Real Time Frequency Response Assessment Using Regression

Synchronous power system inertia is declining, due to the increasing penetration of inverter-interfaced generation. This entails faster and greater frequency decrease after generation outages. When the system encounters low values of system inertia, frequency containment reserves may not be capable of retaining frequency over the threshold for underfrequency load shedding. These system changes necessitate the real time assessment of frequency response and specifically, the assessment of frequency nadir. The method that is currently used for frequency response assessment by the Swedish system operator examines the relation between the frequency nadir, the system kinetic energy, and the size of the disturbance through linear regression. This paper evaluates the aforementioned method and proposes a modified realization of the regression to achieve higher accuracy. Furthermore, the uncertainty that the system nonlinearities introduce in the method is quantified.