Flexible offshore floating photovoltaic structure full-size mechanical analysis method

Abstract

The present application relates to the technical field of photovoltaic equipment, and discloses a flexible offshore floating photovoltaic structure full-size mechanical analysis method, comprising: establishing a floating photovoltaic geometric model, and performing multi-scale structure discretization based on stress characteristics, calculating the local adaptive time step and the global time step of various components; for all component types i units, respectively repeating displacement vector, internal force and external force solution; synchronizing particles on the global time; calculating and integrating the sum of particle external force and internal force vectors; judging whether the Z coordinate of the center point of the cable net structure satisfies the stop iteration condition, and obtaining the geometric configuration of the structure under the action of the steady state. The scheme is based on the stress characteristics of each component to perform multi-scale structure discretization, introduces an adaptive time step mechanism and an asynchronous computing mechanism, and realizes efficient calculation of the full-size mechanical response of the structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic devices, in particular to a full-size mechanical analysis method for a flexible offshore floating photovoltaic structure. BACKGROUND

[0002] At present, in order to build a new power system with new energy as the main body, the new energy industry needs rapid development, and photovoltaic power generation has become a key growth point. The traditional land-based photovoltaic power faces core challenges: large-scale land use intensifies land competition and pushes up costs, especially in the western region, although the resources are abundant, but due to insufficient local consumption, it leads to serious light abandonment; and the east with strong power demand is restricted by high loss and high difficulty of long-distance power transmission.

[0003] Therefore, the land-intensive floating photovoltaic power has attracted attention. In inland waters, although this technology has once developed rapidly, it has been strictly limited by ecological protection policies in recent years, and the development space is relatively limited. At the same time, the vast sea area has become a new focus of new energy development due to its rich wind and light resources, and the commercialization prospect of offshore floating photovoltaic power is very broad. However, offshore floating photovoltaic power is still in its early stages of development. One of the main technical challenges is: the complex nonlinear interaction mechanism of the harsh wind and wave flow environment and the floating structure, especially the flexible structure needs to be further studied, and the existing flexible offshore photovoltaic structure analysis method faces higher requirements.

[0004] As a new form of offshore photovoltaic structure, the mechanical behavior of the flexible offshore floating photovoltaic structure under the action of environmental load embodies the following characteristics: first, it involves the coupling of multiple components, and the entire force transmission path includes floating units, soft connection ropes, longitudinal and transverse cable nets, rigid outer frames, and mooring cables; rigid and flexible components are alternated, floating units and outer frames belong to rigid components, soft connection ropes, longitudinal and transverse cable nets, and mooring cables belong to flexible components, and loads are alternately transmitted in rigid and flexible components; third, the degree of nonlinearity is high, the characteristics of the mooring cable determine its large deformation and the large displacement of the water surface structure, at the same time, the mechanical behavior of the flexible cable net structure and the soft connection rope also presents great geometric nonlinearity. The complex force transmission path of multiple components and the strong nonlinear mechanical behavior in the force transmission process determine the complexity of the full-size mechanical analysis of the flexible floating photovoltaic structure. The traditional finite element method has the problem of calculation divergence when dealing with the above problems. SUMMARY

[0005] The present application aims to provide a full-size mechanical analysis method for a flexible offshore floating photovoltaic structure to solve the problem of complexity and calculation divergence of the traditional finite element method in the full-size analysis of the flexible floating photovoltaic structure.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: a full-size mechanical analysis method for a flexible offshore floating photovoltaic structure, comprising:

[0007] Step 1: Establish the geometric model of the floating photovoltaic system;

[0008] Step 2: Discretize the scale structure based on the force characteristics to form particles and connecting elements; use rod elements to simulate the photovoltaic pontoon, use cable elements to simulate the longitudinal and transverse cable nets and mooring cables, use relaxed cable element models to simulate flexible connecting ropes, and use beam elements to simulate the rigid outer frame; wherein, the modeling geometric length of the relaxed cable element model is the geometric straight line length between the corner point of the photovoltaic pontoon and the cable net node;

[0009] Step 3: Assign material properties to each type of component;

[0010] Step 4: Calculate the local adaptive time step and global time step for various components;

[0011] Step 5: Apply boundary conditions and loads to distribute the loads equally to the relevant particles;

[0012] Step 6: Calculate the displacement vector of each particle within each component type i;

[0013] Step 7: Calculate and integrate the unit internal and external forces of the particles in each component;

[0014] Step 8: Repeat for each component type i. Next step 6~7;

[0015] Step 9: Execute Step 6 again, at which point all particles are synchronized in global time;

[0016] Step 10: Coordinate the positions of particles at the joints of different components;

[0017] Step 11: Calculate and integrate the unit internal forces and external forces of the particles of each component. In this step, the internal force of the particle at the connection is the sum of the internal force vectors of the units of different component types acting on the particle.

