Simplifying Switched Bond Graphs Using Residual Sinks to Enforce Causality: Application to Modeling the Zsource Inverter

Abstract

This paper addresses the problem of modeling the monophasic Z-source inverter in the bond graph (BG) domain. The Z-source inverter is a standard voltage source inverter (VSI) fed through a diode and an LC network. The dynamics introduced to the circuit by the LC network, added to the nonlinear behavior of the VSI and the diode, which results in several switched dynamic modes, makes this configuration very difficult to study and simulate. The main advantage of the Z-source inverter over the standard VSI is that the former can rise or drop the output voltage of the VSI at the same stage and, also, that it avoids the need of using dead time delays between commutations. This latter improvement is enabled by the possibility of shooting-through two power elements in the same leg of the VSI, as the DC-link source is protected by the LC network.
This work revisits the results in (Vázquez Sieber et al. 2008) with the aim of presenting a fully object oriented bond graph model of the Z-source inverter where each BG component represents one and only one physical phenomenon, with a minimum numbers of switched elements, and whit integral-only causality assigned to the energy storage elements. To handle the switching in the BG domain the switched power junction (SPJ) formalism is selected and the residual sink concept is used to avoid the derivative causality. Some simulation results are shown to prove the correct performance of the model.