Dynamic characteristics of three-phase Z-source-based photovoltaic inverter with asymmetric impedance network

Abstract

Three-phase Z-source inverter (ZSI) is a relatively new buck-boost-type inverter topology, which in photovoltaic (PV) applications offers more efficient power point tracking than traditional VSI-type inverter in a single power processing stage. This paper presents an accurate small-signal model for the impedance network present in three-phase grid-connected ZSI, which can be used to e.g. design its control system and predict its impedance characteristics. In this paper, the developed small-signal model is used to study the effect of the asymmetric impedance network to the behavior of the network. It is shown, that asymmetric impedance network will affect to the dynamic characteristics of the inverter, but does not significantly decrease its electrical performance or compromise its stability.