Incorporating Optimal Transmission Switching in Day-Ahead Unit Commitment and scheduling

Abstract

Day-Ahead Unit Commitment is a typical business process of regional transmission organizations (RTO) and some vertically integrated utilities to ensure enough generation capacity is committed day-ahead to meet the load for the next day. In many cases, transmission constraints are required to be taken into consideration under the framework of security-constrained unit commitment (SCUC). Transmission lines are traditionally treated as non-dispatchable assets. Co-optimizing transmission topology with generation dispatch, and leveraging grid controllability could be a viable way to improve economic efficiency of system operations. In a market environment, day-ahead reliability unit commitment (DA-RUC) performs a simultaneous solution of minimizing the cost of commitment for resources to meet forecasted load, net scheduled interchange and operating reserve requirements using SCUC. The commitment may then be further checked by running Security Constrained Economic Dispatch (SCED) to verify that the commitment solution can be feasibly dispatched subject to system constraints and activated transmission constraints for each hour identified in the study period. This paper applies Optimal Transmission Switching (OTS) in DA-RUC using pre-selected set of switchable lines for a large network. Various selection methods of candidate transmission lines are proposed and compared. Simulation results will be presented to demonstrate generation dispatch combined with OTS in each hour could reduce congestion cost and significantly lower generation cost.