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Under-frequency load shedding (UFLS) is a classic and a commonly accepted measure used to mitigate the frequency disturbances in case of loss-of-generation incidents in AC power grids. Triggering of UFLS is classically done at frequency thresholds when system frequency collapse is already close to happening. The renewed interest for synchronous condensers due to the global trends on massive commissioning of non-synchronous renewable power generation leading to reduction of system inertia gives an opportunity to rethink the approach used to trigger load-shedding activation. This question is especially relevant for the Baltic states facing a desynchronization from Russian power grid and a necessity to operate in an isolated island mode. The main goal of this paper is to introduce a predictive load shedding (LS) method without usage of either frequency or ROCOF measurements based on the monitoring of active power injections of synchronous condensers and to prove the efficiency of the concept through several sets of case study simulations. The paper shows that the proposed approach can provide a greatly improved frequency stability of the power system. The results are analyzed and discussed, the way forward for the practical implementation of the concept is sketched.

AbstractThe national energy and climate plans developed by the Baltic States for the period up to 2030 foresee a significant increase in the share of renewable energy in final consumption. Therefore, the development of wind, solar and distributed generation in the Baltic electricity system is expected to increase significantly in the next decade and, thus, the need for balancing capacity will increase. The planned synchronisation of the Baltic power system with the power system of Continental Europe in 2025 will also increase the need for frequency restoration and balancing reserves. At the same time, the shutdown of uncompetitive thermal power plants in the Baltics reduces centralized generation capacity. If this trend continues, the risk of electricity supply shortages will increase in the future. Therefore, it is important to identify activities that help mitigate this risk and take timely actions.

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