Novel grid-connected non-isolated converters for photovoltaic systems with grounded generator
In the photovoltaic branch, transformerless inverters are nowadays the majority of the systems installed in Europe, mainly because of the higher level of efficiency and reduced cost and weight when compared with their counterparts with transformer, whether this concerns low- frequency or high-frequency models. Nevertheless, some limitations arise for the operation of such systems, mainly regarding the fact that normally the panel output cannot be grounded, what is, for example not allowed in USA. Non- grounded operation of panels composed of some new cells technologies can bring undesired effects like cell aging and efficiency reduction. In addition, security matters regarding leakage current due to the panel parasitic capacitance are also a common problem in such systems. In order to address such matters, this paper proposes a novel DC-DC converter for the application in transformerless photovoltaic systems. As main characteristic, it allows the grounding of the negative output of the photovoltaic array and provides a bipolar output voltage. Following the proposition of the circuit, the analysis and evaluation will be performed. A prototype was built and the experimental results are presented in the end.