Ground Fault Overvoltage Analysis of Submarine-Fed IBR-Dominated Networked Microgrids

Nowadays research in the areas of power system resilience and renewable energy resources have been progressing at unprecedented pace. This reflects the current focus of Energy Justice and creates an environment suitable for augmenting electricity service to vulnerable communities. One the one hand, resilience strategies often result in reinforcing or rebuilding portions of a power system network, whereas on the other this represents an opportunity to develop a system to become ready to house larger amounts of renewable energy and by extension microgrids, which can further increase resiliency. This is particularly important in grid-edge systems that are highly dependent on supplies that lack redundancy. This paper addresses the legacy issue of effective grounding, as a grid edge supply is improved in a system where the system operator is building two networked microgrids in two small islands supplied by submarine cables. This is the first system-of-systems of its kind and the farthest from a main grid where the only interconnection is through such vulnerable supply, which by way of construction inherently is ineffectively grounded, making the system prone to temporary overvoltages. In this work, the author analyzes the problem by providing an analytical overview of temporary overvoltage management. The paper proposes mitigating these interconnection issues by using neutral grounding elements connected to coupling transformers and analyzing requirements for inverter negative-sequence current injection to ground faults.