Marginal Pricing Scheme for Ancillary Service Provision From Flexible Nuclear Power Plant

The integration of large-scale non-synchronous Renewable Energy Sources (RES) and the expansion of nuclear power capacity in Great Britain's electricity grid raises several challenges. While the variability and uncertainty of RES increase the risk of frequency instability, traditional nuclear plants offer limited operational flexibility with restricted load-following capabilities and a reduced ability to provide Frequency Response (FR) services. This study addresses these technical challenges by proposing a marginal pricing framework for Ancillary Services (AS) such as inertia and FR, explicitly considering the participation of Flexible Nuclear Power Plants (FNPPs). FNPPs are enabled through the integration of Thermal Energy Storage and a Secondary Steam Rankine Cycle, significantly enhancing their load-following capabilities and ability to provide FR. A Mixed-Integer Second-Order Cone Programming model is developed to co-optimise energy and AS provision, including Primary Frequency Response, and inertia from FNPPs, thermal power plants, and Enhanced Frequency Response from Battery Energy Storage Systems. Case studies based on GB's 2030 power system validate the model and quantify the system benefits and market signals under varying scenarios of wind penetration and FNPP participation. Results show that FNPPs can play a vital role in maintaining grid stability and reducing system operation costs under the proposed market structure.