Generation Expansion Planning in Isolated Power Systems: A Robust Approach With Dunkelflaute Assessment

Generation expansion planning is vital for decarbonizing power systems and ensuring a reliable and sustainable energy future. Strategically adding new generation and grid capacity is essential for supporting a seamless transition to renewable energy while reducing greenhouse gas emissions. However, achieving the optimal capacity mix of energy resources to ensure network reliability and economic efficiency presents significant challenges, particularly for isolated electricity grids. These challenges are exacerbated during periods of low renewable generation and due to the inherent intermittency of weather-dependent energy resources. This paper presents a comprehensive approach to optimizing long-term expansion planning for an isolated electricity grid, focusing on integrating renewable energy and storage systems. We investigate how intermittent and limited energy resources can meet a reserve capacity constraint as the determinant reliability measure. A novel scenario-based optimization model is introduced to guide capacity planning over a 10-year transition period. This model incorporates boundary constraints to optimize annual energy resource values and presents a novel assessment approach to address the challenges of Dunkelflaute events in capacity planning. The methodology is validated using a modified IEEE-RTS system alongside real-generation data from renewable resources. The robustness of the proposed approach is rigorously tested through extensive simulations and post-optimization sensitivity analyses. Our findings demonstrate quantitatively the critical impact of decision variables, including energy storage system duration and the annual penetration levels of renewable energy, on the overall effectiveness of the planning strategy.