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Photovoltaic power generation is a technology that directly converts light energy into electrical energy by utilizing the photovoltaic effect of the semiconductor interface. The key element of this technology is the solar cell. After the solar cells are connected in series, they can be packaged and protected to form a large-area solar cell module, and then combined with inverters, power controllers and other components to form a photovoltaic power generation device. The advantage of solar photovoltaic power generation is that it is less restricted by geographical areas, because the sun shines on the earth; the photovoltaic system also has the advantages of safety and reliability, no noise, low pollution, no need to consume fuel and erect transmission lines, and can generate electricity and power locally, and the construction period is short.

As an electronic product, photovoltaic inverter is composed of many components. Inverter, also known as power regulator, can be divided into independent power supply and grid-connected use according to the use of inverter in photovoltaic power generation system. According to the waveform modulation method, it can be divided into square wave inverter, step wave inverter, sine wave inverter and combined three-phase inverter. For inverters used in grid-connected systems, it can be divided into transformer-type inverters and non-transformer-type inverters according to whether there is a transformer.

As the testing center of the entire power station, the photovoltaic inverter is connected to the DC components on the top and the grid-connected equipment on the bottom. Basically, all the parameters of the power station can be detected by the inverter. Generally, as long as the inverter is connected to the grid, the power curve displayed by the monitoring is a normal "mountain" line, which proves that the power station is running stably. If there is an abnormality, you can check the health status of the supporting equipment of the power station through the information fed back by the inverter. The following are some common fault analysis and treatment methods of photovoltaic inverters:

1. The PV inverter screen does not display

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

possible reason:

(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 does not work. Module voltage is related to solar irradiance.

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

(3) The DC switch is not closed.

(4) When the components are connected in series, a certain joint is not connected properly.

(5) One component is short-circuited, causing other strings to not work.

Solution: use the meter voltage range to measure the DC input voltage of the inverter. When the voltage is normal, the total voltage is the sum of the voltage of each component. If there is no voltage, check whether the DC switch, wiring terminal, cable joint, component, etc. are normal in sequence. If there are multiple components, they should be connected 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, you can contact the manufacturer for after-sales service.

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

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

Fault analysis: Inverter and grid not connected

possible reason:

(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 terminals.

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

3. The screen shows that the PV voltage is high

Fault analysis: DC voltage is too high 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 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 between 350-400V, and the input voltage range of the three-phase string inverter is 250-800V. Between 600-650V. In this voltage range, the efficiency of the inverter is high, and it can generate electricity when the irradiance is low in the morning and evening, but the voltage will not exceed the upper limit of the inverter voltage, causing an alarm and shutdown.

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

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

Possible reasons: There is a short circuit of wires to ground or insulation damage in places such as solar modules, junction boxes, DC cables, inverters, AC cables, and terminals. Loose PV terminals and AC wiring housings, allowing water to enter.

Solution: disconnect the power grid and the 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: too much leakage current

Solution: Remove the PV array input and check the peripheral AC grid. The DC and AC terminals are all disconnected, and the inverter will be powered off for more than 30 minutes. If it can be restored by yourself, continue to use it. If it cannot be restored, contact the after-sales technical engineer.

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

Fault analysis: The grid voltage is too high. When the grid impedance increases, the photovoltaic power generation user side cannot digest it, and when it is sent out, the impedance is too large, causing the voltage on the output side of the inverter to be too high, causing the inverter to shut down for protection or derating.

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.