Towards to larger capacity of EPS for CubeSat: Experience from star of aoxiang and issues for future development

As a highly critical component in CubeSat, electrical power system (EPS) is responsible for harvesting, converting and controlling the satellite's energy. Traditional EPS with a power capacity of several or dozens of watts has already been unable of meeting the needs of many practical CubeSats with more complex functions and longer life. In this paper we analyse the power budgeting of Star of Aoxiang (SAX), the world's first 12U CubeSat launched into space, and present the design and implement of its EPS: MPPT based PV power converter, battery charge/discharge controller, multichannel DC-DC regulator, power distribution switches with protection, and monitoring circuitry based on a low-power MCU. Additionally, we discuss the results of on-orbit experiments of the EPS. The analysis presented is helpful to verify the functionality and reliability of the EPS. To satisfy larger power demands of CubeSat in the near future, EPS with more power handling capacity is becoming an imperative requirement. Based on the flight experience gained from SAX, an advanced power system scheme is proposed with power handling capacity of hundreds of watts for CubeSats. The EPS scheme is featured by modularity, standardization, flexible of configuration, high efficiency, fault-tolerant, and use of Commercial off-the-shelf (COTS) components. The utility of standard modular multi-distributed converters is promising to maximize the power harvested from the optimized distributed deployable solar arrays. The designed EPS can provide a reliable and efficient solution to supply power to the subsystems of CubeSats. It will remain functioning properly in case that failure occurs in some parts of the solar arrays or power converters.