Impact of multiple flexible loads on grid stability for Fast Frequency Reserve

The increasing share of integrated renewable energy sources results in weaker grids and reduced system inertia, posing challenges to grid stability. To address this, fast frequency reserve (FFR) services are being introduced to tackle this problem. Inverter-based loads, with their rapid response, can enhance grid stability by providing FFR services. Therefore, this work aims to investigate the concurrent support provided by various types of flexible loads (FL) (e.g. data centers, charging stations, and hydrogen electrolyzers) under current and future grid conditions. This investigation is conducted through case studies using as a base a 12-bus grid model that incorporates existing frequency containment reserve for disturbances (FCR-D) support provided by hydro units in the Nordic system. The simulation models of introduced FL capture their control loops and main dynamics. The results show that concurrent FFR support of multiple different FLs (without communication with each other) improves frequency response during disturbance in the considered system for the 15% and 30% of wind power plant penetration (WPP). However, with the higher penetration share of 50% of WPP, the current FFR response characteristics with existing FCR-D cannot maintain stable system operation once FFR is deactivated.