《Highly Efficient Single-Phase Transformerless》.pdf

3118 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 57, NO. 9, SEPTEMBER 2010 Highly Efficient Single-Phase Transformerless Inverters for Grid-Connected Photovoltaic Systems Samuel Vasconcelos Araújo, Student Member, IEEE, Peter Zacharias, Member, IEEE , and Regine Mallwitz, Member, IEEE Abstract—Driven by worldwide demand for renewable sources, the photovoltaic market saw in the last years a considerable amount of innovations regarding the construction and operation of inverters connected to the grid. One significant advance, among some that will be here discussed is, for example, the abolition of the galvanic isolation in inverters installed in Germany. There, transformerless topologies, like the H5 and Heric, can reach very high levels of efficiency and allow the best cost–benefit ratio for low-power grid-tied systems. This paper will follow this direction and propose a single-phase transformerless inverter circuit being composed of the association of two step-down converters. Each one modulates a half-wave of the output current, as the correct polarity of the connection to the grid is provided by low-frequency switches. Due to its straightforward design, reduced amount of semiconductors, and simple operation, it is possible to achieve Fig. 1. Overview of the grid-connected PV system concepts showing from the a high level of efficiency and reliability. These and some other left to the right: module integrated, string, minicentral, multistring, and central characteristics will be benchmarked against other existing circuits, inverter concepts. being followed by a theoretical analysis on the properties of the proposed solution. The project of a laboratory prototype will be evaluate