Photovoltaic Module Inspection via Lock-In Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for testing photovoltaic modules require a darkroom and cannot be used on modules with built-in bypass diodes, leading to significant effort and losses during the verification phase.
Innovation Solution
A method and device that modulate an AC voltage onto a photovoltaic module, using a camera with a filter to selectively evaluate electroluminescence and separate interference signals, allowing testing under daylight conditions by employing a digital lock-in method to extract luminescence images from strong background noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electroluminescence imaging is used to test photovoltaic modules, then defects can be detected, but the test must be carried out in a darkroom which requires significant effort and leads to losses
Solution Approach 1:
The patent applies periodic modulation of the excitation signal at a specific frequency, combined with lock-in detection that synchronizes with this frequency. This periodic action allows the system to distinguish the electroluminescence signal from background daylight noise, enabling defect detection without requiring a darkroom environment, thus eliminating verification phase losses while maintaining measurement precision
Solution Approach 2:
The patent introduces an intermediary evaluation device with lock-in detection capability that acts as a mediator between the camera and the defect detection process. This intermediary filters and processes the camera signals to extract the modulated electroluminescence component, enabling accurate defect detection in daylight conditions without the need for darkroom isolation
2Reliability
If conventional electroluminescence testing is used, then quality control can be performed, but the method cannot be used on modules with built-in bypass diodes
Solution Approach 1:
The patent implements a universal testing method that works for all photovoltaic module types regardless of whether they have bypass diodes. The modulated excitation signal and lock-in detection approach can detect defects in both bypass diode and non-bypass diode modules, making the quality control system adaptable to diverse module configurations while maintaining reliability
3Ease of operation
If luminescence imaging is performed under daylight conditions, then testing can be done in operation, but strong background noise from sun and environment interferes with the luminescence signal
Solution Approach 1:
The patent uses periodic modulation of the excitation signal combined with synchronous lock-in detection to extract the weak electroluminescence signal from the strong daylight background. The lock-in detector responds only to signals at the modulation frequency, effectively filtering out ambient noise and maintaining high signal-to-noise ratio while enabling testing under natural daylight conditions
Solution Approach 2:
The patent replaces the mechanical darkroom isolation system with an electronic signal processing system using lock-in detection. This substitution allows the same defect detection capability to be achieved without physically isolating the module from daylight, enabling easy operation during normal working conditions while maintaining measurement precision through electronic noise filtering
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient quality control of photovoltaic modules without the need for a darkroom, effectively separating luminescence signals from interference, and identifying defects such as microcracks and potential-induced degradation with improved signal-to-noise ratio.
Implementation Method 1
the photovoltaic module only being operated in its forward direction... an electroluminescence imaging system is used with which an emission of a sample during operation in the forward direction... is recorded
Implementation Method 2
the camera is preceded by a filter system which is transparent in the wavelength range in which the luminescence signals of the photovoltaic module lie... particularly transparent in the near infrared range (NIR)
Implementation Method 3
evaluating the camera signal generated by the camera using a filter, the photovoltaic module only being operated in its forward direction... a digital filter according to the lock-in method
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates to a method and a device for inspecting photovoltaic modules, wherein the power that a photovoltaic module (12) outputs or draws is modulated (fQ), the photovoltaic module (12) is scanned by means of a camera (26), and the camera signal produced by the camera (26) is evaluated in order to obtain a luminescence image of the photovoltaic module (12), wherein the photovoltaic module (12) is operated only in the forward direction and the camera signal is evaluated by using a filter (24), preferably a digital filter.