D10.2 – Energy storage solution for AC railway grid : A description document for the optimal design and control strategies of energy storage and interface converter for AC infrastructure

The document depicts the advancement of Task 10.2. This work develops a comprehensive system-level simulation model of the Swedish railway traction power system based on real-world field data. The model includes detailed sub-models of static frequency converters (both DC-link and multilevel topologies), electrical locomotives, catenary systems, high-voltage feeder lines, and traction transformers. Its validity is demonstrated through two representative case studies. Various energy storage solutions and corresponding interface converter technologies are investigated and evaluated for the energy storage system (ESS) deployment in railway applications, with a final focus on Li-ion batteries, supercapacitors, flywheel ESS and superconducting magnet energy system (SMES). A dedicated DC-AC converter topology is designed to support ESS integration, aiming to enhance voltage stability and facilitate regenerative braking energy recovery. The performance of the proposed converter, in combination with the four selected ESS technologies, is evaluated with and without a bidirectional DC-DC converter. Furthermore, a novel ESS integration method into existing static frequency converters is proposed to enable peak power shaving and improve the utilization of regenerative energy. This approach is demonstrated using a multilevel converter equipped with supercapacitors, with performance assessment conducted through the developed simulation framework.