Hi gm33,

First congratulations for getting the interview. I think it makes perfect sense to concentrate on the projects that are related to the PhD. You need to be able to show how the PhD will build on your previous research experience and with 15-20 minutes it is better to go for depth than breath. Remember you are also being assessed on time management so practice your presentation over at home and make sure you can do it within the allocated time.

Best wishes!