Introduction to Energy Storage Battery Management System
1. Detailed technical solution
The battery energy storage system consists of the energy storage battery, the master controller unit (BAMS), the single battery management unit (BMU), and the battery pack ends control and management unit (BCMU).
2. Internal communication of the energy storage system
2.1 Communication between energy storage BMS and EMS
BAMS uses a 7-inch display screen to display the relevant information of the entire PCS battery pack unit, and transmits the relevant information to the monitoring system EMS via Ethernet (RJ45). The information content includes battery cell information, battery-pack information, and battery cluster information.
Upload information: BMS uploads battery cell (or group) information: cell voltage, battery pack voltage, charge and discharge current, cell maximum SOC, cell minimum SOC, cell minimum SOH; battery pack SOC, cell maximum Temperature, cell minimum temperature, ambient temperature, and battery abnormal alarm, protection and other related information.
Receive information: BMS receives the battery operating parameters issued by the monitoring system EMS, such as voltage protection setting value, alarm setting value, temperature protection setting value, alarm setting value, SOC protection setting value, alarm setting value Wait.
BAMS management server supports MODBUS communication protocol, in which MODBUS needs to define a special protocol point table; the communication interface is network RJ45 communication.
2.2 Communication between energy storage BMS and PCS
Since the PCS only connects to multiple sets of batteries, the BMS data is aggregated to BAMS, and then BAMS communicates with PCS for one-way transmission, with BAMS as the master and PCS as the slave.
BMS sends information: The information sent by BMS includes related information such as battery status and alarms. Including the maximum SOC, minimum SOC of the battery pack, the maximum chargeable capacity of the battery pack, the maximum dischargeable capacity, the ambient temperature, the minimum SOH of the battery, etc. After receiving the BMS alarm information, the PCS shall perform corresponding protection actions.
Communication interface: CAN or RS485 communication interface is used between PCS and BMS.
Hard node information: For timely and reliable protection, the energy storage system reserves hard nodes. When the BMS detects that the battery system reaches the protection limit, the BMS sends the protection limit value to the PCS through the dry node.
2.3 Internal communication of energy storage BMS three-tier architecture
The three-tier architecture of the BMS system is the single battery management layer BMU, the battery pack management layer BCMU, and the battery cluster (multiple groups) management layer BAMS; among them, the battery cluster management layer is also called a PCS battery cell management layer.
Figure 1: Internal communication diagram of the three-tier architecture of energy storage BMS
The single battery management layer is called BMU and has 1 CAN2.0 bus. It is composed of the battery acquisition unit BCU and the battery equalization unit BEU. It collects various cell information (voltage, temperature) of the battery, calculates and analyzes the SOC and SOH of the battery, realizes the active balance of the single cell, and uploads the abnormal information of the cell Give the battery pack unit layer BCMU; use CAN2.0 bus communication mode externally.
The battery pack management layer is called BCMU, with 3 CAN2.0 buses and 2 RS485 (standby) buses. Responsible for collecting various cell information uploaded by the BMU, collecting various information of the battery pack (group voltage, group temperature), charging and discharging current of the battery pack, etc., calculating and analyzing the SOC and SOH of the battery pack, and uploading all the information to the battery Cluster unit layer BAMS; adopts CAN2.0 bus communication mode.
The battery cluster management layer is called BAMS, which has 1 Ethernet, 2 CAN2.0 buses and 1 RS485 (standby) bus. Responsible for collecting various battery information uploaded by BCMU, and uploading all information to the energy storage monitoring EMS system through the RJ45 interface; communicating with the PCS, sending the relevant abnormal information of the battery to the PCS (CAN or RS485 interface), and is equipped with a hardware interface Node to PCS.
2.4 Equalization function of BMS system
The BMS of the battery energy storage system focuses on two aspects, one is the data analysis and calculation of the battery, and the other is the balance of the battery. The battery management system provided by the energy storage power station has a two-way active non-destructive equalization function, with a maximum equalization current of 5A, and an equalization efficiency of over 80%. At the same time, it can effectively screen out abnormal single batteries for alarm for replacement, which can quickly and efficiently improve the battery The consistency of the battery pack improves the efficiency and service life of the battery pack and ensures the normal operation of the entire energy storage system.
Single battery balancing unit:
Due to the production process and other reasons for the single battery, the capacity and performance of each battery are different. In the process of charging and discharging the battery pack, this difference will inevitably increase. When charging, the battery with small capacity and poor performance will be overcharged; When discharging, the battery with small capacity and poor performance will be over-discharged; the capacity utilization rate of the battery pack will become lower and lower. In the long run, this vicious cycle process will accelerate the damage of the battery. Therefore, it is the consensus of domestic and foreign scholars and the industry that power and energy storage battery packs need to use equalization circuits to extend the battery pack life.
