Challenge

To increase availability and reduce maintenance efforts while maintaining the traction power supply service level at the lowest possible cost, DB wished to replace its existing rotating equipment in Bützow and Schwerin (Germany). For both locations, two static converter stations of 2x15 MW each to feed the 16.7 Hz 15 kV overhead catenaries were contracted as a turn-key project to a consortium with Power Conversion & Storage as the key participant. The systems are currently in commissioning phase.

System overview

Each station consists of two independent blocks operating fully redundantly. They connect to the 110 kV 3-phase grid through an oil-immersed transformer (ONAN cooling system) and feed the 15kV 16.7Hz overhead catenary system directly. For maximum efficiency, each block employs air-core reactors on the 15 kV rail electrification side (transformer-less design). Connection of a 50 Hz filter is not necessary thanks to the innovative converter concept and control algorithm. On the 15 kV rail side, only a small passive filter is required to meet the strict harmonics requirements of DB.

Providing the interface to the distribution grid

Cooling system

Each converter block has its own dedicated closed-loop cooling system with a mix of glycol and water The power electronics is directly cooled with this fluid, to achieve compact design and small space requirements. The heat is then dissipated in a water-air heat exchanger. A high-availability canned motor pump is installed to provide continuous circulation. All systems are monitored automatically. Additional secondary air-cooling is provided for the E-house in each block.

Control system

Internal converter control enables the following operation modes:

• Standard control in all 4 quadrants (according to the P/f, Q/U characteristic)
• Reactive Compensation/ STATCOM (supply of reactive power to the railway grid only)
• Parallel operation with other generation units integrated on the 15kV line
• Isolated mode (creating independent rail grid), with automatic synchronization to three-phase grid before reconnection
• Remote control by sinusoidal reference signal (Pilot Mode) or Autonomous Mode based on asynchronous telemetry reference signal can be provided as well.
• Black Start-Up of rail grid

Remote short circuits are handled reliably by the control algorithms. The control system allows for either local or remote operation via a user-friendly HDM interface and integration to SCADA according to IEC 61850 (IEC60870-105-4 can be provided as well).

Our SFC technology brings multiple advantages to the operator 

Static frequency converter for railway application

In 2014, GE Vernova’s Power Conversion & Storage business delivered and commissioned the SFC systems for the Bauhinia electrification project in Australia. It was the very first time that power electronic converters were employed to feed a 50 Hz electric railway.

System Overview

The project encompassed two independent feeder stations, each featuring a 19 MVA converter system based on Power Conversion & Storage’s proven MV7000 converter technology. 

These converters are housed within a transportable substation building, which includes a control room, while additional supporting equipment is located externally.

A single converter block comprises the following main components:

• Input 3-phase 4QS sub-inverter with three single-phase modules
• DC link with an extensive capacitance
• Output 1-phase 4QS sub-inverter with two phase modules 

The core components of each sub-inverter are the press-pack IGBT modules, arranged in two phase segments and equipped with a patented pull-out mechanism, including the IGBT control amplifiers.

SFC system details

Transformer

The design of the converter system necessitates the installation of two transformers for each converter block. Both transformers are designed for outdoor use and feature an ONAN cooling system, tailored for the hot weather conditions of Queensland, Australia. The input transformer, rated at 132 kV and 50 Hz, has three output windings that directly supply the three inverter units. The output transformer increases the converter’s single-phase 16.5 kV output voltage to supply the railway with a ±25 kV, 50 Hz power. A railway filter is connected to both the output of the railway transformer and its auxiliary winding.

Cooling system

Each converter block features its own dedicated cooling system, using a glycol-water mixture to directly cool the power electronics. The cooling system is designed to operate in temperatures up to 45 degrees Celsius and includes an enhanced water-air heat exchanger to manage the minimal temperature difference between the ambient air and the required inlet fluid temperature. Two water pumps are installed with complete redundancy to ensure continuous circulation, with the pumps alternating every 24 hours. Additional air conditioning is provided for the station premises.

Control system

The internal converter control system facilitates the following operational modes: 

• Standard control in all four quadrants,
• Phase shift operation (supplying reactive power solely to the railway grid),
• Parallel operation with the existing standard 50 Hz railway feeding system,
• Isolated mode (establishing its own railway grid).

The control system can be operated locally or remotely through a user-friendly HDM interface.

Proven expertise and local support

Opting for Power Conversion & Storage’s SFC technology offers several benefits:

• An unparalleled blend of proven static frequency converter technology, extensive global rail expertise, and localized support, including engineering, project management, and service,
• High efficiency and low operating costs,
• Single output transformer,
• High availability, due to a modular design and high degree of standardization,
• IGBT design optimized for highly dynamic loads,
• Maintenance-optimized design,
• Short commissioning time,
• Scalable concept.

Technical specifications

In 2016, GE Vernova’s Power Conversion & Storage business delivered and commissioned the SFC systems for the Moreton Bay Rail link project in Australia. This was the first implementation of SFC technology in an Australian metropolitan rail network.