[0018] Step 12: Determine whether the difference between the Z coordinates of the center point of the cable net structure and the two adjacent global time steps ΔT is less than the preset value. If this stopping iteration condition is not met, repeat steps 5 to 11 above until the stopping iteration condition is met, and complete the geometric configuration of the structure under steady-state action.

[0019] The flexible offshore floating photovoltaic structure has five types of components, including photovoltaic floating boxes, cable net structures, soft connection ropes, rigid outer frames and mooring cables. The distributed array of photovoltaic floating boxes as the main force component has small deformation under the action of wind, wave and current and can be regarded as a rigid component, which is simulated by a rod element. The vertical and horizontal cable net and mooring cable are force transmission components and can only bear tension but not pressure, and have large displacement and deformation characteristics under stress, which are simulated by a cable element. For the soft connection rope, a new cable element model, i.e., a slack cable element model, is established according to the above characteristics. The geometric length of the model is the geometric straight line length between the corner point of the photovoltaic floating box and the node of the cable net (the length is referred to as 1 times length). The vertical and horizontal cable net is connected to the rigid outer frame at both ends, and the rigid outer frame needs to ensure sufficient rigidity to ensure the stability of the cable net grid, which is simulated by a beam element. The present scheme is based on the stress characteristics of each component to discretize the multi-scale structure and establish a finite particle model of the flexible offshore floating photovoltaic structure, and introduces an adaptive time step mechanism and an asynchronous computing mechanism to realize efficient calculation of the full-size mechanical response of the structure.

[0020] Preferably, the calculation method of the internal force of the slack element model is as follows: the unstressed length L0 of the slack element is set to λ times the length, and each time the internal force of the element is calculated, the relationship between the length L of the element and the unstressed length L0 is determined first. If the element length L < L0, the internal force is forced to be 0, indicating that the soft connection rope is still in a relaxed state at this time; when L > L0, the internal force is calculated according to the elongation L-L0 of the slack element. Since the soft connection rope has a slack characteristic, a slack element model is established in the present scheme in combination with its stress characteristics to better simulate the actual soft connection rope structure, so that the final stress analysis result is more accurate.

[0021] Preferably, step 4 specifically comprises: for each type of component, based on the length, material density and Young's modulus of the discrete elements of the component, a minimum stable time step Δt shared by all elements of each type of component is determined in turn as a local adaptive step size of each type of component; the global time step ΔT i is calculated according to the local adaptive time steps Δt of each type of component, i and the ratio of the global time step ΔT to each local time step Δt is calculated.

[0022] Preferably, the local adaptive step size of each type of component in step 4 needs to satisfy the following conditions:

[0023]

[0024] In the formula, ρ i is the material density of the i-type component, E i is the material Young's modulus, and l i is the element length.

[0025] Preferably, the step 6 specifically comprises:

[0026] Step 61: for each particle within each component type i, using central difference method to calculate the particle displacement vector with its local time step for time increment, explicit step to calculate particle displacement vector, the formula is as follows:

[0027]

[0028] In the formula, represents the displacement vector of particle J at time+Δt i moment, F J is the resultant force vector suffered by particle J, C1, C2 are calculation coefficients related to damping, is the equivalent mass of unit assigned to point J;

[0029] Step 62: for the particles connected with rigid frame unit, further calculate the angular displacement of the particle, the formula is as follows:

[0030]

[0031] In the formula, represents the angular displacement of particle J at time+Δt i moment, M J is the resultant moment suffered by particle J, is the equivalent moment of inertia of unit assigned to point J.

[0032] Preferably, the step 7 comprises:

[0033] Step 71: based on the pure deformation of unit and material constitutive relation, calculate the internal force increment of unit, and then superimpose with the initial internal force of unit, so as to obtain the internal force of unit, the specific formula is as follows: , in the formula, K is the stiffness matrix of unit, Δ is the pure deformation of unit; wherein, the internal force of rigid frame unit also includes the bending moment internal force of unit, the formula is as follows: , in the formula represents the internal force vector of unit at time moment, represents the bending moment of unit at time moment;

[0034] Step 72: accumulate the internal force and external force of all units to the particle, the resultant force suffered by particle is:

[0035] , in the formula P J is the external force vector suffered by particle J, is the internal force vector of unit a connected with particle J;

[0036] wherein the resultant of the rigid frame units also includes the resultant moment it receives, and the specific formula is:

[0037] wherein Q J is the external bending moment received by particle J, is the internal bending moment of unit a connected with particle J.

