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Analysis of common failures of photovoltaic inverters

Mar 11, 2021

Analysis of common failures of photovoltaic inverters

1. There is no display on the inverter screen


Failure analysis:


Without DC input, the inverter LCD is powered by DC.


Possible Causes:


(1) The component voltage is not enough, the input voltage is lower than the starting voltage, and the inverter does not work. Module voltage is related to solar radiation.


(2) The PV input terminals are connected reversely. The PV terminals have 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) One of the connectors is not connected properly when the series is connected in parallel.


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


Solution:


Use a 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 the components. If there is no voltage, check whether the DC switch, wiring terminals, cable joints, and components are normal in sequence; if there are multiple components, they must be connected and tested separately.


If the inverter has been used for a period of time and the external access conditions are not found to be the cause, the hardware circuit of the inverter is faulty and you need to contact after-sales technical engineers.




2. The inverter is not connected to the grid


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, the upper row of inverter output wiring terminals is loose.


Solution:


Use a multimeter to measure the AC output voltage of the inverter. Normally, the output terminal should have 220V or 380V voltage. If not, check whether the wiring terminal is loose, whether the AC switch is closed, and whether the leakage protection switch is open.

3. Inverter PV overvoltage


Failure analysis:


High DC voltage alarm.


Possible Causes:


Too many components are connected in series, causing the voltage to exceed the upper limit of the inverter's input voltage.


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 50-600V, and the recommended voltage range after the string is 350-400, and the input voltage range of the three-phase string inverter is 200-1000V, and the string is recommended The subsequent voltage range is between 550-700V. In this voltage range, the inverter has high efficiency and can generate electricity sooner or later when the radiation is low, but it will not exceed the upper limit of the inverter voltage, causing an alarm and shutting down.




4. Insulation failure of inverter


Failure analysis:


The insulation resistance of the photovoltaic system to the ground 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 value of each component to the ground in turn, find out the problem, and replace it.


Five. Grid error


Failure analysis:


The grid voltage and frequency are too low or too high.


Possible Causes:


Rural power grids in some areas have not been transformed, and the grid voltage is not within the scope of safety regulations.


Solution:


Use a multimeter to measure the grid voltage and frequency, if it exceeds, wait for the grid to return to normal. If the grid is normal, the inverter detects the circuit board failure, disconnect the DC and AC terminals of the machine, and let the inverter discharge for about 5 minutes before turning on the power supply. If you can continue to use it, if you can’t, contact After-sales technical engineer.