System overview

The project encompassed two independent feeder stations, each featuring a 15 MVA converter system based on Power Conversion & Storage’s proven MV7000 converter technology.
These converters are housed within a transportable substation building, which includes a control room, while additional supporting equipment is located externally.
A single converter block comprises the following main components:

• Input 3-phase 4QS sub-inverter with three single-phase modules
• DC link with an extensive capacitance
• Output 1-phase 4QS sub-inverter with two phase modules

The core components of each sub-inverter are the press-pack IGBT modules, arranged in two phase segments and equipped with a patented pull-out mechanism, including the IGBT control amplifiers.

SFC system details

Transformer

The converter system design necessitates the installation of two transformers for each converter block. Both transformers are intended for outdoor installation and are equipped with an ONAN cooling system tailored for the hot weather conditions in Brisbane, Australia. The input transformer, rated at 33 kV and 50 Hz, features three output windings that directly supply the three inverter units. The output transformer increases the converter’s single-phase 14.7 kV output voltage to supply the railway with 25 kV at 50 Hz. A railway filter is connected to both the output of the railway transformer and its auxiliary winding

Cooling system

Each converter block is equipped with its own dedicated cooling system, which uses a glycol-water mixture to directly cool the power electronics. The cooling system is designed to operate in temperatures up to 45 degrees Celsius and features an enhanced water-air heat exchanger to manage the minimal temperature difference between the ambient air and the required inlet fluid temperature. Two water pumps are installed, offering 100% redundancy to ensure continuous circulation. These systems are monitored continuously, and the pumps are alternated every 24 hours. 

Additional air conditioning is provided for the station premises

Control system

The internal converter control system enables the following operation modes: 

• Standard control in all four quadrants,
• Phase shift operation, providing reactive power exclusively to the railway grid,
• Parallel operation with the existing standard 50 Hz railway feeding system,
• Isolated mode, where the system operates its own railway grid. 

The control system supports both local and remote operation through a user-friendly HDM interface.

Proven expertise and local support

Opting for Power Conversion & Storage’s SFC technology offers several benefits:

• An unparalleled blend of proven static frequency converter technology, extensive global rail expertise, and localized support, including engineering, project management, and service,
• High efficiency and low operating costs,
• Single output transformer,
• High availability, due to a modular design and high degree of standardization,
• IGBT design optimized for highly dynamic loads,
• Maintenance-optimized design,
• Short commissioning time,
• Scalable concept

Technical specifications

One of the oldest railway lines in Germany, the "Südbahn", now running continuously with electricity

The line was one of the very few two-track non-electrified main lines in Germany and has been connecting the entire Lake Constance region for more than 150 years, but also has a very high priority as a European transport axis with international connections to the Austrian Vorarlberg and the eastern Swiss region and beyond.

It was therefore included in the demand plan for the expansion of the federal railways as a priority and international project. Last but not least, the upgraded Südbahn also offers an impetus for environmentally friendly tourism and opportunities for a further modal shift to rail.

Where diesel locomotives used to run, they are now more environmentally friendly operated with electricity. Continuous electrification is a further step towards the complete electrification of the German rail network. The federal, state and DB have jointly invested a total of 370 million euros.

Challenge

The electrification of the German rail network protects the climate and the environment. Almost two thirds of the federal rail network are electrified (as of 2022), thus equipped with an overhead contact line and thus suitable for the operation of e-locomotives or e-trolley.

Often, partially electrified lines can only be used with diesel locomotives, as a mixed operation is logistically and economically unsustainable.

Solution

GE Electrification with its consortium partner GE Electrification were selected by Deutsche Bahn to build the rail power supply plant with two 15 MW rail converters (with control and protection as well as harmonic filter). These have been reliably feeding the overhead line between Ulm and Lindau since the start of electric train operation in December 2021. End of August 2022, the trial operation was successfully completed followed by the final acceptance by DB at the end of September.

Background

Historically, the electric railway power grid in Germany is operated with alternating current of the frequency 16.7 Hz. The railway electricity system requires its own "world of electricity", which is designed exclusively for this frequency from the power plant via a high-voltage distribution grid to the substations. The railway’s own 110 kV high-voltage grid with a length of around 7900 kilometers (DB Energie GmbH) connects power stations, and converter station.

The conventional answer to the requirement to convert from 50 Hz to 16.7 Hz were rotating machines. The modernization of converter stations is carried out with the help of power converters, which transition the process from a mechanical to an electronic one and thus ensure the supply of the overhead lines in the railway network with electrical energy - for sustainable electrification of the entire railway network.

Looking at the future

The federal government had already set itself the goal of increasing the degree of electrification of the federal rail grid from currently around 62 percent to 70 percent by 2025. GE is ready to support Deutsche Bahn in the electrification of the rail network and thus make an important contribution to the path towards climate-neutral passenger transport.