[0038] Preferably, in step 7, when the local time step of the particle in the i-type component is performed within a global time step, the internal force of the unit of other type components received by the particle at the connection is directly taken as the internal force of the unit calculated at the last integral multiple global time step node , k is an integer and time represents the time node at which the particle is currently located.

[0039] Preferably, in step 7, the pure deformation of the unit of the photovoltaic buoy, the soft connection rope, the longitudinal and transverse cable net and the mooring cable is the extension and contraction amount of the unit, and the calculation formula is as follows:

[0040] wherein l time represents the length of the unit at time;

[0041] The pure deformation of the unit of the rigid frame is calculated according to the following formula:

[0042]

[0043] wherein A and B represent two end points of the rigid frame unit respectively, β is the angular deformation amount of the end points of the unit, Δθ is the sum of the rigid body rotation amount and the angular deformation amount of the end points of the unit within a local time step, and γ is the rigid body rotation amount of the unit within a local time step.

[0044] Preferably, in step 2, the mass of the unit is concentrated on the particle, and the calculation formula of the mass of the particle is:

[0045] wherein J is the number of the particle; n is the total number of the units connected with the particle J; is the equivalent mass of the unit assigned to point J; wherein for the particle connected with the rigid frame unit, the mass of the particle also includes its moment of inertia, and the formula is: wherein is the equivalent moment of inertia of the unit assigned to point J. In this scheme, the total mass of the unit is concentrated on the particle, and the unit only plays a connecting role, and the mass of the particle comes from all the units connected therewith.

[0046] Preferably, the step 10 specifically comprises: at the connecting position of different types of components, when there are multiple displacement vector calculation results, the displacement vector of the particles of this type is uniformly taken as the result calculated according to the larger local time step. At the connecting position of different types of components, the particles belong to different types of components, and different local time steps are used for these components, that is, the connecting position particles may have calculation results calculated by stepping according to different local time steps, so that multiple displacement vector calculation results may exist. In the scheme, the displacement vector of the particles of this type is uniformly taken as the result calculated according to the larger local time step.

[0047] Advantages of the scheme:

[0048] 1. For the initial relaxation characteristics specific to the flexible connecting rope, the present application innovatively proposes and establishes a "relaxation rope element" model, which accurately characterizes the relaxation characteristics of the flexible connection, solves the difficulties existing in the traditional method when directly simulating the connecting member with a specific pre-relaxation length, and significantly improves the accuracy of the stress state analysis of the connecting position.

[0049] 2. The present method innovatively integrates rope elements, rod elements, rigid beam elements and self-defined relaxation rope elements, respectively accurately matches the stress characteristics of various types of components, solves the problem that the traditional finite particle method cannot accurately simulate the complex rigid-flexible coupling dynamic characteristics, and leads to difficulties in large-scale full-size analysis.

[0050] 3. An internal force coupling mechanism based on a global time step node is established, multi-scale rigid-flexible coupling analysis is realized, and a reliable method is provided for full-size mechanical analysis of flexible offshore floating photovoltaic structures.

[0051] 4. The critical stability time step of multi-scale structure components varies greatly due to the difference in component properties. The traditional finite particle method uses a globally unified minimum time step to meet the most stringent constraints, resulting in low calculation efficiency, especially in large-scale structures. The present method innovatively calculates the local adaptive time step for each type of component, allowing the same type of component to step according to its own Δt i , and an asynchronous calculation mechanism is constructed. This method effectively avoids the calculation efficiency bottleneck of the globally unified minimum time step, significantly improves the calculation efficiency (especially for large structures containing a large number of low critical step components), and makes it possible to perform large-scale full-size simulation analysis of flexible offshore floating photovoltaic structures. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 The flowchart of the embodiment of the present application is shown.

[0053] Figure 2 The flexible offshore floating photovoltaic structure of the embodiment of the present application is shown.

