Solid-State Transformer Patents: Who Leads, Where the Gaps Are 2026
- Filing peaked in 2021 at 27 families, then fell back toward the 2017 level of 8 — the technology's patenting cycle has already crested, not accelerated.
- China accounts for 114 of 178 families, more than four times the next-largest receiving office, the United States at 25.
- Grid and control-side IPC codes now outweigh core H01F transformer hardware, with H02M and H02J combined dwarfing the 6 families classified under magnetics and inductors.
Filing growth compares 2021 (27 records) with 2024 (24) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 178 records in scope (CR5), not by the ranked leaders only.
What the filings actually cover
Solid-state transformer (SST) patenting sits at the intersection of power conversion and grid architecture rather than classical transformer hardware. The search set spans dual active bridge topologies, high-frequency link isolation, and medium-voltage control schemes, filtered against IPC classes for power conversion (H02M), grid supply systems (H02J) and magnetics (H01F). Only 6 of 178 families sit in H01F, the classical transformer-hardware class — the bulk of activity is in how the power electronics switch and control the isolated stages, not in the magnetic core itself.
That composition matters for filing strategy: a design that changes control-loop behaviour or module-level voltage balancing is more likely to run into occupied claim space than one that changes core or winding construction. Publication lags filing by roughly 18 months, so the 2026 count of 4 understates true recent activity; the more reliable signal is the decline from the 2021 peak of 27 through the 2022 midpoint of 4.
Filing trend and technology composition
178 patent families published between 2015 and mid-2026, classified by filing year and by IPC subclass, show where drafting effort has concentrated and where it has pulled back.
A 2021 peak, then a pullback
Annual filings rose from 8 in 2017 to a peak of 27 in 2021, then dropped sharply — 2022 sits at 4, and 2026 (partial) shows 4. This is not a young, accelerating field; it is one that had a filing surge around 2020-2021, plausibly tied to grid-modernisation programmes, and has since cooled. Any competitive read of this space should weight the 2021 cohort heavily rather than assume steady linear growth.
Power conversion and grid codes dominate
H02M (power conversion, 125 records) and H02J (power supply and grid systems, 108 records) between them cover almost all of the corpus, with heavy overlap — most SST families touch both. H01F (transformers and magnetics, 6), B60L (EV propulsion, 4), G06F and G06Q (data processing, 4 each), G01R (measurement, 3) and G05B (control systems, 3) are thin tails, each pointing to a specific integration angle — EV charging, monitoring software, or closed-loop control — that has not yet drawn concentrated filing.
Shares are the percentage of the 178 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Solid-State Transformer Technology with Eureka
This page is one run against one query. Ask Eureka your own question about solid-state transformer technology and every answer comes back with the patent numbers behind it.
Try EurekaThe documents other filings build on
US20190312521A1 — Dual voltage and current loop linearization control and voltage balancing control for solid state transformer
Filed by Nanyang Technological University, this record claims a control method that divides a dual active bridge (DAB) power reference across N DAB modules, then corrects per-module capacitor voltage deviation on the high-voltage DC bus through a current-adjustment signal derived from the total reference current and each module's measured deviation.Abstract condensed from the published filing; see the full record for complete claim language.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US5943229A | Solid state transformer | 83 |
| 2 | CN104852406A | 基于电力电子变压器的混合微网系统及功率控制方法 | 60 |
| 3 | US20190312521A1 | Dual voltage and current loop linearization control and voltage balancing control for solid state transformer | 37 |
| 4 | CN204013248U | 一种基于LLC谐振变换器的电力电子变压器 | 34 |
| 5 | CN110690731A | 一种适用于混合微电网的电力电子变压器及其协调控制和模式切换方法 | 28 |
| 6 | CN102064712A | 一种基于简易PFC的电力电子变压器 | 27 |
| 7 | CN108306517A | 两级式多端口电力电子变压器的拓扑结构及其控制方法 | 26 |
| 8 | CN110034572A | 含多端口电力电子变压器的交直流混合系统储能配置方法 | 22 |
| 9 | CN106655794A | 一种电力电子变压器及其控制方法 | 21 |
| 10 | CN105932883A | 基于能量注入式直接AC-AC变换器的电力电子变压器 | 21 |
Citation counts favour older, earlier-filed documents in any searched corpus — read them as markers of influence on later drafting, not as a ranking of current commercial relevance.
Patent titles are shown in the language they were filed in, not translated, so that each record stays verifiable against the original filing — a translated title will not match in Eureka or in any national register. Each row carries its publication number; clicking a row searches Eureka by that number.
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Three patterns stand out once filing volume, geography and citation weight are laid side by side.
Filing is concentrated in one jurisdiction
China's receiving office accounts for 114 of the 178 families, versus 25 for the United States and single digits for India, the EPO, WIPO and Canada combined. A freedom-to-operate check that skips Chinese-language filings misses the majority of the art in this field.
The surge has already passed
Filings peaked at 27 in 2021 and fell to 4 by the 2022 midpoint, with 2026 (partial) also at 4. Treat this as a field that consolidated its core claims in one concentrated window rather than one still building toward a peak.
