Hello, please see subsection "Starting an Analysis" in the Simulation Scripts in PLECS Standalone section of Chapter 10 - Simulation Scripts of the PLECS User Manual (Page 251 in the latest PLECS 4.5 version release).
The command is:
plecs('analyze', 'analysisName', optStruct)
This starts the analysis defined in the Analysis Tools dialog under the name analysisName. The optional argument optStruct can be used to override model parameters.
Let me know if you have any questions.