As of my last knowledge update in September 2021, I'm not aware of a concept called "virtual winding" in the context of transformers. Transformers are devices that transfer electrical energy between two or more circuits through electromagnetic induction. They consist of primary and secondary windings wound around a common magnetic core.
If "virtual winding" is a term that has emerged after my last update, I wouldn't be able to provide specific information about it. It's possible that this term might refer to a new development, concept, or terminology in the field of electrical engineering or transformers that has emerged since then.
I recommend consulting more recent and specialized sources, such as academic articles, engineering journals, or textbooks, to get accurate and up-to-date information about the concept of "virtual winding" in transformers.