1. Problem Description
A customer reported that the reactive power output of the SUN2000-60KTL-M0 was abnormal and did not respond to the background reactive power scheduling.
2. Problem Analysis
First. The customer uses the SmartLogger to issue reactive power output commands. Among the nine inverters onsite, the output of six inverters is normal, and the output of three inverters does not respond to reactive power commands.
Second. According to the log and packet information of the SmartLogger, the reactive power command has been delivered to the inverter. Therefore, the SmartLogger is not faulty.
The inverter receives the instruction with PF=0.94 from 2021/3/27 15:09:48 to 2021/3/27 15:22:28. According to the current operating power, the inverter should normally generate more than 10kVA reactive power.
However, the inverter run log shows that the inverter does not generate reactive power.
The DSP log shows that the intelligent QU restricts the reactive power output of the inverter.
Fourth. Check the run logs again. The onsite power grid voltage approaches or exceeds the level-1 overvoltage protection threshold of the inverter. It is suspected that the onsite power grid voltage is too high. To avoid further increase of the power grid voltage, the inverter limits the reactive power output.
Fifth. To verify the speculation, the overvoltage protection threshold is temporarily adjusted to 260 V. Perform the test again. The inverter can execute the reactive power command normally.
Sixth. The grid-tied voltages of the nine inverters on site differ slightly due to grid-tied points. By comparing the grid-tied voltages of the nine inverters on site, the grid-tied voltage of the inverters is lower than the grid-tied voltage of the abnormal inverters when the reactive power command is executed. As a result, some inverters do not execute reactive commands.
3. Fault Locating
Based on log analysis and on-site tests, it is determined that the on-site power grid voltage is close to the overvoltage protection threshold. Therefore, the inverter does not increase the on-site voltage and restrict the inverter's reactive power output.
4. Solution
1. Check whether the voltage at the grid-tied point is too high. If yes, contact the local power operator.
2. If the voltage at the grid-tied point is higher than the allowed range and the local power operator agrees, modify the overvoltage protection threshold.
