Introduction To Battery Management System of Battery Energy Storage System

                                                                                  Battery Management System (BMS)

      A complete electrochemical energy storage system mainly consists of battery pack, battery management system (BMS), energy management system (EMS), energy storage converter (PCS) and other electrical equipment.

      In the energy storage system, the battery pack feeds back the status information to the battery management system BMS, and the BMS shares it with the energy management system EMS and the energy storage converter PCS; the EMS sends the control information to the PCS and BMS based on optimization and scheduling decisions. , control the single cell/battery pack to complete charging and discharging, etc.

Battery management system BMS: plays a sensing role and is mainly responsible for battery monitoring, evaluation, protection and balancing;

Energy management system EMS: plays a decision-making role and is mainly responsible for data collection, network monitoring and energy scheduling;

Energy storage converter PCS: plays an executive role, and its main function is to control the charging and discharging process of the energy storage battery pack and perform AC to DC conversion.

• What is battery management system BMS

      The full name of BMS is Battery Management System. It is a device that monitors the status of energy storage batteries. It is mainly used to intelligently manage and maintain each battery unit; to prevent overcharging and over-discharging of the battery and extend the service life of the battery; and to collect battery information in real time. Status information, upload data to the background for remote monitoring. It is one of the core subsystems of the energy storage battery system.

• BMS system three-layer architecture:
  

1) Bottom layer: slave BMU - single battery management layer. It is composed of a battery monitoring chip and its auxiliary circuits. It is responsible for collecting various information of a single battery, calculating and analyzing the SOC (battery remaining capacity) and SOH (battery health status) of the battery, achieving active balancing of the single battery, and balancing the single battery. Body abnormality information is uploaded to the main control.

2) Middle layer: Main control BCU - battery pack management layer. Collect various single battery information uploaded by BMU and collect battery pack information. Calculate and analyze the SOC and SOH of the battery pack.

3) Upper layer: General control - battery cluster management layer. Responsible for the overall coordination within the system and external information interaction with EMS and PCS, and controlling the operation process of the entire BMS system according to external requests.

• Specific functions of battery management system BMS

• Cell voltage balancing function

      This function is to correct the voltage or energy dispersion caused by the process differences of the battery cells in the series battery pack, and to prevent the battery performance from deteriorating or even being damaged due to overcharging or over-discharging of individual cells. All individual battery voltage differences are within a certain reasonable range. The error between each battery is required to be less than ±30mv.

• Battery pack protection function

Single battery overvoltage, undervoltage, overtemperature alarm, battery pack overcharge, overdischarge, overcurrent alarm protection, cut-off, etc.

• Data collection function
  

The data collected mainly include: single cell voltage, single cell temperature, pack terminal voltage, charge and discharge current, and the battery internal resistance is calculated.

• SOC/SOH diagnostic function

      Based on the real-time measurement of battery module voltage, charge and discharge current, temperature, single cell terminal voltage, calculated battery internal resistance and other parameters, the diagnosis of the current capacity or remaining capacity (SOC) of the single battery is obtained by analyzing the diagnostic model. Diagnosis of body battery state of health (SOH), assessment of battery pack condition, and estimation of sustainable discharge time in the current state at the time of discharge.

• Thermal management

      During the charging process, the battery module will generate a large amount of heat energy, causing the temperature of the entire battery module to rise. Therefore, BMS thermal management came into being.

• Troubleshooting and fault tolerance

      In case of an abnormality, the BMS will give a fault diagnosis alarm signal and send it to the upper-level control system through the monitoring network to determine the faulty battery and its location, give an alarm signal, and take appropriate measures to deal with these batteries. Among them, technologies such as battery bypass or energy transfer can prevent single battery failure from affecting the operation of the entire battery pack.

• Application of laser welding process

      Laser welding refers to a welding method that uses the heat of a laser beam to melt and fuse workpieces. Specifically, it uses the high power energy and excellent directivity of the laser beam to work. The laser beam is focused on a small area through the focusing system in the laser welding machine, and the energy height is formed in the welding place in a very short time. The concentrated heat source area melts the object to be welded and forms a strong welding point and welding seam.

     In the process of lithium battery production, such as cell manufacturing, PACK manufacturing, and the connection process of the battery management system (BMS), the application of laser welding technology greatly improves the precision, efficiency, and reliability of product manufacturing.

Function upgrade: In-depth integration of big data management and cloud-edge collaboration

•   BMS equipment is an important part of building a cloud-edge energy storage system big data platform and in-depth mining analysis function.

     At present, BMS functions have developed from basic functions such as monitoring, communication, protection, display, and storage to advanced functions such as battery system safety diagnosis, longevity maintenance, and system economic index diagnosis. From a technical point of view, active balancing technology will become the standard, and big data, artificial intelligence and other technologies will be applied to battery status algorithms; the living space of low-end BMS suppliers will become smaller and smaller in the future. Smart operation and maintenance, advanced functions, etc. are the core points for differentiated competition among manufacturers in the future.

Edge: Develop cloud-edge collaboration based on BMS, give full play to the data aggregation capabilities of BMS, realize the collection, analysis, status diagnosis and evaluation of real-time data of the battery system on the station-level equipment side, and realize data cleaning and pre-processing.

Cloud: Based on more station-side data, the cloud realizes multi-dimensional spatio-temporal data mining, refining, and finishing, achieving more detailed and comprehensive assessment of battery operating status, safety status, and energy storage system reliability, and dynamically optimizing BMS operation strategies and The algorithm model is also set down to the equipment side to achieve the best safe and economical operation and maintenance model, realize intelligent operation and maintenance, and provide data support for energy aggregation/distribution/transaction, and provide guarantee for the value realization of the energy storage system.