How to deal with the on grid inverter overvoltage problem?

Nowadays, on grid photovoltaic power generation is becoming more and more popular, but most people is still not so familiar with the on gird inverter photovoltaic system, especially the on grid inverter as TV, refrigerator, etc. Even the technicians of some small installation companies can not quickly detect the common faults of inverters. When the on grid inverter has some system fault information feedback, most of them seem helpless. So this article summed up some of the tips to solve the on grid inverter fault for your reference.

In principle, photovoltaic power generation inverters themselves do not generate voltage. The voltage displayed by the on grid inverters comes partly from photovoltaic components called DC voltage, and partly from the grid called AC voltage. What we are discussing today is how to deal with the problem of on grid inverter showing overvoltage.

According to relevant regulations, photovoltaic power generation on grid inverter must work within the specified grid voltage range, which can be monitored in real time and synchronized with the grid voltage. When the on grid inverter is detected that the grid voltage (AC voltage) exceeds the specified range, the on grid inverters must be turned off and stop working in order to ensure the safety of equipment and protect operators Personal safety.

When there are AC overvoltages in on grid inverters, there are three situations:

01. The grid is too far away resulting in voltage rise.

The distance between on grid inverter and on grid station is too far, which will lead to the increase of voltage difference at the AC terminal side of the inverters. When the voltage range of on grid inverter exceeds the prescribed on grid voltage range, the inverters will show the overvoltage of the grid. In addition, the long, thin, winding or irregular material of the cable used to connect the inverters to the grid will lead to the increase of voltage difference at the AC end of the on grid inverters. So the selection and rational layout of the cables are particularly important.

In view of this situation, the first step is to check whether the on grid distance is too long or not, and the best way is to select the scheme that is near the on grid station; the second step is to check the cable distribution and quality, and to select rational wiring mode and qualified AC cable.

02. Multiple on grid inverters are connected with one access point.

In fact, domestic photovoltaic power generation hasn’t lasted for a long time, Power Supply Bureau is not very experienced in the selection of on grid inverter, and sometimes it seems unprofessional or thoughtless. The usual situation is that multiple single-phase inverters are connected to the same phase, which can easily lead to unbalanced grid voltage, and grid voltage rise. There is no doubt that it will lead to on grid overvoltage.

This situation is relatively easy to solve. We need to consider on grid capacity allocation to the three-phase grid, choose multi-points on grid.

03. Photovoltaic power generation capacity of the same area is too large.

With the improvement of national policy and the expansion of photovoltaic financing channels, many people are scrambling to install photovoltaic power generation, which may lead to too much installed capacity of photovoltaic in the same area (the power supply range or area of a transformer) and insufficient load digestibility of power grid. Because the power generated by photovoltaic system is neither consumed nor achieved long-distance transmission, the natural grid voltage will continue to rise, so the on grid inverter will show that the on grid voltage is too high.

The solution to this situation is:

1. Photovoltaic power generation station capacity reduction

2. Transformer capacity increase

3. Prevention: preliminary investigation on the power gird to evaluated the appropriate grid connection capacity (The best method).

What summarized above is the common way to solve the problem of AC overvoltage. Hope it will help you!