Operational Risk Impact of Flexibility Requirements and Ramp Forecast on the North American Bulk Power System

This paper analyzes the impacts to system flexibility and reliability risks resulting from ramping uncertainties associated with variable energy resources (VERs) such as wind and solar power. A detailed assessment using statistical analysis and forecasting models is applied to an ERCOT case study for a one-hour to 72-hour look-ahead period. The operational impacts of variable energy resources combined with load variations are examined under multiple scenarios. The results show a need to plan for additional flexible resources to manage ramping uncertainty as more variable energy resources are integrated into the system. Forecast accuracy is analyzed and error measures are determined at different VER penetration levels. The findings also suggest the importance of advancing probabilistic modeling tools to support reliability analysis and planning. New tools are needed to enable a flexible and reliable system under conditions of high variability associated with VERs combined with load uncertainty.