A connecting cable applied to photovoltaic module in vacuum environment

Abstract

This invention relates to the field of photovoltaic cable technology, and in particular to a connecting cable for photovoltaic modules used in a vacuum environment. The cable comprises a composite conductor, a gradient functional insulation layer sequentially wrapped around the outside of the composite conductor, a sandwich-structured shielding anti-ionic oxygen layer, and a termination self-locking buffer module connected to the cable end. The cable has a flat, flexible, and standardized structure. The composite conductor of this invention employs a core-sheath structure of nanocrystalline copper and silver-magnesium-nickel alloy, combined with a BN protective layer, ensuring that the resistivity increase after 1 MeV electron radiation is ≤4%, and the gamma ray resistance is 1×10⁻⁶. 6 After Gy, the transmission loss is reduced by ≥60%, solving the problem of the surge in loss after radiation of existing conductors.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cable technology, and in particular to a connecting cable for photovoltaic modules used in a vacuum environment. Background Technology

[0002] Space photovoltaic (PV) modules are core energy devices for spacecraft and space power stations, and their connecting cables need to operate long-term in the extreme environments of low Earth orbit to geostationary orbit. Current ground-based PV cables mostly use irradiated cross-linked polyolefin insulation and oxygen-free copper conductors. While these meet conventional weather resistance and voltage withstand requirements, they struggle to cope with the multiple coupling challenges of atomic oxygen corrosion, high-energy radiation, extreme thermal cycling, and repeated mechanical expansion and contraction in a vacuum environment. In LEO environments, the atomic oxygen flux reaches as high as 10... 15 atoms / cm 2 •s will rapidly oxidize the polymer sheath and copper conductor; high-energy protons, electrons and gamma rays radiation will degrade the insulation material and increase the resistivity of the conductor; the huge temperature difference cycle of -196℃ to +200℃ can easily lead to interlayer peeling and thermal fatigue embrittlement; the repeated deployment and retraction of the solar panels also puts forward stringent requirements on the flexibility and storage reliability of the cable.

[0003] While existing aerospace cables utilize polyimide or ethylene-tetrafluoroethylene copolymer insulation and silver-plated copper conductors, which improves temperature and radiation resistance to some extent, the conductor's radiation resistance remains insufficient, with resistivity increasing by more than 10% after high-energy radiation. Atomic oxygen protective coatings are mostly single SiO2 or PI composite layers, with limited adhesion and bending resistance, and are prone to peeling after long-term exposure. Existing patents for photovoltaic cables primarily focus on weather resistance and tensile strength in terrestrial environments. The design of aerospace cables does not deeply integrate with the exposure characteristics of photovoltaic modules and the requirements of high-voltage DC transmission, lacking an integrated lightweight solution that simultaneously addresses radiation protection, atomic oxygen protection, thermal cycling stability, and low-vacuum venting. Summary of the Invention

[0004] The technical problem to be solved by this invention is the failure of existing cables under atomic oxygen corrosion, high-energy radiation, extreme thermal cycling and repeated extension and retraction.

[0005] The technical solution adopted by this invention to solve its technical problem is: a connecting cable for photovoltaic modules in a vacuum environment, comprising a composite conductor, a gradient functional insulation layer sequentially covering the outside of the composite conductor, a sandwich-structured shielding antigen oxygen layer, and a termination self-locking buffer module connected to the end of the cable; the cable as a whole has a flat, flexible, and shaped structure. The composite conductor is a nanocrystalline copper-silver-magnesium-nickel composite stranded conductor, consisting of a central core wire and an outer stranded wire. The central core wire is an Ag-0.2Mg-0.15Ni alloy wire, and the outer stranded wire is a nanocrystalline copper wire. The surface of the nanocrystalline copper wire is plated with a 2μm thick boron nitride protective layer. The section diameter ratio of the composite conductor is 14~16, and the diameter of a single wire is 0.05~0.08mm. After stranding, it is pressed and shaped into a flat shape by a rectangular polycrystalline mold. The gradient functional insulation layer has a three-layer co-extruded structure, consisting of an inner insulation layer, an intermediate buffer layer, and an outer insulation layer from the inside out. The inner insulation layer is irradiated cross-linked XETFE with a thickness of 0.03~0.05 mm. The intermediate buffer layer is a polyimide / nano-alumina gradient composite material, with the nano-alumina content gradually increasing from 10 wt% to 30 wt% from the inside out, and a thickness of 0.02~0.04 mm. The outer insulation layer is fluoropolymer rubber with a thickness of 0.02~0.03 mm. The sandwich structure shielding antigen oxygen layer includes an inner silver-plated copper flat wire braided shielding layer, a middle PI / SiO2 composite substrate layer, and an outer diamond-like carbon antigen oxygen coating layer. The termination self-locking buffer module includes an elastic buffer section, a self-locking positioning mechanism, and aerospace-grade waterproof and dustproof terminals.

