Download H2O Power Supply Upgrades

Power System for
Ocean Bottom Observatories
Taken from the
Cabled Observatory Presentation
School of Ocean and Earth Science and Technology
February 2006
The Plan
• The Supply should be SCALABLE.
• There should be redundancy wherever
practical.
• High voltage converters present serious
reliability concerns.
• Low voltage converters can be stacked to
achieve both scaling and high reliability.
HV Power Distribution
• Start with High Voltage Distribution.
– Line losses go down with square of voltage.
• Step it down with fixed-ratio transformers.
– This is the main power conversion.
– Keep complexity to a minimum.
• Do any necessary regulation at low
voltage.
– Wide-range COTS regulators available.
– Voltage variations will be well within range.
– Use REDUNDANT regulators.
Limited Current Power Distribution
• Design power modules for nominal
current.
• Stack more converter for higher power.
– This increases primary voltage and secondary
current.
– The secondary voltage remains the same.
• The size of the voltage drop then
determines your available power.
Simplified POWER SUPPLY Stack
Incremental Failure Tolerance
(8-converter stack)
• If any one power converter module fails:
– The step-down ratio changes by 8/7.
– There is 14% increase in secondary voltage.
– The regulators can easily handle that.
• If two power converters fail:
– There is 33% increase in secondary voltage.
– This is still within the regulation range.
• Available power decreases slightly, but
system remains fully functional.
Redundancy
• The previous slide suggests a scheme for
redundancy:
– Extra converters can placed on the stack.
– Simply shorting the input removes them from
active duty.
– They can be brought on line as needed to
replace a failed unit or to increase power
capacity.
– Very minimal circuitry is required to
implement.
Power Supply Control
• Simple Rabbit 3000 microcontroller.
• Isolated voltage-to-frequency converters
monitor all significant voltages.
• Isolated Magnetoresistive-effect sensors
used for currents.
• Thermistor probes for temperatures.
• Backplane used for modular power
converters.
Rabbit 3000 Controllers
Power Module Backplane
Converter Modules
Testing
• Use a variety of fully dynamic loads.
• Use continuous maximum cycling with
pseudo-random pattern generator to
simulate every possible static and
transient load condition.
Dynamic Test Load
Dynamic Load Testing
Conclusions…
• This Second Generation Power Supply
has greatly expanded operating margins.
• Modular design allows for easy testing and
easy maintenance.
• The pseudo-random test load tests for a
wide range of operating conditions.
Conclusions…
• The power system is multiple-fault tolerant
in the critical areas and has very few
single-point failure modes.
• Rigorous system testing will weed out
infant-mortality and rare-event failures.
Discussion
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Design development
System power
Data Communication
System Control
Proof Module