A calculation method for the optimal pre-tension of a flexible photovoltaic support cable structure

Abstract

The present invention discloses a method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure, which belongs to the field of solar energy application technology. The method analyzes the pre-tension of the cable body of the entire flexible photovoltaic support system as a design object, and takes the minimum sum of the horizontal pre-tension of the load-bearing cable and the stabilizing cable as the optimization target under the premise of meeting the deformation strength design requirements of each load condition. The method is applicable to the determination of the pre-tension of the cable body of a single-layer cable and a double-layer cable flexible photovoltaic support structure system. The present invention has the advantages of improving the efficiency and accuracy of the pre-tension value of the cable body of the flexible photovoltaic support structure. Under the premise of meeting the design requirements such as deformation and strength, the horizontal pre-tension of the cable body is optimized to reduce the overall force of the cable body diameter specification and its end support, thereby reducing the cost of the cable body and its foundation and the difficulty of construction tensioning.

Description

Technical Field

[0001] The invention belongs to the technical field of solar energy application, and in particular relates to a method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure. Background Art

[0002] As a new type of photovoltaic support, the flexible support has the advantages of large span and high clearance due to its system structure characteristics, thereby increasing the land utilization space and promoting the compound utilization of land such as "fish-photovoltaic complementarity" and "agriculture-photovoltaic complementarity", and has broad application prospects.

[0003] In order to ensure the wind-resistant stiffness of the entire structural system, the flexible photovoltaic support structure often needs to apply a certain pre-tension to its cable structure system. If the pre-tension is too small, the deformation under the design condition will not meet the requirements, and the wind resistance of the structural system will be weakened; if the pre-tension is too large, the cable force of the cable structure under the limit state will exceed the allowable value of its breaking force, the force under the limit condition of the end support will increase, and the foundation cost of the relevant end support will increase. However, the current design specifications do not have a calculation method for the pre-tension value of the cable body of the flexible photovoltaic support structure. The value of the pre-tension of each cable body during the structural design process is subjective. Although it meets the design requirements, the force of the end support is not optimal (the sum of the horizontal pre-tension of the load-bearing cable and the stabilizing cable is the smallest). Therefore, how to accurately and efficiently design the pre-tension value of the flexible support cable body and further reduce the cost of the current flexible photovoltaic support end support is a key engineering and technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the above-mentioned engineering difficulties, the present invention proposes a method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure. This method has the advantages of improving the efficiency and accuracy of the pre-tension value of the cable body of the flexible photovoltaic support structure. On the premise of meeting the design requirements such as deformation, the overall force of the end support is reduced by optimizing the value of the horizontal pre-tension of the cable body, thereby reducing the cost of the end support foundation.

[0005] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

[0006] A method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure, characterized in that it comprises the following steps:

[0007] Step 1: Input the flexible photovoltaic support structure system parameters and set the initial boundary conditions of the entire flexible photovoltaic support structure system;

[0008] Step 2: Establish a finite element model of the entire structural system based on the structural parameters input in step 1;

[0009] Step 3: Input the initial pretension T0 of the cable body;

[0010] Step 4: Input the external loads on the entire flexible support structure system;

[0011] Step 5: Use the constructed finite element model to calculate the maximum deformation of the cable structure system under self-weight and normal service limit conditions Calculate the maximum cable force on the cable body under the bearing capacity limit condition

[0012] Step 6: Input the deformation control allowable value Δ1 under the self-weight condition of the flexible photovoltaic bracket and the deformation control allowable value Δ2 under the normal use limit condition; the maximum allowable cable force of each cable body is in is the breaking force coefficient, F max is the breaking force corresponding to the cable body;

[0013] Step 7: Check whether the deformation meets the design requirements and whether the sum of the horizontal pretension of the load-bearing cables and the stabilizing cables is the minimum; if both requirements cannot be met, jump to step 3 to adjust the pretension of each cable body, and repeat this cycle until the deformation meets the design requirements and the sum of the horizontal pretension of the load-bearing cables and the stabilizing cables reaches the minimum;

[0014] Step 8: Check whether the maximum cable force meets the design requirements and whether the diameter specifications of each cable body are the smallest; if they cannot meet the requirements at the same time, jump to step 2 to adjust the cable body specifications in the finite element model, and repeat this cycle until the maximum cable force meets the design requirements and the diameter specifications of each cable body are the smallest, and then output the cable body pretension design value and diameter specification.

