Measuring effective area inertia to determine fast-acting frequency response requirements

Abstract

Renewable generation and power electronic convertors increasingly displace the inertia conventionally provided by synchronous generation in the transition to a low carbon electricity network. Changes in generation profiles influence regions of the grid disproportionately, and areas of low inertia are susceptible to frequency diverging from neighboring areas, creating new risks of Rate Of Change Of Frequency (ROCOF)-based generation trips, underfrequency load shedding and islanding. A novel method of measuring area inertia is presented, with results of simulation and trials on the SP Energy Networks (Scottishpower) transmission system in south Scotland. The fundamentally new understanding of frequency and inertial effects is essential for designing mitigation measures for frequency and network stability, and enables new, flexible services for the transition to low inertia power systems.