Analytical methods for power monitoring and control in an underwater observatory

The study of the undersea environment requires the use of scientific instruments at the bottom of the ocean and in the water column to collect useful data. The traditional methods of conducting such studies by sending ships or using bottom instruments and moorings are not able to provide the necessary data over a long period of time due to weather and energy limitations. The objective of the North Eastern Pacific Time-Series Undersea Networked Experiment (NEPTUNE) program is to construct an underwater cabled observatory on the seafloor of the northeast Pacific Ocean off the coast of Washington, Oregon, and British Columbia, encompassing the Juan de Fuca Tectonic Plate. This system features over a few dozens of science nodes for the connection of scientific instruments that enhance our ability to conduct continuous ocean studies in this region. This dissertation investigates important design and implementation issues of the NEPTUNE power system.; The power system associated with the proposed observatory is unlike conventional terrestrial power systems in many ways due to the unique operating conditions of underwater cabled observatories including the high reliability requirements and low observability and controllability. These unique aspects of the NEPTUNE system lead to the development of new hardware and software applications that will provide an essential and efficient operation environment. In this dissertation, the solutions to some of the technical problems are proposed.; The design of the Power Monitoring and Control System (PMACS) allows PMACS to function in a similar way that Supervisory Control and Data Acquisition (SCADA) and Energy Management Systems (EMS) are used to monitor and control terrestrial systems. A Fault Location algorithm is developed to identify a backbone cable fault by solving nonlinear equations with only shore station measurements. The same approach can be applied to underground power systems. In order to handle the request from the science users to turn their loads on and off, a Load Management algorithm is proposed based on nonlinear optimization. This algorithm takes into account the different priorities of science node loads. The PMACS EMS modules require different parameters in the system model to provide accurate results. The effect of cable resistance variation due to the temperature of the seawater is investigated and an algorithm is developed for PMACS to update the resistance values using a quadratic programming technique.; The algorithms developed in this research addresses challenges and difficulties for an underwater observatory system. The results presented in this dissertation should be applicable to similar underwater systems in the future.