Impacts of the changing resource mix on Essential Reliability Services in North America

This paper concerns the changing dynamics of planning and operations of the North American Bulk Power System (BPS) due to the confluence of trends in increasing Variable Energy Resources (VER), the retirement of conventional power plants and the current and future environmental regulations. The work presented is part of a larger effort by the North American Electric Reliability Corporation (NERC) on assessing future reliability needs. Particularly, the commissioning of the Essential Reliability Services Task Force (ERSTF), an effort to understand potential reliability impacts on the way the BPS is planned and operated. The paper reviews Essential Reliability Services (ERSs) - defines key reliability building blocks -such as Voltage and Frequency Support services at their granular component levels. As part of the Frequency Support building block, Ramping Flexibility assessment has been analyzed using two case study examples of North American regional systems; California Independent System Operator (CAISO) and the Electric Reliability Council of Texas (ERCOT). Historical and simulated minutes and hourly data have been used to construct load, wind and solar power profiles, net load duration and ramping capability curves. Base case scenario using historical profiles is presented with and without VER to identify the unique characteristics of each system's ramping requirements. The results clearly distinguish the differences between CAISO and ERCOT's maximum ramping needs based on dominating profiles of load and net load profiles and exemplify BPS reliability concerns related with the need for increasing operators' flexibility.