Hi,
“MP_Core” toolbox is not a standard toolbox that comes with MATLAB.
- You can find the instructions to download & install "mp_core" here: GitHub - MATPOWER/matpower: MATPOWER – steady state power flow simulation and optimization for MATLAB and Octave
- You can also have a look at the official website here: MATPOWER – Free, open-source tools for electric power system simulation and optimization
Hope it helps!