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Run your analysis now →https://www.patsnap.com/resources/blog/rd-blog/voltage-sag-and-interruption-immunity-patent-landscape/ · Patsnap · data cut-off 2026-07-31 · downloaded from the live page
Power Quality · Patent Landscape 2026Voltage sag and interruption immunity patents: who holds ride-through claim space
- Top 5 assignees hold 50.6% of the field. 39 of the 77 records in scope sit with just five companies, with a leader at 14 filings and a long tail below that.
- Filing has been flat, not falling. 2021 to 2024 filings held at 2 to 2 — 0% growth over that span — while 2025-2026 figures are still filling in under normal publication lag.
- H02J and H02M dominate; F03D barely registers. Power supply/grid (45.5%) and power conversion (37.7%) cover most records, while wind-turbine-specific claims (F03D, 6.5%) remain thin.
77
Published Records
51%
Top-5 Share of All Records
0%
Filing Growth 2021→2024
CN
Leading Jurisdiction
Filing growth compares 2021 (2 records) with 2024 (2) — 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 77 records in scope (CR5), not by the ranked leaders only.
Published byPatsnap Research··8 min readSourced from Patsnap Eureka
Field Overview
What this patent landscape covers
Voltage sag and interruption immunity covers the detection, ride-through and compensation technology that keeps motor drives, chillers, grid equipment and power converters running through short-duration voltage dips. The search spans 77 published records filed against sag depth/duration detection, dynamic voltage restorers, ride-through control loops and related monitoring campaigns, with a coverage window from 2015 through the 2026-07-31 cut-off. Because the underlying documents mix HVAC compressor drives, grid-side compensation hardware and motor control loops, the IPC composition is genuinely cross-disciplinary rather than concentrated in a single subclass.
Assignee concentration is real but not absolute: the top 5 companies account for just over half of all records, and the top 10 reach three-quarters of the field, leaving a long tail of single- or double-filing entrants below that. Filing trended toward a 2018 peak and has since held at a modest, flat rate through the last complete year, which argues for entering underexplored claim territory rather than trying to out-file the incumbents on well-trodden ride-through control loop claims.
Filing activity and technology composition, 2017-2026
Source: Patsnap Eureka. Assignee ranking and totals. Derived from a Patsnap search on Voltage Sag and Interruption Immunity covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
The Numbers
Filing trend and technology composition
Two views of the same 77 records: how filing activity has moved year over year, and how the technology splits across IPC subclasses. Since a record can carry more than one IPC class, the composition shares are read against the full 77-record base and sum to more than 100%.
Filing trend, 2017-2026
Filings began at 1 in 2017, rose to a peak of 7 in 2018, and have since settled into a flat pattern — 2 filings in 2021 and 2 again in 2024, a 0% change over that three-year span. 2025 and 2026 figures will keep rising as publications catch up with roughly 18 months of filing-to-publication lag, so the most recent two years should not be read as a decline.
Technology composition by IPC subclass
H02J (power supply and grid systems) touches 45.5% of records and H02M (power conversion) 37.7%, together forming the technical core of most ride-through solutions. H02P (motor and generator control) and H02H (protective circuits) sit in the 14-18% range, G01R (measurement) and H01H (switches/relays) lower still, and F25B (refrigeration/heat pumps) and F03D (wind turbines) are the thinnest slices at 9.1% and 6.5% respectively — the latter despite wind generators being a natural ride-through use case.
Shares are the percentage of the 77 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Source: Patsnap Eureka. Filing trend and technology composition. Derived from a Patsnap search on Voltage Sag and Interruption Immunity covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.
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The most-cited records in this landscape
Representative Filing
US6686718B2 — Control loop and method for variable speed drive ride-through capability improvement
YORK INTERNATIONAL CORPORATION
A variable speed drive (VSD) having a rectifier, an inverter, an inverter modulator, an inverter controller, and a control loop, for controlling a motor load, wherein the control loop reduces an amount of power transferred to the inverter during a voltage sag. The control loop may include a reference generator, a filter, a regulator, and a ride-through corrective algorithm. A method for controlling a VSD to improve voltage sag ride-through by monitoring a voltage applied to the VSD, generating a control signal representative of losses in a motor load when a voltage sag is detected in the voltage applied to the VSD and applying less power to the load of the inverter.Filed by York International Corporation, granted 2004-02-03; cited 78 times within this corpus, the second-highest count in the dataset.
