Reliability Evaluation of Failure Diagnosis for I-V Curve Obtained by Advanced Technique
Youichi HIRATA, Takumi AOKI, Keigo NAKASHIMA, Satoru MIYAZAWA
We propose an advanced technique to obtain I-V curves in the first quadrant and the forth quadrant more accurately than by a conventional technique. In this study, we focus on the examination of the irradiance dependence to evaluate I-V curves of modules with different deterioration states. The I-V curves were swept in the first and the fourth quadrant obtained for different irradiances. Then, four constants of an equivalent circuit of the solar cells, i.e., series resistance (Rs), shunt resistance (Rsh), diode factor (n), and saturation current (A), were analyzed. Rs values were obtained for different irradiances and were stable for modules of the same model. Rs can be used to detect the failures and disconnections of modules in a string. Similarly, Rsh, n, and A can also serve as diagnostic indices. To examine the feasibility of using the four constants as diagnostic indices, the values of the four constants were examined for different irradiances.
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