Hello,
Please see the demo model included with PLECS "Buck Converter with Parameter Sweep" where an inductance value is swept. With a 3 phase voltage source you can parameterize the magnitude, frequency, and offset values by assigning variables that you then change the values for via a script, for example. In PLECS Blockset, you can run a MATLAB script, and in PLECS Standalone you can either use an internal Simulation Script (video:
https://www.plexim.com/support/videos/simulation-scripting-standalone), or externally via the XML-RPC protocol, such as to use Python as your scripting environment, for example.
Good luck,
Kris