[0054] Figure 3 A structural schematic diagram of the embodiment of the present application Figure 2 A structural schematic diagram of the embodiment of the present application

[0055] Figure 4 A flexible offshore floating photovoltaic structure diagram of an analysis example of the embodiment of the present application

[0056] Figure 5 A cable net structure central point displacement time history curve diagram of the embodiment of the present application

[0057] Figure 6 A pre-and post-deformation morphology comparison diagram of the structure of the embodiment of the present application

[0058] Figure 7 A longitudinal cable internal force distribution diagram of the cable net structure of the embodiment of the present application

[0059] Figure 8 A transverse cable internal force distribution diagram of the cable net structure of the embodiment of the present application

[0060] Figure 9 A cable net structure tension cloud chart of the embodiment of the present application DETAILED DESCRIPTION

[0061] The following is further described in detail through specific embodiments:

[0062] The reference signs in the drawings of the specification include: photovoltaic buoy 1, cable net structure 2, soft connecting rope 3, rigid outer frame 4, mooring system 5.

[0063] Embodiment:

[0064] A flexible offshore floating photovoltaic structure full-size mechanical analysis method, as shown in Figure 1 , includes the following steps:

[0065] Step 1: Establish a floating photovoltaic geometric model.

[0066] A flexible offshore floating photovoltaic structure, as shown in Figure 2 , is composed of a photovoltaic buoy 1, a cable net structure 2, a soft connecting rope 3 connecting the photovoltaic buoy 1 and the cable net structure 2, a rigid outer frame 4, and a mooring system 5. Among them, the longitudinal and transverse cable net ends are connected to the rigid outer frame 4, the longitudinal and transverse cable nets are arranged in equal intervals, the photovoltaic modules are independent photovoltaic buoys 1 arranged in the cable net grid, the photovoltaic buoy 1 is provided with a photovoltaic assembly, and the four corners are respectively fixed to the cable net nodes through the soft connecting rope 3. The outer frame is anchored through the mooring system 5, forming a huge floating photovoltaic array.

[0067] Among them, as shown in Figure 3 , the photovoltaic buoy 1 and the longitudinal and transverse cable net are connected in a flexible manner, that is, four soft connecting ropes 3 are used to connect the four corner points of the photovoltaic buoy 1 and the four cable net nodes of the corresponding cable net grid.

[0068] Step 2: Multi-scale structure discretization based on force characteristics.

[0069] The flexible floating photovoltaic structure includes members of various scales and characteristics such as rods (buoys), ropes (rope nets, mooring), slack ropes (connecting ropes), beams (outer frames), etc. The traditional finite particle method cannot accurately simulate the complex rigid-flexible coupling dynamic characteristics, resulting in difficulties in large-scale full-size analysis; in this scheme, the flexible offshore floating photovoltaic structure is divided into five types of components: photovoltaic buoys 1, rope net structures 2, soft connecting ropes 3, rigid outer frames 4, and mooring cables 5, and based on the characteristics of these components, different unit structures are used for simulation to perform stress analysis, as follows:

[0070] 1. The distributed array of photovoltaic buoys 1 as the main force component deforms less under the action of wind, waves and currents, and can be regarded as a rigid component, simulated by a rod element.

[0071] 2. The longitudinal and transverse rope nets and mooring cables are force transmission components that can only bear tension and cannot bear pressure, with large displacement and large deformation characteristics under stress, simulated by a rope element.

[0072] 3. In the photovoltaic structure, in order to ensure that the soft connecting rope 3 only transmits the load on the photovoltaic buoy 1 and does not participate in the force transmission of the overall structure, it is usually necessary to lengthen the soft connecting rope 3, so that its initial length is λ times (λ>1) the geometric straight line distance from the corner point of the photovoltaic buoy 1 to the node of the rope net, for example, λ=1.2. Therefore, the soft connecting rope 3 has a slack characteristic.

[0073] For the soft connecting rope 3, the traditional finite particle method lacks an effective unit model to directly simulate its mechanical behavior, and in this scheme, a new type of rope element model, the slack rope element model, is established: the geometric length of the modeling is the geometric straight line length from the corner point of the photovoltaic buoy 1 to the node of the rope net (this length is referred to as the 1 times length); the internal force calculation rule is: set the unstressed length L0 of the slack rope element as the λ times length, and every time the internal force of the element is calculated, first determine the relationship between the length L of the element and the unstressed length L0, if the element length L<L0, the internal force is forced to be 0, indicating that the soft connecting rope 3 is still in a slack state. When L>L0, the internal force is calculated according to the elongation L-L0 of the slack rope element.

[0074] In view of the initial slack characteristic of the flexible connecting rope, the traditional finite particle method lacks an effective unit model to directly simulate its mechanical behavior, and the present invention innovatively proposes and establishes a "slack rope element" model, which accurately characterizes the slack characteristic of the flexible connection, solves the difficulty of directly simulating the connecting member with a specific pre-slack length in the traditional method, and significantly improves the accuracy of the stress state analysis of the connecting part.

