Q:   Can I use the system equivalence tools or Thevenin equivalents if IBR models are present in my OneLiner network?

A:   The linear theorems that underlie network equivalencing do not strictly apply to networks that contain IBR models because the IBR fault response models are nonlinear.  If you choose to use network equivalencing when IBR models are present, it is recommended to do extensive testing for various fault types and compare the original full model results against the results of the smaller equivalent model.  Some judgment will be required to determine whether the equivalent model provides an acceptable representation of the full system model from which it was derived.