Integrating Lithium Polymer Charging and Peak Power Tracking on a CubeSat Class Satellite

Every satellite must regulate incoming power from solar cells, charge batteries and regulate satellite power to maintain satellite health. The power system should be as light, small, and efficient as possible to allow a maximum of resources to satellite systems while minimizing complexity, and meeting CubeSat mechanical and thermal requirements. This paper describes a modular power system, which integrates peak power tracking, battery charging, and power regulation. In addition, it describes the entire power design of a CubeSat power system. This system includes the modular power system described above together with solar cells, and lithium polymer batteries. Due to a limited budget and limited efficiency of solar cells, there is very little power to supply the satellite. Therefore, the power system achieves good efficiency and low mass/volume by implementing a bang-bang peak power tracking system with integrated battery charging. This system will use a PWM buck-boost converter to control the current drawn from the solar cells as well as regulate the charging of the lithium polymer batteries. A micro-controller tracks the feedback from the peak power / charging system and adjusts the regulator accordingly. In addition to the peak power tracker, a power management scheme insures longer operating periods and a reliable downlink transmission. This design results in a highly integrated power system