Filing in this corpus is concentrated among Chinese grid-research institutions and universities, alongside established international converter-equipment makers such as ABB and General Electric's technology entities. The strongest documented collaboration pairs a Southern Power Grid research institute with its parent company at 20 shared filings, and a university with State Grid Corporation at 12, indicating that institutional research partnerships rather than single corporate labs drive much of the recent volume. Several of the largest historical filers, including State Grid Corporation itself, show zero filings in the most recent year, so cumulative rank and current momentum tell different stories.

No — filing peaked at 67 families in 2018, held around 59 in 2017, and had fallen to 36 by the 2022 midpoint before dropping further toward the partial 2026 count of 8. That trajectory points to a flat-to-declining filing environment rather than an expanding one, though the last one to two years are always undercounted because publication lags filing by roughly 18 months. Read the 2025-2026 figures as a floor rather than a definitive endpoint.

China is the dominant receiving office by a wide margin, with 401 of 949 families filed there against 163 at the EPO, 119 at the USPTO, and smaller counts through WIPO's PCT route, Canada and Germany. A filing strategy or competitive search limited to US or European offices alone would miss the majority of documented activity in this field. Where a design targets Chinese grid deployment specifically, CNIPA prior art should be the first checkpoint.

Protective circuit arrangements (H02H, 109 records) and control/measurement classes such as G05F and G01R are comparatively thin next to power-conversion hardware (H02M, 412 records) and grid-supply claims (H02J, 849 records). This gap suggests that fault current limiting, DC breaker coordination, protection relay logic, and multi-terminal control algorithms specific to HVDC links carry lighter claim density than the core converter topology. That does not mean these areas are unclaimed, only that the filing pressure is measurably lower.

WO2019109271A1, filed by ABB Power Grids Switzerland AG and published in 2019, describes a voltage source converter system that upgrades an existing line-commutated converter (LCC) HVDC installation by substituting VSC converter units for the original LCC converter units, while keeping the existing LCC transformers in place. The claims are framed around a retrofit architecture — replacing converter units on an existing transformer bank — rather than a greenfield VSC design. Anyone planning a hybrid LCC-to-VSC upgrade path should review this filing's claim scope closely before finalising a converter-unit substitution design.