The backflow problem in energy storage systems has always been a problem that troubles users. This article mainly discusses various anti-backflow scenarios and corresponding solutions in commercial and industrial energy storage.
1. What is anti-reflux?
Backflow refers to the phenomenon that when the output power of the new energy power generation system is greater than the user’s electricity demand, the excess power will flow back into the power grid, which may cause instability or even collapse of the power grid system. Preventing the occurrence of backflow problems is called backflow prevention.
In order to prevent backflow problems, anti-backflow devices came into being. This device can monitor the operating status of the power generation system in real time and take corresponding measures when necessary, such as promptly cutting off redundant power generation branch switches and reducing the output power of the power generation equipment, thereby preventing the occurrence of reverse flow.
This scenario is very common in photovoltaic systems for self-use. After installing a photovoltaic system with anti-backflow, the power generated by the photovoltaic is only supplied to the local load, and the power generated by the photovoltaic energy storage system can be controlled not to be sent to the grid.
2. Industrial and commercial energy storage backflow prevention scenarios
During the discharge process of industrial and commercial energy storage systems, due to power fluctuations, changes in load power consumption and other reasons, reverse flow of electrical energy may also occur. The anti-backflow solution can effectively avoid this problem and ensure the safe and efficient operation of the energy storage system. Let’s take a look at some typical backflow prevention scenarios for energy storage systems.
Low-voltage access to the energy storage system for low-voltage backflow prevention.
3. Application scenario 1
The energy storage system is connected to the low-voltage 400VAC side of the transformer. The sum of the energy storage system charging power + load power is not allowed to exceed the corresponding transformer capacity or maximum demand value, and the energy storage system is not allowed to discharge to the high-voltage side of the corresponding transformer.
System configuration plan
- On the energy storage system side, Meter 1 is used as a two-way measurement of charge and discharge of the energy storage system;
- Add Meter 2 on the low-pressure side of Transformer 1 for anti-backflow and anti-overload metering testing;
- Load power = Meter 2 power – Meter 1 power. The discharge power of the energy storage system is adjusted in real time according to the load power.
- If there are many load types and frequent changes and fluctuations, in order to achieve more accurate measurement and control, a separate meter can be added to the load side, and the energy storage and discharge power can be adjusted in real time according to the meter power on the load side.
- Multi-transformer anti-reverse flow under 10KV busbar
4. Application scenario 2
Some factories have multiple transformers of different capacities connected in parallel under the 10kV bus. If an energy storage system is configured under one of the transformers, during certain periods of time, the energy storage system can discharge and send it up to the 10kV bus through the corresponding transformer, and then to other transformers.
It is used under load, but the energy storage system is not allowed to discharge to the high voltage side of the main transformer. This situation is more common in some larger parks. Because the transformers in the park have different capacities, the energy storage system is often only connected to the transformer with a relatively large power load. Here are more information about bess manufacturers.
When the load under this transformer uses less power, The energy storage system can step up the voltage to the 10KV bus through the transformer, and then step down the voltage through other transformers for the transformer to load.
Solution 1: Control counterflow through low-pressure side detection and metering
System configuration plan
- Â On the energy storage system side, Meter 1 is used as a two-way measurement of charge and discharge of the energy storage system;
- Add Meter 2 on the low-voltage side of Transformer 1 to perform the overload prevention function of the transformer;
- Add Meter to other transformers;
- Meter 2 ~ Meter N multi-channel calculation sum to prevent backflow.
This plan will add more electric meters. In practical applications, the construction is difficult, mainly due to the new meter wiring and the length of the meter control 485 communication line.
Solution 2: Control counterflow through high-pressure side detection and metering
System configuration plan
- On the energy storage system side, Meter 1 is used as a two-way measurement of charge and discharge of the energy storage system;
- Add Meter 2 on the low-voltage side of Transformer 1 to perform the overload prevention function of the transformer;
- Add a high-voltage Meter 3 on the 10kV side of the main transformer to perform high-voltage anti-reverse flow detection function.
- Meter3 needs to be connected at the high-voltage side. The high-voltage side wiring construction is difficult and requires dedicated personnel. At the same time, PT and CT configuration issues need to be considered.
5. Application scenario 3
The energy storage is boosted to 10kV through a dedicated step-up transformer and connected to the 10kV grid-connected cabinet. The discharge of the energy storage system is sent up to the 10kV bus through the corresponding transformer, and then sent to other transformers for use under the load. And the energy storage system is not allowed to discharge to the high voltage side of the main transformer.
System configuration plan
- On the energy storage system side, Meter 1 is used as a two-way measurement of charge and discharge of the energy storage system;
- Add Meter 2 on the 10kV side of the main transformer for high-voltage anti-reverse flow function.
6. Application scenario 4
In a multi-energy complementary system, the coordinated operation between various energy equipment (such as photovoltaic power generation, wind power generation, energy storage systems, charging piles, etc.) may lead to countercurrent phenomena. Through reasonable anti-backflow design, efficient and stable operation of multi-energy complementary systems can be achieved.
System configuration plan:
- Multi-point countercurrent data collection
By configuring multiple electricity meters to collect countercurrent data on the high and low voltage sides, the electricity meter data is uniformly connected to the EMS coordination control management system, and the EMS issues control instructions to the outside world to achieve a dynamic balance of energy consumption.
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- Develop system energy management strategies
Through refined energy management strategies, the power balance during the charging and discharging process of photovoltaic power generation and energy storage systems is achieved.
According to the real-time load demand and photovoltaic and energy storage system status, the charging and discharging power is adjusted, and a collaborative control strategy is designed to achieve optimized operation among various energy equipment.
Through real-time monitoring of the operating status of each equipment, intelligent scheduling and control are performed to ensure that the system can effectively prevent backflow while meeting load requirements.
7.Summary
The above are common anti-backflow scenarios and corresponding solutions for industrial and commercial energy storage, also such as lithium-ion battery energy storage. By configuring reasonable solutions in different scenarios, it can not only ensure the stable operation of the system without causing backflow, but also save the initial investment cost of the system.
With the continuous expansion of the industrial and commercial energy storage market and technological advancement, anti-backflow solutions are constantly being updated and improved. We need to comprehensively consider various factors and choose solutions with high efficiency and stability to ensure the safety and security of the global energy storage system.
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