How can I model the ABC flux in a shunt element?

Dynamic Simulation

You can model the ABC flux by performing an Inverse Clarke transform on the dq0 flux signals as shown in the attached project.

Double click on the Flux ABC Virtual Instrument, click Edit, double click on Flux A, Flux B or Flux C to see how the transform is implemented in PowerFactory. 

You can also enable the parameter event to see a step change in flux.