Steady-State and Dynamic Validation of Renewable Transition Pathways: An Automated PLEXOS-PSS/E Simulation Framework

Techno-economic planning identifies renewable generation, storage, and flexibility portfolios but cannot establish their AC-network feasibility or dynamic security. This study develops an automated Python framework coupling PLEXOS planning with steady-state and RMS dynamic assessment in PSS/E. Critical hourly operating conditions are transferred into network cases, tested against disturbances, and evaluated using voltage, frequency nadir, and rate of change of frequency (RoCoF). The framework is demonstrated across four systems (23–505 nodes) and successive renewable energy sources (RES) penetration stages. Across 144–256 screened PSS/E cases per system, the largest individual violation category affected 12.24–41.67% of cases, establishing a conservative minimum affected-case share and revealing technical limitations not represented in the upstream planning assessment, including AC-feasibility, voltage-recovery, and frequency-security limitations. Both benchmark systems exhibited their highest RoCoF near 75% RES rather than at maximum penetration; the IEEE 39-node case reached 1.87 Hz/s, while its lowest nadir occurred at 50% RES. Halving available fast frequency response increased peak RoCoF by 0.05–0.11 Hz/s and lowered nadir by 0.05–0.50 Hz. These findings show that critical transition stages depend on synchronous inertia, network flows, operating conditions, and flexibility deployment. The framework also identifies actionable requirements, including regional voltage support and transmission reinforcement, for subsequent long-term planning.