The electricity generated by a photovoltaic (PV) system is typically supplied to the load first. When PV power generation exceeds the load’s consumption, the excess power flows back into the public grid; this phenomenon is called “reverse current” or “reverse power transmission.” If the application is for a “self-consumption, surplus power to the grid” model, there is naturally no problem. However, when the PV system is designed for irreversible grid connection, reverse current is prohibited or strictly limited.
National standards such as GB/T 50865 and GB/T 29319-2012, “Technical Regulations for Photovoltaic Power Generation Systems Connected to Distribution Networks,” clearly stipulate anti-reverse current requirements: when a PV system is designed for irreversible grid connection, it should be equipped with reverse power protection devices. When a reverse current exceeding 5% of the rated output is detected, the PV system should automatically reduce its output or stop supplying power to the grid within 2 seconds.
Failure to comply with this rule may result in fines or other policy penalties such as grid disconnection by the power company.
So, how is anti-reverse current implemented? Currently, there are several technical solutions for achieving anti-reverse current functionality. If you have other solutions or if there are any areas where the explanation was inadequate, please feel free to discuss them in the comments section.
Inverter + Anti-backflow meter
This is currently the most widely used solution. An anti-backflow meter (usually used in conjunction with a current transformer to collect current signals) is installed on the main line entering the household. It collects real-time power, current magnitude, and direction data on the bus.
When current is detected flowing towards the grid, the anti-backflow meter transmits the reverse power data to the inverter via RS485 or other communication methods, telling the inverter, “Hey, reduce power generation, we can’t use it all.” Upon receiving the instruction, the inverter responds within seconds, reducing power generation, thus preventing current from flowing into the grid.
However, various communication methods exist, including 4G, Wi-Fi, RS485, and Ethernet. Communication speed and signal delay can affect the final anti-backflow effect.
Using a three-phase unbalanced inverter
When the anti-reverse current meter communication indicates that the inverter is generating less electricity, a problem quietly emerges.
Commercial and industrial loads are often inherently “three-phase unbalanced”: some electrical equipment uses single-phase power, while others use three-phase power. The operating time and power consumption of these devices differ, making it difficult to ensure that the three-phase load is the same.
In anti-reverse current scenarios, some inverters do not support independent phase power control. The system can only limit the overall output based on the smallest phase. This leads to photovoltaic (PV) power curtailment, and the remaining electricity needs to be drawn from the grid. (Regarding the specifics of PV power curtailment, many homeowners have different opinions. Some believe they will not be subject to curtailment, while others have indeed encountered it. We welcome everyone to share their real experiences on this point in the comments section.)
To illustrate, imagine three roads with three warehouses. An inverter allocates 20 empty trucks to each road for transporting goods. However, the amount of goods in the three warehouses differs: road A only needs 3 empty trucks, road B needs 10, and road C needs 20.
A traffic controller is checking at the intersections. Their task is to prevent empty trucks from entering the main roads. When they see an empty truck approaching, they immediately order the inverter (dispatch center) to reduce the number of trucks dispatched.
This results in a large number of empty trucks (due to rationed solar power generation) being idle, while the goods in warehouses B and C (electricity demand) are forced to be transported from another main supplier (the power grid) at high prices by renting (or buying) trucks.
To solve this problem, a more intelligent “traffic dispatch center” is needed, capable of monitoring the “truck demand” on the three roads in real time and dispatching vehicles based on the amount of goods in each warehouse.
Inverter paired with energy storage batteries
A meter or current sensor is installed at the grid connection point. When current flow to the grid is detected, the inverter output power remains unchanged, and the bidirectional converter is activated to store excess energy in the battery. This energy is released when photovoltaic power decreases or load power increases.
The advantages of this solution are:
It fundamentally eliminates the risk of reverse current, meeting grid connection compliance requirements.
It significantly improves the self-consumption rate of photovoltaic power, reducing curtailment.
It enables time-based energy transfer, laying the foundation for subsequent applications such as peak-valley arbitrage and demand management.
Of course, compared to a simple anti-reverse current solution, introducing an energy storage system also means higher initial investment and more complex control strategies, requiring a comprehensive evaluation based on the project’s electricity consumption characteristics, electricity price structure, and investment payback period.
Overall, there is no single optimal solution for anti-reverse current that is universally applicable; the key lies in the project’s grid connection mode, load characteristics, and future energy consumption planning.
The above are some common anti-backflow implementation ideas in engineering. If you have any questions or different approaches, please feel free to contact us for discussion.