Reframing the Balance Challenge in Power Systems: Beyond Legacy Paradigms for the Energy Transition

The energy transition is fundamentally reshaping power systems through the rapid integration of variable renewable generation, inverter-based resources, energy storage, and flexible demand. These changes challenge not only conventional operational practices and performance indicators, but also the analytical abstractions and hierarchical decision structures developed for synchronous-machine-dominated systems. This paper revisits the balance challenge as an overarching problem involving the ability of power systems to establish, maintain, and recover feasible operating conditions across multiple timescales, locations, uncertainties, and disturbances. Building on a critical review of long-term planning, resource adequacy, operational scheduling, real-time control, and dynamic security, the paper identifies growing inconsistencies between analytical domains and discusses the need for greater cross-timescale coherence. The Chilean power system, characterized by rapid renewable integration and evolving technical and regulatory requirements, is used to illustrate these challenges through concrete planning and operational experiences. Rather than proposing a universal modeling solution, the paper outlines a conceptual foundation and implementation strategies emphasizing technology-agnostic performance requirements, multiscale modeling, uncertainty assessment, model interoperability, interdisciplinary collaboration, and experimental and regulatory validation. The proposed perspective highlights the need to continuously reassess analytical methods and standards in light of technological change, supporting more reliable, economically efficient, and sustainable power system transitions.