Impact of the transmission grid on the operational system flexibility

In this paper we consider the effects of the transmission grid on the operational system flexibility and evaluate the trade-offs between various options including committing flexible generation, curtailing Renewable Energy Sources (RES) generation, or allowing flexibility violations in the form of ramping up/down requirements in the presence of high penetration of renewable generation. All ISO/TSO markets in the different time scales are considered in this study, namely the Day Ahead Market (DAM), Hour Ahead Market (HAM) and Real-Time Market (RTM). Our proposed methodology is based on the co-optimization of energy and ancillary services. We deployed the Mixed Integer Programming (MIP) Security Constrained Unit Commitment (SCUC) and the Security Constrained Economic Dispatch (SCED) functions applied to all wholesale energy markets in sequence as they are executed in practice today. This paper describes the proposed methodology and presents numerical results resulting from detailed energy simulations applied to the California ISO energy market. The deployment of a detailed transmission model, the implementation of a new Flexible Ramping AS, and the accurate transition between DAM to HAM to RTM markets are the key original contributions of this paper.