ABB has delivered the world’s most powerful rail frequency converter for German utility E.ON. The installation at the Datteln railway hub in the north west of the country can supply up to 413 MW to feed DB Energie’s traction power supply.
ABB has delivered the rail static frequency converter (SFC) system as part of a turnkey package that includes design, engineering, installation and commissioning alongside other key components such as transformers, control and cooling systems.
E.ON ordered the converter station as part of its project to replace a time-served 303 MW coal- fired power station that was built in the 1960s as a dedicated power generation asset to supply railway traction power.
The system has the role of converting electricity from the three-phase high-voltage grid at a frequency of 50 Hz to the 16.7 Hz required by the single-phase 110 kV Deutsche Bahn traction supply.
Four identical converter blocks
As part of this, E.ON specified the power converter system at a rating of 413 MW to meet growing demand. This makes the system the largest of its kind and compares with most installed systems which have power capacity in the region of 15 to 30 MW, such as the inverter station Wimmis for the Swiss Lötschberg railway tunnel.
Niklaus Umbricht, Project Manager at ABB Switzerland said: “The plant in Datteln is now a quantum leap for us. Thanks to continuous improvements in power electronics and a standardized, compact design, we can now convert higher power more efficiently."
ABB’s solution is based on state-of-the-art power electronics with four identical converter blocks of 103 MW. This arrangement was chosen so that maintenance work can be carried out on one of the converter blocks without compromising the conversion capacity of the entire plant. As a result, the converter delivers exceptionally high levels of system availability and reliability.
High efficiency is guaranteed by the Integrated Gate Commutated Thyristor (IGCT) power electronics semiconductor elements. They ensure that no additional line filters are required to compensate for voltage fluctuations and so help to maintain the required grid stability at all times.
Static frequency converters
SFCs are used on the electrical grid to interconnect power networks operating at incompatible frequencies – for example, the shore-to-ship power connections for a cruise ship, which operates at 60 Hz and needs to connect to the shore-side network running at 50 Hz.
SFCs can also be used to interconnect neighbouring distribution grids. For example, ABB installed a 20 MW unit for Western Power Distribution to balance voltage and power flows through two otherwise incompatible 33 kV networks. The installation has unlockedaround 344 MW of power capacity locally, avoiding the need for a costly upgrade to the transmission grid.
Rail traction applications
ABB has been providing SFC technology for railway interconnections since 1994. Its medium- voltage rail SFC solution allows the connection of three-phase public grids to single-phase railway power grids at frequencies of 16.7, 25, 50 or 60 Hz.
The SFC acts as a source of voltage and reactive power, but also ensures a smooth transition from interconnected system operation to island mode in case of disturbances on the grid. It also ensures grid code compliance without the need to install line filters.
Furthermore, the SFC can act as the sole power supply to an isolated section of the railway and subsequently re-synchronise with the rest of the railway traction grid after the disturbance has been cleared.
SFC technology for Network Rail
In 2017, ABB announced a contract with Network Rail to supply a similar system to upgrade the power supply for the East Coast Mainline. With new InterCity Express trains due to start running on the line, Network Rail recognised the need to reinforce its power supply to supply both the main track and Hitachi’s new maintenance depot in Doncaster.
The new trains will require around three times more power than is currently provided by the existing supply. The conventional solution would be to build a new high-voltage grid connection. However, this would be costly and would require a lengthy lead time.
Instead, Network Rail called on ABB to deliver a solution based on an SFC to adapt the feed from Northern Powergrid’s local distribution network.
Taking this approach will deliver an estimated total cost saving of around 60 percent compared with building a new high voltage substation.
