On the calculation of the STC power of PV generators by using typical monitoring system data

The properly in-field characterization of the power at Standard Test Conditions, PSTC, of PV generators is becoming increasingly important in order to evaluate their performance and its evolution in time. Within the state of art, the PSTC characterization procedures of PV arrays are mainly based on I-V curve measurements or PDC measurements performed by precision wattmeters. Those characterizations are usually carried out during discrete measurement campaigns, which does not allow a continuous tracking of the PSTC evolution. In this paper a new PSTC characterization procedure is proposed which is based on the DC power measurements performed by the own PV inverters connected to the PV arrays. This procedure enables an automatic and continuous calculation of the PSTC, which allows to observe its evolution and to detect possible anomalous trends, premature degradations, etc. The procedure has been validated in several PV generators of the large-scale Amareleja PV Plant (45.6 MWp). As showed in this paper, by using several day data and applying the adequate filters, a high accuracy in the PSTC calculation can be achieved, a similar accuracy to that obtained by using precision wattmeter measurements.