Online Characterization of PV Strings by Smart Inverters Using a Self Referencing Algorithm

We present a remote diagnostic method that uses the IV measurement function of smart inverters and a so called self-referencing procedure to represent the performance of the PV generator vs. operating conditions irradiance and temperature (G and T). We have recorded 200 IV-curves of a PV string within a period of six months using a smart inverter. A deep autoencoder detected disturbed or IV measurements so that these were not included in the evaluation. The effective irradiance Geff at the PV string was determined, which was included in the evaluation instead of the measured irradiance. In addition, the cell temperature of the PV generator Teff was determined using physical models for the evaluation. As a result, we create smooth power-surfaces over Geff and Teff conditions in the range of 100–1100 W/m² and 15–90 °C. For validation, the performance data of the PV string were compared by indoor measurements with a calibrated flasher at standard test conditions. The approach offers a remote and real-time diagnostic by smart inverters. It is well suited for accurate power monitoring of PV generators or degradation or soiling tracking without the need for additional sensor capabilities.