[0015] Preferably, in step 1, the initial boundary conditions include component size parameters, component installation inclination angles, cable body specifications, and steel beam and column sizes.

[0016] Preferably, in step 3, when the entire flexible support structure system is a single-layer cable structure, if the end support adopts an inclined steel rod, in is the initial pretension of the component load-bearing cable. If the end support adopts a cable, in is the initial pretension of the end support cable, which can be calculated based on the principle of force balance. Calculation is performed, where α is the angle between the inclined cable and the horizontal plane; when the entire flexible support structure system is a double-layer cable structure, if the end support adopts an inclined steel rod, in is the initial pretension of the lower stabilizing cable. If the end support adopts a cable, According to the principle of force balance, Calculation is performed, where β is the angle between the lower stabilizing cable at the end support and the load-bearing cable.

[0017] Preferably, in step 3, the initial pretension of the cable body can be The angle α between the inclined cable and the horizontal plane is within the range of [30°, 60°], and the angle β between the lower stabilizing cable at the end support and the load-bearing cable is within the range of [0°, 20°].

[0018] Preferably, in step 4, the input external loads include wind load, snow load and temperature load, all of which are taken as loads with a return period of 25 years, and the influence of load combination conditions is taken into consideration.

[0019] Preferably, in step 6, the maximum allowable deformation value Δ1 of the flexible support structure system under deadweight conditions can be taken within the range of [L / 200, L / 100]; the maximum allowable deformation value Δ2 of the flexible support structure system under normal use limit conditions can be taken within the range of [L / 100, L / 50], where L is the span of the flexible photovoltaic support system; the breaking force coefficient of the cable body is The value can be taken within the range of [0.5,0.6]. The breaking force corresponding to the cable body can be taken according to the specifications of the cable body and the corresponding standards, and the strength is 1860MPa.

[0020] Preferably, in step 7, the optimization model takes the sum of the horizontal pretension of the load-bearing cable and the stabilizing cable as the minimum as the optimization target, and the initial pretension of the component load-bearing cable is and the initial pretension of the lower stabilizing cable During the adjustment process, the initial pretension of the cable Adjustments are made synchronously based on the principle of force balance on the end supports.

[0021] Preferably, the specific optimization model is:

[0022] Constraint function:

[0023] Optimization equation: min(t c +t w ·cosβ)

[0024] Parameter variables:

[0025] In the formula, Δt c is the adjustment amount of the pre-tension of the component load-bearing cable, Δt w In order to stabilize the adjustment amount of cable pre-tension, the cable body pre-tension is adjusted by 0.1 kN each time.

[0026] Preferably, the pre-tension values ​​of the same type of cable bodies are equal.

[0027] Preferably, commonly used cable diameter specifications for flexible photovoltaic brackets are 12.7, 15.2, 15.7, 17.8, and 21.6, in mm.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] This method takes the minimum sum of the horizontal pre-tension of each cable (load-bearing cable and stabilizing cable) as the optimization target, and is applicable to the determination of the pre-tension of the cable body of a single-layer cable and double-layer cable flexible photovoltaic support structure system. The present invention has the advantages of improving the efficiency and accuracy of the pre-tension value of the cable body of the flexible photovoltaic support structure. Under the premise of meeting the design requirements such as deformation and strength, the horizontal pre-tension of the cable body is optimized to reduce the overall force of the cable body diameter specification and its end support, thereby reducing the cost of the cable body and its foundation and the difficulty of construction tensioning. The above beneficial effect statement shows that this scheme has good engineering practical prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a three-dimensional schematic diagram of the flexible photovoltaic support structure system;

[0031] Figure 2 It is a side schematic diagram of the flexible photovoltaic support structure system;

[0032] Figure 3 It is the finite element model of the flexible photovoltaic support structure system;

[0033] Figure 4 It is a specific flow chart of the pre-tension optimization model of the cable structure of the flexible photovoltaic support system;

[0034] In the figure: 1. Photovoltaic module; 2. Module load-bearing cable; 3. Stabilizing cable; 4. Rigid support rod; 5. Column; 6. Load-bearing steel beam; 7. Inclined cable. DETAILED DESCRIPTION

[0035] The specific implementation of the present invention is described below in conjunction with the accompanying drawings to facilitate the understanding of the present invention by those skilled in the art. Obviously, the present invention is not limited to the scope of the specific implementation. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are non-creative work, and all inventions and creations using the invention concept of this law are protected.

