Abdollah... instead of doing multi machine power system in MATLAB go with PSAT tool which also matlab supported software..here u can easily design it..this is free software u can download it from internet..
Abdollah you can use PSAT for the dynamic stability studies, and it is very efficient.
Power System Analysis Toolbox (PSAT) is a Matlab toolbox for electric power system analysis and simulation. All operations can be assessed by means of graphical user interfaces (GUIs) and a Simulink-based library provides an user-friendly tool for network design.
also PSAT offre library of Models (genrator ,excitaion system,governor,wind turbine ,FACT ............) also PSAT has library of IEEE test system such as 9bus and 14bus.
if you want work with PSAT i can give you PSAT-2.1.8 with his tutorial.