Customer feedback that a SUN2000-40KTL-M3 inverter shows "On-grid: self derating" status during operation, which affects the normal power generation, hoping to get our help.
Troubleshooting Process and Fault Location
After analyzing the inverter logs, we see that the inverter does have an "On-grid: self derating" status
By looking at the Fusionsolar data, we see that the current curve of this inverter clearly shows a clipping state at noon, and the inverter is in an "On-grid: self derating" state.
During the time when the inverter is in "On-grid: self derating", the voltage of each string at the DC end of the inverter is shown as follows.
The voltage range of full-load MPPT of SUN2000-40KTL-M3 is 540V~800V. The voltage of PV1, PV2, and PV3 strings of the inverter is about 640V, and the voltage of PV5, PV6, PV7, and PV8 strings is about 480V. When the load is high, the PV5, PV6, PV7, and PV8 voltage can not reach the full-load MPPT voltage requirement, there is a derating situation, and the PV5, PV6, PV7, and PV8 power curve shows obvious clipping. At this time, the inverter shows as “On-grid: self derating”.
It can be seen that the reason for the inverter's "On-grid: self derating" status is that some of the string voltages are low to meet the full-load MPPT voltage requirement of the inverter, which leads to the inverter's self derating situation.
Reconfigure the inverter strings on site so that each string meets the full-load MPPT voltage requirements.