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The key part of any satellite for its proper function is the design of Electrical Power System (EPS) whose function is to provide required energy during normal as well as eclipse periods. The main function of EPS is to generate power from solar energy through solar panels mounted on the satellite surface to supply power to loads during normal period and the output voltage is regulated to charge the battery which is required to deliver energy during eclipse. This paper describes the modeling, simulation of a EPS for a Nano satellite in MATLAB Simulink environment.
Nano satellites are typically defined as artificial satellites with a mass between 2.2 and 22.0 lbs. Advances in technology have allowed for lower costs in manufacturing, miniaturization of components, and increased overall utility of technology . Nano satellite has a scientific payload attitude control system, communication system etc, with unique power requirements, therefore there is a need to design and develop a relatively low cost system to suit the operation requirements.
The Nano satellite considered for this simulation is a cuboid shaped and weighs approximately 4kgs which has body mounted solar panels on three sides of its six sides which are going to be deployed in the space. The other three sides are neglected because they will never face the sun or gets any illumination . One of its sides i.e. the nadir side contains the payload which is the objective of the Nano satellite.
Solar energy is the only source of energy in space and the operation of the entire satellite depends on this energy. The role of EPS is to generate, condition and distribute the electrical power to the satellite loads for their functioning . The EPS consists of solar panels which are connected in combination of series and parallel strings for generation. For storage, Li-ion batteries are connected to the bus which is charged during sunlit period and the energy stored is used during the eclipses . For this, power budgeting is to be done so that electronic converters are to be modelled to cater the required energy to various sections of the satellite .
The design process of any satellite sub-system strongly depends on orbital parameters such as the type of orbit, orbital height, inclination, time spent in the sun, time spent in eclipse, average orbits per day and average orbits for the extent of the mission etc. From these calculations, the key aspects which influence the size of the battery like number of charging, discharging cycles and depth of the discharge will be determined .
In this paper, a Nano satellite EPS is simulated and its output voltages are observed. The major role of this work is to model the EPS in the face of continuously changing power requirements. This means that the EPS could be potentially overdesigned if unnecessary parameters are included. The EPS components like solar panels, batteries and DC-DC converter are designed and simulated in MATLAB. The results obtained show that the power consumed by the loads is less than the power generated by the solar panels hence the Nano satellite EPS system is reliable.
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