Predictive frequency stability control based on wide-area phasor measurements

Wide-area phasor measurements provide a dynamic view of the power system in short-term intervals. The time synchronization and concentration of these measurements opens up a range for wide area applications for protection and control. For each kind of instability, related detection and action schemes can be defined to limit or prevent the system from severe disturbances or even collapses. This paper proposes a novel predictive method for emergency frequency control to be used on such occasions. The proposed method avoids the drawbacks of local underfrequency load shedding schemes, such as delayed response and overshedding, by basing control on synchronized phasor measurements. A single machine equivalent for each power system island including the frequency sensitivity of loads, is computed online using phasor measurements. Using this model the progression of frequency stability after a contingency is predicted and stabilizing load shedding is determined in a co-ordinated way for the supervised area of the power system.