Rethinking the Concept of Extreme Contingency for Power Systems with High Wind and Solar Penetration

Extreme contingency is among the central concepts of power system stability analysis and conveys the idea of a severe impact on the system. This paper discusses the intermittency of wind and solar energy sources as a factor that makes it necessary to rethink the concept of extreme contingency for systems with high wind and solar penetration. On the premise that contingency definitions should account for weather conditions, the paper proposes to reclassify some contingencies presently considered extreme as normal and introduces new contingency categories. The following contingencies need to be reclassified: the loss of all units of a wind/solar power plant; the loss of multiple units; and the loss of multiple plants. Contingency categories with variation of wind speed and solar irradiance and with multiple wind/solar plants disconnected pre-contingency are introduced. To explore the relevance of these categories, further analyses with adequate representation of wind/solar power plants are needed.