Enhancing solid-state transformer performance with SiC power modules

Solid-state transformers (SSTs) are among the most demanding applications in power electronics. An SST must isolate, convert, and regulate power across wide input voltage ranges – at high switching frequencies, high junction temperatures, and in physical envelopes far smaller than the conventional line-frequency transformers they replace. Silicon cannot meet all of these requirements simultaneously at grid-relevant power levels. Silicon carbide (SiC) can.

Whether you are designing AI data center infrastructure, renewable energy systems, EV charging stations, or industrial power conversion equipment, choosing the right SiC modules can significantly improve overall SST performance.

What is a solid-state transformer (SST)?

A solid-state transformer (SST) is a power electronic transformer that replaces the traditional line-frequency transformer with high-frequency power converters and a compact high-frequency transformer.

How does a solid-state transformer work?

A solid-state transformer replaces a bulky, low-frequency transformer with a power electronics-based conversion chain. A canonical SST converts power through three main stages:

1. AC/DC converter rectifies the incoming AC voltage into DC

2. Isolated DC/DC converter transfers energy through a high-frequency transformer, providing galvanic isolation while significantly reducing transformer size 

3. DC/AC inverter delivers regulated DC power directly to DC loads or converts it to AC when required, enabling precise voltage regulation, bidirectional power flow, and advanced grid control

Operating these stages at high switching frequencies is what allows SSTs to achieve much higher power density than conventional transformers.

Why are SiC modules ideal for solid-state transformers?

Each of the three stages of an SST switches at frequencies with an order of magnitude higher than grid frequency (typically 10 kHz to over 100 kHz).

At these frequencies and at medium-voltage grid inputs (3.3 kV, 6.6 kV, 10 kV, 13.8 kV, 22 kV, 35 kV), silicon IGBTs reach their practical limits. As frequency increases, switching losses rise, and at 20 kHz and above, IGBT tail current losses become prohibitive.

Silicon MOSFETs do not support the required blocking voltages. SiC MOSFETs operating in the 1200 V to 3300 V class are the only commercially mature device technology that simultaneously supports the blocking voltage, switching frequency, and junction temperature demands of medium-voltage SST designs.

This is why solid-state transformers are identified as one of the major future grid opportunities for high-performance SiC power conversion – and why SiC module selection directly determines system-level performance outcomes.

How do SiC modules improve solid-state transformer performance?

Build smaller and lighter transformers

One of the biggest advantages of SST technology is the replacement of bulky, low-frequency magnetic components with high-frequency converters.

Because SiC modules switch much faster than conventional silicon devices, designers can:

●          Reduce transformer core size

●          Minimize passive component sizes

●          Decrease cooling requirements

●          Increase overall power density

The result is an SST that is significantly smaller and lighter than a conventional transformer while delivering equivalent or greater power.

By leveraging Infineon’s SiC technology, DG matrix’s Interport™ multi-port solid-state transformer platform achieves a compact design that is smaller and lighter than conventional transformers.

Increase system efficiency

Every conversion stage inside an SST contributes to total system losses.

SiC modules help minimize these losses through:

●          Low switching losses

●          Low conduction losses

●          Fast switching characteristics

●          Reduced reverse recovery losses

Higher efficiency translates into:

●          Lower operating costs

●          Reduced energy waste

●          Improved overall system reliability

●          Better performance under continuous operation

SolarEdge is collaborating with Infineon to develop a modular 2–5 MW solid-state transformer platform, targeting over 99% efficiency through advanced SiC-based power conversion.

Simplify thermal management

Heat is one of the primary design challenges in high-power conversion systems.

Because SiC modules generate less heat during switching, SST designers benefit from:

●          Lower cooling requirements

●          Smaller heatsinks

●          Reduced cooling system weight

●          Higher power output from the same enclosure

This makes compact SST designs more practical for space-constrained installations.

Enable higher switching frequencies

Higher switching frequencies are essential for reducing the size of transformers, inductors, and filters.

SiC modules enable stable operation at frequencies that are difficult to achieve efficiently with conventional silicon devices.

Benefits include:

●          Smaller magnetic components

●          Faster power regulation

●          Improved dynamic response

●          Higher overall power density

Improve reliability in demanding applications

SSTs often operate in demanding environments such as:

●          Gigawatt-scale datacenters

●          Renewable energy integration

●          Railway traction

●          Fast EV charging infrastructure

●          Smart grid substations

●          Industrial power distribution

SiC modules are well suited for these applications because they offer:

●          High-voltage capability

●          Robust thermal performance

●          Excellent switching reliability

●          Long operational lifetime

How to choose the right SiC module for your SST design?

Selecting the appropriate SiC module depends on several design considerations:

  • System voltage
  • Power rating
  • Switching frequency targets
  • Medium or high frequency transformer design strategy
  • Thermal management strategy
  • Efficiency requirements
  • Mechanical integration
  • Reliability expectations

Optimizing these parameters together helps maximize SST performance while reducing system size, weight, and total cost of ownership.

What are the system-level benefits of SiC modules in SSTs?

Rather than improving only individual power devices, SiC modules enhance overall system performance.

Infineon’s CoolSiC™ modules for SST

Infineon's CoolSiC™ MOSFET module portfolio covers the 750 V, 1200 V, 2300 V, and 3300 V classes in EasyPACK™, with trench-gate cell architecture that delivers industry-leading
RDS(on) × QG figures for the lowest combined conduction and switching loss in SST power stages.

Key CoolSiC™ module features relevant to SST design:

  • Trench gate architecture: lower gate charge and switching losses versus planar SiC alternatives
  • Kelvin source connection: decoupled power and gate return paths for faster, more controlled switching in high-frequency SST stages
  • High isolation voltage ratings: suitable for medium-voltage SST grid interface requirements
  • Compatible with Infineon EiceDRIVER™ gate driver ICs, optimized for SiC gate drive requirements including negative turn-off bias and short-circuit protection

Advantages of EasyPACK™ CoolSiC™ MOSFET modules for SST:

  • CoolSiC™ MOSFET 750 V, 1200 V, 2300 V, and 3300 V
  • Supporting 400 VDC, ± 400 VDC and 800 VDC grids as well as 10 kV to 35 kV AC connection
  • Reliable, powerful, and efficient technology
  • Well-proven and established package platform
  • Excellent PPM rates and qualification standards
  • Leading production (front-end and back-end)
Explore CoolSiC™ Modules for SST Power Stages

Frequently asked questions about SST

1. Why are SiC modules used in solid-state transformers?

SiC modules support higher switching frequencies with lower losses than conventional silicon devices. This enables smaller transformers, higher efficiency, reduced cooling requirements, and greater power density.

High-frequency switching allows designers to reduce the size of transformers, inductors, filters, and cooling systems, resulting in a significantly more compact overall design.

The primary benefits include higher efficiency, lower system weight, higher power density, improved thermal performance, faster switching, and increased reliability.

Gigawatt-scale datacenters, smart grids, renewable energy systems, EV charging infrastructure, railway traction, industrial power conversion, and microgrids all benefit from the performance advantages of SiC-enabled solid-state transformers.

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