Solar Cell String Defect Detection via Terminal Impedance
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Solution Overview
Problem
Existing inspection techniques for photovoltaic power generation systems are inefficient in determining defects in multiple locations of a solar cell string, as they require individual inspection of each solar cell module and bypass diode, making it difficult to identify defects across the entire string.
Innovation Solution
An inspection apparatus that applies an AC inspection signal to both the positive and negative terminals of a solar cell string, measuring impedance values to determine the presence and location of defects by comparing measured index values to reference values, allowing for the identification of multiple defects within the string using a single inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual inspection of each solar cell module and bypass diode is performed, then measurement precision of defect locations is improved, but device complexity and inspection time increase
Solution Approach 1:
The solar cell string is segmented into multiple sections based on the number of solar cell modules, and inspection is performed by applying signals to positive and negative terminals separately. This segmentation allows comprehensive defect detection without requiring individual inspection of each module, reducing system complexity while maintaining measurement precision.
Solution Approach 2:
The inspection apparatus uses a universal measurement method that can detect defects in multiple locations simultaneously by measuring index values from both terminals. This multi-functional approach replaces the need for separate inspection devices for each module, reducing overall device complexity while maintaining comprehensive defect detection capability.
2Measurement precision
If individual inspection of each solar cell module is performed, then defect detection accuracy is improved, but inspection time and productivity decrease
Solution Approach 1:
The inspection process is segmented into two terminal-based measurements (positive terminal and negative terminal) that collectively provide comprehensive defect detection for the entire string. This segmentation approach achieves complete coverage in parallel, improving productivity while maintaining defect detection accuracy through the combined index value analysis.
Solution Approach 2:
The inspection method merges the inspection of all solar cell modules into a single measurement process by combining index values from both terminals. This merging allows simultaneous detection of multiple defects throughout the string, dramatically improving inspection efficiency while maintaining accurate defect location identification through the combined data analysis.
3Reliability
If comprehensive inspection of multiple locations is performed, then defect detection capability is improved, but ease of operation deteriorates
Solution Approach 1:
The complex task of inspecting multiple locations is segmented into two simple terminal-based operations: applying signal to positive terminal and applying signal to negative terminal. This segmentation simplifies the operator's task while maintaining comprehensive defect detection capability, as the system automatically processes the segmented measurements to identify all defects.
Solution Approach 2:
The inspection apparatus performs automatic defect detection and location identification by itself, eliminating the need for operators to manually inspect each module. The system self-services by automatically measuring index values from both terminals, processing the data, and identifying defect locations, thereby improving ease of operation while maintaining high defect detection capability.
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 detection of defects in multiple locations within a solar cell string, reducing the need for individual module inspections and improving the accuracy of defect identification and location determination.
Implementation Method 1
measuring impedance values to determine the presence and location of defects by comparing measured index values to reference values
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A defect number determination unit (47) determines whether or not a solar cell string (3) is defective in a plurality of positions on the basis of whether or not a combined impedance found from impedances in the case where an inspection signal is applied to a P terminal and an N terminal of the solar cell string (3) deviates from a reference impedance by greater than or equal to a predetermined threshold. This makes it easy to determine whether or not the solar cell string is defective in a plurality of positions.