Understanding the Origin of Unusual I-V Curves seen in Field Deployed PV Modules

Simulation models for I-V characteristics of PV modules under mismatch conditions often assume ideal bypass diode and ignore the reverse leakage current of cells. In this paper, we present a SPICE based model in which customized reverse leakage current and real I-V characteristics of bypass diodes can be specified. This model is used to gain insight into root causes of some of the unusual I-V characteristics seen in field deployed modules. Different mismatch scenarios for a PV module were simulated for both the modules made up of leaky and non-leaky cells, and the resultant I-V curves were compared. The effect of Potential Induced Degradation (PID) on the I-V curves of PV modules was also simulated under the presence of mismatch. Using this model, we accurately reproduced the I-V characteristics of fielded modules degraded due to PID, and Bypass Diode failure in the short circuit condition.