Inertia of the electric power system with micro grids and renewable energy sources

The paper defines the Coefficient of Accumulated Kinetic Energy (CAKE) as an indicator of the sufficiency of kinetic energy in the rotating masses of thermal and hydro generators that are engaged to cover the power system load diagram. Knowledge of this indicator is of great importance in a situation of increasing engagement of renewable energy sources (RES). The variability of the available RES continuously alters the available inertia of the electricity system, i.e. its available kinetic energy needed to prevent an unwanted drop in the system frequency that occurs immediately after a system power shortage occurs due to generator failure or weather conditions that determine the power output from renewable sources. The calculation of coefficient CAKE was made for the entire power system and for the generators individually. Knowledge of this indicator gives a complete overview of the system's ability to prevent a frequency drop below a certain value (in a concrete analysis, the limit value for the frequency drop is 49.5 Hz). The inadequate value of the CAKE coefficient can be an additional para meter in the short- and long-term generator engagement plan and the quality assessment of theP-fregulation.