What Happened in ERCOT
Voltage sag shows value of accurate wind forecasting.
Variability is a well-known characteristic of windpower, and system operators know they must plan for changes in wind generation over the course of a day. But when those plans fall short, voltage levels can drop quickly, forcing grid operators to dispatch resources to make up the difference—either by shedding load or bringing reserve generation online.
That’s exactly what happened in ERCOT on an evening in February, when a combination of events left the system operator short on power and long on demand (See Figure 1).