Reliability unit commitment in the new ERCOT nodal electricity market

ERCOT is transitioning from a current zonal market to a newly redesigned nodal market. In the new ERCOT nodal wholesale market, a Reliability Unit Commitment (RUC) process is designed and implemented to ensure transmission system reliability and security. The main objective of RUC is to ensure that enough resource capacity, in addition to ancillary service capacity, is committed in the right locations to reliably serve the forecasted load in the ERCOT system. The RUC is implemented in a Security Constrained Unit Commitment (SCUC) framework that minimizes the total operation costs based on generator three-part supply offers subject to various system and resource security constraints. Some enhanced features have been implemented in the RUC SCUC engine to handle special resource scheduling such as combined cycle resources, split generation resources and self-committed resources. The RUC settlement uses a “make-whole” payment to ensure all generating resources committed by RUC are adequately compensated for their operation costs.