Combined Frequency Control From Trains Thermal Inertia: An Assessment of Frequency Controllers Interaction

The increasing introduction of power electronics into electric power systems requires more effort to maintain the stability, reliability, and security of grids. Among these, the frequency stability is worsened by the displacement of conventional generators. Demand response has been considered as an alternative to ensure grid stability. The present work proposes a combined frequency control for railway systems to support grid ancillary services without risking the circulation of trains and the comfort of passengers. In contrast to current demand response algorithms, it provides primary and secondary frequency control, and virtual inertia. In addition, due to the rising dynamics complexity in grids, this work presents a performance-based methodology to assess the interaction among frequency controllers without needing detailed models. Simulation and experimental case studies are presented to exemplify and validate the proposed method. The results demonstrate the effectiveness of the methodology in allowing a fast and low-complexity assessment. In addition, the benefits of the proposed control are demonstrated by several performance metrics. The coherence between simulation and experimental results validates the reliability and implementability of the proposed method in a real microgrid.