Three-phase tri-state buck–boost integrated inverter for solar applications

This study presents a three-phase tri-state buck-boost integrated inverter suitable for stand-alone and/or grid-connected photovoltaic (PV) energy applications. The usage of the special features of the tri-state operation coupled with a modified space vector modulation allows the inverter to present a remarkable degree of freedom for the controllers´ design, that is, input and output can be independently controlled. As the input can be autonomously controlled, this converter is very attractive for interfacing renewable energy sources as PV panels, once the main duty cycle D₁ controls the maximum power point tracking and the second duty cycle D₂ is responsible to feed the output. It should be pointed out that there are no power electrolytic capacitors in this integrated inverter, which results in a major advantage for the structure working life and it is the first time in the literature that this inverter is used to feed power into the grid. Throughout this study the system is described, the modulation and control schemes are presented and interesting experimental results are available in order to confirm the outstanding features of this proposal.