February 27, 2025
Challenge
The customer required a converter station capable of converting the energy from a public 220 kV 50 Hz grid to a level required for the railway-operated 110 kV 16.7 Hz distribution grid. The key objectives of the project were to achieve the highest conversion efficiency, reliability and system availability at the lowest possible cost.
System overview
The Mannheim station consists of a single independent converter block. It connects to the 220 kV 50 Hz 3-phase grid through an oil-immersed transformer (ONAN cooling system) and feeds the German Railway owned and operated 110 kV 16.7 Hz single phase distribution network via a step up single phase transformer.
Converter system
The power part of the converter block consists of one converter system based on the proven MV 7000 converter type. The converter is rated at 150 MVA and is located in a single building. A single converter includes 3 x 5 medium voltage inverter units, each with the following main components:
- An input 3-phase pulse controlled sub-inverter
- A DC link with a 33.4 Hz filter
- An output 1-phase 4QS sub-inverter
The core components in each sub-inverter are the press-pack IGBT modules organised in two phase-segments and fitted with a patented pull-out mechanism including the IGBT control amplifiers.
Providing the interface to the distribution grid
Cooling system
The converter block has its own dedicated cooling system with a mix of glycol and water. The power electronics as well as other components of the inverter units are directly cooled with this fluid. The advantage here is compact design and small space requirements. The heat is then dissipated in a water-air heat exchanger. Two water pumps are installed (100% redundancy) to provide continuous circulation. All systems are monitored and the pumps are switched over every 24 hours. To reduce the space required, the heat exchangers are located on the roof of each converter block.
Additional air-conditioning is provided for the house premises.
Control system
Internal converter control enables the following operation modes:
- Standard control in all 4 quadrants (according to the P/f, Q/U characteristic)
- Phase shift operation (supply of reactive power to the railway grid only)
- Parallel operation with rotary frequency converter
- Black Start-Up of rail grid
The control system allows for either local or remote operation via a user-friendly HDM interface.
Our SFC technology brings multiple advantages to the operator
Static frequency converter for railway application
