Grid Stability Risks Under High Penetration of Renewable Energy

The increasing penetration of renewable energy fundamentally alters the structural and dynamic properties of modern power systems. As inverter-based generation replaces synchronous machines, traditional assumptions regarding inertia, control hierarchy, and network behavior become less reliable. This paper examines grid stability risks under high renewable penetration from a non-empirical, system-oriented perspective. Rather than focusing on specific technologies or case studies, the analysis explores how structural transformation, control interaction, and system coupling reshape the conditions under which stability is maintained. The paper discusses key risk mechanisms related to low-inertia frequency dynamics, voltage behavior in inverter-dominated networks, and the interaction of heterogeneous control strategies. It further examines how coupling among frequency, voltage, network structure, and control logic can amplify local disturbances into system-wide stability challenges. By situating these risks within the broader context of the energy transition, the paper argues that instability should be understood as a structural feature of transitional power systems rather than as an exceptional failure. The analysis highlights the limitations of component-level optimization and emphasizes the need for flexibility, coordination, and adaptive design at the system level. This conceptual approach provides a framework for understanding grid stability as an emergent system property in renewable-dominated power systems.