[0006] The nanocrystalline copper wire has a grain size ≤100nm, is prepared by a severe plastic deformation process, and has a resistivity increase of ≤4% after 1MeV electron radiation.

[0007] The three-layer structure of the gradient functional insulation layer is formed by synchronous co-extrusion, with an interlayer bonding strength ≥15MPa and a volume resistivity ≥1×10⁻⁶. 15 Ω·m.

[0008] The braided shielding layer has a braiding density of ≥95%, a flat wire thickness of 0.02 mm, and a width of 0.15 mm; the PI / SiO2 composite substrate layer has a SiO2 content of 25 wt% and a thickness of 0.03 mm; the diamond-like carbon coating has a thickness of 1~1.5 μm and is deposited by PECVD process.

[0009] The elastic buffer section is a cable section covered with corrugated polyimide, with a corrugation pitch of 5-8 mm and a stretchable stroke of 10-15 times the cable diameter.

[0010] The self-locking positioning mechanism includes a slider, a slot and a spring buckle. The slider is fixed to the end of the cable, the slot is engaged with the photovoltaic module junction box, and the unlocking force of the spring buckle is ≥50N.

[0011] The aerospace-grade waterproof and dustproof terminal uses a titanium alloy shell with gold-plated contacts inside, with a contact resistance of ≤0.5mΩ and a protection level of IP68.

[0012] The width-to-thickness ratio of the flat flexible structure is 3~5:1, the bending radius is ≤5 times the cable thickness, and it meets the requirement that the solar panel folding gap is ≤5mm.

[0013] The total vacuum outgassing rate of the connecting cable is ≤0.5%, and the condensable matter content is ≤0.1%, which meets the NASASP-R-0022A standard.

[0014] The insulation resistance of the connecting cable remains ≥1×10⁶ Gy after the gamma-ray radiation dose reaches 1×10⁶ Gy. 14 Ω·m, shielding effectiveness ≥80dB; after 2000 thermal cycles at -196℃ to +200℃, insulation resistance retention rate ≥98%.

[0015] The beneficial effects of this invention are: the composite conductor adopts a core-sheath structure of nanocrystalline copper and silver-magnesium-nickel alloy, combined with a BN protective layer, so that the resistivity increase after 1MeV electron radiation is ≤4%, and the gamma ray resistance is 1×10 6 After Gy, transmission loss is reduced by ≥60%, solving the problem of increased loss after radiation in existing conductors; the sandwich-structured atomic oxygen layer integrates braided shielding, PI / SiO2 substrate, and DLC coating, reducing the atomic oxygen erosion rate by ≥90% while achieving electromagnetic shielding effectiveness of ≥80dB, avoiding the weight redundancy and interlayer delamination risk of traditional separate designs; the graded functional insulation layer, through graded material composition design and co-extrusion process, achieves an interlayer bonding strength of ≥15MPa and an insulation resistance of ≥2000 cycles after thermal cycling from -196℃ to +200℃. With a retention rate of ≥98%, it solves the problem of thermal fatigue embrittlement of existing insulation layers; the flat and flexible shaping structure makes the bending radius ≤5 times the thickness, adapting to the folding gap of the solar array; the self-locking buffer module at the end achieves ≥2000 cycles of unfolding and retraction without damage; the weight of a single cable is reduced by ≥40%, meeting the lightweight requirements of multi-satellite launch and megawatt-level power plants; all materials use low-outgas formula, with a total outgassing rate ≤0.5% and condensable matter ≤0.1%, avoiding contamination of photovoltaic module optical components, and adapting to the full orbital environment from LEO to GEO and the requirements of 1500VDC high-voltage direct current transmission. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Figure 1 This is a schematic diagram of the internal cross-sectional structure of Embodiment 1 of the present invention.

