Dynamic and static potential balance method for reducing primary discharge risk of spacecraft high-voltage solar cell array

Abstract

The invention discloses a dynamic and static potential balance method for reducing the primary discharge risk of a spacecraft high-voltage solar cell array, and belongs to the technical field of spacecraft power supply system protection. The method comprises the following steps: firstly, obtaining local potential distribution of high-voltage solar cells according to spacecraft surface suspension potential and circuit structure characteristics of a high-voltage solar cell array; then calculating the maximum suspension potential difference among the substrates, the interconnection sheets and the glass cover sheets of different battery strings to obtain a potential difference needing to be balanced; and finally, according to the distributed capacitance and the bias time of the high-voltage solar cell array, calculating to obtain a dynamic bias resistance value, a static bias capacitance and a balanced suspension potential. According to the invention, the worst suspension potential difference of the spacecraft high-voltage solar cell array can be effectively reduced, the risk of primary discharge is greatly reduced, and the power supply reliability of the space high-voltage solar cell array is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of spacecraft power system protection, and in particular relates to a dynamic and static potential balancing method for reducing the primary discharge risk of a spacecraft high-voltage solar cell array. Background Art

[0002] With the continuous development and progress of my country's space station and satellite technology, the demand for spacecraft power systems continues to increase, and ultra-high power power systems have become the development trend of the next generation of spacecraft energy systems. In order to meet the high power demand, high voltage and high current can be used for transmission, but high current transmission will bring about problems such as huge power cable weight and loss. Therefore, high voltage and low current high-voltage solar cell arrays have become an inevitable choice. However, the large area of ​​high-voltage solar cell arrays exposed to space plasma will interact with the plasma in the space environment to cause surface charging, and generate a reverse potential gradient between the substrate-interconnection sheet-insulation part (also known as the "three-junction") of the solar cell array. The high voltage exacerbates the suspension potential difference at the three-junction. When the potential difference reaches a certain value, it is very easy to induce a discharge under the action of space plasma, and even cause a continuous discharge arc, causing the solar cell array to short-circuit and burn, which seriously threatens the safe operation of the spacecraft.

[0003] The fundamental reason for the discharge of space high-voltage solar arrays is the coupling of high potential difference and space plasma. Based on these two points, the discharge can be suppressed. At present, the main discharge protection measures for space high-voltage solar arrays are to reduce the voltage between strings, reduce the string current, plate the conductive layer on the surface of the glass cover, fill RTV glue and use active potential controller. The two measures of reducing the voltage between strings and reducing the string current cannot meet the needs of high-voltage and high-power space solar arrays. The surface conductive layer is plated to suppress the discharge by reducing the local unbalanced potential on the surface of the solar array. Filling RTV glue is to increase the discharge breakdown voltage or isolate the discharge probability by adding insulation to the discharge path. Both methods suppress the discharge phenomenon by using special materials, but the material performance attenuation, preparation process and weight increase need to be considered. The use of active potential controller is to use plasma emitters to achieve the purpose of actively controlling the potential, but there are problems such as equipment performance attenuation, equipment installation and volume weight increase. Summary of the invention

[0004] In order to address the deficiencies in the prior art, the present invention proposes a dynamic and static potential balancing method for reducing the risk of primary discharge of a spacecraft high-voltage solar array. The method mainly adopts a method of adding dynamic bias resistors and static bias capacitors between the spacecraft structure, the bus positive end, the bus negative end and the solar array substrate to dynamically and statically balance the local harsh potential distribution of the high-voltage solar array, thereby reducing the worst floating potential difference at the three-junction point where primary discharge is prone to occur, thereby achieving the purpose of reducing the risk of primary discharge.

[0005] The present invention provides a dynamic and static potential balancing method for reducing the primary discharge risk of a spacecraft high-voltage solar cell array, and the specific steps are as follows:

[0006] Step 1: According to the connection and distributed capacitance characteristics between the high-voltage solar array and the spacecraft structure, obtain the suspension potential of different parts of the high-voltage solar array, including the negative suspension potential U between the spacecraft structure and the solar array substrate. 结-基 , the surface potential of the solar array is U 表 , and the interconnection sheet potential U of the upper and lower battery strings 上串互连片 with U 下串互连片 .

