No, NPTEL courses are not compulsory for B.Tech. In AKTU. These courses simply aim at adding qualitative knowledge among the students. In addition, every NPTEL course grants you extra 3 credits. If you are lagging behind in B.Tech. courses then NPTEL courses will definitely help you compensate for the loss.
So it can be said that for. B.Tech. student NPTEL courses are highly recommended but not compulsory.