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Power System Architecture for Qatar University Cubesat (Phase II) Abdelrhamn Abdalla, Abdallahi Ahmed, Abdulrahman Hussein and Moumen El-Hassan Supervisors: Dr. Atif Iqbal & Dr. Ahmed Massoud Qatar University Department of Electrical Engineering, College of Engineering Spring 2015 Abstract The role of the power supply architecture of Qatar University Cubesat is supplying all the satellite subsystems by their power requirements. The architecture composes from different stages including power generation, storage and finally distribution. Different MPPT (maximum power point tracking) algorithm has been studied and compared with Perturbed &Observed (P&O) method that is designed by previous group, to compare the response of each technique under different conditions. in this project a new class of solar PV with three junctions is used. A prime mathematical model for triple junction PV has been developed and simulated under the effect of different parameters. H∞based closed-loop control is designed to control DC-DC converters and the design has been studied in terms of transient overshoot and steady state error and the results shows that how robust is the controller and it shows that it is the perfect choice for the CubeSat application. Introduction Mission Statement Qatar university Cubesat (Qubesat) mission is to map and observe the current waste disposal sites in Qatar and search for the illegally disposed waste in the desert. To achieve that, a camera will be attached to the Cubesat to capture images of the desired sites. Background To achieve this goal, the technical aspects of the project are performed through five different systems. The division is illustrated below. The system configuration for the On-Board Electric Power Supply System (OBEPSS) can be well visualized as illustrated in figure 1 Parameter Value InGaP Short Circuit Current ISC1 13.78 mA/cm2 GaAs Short Circuit Current ISC2 15.74 mA/cm2 Ge Short Circuit Current ISC3 20.60 mA/cm2 STC Irradiance GSTC 0.1W/cm2 STC Temperature TSTC 298 K InGaPBandgap Energy 1.86eV GaAsBandgap Energy 1.40eV GeBandgap Energy 0.65eV Cell Area 0.2663 cm2 Ideality Constant for all cells 2 Gamma γ (Sharp Cell) 2 Series Resistance 0.0134Ω 1 for cell 1α 5.771X10-4 2 for cell 2α 5.405X10-4 3 for cell 3α 4.774X10-4 Beta Constant β1 (Cell 1) 372 Beta Constant β2 (Cell 1) 204 Beta Constant β3 (Cell 1) 235 Figure 3. Neural Network Training Regression Table 2: Data used to test the network and output results Simulation Results temp C 39.8 42.9 Irr. W/m2 868 1066.6 expected output voltage (V) 32.12 28.03 Output from ANN (V) 31.9 I-V Curve of Triple Junction P-V Curve of Triple Junction 35 15 10 5 Power W/cm2 30 InGaP GaAs Ge 25 15 10 InGaP GaAs Ge 5 0 0 0.5 1 1.5 Voltage (V) (a) 2 2.5 0 0 0.5 1 1.5 Voltage (V) 2 29 (b) Figure 2. (a) I-V (b) P-V Curve for triple junction matched current density Experimental setup 29.45 Controller Rejection 2.5 28 27 26 25 24 23 9.06 9.08 9.1 9.12 9.14 9.16 9.18 9.2 9.22 9.24 4 -4 Time(10 s) x 10 Figure 4. H-∞Controller Response Figure 1. Hardware Overview of the power supply of the Cubesat Conclusion The power supply architecture of the Cubesat was designed. Single PV solar panel has been modeled and simulated under different real space conditions including soft and hard shading. In addition to that, a primary modeling of triple junction PV solar panel has been done and simulated for various parameters such as irradiance and temperature. This is one of the major contributions of phase II. No such model is available in the literature and hence this is the novelty of the work. Results of triple junction model were compared to the results and data provided by Space Clyde to Qatar University and, it shows that the model is an appropriate one. For the maximum power point tracking, different algorithms studied including P&O which is modeled and tested during phase I and the conclusion of this comparison study is that ANN MPPT algorithm has fast and stable response compared to P&O algorithm. Based on this MPPT using ANN algorithm has been done for simulated data and practical readings. Moreover, H-∞ based closed-loop control is designed to control DC-DC converters and the design has been studied in terms of transient overshoot and steady state error and the results shows that how robust is the controller and it shows that it is the perfect choice for the CubeSat application. Future work 20 Amplitude(mV) System Overview Table 1: Simulation Parameters of triple junction Current Density mA/cm2 The OBEPSS is responsible for delivering the power required to power the satellite efficiently. This process involves power generation through photovoltaic panels, power storage, power control, and power distribution to on board loads. The MECHS is responsible for designing the structure that houses the satellite equipments and protects it against vibration and extreme thermal changes in the low earth orbit (LEO). The COMS is responsible to assure a reliable communication (Uplink and Down-link) between the satellite and the ground station. The ACS is responsible for adjusting the position of the Cubesat The GSS is responsible for controlling the satellite and reviving the health of it in the space. In addition it receives the required data to achieve the mission of the satellite. Practical Result Simulation Parameters of triple junction Inphase III, Implementation is the main task to be done, starting from the converters designed and simulated in phase II and, going through tests of these converters with the triple junction as input. MPPT using ANN has been done and results can be used to design the MPPT converter. For more advanced power system, single input single output converters can be exchanged with single input multi output converter which will decrease the space needed for the converters in a significant way. Acknowledgements The authors would like to thank their supervisors Dr. Atif Iqbal and Dr. Ahmed Massoud and the Department of Electrical Engineering in Qatar University. In addition, the authors would like to express their gratitude toward both Dr. Nader Meskin and Eng. Ben Pratheesh for their Help.