[0007] Step 2: Based on the suspension potentials of different parts of the high-voltage solar cell array obtained in step 1, the worst suspension potential difference and the balanced potential difference ΔU at the three junctions of the upper cell string and the lower cell string are calculated respectively.

[0008] Step 3: Add a dynamic bias resistor, and calculate the positive and negative terminal potentials of the solar cell array after bias according to the dynamic bias resistor voltage divider relationship. Combined with the ΔU obtained in step 2, the relationship between the dynamic bias resistor and the potential after bias is obtained.

[0009] Step 4: Considering the time required for biasing when the floating potential changes, the static bias capacitance and the distributed capacitance of the solar cell array, combined with the relationship equations between the dynamic bias resistance and the bias potential in step 3, the dynamic bias resistance value, the static bias capacitance and the balanced floating potential are calculated.

[0010] The advantages of the present invention are:

[0011] 1. The dynamic and static potential balancing method of the present invention for reducing the primary discharge risk of a spacecraft high-voltage solar cell array only requires adding a dynamic bias resistor between the spacecraft structure, the bus positive end, the bus negative end and the solar cell array substrate to achieve floating potential balance, reduce the worst floating potential difference at the three junctions of the solar cell panels, and achieve the purpose of reducing the primary discharge risk. The method is simple and easy to implement, and there is no need to consider the problems of protective material degradation, device reliability, performance attenuation, etc., and has high reliability.

[0012] 2. The present invention provides a dynamic and static potential balancing method for reducing the risk of primary discharge of a spacecraft high-voltage solar array. When the distributed capacitance of the solar array is unbalanced, it is difficult for the dynamic bias resistor to achieve floating potential balance. Increasing the static bias capacitor can solve the problem of distributed capacitance imbalance and achieve dynamic and static balance of the floating potential at the same time.

[0013] 3. The dynamic and static potential balancing method of the present invention for reducing the risk of primary discharge of a high-voltage solar array in a spacecraft takes into account the potential bias time, keeping it at the level of hundreds of milliseconds to seconds, and has the characteristic of high balancing efficiency; and takes into account the power consumption of the dynamic bias resistor, which only accounts for less than one thousandth of the power of the power supply system, and will not cause any impact on the power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A flow chart of a dynamic and static potential balancing method for reducing the primary discharge risk of a spacecraft high-voltage solar cell array according to the present invention;

[0015] Figure 2 The invention discloses a circuit structure of a high-voltage solar array of a spacecraft and a schematic diagram of its local equivalent.

[0016] Figure 3 It is a local equivalent schematic diagram after adding dynamic bias resistance and static bias capacitance to the high-voltage solar cell array of the spacecraft. DETAILED DESCRIPTION

[0017] The present invention will be described in further detail below with reference to the accompanying drawings.

[0018] The present invention provides a dynamic and static potential balancing method for reducing the primary discharge risk of a spacecraft high-voltage solar cell array, such as Figure 1 As shown, the specific steps include:

[0019] Step 1: Obtain the suspension potential of different parts of the high-voltage solar array.

[0020] like Figure 2 As shown, the substrate of the high-voltage solar array is connected to the spacecraft structure through a resistor. In the space plasma environment, a surface charging effect occurs, absorbing a large number of electrons. Therefore, relative to the zero potential at a distance, the spacecraft structure and the solar array substrate are at a negative floating potential U 结-基 Due to the influence of various factors such as incident electrons, ions and secondary electron emission, the surface potential of the conductive layer on the solar cell array is U relative to the zero potential at a distance. 表 ; Since the distributed capacitance between different solar cell strings and the substrate is approximately equal, the interconnection potential of the upper and lower cell strings can be obtained as:

[0021] U 上串互连片 =U 正端 =U结-基 +(U 正端 -U 负端 ) / twenty one)

[0022] U 下串互连片 =U 负端 =U 结-基 -(U 正端 -U 负端 ) / twenty two)

[0023] Among them, U 正端 , U 负端 They are the positive and negative terminal potentials of the high-voltage solar array respectively.

