Characteristics of Failed Bypass Diodes for Photovoltaic Module by Artificial and Natural Lightning

In recent years, bypass diodes (BPDs) in photovoltaic (PV) modules have failed because of lightning-induced surges, and burnout of BPDs has also occurred. In this study, we investigate the characteristics of BPDs in PV modules, with the most likely cause of failure being lightning-induced surges; conduct an artificial lightning test of BPDs; and compare the failure characteristics with those BPDs that failed due to natural lightning. As a result, we confirmed that the schottky barrier diodes (SBDs) exposed to lightning-induced surges show short-mode failures where the fault resistance decreases inversely proportionally to the increase in the lightning surge amplitude. We also confirmed that the BPD in the PV module damaged by natural lightning fails in short mode or open mode. When the BPD fails in short mode, the circulating current generated in the bypass circuit increases the risk of heat generation and ignition.