FACTS for dynamic load balancing and voltage support in rail traction

With increasing focus on economical as well as environmentally friendly means for mass transit, rail transport is gaining renewed momentum in many parts of the world. This means investing in novel rail infrastructure as well as upgrading and electrifying existing facilities. The TEN (Trans-European Network) program within the European Union is but one current example of the importance attributed to more and better mass transit all over the world. The feeding of heavy rolling stock from AC grids will in many cases cause unacceptable voltage drops as well as unsymmetry between phases of the feeding grid. A traditional way to improve the situation would be to build additional power transmission lines and/or step up the feeding voltage to a higher level. This, however, may be undesirable or even impossible, for cost reasons as well as for environmental reasons. FACTS devices offer means of remedy within the existing feeding grid, restoring grid symmetry as well as voltage stability, and also mitigating harmonic distortion emanating from rolling stock. FACTS devices such as SVC (Static Var Compensator) and STATCOM (Static Compensator) are well proven and commercially available today. The paper treats dynamic load balancing of grids supplying power to rail transport, as well as dynamic voltage support and harmonic mitigation, by means of SVC as well as STATCOM.