[0024] Step 2: Calculate the worst potential difference and the potential difference after equilibrium;

[0025] From equations (1) and (2), we can see that relative to the substrate potential of the solar cell array, the interconnection sheet potentials of the upper and lower cell strings are biased positively and negatively, respectively. Combined with the surface potential, it can be obtained that the worst potential difference is between the surface of the lower cell string and the interconnection sheet. Therefore, the potential differences that need to be balanced are:

[0026]

[0027] Among them, ΔU1 and ΔU2 are the potential differences that need to be balanced between the upper and lower string interconnects, respectively.

[0028] Then the potential difference between the upper and lower strings after the interconnection is balanced is:

[0029]

[0030] Step 3: Add dynamic bias resistance to balance the floating potential;

[0031] like Figure 2 As shown, dynamic bias resistors R1 and R2 are added to the positive and negative ends of the busbar of the high-voltage solar array to make U 正端 and U 负端 Relative to the remote zero potential, even if U 上串互连片 and U 下串互连片 The potential shifts, U 正端 and U 负端 The potentials after bias are:

[0032]

[0033]

[0034] Among them, ΔU 偏置1 With ΔU 偏置2 U 正端 and U 负端 Bias potential.

[0035] And ΔU 偏置1 and ΔU 偏置2 Satisfaction relationship:

[0036] (ΔU 偏置1 +ΔU 偏置2 )=U 正端 -U 负端 (8)

[0037] Then the potential difference between the upper battery string and the lower battery string after balancing can also be expressed as:

[0038] ΔU=|U 上串互连片-偏置后 -U 结-基 |=|U 表 -U 下串互连片-偏置后 | (9)

[0039] The above equations 6 to 9 constitute a set of equations for the relationship between the potential before and after the dynamic bias resistance is added and the dynamic bias resistance.

[0040] Step 4: Calculate the dynamic bias resistance and static bias capacitance;

[0041] Considering the distributed capacitance charging time t after adding the dynamic bias resistor, that is, the bias time, it is taken as 5 times the time constant:

[0042] t = 5 × τ = 5 × R 总 ×C 总 (10)

[0043]

[0044] In the formula, R 总 is the sum of the dynamic bias resistors, R 总 =R1+R2; C 分布1 and C 分布2 are the distributed capacitance values ​​between the two solar cell strings and the substrate respectively. C1 and C2 are bias capacitances in μF level.

[0045] Therefore, R can be obtained through equations (10) and (11): 总 ; Further, according to the equilibrium potential difference and the resistor voltage divider relationship given in step 3, the dynamic bias resistors R1 and R2 can be obtained; finally, according to the substrate potential U 结-基 , surface conductive layer potential U 表 As well as the potential difference ΔU after the upper battery string and the lower battery string are balanced, the potential U after the upper string and the lower string are biased can be obtained. 正端-偏置后 with U 负端-偏置后 .

[0046] The power loss of the dynamic bias resistor can also be calculated:

[0047]

[0048] It is required that the power loss of the dynamic bias resistor accounts for less than one thousandth of the power of the power system and will not affect the normal operation of the power supply and distribution of the entire spacecraft power system.

[0049] Example:

[0050] This example takes a spacecraft in low orbit as an example. The bus voltage of the power system is 400V, that is, U 正端 -U 负端 =400V, working power is 20kW, surface charging effect occurs in LEO (Low Earth Orbit) plasma environment, U 结-基 =-120V, U 表 =5V. When no dynamic bias resistor is added, the interconnection potentials of the upper and lower solar cell arrays can be obtained as follows: U 上串互连片 =80V, U 下串互连片 =-320V, the corresponding two strings of bad potential differences are: ΔU1 = |U 上串互连片 -U 结-基 |=200V,ΔU2=|U 下串互连片 -U 表 |=325V, it can be seen that the lower battery string has the worst floating potential difference and the highest discharge risk. The potential difference after balancing should be ΔU=(ΔU1+ΔU2) / 2=262.5V; take the bias time t=1s, the distributed capacitance C 分布1 =C 分布2 =100nF, C1=C2=2μF, R 总 =R1+R2≈200kΩ. According to the relationship between the equilibrium potential difference and the dynamic bias resistance, the dynamic bias resistance R1=131.25kΩ, R2=68.75kΩ. The floating potential after equilibrium is: U 上串互连片-偏置后 =142.5V, U 下串互连片-偏置后 =-257.5V, at this time, the worst potential difference is reduced from 325V to 262.5V, which greatly reduces the risk of breakdown discharge, and the power consumed by the dynamic bias resistor is 0.8W, which only accounts for 4 / 100000 of the power of the power supply system, and will not have any impact on the normal operation of the system power supply and distribution system. When the distributed capacitance is unbalanced, take C 分布1 =10nF, C 分布2 =100nF, at this time the static bias capacitance C1=C2=2uF, which is much larger than the distributed capacitance. Therefore, under the joint action of the bias resistor and capacitor, the above-mentioned floating potential balance can still be achieved.

