Common Issues and Solutions in Photovoltaic System Design

February 28, 2024

1. Inverter Screen Not Displaying

Problem Analysis: The LCD screen of the inverter is not powered by DC input.

Possible Causes:

(1) Insufficient module voltage. The operating voltage range for inverters is between 100V to 500V, and they do not operate below 100V. Module voltage is related to solar irradiance.

(2) PV input terminals are connected in reverse. The PV terminals have positive and negative poles that must be correspondingly matched and should not be reversed with other strings.

(3) The DC switch has not been closed.


(4) A connection at a junction of modules in series is not secure.


(5) One module is short-circuited, causing other string(s) not to function as well.

Solution: Use a multimeter on the voltage setting to measure the DC input voltage to the inverter. If the voltage is normal, the total voltage should be the sum of individual module voltages. If no voltage is detected, sequentially check the DC switch, terminal connections, cable joints, and modules. If there are multiple arrays, test them individually.

2. Inverter Not Connecting to Grid

Problem Analysis: The inverter is not connected to the electrical grid.

Possible Causes:

(1) The AC switch has not been turned on.


(2) The AC output terminals of the inverter are not connected.


(3) During wiring, the upper row of the inverter's output connection terminal became loose.

Solution: Use a multimeter on the voltage setting to measure the AC output voltage from the inverter. Under normal conditions, there should be a voltage of 220V or 380V at the output terminals. If there isn't any, check the connection terminals for looseness, verify if the AC switch is closed, and ensure that the leakage protection switch has not tripped.

3. PV Overvoltage

Problem Analysis: An alarm due to high DC voltage.

Possible Cause: Too many modules are connected in series, resulting in a voltage exceeding the inverter's voltage limit.

Solution: Due to the temperature characteristic of modules, the voltage is higher at lower temperatures. For single-phase string inverters, an input voltage range of 100-500V is recommended, with the optimal voltage being around 350-400V. For three-phase string inverters, the input voltage range is 250-800V, with an optimal voltage between 600-650V. Within this voltage range, the inverter operates at higher efficiency, generates power during low irradiance periods, but does not trigger overvoltage alarms leading to shutdown.

4. Isolation Fault

Problem Analysis: The insulation resistance between the photovoltaic system and ground is less than 2 megohms.

Possible Causes: Short circuits to ground or damaged insulation layers exist in solar modules, junction boxes, DC cables, inverters, AC cables, or connection terminals. Water ingress may occur due to loose PV connection terminals or AC connection housing.

Solution: Disconnect the grid, inverter, and inspect each component's wire-to-ground resistance in sequence to locate the problem area and replace it.

5. Leakage Current Fault

Problem Analysis: The leakage current is too large.

Solution: Remove the PV array input and then check the external AC grid. Disconnect both the DC and AC sides, allowing the inverter to remain without power for over 30 minutes. If it can recover, continue using it; otherwise, contact the after-sales technical support engineer.

6. Grid Error

Problem Analysis: Grid voltage or frequency is too low or too high.

Solution: Measure the grid voltage and frequency using a multimeter. If outside the normal range, wait for the grid to return to normal. If the grid is fine, it suggests an issue with the inverter's detection circuit board. As with previous hardware faults, disconnect both DC and AC sides and let the inverter rest without power for more than 30 minutes. If it recovers, resume use; otherwise, contact the after-sales technical support engineer.

7. Inverter Hardware Failure

Categorized into recoverable and non-recoverable failures.

Problem Analysis: Circuit board, detection circuits, power loops, and communication circuits within the inverter have malfunctions.

Solution: Similar to the above hardware fault scenarios, when the inverter exhibits such issues, disconnect both the DC and AC sides and allow the inverter to remain without power for over 30 minutes. If it can recover, continue using it; otherwise, contact the after-sales technical support engineer.

8. System Output Power Too Small

Problem Description: Unable to achieve the desired output power.

Possible Causes: Many factors affect the output power of a photovoltaic power plant, including solar radiation levels, the tilt angle of solar cell modules, shading and dirt, and the temperature characteristics of the components. Incorrect configuration and installation can also lead to reduced system power.

Common Solutions include:

(1) Verify the power of each module before installation.


(2) Adjust the installation angle and orientation of the modules.


(3) Check for shading and dust on the modules.


(4) Ensure that the voltage of the modules in series falls within the specified voltage range; a voltage that is too low will reduce system efficiency.


(5) When installing multiple string arrays, check the open-circuit voltage of each string before installation, ensuring the difference is not more than 5V. If the voltage is incorrect, inspect the lines and connectors.


(6) Install the arrays in batches, recording the power of each batch; the power difference between groups should not exceed 2%.


(7) Poor ventilation around the installation location might prevent the inverter's heat from dissipating effectively, or direct exposure to sunlight could cause the inverter to overheat.


(8) The inverter has dual MPPT inputs, where each input should handle about 50% of the total power. Ideally, the design capacity for each input should be equal. If all modules are only connected to one MPPT terminal, the output power will be halved.


(9) Poor cable joint contact, excessively long cables, or undersized cable diameter can lead to voltage loss and ultimately result in power loss.


(10) The grid-connected AC switch capacity is too small, not meeting the output requirements of the inverter.

9. AC Side Overvoltage

The grid impedance is too high, preventing the photovoltaic power generated from being fully consumed on the user side, and when transmitted outwards, results in an overvoltage on the inverter's output side, triggering protective shutdown or de-rating operation.

Common Solutions include:

(1) Increase the size of the output cable since thicker cables have lower impedance.


(2) Position the inverter closer to the grid connection point as shorter cables have lower impedance.

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