Geographically distributed simulations (GDS) overcome the inherent limitations in capabilities of single research infrastructure to accurately represent large-scale complex power and energy systems within representative operating environments in real-time. The feasibility of GDS has been proven, however, there is a lack of confidence in its adoption owing to limited evidence of its stability and accuracy that ascertain its practical applicability. This paper presents detailed small signal stability models for GDS setups with two interface signals transformations. The models have been validated by empirical analysis and used for determining the boundaries for stable operation of GDS setups. For the common region of stability of the two transformations considered, accuracy analysis presented offers insights for their selection. This advancement, thereby, enables realisation of experimental setups that can cater for the growing need to design and validate operational schemes that ensure robust and resilient operation of critical national infrastructure.Index Terms-Accuracy, geographically distributed simulations (GDS), power hardware-in-the-loop (PHIL), stability.
I. INTRODUCTIONH ARDWARE-in-the-loop has proven to be a valuable approach to accelerate the validation and deployment of novel technologies, with an increasing number of laboratories across the world adopting the approach [1]. The rapidly increasing complexity of power and energy systems (due to increased decentralization, decarbonization and digitalization) presents a challenge for single research laboratories, as existing capabilities (computational, expertise or equipment) will have to expand to encapsulate the growing complexity to ensure rigorous validation and roll-out of novel technologies at pace. This has encouraged the development and establishment of the concept of geographically distributed simulations (GDS), allowing for complementary expertise, additional equipment, domains and computational resources to be