal offset limit can be appropriately relaxed: 5%~8% of the maximum water depth under the rated operating condition, and 8%~15% of the maximum water depth under the survival condition.

[0061] Excessive pitch angle will cause instability of the wind turbine platform and a sharp increase in the dynamic tension of the anchor chain. In order to ensure the power generation efficiency and the safety of the platform structure, the pitch angle of the offshore wind turbine in operation also needs to be limited. According to the DNVGL-ST-0119 Offshore Wind Turbine Structures Standard, the pitch angle of the floating wind turbine platform needs to meet the following strict requirements in the design: under normal operating conditions, the platform pitch angle should not exceed ±8° (dynamic fluctuation range based on 10-minute average), and the annual average should be controlled within ±5°; under the 50-year extreme survival condition, the instantaneous peak value is allowed to reach ±15°.

[0062] In order to ensure the safety of the mooring anchor chain during the operation of the wind turbine system, and at the same time not to have too long a mud drag section, considering the economy of the wind turbine platform, the tension of the mooring anchor chain is also required accordingly. The anchor chain tension is limited by the mooring tension safety factor, which is specifically specified as follows: the maximum breaking force (MBS) of the anchor chain divided by the maximum tension of the anchor chain during the operation of the platform.

[0063]

[0064] In the formula: P B is the maximum breaking force of the anchor chain, T MAX is the maximum tension of the anchor chain during operation.

[0065] The CCS Offshore Mobile Platform Classification Standard stipulates that the mooring safety factor a≥2.25 under operating conditions, a≥1.67 under survival conditions, and a≥1.25 under damaged state:

[0066] The length of the anchor chain is mainly related to the mooring form and the anchor used. The catenary mooring usually uses a drag anchor that relies on horizontal drag force to provide grip, so a long enough mud drag section needs to be reserved to prevent the wind turbine platform from being dislodged when the horizontal offset reaches the maximum. However, too long a mud drag section will cause waste. The estimated empirical formula at the initial design stage is: or

[0067] In the formula: L is the length of the anchor chain;H To design the water depth.

[0068] As the key core subsystem of offshore floating wind turbine, the performance of mooring system directly affects the safety and stability of the whole wind turbine system. Under the action of complex and changeable marine environmental loads, if there is no effective constraint of the mooring system, the floating platform will produce large displacement of six degrees of freedom, which not only leads to significant reduction of power generation efficiency, but also may cause serious accidents such as platform collision, structural damage and overturning. Through the reasonable design of mooring system, the motion response of the platform under extreme sea conditions can be effectively suppressed, and the platform displacement can be controlled within the safety threshold range, so as to ensure that the wind turbine can maintain stable working state and optimal power generation performance under various environmental conditions. For offshore wind turbine system, catenary and tension type are commonly used for mooring. In the sea area with water depth less than 1000m, considering the economy and safety comprehensively, catenary mooring system is more preferred.

[0069] In this paper, the number of submersible wind turbine platform anchor chains is 3, the included angle between the three anchor chains is 120°, the fairlead is at 18.25+Dm below the water surface, and the mooring arrangement and anchor chain number Figures 23-24 .

[0070]

[0071] Working principle: in actual work, by connecting the connecting seat 8 with fan 9 is inserted into the shell 3, while guiding the rotating column 7 extends to the connecting seat 8, at this time by controlling the electric push rod 4 work, electric push rod 4 can push rack 5 to move, when the rack 5 moves, rack 5 can synchronous gear 6 to rotate, at this time with the rotation of gear 6, gear 6 can synchronous control right rack 5 to the left to move, by controlling the movement of two rack 5, two rack 5 can synchronous drive two clamping plate 10 close to each other, at this time two clamping plate 10 can move to clamp the connecting seat 8 fixed, while with the rotation of gear 6, gear 6 can synchronous drive rotating column 7 to rotate, when rotating column 7 rotates, rotating column 7 can drive two limit plate to rotate, limit plate rotation can with the bottom of the connecting seat 8 inner wall contact, limit the movement of connecting seat 8, realize the effect of stable installation of fan 9, while with the movement of clamping plate 10, clamping plate 10 can control two drive plate 11 to move, when two drive plate 11 moves, drive plate 11 can push two extension plate 12 to the outside of the shell 3 to move, when the extension plate 12 moves, extension plate 12 can push two sliding block 14 away from each other, when the sliding block 14 moves, sliding block 14 can pull two connecting rod 15 to move, while with the movement of two connecting rod 15, two connecting rod 15 can pull the auxiliary ring 16 down, when the auxiliary ring 16 down, auxiliary ring 16 can exert pressure on the fan 9, further guarantee the stability of installation.

