Environmental Engineering Reference
In-Depth Information
Figure 4.59
Photovoltaic System with Parallel Strings and Central Inverter
For partly shaded systems or modules with different power outputs, this
connection scheme can cause relatively high losses. Therefore, string inverters
with decoupled parallel strings can reduce the losses. Their nominal power is
in the range of 1 kW. However, module inverters promise the best performance
for partially shaded photovoltaic generators. They can set a different operating
voltage for each module. The cabling is simpler because no DC cables are
needed. Another advantage is the system modularity. However, the
disadvantages of module inverters are lower nominal efficiencies and higher
specific costs. Figure 4.60 shows both versions: string and module inverters.
Finally, Table 4.12 shows
technical data
for several inverters. It is apparent
that the efficiency increases slightly with the rated power. The harmonic
distortion of available inverters is between 1.5 and 5 per cent. Most of the
inverters are designed using the PWM concept.
Figure 4.60
Photovoltaic Generator with String Inverters (left) and
Module Inverters (right)
