Analyzing the Frequency Stability of the Timor Power System with High Penetration of Variable Renewable Energy

Sammanfattning

This thesis investigates the stability of the Timor power system under high penetration of Variable Renewable Energy (VRE) power plants. The study utilizes dynamic modeling and simulation to assess system performance and propose stability-enhancing strategies. This thesis analyzes the frequency stability of the Timor power system under high penetration of VRE, particularly photovoltaic (PV) and wind power plants. The study employs dynamic simulations using DIgSILENT PowerFactory, based on real data from PT PLN (Persero). Various operating scenarios are evaluated, including daytime with high renewable penetration and nighttime with lower penetration, under two types of disturbances: the tripping of the largest generating unit and a sudden load increase. The results indicate that high shares of VRE significantly increase the system’s vulnerability to frequency deviations due to the absence of inherent inertia. In several scenarios, the system frequency nadir fell below the first stage of under-frequency load shedding (UFLS), in the worst-case scenario, the system frequency falls to 47.89 Hz when VRE dominates the power generation mix. This condition highlighting the need for additional frequency support. The integration of Battery Energy Storage System (BESS) provides fast frequency respons (FFR), effectively mitigating frequency drops and keeping the system within operational limits. The required BESS capacity varies depending on the generation mix: approximately 25 MW during daytime coal-dominated operation, 10 MW with Gas Engine Power Plants (GEPP) online, and 5 MW at nighttime. Overall, the study demonstrates that while large-scale integration of PV and wind poses challenges to frequency stability, the deployment of appropriately sized BESS can ensure reliable and resilient system operation. The findings provide practical insights for PT PLN in planning and operating future renewable-based systems in Timor and contribute to Indonesia’s energy transition and sustainability goals.