Limits of Advisability for Master--Slave Configuration of DC--AC Converters in Photovoltaic Systems

Several feed-in tariffs are now available for photovoltaic (PV) systems, and thus, the maximization of the productivity is very important; this goal can be achieved by solar cell technologies with high efficiency and low temperature losses, one axis or dual axis sun-tracking systems, proper cooling techniques for PV modules in building integrated applications, master--slave (M--S) control for the inverters in large grid-connected PV plants, etc. About the last item, this paper deals with the advisability of the master--slave concept versus the centralized inverter layout. Here, attention is focused on the influence of the installation site with its irradiation peculiarities, the tilt angle of the PV modules, the efficiency curve of the inverters, and the number of slaves. The simulated productions put into evidence energy gains up to 4% per year, considering the only cloudy-day contribution. On the basis of these comparisons, the M--S concept can be profitable if the number of cloudy days is sufficiently high, the tilt angle is adequate, and the dc--ac efficiency curve is ``well shaped."