2-D Coaxial Integration of Medium Voltage Power Electronics Enabled by Field-Driven Design

Abstract

The looming transformation of today's electrical infrastructure will require engineers and grid operators to pursue new technologies that are more resilient, adaptable, distributed, and efficient. Increased power demand from electrified transportation and multi-MW datacenters, in combination with higher generation volatility due to distributed energy resources continue to strain the electrical grid both domestically and abroad. Power electronics engineers continue to innovate, developing technologies to reliably integrate renewable generation and energy storage, enable efficient high-voltage dc transmission, and facilitate distributed, bidirectional power flow control. Despite these technological advances, a significant bottleneck remains: the time required to deploy critical distribution infrastructure is on the order of years. This is especially true in dense urban environments where the installation of a distribution-level substation can take as long as 10 years, resulting in power demand which quickly outpaces the supply, throttling growth. To enable the grid of tomorrow, it is crucial to improve the utilization and capacity of the existing infrastructure, while continuing to expand. To that end, this work proposes a radically new integration concept for power electronics with the goal of enabling a transformative increase in power density to facilitate the rapid deployment of critical infrastructure. This dissertation will explore the possibility of integrating medium-voltage power electronics directly in line with the cable, to create an intelligent cable splice. The intelligent cable splice concept combines the functionality and flexibility of modern power electronics with the coaxial form factor of medium-voltage cables, allowing medium- and low-voltage lines to be spliced together, with seamless, bidirectional power conversion embedded in the cable. The goal of this work is to explore the cable-integrated design space and determine the extent to which cable-like properties such as voltage scaling and passive cooling, can be inherited in the power electronics design. The analysis begins at the physics level, reconciling the electrical, thermal, and mechanical fields of the converter with that of the cable. The insulation performance of the integrated converter is compared to current practice through the use of a scaling factor, which quantifies the potential size reduction of coaxial integration. The limitations of passive cooling in a cable-like form factor are derived, and the findings inform the design of a passive cooling solution, allowing the intelligent cable splice to be deployed in existing underground cable vaults without the overhead of active cooling resources.