hmm, I don't see anything in that article that would say diesel submarines are using AC generators or anything here would disprove the idea that diesel submarines largely use DC electrical power, but I'm sure you know best. I will just leave it as that.I don't quite understand your contact's point on diesel submarines and DC power. Almost all modern generators are alternators, fitted with AC-DC converters if needed. In particular all PLAN vessals use high-speed alternators.
The article is about Xiao Fei and his work. Xiao Fei worked on high speed induction generators for PLAN in the early 2010s and worked as part of Ma Weiming's team on subsequent new generator designs which are installed on all PLAN vessels in active service or under development. Xiao Fei is an expert on power conversion and has been in charge of converter design for those generators.
In around 2008, at the suggestion of Ma Weiming, Xiao Fei had applied his work on high speed marine generators to solve Chinese wind turbine industry's struggle with converters, and successfully designed a converter for a 2MW direct drive wind turbine PMSG.
Anyway it's clear from the article that all PLAN vessals use high speed alternators and then convert AC to DC if needed. This is not surprising at all since almost nobody uses DC generators nowadays.
Also it's interesting that the article claims Ma Weiming's high speed generators are now standard on all PLAN vessels in active service. PLAN must have done a lot of retrofitting.