Design and validation of modular MPPT electric power system for multi-U CubeSat

To meet the power demand for multi-U CubeSat from 1U up to 20U, a kind of innovative modular electric power system(EPS) is designed and verified. The system can convert three independent photovoltaic power inputs with each channel up to 40Watts, and the maximum power point (MPP) for each channel can be set independently by hardware. The solar power is converted and stored in lithium-ion batteries. Using a high efficiency charge controller, the battery voltage is maintained between 6.5V to 8.4V. Two buck-converters are applied to change the battery power to 5V and 3.3V to supply other subsystems with 5A maximum current. A TI MPS430 ultralow power microcontroller is used to monitor the system status, switch the power outputs and communicate with onboard computer via I2C. The proposed EPS has already been applied in Aoxiang ZhiXing(Aoxiang-Sat), the world's first 12U scientific CubeSat, which is launched on June 25, 2016. The telemetry data shows that the power produced by EPS is abundant for the satellite, and it worked with excellent performance during the satellite lifetime.