Q: What should I do if suitable Professor for my thesis research is completely booked? I plan to make Master Thesis with the topic around Energy Storage System and PV, unfortunately the suitable Professor in electric power system does not have time to be my advisor.

I will use Matlab as modelling tools. Should I go find the professor with expertise in Matlab and Math Modelling instead?

Or should I change my topic instead?
You might try to convince the Professor's best student to supervise you. (Formally, the Professor might need to be listed as your supervisor, but the student will be your supervisor informally.)