Anyone who wants to connect a data center, an electric vehicle charging station, a wind or solar farm, or a large-scale battery storage system to the power distribution grid needs a transformer. This is because high-voltage grids operate at voltages of several tens of thousands of volts. So-called Solid State Transformers (SSTs) are increasingly being used, which promise several advantages compared to conventional transformers with ton-heavy magnetic cores and copper windings.

For the AI data centers that are currently springing up like mushrooms, short delivery times are particularly important. Only a few specialized manufacturers such as ABB, General Electric, and Hitachi produce multi-megawatt high-voltage transformers – and have delivery times measured in years.

SSTs, on the other hand, are available faster, and more and more providers are entering the market. But SSTs promise even more advantages.

SST Technology

An SST can be roughly described as a gigantic switched-mode power supply. It contains high-power semiconductor switches such as silicon carbide transistors (SiC) or IGBTs, which operate at higher frequencies than the mains frequency and can be controlled dynamically. Due to the higher frequencies, smaller transformers are sufficient for the same power output. Thanks to the control capability, SST modules can be interconnected for higher total power.

SSTs can couple grids with different frequencies or feed directly from the medium-voltage grid into high-voltage direct current grids (HVDC with 800 volts), which are also advantageous for AI data centers. SSTs are also beneficial for high-voltage direct current transmission (HVDC), which is used for underground and subsea cables, for example.

Battery storage systems for bridging power failures (UPS) or for intermediate storage of cheap electricity during off-peak hours are also said to be easier to connect with SSTs. Some SST manufacturers therefore also call the technology “Power Router”.

However, SSTs are also used in electric locomotives, for example. They are more compact and lighter than magnetic core transformers, can be designed for different railway power systems in different countries, and can directly forward single-phase power fed in at, for example, 16.67 Hz to three-phase motors.

SST Arms Race

The EU project TIGON uses a 150 kW Solid State Transformer (SST) for coupling to a 3 kV grid.

(Image: TIGON)

The demand for powerful transformers for power distribution grids is currently skyrocketing. The AI boom is fueling the construction of many new data centers. The Stargate site in Abilene, Texas is expected to consume more than 5 gigawatts in its final configuration, which is approximately the power demand of Austria. The energy transition towards wind power and photovoltaics requires more connection points and additional power lines, as well as battery storage systems. In addition, there are powerful charging stations for e-cars and soon also trucks (Megawatt Charging System/MCS).

Today, Infineon, a manufacturer of SiC transistors, among other things, announced an SST cooperation with the photovoltaic company SolarEdge.

In August, Eaton, a company specializing in energy distribution systems, announced the acquisition of Resilient Power Systems. The latter manufactures particularly compact SSTs for car charging stations.

In March, ABB acquired a stake in DG Matrix. The North Carolina-based company builds modular 200 kW converters, primarily for AI data centers.

The EU is funding, for example, the SSTAR project for SSTs as well as TIGON for their use in microgrids.

(ciw)

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This article was originally published in German. It was translated with technical assistance and editorially reviewed before publication.