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Low power grid-tied photovoltaic (PV) generation systems increasingly use transformerless inverters. The elimination of the transformer allows smaller, lighter and cheaper systems, and improves the total efficiency. However, a leakage current may appear, flowing from the grid to the PV panels through the existing parasitic capacitance between them, since there is no galvanic isolation. As a result, electromagnetic interferences and security issues arise. This paper presents a novel transformerless single-phase Current Source Inverter (CSI) topology with a reduced inductor, compared to conventional CSIs. This topology directly connects the neutral line of the grid to the negative terminal of the PV system, referred as common mode configuration, eliminating this way, theoretically, the possibility of any leakage current through this terminal. The switches control is based on a hysteresis current controller together with a combinational logic circuitry and it is implemented in a digital platform based on National Instruments Technology. Results that validate the proposal, based on both simulations and tests of a low voltage low power prototype, are presented.

Photovoltaic (PV) electricity is widely used because of its positive environmental impact. To properly feed this energy into the grid, an electronic power converter, known as a PV inverter, is needed, which may or may not use a transformer. This article details the analysis and design of a transformerless photovoltaic inverter topology for grid-connected applications. This converter offers high efficiency, a low number of elements, and negligible leakage current, which makes it a good alternative for this application. The converter has been validated through an experimental prototype and compared with other topologies with similar characteristics.

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