Time-domain stability analysis of mixed generation electric power system subject to severe disturbance: Test of control parameter adjustments for increased renewable energy penetration

Power systems with high penetration of inverter-based generation face severe stability challenges due to reduced inertia and altered transient behavior during disturbances. Addressing these challenges is crucial to ensure reliable operation in the ongoing energy transition. In this study, a detailed mixed-generation system composed of synchronous machines and inverter-based generators is modeled and analyzed under severe disturbances using Time-Domain Simulation (TDS). The proposed framework systematically tests combinations of physical and control parameter adjustments – such as system inertia, power controller gains, phase-locked loop (PLL) gains, and power reference control – to identify the mechanisms that enhance transient stability at various renewable penetration levels. Unlike previous studies that rely on simplified linear or small-signal models, this work employs high-fidelity nonlinear dynamic modeling implemented in DIgSILENT PowerFactory, enabling quantitative assessment of stability boundaries for renewable shares ranging from 10% to 90%. The results demonstrate how coordinated parameter tuning can increase the maximum stable renewable penetration while maintaining system robustness. This study provides practical insights for grid operators and researchers by linking each renewable penetration level with the minimum parameter adjustments required to ensure transient stability in mixed-generation systems