[0075] 4. The cable net is connected to the rigid outer frame 4 at both ends. The rigid outer frame 4 needs to be rigid enough to ensure the stability of the cable net grid, and is simulated by beam elements.

[0076] In this step, the structure is discretized into a finite number of particles, which are connected by various elements. The total mass of the elements is concentrated on the particles, and the elements only serve as connectors. The mass of a particle comes from all the elements connected to it. The mass of a particle is calculated as follows:

[0077] (1)

[0078] In the formula, J is the number of particles; n is the total number of elements connected to particle J; is the element assigned to point J. For particles connected to the rigid outer frame 4 element, the moment of inertia is also calculated:

[0079] (2)

[0080] In the formula, is the element assigned to point J.

[0081] Step 3: Assign material properties to each type of component.

[0082] The material properties obtained in this step include Young's modulus, element density, Poisson's ratio, and shear modulus.

[0083] Step 4: Calculate the local adaptive time step for each type of component and the global time step.

[0084] In this step, for each type of component in the aforementioned photovoltaic buoy 1, cable net structure 2, soft connection rope 3, rigid outer frame 4 and mooring cable, based on the length, material density and Young's modulus of the discrete elements, a minimum stable time step shared by all elements in each type of component is determined as the local adaptive step size.

[0085] The property differences of multi-scale structure components result in large differences in critical stable time steps. The traditional finite particle method uses a global unified minimum time step to meet the most stringent constraints, resulting in low computational efficiency, especially in large-scale structures. This method innovatively calculates the local adaptive time step (Δt i ) for each type of component, allowing the same type of component to be calculated according to its own Δt iStep by step, and build asynchronous computer mechanism, effectively avoid the global unified minimum time step of the calculation efficiency bottleneck, significantly improve the computing efficiency, especially for the large structure containing a large number of low critical step components, make flexible offshore floating photovoltaic structure engineering practical large-scale full size simulation analysis possible.

[0086] Where, each type of component of local adaptive step length must meet the following conditions:

[0087] (3)

[0088] In the formula, ρ i is the density of the material of the i type component, E i is the Young's modulus of the material, and l i is the unit length.

[0089] According to the local adaptive time step Δt i of each type of component, the global time step ΔT is calculated, and the ratio of the global time step ΔT to each local time step Δt i is calculated.

[0090] Step 5: Apply boundary conditions and loads.

[0091] In this step, the seabed anchor point of the mooring cable is set as the displacement boundary constraint point, the wind wave flow load is applied to the structure, and the load is equivalent distributed to the related particles.

[0092] Step 6: Local parallel time step calculation.

[0093] For each particle in each component type i, the central difference method is used to calculate the particle displacement vector with its local time step as the time increment.

[0094] (4)

[0095] In the formula, represents the displacement vector of particle J at time+Δt i , F J is the resultant force vector of particle J, which is calculated by the following formula:

[0096] (5)

[0097] In the formula, P J is the external force vector of particle J, is the internal force vector of element a connected to particle J, and the internal force acting on the particle needs to be negative.

[0098] ​C1, C2 are damping related calculation coefficients, calculated by the following formula:

[0099] (6)

[0100] In the formula, ζ is the damping factor.

[0101] For the particles connected with the rigid outer frame 4 unit, the angular displacement of the particle also needs to be calculated:

[0102] (7)

[0103] In the formula, denotes the angular displacement of particle J at time+Δt i , M J is the resultant moment on particle J.

[0104] (8)

[0105] In the formula, Q J is the external bending moment on particle J, is the internal bending moment of unit a connected with particle J.

[0106] Step 7: Integration of internal and external forces of particles.

[0107] In this step, the internal and external forces of the particles of each component are integrated. This step divides the internal force calculation into two parts: unit pure deformation calculation and unit internal force solution. The concept of reverse motion is introduced. Through virtual reverse motion, the unit form at the end of each iteration time step is reversely rigidly translated or rotated to the initial time step of each iteration time step, thereby decoupling the unit displacement and deformation. By comparing the unit forms at the initial time and the end time, the pure deformation of the unit in each iteration time step is obtained.

[0108] Among them, the unit pure deformation of photovoltaic buoy 1, soft connection rope 3, longitudinal and transverse cable net and mooring cable is the stretching amount of the unit:

[0109] (9)

[0110] In the formula, l time denotes the length of the unit at time.

