Brief analysis of energy storage battery BMS and power battery BMS

1 Application scenario for large-scale energy storage systems

New energy plants, wind power or solar power stations, are increasingly being equipped with energy storage systems to stabilize fluctuations in output power.

With the reform of the power system, independent energy storage power stations gradually entered people's horizons, and independent energy storage power stations that sell electricity for a living gradually emerged.

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

2 The difference between the energy storage battery management system (ESBMS) and the 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 is in a high-speed electric vehicle, and it has higher requirements for the power response speed and power characteristics of the battery, the accuracy of SOC estimation, and the number of state parameter calculations.

The energy storage system is very large, and the centralized battery management system and the energy storage battery management system are obviously different. Here, the power battery distributed battery management system is compared with it.

2.1 Batteries and their management systems are positioned differently in their respective systems

In energy storage systems, energy storage cells only interact with energy storage converters at high pressures, and the converters take electricity from the AC grid and charge the batteries; Or the battery pack supplies power to the converter, which converts electricity into AC and sends it to the AC grid.

The communication and battery management system of the energy storage system mainly has information interaction with the converter and the power storage station scheduling system. On the one hand, the battery management system sends important state information to the converter to determine the high voltage power interaction situation; On the other hand, the battery management system sends the most comprehensive monitoring information to the dispatching system PCS of the energy storage station.

The BMS of electric vehicles has an energy exchange relationship with motors and chargers at high pressures; In terms of communication, there is information interaction with the charging machine during the charging process, and in the entire application process, there is the most detailed information interaction with the vehicle controller.

2.2 Different hardware logical structures

In the energy storage management system, the hardware generally adopts a two-or three-tier model, and the larger scale tends to be a three-tier management system.

The power battery management system has only one layer of centralized or two distributed, and basically, there will be no three-layer situation. Small cars mainly use a layer of the centralized battery management system. Two Layer Distributed power battery Management System

From the functional point of view, the first and second modules of the energy storage battery management system are basically equivalent to the first collection module and the second control module of the power battery. The third layer of the energy storage battery management system is added to this layer to cope with the huge size of the energy storage battery.

A rather inappropriate analogy. The best number of people in a manager is seven. If the department has been expanding and 49 people have appeared, then seven people have to choose a leader and appoint a manager to manage the seven leaders. Beyond personal ability, management is prone to confusion.

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

2.3 Differentiation of communication protocols

The energy storage battery management system and the internal communication basically use the CAN protocol, but it communicates with the external, external mainly refers to the power storage station scheduling system PCS, often using the Internet protocol format TCP/IP protocol.

Power batteries, where the large environment of electric vehicles adopts the CAN protocol, are only distinguished by the use of internal CAN between the internal components of the battery pack, and the use of the vehicle CAN between the battery pack and the vehicle.

2.4 Different types of power cores used in energy storage plants lead to greater differences in management system parameters

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

The type of battery is different, and its external characteristics are very different. The battery model cannot be used at all. The battery management system and the core parameters must be a one-to-one relationship. The detailed parameters of the same type of core produced by different manufacturers will not be the same.

2.5 Differentiation in the threshold setting

Storage power stations are relatively rich in space and can accommodate more batteries. However, some power stations are remote, inconvenient to transport, and large-scale battery replacement is a difficult matter. The energy storage power station expects a long life and no failure. Based on this, the upper limit of the operating current will be set relatively low, so that the core will not work at full load. Neither the energy characteristic nor the power characteristic of the core need be particularly high. Mainly look at price performance.

The power battery is different. In the limited space of the vehicle, the battery that is not difficult to install is hoping to maximize its ability. Therefore, the system parameters will refer to the limit parameters of the battery, such application conditions are bad for the battery.

2.6 Differences in the number of state parameters required to be calculated

SOC is the state parameter that both need to be calculated. But until today, the energy storage system does not have a unified requirement, and the energy storage battery management system must have the ability to calculate the state parameters. In addition, the application environment of energy storage batteries is relatively abundant, and the environment is stable. Small deviations are not easily perceived in large systems. Therefore, the computing capacity of the energy storage battery management system is relatively lower than that of the power battery management system, and the corresponding single battery management cost is not as high as the power battery.

2.7 Preferred passive equilibrium conditions for the energy storage battery management system

It is very urgent for the energy storage power station to request the balanced capability of the management system. The scale of the energy storage battery module is relatively large, with multiple series of batteries in series. A larger single voltage difference will cause the capacity of the entire box to decrease. The more series batteries, the more capacity they will lose. From the point of view of economic efficiency, it is very necessary to balance the energy storage power station.

Because of the abundant space and good heat dissipation conditions, passive equilibrium can better exert its effectiveness, adopt a relatively large equilibrium current, and do not have to worry about the problem of high-temperature rise. The low-price passive equilibrium can be greatly expanded at the power storage station.

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