Design and Implementation of On-board Electrical Power ... - OUFTI-1

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• Voltage (4) and current (5) at maximum power point (3) on Figure 3.4.Figure 3.4: I-V curve of Si solar cell in sunlight.The I-V curve is dependant upon several environmental parameters. The most importantare:• The temperature.The short-circuit current is slightly increased with temperature while the open-circuitvoltage is decreased. In usual temperature ranges, the efficiency of solar cells decreaseswith temperature.• The light exposure.The current increases with light intensity. The wavelength of the light has an influence.I-V curves are generally given for a particular spectrum. “Air Mass Zero (AM0)” is thespectrum of the sunlight in space, at the sun-earth distance. AM1.5 is the spectrum onearth.• The age.Radiations tend to decrease the efficiency over time. Commonly used terms to definethe age of a solar cell are “Begin Of Life” (BOL) and “End Of Life” (EOL).3.2.2 Azurspace’s solar cellsAzurSpace is a German company that produces solar cells for space application since 1969.More than 340 satellites have been equipped with their products. The company contributesto our project by providing the solar cells for OUFTI-1. They are triple-junction GaAs solarcells. This kind of solar cell has a high efficiency and is commonly used in space application.22
Figure 3.5: 3G - 28% solar cell from AzurSpace.The last commercialized model, the “3G - 28%” (figure 3.5), has an efficiency of 28% at BeginOf Life (BOL), but a new model with 30% efficiency at BOL will be tested on OUFTI-1.The dimensions of the solar cells are 80mm x 40mm with cropped corners, for a totalsurface of 30.18cm 2 .Azurspace provided a document with electrical data for the 30% cells (table 3.1). The shortcircuit current is thus 528.15 mA for one cell, and the current at max. power is 513.06mA.Open Circuit Voltage V OC [mV ] 2,716Short Circuit Current J SC [mA/cm 2 ] 17.5Voltage at max. Power V pmax [mV ] 2,427Current at max. Power J pmax [mA/cm 2 ] 17.0Maximum Power P pmax [mW/cm 2 ] 41Average Efficiency η bare [%] 30.1Table 3.1: Electrical characteristics of Azurspace 3G - 30% solar cells at 28 ◦ C and for theAM0 spectrum [23].3.2.3 Simple modelAn ideal solar cell can be modelled by a reverse-biased diode (PN junction) in parallel with acurrent source (photovoltaic effect). A more practical model includes a shunt resistor and aseries resistor. The equivalent circuit is shown on Fig.3.6, where R sh is the shunt resistanceand R s the series resistance.The R sh resistance has generally a value of several hundreds Ohm. The current in R sh isvery small compared to the other currents, and the effect of R sh can thus be neglected [17].Solar cell models without R sh give satisfactory results.Thus, ignoring the shunt resistor, the equations giving the relation between V and I arethenV = V j − IR sI = I L − I D23
Page 2 and 3: AcknowledgementsI want to thank the
Page 4 and 5: Contents1 Introduction 91.1 Cubesat
Page 6 and 7: 4.4.2 Mean case . . . . . . . . . .
Page 8 and 9: B Power budget worksheet 106C Pictu
Page 10 and 11: design and the tests are delegated
Page 12 and 13: Chapter 2Requirements of the EPS2.1
Page 14 and 15: • The Single-Event Upset (SEU)Thi
Page 16 and 17: the P-POD. RBF pins must fit within
Page 18 and 19: Figure 2.6: Top view of the PC104 c
Page 20 and 21: Chapter 3Design of EPS architecture
Page 24 and 25: Figure 3.6: The equivalent circuit
Page 26 and 27: of our Lithium-Polymer batteries va
Page 28 and 29: Figure 3.12: I-V curve of a solar p
Page 30 and 31: 3.3.3 CapacityA important value to
Page 32 and 33: Parameter SLPB723870H4 SLPB554374HN
Page 34 and 35: of the batteries is kept between -2
Page 36 and 37: Over Charge Prohibition 4.275 ± 0.
Page 38 and 39: supplied in 5V. The circuit will be
Page 40 and 41: Chapter 4The Power Budget4.1 Introd
Page 42 and 43: Figure 4.1: P-V curve of a solar pa
Page 44 and 45: 4.3.2 Efficiency of convertersTo at
Page 46 and 47: Figure 4.3: Consumptions in % in me
Page 48 and 49: Chapter 5Electrical Design of EPS5.
Page 50 and 51: V outV in= D. (5.1)Since D ≤ 1, t
Page 52 and 53: The power losses in the inductor ar
Page 54 and 55: ∆i L,1 + ∆i L,2 = 0, (5.16)V in
Page 56 and 57: Using the value of ∆i L given by
Page 58 and 59: There is no data about the case to
Page 60 and 61: Capacitor selectionFour 10µF ceram
Page 62 and 63: • Output voltage: 5V.• Maximum
Page 64 and 65: Figure 5.12: Burst mode operation (
Page 66 and 67: Figure 5.14: Simplified schematics
Page 68 and 69: Figure 5.15: Worksheet for 3.3V con
Page 70 and 71: sequently, the k was chosen above 0
Page 72 and 73:
where G 1 is the initial control-to
Page 74 and 75:
Figure 5.21: Measured Bode diagram
Page 76 and 77:
Figure 5.26: Equivalence between th
Page 78 and 79:
C f =12πf f R 0f,L f = R 2 0f C f
Page 80 and 81:
Figure 5.37: Schematics of the firs
Page 82 and 83:
R KR >1.45V100mA − 1.3A35= 23.07
Page 84 and 85:
The schematics is shown on figure 5
Page 86 and 87:
A commercial model meets all requir
Page 88 and 89:
Figure 5.45: Schematics of the heat
Page 90 and 91:
PrefixX7X5Y5Z5SuffixTemperature ran
Page 92 and 93:
6.2.1 The second dissipation system
Page 94 and 95:
• The antenna deployment system.
Page 96 and 97:
6.3.3 TestsThe engineering model of
Page 98 and 99:
7.3 ActivitiesAs OUFTI-1 is designe
Page 100 and 101:
8.1.2 DesignA model of Li-Po batter
Page 102 and 103:
[15] Fabien Jordan, Phase B Electri
Page 104 and 105:
TaK = 273 + TaC;%Photo-current ther
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Appendix BPower budget worksheetIn
Page 108 and 109:
108
Page 110 and 111:
Appendix CPictures of the prototype
Page 112 and 113:
Appendix DSchematics of the enginee
Page 114 and 115:
876543213V3 CONVERTER AND INPUT FIL
Page 116:
87654321ANTENNA DEPLOYMENT CIRCUITB
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