Short-term hydropower optimization and assessment of operational flexibility

Hydroelectric power systems are largely characterized by variability and uncertainty in water resource obligations. Market volatility and the growing number of operational obligations for flood control, navigation, environmental obligations, and ancillary services (including load-balancing requirements for renewable resources) further the need to quantify sources of uncertainty. The variations caused by these factors require the hydropower system to have enough upward and downward flexibility for control technologies, such as dynamic optimal control load-following, unit commitment, or automatic generation, to be effective. Therefore, it is increasingly important to identify measures of operational flexibility to better manage uncertainty and operational obligations. The objective of this paper is to present and discuss approaches for assessment of operational flexibility as a function of dynamic states and control input and how the available operational flexibility can be used by hydropower producers in a comprehensive optimization reformulation to accommodate business procedures to drive the system in an efficient, safe, and interpretable way. The authors consider simple metrics such as power capability and its derivatives as indicators for upward flexibility and effective energy storage capability for downward flexibility. Test results based on the Federal Columbia River power system (FCRPS), managed by the Bonneville Power Administration, Army Corps of Engineers, and Bureau of Reclamation, are presented and demonstrate how operational flexibility can be assessed and that role it plays in short-term operations.