It's well known that oversizing the inverter may increase power output in lower light conditions, through having more DC power than the inverter AC power and take the full advantage of the inverter capacity.
The level of oversizing depends on many factors, like the location the orientation of the PV plant. In middle European countries like Germany the sunlight is very poor during winter and the summertime is relatively short, which make oversizing the inverter a reasonable procedure.
In this case study, Huawei 60 KTL grid-connected inverter was implemented with the following project details:
Location: south Germany where the sun’s maximum irradiation power remains at around 1,000 W/m².
Orientation: the PV modules were installed on a complex rooftop with different orientations; south, north, and east/west.
Connection: 3 MPPT are connected to the southern roof, 1 MPPT to the north and 2 MPPT to the east/west. All strings have the same number of PV modules.
DC power: 140 % DC-to-AC ratio (sizing factor: 1.4). The PV Generator produces 80 kwp in the standard test conditions.
Analysis:
output power:
The inverter works normally with smooth AC curve with no clipping during normal weather days. During the heat days the output curve of the MPPT connected to the southern roof clips.
Clipping losses are considered a problem for operating PV power plants, but since the number of days with perfect sun radiation are very few in this region and the MPPT connected to the north and east/west side do not show any clipping during heat days, clipping is not considered a major issue on the inverter lifetime.
Advantage of using the 60 KTL inverter:
The Huawei 60 KTL has 6 MPPT and 12 inputs, this feature makes it possible to connect such complex roof structure with only one inverter and minimize the costs.
