Practical and theoretical approaches to detecting grid dynamics and stability

Abstract

Abstract: Electricity supply systems used to be operated in accordance with strict hierarchical principles. Major power stations controlled the grid frequency and balanced load as well as stabilized voltage levels. In such a system the high inertia of power producers posed a natural limit on the amount of observable dynamic effects and maintained good resilience against Blackout phenomena during overload situations. However, as more and more small, distributed energy producers enter into the picture, inertia is lost and concern for dynamic instabilities grows. This paper gives examples of some dynamic disturbances of electrical grids under stress and points out innovative methods for their quick and sensitive detection, such as Wavelet-based subharmonic oscillation detection. Furthermore, when electrical grids are closer to breakdown they can enter a nonlinear regime where the statistical properties of the state variables become more and more pronounced. We argue that in some situations these statistical fluctuations can be a good early indicator for an upcoming Blackout and propose how to capture breakdown criticality with an appropriate measurement algorithm based on the analysis of voltage statistics.