[0018] Figure 2 This is a schematic diagram of the structure of the self-locking buffer module of the termination in this invention.

[0019] Figure 3 This is a schematic diagram of the internal cross-sectional structure of Embodiment 2 of the present invention.

[0020] In the diagram: 1. Composite conductor, 11. Central core wire, 12. Outer stranded wire, 13. BN protective layer; 2. Gradient functional insulation layer, 21. Inner insulation layer, 22. Intermediate buffer layer, 23. Outer insulation layer; 3. Sandwich structure shielding antigen oxygen layer, 31. Braided shielding layer, 32. PI / SiO2 composite substrate layer, 33. DLC coating; 4. Termination self-locking buffer module, 41. Elastic buffer section, 42. Self-locking positioning mechanism, 421. Slider, 422. Slot, 423. Spring snap, 43. Aerospace-grade terminal. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Example 1, Figure 1 , Figure 2 The embodiment shown provides a connection cable adapted to low-Earth orbit constellation space photovoltaic modules, with the following specific parameters: Composite conductor 1: The central core wire 11 is a Φ0.06mm Ag-0.2Mg-0.15Ni alloy wire, the outer stranded wire 12 is 6 Φ0.05mm nanocrystalline copper wires, and the surface is plated with a 2μm BN protective layer 13; the pitch ratio is 15, and it is pressed into a flat shape with a width of 0.5mm and a thickness of 0.2mm by a rectangular polycrystalline mold, with a DC resistance ≤1.2Ω / m.

[0024] Graded functional insulation layer 2: Inner insulation layer 21 is radiation-crosslinked XETFE with a thickness of 0.04 mm; intermediate buffer layer 22 is a PI / Al2O3 graded composite material, in which the Al2O3 content ranges from 10 wt% to 30 wt% with a thickness of 0.03 mm; outer insulation layer 23 is fluoropolymer rubber with a thickness of 0.025 mm; the three layers are co-extruded, with an interlayer bond strength of 18 MPa and a volume resistivity of 1.2 × 10⁻⁶. 15 Ω·m.

[0025] The sandwich structure shielding atomic oxygen layer 3 consists of: a silver-plated copper flat wire braided shielding layer 31, with flat wire parameters of 0.02mm × 0.15mm and a braiding density of 96%; a PI / SiO2 composite substrate layer 32, with 25wt% SiO2 and a thickness of 0.03mm; and a DLC coating 33, with a thickness of 1.2μm, processed using PECVD; the atomic oxygen erosion rate is 8 × 10⁻⁶. -25 cm 3 / atom, gamma rays 1×10 6 The shielding effectiveness after Gy is 85dB.

[0026] Termination self-locking buffer module 4: The elastic buffer section 41 is corrugated PI-coated with a corrugation pitch of 6mm and a telescopic stroke of 12mm; the unlocking force of the self-locking positioning mechanism 42 is 55N; the aerospace-grade terminal 43 has a titanium alloy shell, gold-plated contacts, a contact resistance of 0.4mΩ, and IP68 protection; the total length of the module is 50mm and the weight is ≤10g.

[0027] Overall performance: Flat structure, 1.0mm wide and 0.3mm thick, width-to-thickness ratio 3.3:1, bending radius 1.0mm; total vacuum outgassing rate 0.35%, condensable matter 0.08%; after 2000 thermal cycles from -196℃ to +200℃, insulation resistance retention rate 98.7%, breakdown field strength 28kV / mm; after 2000 expansion and contraction cycles, no interlayer peeling, no terminal loosening, transmission loss ≤1.2%.

