Nowadays, photovoltaic grid-connected power generation is becoming more and more popular, but for most ordinary people, the photovoltaic grid-connected system is still not as familiar as the TV refrigerator, especially the grid-connected inverter. Even the technicians of some small installation companies can't quickly check the common faults of the inverter.
When the inverter feeds back some system fault information, most of them will be helpless. Therefore, some tips for solving inverter faults are summarized and are for your reference only.
In principle, the PV inverter itself does not generate voltage. The voltage displayed by the inverter comes from the PV module, called DC voltage, and the other part comes from the grid called AC voltage. What we are discussing today is what to do when "the grid-connected inverter shows the AC overvoltage problem".
According to the relevant regulations, the PV grid-connected inverter must work within the specified grid voltage range, can be monitored in real time and synchronized with the grid voltage. When the inverter detects that the grid voltage (AC voltage) is outside the specified range .The device must be tripped to stop working in order to ensure the safety of the equipment and protect the personal safety of the operator.
When the inverter has AC overvoltage, there are three cases:
1. The grid connection distance is too far, resulting in voltage rise
If the grid-connected inverter is too far away from the grid connection point, the voltage difference on the AC terminal side of the inverter will increase. When the inverter is connected to the grid-connected voltage range, the inverter will display the grid overvoltage. In addition, the cable used by the inverter to the grid point is too long, too thin, entangled or the material is not in compliance, which will lead to an increase in the voltage difference at the AC terminal of the inverter. Therefore, the cable selection and rational layout are used. very important.
In this case, first check whether the grid connection distance is too long, it is best to choose the nearest grid connection scheme; secondly check the cable distribution and cable quality, select the reasonable wiring method and qualified AC cable.
2. Multiple inverters focus on one access point
The domestic photovoltaic power generation has not been in a long time. The power supply bureau has not experienced much when selecting inverters for grid connection, and sometimes it seems unprofessional or unconsidered. It is often the case that multiple single-phase inverters are connected to the same phase, which can easily lead to grid voltage imbalance, and the grid voltage rises, which naturally causes the grid-connected voltage to be too high.
This situation is relatively better to solve, you need to consider the project grid-connected capacity to the three-phase grid, choose multi-point grid.
3. Photovoltaic installed capacity in the same area is too large
As the national policy is getting better and better, the financing channels of PV finance are expanding, and many ordinary people are competing to install. As a result, there may be too many PV installed capacity in the same area (the power supply range or area of a transformer). The grid load digestibility is insufficient. Since the electric energy generated by the photovoltaic system cannot be consumed nearby, and the long-distance transmission point cannot be realized, the natural grid voltage will continuously rise, and the inverter will show that the grid-connected voltage is too high.
The solution to this situation is:
1. Photovoltaic power station derating
2. Transformer capacity
3. Do a good job of prevention: Pre-investigate the grid to assess the appropriate grid-connected capacity (the best method)
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