Solid-State Transformers Transitioning from AC to DC Power Grids to Meet Sustainable Energy Goals
Electricity grids around the world have been working with alternating currents (AC) for more than 100 years. However, the advancements in power electronics are making a new norm for power grids to shift to direct currents (DC).
The École Polytechnique Fédérale de Lausanne (EPFL) Research Institute, Switzerland, has developed a compact medium-frequency transformer that is efficient and works on DC power distribution networks. This device enhances the flexibility and efficiency of smart grids while considering several sustainable steps to reach energy goals.
This article will explain solid-state transformers that are manufactured to transition from AC to DC electricity grids.
What are solid-state transformers?
A solid-state transformer (SST) is the assembly of power semiconductor components, control circuitry, power converters, and high-frequency transformers.
A solid-state transformer has various applications, such as smart grids, EV charging stations, traction locomotives, and renewable power integration.
SST has several features, such as flexible control over the power distribution network, reduced size and cost, power factor correction, high efficiency, and reactive power compensation, high power density.
Solid-state transformers serve as the building blocks of smart grid infrastructure. As per the application, SSTs are able to transfer power bidirectionally and scale down and scale up voltages.
Moreover, to meet the future demand for smart grid infrastructure, potential companies that were conventionally manufacturing transformers are also taking a core interest in the research and development (R&D) of solid-state transformers.
How does a solid-state transformer power grid work?
Today, most appliances run on DC, such as computers, light-emitting diodes (LEDs), and even electric cars. The purpose of a solid-state transformer is to step-up or step down the current, that is, to convert AC to DC, functioning the same as a conventional transformer.
Solid-state transformers use devices based on semiconductors, transistors, and diodes that can handle fast switching and high-power levels. As soon as these utilities start to roll out the smart grid, they gather important information, such as up-to-the-minute electricity usage measurements from smart meters installed at homes and businesses. With the progress of the smart grid, solid-state transformers adjoin to strengthen the control over power flows through the lines.
Some basic requirements of SST are:
- Transformer oil that wouldn’t react when exposed to the environment.
- Core saturation of harmonics to gain in large inrush currents.
- Voltage dips to represent the output waveform.
- A voltage regulation capability transformer.
EPFL researchers developed medium-frequency transformers (MFTs) that are optimally designed to enable one of the key technologies for SSTs. This MFT prototype is rated 100kW when operated at 10kHz. These MFTs serve the basic need for industrial use of transformers to convert current not only from AC to DC but AC-AC, DC-DC, and DC-AC.
The significant advantages of SSTs over conventional transformers are:
- Instantaneous voltage compensation
- Voltage Sag compensation
- Fault isolation
- Outage compensation
- Harmonic isolation
- Metering or advanced distribution automation
- DC Output
- Power factor correction (and reactive power compensation)
How are solid-state transformers affecting the market?
Compared to conventional transformers, a solid-state transformer is a highly efficient power transformer. Thus, in coming years, the solid-state transformer market is expected to receive a rise in investments in smart grid, renewable power expansion, and others to generate higher revenue products.
Moreover, agreements, acquisitions, partnerships, and collaborations among key players are a comprehensive competitive strategy to aid the untapped revenue generation in the solid-state transformer market.
According to a report by BIS Research, the global solid-state transformer market is expected to value $207.3 million in 2025 and is projected to reach $467.0 million in 2031, following a CAGR of 14.34% during the forecast period 2026–2031.
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Moreover, the growth in the global solid-state transformer market is expected to be driven by an investment rise toward the construction of power transmission and distribution networks, charging station infrastructure, and EV renewable power generation across the globe.
Conclusion
High-voltage DC is proven to be an efficient method for transporting power over large distances, but the interconnection still requires legacy AC grids. To achieve sustainable DC grids in the future DC grids, facilitating the smart grid concept, further technological advancements are required to progress in transformers.
This transition requires power electronic conversion devices that are flexible, efficient, and enabled with high performance. Solid-state transformers are the most common and preferred choice in the energy sector.
