I have a Raspberry Pi 3, and because it has built in WiFi, is there any way to create virtual adapters so it can be connected to a WiFi network and be broadcasting one?
You may check this link that can create a virtual AP with
Raspberry Pi 3. If the virtual AP work but not the Pi, then you may need to create static IP routes to enable the Pi to connect to the network.
Hope this help.
Some years later with modern operating system using systemd-networkd there is a setup available that is tested with Raspberry Pi. It uses only the built-in WiFi device and creates a virtual interface ap0 that is used for the access point. The physical interface wlan0 is used for the uplink client connection to the (internet) router so it works as WiFi repeater. How to setup this you can look at Access point as WiFi router/repeater, optional with bridge.