Generation expansion planning: Transitioning toward decarbonization with a focus on reliability and Dunkelflaute

Modern power systems increasingly rely on variable renewable energy sources, supported by energy storage systems and gas power plants, to meet decarbonization targets. However, the high penetration of renewables introduces significant uncertainty due to their weather-dependent nature, posing challenges to system reliability. This paper proposes a probabilistic, multi-level generation expansion planning framework that integrates reliability assessments, with a particular emphasis on the role of energy storage systems. A novel probabilistic approach is also introduced to model the Dunkelflaute phenomenon and evaluate its impact on system reliability. Additionally, the study explores the influence of regulatory mechanisms — referred to as embedded system reliability schemes — on reliability outcomes. The proposed optimization model is tested on a modified IEEE Reliability Test System and validated through scenario-based simulations and sensitivity analyses. Results highlight the pivotal roles of reliability targets, storage system characteristics, and embedded reliability schemes in shaping reliable and cost-efficient expansion planning strategies. • This paper introduces a multi-level approach to generation expansion planning. • A novel probabilistic approach is utilized to model Dunkelflaute events. • This paper presents a scheme to defer investments while ensuring reliability.