With the increase in inverter-based resources, maintaining system stability has made frequency maintenance criteria an important factor. In South Korea, there are two frequency maintenance criteria for N-1 and N-2 contingency faults, and consistency between these criteria is necessary to ensure the rational use of limited frequency response resources. This article proposes a method to verify the consistency of the criteria based on the minimum inertia in the system. The proposed methodology has the following salient features: i) developing a methodology to verify consistency between criteria based on minimum system inertia, ii) identifying the inconsistency in South Korea's existing frequency maintenance criteria and the need for their revision, iii) evaluating the impact of inconsistent frequency maintenance criteria on non-synchronous generation and system non-synchronous penetration. The methodology was validated on the IEEE 39 bus test system and applied to 7040 hourly operational data from the energy management system of the South Korean to verify the differences in criteria. The main result is that the two frequency maintenance criteria are inconsistent, require more frequency response resources in the N-1 criterion. The findings provide practical implications for system planners and operators, highlighting the need for frequency maintenance criteria revision in South Korea.

Managing the output of renewable energy sources considering their uncertainty and variability is crucial for resilience in power system operation. In addition, analyzing stability issues that may arise at the maximum output is important to ensure power system stability. Therefore, the authors propose a method for estimating the maximum non‐synchronous generation (Max NSG) of renewable energy based on the minimum inertia of the power system. The minimum inertia is determined through the correlation between the available and required quantity of inertia and governor resources, satisfying the frequency standards in a South Korean power system. The Max NSG of renewable energy sources at that system inertia level is estimated based on the derived minimum inertia. The proposed method was applied to 22,612 operation data extracted from the Korea energy management system (K‐EMS). The authors estimated a linear relationship between demand levels and Max NSG, ranging from 52.6 to 3.83 GW. The study shows that Max NSG, which is difficult to estimate in many power system operating conditions, can be estimated based on minimum inertia considering the frequency stability in South Korean power systems.

In low-inertia systems with a high penetration of renewable energy, the rotational kinetic energy and inertia constant are significant factors in determining frequency stability. The energy released owing to the frequency decrease during contingency represents a portion of the inertia that a synchronous machine possesses in the normal state. However, when securing inertia or planning additional resources to secure frequency stability, inertia in the normal state is analyzed as the standard rather than the amount of energy released during a fault. Therefore, in this paper, we define the actual energy emitted from a synchronous machine as Effective inertia. In order to evaluate Effective inertia in various operating conditions, we conducted a comprehensive review on approximately 24,627 cases from the years 2019, 2020, and 2021. As a result, in systems with low rotational kinetic energy, both low- and high-frequency nadirs were observed, indicating high uncertainty. However, Effective inertia presented a consistent trend regarding the energy release aligned with the minimum frequency. For instance, the rotational kinetic energy required to satisfy the frequency standard was 23 GWs, while the required Effective inertia was 858 MWs. We emphasize that securing inertia based on rotational kinetic energy includes additional imaginary energy that does not contribute to frequency, resulting in an energy requirement greater than that needed for Effective inertia. Therefore, in order to secure the frequency stability of the future system, the actual required energy amount based on Effective inertia will be presented and utilized in the inertia market and FFR (Fast Frequency Response) resource design.

As power systems shift toward inverter-based resources (IBRs), maintaining stability depends on both total available inertia and system strength. This paper addresses frequency security by determining the required frequency response reserves (FRR) as an explicit function of the short-circuit capacity (SCC) at the renewable interconnection bus. For a fixed contingency, lower SCC at the connection point increases the required FRR and raises the secure operating level of inertia (SOLI); conversely, higher SCC reduces both for the same event. We show that, for a fixed contingency and nadir standard, lower local SCC at the renewable interconnection bus systematically increases both the required FRR and the SOLI. This SCC–FRR formulation enables system operators to set region-specific FRR targets and to assess the impact of renewable siting in weak versus strong areas without changing the underlying frequency-security standard. We substantiate this with a regional analysis on KEPCO’s system, using data-driven operating snapshots and dynamic frequency simulations for three areas with different SCC and renewable siting patterns. The results reveal local system strength differences across areas and demonstrate that relocating renewable connections alters FRR needs and shifts SOLI in proportion to local SCC. Jeonnam needs approximately 14–23% higher SOLI and 28–45% more FRR than other areas under the same nadir criterion.