In the early days of electric rail transport, rotating machines and transformers were used to convert electricity voltage levels and frequencies. But as speed levels and rail networks have grown, the technology used for frequency conversion has also moved on. Since the 1970s this has been achieved through frequency converters based entirely on power electronics.
ABB has delivered a solution based on an SFC system as part of the New Generation Rollingstock (NGR) project, an expansion plan for the Queensland Rail system, which covers suburban and long-distance routes through this northeastern Australian state. Rather than synchronizing grid frequencies, this SFC system converts the phases of the power supply – namely from Australia’s three-phase high-voltage national grid to the single-phase 25-kilovolt Queensland Rail grid, which both have a synchronized frequency of 50 hertz (Hz). While SFCs for 16.7 and 25 Hz are well established, the traditional solution for 50 Hz power systems has been transformers, and this is the first SFC of this configuration delivered by ABB and one of the first installed in Australia.
The solution is proving effective and has many advantages such as fewer network issues with unbalanced loads, step changes in load and harmonics, better reactive power support on both the three-phase and single-phase sides of the substation and also the possibility to load share with the adjacent feeder station thus giving greater strength to the power network.
In addition to the SFC solution, ABB has provided a modular switch room with gas-insulated medium-voltage switchgear to upgrade an existing feeder substation and was responsible for the design, engineering, installation and commissioning of the project.
A new purpose-built maintenance center and the associated increase in rolling stock movements on the main line and within the service center is powered by this upgraded traction feeder substation.
The NGR project, undertaken by the Queensland government, includes the addition of 75 new six-car electric trains – a 30 percent increase of the fleet – that will come into service on the network in 2016. NGR is considered a significant public transport expansion to meet the rising demand for rail services in southeast Queensland and reduce the constantly growing amount of private vehicles on the road.