“More speed with the electrification makes sense not only for climate protection,” says Dirk Flege, managing director of Allianz pro Schiene and continues “The shift to rail plays a key role in the transport sector since rail transport consumes 5,5 times less energy than road transport. The rail network’s capacity must be expanded to shift more traffic to the rails in the future. The rapid electrification of more routes is also critical because it makes the rail network more flexible and thus more efficient.”

Steel plant - Sremska Mitrovica, Serbia

Metalfer Steel Mill (MSM) is a Serbian steel plant, located in the Northwest of the country, close to the Croatian border. It is owning and operating an EAF-based steel mill manufacturing construction steel products from recycled scrap metal. They are the only rebar producer in Serbia and the leading supplier on the local market, also exporting to the neighboring countries.

MSM is part of Metalfer Group, an industrial group of companies involved in mining, metallurgy, energy, and trading, established in Serbia in 2002.

In November 2021, GE Power Conversion was awarded a contract to provide MSM with a STATCOM system to help stabilize the local grid.

Challenge

Our customer is operating a mini mill based on an Electric Arc Furnace (EAF) melt shop with a capacity of 400 kT/Y. The EAF is generating high voltage flicker, that the existing SVC system cannot compensate enough, preventing the facility from reaching the standard limit.

The flicker is causing significant power quality issues, to the plant itself but also to the neighborhood. As the Croatian authorities were complaining, MSM has been ordered by the local Transmission System Operator (TSO) to resolve the problem or to shut down the power.

Solution

To answer this need for high compensation level, GE Power Conversion proposed a STATCOM system based on its Modular Multilevel Converter (MMC) technology. This advanced transformer less solution, using the MM7 drive, offers high performance with a flicker mitigation ratio up to 6.0 –a strong asset over competition that allowed GE to be selected for this project.

Scope of supply

• MM7 STATCOM 20 kV/from -49MVar to +121 MVAr
• 3 phases, each constituted by 5 towers
• Engineering, delivery, supervision of erection and commissioning

The equipment has been delivered at the end of 2022 and started operating in March 2023. It was then successfully tested in April 2023.

Looking at the future

In a near future, MSM intends to change the plant’s bus voltage from 20 kV to 33 kV – a grid expansion that GE Power Conversion already anticipated and will therefore easily be implemented by adding 2 towers per phase to the MM7, thanks to the high flexibility of the solution.

Benefits

Despite a relatively low grid quality factor (X/R) and short-circuit level, Power Conversion's solution achieved a flicker reduction above 5, hence meeting the customer's expectations. 

About the project

In 2018, GE Electrification was awarded a contract by Elecnor Spain to supply the Static Synchronous Compensator (STATCOM) solution for the Electrical Balance of Plant (EBoP) of a wind farm developed in Jordan by Mass Energy Group Holding, a subsidiary of Mass Global.

This 100 MW wind facility, located in Al-Tafila Governorate, about 130 km south of the capital Amman, entered successfully into operation at the beginning of 2020.

It is the first renewable energy project by Mass Energy Group Holding.

This development fell within the Jordan 2025 Vision and Strategy, a plan which aims at increasing the share of renewable energy in the total energy mix to 11% and boost domestic energy production. The Mass Energy wind farm has been developed to power around 150,000 homes and reduce carbon emissions by 233,800 metric tons annually.

The Grid Stability Challenge

Maintaining grid stability and voltage control is necessary especially in today’s world where the evolving power generation scene has become even more challenging for Transmission System Operators – a larger share of renewables, retirement of base-load plants, increased environmental regulation and greater cross-border trading are all making grid stability more complex.

To maintain reliability and quality of power supply in this environment, economical and efficient solutions are needed to provide dynamic voltage support and fast reactive power compensation. By selecting GE Electrification’s STATCOM systems to equip the EBoP, Mass Energy and Elecnor made the choice of a proven technology.

Our Solution

The STATCOMs are power electronics-based power quality devices which ensure dynamic voltage control and increased power transfer capability. They are based on our proven range of Voltage Source Inverters with demonstrated proficiency in energy and industrial applications.

A STATCOM offers a strong dynamic performance, especially a fast response time as well as the ability to generate or absorb reactive power during Fault Ride Through. It therefore helps increase reliability and availability of grid operation. For the Mass wind farm in Tafila, GE Electrification’s scope of work included the development, supply, supervision of erection & commissioning of two 19 MVAr STATCOM systems based on GE’s MV7000 inverter technology.

This solution allows an overload capacity of 300% during 500 milliseconds during the Low Voltage Ride Through.

It enables to solve the quality issues on the grid during operations and can then help improve grid reliability and avoid significant upgrade costs for grid connections.

STATCOM Key Features

• Valve based on IGBT press-pack technology
• Heavy duty solution to allow installation in very harsh remote areas
• Current range up to 300%/500 ms
• Very high availability with N-1 redundancy
• Stepless adjustable cos phi
• Transformer to connect to high voltage grid
• Water cooled through Air/Water exchanger
• Air-conditioned
• Controls based on industry standard components
• Containerized solution to allow very fast installation
• Reduced footprint