As the penetration of renewable energy sources (RES) deepen on the supply side of power systems, there is an increased need for flexibility to accommodate the vagaries and deviations from forecasts. In order to respond to this need, implicit and explicit approaches have been proposed. Implicit approaches, such as advanced scheduling methods allocate recourse in the operating planning stage to be released when actuals materialize in real time. The ability to maintain the balance in real time depends on the quality of the uncertainty model (e.g. scenarios, uncertainty budget, bounds, etc.), which often also increases the computational burden. On the other hand, explicit approaches allocate the needed flexibility via time-dependent capacity and ramp constraints in the operating planning process. In this case, the ability to maintain balance in real time depends on the quality of the forecasts of dynamic headroom and ramping needs. While both approaches tackle the same problem, they have different implications in terms of i) understanding the method and results; ii) computational performance and scalability; iii) actual adoption for system operation. This presentation summarizes the differences between implicit and explicit methods, as well as propose a viable path for system operators to adopt methods that that capture the system flexibility needs, without needing reformulations of existing scheduling approaches, and therefore to be able to use them in actual system operation.
Miguel A. Ortega-Vazquez is a Senior Technical Leader at the Electric Power Research Institute (EPRI) in Palo Alto, CA, and Affiliate Assistant Professor in the Department of Electrical and Computer Engineering at the University of Washington in Seattle, WA. Before joining EPRI, he was Assistant Professor at the University of Washington in Seattle, WA; and before that, Assistant Professor at the Chalmers University of Technology, Sweden. He holds a Ph.D. from The University of Manchester; M.Sc. from the Universidad Autónoma de Nuevo León, Mexico; and an Electric Engineering degree from the Instituto Tecnológico de Morelia, Mexico. His current research interests include power system operation and planning, power system economics, integration of renewable energy sources, and the smart grid. Dr. Ortega-Vazquez is an Editor of the IEEE Transactions on Smart Grid.