Generally, the electricity generated by a photovoltaic system is prioritized for load consumption. When the photovoltaic power generation is greater than the load power consumption, reverse power flow into the grid occurs, known as "reverse current." Power grids have strict regulations regarding the grid connection of photovoltaic power generation, and unauthorized reverse power flow to the grid will face relevant penalties. At the same time, for photovoltaic projects that do not need to be connected to the grid, anti-reverse flow protection is crucial for achieving green energy self-sufficiency.

So, what is anti-reverse flow? What are its working principles and solutions?

01. What is Anti-Reverse Flow?

In a photovoltaic system, the DC electricity output from the photovoltaic modules is converted into AC electricity by the inverter to supply the load. When the power generated by the photovoltaic system is greater than the power consumed by the load, the excess electricity flows back into the grid, creating a "reverse current," because the load cannot consume all the generated photovoltaic power. A photovoltaic system equipped with anti-reverse flow functionality can promptly reduce the inverter's output power when the generated power exceeds the load power. This lowers the overall power generation of the system, ensuring that the photovoltaic-generated electricity is used solely by the load and preventing excess electricity from flowing to the grid.

[Reverse Current Schematic Diagram]

02. Why is Anti-Reverse Flow Installation Necessary?

Generally, there are several reasons why anti-reverse flow installation is required:

• Grid Policy Restrictions: Some regions do not allow grid connection due to policies and grid capacity limitations. Unauthorized reverse power flow to the grid will face relevant penalties.
• Grid Connection Power Limits: The grid has strict limits on grid-connected power. If excess power beyond the limit is directly injected without control, it will impact the grid.
• Self-Consumption, Surplus Power Not to the Grid Principle: Photovoltaic power generation systems need to ensure that the generated electricity is primarily supplied to local loads. If the local load cannot consume all the generated power, anti-reverse flow devices are needed to prevent the excess power from flowing back to the grid. This is where solutions like the Shenzhen HBDTECH PV550 Water Pump Photovoltaic Inverter can play a crucial role in managing power flow for off-grid applications.

03. Working Principle of Anti-Reverse Flow

In practical applications, an anti-reverse flow meter + CT (current transformer) installed on the main busbar of the incoming line is used to obtain real-time power and the magnitude and direction of the current on the line. When a current flowing towards the grid is detected (reverse current), the anti-reverse flow meter transmits the reverse power data to the inverter via RS485 communication. Upon receiving the command, the inverter responds within seconds by reducing its output power. This keeps the current flowing from the photovoltaic power station to the grid consistently close to 0, thereby achieving anti-reverse flow and preventing excess electricity from being sent to the grid. The precise control offered by inverters, including specialized types like the 550 Textile Inverter for industrial applications, is essential for effective anti-reverse flow operation.

04. Anti-Reverse Flow Solutions

KSTAR has consistently focused on the technical application of inverters in photovoltaic projects, combining different devices such as photovoltaic inverters, anti-reverse flow meters, and anti-reverse flow boxes to form anti-reverse flow solutions suitable for various scenarios.

(1) Single-Phase Standalone Anti-Reverse Flow System Solution

• Required Equipment: Photovoltaic grid-connected inverter, anti-reverse flow meter, communication cable between the meter and the inverter. This solution is suitable for residential photovoltaic scenarios.
  

[Single-Phase Standalone Anti-Reverse Flow System Solution Diagram]

(2) Three-Phase Standalone Anti-Reverse Flow System Solution

For small-power grid-connected inverters used in households, a DC anti-reverse flow meter can be directly used. The AC output terminals of the inverter are directly connected to the meter, and from the meter, they are connected to the grid connection point to achieve anti-reverse flow. For high-power grid-connected inverters, it is necessary to use CTs to detect the current on the grid-connected busbar. The current is proportionally reduced by the CTs and then connected to the anti-reverse flow meter to measure the current and power at the grid connection point. This setup can be optimized using advanced inverter technology, such as that found in the Shenzhen HBDTECH PV550 Water Pump Photovoltaic Inverter for larger residential or small commercial applications.

[Three-Phase Standalone Anti-Reverse Flow System Solution Diagram]

(3) Multi-Inverter Anti-Reverse Flow System Solution

Multiple inverters are connected in series through communication interfaces to a data collector. This is suitable for multi-inverter modes, offering more powerful functions and larger capacity. This type of system can also benefit from the integration of specialized inverters like the 550 Textile Inverter in industrial settings where multiple power sources might be involved.

[Multi-Inverter Anti-Reverse Flow System Solution Diagram]

Summary

Anti-reverse flow solutions effectively meet the "grid connection without feeding back to the grid" policy requirements in certain regions. Furthermore, anti-reverse flow can ensure the stable operation of the power grid, enhance system safety, optimize economic efficiency, improve energy utilization efficiency, and adapt to technological developments and policy changes.