[0111] And for the unit pure deformation of the rigid outer frame 4, it is calculated as follows:

[0112] (10)

[0113] In the formula, A and B represent two end points of the rigid frame 4 unit respectively, β is the rotation deformation amount of the unit end point, Δθ is the sum of the rigid rotation amount and the rotation deformation amount of the unit end point in a local time step, and γ is the rigid rotation amount of the unit in a local time step. The calculation formulae of Δθ and γ are as follows:

[0114] (11)

[0115] (12)

[0116] wherein, is the unit direction vector of the rigid frame 4 unit at time.

[0117] The unit internal force increment is calculated based on the pure deformation and material constitutive relation of the unit, and then superimposed with the initial internal force of the unit to obtain the unit internal force.

[0118] (13)

[0119] In the formula, K is the stiffness matrix of the unit, and the calculation method is the same as that of the traditional finite element method; and Δ is the pure deformation amount of the unit.

[0120] For the rigid frame 4 unit, the bending moment internal force of the unit also needs to be calculated:

[0121] (14)

[0122] represents the internal force vector of the unit at time, represents the bending moment of the unit at time.

[0123] The internal force and external force of all units are accumulated to the particle to obtain the force condition of each particle. The resultant force of the particle is:

[0124] (15)

[0125] For the particle connected with the rigid frame 4 unit, the resultant moment of the particle also needs to be calculated:

[0126] (16)

[0127] In the scheme, the internal force of the unit from other types of components received by the particle at the connection of different types of components in the asynchronous calculation of different types of components has a time lag. When the local time step of the particle in the i-type component (including the particle at the connection with other types of components) is calculated in a global time step, the internal force of the unit of other types of components received by the particle at the connection is directly used in the calculation process k is an integer and time represents the time node that the particle is currently in. The particles at the connection are subjected to different internal forces in different units, and in a global time step, the internal forces in different units are not uniform in the time node because the particles in different units use different local time steps. Therefore, the internal forces calculated using the synchronized time node are used.

[0128] Step 8: For all component types i, repeat steps 6-7 respectively times .

[0129] Step 9: Step 6 is performed again, at this time all particles are synchronized in global time.

[0130] In this step, all particles of all components (i.e. all particles) have completed n i iteration calculations, i.e. they have all gone through n i *Δt i =ΔT time, so they are synchronized in time.

[0131] Step 10: Coordination of the positions of particles at the connections of different components.

[0132] Particles at the connections of different types of components belong to units of different types of components, and these units use different local time steps. Therefore, the particles at the connections may have results calculated by stepping in different local time steps, which may result in multiple displacement vector calculation results. When multiple displacement vector calculation results appear, the displacement vector of this type of particle is uniformly taken as the result calculated by the larger local time step.

[0133] Step 11: Integration of internal and external forces of particles.

[0134] This step is used to integrate the sum of the internal force vectors of the particle and the external forces acting on the particle from all units of different component types connected to the particle. The integration of internal forces in this step is different from that in step 7.

[0135] In this step, the internal forces of each unit are first solved, and the solving process is consistent with the internal force solving method in step 7. Then, the internal forces of all units are accumulated to the particle, and the external load is updated. The force of the external load acting on the particle is superimposed to obtain the final force of the particle. This scheme integrates the internal forces acting on the particles at the connections of different types of components, i.e. the sum of the internal force vectors of the particle from all units of different component types connected to the particle, and realizes the multi-scale coupling of the structure.

[0136] Step 12: Determine whether to terminate iteration.

[0137] The iteration termination condition in this step is as follows: the difference between the Z coordinates of the center point of the cable net structure 2 in two adjacent global time steps ΔT is less than 10 -4 m. If not, repeat steps 6-11. If yes, terminate the iteration.

[0138] Step 13: The calculation is completed, and the final position of all particles constitutes the geometric configuration of the structure in the steady state.

[0139] In this scheme, the explicit algorithm is used to solve the mechanical equilibrium equation in the structure analysis method, so there is a result output for each iteration process. The calculation results of each global iteration step are recorded, and the time history curve is drawn to visually monitor the structure dynamic response process. The position information of all particles before and after deformation of the structure can be extracted, and the initial configuration and final steady state configuration of the structure can be drawn to intuitively describe the morphological changes of the structure. The internal force data of each type of component of the structure at steady state or a specified time can be extracted, and the internal force distribution diagram of the structure can be drawn; all the internal forces are sorted and high internal force elements are selected, and the specified elements are highlighted in the overall morphological diagram of the structure, so that it can be clearly and intuitively seen which parts are force concentrated, facilitating subsequent local component strengthening and structure optimization.