Foundational claims sit two decades back
The most-cited record in the corpus, US5943229A, was filed well before the 2021 surge — its citation count reflects age and centrality to the term "solid state transformer" itself, not current filing activity. Newer high-citation records like US20190312521A1 concentrate on DAB control rather than basic topology.
Filing is often institutional, not solo
The strongest co-assignee links pair a national grid operator with its own research institute or a regional supply bureau — a pattern consistent with utility-driven rather than pure-vendor R&D in the Chinese filings.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to solid-state transformer technology, with the prior art for and against each one.
| Assignee | Co-assignee | Shared families |
|---|---|---|
| State Grid Corporation of China | State Grid Smart Grid Research Institute Co., Ltd. | 6 |
| Guangdong Power Grid Co., Ltd. | Guangdong Power Grid Co., Ltd. Dongguan Power Supply Bureau | 6 |
| State Grid Corporation of China | Xuji Group Co., Ltd. | 5 |
| State Grid Corporation of China | Xuji Electric Co., Ltd. | 5 |
| State Grid Corporation of China | State Grid Beijing Electric Power Company | 4 |
| State Grid Smart Grid Research Institute Co., Ltd. | State Grid Beijing Electric Power Company | 4 |
| State Grid Corporation of China | Xi'an Xuji Power Electronics Technology Co., Ltd. | 3 |
| State Grid Corporation of China | State Grid Liaoning Electric Power Co., Ltd. Anshan Power Supply Company | 3 |
The strongest co-assignee pairs link a grid operator to its affiliated research institute or regional supply bureau, suggesting these filings originate from joint utility R&D programmes rather than single-company labs.
Who holds the ground, and who is still moving
Recent-year momentum diverges sharply from historical filing volume: several of the largest historical filers show zero activity in the latest tracked year, while at least one global player continues to add filings.
ABB keeps filing while others pause
ABB (Switzerland) shows 2 filings in the latest year, making it one of the few assignees still active while several historically prolific Chinese filers, including the State Grid Corporation of China and its Smart Grid Research Institute, show 0 filings in the same period.
The largest historical filer has gone quiet
State Grid Corporation of China's filing count dropped to zero in the latest year, a -100% year-on-year change from its prior activity. That does not necessarily mean disengagement — it is consistent with the broader post-2021 pullback across the whole corpus.
Grid operators file jointly with their own institutes
The strongest co-assignee pairing — State Grid Corporation of China with its Smart Grid Research Institute — appears together 6 times, matched by a similar pairing between Guangdong Power Grid and its Dongguan supply bureau. These are structural, recurring collaborations rather than one-off joint ventures.
| Assignee | Recent year | YoY |
|---|---|---|
| ABB (Switzerland) Ltd. | 2 | — |
| Huawei Digital Power Technologies Co., Ltd. | 0 | — |
| State Grid Corporation of China | 0 | -100% |
| Southeast University | 0 | — |
| State Grid Smart Grid Research Institute Co., Ltd. | 0 | — |
| Guangdong Power Grid Co., Ltd. | 0 | — |
| ABB Power T&D Co., Ltd. | 0 | — |
| Hunan University | 0 | — |
Where to take this next
The dataset points to specific follow-up work depending on whether the goal is freedom-to-operate, licensing, or new filing strategy.
Run a freedom-to-operate check weighted toward China
With 114 of 178 families filed through China's receiving office, an FTO review that treats the US and EPO as primary will miss the majority of the art. Prioritise Chinese-language claim review before finalising a DAB control or medium-voltage isolation design.
Explore assignee filings in EurekaReassess timing assumptions before committing R&D spend
The 2021 peak of 27 filings followed by a drop to single digits suggests the core topology and control claims are already staked out. New entrants are better placed targeting the thinner IPC branches — B60L, G06F, G01R, G05B — than re-filing on core DAB topology.
Map white space in EurekaTrack ABB's continued filing against the quieter Chinese incumbents
ABB's continued activity in the latest year, against zero activity from several of the largest historical Chinese filers, is worth monitoring for signs of a shifting competitive centre of gravity.
Set up momentum alerts in EurekaCommon questions about solid-state transformer patents
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.
China's receiving office accounts for 114 of the 178 families in this corpus, more than four times the United States total of 25, with India, the EPO, WIPO and Canada each in single digits. Any freedom-to-operate or licensing review that does not examine Chinese-language filings directly is reviewing a minority of the relevant art. This is particularly important for grid-operator-driven filings, which cluster heavily in China.
US20190312521A1, filed by Nanyang Technological University, claims a control method for balancing per-module capacitor voltage across N dual active bridge modules on the high-voltage DC bus of a solid-state transformer, using a current-adjustment signal derived from deviation measurements. It is one of the more heavily cited recent records in this corpus, reflecting its relevance to modular DAB control architectures rather than basic SST topology. Anyone designing multi-module DAB voltage-balancing logic should review its full claim set closely before finalising a control scheme.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
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Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.