Dr. Milan Prodanović

This talk examines the challenges associated with the ongoing decarbonisation of electricity systems and their role in the 2025 Iberian blackout. It opens with an overview of the Iberian power system’s structure and operational characteristics, covering network topology, interconnections with neighbouring systems, recent trends in electricity demand, the rapid growth of renewable energy penetration, and the regulatory and market frameworks governing system operation prior to the event. These contextual elements are essential for understanding the conditions under which the disturbance occurred. The presentation then analyses the sequence of events and underlying mechanisms that precipitated the blackout, with particular focus on system stability. As conventional synchronous generation is progressively displaced by inverter-based renewable resources, the dynamic behaviour of the grid changes substantially. Reduced system inertia, altered fault responses, and the distinct control characteristics of power electronic converters introduce new operational challenges for transmission system operators. Within this context, the talk explores how these evolving technical conditions may have contributed to system vulnerability, and examines the stability phenomena that can emerge in highly decarbonised power systems. Building on this analysis, the presentation addresses the key technical and regulatory requirements for the future transformation of electricity networks. Particular emphasis is placed on strategies to reinforce transmission infrastructure and enhance cross-border interconnections, thereby improving system robustness and flexibility. The declining contribution of synchronous machines—which traditionally provided inertia, voltage control, and other essential ancillary services—is also examined. Ensuring the continued provision of these services will be critical to maintaining stability and operational security in power systems increasingly dominated by inverter-based resources. The presentation further considers how to preserve the quality of grid services in a rapidly evolving energy landscape. As systems integrate larger shares of variable renewable generation, operators must adapt operational practices and develop new tools for monitoring and controlling system dynamics. This transformation will likewise require adjustments to market design and regulatory frameworks, so as to appropriately value and incentivise stability services such as frequency support, voltage regulation, and fast dynamic response. Finally, the talk evaluates the role of emerging technologies in supporting the stability and resilience of future power systems. Modern power electronic converters and their control architectures are considered alongside the growing contribution of energy storage. Advanced converter control strategies—including grid-forming and grid-following approaches—offer the potential to replicate or even surpass many of the services traditionally provided by synchronous generators. In combination with energy storage, these technologies can make substantial contributions to frequency control, voltage stability, and overall system resilience. The presentation concludes by discussing how these technological solutions must be embedded within evolving Grid Codes and operational standards. Establishing clear technical requirements for inverter-based resources will be essential to ensure that new generation and storage assets contribute effectively to system stability. Drawing on the lessons of the 2025 Iberian blackout, the talk highlights the broader implications for power system planning, operation, and regulation in the transition towards fully decarbonised electricity networks.

Keywords: Decarbonization of the power system, Stability of electrical power networks, Iberian power blackout 2025, Control of power converters for renewable energy sources, Ancillary grid services, Energy storage