In a power system, power is generally sent from the grid to the load, which is called forward current. After installing a photovoltaic power station, when the power of the pv system is greater than that of the load, the power that cannot be consumed will be sent to the grid. Since the current direction is opposite to the conventional one, it is called “countercurrent".

1. What is anti-backflow?

An usual photovoltaic power generation system converts AC to DC. When the power of the photovoltaic system is greater than that of local load, the extra electricity will be sent to the grid. The photovoltaic system with CT(Current Transformer) has anti-backflow function, which means that the electricity generated by photovoltaics is only supplied to loads, preventing excess electricity from being sent to the grid.

2. Why do you need anti-backflow?

There are several reasons for installing an anti-backflow prevention solution:

2.1.Limited by the capacity of the upper-level transformer, users have new grid system installation needs, but it is not allowed locally.

2.2.Due to some regional policies, grid connection is not allowed. Once it is found, the grid company will impose a fine.

2.3.The pv panels have been installed, but due to incomplete filing information (such as unclear real estate property rights, etc.), the grid company does not allow grid connection, and the cost of installing energy storage systems is very high.

3. How to achieve anti-backflow?

Install an meter or a current sensor at the grid-connected point, and feed back the detected grid access point data to the inverter. When it detects that there is current flowing to the grid, the inverter responds quickly and reduces the output power until the countercurrent is Zero, so as to achieve zero power Internet access.

4. The solution?

Deye inverter anti-backflow working principle: install an meter with CT or current sensor at the grid-connected point. When it detects that there is current flowing to the grid, it will feed back to the inverter, and the inverter will immediately change its working mode and track from the maximum power point of MPPT. The working mode is transferred to the control output power working mode, and the output power of the inverter is nearly equal to the load side, so as to realize the anti-backflow function. According to different system voltage levels, photovoltaic anti-backflow systems can be divided into single-phase anti-backflow systems, three-phase and energy storage system ones.