| Possible Cause | Suggestions |
| Cause ID 1: Major The PV string is reversely connected. | Check whether the PV string is reversely connected to the SUN2000. If yes, wait until the solar irradiance declines at night and the PV string current reduces to below 0.5 A. Then, turn off the two DC switches and correct the PV string connection. |
| Cause ID 2: Warning Only a few PV modules are connected in series to the PV string, and therefore the end voltage is lower than that of other PV strings. | Check whether the number of PV modules connected in series to the SUN2000 is small. If yes, increase the number. |
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