All of the large-scale regional wind and solar integration studies performed by the National Renewable Energy Laboratory (NREL) and others have identified the lack of power system dynamic analysis as a significant research gap. Acceptable dynamic performance of the grid in the fractions of a second to one minute following a large disturbance (e.g., loss of a large power plant or a major transmission line) is critical to system reliability, thus there is a need to analyze the dynamic behavior of North American systems under high variable renewable conditions. The Western Interconnection, in particular, has a long history of dynamic performance constraints on system operation—so any dynamic performance changes due to increased wind and solar generation could have substantial impact on all aspects of renewable integration. The primary objectives of Phase 3 of the Western Wind and Solar Integration Study (WWSIS-3) are to examine the large-scale transient stability and frequency response of the Western Interconnection with high wind and solar penetration, and to identify means to mitigate any adverse performance impacts via transmission reinforcements, storage, advanced control capabilities, or other alternatives.
WWSIS-3 evaluated a variety of system conditions, disturbances, locations, and renewable penetration levels to help draw broader conclusions from an analysis of two specific types of power system stability: frequency stability and transient stability. A technical definition of the different aspects of power system stability is provided in (Kundur et al. 2004).