Performance Requirements of PV Converters
Efficiency The losses of the PV inverters have reduced in time, and efficiency achieves values above 97% (see, for instance, SunnyBoy 5000TL by SMA for domestic applications below 5.25 kW) and even more for central inverters (see, for instance, SunnyCentral 760CP XT by SMA, a central inverter with nominal power up to 850 kW with 98% of efficiency) [5]. Therefore, it can be affirmed that the PV inverter efficiency for state-of-the-art brand products stands around 98%. However, it has to be noticed that the efficiency is expected to achieve higher values when silicon carbide (SiC) and gallium nitride (GaN) devices are vastly used as the basic power semiconductors of the PV inverters in the next decade [6].
Power Density
Power density is always important, but it is becoming critical mainly for domestic and commercial applications (below 20 kW). In this way, several solutions have been recently presented such as the ABB PVS300 inverter, which is based on a neutralpoint-clamped (NPC) topology, achieving a very compact solution with very high power density [7].
Installation cost
Figure 2 shows the evolution of each cost component of a PV system in central Europe [8]. Comparing the figures from the year 2000 to the figures in 2012, there is an important reduction in the total cost (68%), but the most important reduction (78%) is due to the cost of the PV modules. The inverter cost has been reduced by 68%, and the installation-related costs have had the smallest reduction in the entire group (56%). Installation costs may vary greatly from one country or region to another as the land, labor, and other local factors may have a great influence on the total cost.