In Figure 1, a typical configuration
of a grid-connected PV system is
represented [2]. In a conventional PV
system, the PV cells (arranged in a single
module, a string of series-connected
modules, or an array of parallel-connected
strings) generate a dc current
that greatly depends on the solar irradiance,
temperature, and voltage at
the terminals of the PV system. This dc
power is transformed and interfaced to
the grid via a PV inverter. Additional elements
include a grid connection filter,
a grid monitor or interaction unit (for
synchronization, measurements, antiisland
detection, etc.), and a low-frequency
transformer (which is optional
depending on local regulations, the
converter topology, and the modulation
used to control it [3]). Another option is
an intermediate dc–dc power stage between
the PV modules and the grid-tied
inverter. This optional stage decouples
the PV system operating point from the
PV inverter grid control. Additionally,
it can boost the PV system dc output
voltage if required or provide galvanic
isolation and perform maximum power
point tracking (MPPT) control.