Local Frequency Transients in the Future European Synchronous Transmission Grid

The planned shutdown of coal and nuclear power plants together with the increasing presence of converter-interfaced systems such as HVDC links and Renewable Energy Sources (RES) is modifying the traditional structure of power systems. This trend leads to a decrease in available kinetic energy that affects frequency stability since conventional power plants are being displaced. A common practice during frequency studies is to consider only the Center of Inertia (CoI). This approach implies the neglect of local frequency and RoCoF transients. Such an assumption might not always be valid. In this work, we elaborate on the mechanism behind the origin of local frequency transients. Then, we demonstrate with dynamic simulations that these transients can occur in the European context after a plausible single-contingency. The results lead to practical conclusions relevant to transmission system operators. For instance, we identify that zero inertia regions do not directly imply a worse local transient behavior.