INFLUENCE OF THE SWEEP VOLTAGE IN THE MEASUREMENT OF I-V CURVES OF AMORPHOUS SILICON PHOTOVOLTAIC MODULES
DOI:
https://doi.org/10.59627/cbens.2010.1428Keywords:
Solar Energy, I-V curve, Photovoltaic module, Pulsed solar simulatorAbstract
The determination of the electrical characteristics of photovoltaic modules necessarily is performed by means of the I-V (current versus voltage) curve. Although the testing procedures are well described in Brazilian national standards, as well as in the international standards, transient effects that occur during the measurement can affect the final result. The sweep time along with the sweep direction influence the shape of the I-V curve, which can lead to combined uncertainties upper than 5 %. Several measurements in an amorphous silicon module were performed, varying the sweep time and direction, i.e., from Isc to Voc and from Voc to Isc . The measurements taken with variable speed, from 1.4 to 40 ms were compared with a standard curve taken at 50 ms, in both directions. The 50 ms measurement is so called stationary measurement. Results have shown differences up to 3% between maximum power measured at fast rates and at 50 ms ramp. With an ascendant ramp (Isc to Voc) the maximum power is underestimated, and with a descendant ramp (Voc to Isc), the maximum power is overestimated, under fast sweep rates, mainly due to capacitive effects. In order to perform tests in amorphous silicon modules with sweep time lesser than 50 ms, some precautions or later corrections must be performed.
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