Resilient Transmission Grid Design: AC Relaxation vs. DC approximation
For power system planners, this work provides a framework to evaluate resilience investments and highlights the importance of using AC models over DC approximations for accurate resilience planning.
This paper develops a model and tractable methods for optimizing transmission grid upgrades to improve resilience against extreme weather and attacks, comparing AC power flow relaxations with DC approximations. Tests on the RTS-96 system show that AC relaxations provide more accurate resilience assessments than DC approximations.
As illustrated in recent years (Superstorm Sandy, the Northeast Ice Storm of 1998, etc.), extreme weather events pose an enormous threat to the electric power transmission systems and the associated socio-economic systems that depend on reliable delivery of electric power. Besides inevitable malfunction of power grid components, deliberate malicious attacks can cause high risks to the service. These threats motivate the need for approaches and methods that improve the resilience of power systems. In this paper, we develop a model and tractable methods for optimizing the upgrade of transmission systems through a combination of hardening existing components, adding redundant lines, switches, generators, and FACTS and phase-shifting devices. While many of these controllable components are included in traditional design (expansion planning) problems, we uniquely assess their benefits from a resiliency point of view. More importantly, perhaps, we evaluate the suitability of using state-of-the-art AC power flow relaxations versus the common DC approximation in resilience improvement studies. The resiliency model and algorithms are tested on a modified version of the RTS-96 (single area) system.