The Definition of Effective Inertia and its Analysis on the Low Inertia System Connected via HVDC

This paper introduces the concept of “Effective Inertia,” which refers to the kinetic energy contributed by synchronous generators up to a specific frequency threshold. Additionally, the notion of “Critical Effective Inertia” is proposed, representing the energy required until the lowest point of frequency. By quantifying these energy values, it becomes possible to determine the additional energy needed to maintain frequency stability. However, when evaluating effective inertia, it is crucial to account for Fast Frequency Response (FFR) mechanisms, such as HVDC, as they possess distinct dynamic characteristics. To demonstrate the application of this concept, a case study of the Jeju power system in South Korea is presented, focusing on the analysis of effective inertia in a low inertia system connected via HVDC.