Maximizing Flexibility and Efficacy of Undersea Wireless Power Transfer Systems

Abstract

Autonomous underwater vehicles (AUVs) are an ever-increasingly essential tool for ocean-based applications, whether it be scientifically, economically, or militarily. To advance the capabilities of AUVs, it is crucial to improve the mission time and length of these vehicles. One proposed way to achieve this is with remote undersea wireless power transfer (WPT) systems to allow AUV charging from remote areas of the ocean floor. While there has been significant research in WPT system design, these projects often tailor the design specifications towards a specific AUV shape, size, or power requirement. These point designs have wildly different power outputs, efficiencies, coupling coefficients, sizes, and more, making it difficult to understand how the design parameters affect each of these properties. This paper aims to address this knowledge gap in current undersea WPT systems by designing an equivalent circuit framework for a WPT system with a targeted power output of ~1 kW to show how design parameters such as input voltage, coil size, transfer gap, coupling coefficient, and load resistance affect the power output and efficiency of the charger. Furthermore, the effects of misalignment in vertical and lateral directions for two separate compensation networks – series-series (SS) and series-parallel (SP) – are compared to determine which compensation network would perform best under specified circumstances. The paper then addresses the losses associated with a conductive environment by coupling the circuit model with an electric field model in seawater. The impact of undersea losses on system metrics is quantified, showing a 3% decrease in efficiency as compared to in air. Finally, the study investigates the use of magnetic cores in WPT systems for EM shielding and field-shaping characteristics. A design methodology is introduced to rank material properties based on the desired system performance characteristics. Suggested materials are then chosen according to this ranking and tested using the models derived in the study. By mapping both electrical and magnetic-core design spaces in a conductive seawater environment, this thesis delivers a unified methodology for designing scalable, efficient undersea wireless chargers.