[0036] Example:

[0037] The span of a photovoltaic flexible support project is 35m, the lowest point of the photovoltaic module is 7m above the mud surface, the load-bearing cable of the module adopts a 17.8mm diameter prestressed concrete steel strand, the stabilizing cable adopts a 15.2mm diameter prestressed concrete steel strand, and the inclined cable adopts a 21.6mm diameter prestressed concrete steel strand. The standard strength of the steel strand used is 1860MPa; the bearing steel beams are all made of H-shaped steel, the columns are made of PHC400 prestressed concrete pipe piles, and the number of pile foundations in a square array and a single row is 5. The optimization model of the prestressing force of the cable structure proposed in the present invention is used to design the prestressing force of the cable body. The specific process (such as Figure 4 shown) is:

[0038] Step 1: Input the parameters of the flexible photovoltaic support structure system, set the initial boundary conditions of the entire flexible photovoltaic support structure system, the component size parameters are 2384×1096×35mm, the component installation angle is 15°, and the distance between the front and rear rows of components is 1.71m;

[0039] Step 2: Based on the structural parameters input in step 1, a finite element model of the entire flexible support structure system is established (e.g. Figure 3 shown);

[0040] Step 3: The flexible support of this project adopts a double-layer cable structure with the end support as a cable. The angle α between the cable and the horizontal plane is 45°, and the angle β between the lower stabilizing cable at the end support and the component bearing cable is 10°. The initial pretension of the component bearing cable is Initial pretension of the lower stabilizing cable The initial pretension of the cable is based on the principle of force balance.

[0041] Step 4: Input the external loads on the entire flexible support structure system, where the basic wind pressure once in 25 years is 0.33kN / m 2 The basic snow pressure once in 25 years is 0.47kN / m 2 , the maximum temperature difference load is 20℃.

[0042] Step 5: Use the constructed finite element model to calculate the maximum deformation of the cable structure system under the self-weight condition The maximum deformation under normal use limit conditions is Under the bearing capacity limit condition, the maximum cable force on the inclined cable is 269.4kN, the maximum cable force on the component load-bearing cable is 122.5kN, and the maximum cable force on the lower stabilizing cable is 92.5kN.

[0043] Step 6: Input the allowable value of deformation control under the self-weight condition of the flexible photovoltaic bracket Allowable value of deformation control under normal use limit conditions The maximum allowable cable force of each cable body is in Taking 0.6, the maximum allowable cable force of the inclined cable is calculated to be 318kN, the maximum allowable cable force of the component load-bearing cable is 213kN, and the maximum allowable cable force of the lower stabilizing cable is 156kN.

[0044] Step 7: After reviewing steps 5 and 6, the deformation under self-weight and normal use limit conditions meet the design requirements, but the sum of the horizontal pretension of the load-bearing cables and stabilizing cables is 122kN, which has not yet reached the minimum. Jump to step 3 to adjust the pretension of each cable body, and repeat this cycle until the deformation meets the design requirements and the sum of the horizontal pretension of the load-bearing cables and stabilizing cables reaches the minimum.

[0045] Step 8: After reviewing steps 5 and 6, the maximum cable force of the cable body under the bearing capacity limit condition meets the design requirements, but the diameter of the stabilizing cable of 15.2 mm has not yet reached the minimum. Jump to step 2 to adjust the diameter of the stabilizing cable to 12.7 mm, and repeat this cycle until the maximum cable force meets the design requirements and the diameter of each cable body is the minimum.

[0046] The specific optimization model is:

[0047] Constraint function:

[0048] Optimization equation: min(t c +t w ·cosβ)

[0049] Parameter variables:

[0050] In the formula, Δt c is the adjustment amount of the pre-tension of the component load-bearing cable, Δt w In order to stabilize the adjustment amount of cable pre-tension, each iterative adjustment amount is based on 0.1 kN.

[0051] After several iterations of optimization, the final design pretension of the output component load-bearing cable is 82.8kN, the design pretension of the lower stabilizing cable is 31.9kN, and the design pretension of the inclined cable is 161.8kN; the diameter of the component load-bearing cable is 17.8mm, the diameter of the lower stabilizing cable is 12.7mm, and the diameter of the inclined cable is 21.6mm.

