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Satellite Electrical Power System (EPS) Design Review

Satellite Electrical Power System (EPS) Design Review. Hayden Waddle Joshua Stogsdill Stephen Maloney Travis McCullar. Abstract. The EPS system will be responsible for several functions including Boosting input voltages from panels Regulating battery charging and bus voltages

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Satellite Electrical Power System (EPS) Design Review

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  1. Satellite Electrical Power System (EPS)Design Review Hayden Waddle Joshua Stogsdill Stephen Maloney Travis McCullar

  2. Abstract • The EPS system will be responsible for several functions including • Boosting input voltages from panels • Regulating battery charging and bus voltages • Sending telemetry to main controller • Commercially available systems - Clyde Space • More features, greater protection • Include same major functions (Voltage regulation, battery charge routines, temperature monitoring)

  3. Current Status : Problem Simplification • Simplified Design • Gain traction on building a working prototype by reducing requirements to manageable levels • Add complexity after simplified design is constructed and tested VBat 5V Regulator Solar Panels In Parallel Boost Converter Battery Charger Lithium Polymer Batteries 5V 3.3V Regulator 3.3V Battery Heating System

  4. Boost Converter and Voltage Regulation • Boost Converter • Solar cells provide 4 - 8 V • Battery Charger requires 8.4 - 12V • Boost converter raps input voltage to a constant 12 V • Voltage Regulation • Current testing - linear voltage regulators. • Production - more efficient switching regulators.

  5. Battery Charging • Battery Charger - MCP73864 • Self-contained Li-ion/Li-polymer charger. • Implements most efficient charge cycle. • Provides thermal limits for battery charging. • Batteries • Current testing - smaller scale Li-ion batteries. • Production - Li-polymer batterieswith capacity of greater than1240 mAh.

  6. Battery Heating • Battery Charger Thermal charging limits. • External heaters and control system • Battery mounted thermistors. • Control through: • Onboard microcontroller. • Main satellite microcontroller. • Heater options: • PCB Traces • Thin Film Heaters • Heat Tape

  7. Current Prototype Status • Purchased test boost converter, regulators, battery charger, PIC controller • Tested boost converter and regulators using DC source in lab; 1V->12V • Attempted test using solar panel with flashlight 12V 5V Regulator DC Source >1 V Boost Converter 5V 3.3V Regulator 3.3V

  8. Future Plans : Complexity Level 1 • Replace the boost converter with a peak power tracker • A peak power tracker provides a varying “load” to the outputs of the solar panels • This load specifies the operating point on the solar panel I-V curve • At the knee of this curve, maximum power output from the solar cells is achieved

  9. Future Plans : Complexity Level 1 • The peak power tracker varies the load efficiently by varying the duty cycle of a boost converter circuit • RIn = ROut(1-D)2 • In this way, energy is stored in the magnetic field of the inductor rather than wasted in a resistor

  10. Future Plans : Complexity Level 1 • Many methods for varying the duty cycle of the boost converter to find peak power exist, such as the “perturb and observe” method • Some assumptions required – if the satellite is spinning very quickly, control will be difficult or impossible Boost Converter Load V Solar Cell I D/A A/D Controller

  11. Future Plans : Complexity Level 2 • Separate the solar cell panels from their parallel configuration and use a peak power tracker for each panel • This will allow telemetry output of individual panel voltage/current (useful for determining orientation and spin rate) • Telemetry output for battery voltage and charge status • Over-current protection for VBatt

  12. Future Plans : Complexity Level 3 • Flight pin / footswitch integration • Temperature testing using a NASA weather balloon / Cryo-chamber • Battery coatings to prevent ballooning effect in space – Kapton coating • Design for satellites with more powerful solar panels to continue limited operation after battery death

  13. Current Budget

  14. Future Budget Near Future Budget Distant Future Budget *Price subject to change due to implementation design.

  15. Timeline

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