[0140] The following is a detailed example of using the above analysis

[0141] The structural morphology of the structural scheme is shown in Figure 4 The structure is composed of photovoltaic floating boxes 1, soft connecting ropes 3, longitudinal and transverse cable nets, rigid peripheral floating buoys, and mooring cables, which meets the characteristics of multi-component rigid-flexible coupling and strong nonlinearity of mechanical behavior. The AQWA software is used to calculate the load on the structure, and the above-mentioned structure analysis method is used to simulate the mechanical behavior of the structure.

[0142] The displacement time history curve of the center point of the cable net structure 2 is shown in Figure 5 As can be seen from the figure, the proposed structure analysis method converges for the simulation results of the complex mechanical behavior of the flexible offshore floating photovoltaic.

[0143] The comparison of the deformation before and after the deformation of the structure is shown in Fig. 6. As can be seen from the figure, the proposed structure analysis method can effectively simulate the complex mechanical behavior of the flexible offshore floating photovoltaic structure, and the calculation results converge.

[0144] The internal force distribution diagram of the longitudinal and transverse cables of the cable net structure 2 is shown in Figure 7 and Figure 8 As shown in Figure 9 , the tension cloud diagram of all elements of the longitudinal and transverse cable net is drawn, and the force state is distinguished according to the color, so that the most concentrated place of the structure can be seen. Designers can optimize the internal force distribution and strengthen the local components based on this.

[0145] The application innovatively proposes and establishes a "relaxed tendon unit" model, accurately characterizes the relaxed characteristics of flexible connections, solves the difficulties of traditional methods in directly simulating the connectors with specific pre-relaxation length, and significantly improves the accuracy of stress state analysis of the connection parts. The method innovatively integrates tendon unit, rod unit, rigid beam unit and self-defined relaxed tendon unit, and accurately matches the stress characteristics of various components respectively. A global time step node-based internal force coupling mechanism is established, realizing multi-scale rigid-flexible coupling analysis, and providing a reliable method for full-size mechanical analysis of flexible offshore floating photovoltaic structure. The method innovatively calculates the local adaptive time step length for each component type, allows the same type of components to step according to their respective Δt i , and builds an asynchronous computing mechanism; the method effectively avoids the calculation efficiency bottleneck of global unified minimum time step length, significantly improves the calculation efficiency, and makes large-scale full-size simulation analysis of flexible offshore floating photovoltaic structure engineering practical possible.

[0146] The above-mentioned is only the embodiment of the application, and the specific technical solutions and / or common knowledge of characteristics in the scheme are not described in detail. It should be pointed out that for those skilled in the art, without departing from the technical scheme of the application, a number of modifications and improvements can be made, in the application, unless otherwise specified and limited, the terms "installation", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium; it can be the communication between two elements. For those skilled in the art, the specific meaning of the above-mentioned terms in the application can be understood according to the specific circumstances. The protection scope claimed in the application should be subject to the content of its claims, and the specific implementation mode and the like in the specification can be used to explain the content of the claims.

Claims

1. A method for full-scale mechanical analysis of a flexible offshore floating photovoltaic structure, characterized in that, The method comprises the following steps: Step 1: establishing a floating photovoltaic geometric model; Step 2: performing scale structure discretization based on force characteristics to form particles and units connected by the particles; a rod unit is used to simulate the photovoltaic floating box, a string unit is used to simulate the longitudinal and transverse cable net and the mooring cable, a slack string unit model is used to simulate the soft connecting rope, and a beam unit is used to simulate the rigid outer frame; the geometric length of the slack string unit model is the geometric straight line length between the corner point of the photovoltaic floating box and the node of the cable net; Step 3: assigning material properties to each type of component; Step 4: calculating the local adaptive time step of each type of component and the global time step; Step 5: applying boundary conditions and loads, and equivalently distributing the loads to the related particles; Step 6: calculating the displacement vector of each particle in each component type i; Step 7: calculating and integrating the internal force and external force of the particles of each component; Step 8: For all component types i, repeat each of Substeps 6-7; Step 9: performing step 6 again, at this time all particles are synchronized in the global time; Step 10: coordinating the positions of the particles at the connection of different components; Step 11: calculating and integrating the internal force and external force of the particles of each component, and the internal force of the particles at the connection is the sum of the internal force vectors of the units of different component types acting on the particles; Step 12: judging whether the difference between the Z coordinates of the center points of the cable net structure in two adjacent global time steps ΔT is less than a preset value, if the stop iteration condition is not met, repeating the above steps 5-11 until the stop iteration condition is met, and the geometric configuration of the structure under the action of the steady state is completed; The calculation method of the internal force of the slack string unit model is: the unstressed length L0 of the slack string unit is set as λ times the length, and each time the internal force of the unit is calculated, the relationship between the length L of the unit and the length L0 is determined first, if L < L0, the internal force is forced to be 0, indicating that the soft connecting rope is still in a relaxed state at this time; when L > L0, the internal force is calculated according to the elongation L-L0 of the slack string unit; The step 4 specifically comprises: for each type of component, determining a minimum stable time step shared by all units in the type of component based on the length, material density and Young's modulus of the discrete units in the type of component as a respective local adaptive time step; calculating a global time step ΔT according to the local adaptive time steps Δt of the types of components; and calculating a ratio of the global time step ΔT to the local adaptive time steps Δt. i i .​​​​ 2. The method according to claim 1, wherein: The local adaptive step of each type of component in step 4 needs to meet the following conditions: In the formula, ρ i For component type i, E is the material density. i For the Young's modulus of the material, l i The unit length is denoted as .

