<p>Amidst global efforts to achieve carbon neutrality, the large-scale integration of renewable energy into power grids has highlighted the critical challenge of long-duration power imbalances, stemming from the inherent variability of renewable sources over extended periods and posing significant threats to grid stability. This paper provides a comprehensive review of current research on addressing long-duration balance in renewable-dominated power systems, identifying key challenges in the stochastic long-term fluctuations of renewable energy generation and strategies to mitigate these imbalances. To address these challenges, we propose a comprehensive research framework encompassing four dimensions: modeling and analysis of long-duration uncertainties in renewable energy; development of a unified methodology for modeling Long-Duration Energy Storage (LDES) in power system planning; simulation of power system operations considering long-duration balance; and strategic integration of long-duration flexibility resources into optimization and planning processes. Each of these domains is examined in depth, providing detailed insights into their critical research components. By addressing the key challenges and proposing actionable solutions, this study provides a systematic foundation for advancing long-duration balance in renewable-dominated power systems, contributing to the sustainable and reliable operation of future energy infrastructures.</p>