In the literature, only a few works have attempted to derive the equivalent model of unbalanced three-phase passive elements in the sequence domain, and none is able to account for the interaction between the zero sequence and the positive and negative sequences. This work presents the derivation of the equivalent dq sequence-domain model of unbalanced three-phase passive elements both analytically and with an intuitive graphical approach. The proposed model can be a useful tool to design controllers for three-phase inverters and rectifiers. Experimental results are shown to validate the proposed models.