3. The method according to claim 1, wherein: Step 6 specifically comprises: Step 61 : For each particle within each component type i, the central difference method is employed to its local time step The particle displacement vector is calculated with an explicit step for the time increment, as follows: wherein represents the displacement vector of particle J at time + Δt i F J is the resultant force vector experienced by particle J, C1, C2 are calculation coefficients related to the damping, is the equivalent mass assigned to point J; Step 62: for the particles connected with the rigid outer frame unit, further calculate the angular displacement of the particles, and the formula is as follows: wherein denotes the angular displacement of particle J at time + Δt i M J is the resultant moment on particle J, is the unit equivalent moment of inertia assigned to point J.

4. The method according to claim 3, wherein: Step 7 comprises: Step 71: Calculate the internal force increment of the unit based on the pure deformation of the unit and the material constitutive relation, and then superimpose it with the initial internal force of the unit to obtain the internal force of the unit, and the specific formula is: , wherein K is the stiffness matrix of the unit, and Δ is the pure deformation of the unit; wherein the internal force of the rigid outer frame unit also includes the bending moment internal force of the unit, and the formula is as follows: , wherein represents the internal force vector of the unit at time time, represents the bending moment of the unit at time time. Step 72: accumulate the internal force and external force of all units to the particles, and the resultant force acting on the particles is: where P is the vector of external forces acting on the particle J, J is the vector of internal forces of the element a connected to the particle J, is the vector of internal forces of the element a connected to the particle J, Wherein, the resultant force of the rigid outer frame unit also includes the resultant moment thereof, and the specific formula is: where Q J is the external bending moment on particle J, is the internal bending moment of the cell α to which particle J is connected.

5. The method according to claim 4, wherein: The step 7 directly adopts the cell internal force of other type component suffered by the particle at the joint calculated by the last integral multiple global time step node calculation for the cell internal force of the particle in the i type component when its local time step is carried out within a global time step , k is an integer and , time represents the time node at which the particle is currently located.

6. The method of claim 3, wherein the method is a full-scale mechanical analysis method for a flexible offshore floating photovoltaic structure. The unit pure deformation of the photovoltaic floating box, the soft connecting rope, the longitudinal and transverse cable net and the mooring cable in step 7 is the elongation of the unit, and the calculation formula is as follows: wherein l time denotes the length of the unit at time The unit pure deformation of the rigid outer frame is calculated according to the following formula: In the formula, A and B represent two end points of the rigid outer frame unit respectively, β is the angular deformation of the unit end point, Δθ is the sum of the rigid body rotation and the angular deformation of the unit end point in one local time step, and γ is the rigid body rotation of the unit in one local time step.

7. The method of claim 1, wherein: In step 2, the mass of the unit is concentrated on the particles, and the calculation formula of the particle mass is: where J is the index of the particle; n is the total number of units connected to particle J; is the unit equivalent mass assigned to point J; where for particles connected to rigid frame units, the particle mass also includes its rotational inertia, given by: where is the unit equivalent rotational inertia assigned to point J.

8. The method of claim 1, wherein: Step 10 specifically comprises: for the particles at the connection of different types of components, when there are multiple displacement vector calculation results, the displacement vector of the particles is uniformly taken as the result calculated according to the larger local time step.

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