Post on 25-Jun-2020
Max Power Point Tracking System
Andres Lopez Sco: Palo, Andrew Dahir, Nicholas
Rainville
This work was supported by the NaDonal Science FoundaDon REU Grant No. 1157020 to the University of Colorado.
QB-‐50 Project • QB-‐50 is a project led by the Von Karman InsDtute of Fluid Dynamics that is a part of the European Union FP7 program.
• 50 cubesat constellaDon with each carrying one of 4 different scienDfic instruments.
• Deployment alDtude of ~380 km (ISS) • Deorbit with in 9-‐12 months. • The constellaDon will yield distributed measurements of the lower-‐thermosphere.
QB-‐50 Challenger • Challenger carries an Ion-‐Neutral Mass Spectrometer (INMS). Built by University College London. – Measures abundance of Oxygen, Nitrogen, and Nitric Oxide.
• Challenger carries heritage from CSSWE and MinXSS. QB-‐50 Challenger with PV
array deployed and prototype INMS structure
MoDvaDon • OpDmize power output of PV array.
– Output of 16.5 V at 460 mA on Earth in full sunlight.
• Prevent brown-‐outs – Pull more power from PV array than the amount it can provide (excessive load).
MPPT Theory • Output voltage and current of solar cells can vary due to environmental condiDons. – Temperature, internal resistance, solar irradiance
• Regulate the PV array voltage and current to where power supplied to the load is the greatest.
MPPT Algorithm • Constant Voltage
Constant Voltage Method • Power is interrupted. Voc with zero current is measured. OperaDon is resumed with the output voltage at a fixed raDo(.76) of the measured Voc.
• Pros – Simplest – Least ComputaDonal
• Cons – 76% is good approximaDon but someDmes does not coincide with the MPP
Hardware • PV Array • Voltage/Current Sensor (TI INA3221)
• Buck Converter (TI TPS5420)
• Li-‐Ion Ba:eries QB-‐50 Challenger Deployed PV array
Voltage and Current Sensing • Triple Channel Voltage/Current Monitor (TI INA3221) – CommunicaDon over I2C interface.
TI INA3221 Example ApplicaDon
DC-‐DC Regulator • Boost/Buck Converter
– Increase/Decrease Voltage • Buck Converter (TI TPS5420) – Vin Min: 5.5 V – Vin Max: 36 V – Iout Max: 2 A conDnuous (3 A Peak)
– Switching frequency: 500 kHz (500,000/sec)
TI TPS 5420 FuncDonal Block Diagram
Microcontroller • Arduino (ATmega328P)
– Controls ba:ery-‐charging circuitry (DC-‐DC Regulator)
– Reads sensor values over I2C.
– Monitors system performance (I/V from PV array and ba:eries)
Arduinos communicaDng voltage values over I2C
ATmega328P
PV Array
TPS5420
INA3221
Ba:eries
I2C
Power
Data
Outcomes/Future Work • Device built from spare Electrical Power System (EPS) Board.
• Preliminary TesDng • Device will exit prototype phase. Finalized, it will be implemented on future cubesats.
Prototype of Device
QuesDons?