[0052] The above shows and describes the basic principles and main structural features of the present invention. The present invention is not limited to the above examples. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure, characterized in that: The steps include: Step 1: Input the flexible photovoltaic support structure system parameters and set the initial boundary conditions of the entire flexible photovoltaic support structure system; Step 2: Establish a finite element model of the entire structural system based on the structural parameters input in step 1; Step 3: Input the initial pretension T0 of the cable body; Step 4: Input the external loads on the entire flexible support structure system; Step 5: Use the constructed finite element model to calculate the maximum deformation of the cable structure system under self-weight and normal service limit conditions Calculate the maximum cable force on the cable body under the bearing capacity limit condition Step 6: Input the deformation control allowable value Δ1 under the self-weight condition of the flexible photovoltaic bracket and the deformation control allowable value Δ2 under the normal use limit condition; the maximum allowable cable force of each cable body is in is the breaking force coefficient, F max is the breaking force corresponding to the cable body; Step 7: Check whether the deformation meets the design requirements and whether the sum of the horizontal pretension of the load-bearing cables and the stabilizing cables is the minimum; if both requirements cannot be met, jump to step 3 to adjust the pretension of each cable body, and repeat this cycle until the deformation meets the design requirements and the sum of the horizontal pretension of the load-bearing cables and the stabilizing cables reaches the minimum; Step 8: Check whether the maximum cable force meets the design requirements and whether the diameter specifications of each cable body are the smallest; if they cannot meet the requirements at the same time, jump to step 2 to adjust the cable body specifications in the finite element model, and repeat this cycle until the maximum cable force meets the design requirements and the diameter specifications of each cable body are the smallest, and then output the cable body pretension design value and diameter specification.

2. According to claim 1, a method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure is characterized by: In step 1, the initial boundary conditions include component size parameters, component installation inclination angles, cable body specifications, and steel beam and column sizes.

3. The method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure according to claim 1, characterized in that: In step 3, when the entire flexible support structure system is a single-layer cable structure, if the end support adopts an inclined steel rod, in is the initial pretension of the component load-bearing cable. If the end support adopts a cable, in is the initial pretension of the end support cable, according to the force balance principle Calculation is performed, where α is the angle between the inclined cable and the horizontal plane; when the entire flexible support structure system is a double-layer cable structure, if the end support adopts an inclined steel rod, in is the initial pretension of the lower stabilizing cable. If the end support adopts a cable, According to the principle of force balance Calculation is performed, where β is the angle between the lower stabilizing cable at the end support and the load-bearing cable.

4. The method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure according to claim 3, characterized in that: In step 3, the initial pretension of the cable body is The angle α between the inclined cable and the horizontal plane is within the range of [30°, 60°], and the angle β between the lower stabilizing cable at the end support and the load-bearing cable is within the range of [0°, 20°].

5. The method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure according to claim 1, characterized in that: In step 4, the external loads input include wind load, snow load and temperature load, all of which are taken as loads with a return period of 25 years and the influence of load combination conditions is taken into account.

6. The method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure according to claim 1, characterized in that: In step 6, the maximum allowable deformation value Δ1 of the flexible support structure system under the deadweight condition is within the range of [L / 200, L / 100]; the maximum allowable deformation value Δ2 of the flexible support structure system under the normal use limit state is within the range of [L / 100, L / 50], where L is the span of the flexible photovoltaic support system; the breaking force coefficient of the cable body is The value is within the range of [0.5,0.6]. The breaking force corresponding to the cable body is determined according to the specifications of the cable body and the corresponding standards, and the strength is 1860MPa.

7. The method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure according to claim 1, characterized in that: In step 7, the optimization model takes the sum of the horizontal pretension of the load-bearing cables and the stabilizing cables as the minimum as the optimization target, and the initial pretension of the component load-bearing cables is and the initial pretension of the lower stabilizing cable During the adjustment process, the initial pretension of the cable Adjustments are made synchronously based on the principle of force balance on the end supports.

8. The method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure according to claim 3, characterized in that: The specific optimization model is: Optimization equation: min(t c +t w ·cosβ) Parameter variables: In the formula, Δt c is the adjustment amount of the pre-tension of the component load-bearing cable, Δt w In order to stabilize the adjustment amount of cable pre-tension, the cable body pre-tension is adjusted with 0.1 kN as the benchmark for each iteration.

9. The method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure according to claim 1, characterized in that: The pre-tension values ​​of cables of the same type are equal.

10. The method for calculating the optimal pre-tension of a flexible photovoltaic support cable structure according to claim 1, characterized in that: The commonly used cable diameter specifications for flexible photovoltaic brackets are 12.7, 15.2, 15.7, 17.8, and 21.6, in mm.

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