The Swedish Transport and Infrastructure Ministry is looking for an energy-efficient and cost-efficient solution to guarantee the power supply for its growing railway traffic. To boost the traction power supply network, the local transport authority Trafikverket has tasked Siemens with setting up a Sitras SFC plus static frequency converter to feed in power from the 50 Hz public grid to the 16.7 Hz traction power supply network. The order is worth around EUR 17 million, and the converter will come into operation in the spring of 2017.
The special feature of the Sitras SFC plus is its multilevel converter technology: with a modular design, it operates with several series-connected power transistor elements (IGBT) and capacitors which assemble the desired voltage from small steps. This reduces the switching frequency and thus the power loss by around ten percent
compared to previous systems. The noise level was also reduced, benefiting local residents. Multilevel systems also take up around 20 percent less space as they can be set up in a more compact way than the other solutions offered on the market.