Introduction

1. Power System Architecture for Qatar University Cubesat Abdulaziz AlKuwari, Hassan Miqdad and Ahmed Diab Supervisors: Dr. Ahmed Massoud & Dr.Tamer Khattab Qatar UniversityDepartment of Electrical Engineering, College of Engineering Spring 2014 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. The rated power of the presented system is increased by a factor of 10 compared to the actual satellite power system. The power generation is achieved by using 120W PV module. Later, the power is stored in a rechargeable battery. Three different converters are used to regulate the output voltages to match the loads requirements. To assure having a regulated voltage levels, a feedback control mechanism is also provided. In order, to control the conditioning converters a full detailed model was derived using state space technique.  The model is used later, to design the controller. An adaptive maximum power point tracking algorithm is introduced and implemented practically. Finally the efficiency of the Cubesat is calculated at three different cases that represent the real situations that the satellite will operate at. Introduction Practical Result Converters parameters • 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 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. Figure 6. The overall system implementation result Figure 3. Oscilloscope result of the MPPT with adaptive perturb (transient) Conclusion Computer Simulation The power supply architecture of the Cubesat was designed. The power is captured by solar panels and conditioned through power converters. The converters regulate the voltage based on the satellite subsystems requirements. To extract the maximum power from the panels, a maximum power point tracking controller based on the Perturb and Observe algorithm was simulated and implemented practically. An enhancement to the algorithm was introduced by including an adaptive term to the algorithm. The power converters were modeled using the state space representation, and then a control strategy based on the state feedback control technique was proposed. Finally, the efficiency of the system was evaluated. The overall Cubesat power system is simulated using MATLAB/Simulink. The model is shown in figure 2. Figure 4. open loop steady-state output voltage of the buck converter number (2) Future work As a future work the same system has to be implemented based on the real standard size of the Cubesat power supply at which the engineering satellite phase shall be terminated. In the satellite, some loads do not require to be supplied permanently. Those loads can be disconnected during that time. A triple junction model of a PV panel shall be derived to test the behavior of the purchased PV module and its performance with the proposed MPPT algorithm. An over-current protection strategy has to be added to the system in addition to battery over -charge protection strategy. Figure 5. closed loop transient output voltage of the buck converter number (2) System Overview Experimental setup The system configuration for the On-Board Electric Power Supply System (OBEPSS) can be well visualized as illustrated in figure 1 Figure 2. Simulink model of the power supply DSP Programming code PV Panel Simulink code MPPT Converter Acknowledgements Power Conditioning Converters Current, Voltage sensors and the DSP The authors would like to thank their supervisors Dr. Ahmed Massoud and Dr. Tamer Khattab and the Department of Electrical Engineering in Qatar University. In addition, the authors would like to express their gratitude toward both Eng. Mohammed Ayad and Eng. Ayman Ammar for their extensive support . Battery Loads Figure 1: The Hardware Overview Configuration of the power supply of the Cubesat