With the continuous progress of energy storage technology, however, the problem of reverse flow in energy storage systems has always been a difficult problem for users. Countercurrent refers to the phenomenon where excess electrical energy flows back into the grid when the output power of a new energy generation system exceeds the user's electricity demand, which may cause instability or even collapse of the grid system. Preventing the occurrence of counter current problems is called preventing counter current.

In order to prevent backflow problems, anti backflow devices have emerged. This device can monitor the operation status of the power generation system in real time and take corresponding measures when necessary, such as timely cutting off excess power generation branch switches, reducing the output power of power generation equipment, etc., in order to prevent the occurrence of reverse current. During the discharge process of energy storage integrated systems, power fluctuations, changes in load electricity consumption, and other reasons may also lead to energy backflow. The anti backflow scheme can effectively avoid this problem and ensure the safe and efficient operation of the energy storage system. The following are various anti backflow scenarios in various energy storage integrated systems:

1、Low voltage connection of energy storage system for low-voltage anti backflow：The energy storage system is connected to the low-voltage side of the transformer, and the total charging power and load power of the energy storage system are not allowed to exceed the corresponding transformer capacity or maximum demand value, nor is the energy storage system allowed to discharge to the corresponding transformer high-voltage side. So it is necessary to install anti backflow devices on the low-voltage side of the energy storage system.

2、Anti reverse current of multiple transformers under the 10kV bus: Some factories have multiple transformers with different capacities connected in parallel under the 10kV bus. If an energy storage system is installed under one of the transformers, during certain periods, the energy storage system can discharge and be sent to the 10kV bus through the corresponding transformer, and then to the load under other transformers for use. However, it is not allowed for the energy storage system to discharge to the high voltage side of the main transformer. This situation is more common in some larger industrial parks. Due to the varying sizes of transformers in the park, the energy storage system is often only connected to transformers with relatively high electrical loads. When the load under this transformer consumes less electricity, the energy storage system can use this transformer to boost the voltage to the 10KV bus, and then use other transformers to reduce the voltage to the lower load of the transformer. At this point, reverse current can be controlled through low pressure side detection and metering, or through high pressure side detection and metering.

3、The 10KV high-voltage connection of the energy storage system is used for high-voltage anti backflow: 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 to the 10kV busbar through the corresponding transformer, and then sent to other transformers for load use. And it is not allowed for the energy storage system to discharge to the high voltage side of the main transformer. So it is necessary to add anti backflow devices on the 10KV high-voltage side of the main transformer.

4、Multi functional complementary systems for anti backflow: In a multi energy complementary system, the coordinated operation of various energy equipment (such as photovoltaic power generation, wind power generation, energy storage systems, charging piles, etc.) may lead to backflow phenomena. Through reasonable anti backflow design, efficient and stable operation of multi energy complementary systems can be achieved.

In summary, by configuring reasonable solutions in different scenarios, it is possible to ensure stable operation of the system without generating backflow, and save initial investment costs to ensure the safety and reliability of the energy storage system.