Assessing the Effects of Low Load on Under-Frequency Load Shedding Schemes and Exploring Potential Solutions: A Review

Grid frequency decline under load-generation imbalance can be corrected by shedding a certain amount of load. However, due to the rapid uptake of distributed photovoltaic generation, the visible loads to system operators in distribution feeders are reducing. Traditional load-shedding schemes are facing challenges due to the low-load situation. The required amount of demand reduction cannot be achieved with the traditional load-shedding schemes as before. In some situations, with reverse power flows, load shedding can further increase the generation deficit. Power system operators have temporarily included important loads into UFLS schemes to attain the necessary load levels, but this has reduced the reliability of critical loads. This paper discusses the impacts of the low-load problem and reviews the solutions suggested in the literature.