Recently, many non-conventional three-phase inverters, topologies for green energy source grid-connection systems, and electric drives have been proposed. Simplifying the inverter circuit is crucial to analyze and solve their models in order to design them. The main goal of the study is centered on obtaining a single-phase equivalent circuit and space state model from non-conventional three-phase inverters based on bidirectional direct current–direct current (DC–DC) Buck-Boost topology using isolated gate bipolar transistors (IGBT). From just one phase of the three-phase inverter, the single-phase equivalent circuit was obtained by means of Kirchhoff’s laws. The equivalent circuit operation steps were presented in order to obtain the space state model. Finally, the equivalent circuit was simulated, and experimental results with a 200 W three-phase inverter feeding a resistive, inductive, and capacitive loads were performed to confirm the theoretical and simulation analyses. The results show the state space dynamic behavior variables of single-phase and three-phase models are quite similar. Therefore, it can be concluded that the proposed circuit can be used with property to represent equivalent single-phase models of non-conventional three-phase inverters.