Windows tablet otg simultaneously charge?
If you have a hub connected to the tablet, the tablet is in host mode, and must be a SOURCE for VBUS. Therefore it can't charge itself. To accomplish what you want you need a special device called "accessory charge adapter". In simplest form it might look like this:
In theory your tablet should discriminate between ID pin grounded (host mode, sources VBUS), ID pin floated (device mode, consumes VBUS), and ID pin = 100-125k, meaning "accessory charger". In this case the tablet should serve as a host, but consume VBUS for internal charging.