A Method for Detecting PV Module’s Degradation due to Increased Local Resistance in Power Plant

To create a reuse standard, we devised and demonstrated a method to detect the deterioration of PV (Photovoltaic) modules caused by an increase of local resistance from inverter operation data (voltage, current, irradiation). After that, a method for determining the quality ranking of PV modules focused on the local resistance was devised.The PV system equipped with a control unit performs the proposed detection method using one time zone of MPPT (maximum power point tracking) and two time zones of clipping of the output to detect local resistance increases. We obtained the operating data from the 53.8 kW PV power generation system installed 11 years ago. By applying the proposed method, we succeeded in detecting an increase in local resistance for a module that has deteriorated by about 7% compared to its rating. Over the past four years, the degradation rate is equal to or slightly higher than the guaranteed performance of the module of 0.7% / year. In addition, we investigated the PV modules in this system and found many parts of corrosion. This showed that the proposed method is useful.