A network-inclusive, optimization-based approach to power system flexibility evaluation

The central task of power system planners is to design and implement a power system with sufficient electricity supply to meet the load at all times and that of their operator counterparts is to deploy the available supply to meet changes in the load and ensure supply matches the load around-the-clock. Power system flexibility-the ability of the resources in the system to respond to the variability and uncertainty of the load-enables planners and operators to manage load and supply uncertainty to achieve the supply-demand balance. A surge in wind and solar development over the past decade has begun to shift the focus from meeting the load to meeting the net load-the load minus the output of wind and solar generators. The net load generally exhibits higher variability and uncertainty than the load alone. With deepening wind and solar penetrations, there is an acute and growing need to evaluate system-wide flexibility to ensure sufficient supply is in place and online so that the additional variability and uncertainty associated with the net load can be effectively managed and the net load reliably and economically met. In this paper we introduce a general methodology for evaluating system-wide flexibility that takes into account supply-and demand-side sources of flexibility and includes network impacts. Furthermore, we describe how this methodology can be applied to give planners and operators a tool to assess the risk of insufficient flexibility.