## 3 Results
### Use of the Developed Application in the Analysis of Some Parameters of Two PV Plants
Figure 15: Graphical representation of the matrix of the correlation indexes of the power production at the output of the 17 inverters (\(P_{\rm{ac}}\)) of plant 2 for 3 March 2021 (**a**), 15 February 2021 (**b**) and 26 January 2021 (**c**). Therefore, the representation of the correlation index matrices allows visual access to a comparison of the operation of all the inverters in a plant, and it can be a very useful tool, especially in plants with a larger number of inverters, detecting possible deviations in production and showing the greater or lesser magnitude of these possible deviations. Thus, just by visualising a series of numbers, it is possible to see whether the inverters are working correctly or whether there is some kind of problem. It would only be necessary to proceed to analyse in more detail the daily power values if these graphs show the presence of some kind of deviation in order to have more information about when the problem occurred. In addition to the behaviour of the PV plant elements, another very important aspect to take into account during operation is whether their production is having any kind of impact on the electricity grid. In most plants, this is an aspect that is not recorded or analysed, but it is essential in order to be able to correctly integrate the production of this type of plant into the electricity grid without producing disturbances that could affect users [96]. Although a complete analysis of their impact on the electricity network would require grid analysers at the injection point of the plants (PCC), the inverters themselves can provide information on some parameters of the grid and their relationship with the production of the plants. For example, the inverters record the value of the voltage signal of the electricity grid (\(V_{ac}\)), so it is possible, with the values measured by inverters, and without the need for additional instrumentation, to carry out an analysis of the value of this parameter in the different phases. This parameter can be recorded by the inverters 24 h a day, even when no production is being injected into the grid, as is the case with the inverters analysed in this study. As an example, the graphs in Figure 17 show the value of this voltage \(V_{ac}\) in phase 1 measured every 5 min by two inverters, one from plant 1 (a) and the other from plant 2 (b), during the entire period analysed (1 November 2020 to 4 July 2022). The values between 225 and 250 V have been represented in order to better observe the behaviour of this parameter with the colour degradation. In both cases, the highest voltage values generally occur in the central hours of the day, and to a greater extent in the spring and summer months, which is when the production of the PV plants is higher in their geographical location. This behaviour is even more evident in the case of plant 2, which has a higher nominal power and therefore a higher total production injected into the grid than plant 1. Figure 16: \(P_{ac}\) corresponding to inverters of plant 2 on 3 March 2021 ((a) for inverters 1 to 8, and (b) for inverters 9 to 17), 15 February 2021 ((c) for inverters 1 to 8, and (d) for inverters 9 to 17) and 26 January 2021 ((e) for inverters 1 to 8, and (f) for inverters 9 to 17). For a more complete analysis, in addition to the instantaneous values of the \(V_{ac}\) voltage, it has been possible, using the tool developed, to easily determine statistical values of this magnitude, and in general of all the parameters recorded in the PV plants. The maximum, minimum and average values of the voltage measured from the grid have therefore been determined for each day. The obtained results are shown in Figure 18. The two graphs in this figure show the average daily values of the \(V_{ac}\) grid voltage measured in phase 1 by an inverter of PV plant 1 (a) and by an inverter of PV plant 2 (b). Also shown here in blue is the range of values corresponding to the difference between the maximum and minimum daily values of the recorded grid voltage.