A novel approach to underfrequency load shedding

The research and development of underfrequency load-shedding protection tends to rely on an adaptive approach. Unfortunately, adaptive schemes are very dependent on an active power imbalance determination, based on a measurement of the frequency first derivative. Therefore, their effectiveness might be seriously reduced by a lack of data or the wrong estimation of certain parameters that are needed to accurately define the relation between the frequency first derivative and the active power imbalance. Consequently, it is reasonable to attempt to avoid having to calculate the imbalance. A novel approach to underfrequency load shedding is presented in this paper, using the frequency second derivative as a source of information for a forecast of the frequency trajectory. A Newton-method-based approximation and the interpolation of the frequency second derivative are continuously performed in order to forecast the minimum frequency value using a numerical integration.