The conventional transformer is a marvel of simplicity — but it is passive, heavy, and offers no control beyond changing voltage. As grids fill with solar, EVs and batteries, operators want active, controllable transformers. The Solid-State Transformer (SST), sometimes called a power electronic transformer, delivers this by combining power electronics with a small high-frequency magnetic core.
Working principle
An SST first rectifies the incoming AC to DC, then an inverter converts it to high-frequency AC (kilohertz). This drives a compact medium-frequency transformer (MFT) for isolation and voltage change — higher frequency means a far smaller core. The output is rectified and inverted back to the desired AC (or kept as DC). Because every stage is actively switched, the SST can regulate voltage, correct power factor and expose DC ports.
| Property | Line-frequency transformer | SST |
|---|---|---|
| Frequency | 50/60 Hz | kHz (medium frequency) |
| Size / weight | Large, heavy | Compact, light |
| Control | Passive | Active V regulation, PF, fault |
| DC port | No | Native DC bus |
| Cost / losses | Low cost, robust | Higher cost, switching loss |
Why it mattersThe SST's killer feature for 2026 grids is the native DC bus: it directly interfaces solar, batteries and DC fast-chargers without extra conversion stages.
Applications
- Smart-grid distribution with integrated DC microgrids
- EV fast-charging hubs and traction power
- Renewable and storage interconnection with power-quality control
References & further reading
- Huber & Kolar, “Solid-State Transformers: On the Origins and Evolution of Key Concepts,” IEEE IES Magazine, 2016.
- She et al., “Review of Solid-State Transformer Technologies and Applications,” IEEE Trans. Power Electronics, 2013.
- Hannan et al., “State of the Art of Solid-State Transformers,” IEEE Access, 2020.