Estimating frequency stability margin for flexible under-frequency relay operation

Abstract

SmartGrid solutions are often misinterpreted as complex approaches requiring large amounts of (online) data and computational power for delivering high-quality results. With today's technology, this is surely the most obvious and technically achievable approach for dealing with complex problems. However, by taking this road in the power system field, providing the required high-level reliability becomes a challenging task. Therefore, a thorough consideration of whether increased complexity justifies the gains is surely warranted, especially when it comes to power system protection, where the applied procedures are all about transparency, simplicity and robustness – which is often in contrast to the above interpretation of SmartGrids. Therefore, the motivation of the presented research was to design an effective SmartGrid solution for avoiding power system frequency instability, appropriate for real-life application. Under-frequency load-shedding protection is the subject of many research activities that often result in complex and, consequently, unfeasible suggestions. In contrast, this paper presents an effective RoCoF-based upgrade to the conventional approach, eliminating its most important shortcoming: inflexibility. By estimating frequency stability margin in real time, shedding decisions remain local, whereas the overall efficiency of this system protection scheme is brought to the level of the most sophisticated solutions available in the literature.