There is a global focus on adding renewable energy sources to the mix of energy supplies. In this study, the grid connections for large-scale offshore wind farms in areas that have high penetration of renewable energy sources were examined. System strength evaluation considering the interaction of wind farms and inverter-based resources (IBRs) was performed; the fault current was then analyzed to determine their contribution to the total fault current at a bus level. These studies revealed that the interaction between offshore wind farms and IBRs may make the power system weaker, and it is possible that fault current contributions from offshore wind farms can violate the capacity limit of existing circuit breakers. The results of steady-state analysis were verified through case studies focused on the southwest area of the Korea Electric Power Corporation (KEPCO) system where large-scale offshore wind farms are planned to be established and connected. Power system planners will benefit from the results of this study with a better understanding of the factors to consider when integrating large-scale wind farms in areas with high penetration of renewables.

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.

This paper proposes a real-time oscillation monitoring framework based on an enhanced Geometric Feature Extraction (GFE) algorithm. The method utilizes high-resolution synchrophasor measurements from Phasor Measurement Units (PMUs) and employs a sliding window approach to identify oscillatory behavior in power systems. To improve detection robustness, the algorithm integrates signal-to-noise ratio (SNR) filtering and adaptive estimation of the Radius of Trajectory (RoT), which characterizes geometric patterns in reconstructed phase-space trajectories. A real-time alarming index is computed for each sample, and an oscillation alarm is triggered when the proportion of oscillatory samples within a window exceeds a predefined threshold. The proposed method was validated using actual PMU data recorded during a forced oscillation event caused by a Thyristor-Controlled Series Capacitor (TCSC) in the KEPCO power system. Experimental results demonstrate that the algorithm accurately captures the initiation, persistence, and attenuation of oscillatory behavior, offering both high detection sensitivity and low computational overhead suitable for real-time deployment.

The large-scale integration of renewable energy into modern power grids has led to a critical reduction in both system-wide rotational inertia and localized system strength. While previous studies have often analyzed these two factors in isolation, this paper observes their interdependent relationship. Specifically, this paper demonstrates the impact of short-circuit capacity (SCC) on system reserve requirements by quantifying the Frequency Regulating Reserve (FRR) volume necessary to satisfy frequency nadir criteria under the most severe contingency. This quantification is based on a comparative analysis of regional renewable energy deployment in the Korean power system. The simulation results reveal that the required FRR increases significantly when renewables are deployed in areas with low SCC. These findings highlight the potential hidden costs of interconnecting renewables in a weak grid area, particularly from the perspective of system inertia, underscoring the necessity of considering location-aware markets in future power systems.

The increasing interconnection of inverter-based resources (IBRs) with low short-circuit current has weakened grid strength, making phase-locked loops (PLLs) susceptible to instability due to accumulated phase-angle error under current limiting. This study defines such instability as IBR instability induced by reduced grid robustness and proposes a root-mean-square (RMS) model-based screening method. After fault clearance, the residual q-axis voltage observed by the PLL is treated as a disturbance signal and, using the PLL synchronization equations, is analyzed with a standard second-order formulation. The maximum phase angle at which synchronization fails is defined as ${\theta }_{peak}$, and the corresponding q-axis voltage is defined as $V_{q,crit}$. This value is then mapped to a screening metric $P_{peak}$ suitable for RMS-domain assessment. The proposed methodology is applied to the IEEE 39-bus test system: the stability boundary and $P_{peak}$ are obtained in Power System Simulator for Engineering (PSSE), and the results are validated through electromagnetic transient (EMT) simulations in PSCAD. The findings demonstrate that the RMS-based screening can effectively identify operating conditions that are prone to PLL instability in weak grids, providing a practical tool for planning and operation with high IBR penetration. This screening method supports power system planning for high-penetration inverter-based resources by identifying weak-grid locations that require EMT studies to ensure secure operation after grid faults.