Frequency Reserve Management in Isolated Industrial Systems Dominated by Constant Power Loads

This article explores the application of interconnected synchronous system requirements for frequency containment reserves (FCR) in isolated industrial grids. These grids typically rely on turbogenerators as the main energy source, have a high penetration of wind energy, include energy storage systems, and feature constant power loads connected through power electronic converters. Building on the recent Nordic FCRI requirements for islanded operation, we propose an extension that enables prioritization among different reserve providers based on specific grid conditions. A complex isolated industrial grid is selected as a case study to evaluate this approach. The grid’s stability is analyzed using eigenvalues and participation factors, taking into account the negative effects of constant power loads. The study shows that allocating reserves to faster, converter-interfaced storage devices and loads improves overall system stability and allows turbogenerators to operate under more constant loading conditions. The results are validated through computer simulations in DIgSILENT PowerFactory and laboratory power-hardware-in-the-loop experiments, which compare the proposed approach to standard droop control methods. Furthermore, the simulation models developed for this study are made publicly available to ensure reproducibility.