It is a technology that directly converts light energy into electrical energy by using the photovoltaic effect at the semiconductor interface. The key component 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 of solar cell modules, and then combined with inverter, power controller and other components to form a photovoltaic power generation device. The advantage of solar photovoltaic power generation is that
it is less restricted by region, because the sun shines on the earth; The photovoltaic system also has the advantages of safety and reliability, no noise, low pollution, local power generation and power supply without fuel consumption and power transmission
lines, and short construction period.
As an electronic product, photovoltaic inverter is composed of multiple devices. Inverter, also known as power regulator, can be divided into independent power supply and grid connection according to the use of inverter in photovoltaic power generation system. According to the waveform modulation mode, it can be divided into square wave inverter, step wave inverter, sine wave inverter and combined three-phase inverter. The inverter used in grid connected system can be divided into transformer type inverter and non transformer type inverter according to whether there is transformer or not.
As the detection center of the whole power station, PV inverter can detect almost all power station parameters from DC components at the top and grid connected equipment at the bottom. Generally, as long as the inverter is in the grid connected state, the power curve displayed by monitoring is a normal "mountain" line, which proves that the power station operates stably. In case of any abnormality, the health status of the supporting equipment of the power station can be checked through the information fed back by the inverter. Here are some common fault analysis and treatment methods of PV inverter:
1. PV inverter screen is not displayed
Fault analysis: there is no DC input, and the inverter LCD is powered by DC.
(1) Insufficient component voltage. 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 connected reversely. The PV terminal has positive and negative poles, which should correspond to each other and cannot be connected reversely with other groups in series.
(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: measure the DC input voltage of the inverter with the voltmeter after use. When the voltage is normal, the total voltage is the sum of the component voltages. If there is no voltage, check whether the DC switch, wiring terminal, cable connector, components, etc. are normal. If there are multiple components, separate and separate access test shall be conducted. If the inverter is used for a period of time and no cause is found, the inverter hardware circuit is faulty. You can contact the manufacturer for after-sales service.
2. The PV inverter is not connected to the grid, and the screen shows that the mains power is not connected
Fault phenomenon: the inverter is not connected to the grid, and the screen shows that the mains power is not connected
Fault analysis: inverter and power grid are not connected
(1) The AC switch is not closed.
(2) The inverter AC output terminal is not connected.
(3) During wiring, the upper row of inverter output terminals is loosened.
Solution: measure the AC output voltage of the inverter with the voltage gear of the multimeter. Under normal conditions, 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 disconnected.
3. The screen shows that the PV voltage is high
Fault 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 single-phase series inverter is 100-500v. It is recommended that the voltage behind the series is 350-400v. The input voltage range of three-phase series inverter is 250-800v. It is recommended that the voltage behind the series is 600-650v. In this voltage range, the inverter has high efficiency and can generate power in the morning and evening when the irradiance is low, but the voltage will not exceed the upper limit of the inverter voltage, causing alarm and shutdown.
4. The screen shows that the PV insulation impedance is too low
Fault analysis: the grounding insulation resistance of photovoltaic system is less than 2 megohm
Possible causes: short circuit of wires to the ground or damage of insulation layer in solar modules, junction boxes, DC cables, inverters, AC cables, terminals and other places. The PV wiring terminal and AC wiring housing are loose, resulting in water ingress.
Solution: disconnect the power grid and inverter, check the resistance of each component wire to the ground in turn, find out the problem point and replace it.
5. The screen shows that the output leakage current is too high
Fault analysis: the leakage current is too large
Solution: remove the PV array input terminal, and then check the peripheral AC power grid. Disconnect all DC and AC terminals, and power off the inverter 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
Fault analysis: the grid voltage is too high. As the grid impedance increases, the photovoltaic power generation user side cannot digest it. When it is transmitted out, the output side voltage of the inverter is too high due to excessive impedance, causing the inverter protection shutdown or derating operation.
terms of settlement:
(1) Increase the output cable because the thicker the cable, the lower the impedance.
(2) When the inverter is close to the parallel node, the shorter the cable, the lower the impedance.