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

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of our Lithium-Polymer batteries varies between 2.7V and 4.2V, depending on the state ofcharge/discharge.The solar cells of one face will be connected in series. This forms a “solar panel”. Connectingtwo cells in series does not pose any problem. The current in each cell will be thesame as for one cell alone.Five solar panels are connected in parallel on the batteries bus. If a solar panel does notproduce enough power, it will be crossed by a negative current. This current is lost for theCubeSat and could even damage the solar cells.Therefore, solar panels have to be protected by a diode. To minimize the power loss onthe diode, a Schottky rectifier is used. The voltage at the terminals of the used Schottkyrectifier is between 0.5V and 0.6V. Figure 3.9 shows the electrical schematics of a solar panel.The voltage at the terminal of a solar panel will be the voltage of two solar cells minus thevoltage of the diode.Figure 3.9: Components and schematics of a solar panel.It is interesting to plot the I-V and P-V curves of a solar panel. The curve of one solarcell is already known. A model of Schottky rectifier has been chosen. The I-V curve of aSchottky rectifier has been measured and integrated to Matlab. The Matlab code used toplot the I-V and P-V curves of the solar panels is shown in the Appendix A. Figures 3.10 and3.11 show the characteristics of the solar panel for temperatures of -35 ◦ C, 5 ◦ C, and 45 ◦ C,with full insolation (G nom = 1350W/m 2 ). Figures 3.10 and 3.11 show the I-V and P-V curvesfor insolation of 0.25G nom , 0.5 G nom , 0.75 G nom , and G nom , when the temperature is 5 ◦ C.The voltage applied on a solar panel is the voltage of the batteries (V batt ). The poweroutput of a solar panel is thus dependent of the state of the batteries. In other words, thefigure 3.11 can be interpreted as the power output of a solar panel under full insolation as afunction of the batteries voltage.The following statements can be deduced from figure 3.11.• The maximum amount of power lost because V batt > V mpp is around 0.35W. This occurswhen V batt = 4.2V and T = 45 ◦ C. The output power is then around 1.65W.• The maximum amount of power lost because V batt < V mpp is around 1.2W. This occurswhen V batt = 2.6V and T= -35 ◦ C. The output power is then around 1.3W.26
Figure 3.10: I-V curve of a solar panel for tree temperatures and under a full insolation(G nom ).Figure 3.11: P-V curve of a solar panel for tree temperatures and under a full insolation(G nom ).• The MMP cannot be reached when the temperature is under around 10 ◦ C.• The maximum reachable output power is around 2.2W. V batt must be maximum (4.2V)and the temperature must be under around 10 ◦ C.• For V batt∼ = 4V and a temperature between 5 ◦ C and 35 ◦ C (most of time the case for apanel exposed to sun), the operating point is close to the MPP.27
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 22 and 23: • Voltage (4) and current (5) at
Page 24 and 25: Figure 3.6: The equivalent circuit
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
Page 106 and 107:
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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