As of my last update in September 2021, there is no established concept of a "virtual winding transformer" in the context of autotransformers. Autotransformers are transformers with a single winding that acts as both the primary and secondary winding. They are used to step up or step down voltages in electrical power systems.
It's possible that new concepts or terminologies have emerged after my last update, or there might be some misunderstanding or miscommunication regarding the term "virtual winding transformer." If this is a recent development or a specialized term used in a specific context, I recommend consulting up-to-date technical sources, research papers, or relevant experts in the field to get accurate information on the concept.