Solis Seminar 【Episode 25】 : Solution for "OV-G-V0X" alarm

Background
In PV systems, grid over-voltage faults (OV-G-V0X) can occur frequently, especially in areas with weak grids and high solar PV grid-connected capacity. Such faults are common and in this episode of Solis seminar, we will share with you the causes of “OV-G-V0X", and how to rectify the issue.

Fault Description
During normal operation of the inverter, it will monitor whether the grid voltage exceeds the grid-tied standard voltage range in real time. If the grid voltage is higher at a certain time, the inverter will be disconnected from the grid and display the error message “OV-G-V0X” (X value 1~4)”.

Types of Error Message and their Meaning
"OV-G-V01": the grid voltage value is higher than the standard Vup01 (standard first step overvoltage value);
"OV-G-V02": the instantaneous grid voltage value is higher than 1.35 times the peak value of the rated AC voltage
"OV-G-V03": the average value of the grid voltage within 10 minutes is higher than the standard value
"OV-G-V04": the grid voltage value is higher than the standard Vup02 (standard second step overvoltage value)

Causes of Grid Over Voltage Errors

PV System Issues
When the "OV-G-V0X" message appears, it is recommended to check the following first:

1) Is the inverter too far away from the grid connection point? This will cause the voltage difference on the AC terminal side of the inverter to increase, which will exceed the voltage range set by the inverter standard
2) Are multiple inverters concentrated in one grid connection point? For example, multiple single-phase inverters connected to the same phase of the grid can cause the voltage of this phase to increase.
3) Are there a lot of solar systems installed in the same area within the power supply range of a transformer? If the grid load consumption capacity is small, the excess electrical power will not be consumed and this will cause the grid voltage to rise.
4) The wiring of the AC breaker is loose.

Figure 1. Loose connection or poorly connected cables

Grid Surge
In addition, we need to confirm whether there is any large-scale electrical equipment in the owner’s electrical load, such as high-power motors, processing machine tools, etc. The switching of this equipment will impact and interfere with the grid, causing excessive grid harmonics and abnormal grid voltage fluctuations, exceeding the tolerance range of the inverter. To protect itself, the inverter will disconnect from the grid and display the “OV-G-V0X” message.

Figure 2. Surge and over-voltages of the grid waveform caused by various load shocks

Possible Inverter Related Causes

1) The inverter grid-standards are set incorrectly and do not meet the on-site grid requirements, resulting in frequent grid over-voltage reports

2) Abnormal internal sampling of the inverter results in a large difference between the displayed grid voltage and the actual value, resulting in the message "OV-G-V0X"

3) Loose connection or poorly connected AC cables of the inverter
 
4) Wiring error, connect line A/B/C to N or PE interface of the inverter AC terminal.

Figure 3. Wiring error, connect line A/B/C to N or PE interface of the inverter AC terminal

Solutions

If Caused by the PV System
1) Select the nearest grid-connected solution; or replace the AC cable with a larger cable
2) Divide the grid-connected capacity of the project evenly on each phase of the grid.
3) For the issue of excessive installed PV capacity in the same area, it is recommended to reduce the capacity of the PV system or increase the capacity of the transformer
4) For the incorrect connection of AC cables, identify the correct and securely phases, neutral, ground and rewire the system.  

If Caused by Grid Surge
1) Check whether there is "GRID SURGE" in the inverter alarm message
Main Menu→Advanced Info→Password 0010→Alarm Message
2) Use an oscilloscope to test the voltage and current waveforms on the AC side of the grid and provide the readings to your local Solis service contact. Solis will provide you with a suitable solution based on the readings.

If Caused by the Inverter setting
1)     Adjust the grid connection standards to match the on-site grid conditions
Setting single-phase inverter grid-tied standard:
A. Main Menu→Advanced Settings→Password 0010→Switch ON/OFF→OFF；
B. Advanced Settings→Password 0010→Select Standard→Select Standard Code→Save & Send；
C. Advanced Info→Password 0010→Running Message→Standard NO.→Standard Code is correct；
D. If the modification is not successful, repeat step B.

Setting three-phase inverter grid-tied standard:
A. Main Menu→Advanced Settings→Password 0010→Switch ON/OFF→OFF；
B. Advanced Settings→Password 0010→Select Standard→Select Standard→Save & Send；
C. Advanced Info→Password 0010→Running Message→Standard NO.→Standard Code is correct；
D. If the modification is not successful, repeat step B.

2)    Set the over-voltage drop power mode to reduce the output power of the inverter through a gradient to stabilize the output voltage and reduce the overall power generation loss.

Setting inverter over-voltage power functions:
Main Menu→Advanced Settings→Password 0010→STD. Mode Settings→Working Mode Set→Work Mode：(Volt-watt→Voltage1~4： P-Limit1~4： )→Save & Send

3)  Abnormal internal sampling of the inverter. Modify the display value of the grid voltage through the compensation parameter setting in the inverter

Setting inverter AC voltage parameters:
Main Menu→Advanced Settings→Password 0010→Compensation Set→Voltage Parameter→Setting value of Vg-A-Zero, Vg-B-Zero, Vg-C-Zero→Save & Send.

If you have any other questions, you can contact Solis support engineers or go to www.solisinverters.com/aftersales.html

Solis is one of the world's largest and most experienced string inverter manufacturers with a global network of service teams.

Summary
Grid over-voltage is a relatively common type of problem. When this fault occurs in a solar PV system, it needs to be eliminated in good time following the above trouble shooting steps. Follow the solutions provided and, if needed, utilize the support of your local Solis support team to restore the system to normal operating conditions.