The most-cited records in this corpus are modular multilevel converter and hybrid HVDC converter patents, including US20130279211A1, US20130208514A1 and US20130208521A1, alongside the related WO2011124258A1 hybrid HVDC converter filing. These citation leaders date from the early-to-mid 2010s, before the 2017 peak in this dataset, and citation counts favour older records simply because they have had more time to be cited. Current recent-year momentum across the tracked major assignees — including ABB, Siemens, GE and Alstom's technology entities — shows zero filings in the latest year, so 'most important' historically and 'most active' currently are two different questions here.

No — filing peaked at 62 records in 2017 and had fallen to 22 by the 2022 midpoint of this dataset, a flat-to-declining trajectory rather than a growing one. Because publication lags filing by roughly eighteen months, the very latest years in any such trend will always look lower than they eventually turn out to be, but the multi-year decline from the 2017 peak predates that lag effect. Treat this as a technology where the core converter and protection claim space is largely staked out rather than one still in a land grab.

Start with the H02H protective-circuit subclass, which holds 195 of the 763 families in this corpus, considerably fewer than the 611 in H02J grid systems or 329 in H02M power conversion. That smaller pool still contains highly cited hybrid-converter patents, so a narrower but more careful search on fault ride-through and DC circuit breaker claims is likely to surface the real blocking art faster than a broad converter-topology sweep. Given China's 200-record lead in receiving-office volume, that search needs to cover Chinese-language filings from entities like State Grid and the Nari Group, not just English-language US and European records.

China leads with 200 records at its receiving office, ahead of the European Patent Office at 153 and the United States at 130. WIPO/PCT filings add another 93, with India at 46 and the United Kingdom at 29. This ordering reflects where applicants are choosing to seek protection, not necessarily where the underlying R&D happens, but it does mean Chinese-language prior art and state-linked entities such as State Grid deserve first-line attention in any competitive or FTO analysis.

US9735702B2, held by Huazhong University of Science and Technology, claims an operating method for boosting AC-side voltage in a full-bridge sub-module modular multilevel converter while keeping DC-link voltage and semiconductor current rating constant. It ties that method specifically to reducing energy interaction between upper and lower arms and to a resulting reduction in required sub-module capacitance. Anyone implementing full-bridge sub-module MMC topology with AC-side voltage boosting under a fixed DC-link voltage needs to review this claim scope directly rather than assume a workaround exists, since it was granted at the 2017 peak filing year when this exact topology space was most active.