Natong Nanjing Photovoltaic Science Tour---Analyze common photovoltaic power station failures (Inverter)

There is a saying in the photovoltaic industry: 2018 is the first year of distributed photovoltaic power stations. This saying was confirmed at the distributed photovoltaic power generation technology training class held by Photovoltaic Box in Nanjing in 2018! Installers and distributors from all over the country gathered in Nanjing to systematically learn about the construction of distributed photovoltaic power stations.

As an expert in the field of photovoltaic inverters, Natong Energy has been committed to popularizing photovoltaic science. At the Nanjing training class, Lu Bo, technical service manager of Natong Energy, was invited to share his views on inverter selection, intelligent services, and other aspects. After class, he helped the students analyze common problems in photovoltaic power stations and received unanimous praise from the students.

Tips:

1. The inverter screen does not display

Failure analysis:

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

Possible causes:

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

(2) The PV input terminals are connected in reverse. The PV terminals have positive and negative poles, which must correspond to each other and cannot be connected in reverse with other groups.

(3) The DC switch is not closed.

(4) One of the connectors is not connected properly when connecting series and parallel.

(5) A component short-circuit causes other strings to fail to work.

Solution:

Use the voltage range of 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 each component. If there is no voltage, check the DC switch, wiring terminals, cable connectors, and components in turn to see if they are normal; if there are multiple components, connect them separately for testing.

If the inverter has been used for a period of time and no cause is found after checking the external access, it means that the inverter hardware circuit is faulty and you need to contact an after-sales technical engineer.

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 turned on.

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

(3) During wiring, the upper row of inverter output terminals became loose.

Solution:

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

3. Inverter PV overvoltage

Failure analysis:

DC voltage is too high 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 stringing is between 350-400V. The input voltage range of the three-phase string inverter is 200-1000V, and the recommended voltage range after stringing is between 550-700V. In this voltage range, the inverter is more efficient and can generate electricity when the radiation 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. Inverter insulation failure

Failure analysis:

The insulation resistance of the photovoltaic system to ground is less than 2 megohms.

Possible causes:

There are short circuits to the ground or insulation damage in solar panels, junction boxes, DC cables, inverters, AC cables, wiring terminals, etc. The PV wiring terminals and AC wiring enclosures are loose, causing water ingress.

Solution:

Disconnect the power grid and inverter, check the resistance value of each component to the ground in turn, find out the problem point, and replace it.

5. Grid Error

Failure analysis:

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

Possible causes:

In some areas, the rural power grid has not been completely transformed and the grid voltage is not within the safety regulations.

Solution:

Use a multimeter to measure the grid voltage and frequency. If they exceed the limit, wait for the grid to return to normal. If the grid is normal, the inverter detection circuit board is faulty. Disconnect the DC and AC terminals of the machine, let the inverter discharge for about 5 minutes, and then turn on the power. If it can be restored, continue to use it. If not, contact the after-sales technical engineer.