Long-Term Energy Transition Scenarios in Weakly Interconnected Countries: Implications for Frequency Stability and Reserve Requirements

The global energy transition, driven by the Sustainable Development Goals and commitments to decarbonization, is transforming power systems with a rapid shift towards renewable energy sources. While this transition offers environmental and economic benefits, it poses significant operational challenges, particularly in maintaining frequency stability and ensuring adequate reserves. This study addresses these challenges, focusing on countries with vast renewable energy potential but isolated or weakly interconnected power systems prone to frequency instability. Presenting Bolivia as a notable case study in the global south, this research harmonizes and adapts longterm energy planning scenarios for 2050, derived from energy planning framework developed with Energy System Optimization Models, as inputs to an energy model aimed at Unit Commitment and Optimal Dispatch. This work integrates a multisectoral long-term planning perspective with detailed temporal and spatial resolution analysis that includes operational constraints to evaluate system stability and reserve requirements. The methodology involves an exogenous stability analysis to quantify system inertia response, fast frequency reserve, and primary frequency reserve needs, based on the (n-1) contingency criterion. For Bolivia, the dispatch results shows the largest contingency at 400 MW. In the long-term planning scenarios projected for 2050, the total amount of system inertia available relative to the overall size of the power system is expected to be significantly lower than in 2022, reflecting the decommissioning of fossil fuel power plants and the increasing penetration of renewable energy sources. This decline necessitates different balancing services to maintain frequency stability. The study highlights that appropriate reserve sizing is crucial for maintaining stability under low-inertia conditions. In the case study, reserves are adequately sized. Fast frequency reserve requirements range from 60 MW to 454 MW, while the available capacity from BESS averages between 321 MW and 1133 MW. Similarly, primary frequency reserve requirements range from 43 MW to 105 MW, while the available capacity from committed generators providing this service averages between 87 MW and 116 MW. These findings underscore the dependency of reserve availability on the dispatch of flexible generation resources. By bridging long-term energy planning with operational-level analysis, this study offers a replicable framework for evaluating system stability and reserve needs in future power systems, particularly for developing countries navigating the transition to resilient, low-carbon energy systems.