Growatt - Common Inverter Faults And Solutions

As an important component of the entire power station, the inverter is connected to the DC components at the top and the grid-connected equipment at the bottom. Basically, all power station parameters can be detected by the inverter. If an abnormality occurs, the health status of the power station's supporting equipment can be checked through the information fed back by the inverter. The following is a summary of some common fault information and solutions for photovoltaic inverters.

Cause of fault

Indicates that the mains is not connected or the AC circuit breaker is disconnected, causing the inverter to fail to detect the voltage of the mains.

Solution

1. Determine whether the power grid is off. If the power grid is off, wait for the power grid to resume power supply.

2. If the power grid is normal, use the AC voltage range of the multimeter to measure whether the AC output voltage is normal. First measure the inverter output port and check whether there is a problem on the inverter output side. If there is no problem, the external AC side is disconnected. Check the air switch, knife switch, over-voltage and under-voltage protector and other safety switches for damage and disconnection.

Fault cause:

When photovoltaic power generation is connected to the user-side power grid, the voltage at the access point will increase. The greater the internal resistance of the power grid, the greater the increase. The closer to the transformer, the smaller the line resistance, the smaller the fluctuation of the power grid, and the closer to the end of the power grid, the longer the line, the greater the voltage fluctuation.

Therefore, when the inverter is connected to the power grid far away from the transformer, the grid working environment of the inverter will become very poor. After exceeding the upper limit of the inverter working voltage, the inverter will report a fault and stop working.

According to the requirements of the overvoltage/undervoltage protection on the AC output side of the photovoltaic power grid-connected inverter technical specification (NB/T32004-2018): When the voltage at the AC output end of the inverter exceeds the allowable voltage range of the power grid, the inverter is allowed to disconnect the power supply to the power grid, and a warning signal should be issued when it is disconnected. When the grid voltage returns to the allowable voltage range, the inverter should be able to start and operate normally.

Solution:

Try to place the access point of the photovoltaic power station close to the transformer output end to reduce line loss.

2. Try to shorten the line length of the inverter AC output end, or use thicker copper core cables to reduce the voltage difference between the inverter and the grid.

3. Now most grid-connected inverters have AC voltage regulation function. You can contact the manufacturer to widen the AC voltage range to adapt to grid voltage fluctuations.

4. If possible, the output voltage of the transformer can be appropriately lowered.

Fault cause:

The inverter has the function of detecting the insulation impedance of the DC side. When it detects that the DC positive and negative poles have an impedance to the ground lower than 50kQ, the inverter will report "PV insulation impedance is too low fault" to prevent the human body from contacting the live part of the panel and the ground at the same time, causing the risk of electric shock.

Influencing factors include: DC component leakage, cable insulation damage, moisture on the live exposed part, poor grounding of the component bracket, high humidity in the weather and power station environment, etc.

Solution:

Disconnect the AC and DC circuit breaker, use the special MC4 disassembly wrench to remove the positive and negative poles of the DC test string to ensure that the component bracket is reliably grounded, use the multimeter megohm range, connect the red test lead to the positive pole of the string, and the black test lead to the ground, read the measured impedance of each positive pole to the ground, and then connect the red test lead to the negative pole of the string, and then read the impedance of each negative pole to the ground. If it is greater than 50kΩ, it is judged that the insulation of the string is reliable. If it is less than or equal to 50kΩ, it is judged that there is a problem with the insulation of the string. You can check the cable condition of the string separately to see if there is any damage or poor contact. Low insulation impedance usually means that the positive and negative poles are short-circuited to the ground.

Fault cause:

The inverter leakage current detection module detects that the leakage current is too large. To protect personal safety, it stops working and reports the fault information.

1. Disconnect the PV input, restart the machine, and observe whether the machine can return to normal.

2. Check whether the AC ground wire is connected to the live wire, measure whether the voltage between the ground wire and the live wire is normal, or use a leakage current detector to detect.

3. If there is no connection between the ground wire and the live wire, it is likely that the machine is leaking electricity, and you need to contact the manufacturer for processing.

Fault cause:

There are too many series-connected components in a single PV string, causing the voltage to exceed the PV voltage upper limit of the inverter

Solution:

Check the parameters of the inverter, determine the input range of the DC voltage, and then measure whether the open-circuit voltage of the string is within the allowable range of the inverter. If it exceeds the allowable range, reduce the number of series-connected components in the string.

Similarly, if the PV voltage is reported to be too low, check whether the number of series-connected components is too small, or the positive and negative poles of the string are reversed, the terminals are loose and the contact is poor, or the string is broken.

Fault reason

1. There is no DC input or the auxiliary power supply is faulty. The inverter LCD is powered by DC, and the component voltage cannot reach the inverter startup voltage.

2. The PV input terminal is connected in reverse. The PV terminal has positive and negative poles, which must correspond to each other and cannot be connected in reverse with other strings.

3. The DC switch is not closed.

4. One component is broken, causing other strings to fail to work.

Solution:

1. Use the voltage range of the multimeter to measure the DC input voltage of the inverter. When the voltage is normal, the total voltage is the sum of the voltages of each component.

2. If there is no voltage, check the DC switch, terminal blocks, cable connectors, components, etc. in turn to see if they are normal.

Fault reason:

The collector and inverter are not communicating; the collector is not powered on; installation position signal problem; internal reason of the collector.

Solution:

1. Check whether the communication interface between the collector and the inverter is normal, and observe the communication indicator light;

2. Check the local signal strength. If the signal is weak, an enhanced antenna is required;

3. Scan the correct collector serial number;

4. If there is no connection response from the collector when there is no problem with the external conditions, it can be considered that the collector has an internal fault.

The above analyzes the typical problems of inverters in photovoltaic projects and gives some suggestions, focusing on understanding the causes and treatment methods of typical problems. At the same time, in the daily maintenance of power stations, perfect safety protection measures and good standardized operation and maintenance are also the key to ensuring the benefits of power stations.

Growatt Inverter