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 Design development System power Data Communication System Control Proof Module