Highest-citation records in scope
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US20120056602A1 | Control of a permanent magnet synchronous generator wind turbine | 116 |
| 2 | US6686718B2 | Control loop and method for variable speed drive ride-through capability improvement | 78 |
| 3 | US20070151272A1 | Electronic control transformer using DC link voltage | 59 |
| 4 | US20070063668A1 | A ride-through method and system for HVAC&r chillers | 52 |
| 5 | US7081734B1 | Ride-through method and system for HVACandR chillers | 52 |
| 6 | US20030098668A1 | Control loop and method for variable speed drive ride - through capability improvement | 48 |
| 7 | US7332885B2 | Ride-through method and system for HVAC&R chillers | 40 |
| 8 | US6847515B1 | Power supply systems and methods that can enable an electromagnetic device to ride-through variations in a su… | 30 |
| 9 | CN105842580A | 一种适用于智能配电网的电压暂降源精确定位优化方法 | 29 |
| 10 | US20060250105A1 | Variable speed drive for a chiller system with a switched reluctance motor | 28 |
Citation counts reflect influence inside this searched corpus and skew toward older filings; treat them as a marker of foundational status, not 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.
Source: Patsnap Eureka. Citation counts and representative records. Derived from a Patsnap search on Voltage Sag and Interruption Immunity covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
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What the filing pattern tells you
Three read-throughs of the same dataset: concentration, momentum and co-filing structure, each pointing at a different strategic question.
Concentration
50.6%
of 77 records held by the top 5 assignees
Ownership is top-heavy but not closed
The leader holds 14 filings and fifth place holds 4, a steep drop that signals one or two companies built genuine depth in ride-through control loops early, while the rest of the top 5 filed opportunistically. The top 10 combined reach 75.3% of all 77 records, meaning entrants outside that group are filing in the remaining quarter of the field almost one at a time.
Top 10 = 58 of 77 records
Momentum
0%
filing growth, 2021 to 2024
Flat, not declining, filing activity
The three-year comparison shows filings unchanged at 2 in both 2021 and 2024, after an early peak of 7 in 2018. That flatness — rather than a drop — is the honest read once you account for publication lag pulling down the last one to two years of any trend.
Peak year: 2018 at 7 filings
Co-filing
10
co-assignee pairs identified
Collaboration is narrow and recurring
Only 10 co-assignee pairs appear across the dataset, and the strongest pair recurs at a count of 4 with two related pairings at 3 each — all clustered around the same small group of named inventors and their corporate assignee. That pattern points to internal inventor-to-corporate filing relationships rather than broad industry co-development.
Strongest pair: 4 shared filings
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Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to voltage sag and interruption immunity, with the prior art for and against each one.
Where filing activity clusters
| Assignee | Co-assignee | Shared families |
|---|---|---|
| SCHNETZKA HAROLD R | JADRIC IVAN | 4 |
| Johnson Controls Technology Company | SCHNETZKA HAROLD R | 3 |
| Johnson Controls Technology Company | JADRIC IVAN | 3 |
| York International Corporation | SCHNETZKA HAROLD ROBERT | 2 |
| York International Corporation | COSAN MUHAMMET | 2 |
| State Grid Corporation of China | Jiangsu Fangtian Power Technology Co., Ltd. | 2 |
| State Grid Corporation of China | State Grid Fujian Electric Power Co., Ltd. Electric Power Research Institute | 2 |
| State Grid Corporation of China | State Grid Fujian Electric Power Co., Ltd. | 2 |
Co-assignee pairs concentrate around a small inventor group tied to one corporate assignee, rather than spreading across multiple companies — a sign of internal R&D teams rather than joint ventures.
Source: Patsnap Eureka. Co-assignee relationships and derived observations. Derived from a Patsnap search on Voltage Sag and Interruption Immunity covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
Competitive Landscape
Who holds the ground, and where it opens up
Fifty-nine assignees are ranked across this dataset, from a leader with 14 filings down to single-record entrants. Combined with the IPC breakdown, the ranking shows both where claim space is defended and where it is thin enough to enter.
Leader
14
records held by the top-ranked assignee
A clear leader, then a steep drop-off
The top assignee holds 14 of the 77 records in scope, more than three times fifth place at 4. That gap suggests a sustained filing programme rather than a single burst, likely built around the ride-through control loop and DVR technology visible in the most-cited records.
