Pseudorandom Sequence Coded Electroluminescence Imaging for Photovoltaic Module Inspection Under Strong Environmental Light

Abstract

The inspection for photovoltaic (PV) module is mainly used in darkroom based on electroluminescence (EL) imaging. To improve the universality and anti-interference characteristic, this aricle proposes a pseudorandom-sequence coded EL (PRC-EL) for PV module inspection under ambient light. In the proposed method, the uncorrelated ambient light is inhibited by an equilibrium sequence, which results in a much higher anti-noise performance for PV inspection. The feasibility of the proposed PRC-EL method is verified mathematically and a prototype system is established in this work. The experimental results show that this method can significantly improve the anti-interference ability of EL detection method. The EL image can be recovered by using a 10 bit industrial camera for outdoor measurements (the peak is 286 $\rm {W}/\rm {m}^{2}$), the 40.8 $\rm {W}/\rm {m}^{2}$ can be tolerated by a low-cost 8-bit camera, suitable for indoor and cloudy environments. Furthermore, the stable high-quality images can be restored continuously using the adaptive-order PRC-EL method under widely varying ambient light conditions. The proposed method can make full use of daily working hours and conditions to perform nondestructive testing and online detection of PV modules, which expands the number of potential application scenarios for EL methods significantly. The proposed method shows major potential to provide improvements in the detailed regular inspection, classification, and performance research of PV modules.