How to handle Reverse Polarity issue

How to handle Reverse Polarity issue

1. Purpose：

The inverter is susceptible to damage from polarity reverse connection. In order to protect the internal circuit, the inverter will active an alarm and stop for functioning to prevent further damage when a polarity reverse connection occurs.

2. Issue description:

The on-site inverter will issue a reverse polarity alarm. Taking the hopeSun110KTL inverter as an example, measure the current of each PV string. When the inverter is not running, PV string2 displays a current of 13A.

The monitoring system is indicating a reverse polarity alarm.

And PV String2 current is indicating the negative current.

The current is being displayed when the inverter is not running.

3. Possible root cause of the issue:

3.1 Reverse of positive and negative polarity.

3.2 The internal switch cable of the inverter is reversed.

3.3 The voltages of the PV strings in the same MPPT are unbalanced.

 4. Checking steps and solution:

4.1 Reverse of positive and negative polarity.

A. Check the current value of each PV strings through monitoring system.

B. Verify for any negative current in the string.

C. Check the actual input current value.

Solution: If the input strings are reversed, exchange the polarities of the stings.

4.2 The internal switch cable of the inverter is reversed.

Check if it is still showing polarity reserved alarm when the sting polarity is correct

Solution: Contact Hopewind service team.

4.3 The voltages of the PV strings in the same MPPT are unbalanced.

  Check if there is significant differences in the PV sting voltages within the same MPPT.

  Solution: Ensure that the PV string voltages are the same within one MPPT.

​Summary: When the string is reversed, the current will not pass through the Boost circuit, but will instead form a circuit inside the string. This allows us to measure the current value even if the inverter is not operational. However, when the string is reversed, the connector should not be unplugged immediately. It’s important to wait for the string current to be less than less than 0.5A before disconnecting.