A good starting point to model this scenario is to look at the 'Three-Phase Mutual Inductance Z1-Z0' block which shows how to model 3-phase mutual inductance. The following documentation link explains this in detail:
The example link on this page: "power_3phmutseq10" illustrates the use of this block to build a three-phase inductive source with different values for the positive-sequence and zero sequence impedance.