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Checklist for Troubleshooting Inverters Low Power

1. Check AC Connection: If the installation is new, ensure that the AC cables are properly connected to the terminals of the AC junction box. The polarity is clearly marked on the AC gland.

   
   

2. Inspect MC4 Connectors: Verify that all MC4 connectors are securely in place and that there are no loose connections.

   
   

3. Properly Crimp MC4 Connectors: Make sure all MC4 connectors are correctly crimped to ensure a secure connection.

   
   

4. Measure Open-Circuit Voltage (VOC) of PV Strings: Measure the open-circuit voltage of the PV strings at the connector end after disconnecting the strings from the inverter.

   
   

5. Check Voltage Between PV+ and Ground / PV- and Ground: Use a multimeter to measure the voltages between PV+ and ground, as well as PV- and ground, for all PV strings. The values should decrease within a range of 5% to 95% of a single PV module's VOC. If the voltage remains above a single module's VOC or increases instead of decreasing, there may be a fault in the affected string.

   
   

6. Three-Phase Systems: Check the AC-side voltage between phases, phase to neutral, and neutral to ground. The measurement should be taken from the connector or plug which are directly connecting AC grid to the inverter or AC terminals of the inverter. Note that some customers may mistakenly convert a two-phase system into a three-phase system by shorting phases.

   
   

7. Single-Phase Systems: Check the AC-side voltage between phase and neutral, phase and ground, and neutral and ground. The measurement should be taken at the inverter AC junction box.

   
   

8. Disable DRM: Ensure that DRM is set to "OFF." This setting can be found under "Advanced Settings" > "STD. Mode Settings" > "Initial Settings."

   
   

9. Disable CV Mode: Set CV mode to "STOP." This setting is found under "Advanced Settings" > "Special Settings" > "Constant Voltage Mode."

   
   

10. Disable EPM Device: If no EPM device is being used, disable the fail-safe mode in the internal EPM settings. Also, ensure that the model selection is set to "OFF."

    
    

11. Set Operating Mode to "Null": This setting can be found under "Advanced Settings" > "STD. Mode Settings."

    
    

12. Enable Grid: Activate the grid in the advanced settings. In some newly upgraded HMI inverters, the "GRID-STOP" option may have been mistakenly selected instead of "GRID-ON." Do not use the "GRID-STOP" option.

    
    

13. Check for Panel Shadows: Ensure that no shadows are cast on the solar panels, as this can significantly reduce performance.

    
    

14. Record Complete System Data: Note all relevant information from the menu, including:

    
    

• DC values (DC1, DC2, DC3, DC4)

• Grid voltages (VA, VB, VC, or VGrid)

• Status messages (error codes)

• Total energy generated

  
  

15. Retrieve Advanced Diagnostic Information: Record alarm messages, software versions, current operating messages, and warning messages from the advanced info menu.

    
    

16. Photo Documentation: Take clear and complete photos of:

• ACDB and DCDB in a closed state

• The inverter's serial number (located on the inverter body)

• The entire inverter installation

  
  

Following these steps will help conduct a thorough fault analysis and enable efficient troubleshooting.