[0028] Example 2, Figure 2 and Figure 3 This embodiment provides a connection cable adapted to megawatt-level space photovoltaic power stations. Based on embodiment 1, the current carrying capacity and protection level are optimized, and the specific adjustments are as follows: Composite conductor 1: The central core wire 11 is an Ag-0.2Mg-0.15Ni alloy wire with a diameter of 0.08mm, and the outer stranded wire 12 is 8 nanocrystalline copper wires with a diameter of 0.07mm. The flat size is 0.8mm×0.25mm, and the DC resistance is ≤0.55Ω / m.

[0029] Gradient functional insulation layer 2: Inner insulation layer 21 with a thickness of 0.05 mm, intermediate buffer layer 22 with a thickness of 0.04 mm, and outer insulation layer 23 with a thickness of 0.03 mm; interlayer bonding strength of 20 MPa, and breakdown field strength of 30 kV / mm.

[0030] Sandwich structure shielding atomic oxygen layer 3: inner layer silver-plated copper flat wire braided shielding layer 31 density 97%, DLC coating 33 thickness 1.5μm; atomic oxygen erosion rate 7×10 -25 cm 3 / atom, shielding effectiveness 88dB.

[0031] Overall performance: Flat structure, 1.5mm wide and 0.4mm thick, width-to-thickness ratio 3.75:1, bending radius 1.5mm; single-piece weight reduction of 45%, vacuum current carrying capacity increased by 50%; γ-ray emission 1×10 6 After Gy, the resistivity increase is ≤3%, and the transmission loss is ≤0.8% after 2000 extension and retraction cycles, meeting the high current transmission requirements of megawatt-level power plants.

[0032] Key process description Composite conductor 1 preparation: Nanocrystalline copper wire is prepared by equal channel angle extrusion process, and the grain size is controlled to ≤100nm; silver magnesium nickel alloy wire and nanocrystalline copper wire are drawn and plated with BN respectively, and then twisted together with a pitch ratio of 14~16, and then pressed and shaped by rectangular polycrystalline mold to ensure that the flat structure does not flip or twist.

[0033] Gradient functional insulation layer 2 co-extrusion: A three-layer synchronous co-extrusion equipment is used. The melt temperatures of the inner insulation layer 21, the intermediate buffer layer 22, and the outer insulation layer 23 are controlled at 320℃, 380℃, and 280℃, respectively. The concentricity error of the die head is ≤0.01mm, achieving gapless bonding between layers.

[0034] Sandwich structure shielding antigen oxygen layer 3 deposition: The inner silver-plated copper flat wire braided shielding layer 31 is made by flat wire braiding machine to control the braiding tension uniformly; the PI / SiO2 composite substrate layer 32 is formed by casting, and the SiO2 nanoparticles are surface modified to improve the compatibility with PI; the DLC coating 33 is deposited by PECVD process with the following process parameters: RF power 300W, CH4 / Ar volume ratio of reaction gas 1:5, deposition temperature 150℃, ensuring coating adhesion ≥20N / 25mm peel strength.

[0035] The self-locking buffer module 4 is assembled as follows: the PI corrugated layer of the elastic buffer section 41 is molded and connected to the cable body by laser welding; the slider and slot 422 of the self-locking positioning mechanism 42 are made of 3D printed titanium alloy, and the spring buckle 423 is made of high temperature resistant stainless steel; the connection between the terminal 43 and the cable is made by ultrasonic welding to ensure no loose connection in a vacuum environment.