Claims

1. A dynamic and static potential balancing method to reduce the risk of primary discharge of high-voltage solar arrays in spacecraft, Features: The steps include: Step 1: According to the connection and distributed capacitance characteristics between the high-voltage solar array and the spacecraft structure, obtain the suspension potential of different parts of the high-voltage solar array, including the negative suspension potential U between the spacecraft structure and the solar array substrate. 结-基 , the surface potential of the solar array is U 表 , and the interconnection sheet potential U of the upper and lower battery strings 上串互连片 with U 下串互连片 ; Step 2: Based on the suspension potentials of different parts of the high-voltage solar cell array obtained in step 1, the worst suspension potential difference and the balanced potential difference ΔU at the three junctions of the upper cell string and the lower cell string are calculated respectively; Step 3: Add a dynamic bias resistor, and calculate the positive and negative terminal potentials of the solar cell array after biasing according to the dynamic bias resistor voltage divider relationship. Combined with the ΔU obtained in step 2, the relationship between the dynamic bias resistor and the potential after biasing is obtained. Step 4: Considering the time required for biasing when the floating potential changes, the static bias capacitance and the distributed capacitance of the solar cell array, combined with the relationship equations between the dynamic bias resistance and the bias potential in step 3, the dynamic bias resistance value, the static bias capacitance and the balanced floating potential are calculated.

2. A method for dynamic and static potential balancing for reducing the primary discharge risk of a high voltage solar array of a spacecraft as claimed in claim 1, Features: The worst floating potential difference at the three junctions of the upper battery string and the lower battery string is: ΔU 1 =|U 上串互连片 -U 结-基 ΔU 2 =|U 下串互连片 -U 表 | Then the potential difference between the upper battery string and the lower battery string after balancing is:

3. A method for dynamic and static potential balancing for reducing the primary discharge risk of a high voltage solar array of a spacecraft as claimed in claim 1, Features: In step 3, add dynamic bias resistors R at the positive and negative ends of the busbar. 1 and R 2 , making U 正端 and U 负端 Relative to the remote zero potential, even if U 上串互连片 and U 下串互连片 The potential of the positive and negative terminals of the solar cell array after bias is shifted, respectively: And ΔU 偏置1 and ΔU 偏置2 Satisfaction relationship: (ΔU 偏置1 +ΔU 偏置2 )=U 正端 -U 负端 The potential difference between the upper battery string and the lower battery string after balancing is expressed as: ΔU=|U 上串互连片-偏置后 -U 结-基 |=|U 表 -U 下串互连片-偏置后 | 4. A method for dynamic and static potential balancing for reducing the primary discharge risk of a spacecraft high voltage solar array as claimed in claim 1, Features: In step 4, the floating potential bias time after adding the dynamic bias resistor, that is, the charging time of the distributed capacitance and the static bias capacitance, is taken as 5 times the time constant: t=5×τ=5×R 总 ×C 总 In the formula, R 总 is the sum of the dynamic bias resistors, R 总 =R 1 +R 2 , C 分布1 and C 分布2 are the distributed capacitance between the two solar cell strings and the substrate, the static bias capacitance C 1 and C 2 Take μF level; combine the potential difference after equilibrium and the relationship between the floating potential to obtain the dynamic bias resistance and power loss.

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