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Common problems, failure analysis, and solutions displayed on photovoltaic inverters

Mar 11, 2021

Common problems, failure analysis, and solutions displayed on photovoltaic inverters

Although photovoltaic power plants have a long life and a warranty period of up to 25 years, they will more or less always "sick" during the power generation process, so will you "treat" your photovoltaic power plants? If not, you might as well take a look at the following content!




1. There is no display on the inverter screen


 


Failure analysis: There is no DC input, the inverter LCD is powered by DC.


Possible Causes:


(1) The component voltage is not enough. The working voltage of the inverter is 100V to 500V. When it is lower than 100V, the inverter will not work. Module voltage is related to solar irradiance.


(2) The PV input terminal is connected reversely. The PV terminal has positive and negative poles, which should correspond to each other and cannot be connected in series with other groups.


(3) The DC switch is not closed.


(4) When the components are connected in series, one of the connectors is not connected properly.


(5) One component is short-circuited, causing other strings to fail to work.


Solution: Use the meter voltage file to measure the DC input voltage of the inverter. When the voltage is normal, the total voltage is the sum of the voltages of the components. If there is no voltage, check whether the DC switch, wiring terminals, cable joints, components, etc. are normal. If there are multiple components, they must be connected separately and tested separately. If the inverter has been used for a period of time and no cause is found, the hardware circuit of the inverter is faulty, and you can contact the manufacturer for after-sales service.


 


2. The inverter is not connected to the grid, and the screen shows that the mains is not connected


Trouble phenomenon: the inverter is not connected to the grid, and the screen shows that the mains is not connected


Failure analysis: the inverter is not connected to the grid


Possible Causes:


(1) The AC switch is not closed.


(2) The AC output terminal of the inverter is not connected.


(3) When wiring, loosen the upper row of inverter output wiring terminals.


Solution: Use a multimeter to measure the AC output voltage of the inverter. Under normal circumstances, the output terminal should have 220V or 380V voltage. If not, check whether the wiring terminals are loose, whether the AC switch is closed, and whether the leakage protection switch is off. open.


 


3. The screen shows that the PV voltage is high


Failure analysis: high DC voltage alarm


Possible cause: Too many components are connected in series, causing the voltage to exceed the voltage of the inverter.


Solution: Because of the temperature characteristics of the components, the lower the temperature, the higher the voltage. The input voltage range of the single-phase string inverter is 100-500V. The recommended voltage after the string is 350-400V, and the input voltage range of the three-phase string inverter is 250-800V. It is recommended that the voltage after the string is between 250-800V. Between 600-650V. In this voltage range, the inverter has high efficiency and can generate electricity in the morning and evening when the irradiance is low, but the voltage will not exceed the upper limit of the inverter voltage, causing an alarm and shutting down.


 


4. The screen shows that the PV insulation resistance is too low


Fault analysis: the ground insulation resistance of the photovoltaic system is less than 2 megohms


Possible causes: solar modules, junction boxes, DC cables, inverters, AC cables, terminals and other places have wires short-circuited to the ground or the insulation layer is damaged. The PV wiring terminal and the AC wiring housing are loose, causing water to enter.


Solution: disconnect the power grid and inverter, check the resistance of the wires of each component to the ground in turn, find out the problem, and replace it.


 


5. The screen shows that the output leakage current is too high


Fault analysis: Leakage current is too large


Solution: Remove the input terminal of the PV array, and then check the peripheral AC grid. Disconnect the DC terminal and the AC terminal, and let the inverter power off for more than 30 minutes. If you can recover, continue to use it. If you can’t recover, contact the after-sales technical engineer.


 


6. The screen shows that the mains voltage is out of range


Failure analysis: the grid voltage is too high. The grid impedance increases, and the photovoltaic power generation user side cannot digest it, and the output side voltage of the inverter is too high due to the excessive impedance when it is sent out, which causes the inverter to shut down or derate operation.


Solution:


(1) Increase the output cable, because the thicker the cable, the lower the impedance.


(2) The inverter is close to the grid connection point. The shorter the cable, the lower the impedance.