Fifth place: 4 records
Mid-field
3
records at tenth place
A crowded middle tier
Tenth place holds 3 records, meaning the gap between fifth and tenth place is comparatively shallow — several assignees are filing at a similar, moderate pace rather than one company running away with the field below the leader.
Top 10 = 75.3% of all records
Long tail
59
assignees ranked in total
Most entrants file once or twice
Outside the top 10, the remaining assignees split the last 24.7% of records among dozens of single- or double-filing entrants, including several Chinese grid-operator subsidiaries and university labs. That pattern is typical of a field where the core control-loop IP is settled but application-specific implementations keep attracting new filers.
24.7% of records held outside the top 10
Recent-year filing momentum
| Assignee | Recent year | YoY |
|---|---|---|
| York International Corporation | 0 | — |
| Johnson Controls Technology Company | 0 | — |
| State Grid Corporation of China | 0 | — |
| ZHONG QINGCHANG | 0 | — |
| Schneider Electric USA, Inc. | 0 | -100% |
| Sichuan University | 0 | — |
| North Carolina State University | 0 | — |
| SCHNETZKA HAROLD R | 0 | — |
Source: Patsnap Eureka. Assignee-level momentum. Derived from a Patsnap search on Voltage Sag and Interruption Immunity covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
Next Steps
Where to take this analysis
The dataset points to specific next questions depending on whether you are scoping freedom-to-operate, evaluating an acquisition target, or deciding where to file next.
Check freedom-to-operate on ride-through control loops
The most-cited records concentrate around VSD and chiller ride-through control loops filed by a small number of assignees. Before filing in that space, screen the leader's full portfolio rather than relying on the most-cited records alone.
Run a claim chart in EurekaScope the under-claimed branches
F03D wind-turbine ride-through and sag-source-location diagnostics show materially lower IPC density than the H02J/H02M core, which is the profile of genuine white space rather than a gap in the search.
Explore white space in EurekaTrack the flat filing trend for a turn
Filing held flat from 2021 to 2024 at 0% growth; watch the next one to two publication cycles to see whether that flatness breaks in either direction once the lag clears.
Set a monitoring alert in EurekaSource: Patsnap Eureka. Forward-looking reading of the same dataset. Derived from a Patsnap search on Voltage Sag and Interruption Immunity covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
FAQ
Common questions about this landscape
One assignee leads with 14 of the 77 records in scope, well ahead of fifth place at 4. The top 5 assignees combined hold 50.6% of all records, and the top 10 reach 75.3%, so ownership is concentrated but not closed — roughly a quarter of the field is split among a long tail of smaller filers. Reviewing the leader's full portfolio, not just its most-cited patents, is the right starting point for any competitive or freedom-to-operate analysis.
Filing activity peaked in 2018 at 7 records and has since settled to a flat rate, with 2 filings in 2021 and 2 again in 2024 — a 0% change over that span. The 2025 and 2026 figures in any dataset like this will look artificially low because publication typically lags filing by around 18 months, so those final years should not be read as a genuine slowdown. The honest read is flat, steady activity rather than growth or decline.
Power supply and grid systems (IPC H02J) appear in 45.5% of the 77 records, and power conversion (H02M) in 37.7%, making these two subclasses the technical core of most filings. Motor and generator control (H02P) and protective circuits (H02H) follow at lower shares, while measurement (G01R) and switches/relays (H01H) are thinner still. Because a single record can carry multiple IPC codes, these shares add up to more than 100% and should be read as overlap, not a strict breakdown.
Wind-turbine-specific ride-through (F03D) appears in only 6.5% of records and refrigeration/chiller ride-through (F25B) in 9.1%, both well below the H02J and H02M core. Sag-source-location diagnostics and compensation-energy optimisation for dynamic voltage restorers also show comparatively light claim density relative to the core control-loop art. These are reasonable areas to screen first for a first-to-file position, though a proper freedom-to-operate check should confirm density before committing claims.
US6686718B2, assigned to York International Corporation and granted in 2004, claims a control loop for a variable speed drive that reduces power transferred to the inverter during a voltage sag, using a reference generator, filter, regulator and ride-through corrective algorithm. It is cited 78 times within this corpus, the second-highest citation count in the dataset, which marks it as one of the foundational documents in the field. Anyone designing a motor-drive ride-through control loop should review its claim scope directly rather than relying on citation count alone, since high citation reflects influence within this searched set, not current freedom-to-operate risk.
Answers are grounded in the same dataset. Derived from a Patsnap search on Voltage Sag and Interruption Immunity covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
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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.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
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.