7Impacts on the accuracy of the measurement 17
Accuracy of the peak power calculations from I-V characteristics of PV generators
with the PVPM
Under following constraints the peak power results of the PVPM have an accuracy of +/- 5% relating to the
actual peak power value of the device under test:
● The device under test consists of mono- or polycristalline silicon cells
● The device under test is not (not even slightly) shadowed
● The irradiation reference sensor is not (not even slightly) shadowed
● The irradiation reference sensor must have largely the same spectral sensitivity as the tested device
● The measurement has to be carried out under natural sunlight
● According to IEC60904 the sun has to stand within +/- 10° at right angle to the active surface of the device
under test
● According to IEC60904 an irradiation of at least 800W/m² is required. On the basis of comparative
measurements we found 600W/m² to be sufficient for the PVPM
● The measurement of the irradiation has to take place immediately before/after that of the I-V characteristic,
the time-lag between measurement of characteristic and irradiation should be less than 1ms.
● The measured value of the irradiation reference sensor has to be adjusted with the measured temperature of
the reference cell
● The measurement of the cell temperature has to take place immediately before/after the measurement of
the characteristic within 1second and an accurateness of 1K
● The active surface of the device under test must lie in-plane with the irradiation reference sensor (within +/-
1-2°)
● Before the measurement of the I-V characteristic the irradiation has to be constant enough (+/-10W/m²) for
at least 10 seconds , in that way misinterpretations of the temperature of tested device and reference sensor
can be avoided
● The irradiation must not vary more than 10W/m² during the measurement (PVPM will caution the user in this
case)
● The temperature of the device under test and the reference sensor has got to be balanced (no alteration of
temperature may be indicated)
● Current and voltage of the device under test are measured with distinct measuring lines (four-wire
measurement)
Operation manual for PVPM devices PV-Engineering GmbH
To Next Page
Loading...
Need help?
General