Single-stage DC-AC converter for photovoltaic systems

This paper presents a DC-AC converter that merges a DC-DC converter and an inverter in a single-stage topology to be used as an interface converter between photovoltaic systems and the electrical AC grid. This topology is based on a full bridge converter with three levels output voltage, where two diodes and one inductor have been added in order to create a Boost converter. The control system of the proposed converter is based on two hysteretic controllers: one for the grid injected current and the other for controlling the panel current. A prototype of the proposed converter including power and control circuits was developed. The MPPT algorithm is not yet implemented and, therefore, to obtain experimental results an additional power supply is used to emulate the PV panel. Theoretical analysis and design criteria are presented together with simulated results to validate the proposed concepts. Experimental results are obtained in a lab prototype to evidence the feasibility and performance of the converter.