CONTRIBUTION OF WIND POWER PLANTS' SYNTHETIC INERTIAL RESPONSE TO SYSTEM INERTIA IN THE PROSPECTIVE POWER SYSTEM OF SERBIA

Frequency stability in power systems refers to the system’s ability to maintain frequency within permissible limits following disturbances such as sudden changes in consumption or generation, or outages of generating units. The rotating masses of synchronous generators in hydropower plants and thermal power plants, which store kinetic energy, serve as the primary source of inertia in Serbia’s modern power system. When a frequency disturbance occurs, these rotating masses slow down the frequency deviation, providing a time buffer for the activation of primary frequency control resources. However, the decarbonization of electricity generation is leading to a decreasing share of conventional sources in the generation mix and a rapid increase in the installed capacity of new renewable energy sources (RES). Modern wind turbines are connected to the grid via power converters, which decouple the generator from the grid frequency, making them insensitive to frequency changes in the system. However, a frequency-sensitive control loop can be implemented in the converter—known as the synthetic inertial response concept—allowing wind turbines to contribute to system inertia by utilizing the kinetic energy stored in their rotating masses, primarily in the turbine and generator. In this study, specific kinetic energy is defined as a relevant metric for assessing available system inertia. It represents the ratio of available kinetic energy in the system to the total generation power during the analyzed hour. This indicator provides a realistic representation of the system’s ability to respond to disturbances, as it effectively quantifies the available kinetic energy per megawatt of potential imbalance caused by generating unit outages. By analyzing the dynamic changes in this parameter, the impact of integrating future RES capacities on system inertia is examined. The study also evaluates the potential of wind turbines to provide inertial support in Serbia’s prospective power system under two RES development scenarios and two hydrologically extreme years. The available kinetic energy of wind turbines is not a fixed value, as turbine speed varies with wind speed fluctuations. Additionally, not all wind turbines within a wind farm operate at the same operating point, making it necessary to calculate the kinetic energy of each wind turbine individually for each operating state, followed by an assessment at the wind farm level. The estimation of wind farms’ kinetic energy contribution in the prospective system is based on an analysis of the Čibuk 1 wind farm, considered representative of future wind power capacities in the system.