Installing photovoltaic panels on your own balcony for power generation is both environmentally friendly and economical. However, you may not know that if not handled properly, self-generated electricity may violate electricity regulations. The key issue is — preventing backflow.

In traditional power supply systems, electricity typically flows from the grid to the user's home, which is called forward current. After installing a photovoltaic power generation system, when the photovoltaic power generation exceeds the household electricity demand, the excess electricity will flow back into the grid, forming a "reverse flow."

Why doesn't the power grid like reverse flow?

Voltage instability: Backflow can cause local grid voltage to rise, affecting the power quality of other users on the same line.

Safety hazards: Potentially endangering the safety of power grid maintenance personnel.

Metering Chaos: Interfering with the power company's metering system, resulting in inaccurate measurements.

According to the "Management Measures for the Development and Construction of Distributed Photovoltaic Power Generation" issued by the National Energy Administration in 2025, large-scale industrial and commercial distributed photovoltaics must choose the self-consumption mode, and grid connection is not allowed. Although household photovoltaics are allowed to feed excess electricity into the grid, some regions (such as Liaoning) also have restrictions on the proportion of grid connection. If it is found that the amount of electricity fed into the grid exceeds 50% within two years, it will be required to set up anti-backflow facilities.

The anti-backflow system is like an intelligent "electricity traffic police," monitoring and controlling the flow of electricity in real time:

Precise Monitoring: Install anti-backflow electric meters and CT transformers on the incoming line side to collect the power, current magnitude, and direction on the bus in real time.

Intelligent Judgment: When current is detected flowing towards the grid (i.e., reverse flow), the meter will immediately send the reverse flow power data to the inverter via RS485 communication.

Quick response: The inverter responds to commands on a second-level basis, quickly reducing output power to ensure that the current flowing to the grid is always close to zero.

This system can achieve dynamic adjustment of "reducing power when there is reverse flow, and increasing output when there is no reverse flow," which not only meets its own electricity demand but also prevents power from being fed back.

For general household balcony photovoltaic power stations, it is recommended to use a single-phase anti-backflow system, which only requires three components:

Installation Highlights:

The CT current transformer is installed at the busbar of the grid connection point, with the P1 side close to the power grid and the P2 side close to the inverter and load.

Ensure that the secondary side of the transformer is not open.

The photovoltaic inverter is connected to the anti-backflow meter via RS485 cable.

This solution is simple and economical, making it very suitable for balcony photovoltaic systems with a power output of less than 5kW.

A: Not at all. The system only limits output when your power generation exceeds your power consumption, and it does not affect normal power usage. When power consumption increases, the system will immediately restore the power generation capacity.

A: No. When there is insufficient power generation on cloudy days, the system will automatically draw electricity from the grid, seamlessly switching without affecting the use of household appliances.

A: Basically maintenance-free. Once the system is running stably, you only need to regularly check if the electric meter display is normal.

A: Most modern systems have dual protection, meaning that even in the event of a communication failure, the inverter itself has basic anti-backflow functionality. The worst-case scenario may be a brief backflow, which will be detected by the grid, but usually, there will not be an immediate penalty; instead, you will be notified for maintenance.

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