Brief analysis of energy storage battery BMS and power AG10 battery

　　1Application scenarios of large-scale energy storage systems

　　New energy power stations, wind power or solar power stations, in order to achieve the purpose of smoothing output power fluctuations, more and more power plants are beginning to be equipped with energy storage systems.

　　Independent energy storage power stations, as the power system reform gradually enters people's field of vision, independent energy storage power stations that make a living by reselling electricity gradually appear.

　　Microgrid is a small power supply and distribution network that includes distributed power sources, power loads, energy storage systems and grid management systems. In order to ensure the continuity and stability of power consumption of the load, each microgrid will be equipped with an energy storage system.

　　2 The difference between energy storage battery management system (ESBMS) and power battery management system (BMS)

　　The energy storage battery management system is very similar to the power battery management system. However, the power battery system in a high-speed electric vehicle has higher requirements for the battery's power response speed and power characteristics, SOC estimation accuracy, and the number of state parameter calculations.

　　The scale of the energy storage system is very large, and there are obvious differences between the centralized battery management system and the energy storage battery management system. Here we only compare the power battery distributed battery management system with them.

　　2.1 The positions of batteries and their management systems in their respective systems are different

　　In the energy storage system, the energy storage battery only interacts with the energy storage converter at high voltage. The converter takes power from the AC grid and charges the battery pack; or the battery pack supplies power to the converter, and the electric energy passes through the converter. Convert it into AC and send it to the AC power grid.

　　For energy storage system communication, the battery management system mainly has information interaction relationships with the converter and energy storage power station dispatching system. On the one hand, the battery management system sends important status information to the converter to determine the high-voltage power interaction; on the other hand, the battery management system sends the most comprehensive monitoring information to the PCS, the scheduling system of the energy storage power station. As shown below.

　　Basic topology of energy storage system

　　The BMS of electric vehicles has an energy exchange relationship with the electric motor and charger at high voltage; in terms of communication, it has information exchange with the charger during the charging process. In the entire application process, it has the most detailed communication with the vehicle controller. Information exchange. As shown below.

　　Electric vehicle electrical topology

　　2.2 Different hardware logical structures

　　The hardware of energy storage management systems generally adopts a two-layer or three-layer model. Larger systems tend to have a three-layer management system, as shown in the figure below.

　　Three-layer energy storage battery management system block diagram

　　The power battery management system has only one layer of centralized or two distributed systems, and there is basically no three-layer situation. Small cars mainly use a one-layer centralized battery management system. The two-layer distributed power battery management system is shown in the figure below.

　　Block diagram of distributed electric vehicle battery management system

　　From a functional perspective, the first and second layer modules of the energy storage battery management system are basically equivalent to the first layer collection module and the second layer main control module of the power battery. The third layer of the energy storage battery management system is an added layer on this basis to cope with the huge scale of energy storage batteries.

　　To use an analogy that is not so appropriate. The optimal number of subordinates for a manager is 7. If the department continues to expand and there are 49 people, then 7 people will have to choose a team leader, and then appoint a manager to manage these 7 team leaders. Beyond personal capabilities, management is prone to chaos.

　　Mapping to the energy storage battery management system, this management capability is the computing power of the chip and the complexity of the software program.

　　2.3 Communication protocols are different

　　The energy storage battery management system basically uses the CAN protocol for internal communication, but its communication with the outside, which mainly refers to the energy storage power station dispatching system PCS, often uses the Internet protocol format TCP/IP protocol.

　　Power batteries and the electric vehicle environment in which they are located all adopt the CAN protocol. They are only distinguished by the use of internal CAN between the internal components of the battery pack and the use of vehicle CAN between the battery pack and the entire vehicle.

　　2.4 Energy storage power stations use different types of batteries, so the management system parameters are quite different.

　　Due to safety and economic considerations, energy storage power stations often use lithium iron phosphate when choosing lithium batteries. Some energy storage power stations use lead-acid batteries and lead-carbon batteries. The current mainstream battery types for electric vehicles are lithium iron phosphate batteries and ternary lithium batteries.

　　Different battery types have huge differences in external characteristics, and battery models are not universal at all. The battery management system and battery cell parameters must have a one-to-one correspondence. The detailed parameter settings of the same type of batteries produced by different manufacturers will not be the same.

　　2.5 Threshold setting tendencies are different

　　Energy storage power stations have more space and can accommodate more batteries. However, some power stations are located in remote locations and have inconvenient transportation. Large-scale replacement of batteries is more difficult. The expectation for battery cells in energy storage power stations is that they have a long service life and should not malfunction. Based on this, the upper limit of the operating current will be set relatively low to prevent the battery core from working at full load. The requirements for the energy characteristics and power characteristics of the battery core do not need to be particularly high. Mainly depends on cost performance.

　　Power batteries are different. In the limited space of the vehicle, it is difficult to install the battery, hoping to maximize its capabilities. Therefore, the system parameters will refer to the extreme parameters of the battery, and such application conditions are harsh for the battery.

　　2.6 The number of state parameters required to be calculated is different between the two.

　　SOC is a state parameter that both need to be calculated. But until today, there is no unified requirement for energy storage systems. What state parameter calculation capabilities do energy storage battery management systems require? In addition, the application environment of energy storage batteries has relatively ample space and a stable environment, so small deviations are not easily perceived in large systems. Therefore, the computing power requirements of the energy storage battery management system are relatively lower than those of the power battery management system, and the corresponding single-string battery management cost is not as high as that of the power battery.

　　2.7 It is better to apply passive equalization conditions to the energy storage battery management system.

　　Energy storage power stations have very urgent requirements for the balancing capabilities of the management system. The scale of the energy storage battery module is relatively large. Multiple strings of batteries are connected in series. The large cell voltage difference will cause the capacity of the entire box to decrease. The more batteries connected in series, the more capacity will be lost. From the perspective of economic efficiency, energy storage power stations need to be fully balanced.

　　And because passive balancing can work better under ample space and good heat dissipation conditions, using a relatively large balancing current does not have to worry about excessive temperature rise. Low-cost passive equilibrium can be used in energy storage power stations.

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