What is an anti-backflow grid-connected box?

"Last year, when I installed household PV, the first grid connection acceptance failed just because I didn't install an anti-reverse power flow grid connection box.

The power grid inspection said that current reverse flow might occur, affecting the stability of the community's power grid.

After installing this box, the acceptance passed at one time, and there were no problems with power generation for half a year!"

Mr. Zhao, a PV owner in Jiaxing, Zhejiang, sighed when talking about his grid connection experience. Nowadays, with the popularization of distributed PV in urban and rural households and industrial and commercial workshops, the anti-reverse power flow grid connection box, as a core equipment to ensure grid connection safety, has gradually entered the public eye and become an indispensable key link in PV system installation.​ Many PV owners may not know why it is necessary to install an anti-reverse power flow grid connection box.

Simply put, the electricity generated by PV panels is prioritized for household use, and the unused electricity can theoretically be sold to the power grid. However, without an anti-reverse flow device, when the PV power generation suddenly exceeds the household electricity consumption, the excess current will "flow back" to the power grid, which may cause fluctuations in grid voltage, frequency imbalance, and even affect the electricity safety of surrounding residents. More importantly, according to the grid connection specifications of State Grid, distributed PV systems must have anti-reverse power flow functions, otherwise they cannot pass the acceptance and cannot generate electricity legally.​

"Before installing the anti-reverse flow device, every sunny noon, when the PV power generation was the highest and the household appliances couldn't use it all, the electricity meter would start to reverse. The power grid staff soon came to the door, saying that this kind of reverse power generation was illegal, and either rectify it or shut down the machine." Manager Li, the person in charge of a factory's PV project, recalled.

Since installing the anti-reverse power flow grid connection box, this problem has been completely solved—it can real-time monitor the PV output current and household electricity load. When the power generation exceeds the electricity consumption, it will automatically adjust the output power of the PV inverter, or directly cut off the grid connection channel of the excess current, ensuring that no current flows back to the power grid.​

In addition to the core anti-reverse power flow function, this grid connection box is also the "safety protection center" of the PV system. It integrates multiple protection components such as circuit breakers, fuses, and surge Protectors. In case of sudden situations such as lightning strikes, short circuits, and overloads, it will trip instantly to cut off the circuit, avoiding damage to PV modules and inverters. Master Wang, a PV installation technician in Hefei, Anhui, said: "Last flood season, a household's PV system was struck by lightning. Thanks to the timely action of the surge protector in the anti-reverse power flow grid connection box, only a small accessory was burned. Without this protection, the entire PV system might have been scrapped."

​ Nowadays, the anti-reverse power flow grid connection boxes on the market also have more intelligent monitoring functions, which are particularly popular among industrial and commercial PV owners. Through the supporting mobile APP or background system, owners can real-time check the PV power generation, self-used electricity, and the operation status of the anti-reverse flow device, and even receive fault alarm reminders. "The PV panels of our factory are installed on the roof.

Before, we had to climb up to check the equipment. Now we can know if there is reverse flow and whether the equipment is operating normally by looking at the mobile phone, which saves a lot of effort in operation and maintenance." Mr. Chen, the person in charge of an electronic factory in Dongguan, Guangdong, said.​

It is worth mentioning that the installation and adaptability of the anti-reverse power flow grid connection box are very user-friendly. Whether it is a small-power PV system of 3-10kW for household use or a high-power system of tens or hundreds of kW for factories, there are corresponding models to choose from. Moreover, the installation process is simple. Generally, it is installed in the outdoor distribution box in conjunction with the PV inverter and electricity meter box, which does not take up space and does not affect the appearance. "Now when installing PV, installation technicians will take the initiative to recommend installing an anti-reverse power flow grid connection box.

The price is not expensive, about a thousand yuan, but it can solve the big problems of grid connection acceptance and safe power generation, with high cost performance." Mr. Zhao said.​

Industry experts said that with the rapid development of distributed PV, the power grid has higher and higher requirements for grid connection safety, and the importance of anti-reverse power flow grid connection boxes will become more prominent. In the future, with technological upgrading, anti-reverse power flow grid connection boxes will also integrate more intelligent functions, such as linking with energy storage batteries to store excess PV electricity, which not only avoids current waste but also further improves the electricity autonomy of households and enterprises. For owners planning to install PV, understanding the role of anti-reverse power flow grid connection boxes in advance and choosing products that meet national standards can make PV power generation legal and safe.