[0036] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A connecting cable for photovoltaic modules in a vacuum environment, comprising a composite conductor (1), a gradient functional insulation layer (2) sequentially covering the outside of the composite conductor (1), a sandwich-structured shielding antigen oxygen layer (3), and a termination self-locking buffer module (4) connected to the cable end; the cable as a whole has a flat, flexible, and shaped structure, characterized in that: The composite conductor (1) is a nanocrystalline copper-silver magnesium-nickel composite stranded conductor, consisting of a central core wire (11) and an outer stranded wire (12). The central core wire (11) is an Ag-0.2Mg-0.15Ni alloy wire, and the outer stranded wire (12) is a nanocrystalline copper wire. The surface of the nanocrystalline copper wire is plated with a 2μm thick boron nitride protective layer (13). The section diameter ratio of the composite conductor (1) is 14~16, the diameter of a single wire is 0.05~0.08mm, and after stranding, it is pressed and shaped into a flat shape by a rectangular polycrystalline mold. The gradient functional insulation layer (2) is a three-layer co-extruded structure, consisting of an inner insulation layer (21), an intermediate buffer layer (22), and an outer insulation layer (23) from the inside out. The inner insulation layer (21) is irradiated crosslinked XETFE with a thickness of 0.03~0.05 mm. The intermediate buffer layer (22) is a polyimide / nano-alumina gradient composite material with the nano-alumina content increasing from 10 wt% to 30 wt% from the inside out, and a thickness of 0.02~0.04 mm. The outer insulation layer (23) is fluoroether rubber with a thickness of 0.02~0.03 mm. The sandwich structure shielding antigen oxygen layer (3) includes an inner silver-plated copper flat wire braided shielding layer (31), a middle PI / SiO2 composite substrate layer (32), and an outer diamond-like carbon antigen oxygen coating layer (33). The terminator self-locking buffer module (4) includes an elastic buffer section (41), a self-locking positioning mechanism (42), and an aerospace-grade waterproof and dustproof terminal (43).

2. The connecting cable for photovoltaic modules in a vacuum environment according to claim 1, characterized in that: The nanocrystalline copper wire has a grain size ≤100nm, is prepared by a severe plastic deformation process, and has a resistivity increase of ≤4% after 1MeV electron radiation.

3. The connecting cable for photovoltaic modules in a vacuum environment according to claim 1, characterized in that: The three-layer structure of the gradient functional insulation layer (2) is formed by synchronous co-extrusion, with an interlayer bonding strength ≥15MPa and a volume resistivity ≥1×10⁻⁶. 15 Ω・m.

4. The connecting cable for photovoltaic modules in a vacuum environment according to claim 1, characterized in that: The braided shielding layer (31) has a braiding density of ≥95%, a flat wire thickness of 0.02 mm, and a width of 0.15 mm; the PI / SiO2 composite substrate layer (32) has a SiO2 content of 25 wt% and a thickness of 0.03 mm; the diamond-like carbon coating (33) has a thickness of 1~1.5 μm and is deposited by PECVD process.

5. A connecting cable for photovoltaic modules in a vacuum environment according to claim 1, characterized in that: The elastic buffer section (41) is a cable section covered with corrugated polyimide, with a corrugation pitch of 5~8mm and a stretchable stroke of 10~15 times the cable diameter.

6. A connecting cable for photovoltaic modules in a vacuum environment according to claim 1, characterized in that: The self-locking positioning mechanism (42) includes a slider (421), a slot (422) and a spring buckle (423). The slider (421) is fixed to the end of the cable, the slot (422) is engaged with the photovoltaic module junction box, and the unlocking force of the spring buckle (423) is ≥50N.

7. A connecting cable for photovoltaic modules in a vacuum environment according to claim 1, characterized in that: The aerospace-grade waterproof and dustproof terminal (43) uses a titanium alloy shell and is equipped with gold-plated contacts inside. The contact resistance is ≤0.5mΩ and the protection level reaches IP68.

8. A connecting cable for photovoltaic modules in a vacuum environment according to claim 1, characterized in that: The width-to-thickness ratio of the flat flexible structure is 3~5:1, the bending radius is ≤5 times the cable thickness, and it meets the requirement that the solar panel folding gap is ≤5mm.

9. A connecting cable for photovoltaic modules in a vacuum environment according to claim 1, characterized in that: The total vacuum outgassing rate of the connecting cable is ≤0.5%, and the condensable matter content is ≤0.1%.

10. A connecting cable for photovoltaic modules in a vacuum environment according to claim 1, characterized in that: The connecting cable is exposed to gamma-ray radiation doses of up to 1×10⁻⁶. 6 After Gy, the insulation resistance remains ≥1×10 14 Ω·m, shielding effectiveness ≥80dB; after 2000 thermal cycles at -196℃ to +200℃, insulation resistance retention rate ≥98%.

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