This issue is crucial in the design and operation of photovoltaic energy storage systems. The core conclusion is that backflow prevention is the core control logic that prevents excess electricity from photovoltaic energy storage systems from flowing back into the public power grid. The core purpose is to provide dual protection—ensuring both the safe and stable operation of the power grid and ensuring that users comply with relevant electricity consumption rules and grid connection requirements.
What is anti-backflow?
nti-reverse current is an indispensable core control function of photovoltaic energy storage systems. The system uses dedicated current sensors to accurately detect the current direction, instantaneous flow rate, and power changes on the grid side in real time. When photovoltaic power generation exceeds the user’s real-time electricity demand, a dynamic adjustment mechanism is automatically activated: either limiting the output power of the photovoltaic modules through the inverter power control module, or switching the charging and discharging state of the energy storage system through the energy storage EMS (Energy Management System), fundamentally preventing excess electricity from “flowing back” into the public grid.
Simply put, it prioritizes the electricity generated by photovoltaic systems to meet the user’s own production and living needs (or prioritizes self-consumption). Any unused electricity is either promptly stored in the energy storage battery bank for backup, or the photovoltaic module’s power generation is actively reduced, ensuring that electricity consumption is entirely completed on the user side, without transmitting excess electricity to the grid.
Why Prevent Backflow?
Ensuring Power Grid Safety and Stability:
Core equipment in the power grid, such as distribution transformers and transmission lines, are designed for rated loads and have fixed safe carrying capacities. Large amounts of backflow power, not handled by the grid, can cause voltage increases and frequency fluctuations in the regional power grid, exceeding equipment safety thresholds. This not only accelerates equipment aging and increases maintenance costs but can also lead to line tripping, equipment failures, and even trigger cascading failures in the regional distribution network.
Compliance with Electricity Policy Requirements:
Most provinces and cities in China have established clear grid connection standards for distributed photovoltaic projects (especially the “self-consumption, surplus power not fed into the grid” model). To avoid overloading the distribution network, power grid companies typically do not allow users to transmit electricity to the grid without approval. Unapproved backflow directly violates the grid connection agreement, and users may face fines, suspension of grid connection qualifications, and other rectification measures.
Avoiding Metering and Billing Disputes:
Traditional public power grid meters are mostly designed for one-way billing, lacking the ability to accurately measure in both directions and distinguish the direction of electricity flow. Backflowing electricity may be mistakenly recorded as electricity drawn from the grid, leading to unnecessary electricity bills. Furthermore, unauthorized reverse transmission of electricity may be misjudged as illegal electricity use, triggering legal disputes related to “electricity theft.”
Optimizing System Operating Efficiency:
The coordinated operation of anti-backflow functions and energy storage systems is key to improving photovoltaic (PV) utilization. Anti-backflow control can store potentially wasted PV energy in battery banks, releasing it during peak demand or when PV power generation is insufficient. This significantly reduces PV curtailment rates, greatly increases self-consumption rates, reduces user dependence on grid power, mitigates the impact of peak-valley electricity price fluctuations, and more fully utilizes clean energy.
