The I-V Curve or Current-Voltage Characteristic Curve is a graphical representation that defines the characteristics of an electrical circuit. As the name suggests, I-V curves show the relationship between the current flowing through an electronic device and the voltage applied across its terminals. I-V (current-voltage) curve measurement is one amongst the set of well-established methods used for defect (or fault) diagnosis and performance analysis of Solar-PV installations.
Solar-PV defects can be evaluated at multiple levels – from modules to strings to arrays. A Defect in PV is defined as the module and/or string level phenomenon that can degrade power and/or cause unsafe conditions. Defects can be determined by doing a comparative analysis of “as measured” or “on-field” I-V curve against a “reference” or “baseline” I-V curve. I-V Curve measurements are used to determine the short circuit current (Isc), open circuit voltage (Voc), maximum power (Pmax), fill factor and other parameters that have an impact on Solar-PV performance. The baseline measurement is done with portable IV trace equipment attached to the leads of the module or at the junction box of the string with the use of a reference cell similar to the tested PV, avoiding spectral mismatch to determine global irradiance. The Solar-PV module or string under measurement is then connected to the I-V trace equipment and exposed to sunlight at near-close ideal conditions for on-filed measurement. The two I-V curves measured are then translated to Standard Test Conditions (STC) – 1000 W/m2, 25°C, 1m/s, 1.5AM, as outlined in IEC 60904 standards. The on-field established I-V curve is compared to baseline curve, again both translated to same STC conditions.
Now that you know what I-V curves measurements are, what are you waiting for? Go take your Solar-PV I-V curves measurements. In our next post, we will show how to diagnose Solar-PV defects using the measured I-V curve. Stay Tuned!