Power System for Ocean Bottom Observatories

Taken from the

Cabled Observatory PresentationSchool 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

• Design development

• System power

• Data Communication

• System Control

• Proof Module