In-Situ Characterization of Potential-Induced Degradation in Crystalline Silicon Photovoltaic Modules Through Dark I-V Measurements

Abstract

© 2011-2012 IEEE. A temperature correction methodology for in-situ dark I-V (DIV) characterization of conventional p-Type crystalline silicon photovoltaic (PV) modules undergoing potential-induced degradation (PID) is proposed. We observe that the DIV-derived module power temperature coefficient (γdark ) varies as a function of the extent of PID. To investigate the relationship between γdark and DIV-derived module power (Pdark (Ts), measured in situ and at the stress temperature) two parameters are defined: change in the DIV-derived module temperature coefficient (δγdark ) and DIV-derived module power degradation at the PID stress temperature (δPdark (Ts)). It is determined that there is a linear relationship betweenδγdark andδPdark (Ts). Based on this finding, we can easily determine the module γdark at various stages of PID by monitoring Pdark (Ts) in situ. We then further develop a mathematical model to translate Pdark (Ts) to that at 25 °C (Pdark (25 °C)), which is correlated with the module power measured at the standard testing conditions (PSTC ). Our experiments demonstrate that, for various degrees of PID, the temperature correction methodology offers a relative accuracy of ±3% for predicting PSTC . Furthermore, it reduces the root-mean-square error (RMSE) by around 70%, compared with the PSTC estimation without the temperature correction.