Development of models for on-line diagnostic and energy assessment analysis of PV power plants: the study case of 1 MW Sicilian PV plant

For photovoltaic (PV) power plants, every kilowatt-hour is important, because only kilowatt-hours that are fed into the grid are remunerated. A plant’s operator can only adopt prompt measures to eliminate operational faults when these are immediately signaled. In fact, just reading the feed-in meter each month is not sufficient to promptly recognize faults and to avoid the loss of yields. Many inverters record the most important operational data, automatically evaluate the data and, in case ofa fault, send the operator notifications via email ortext message. However, it only allows obviousfaults to be recorded. On the other hand, continuous, absolute and comparative measurements are necessary to ensure the maximum efficiency and availability. Based on real time and historical data, a technical plant manager should inform the operators of any fault which occurs or even take independent measures to rectify it. In this context, suitable models are developed and applied to a 1 MW power plant where a SCADA, Supervisory Control And Data Acquisition,has been installed and operational data are available on a Web page. In order to evaluate the performance of the PV system, firstly the daily corrected Performance ratio has been evaluated. Then, different approaches to estimate the AC and the DC power of the PV plant have been developed. Basing on the difference between the measured and the estimated power,a statistical approach is proposed; it allows to define suitable thresholds on the AC and DC power in order to individuate a fault when occurs. The experimental results show theeffectiveness of the proposed approach.