Solid-State Transformer (SST) vs. Traditional Power Transformer: Core Differences

Also known as: In the industry, the Solid-State Transformer is commonly referred to as the Power Electronic Transformer (PET).

1. What Is a Solid-State Transformer (SST)?

Traditional power transformers operate on the principle of electromagnetic induction, converting AC power from one voltage level to another. They are structurally simple and technologically mature, but their functionality is relatively fixed.

Solid-State Transformers (SST) employ a multi-stage power electronic conversion topology, typically following the path AC → DC → high-frequency AC → DC/AC:

2. Core Technological Foundations of SST

The realization of SST depends on the maturity of power electronics technology and wide-bandgap semiconductor devices, notably:

• Silicon Carbide (SiC)
• Gallium Nitride (GaN)

Compared with conventional silicon-based devices, wide-bandgap devices offer higher voltage ratings, higher switching frequencies, and lower losses, enabling SST to achieve:

• Higher-frequency energy conversion (several kHz to tens of kHz)
• Drastic reduction in magnetic component and high-frequency transformer volume
• Millisecond/microsecond-level dynamic response
• Flexible active control of voltage, current, and power

Key point: The SST is not merely an "electronic version" of a traditional transformer; it replaces part or all of the power-frequency transformer's functions with a semiconductor-based conversion system.

3. Core Differences: SST vs. Traditional Power Transformer

In one sentence:
A traditional transformer is a passive voltage conversion device based on electromagnetic induction;
An SST is an active electrical energy control device based on power electronic conversion.

4. Summary

The Solid-State Transformer (SST) is not a simple upgrade of the traditional power transformer; it is a new type of electrical energy conversion device based on power electronics technology.

The core differences are:

• Traditional power transformers rely on electromagnetic induction to perform power-frequency AC voltage conversion. They are structurally simple, technologically mature, but functionally fixed.
• Solid-State Transformers (SST) leverage semiconductor power devices and high-frequency conversion technology to simultaneously achieve voltage conversion, rectification, inversion, DC-DC conversion, and power control — delivering greater functionality, smaller footprint, and more flexible control.

Edited From：Echo