AC Voltage Offset Procedure and Firmware Requirements

If an AC voltage sensor is faulty and resulting in a discrepancy between the actual voltage and the voltage measured by the inverter, it can cause false UN-G-V or OV-G-V faults.  Inverters manufactured after July 9, 2018 will allow the inverter AC voltage measurements to be offset by a user-defined value up to +/- 5 V.


Inverters manufactured prior to July 2018 are likely running firmware that doesn't support voltage offsets.  Voltage offset capabilities were added to DSP ver 23 on 2018.6.16 and HMI ver 0E on 2018.7.09.  So as long as the HMI firmware is version 0E or above (including Sunspec) and DSP is version 23 or above, offsets should already be allowed.  Otherwise, the firmware will need to be updated to allow voltage offsets to be applied.


After the firmware is uploaded successfully, you'll need to complete the following steps to perform the voltage offset.  Leave the AC switch "off" and the DC "on" until directed otherwise.


To determine the voltage error for each phase:
  1. Measure the voltages of phase 1 and check the voltage according to the inverter. This has to be done at the same time -- the two displays should be showing the values right next to each other. We recommend taking photos showing the inverter reading and multimeter measurement in the same photo.
  2. Record the measured voltage vs the inverter voltage and calculate the error (Error = Vmeasured – Vinverter).
  3. Repeat steps 1-2 for phase 2.
  4. Repeat steps 1-2 for phase 3.

To apply voltage offsets on 25-40K models:
Do the following to set the offset on the inverter:
  1. Press ENTER to open the menu.
  2. Scroll DOWN to Advanced Settings and press ENTER.
  3. Type in the password (0010) by pressing DOWN, DOWN, UP and ENTER.
  4. Scroll to Special Settings --> VgSet and press ENTER.
  5. Scroll DOWN to Voltage parameter and press ENTER.
  6. Set the offset values for each respective phase, according the previously calculated voltage error. [If the inverter display is higher than measured (false OV-G-V faults), the offset value will be negative (-). If the inverter display is lower than measured (false UN-G-V faults), the offset value will be positive (+).]
  7. Press ESC, then ENTER to save and send.
  8. Power cycle the inverter, and compare the AC voltages measured by multimeter with the voltages displayed by the inverter. If still not within 2 volts of each other repeat the calibrating process.
  9. Observe the inverter generating to verify normal operation prior to leaving site (compare to neighboring inverters if identical).

To apply voltage offsets on 50-66K models:
Do the following to set the offset on the inverter:
  1. Press ENTER to open the menu.
  2. Scroll DOWN to Advanced settings and press ENTER.
  3. Type in the code (0010) by pressing DOWN, DOWN, UP and ENTER.
  4. Scroll UP to Compensation Set and press ENTER.
  5. Scroll DOWN to Voltage parameter and press ENTER.
  6. Set the offset values for each respective phase, according the previously calculated voltage error. [If the inverter display is higher than measured (false OV-G-V faults), the offset value will be negative (-). If the inverter display is lower than measured (false UN-G-V faults), the offset value will be positive (+).]
  7. Press ESC, then ENTER to save and send.
  8. Power cycle the inverter, and compare the AC voltages measured by multimeter with the voltages displayed by the inverter. If still not within 2 volts of each other repeat the calibrating process.
  9. Observe the inverter generating to verify normal operation prior to leaving site (compare to neighboring inverters if identical).
J
John is the author of this solution article.

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