Flywheel Energy Storage Model, Control and Location for Improving Stability: The Chilean Case

A flywheel energy storage (FES) plant model based on permanent magnet machines is proposed for electro-mechanical analysis. The model considers parallel arrays of FES units and describes the dynamics of flywheel motion, dc-link capacitor, and controllers. Both unit and plant-level controllers are considered. A 50-MW FES plant model is tested in the Northern Chile Interconnected System (NCIS) when connected to the Argentinian Interconnected System (AIS). The FES plant provides transient support for primary frequency regulation and its impact on stability is studied using small-signal analysis and time domain simulations. To identify the best location to install the FES plant, eigenvalue sensitivity for the interarea mode is analyzed. The results are validated for different operation scenarios of wind and solar power. By installing the FES plant in the NCIS best location, the damping ratio of the interarea mode is increased from 0.53% to 13.1%. Moreover, the power transfer from the NCIS to the AIS can be augmented from 90 to 180 MW while still keeping the damping ratio above 9%. These findings are promising and may lead to useful planning criteria for energy storage deployment.