A solid-state transformer (SST) replaces the single iron core and copper winding of a conventional transformer with power-electronic conversion stages — typically a dual active bridge operating at high frequency through a smaller, lighter isolation transformer. In patent terms this shifts the claim territory from magnetics and winding geometry (IPC H01F) toward power conversion and control (H02M, H02J). This dataset shows only 6 of 178 families in H01F, confirming that most SST patenting activity is now in switching and control claims rather than core transformer hardware.

Filing in this corpus is concentrated among Chinese grid operators and their affiliated research institutes, alongside global power-electronics vendors such as ABB. The strongest collaborative filing pattern pairs a national or regional grid operator with its own research institute or supply bureau, with the top pairs co-filing 6 times each. Recent-year momentum diverges from historical volume, however — several of the largest historical filers show zero filings in the latest tracked year while ABB continues to add filings.

No — filing peaked in 2021 at 27 families and had fallen back to 4 by 2022, with the partial 2026 count also at 4. This points to a filing cycle that already crested rather than one still accelerating, though publication lag of roughly 18 months means the most recent one to two years are always undercounted at the time of measurement. A realistic read treats the 2021 cohort as the field’s high-water mark for now.