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