Increased frequency and voltage interactions affecting frequency and transient stability in networks with large penetration of renewable generation

The paper investigates the frequency and voltage dynamics and stability in power systems with increased penetration of inverter-based renewable energy sources (RES). The case studies presented within the paper show that the frequency dynamics (frequency nadir and rate of change of frequency) is not only affected by the decrease in system inertia but also by increasing frequency/voltage interactions when the proportion of RES exceeds that of synchronous generation. Furthermore, the critical fault clearing Time (CCT) analysis for transient stability indicates that RES fault ride through (FRT) and their settings can have a significant impact on the nearby generators. The studies also demonstrate that voltage and frequency interactions can be reduced and transient stability of synchronous generators improved by applying dynamic voltage support in weak areas of the system