The choice of inverter for the photovoltaic installation is a very important step in the design of PV systems. A poorly chosen inverter, even with good quality photovoltaic modules, can significantly reduce the efficiency of the entire installation. The key parameter in the selection of the inverter is its power on the DC side. According to the generally accepted principle, the power of the photovoltaic installation should be between 85 and 118 \( \% \) of the inverter power. This is because the actual operating conditions of photovoltaic modules are different from the laboratory conditions under which they are tested (STC conditions: 1 000 \( \frac{W}{m^{2}} \), \( 25_{}^{o}\textrm{C} \), AM1.5). A photovoltaic system rarely operates at its nominal power.
The selection of an inverter for a photovoltaic installation can be done in terms of the number of MPPT (maximum power point controllers). In the case where the photovoltaic installation is built with an inverter with one MPPT, then the MPPT maximum power point will be sought for all modules simultaneously. This is also the case when the modules form several chains and are connected separately to the inverter. Therefore, it is important that each PV module has similar operating conditions and parameters. On the other hand, a photovoltaic installation built with several chains with different numbers of panels or uneven lighting requires an inverter with a higher number of MPPTs. In this case, each chain of PV modules connected to a given MPPT will be received by the inverter as one separate energy generator [1].
Inverter matching is also carried out based on the technology in which the modules used in the photovoltaic system were manufactured. In the case of monocrystalline, polycrystalline, thin-film CIS/CIGS panels, as well as micromorphic modules in which a layer of transparent conductive oxides (TCO) is separated from the glass by a laminate, it is possible to use both transformerless and transformer inverters. Galvanically isolated transformer inverters are used for installations made of panels in which the TCO layer is not isolated from the glass. This applies to CdTe thin-film and amorphous modules, which require the negative pole to be grounded [2]. The lack of grounding can cause current to flow into the module frame, which in turn can cause sodium ions to precipitate from the glass and tarnish it. By using a transformer inverter, galvanic separation is provided between the DC and AC sides of the PV system. If a short circuit occurs on the DC side, the short circuit current does not flow through the inverter, which protects it from damage.