# Review on Optimization Techniques of PV/Inverter Ratio for Grid-Tie PV Systems
## 2 Literature Review
### PV Array to Inverter Sizing Strategies
#### 2.2.2 DC/AC Sizing Ratio According to Third-Party Publications
Consequently, throughout the maximum irradiance, where the inverter that clips power could allow the inverter components to overheat, an undersized inverter would directly affect energy generation. Alternatively, higher power inverters will operate at reduced efficiencies, particularly in medium and low irradiance steps, which results in increasing inverter costs and limits the system's potential to make money. The grid-connected system performance is significantly impacted by the choice of the inverter, which may be either oversized or underpowered in relation to the STC power capacity of the PV array, as stated in ([PERSON] et al., 2016). According to ([PERSON] et al., 2016), the ideal PV/inverter size ratio is significantly influenced by factors such as inverter efficiency, orientation and inclination, local climate, and location. In addition, the authors recommended that the capital expenses of the PV-to-inverter cost ratio (T) be taken into account when forming the top sizing ratio value. For the highest inverter efficiency, the ratio of inverter sizing (Rs) must be scaled within 1.3-1.4 (low irradiation) and 1.1-1.2 (high irradiation) in specific European locations, such as Nancy, Stuttgart, London, Almeria, and Madrid. The Rs value must be estimated in the range of 1.4-1.5 on low irradiance and 1.2-1.3 on high irradiance when dealing with low inverter efficiency ([PERSON] et al., 2016). The Rs is determined in terms of the inverter sizing ratio (P\({}_{\text{inv, rated}}\)) (dimensionless) and the array capacity at STC rating (P\({}_{\text{PV, rated}}\)) by Equation (4) ([PERSON] et al., 2016);  
\[\text{Rs}\ =\frac{\text{P}_{\text{PV,rated}}}{\text{P}_{\text{inv,rated}}} \tag{5}\]  
In order to determine the ideal inverter downsizing coefficient, the study ([PERSON] et al., 2016) suggested a sizing method in the range of P\({}_{\text{inv,dc,nom}}\), and P\({}_{\text{PV,nom}}\). The authors point out that a number of variables, including weather, price, and inverter features, may impact an inverter scaling strategy. The threshold (occurrence percentage) of irradiance (GTH) at a specific site should not be exceeded by the distribution of irradiance, as this may result in excessive power that exceeds the inverter capacity. This could result in some energy losses under greater irradiance and a reduced coefficient of power with temperature. The relationship between P\({}_{\text{inv,dc,nom}}\), and P\({}_{\text{PV,nom}}\) is called the inverter downsize coefficient (R) and is derived by ([PERSON] et al., 2016):  
\[\text{R}=\frac{\text{P}_{\text{inv, dc,nom}}}{\text{P}_{\text{PV, nom}}}=\frac{\text{G}_{\text{TH}}}{\text{G}_{\text{STC}}}; \begin{cases}\text{ Undersized inverter for $0<\text{R}<1$}\\ \text{ oversized for $\text{R}>1$}\end{cases}  \tag{6}\]  
where G\({}_{\text{STC}}\) = 1000 W/m\({}^{2}\) is the STC irradiance, G\({}_{\text{TH}}\) is the irradiance threshold at a chosen site (W/m\({}^{2}\)), P\({}_{\text{PV,nom}}\) is the rated PV installed power (kWp), and P\({}_{\text{inv,dc,nom}}\) is the DC input rated power of inverter (kW). [PERSON] et al. (2016) stated that the present performance of the PV-to-inverter sizing ratio, which is given by (P\({}_{\text{-PV}}\)@STC/PWR\({}_{\text{-AC}}\)@NOM) varies between 0.95 to 0.85 in most PV designs operating within a PV plant site in Germany, Bavaria Southeast.