The challenge for the railway sector regarding energy is to increase the capacity while improving the energy consumption and limiting the environmental impacts, and to decrease the investment and exploitation costs, while maintaining safety and service quality. It makes it necessary to rethink railway power supply under future requests, reflecting the status of different systems.
The project FUNDRES presents a deep thinking and related work to define the future of railway, based on new unified Future UNified Dc Railway Electrification System based on 9 kvDC, able to integrate the existing lines during transition period. In the coming years, MVDC power grids will contribute to the deployment of renewable energies and the electrification of transport systems. Compared to classical AC electricity distribution networks, they are generally more energy efficient and facilitate the interconnection of sources, storage elements and loads. In 2018, a new 9 kV DC railway electrification system was presented as an opportunity for railway sector. The ambitions of FUNDRES were to bring substantial improvements in the energy technology area and station for the future unified system based on 9 kV DC. The consortium composed by LAPLACE, EPFL, POLIMI and UIC proposed to develop several scenarios, validated by experimental demonstration at the laboratory level (TRL4) and digital twin which offers the possibility to predict the behaviour of the proposed unified electrical system based on 9kV DC.
The project outputs will be used to deliver new integrated technology demonstrators and scientific progress for the project IN2STEMPO, and more largely for Shift2Rail, which will be implemented in the railway network.
The project FUNDRES allowed to demonstrate:
- The possibility to restore braking energy to the public grid. To study several scenarios, a Real Time Hardware In the Loop (RT-HIL) system has been developed both for MMC and railway system. The RT-HIL system was implemented on a real-time simulator equipment (RT-Box). In parallel with this work, two prototypes of MMC (5 kV / 250 kVA - 48 cells) were built to set-up a test platform to realize an experimental demonstration (currently ongoing) at the real voltage level of the future DC railway electrification system
- The feasibility of the integration of renewable sources into a railway traction system, taking into account the various power flows due to the railroad traffic and the natural variability of the Renewable Energy Sources. This demonstration was made the set up of a Digital Twin (DT) of the future 9 kV DC power system.
- Promising results in terms of energy efficiency have been obtained by carrying out experimental tests of one elementary module of a Solid State Transformer (SST). To do so, an electrical model of a three-wire DC power supply, including SSTs, was proposed to prepare for a transition between 1.5 kV and 9 kV electrification systems. A full 3D design of a 9 kV/1.5 kV SST in a container configuration has been completed.