[0072] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the foregoing detailed description of the present application is made with reference to the foregoing embodiments, for the skilled in the art, it still can be modified, or part of the technical features of the equivalent replacement, within the spirit and principles of the present application, any modification, equivalent replacement, improvement, etc., should be included in the scope of protection of the present application.

Claims

1. A fully submersible wind turbine platform with a high stability mooring system, comprising a platform (1) and a wind turbine (9), characterized in that, The fully-submerged fan platform further comprises: An internally hollow support table (2) fixedly connected to the top of the platform (1); An outer shell (3) fixedly connected to the top of the support table (2); An internally hollow connecting seat (8) fixedly connected to the bottom of the fan (9) and movably connected to the outer shell (3); Two clamping plates (10) slidably connected to the inner wall of the bottom of the outer shell (3) and each in contact with the outer wall of the connecting seat (8), the bottom of each of the two clamping plates (10) extending into the support table (2); The outer shell (3) is provided with a mounting mechanism, and the top of the support table (2) is provided with an auxiliary mechanism.

2. A fully submersible wind turbine platform having a high stability mooring system as claimed in claim 1, wherein, The mounting mechanism comprises a gear (6), a rotating column (7) and two racks (5), the gear (6) is rotatably connected to the inner wall of the top of the support table (2), the rotating column (7) is rotatably connected to the top of the gear (6) and extends into the outer shell (3), and the two racks (5) are symmetrically slidably connected to the inner wall of the top of the support table (2) and each in engagement with the gear (6), the top of each of the two racks (5) being fixedly connected with the bottom of the adjacent clamping plate (10).

3. A fully submersible wind turbine platform having a high stability mooring system as claimed in claim 2, wherein, The left inner wall of the support table (2) is fixedly connected with an electric push rod (4), and the output end of the electric push rod (4) is fixedly connected with the left rack (5).

4. A fully submersible wind turbine platform having a high stability mooring system as claimed in claim 1, wherein, The auxiliary mechanism comprises two extension plates (12), two sliding blocks (14), two connecting rods (15) and an auxiliary ring (16), the two extension plates (12) are symmetrically slidably connected to the inner wall of the bottom of the outer shell (3) and each extends out of the outer shell (3), the two sliding blocks (14) are symmetrically slidably connected to the top of the support table (2) and each of the two sliding blocks (14) is fixedly connected with the side of the two extension plates (12) away from each other, the two connecting rods (15) are rotatably connected to the front side of the adjacent sliding blocks (14), and the auxiliary ring (16) is fixedly sleeved on the outer wall of the fan (9) and rotatably connected with the top of the two connecting rods (15) on the front side.

5. A fully submersible wind turbine platform having a high stability mooring system as claimed in claim 4, wherein, Each of the two extension plates (12) is fixedly connected with a driving plate (11) on the side close to each other, and the two driving plates (11) are arranged in an up-down manner, and each of the two driving plates (11) is fixedly connected with the outer wall of the adjacent clamping plate (10) on the side away from each other.

6. A fully submersible wind turbine platform having a high stability mooring system as claimed in claim 4, wherein, The top of the support table (2) is symmetrically provided with two sliding rails (13), and the two sliding blocks (14) are slidably connected with the adjacent sliding rails (13).

7. A fully submersible wind turbine platform having a high stability mooring system as claimed in claim 2, wherein, The outer wall of the rotating column (7) is fixedly connected with two limiting plates, and the two limiting plates are fixedly connected with the inner wall of the bottom of the connecting seat (8).

8. A fully submersible wind turbine platform having a high stability mooring system as claimed in claim 1, wherein, The front side of the sliding block (14) and the front side of the auxiliary ring (16) are each provided with an axis, and the two ends of the connecting rod (15) are each fixedly connected with the inner wall of the adjacent axis.

Images