Abstract
The relative weight of the energy generated by means of renewable
sources is constantly increasing. Among all these sources, the photovoltaic
(PV) systems present the higher and more stable relative growth.
However, the PV system is still too expensive and a significant effort
is being done to increase the efficiency and reduce the cost. Concerning
the PV inverters, this has lead to the elimination of the low frequency
(LF) transformer that has been traditionally included. The LF transformer
provides isolation from the grid but reduces the PV inverter efficiency
and increases its size and cost. However, the elimination of the
transformer might generate strong ground currents, which become now
an important design parameter for the PV inverter. The ground currents
are a function of the system stray elements. However, there is no
simple model and procedure to study the common mode behavior of a
PV system, which is required to analyze the ground currents. In this
paper, a comprehensible model is proposed which provides a better
understanding of the common mode issue in single-phase transformerless
PV systems. In addition, a procedure is developed to analyze the
global performance, efficiency, grid current quality, and common
mode behavior of a PV inverter as a function of its particular structure
and modulation technique
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