Unipolar PWM Strategy for Transformerless PV Grid-Connected Converters

In domestic grid-connected PV applications, a singlephase
converter is usually employed. In such low-power plants, it
is possible to adopt converter topologies without galvanic isolation
between the photovoltaic (PV) panels and the grid. The absence of
a high- or line-frequency transformer permits us to reduce power
losses, cost, and size of the converter. On the other side, in the
presence of a galvanic connection, a large ground leakage current
could arise due to parasitic PV panel capacitance. Leakage currents
cause electric safety problems, electromagnetic interference
increase and, consequently, a reduction of the converter power
quality. This paper presents a converter topology able to minimize
the ground leakage current also in the case of unipolar pulsewidth
modulation without increasing inductive common mode filter size
and preserving efficiency. Simulations and experimental results
show the feasibility of the proposed solution.