Design and implementation of three-phase gridconnected two-stage module integrated converter

This paper presents a high efficiency module integrated inverter (MIC) with both stages ZVS operation for three phase grid tied photovoltaic system. LLC resonant dc-dc converter is employed in the first stage to track the maximum power of PV panel. A novel and simple soft switching scheme without adding auxiliary components is proposed for three phase for the second stage. Meanwhile, modeling and control strategy of three phase four-wire DC/AC converter are also discussed. In addition, a dedicated Center Points Iteration (CPI) MPPT algorithm for LLC resonant topology is applied to quickly tracking the maximum power. In addition, the capacitance of DC-link is also investigated because DC-link capacitor plays an important role for dual-stage MIC. Finally, a 400 watts prototype has been built and tested. The peak efficiency of the whole system prototype has been measured, which is up to 96%, 98.2% in the first stage, and 98.3% in the second stage, respectively.