Field I-V Curve Measurements Methodology at String Level to Monitor Failures and the Degradation Process: A Case Study of a 1.42 MWp PV Power Plant

Abstract

This research shows the methodology results for outdoor characterization by the I-V curves of the PV power generators at the biggest Brazilian rooftop PV power plant mounted at the Mineirão Football Stadium. The experimental results of the methodology were obtained by a measurement campaign using two capacitive loads. This work identified a significant difference when these measurements were extrapolated to standard test conditions (STC) and compared to the rated power data shown on the PV modules' label at strings: between 24.12% to 26.19% lower. Results showed a contribution of soiling in a power reduction of about 6.7% on average. Additionally, it was considered an uncertain method, and AC electrical parameters were monitored. The reference PV module's calibration was carried out with great attention - the measurements were made with the PV device under test (DUT), guaranteeing the same real operating conditions for the reference PV module and the PV string as DUT. This measurement method has allowed a better characterization of the uncertainty associated with the measurement process. Finally, this study demonstrates the importance of investigating the actual power of the installed PV generators and how these measurements are essential to guaranteeing energy production following the owner's expectations.

Keywords

• PV power plants
• on-site I-V curve measurements
• uncertainty method
• translation to STC
• commissioning/quality assurance
• dust and soiling degradation taxes on PV modules