Fault diagnosis of photovoltaic modules through image processing and Canny edge detection on field thermographic measurements

Abstract

Today, conventional condition monitoring of installed, operating photovoltaic (PV) modules is mainly based on electrical measurements and performance evaluation. However, such practices exhibit restricted fault-detection ability. This study proposes the use of standard thermal image processing and the Canny edge detection operator as diagnostic tools for module-related faults that lead to hot-spot heating effects. The intended techniques were applied on thermal images of defective PV modules, from several field infrared thermographic measurements conducted during this study. The whole approach provided promising results with the detection of hot-spot formations that were diagnosed to specific defective cells in each inspected module. These evolving hot spots lead to abnormally low performance of the PV modules, a fact that is also validated by the manufacturer's standard electrical tests.

Correlation of Infrared Thermal Imaging Results with Visual Inspection and Current-Voltage Data of PV Modules Installed in Kumasi, a Hot, Humid Region of Sub-Saharan Africa

“…They are hard to avoid and it is impossible to quantify their impact on module's performance during their lifetime. In the literature [5], it is reported that as a field module ages and is subjected to thermal and mechanical stresses, repeated relative movement of the crack results in electrical separation and an inactive cell with significant hot spot heating effect.…”

“…A number of studies in the literature [5,12] have reported the defects associated with fielded PV modules as well as in recently installed modules [16,17] using optical and thermal observations. According to IEC 61215 and as reported in the literature [18], the parameters for detecting degradation include defects in insulation and leak currents and visual detection.…”

“…Current PV research focuses on achieving high utilization factors and optimum performance of PV systems. Tsanakas et al [5] report that the performance and lifetime of PV modules are influenced by defects originating either in the module's manufacturing processes or in the field.…”

Hot Spots Detection of Operating PV Arrays through IR Thermal Image Using Method Based on Curve Fitting of Gray Histogram

“…Therefore, the least square method is used to fit the gray level histogram. The gray level histogram provides us with 256 sample points whose coordinates are seen as formula (2) : Based on the characteristics of infrared thermal image of PV module , we can select gray value corresponding to the first 'valley' on the right hand side of the highest peak as the segmentation threshold, so that the hot spots can extracted .The threshold T is set according to formula (4).…”

“…Tsanakas, etc. proposes the use of standard thermal image processing and the Canny edge detection operator as diagnostic tools for module-related faults that lead to hot-spot heating effect [4] . Wang Pei-zhen presents a new method of target feature extracting in view of low contrast of target and background, strong noise and non uniformity in the infrared image and peculiarity of the photovoltaic array.…”