Initial detection of potential-induced degradation using dark I–V characteristics of crystalline silicon photovoltaic modules in the outdoors

We have studied a method to diagnose the initial potential-induced degradation (PID) of p-type crystalline silicon photovoltaic (PV) modules using the dark I–V (DIV) characteristics of the PV power system. The DIV characteristic behavior is expressed as the reverse saturation current density ratio calculated by the double diode model and the current ratio by comparing DIV and light I–V (LIV) before and after the occurrence of PID of solar cells. The ratio of the normalized maximum power of the PV modules that suffered the initial PID in the outdoors was verified to be 0.0125 RMSE (root mean square error). The proposed method can detect the occurrence of PID by periodically measuring both end PV modules of the same PV string, without interruption of the power plant in the dark state, and it is possible to easily and quickly diagnose the power loss due to the initial PID.