The Solid-State Shift: Reinventing the Transformer for Modern Grids

I have a question for people more familiar with these. What exactly happens at the isolation stage. They say it includes a high frequency transformer (HFT). But its input and out put is DC. And classic transformers operate on AC. So in order to get the transformer working, one would have to chop up the incoming dc power into a square wave or a sine wave. But what transistors can you use to do this, considering you are dealing both with very high power and very high frequencies?

No, I'm not joking. For these kinds of voltages, you need to use highly homogenous doped silicon, and the only way to produce it is to irradiate silicon with neutrons. It transmutes some of the silicon atoms into phosphorus: https://nrl.mit.edu/facilities/ntds/

And doping during crystal growth doesn't produce homogenous enough silicon.

It's apparently possible for boron doping.

I think because phosphorus is bigger than silicium you'll get too many defects in the crystal, while with the smaller boron it is not an issue.

You can stack power transistors to switch higher voltages on the primary side. On the secondary side you just need an H-bridge. Which can be made up of transistors in parallel.

We've had high power high voltage transistors for about 40 years now. A lot of this isn't technical but rather economic. As the price falls the applications where they are cheaper increases. It's notable for instance Toyota started work on their hybrid drive in the mid nineties when inverters for 10-100 HP motors became cheap enough.

[1] https://en.wikipedia.org/wiki/Switching_power_supply