System Strength Boundaries for High-IBR Grids

Abstract

With the increasing concern of greenhouse gas emissions and its effect on global warming, the electric power grid is experiencing a transformation with generation sources and their underlying characteristics. This transformation is the retirement of synchronous generation powered by fossil fuels in favor of renewable generation sources that emit fewer greenhouse gases to the earth’s atmosphere. These renewable generation sources, also known as inverter-based resources (IBRs), exhibit characteristics that are dissimilar to those presented by traditional synchronous generation sources. This difference has a conspicuous effect on power system strength and stability, which in turn will influence the performance of transmission line protection. Short-circuit strength measurements like short-circuit ratio (SCR) were created to quantify voltage stability at a specific point where a generation source with a converter would interconnect with the grid. Due to the intermittent availability of IBRs and electrical interaction between clusters of IBRs located nearby, these same metrics are inadequate with high penetration of IBRs on the power system. A new system strength analysis method must be established to account for these differences. This thesis addresses this critical gap by first analyzing the limitations of traditional Short-Circuit Ratio (SCR) based metrics in IBR-dominated systems. Employing short-circuit modeling software ASPEN, this research establishes a novel metric for defining the electrical boundaries of high-IBR penetration areas. Finally, the thesis demonstrates that this boundary significantly reduces the performance and reliable operation of transmission line protection, thereby providing a robust tool for system planning and operation.