Optimal CCGT ramp-up strategies for power system flexibility and stability based on a combined power quality index

This paper investigates the critical impact of the active power ramp rate on the dynamic stability of integrated 220/110 kV power grids. Based on a comprehensive series of simulations across diverse loading scenarios (1500–1800 MW) and short-circuit levels (5000–10000 MVA), the physical mechanisms governing the system’s transition into asynchronous operation were identified. The results establish that under reduced grid stiffness (5000 MVA), the critical ramp rate threshold is 21 MW/min. Exceeding this limit triggers an avalanche-like surge in the Rate of Change of Frequency (RoCoF) beyond 0.1 Hz/s, accompanied by severe voltage sags. The scientific novelty of this study lies in the development of a Combined Power Quality Index (CPQI), which synthesizes voltage and frequency dynamics. Verification via heat mapping confirms the index’s effectiveness as a predictive diagnostic tool for contingency analysis, enabling the clear differentiation between secure operating regions and critical bifurcation points.