The balance system of the battery monitoring module mainly includes four steps: battery information collection → balance rule calculation → balance state output → balanced realization.
2.5 Introduction to the three-level architecture module and installation of the energy storage BMS system
2.5.1 Energy storage system management unit BAMS
BAMS consists of a high-performance 32-bit MCU processor platform, embedded Linux operating system, with a 7-inch TFT touch LCD display, which can upload the lithium battery energy storage system data to the background management in real-time, and can accept background monitoring; independent research and development, Support function expansion and customized services, the communication mode of BAMS and Micronet central control system adopt Ethernet Modbus TCP/IP, the communication interface with PCS is RS-485, and the protocol mode adopts Modbus; the battery can be stored through the remote server via Ethernet. The energy system conducts real-time monitoring and data management, realizes remote measurement, remote signaling, and remote control so that the energy storage system can be maintained in time, ensure the safe operation of the energy storage system, and improve the reliability of the power supply system.
BAMS uses the real-time battery data uploaded by BCMU for real-time display, data calculation, performance analysis, alarm protection, and other processing, and realizes linkage control with PCS and energy storage monitoring background system (EMS), according to the output power requirements and the SOC of each group of batteries Optimize the load control strategy to ensure the optimization of all battery packs.
The energy system master controller monitors the voltage of the single cells online, the terminal voltage of the battery pack, the charging and discharging current, and the temperature, according to the SOC, voltage, temperature, battery pack voltage, temperature, charge, and discharge of every single cell uploaded by the BCMU Current and various abnormal alarm information are displayed. Real-time monitoring and data management of the lithium battery energy storage system through the remote server via Ethernet, realizing remote measurement, remote signaling, and remote control so that the energy storage system can be maintained in time, and the safe operation and reliability of the energy storage system can be guaranteed; reserved; The dry node communicates with the PCS to ensure that the battery system communicates with the PCS under abnormal conditions.
2.5.2 Single battery management module BMU-L3216
The energy storage unit battery management BMU_L3216 module uses advanced measurement technology to accurately measure battery parameters in real-time, such as voltage, current, temperature, and other data, and upload the measurement data to the energy storage system management unit.
Main functions of energy storage battery management module
Ø Online automatic detection of cell voltage, temperature, etc.;
Ø Perform 2A lossless equalization online to achieve charge equalization;
Ø Real-time alarm function to achieve over-limit alarm for voltage and temperature;
Ø On-site alarm, dry node output is closed, remote computer alarm can be realized and the alarm content can be displayed;
Ø With RS485 communication interface, it can be connected to the monitoring system or on-site acquisition unit to realize the upload of data and alarm information to achieve the purpose of remote monitoring of the battery pack;
Ø Adopting modular design, the modules are isolated from each other, and the system reliability is high.
The main indicators of the energy storage battery management module:
Module power supply voltage: DC 24V±10%
Number of battery monitoring sections: 16 sections
Voltage detection range: 0～5.0 V
Voltage detection accuracy: ±0.1%FSR
Temperature measurement accuracy: ±1℃
Lossless equalization current: 2A
Battery balance method: Active and lossless charge balance
Input insulation resistance: ≥5MΩ 500V
Data communication interface: RS485 or CAN2.0
Communication baud rate: 9600bps or 250kbps
On-site display mode: LED working status indication
Size and quality: 250×126×45(mm)/1Kg
Installation method: rack, wall
(A) Explanation of the working principle of the equilibrium system:
u Battery information collection:
Fast and accurate battery information collection is the basis for effective balance; the energy storage battery management module uses a high-speed, high-precision, high-effective bit Σ-Δ 24-bit AD converter, and high-precision (±0.05%) low-temperature drift (± 2PPM) precision benchmark to ensure high consistency and accuracy of battery information measurement in any allowable working environment.
u Balance rule calculation:
The balance rule is to pick out which batteries need to be balanced and how to balance. The calculation of the superior balance rule is the guarantee of effective balance. The equalization rules of the energy storage battery management module integrate relevant factors such as battery pack status, battery voltage, battery SOC, temperature, battery manufacturer, cycle number, etc., so that the calculation results are more in line with actual needs, and discharge, charge and dynamic balance can be achieved.
u Balanced realization:
The equalization realization unit implements equalization on the corresponding battery according to the equalization state output by the equalization rule. The equalization of the energy storage battery management module adopts a lossless charging method, and its charging current can be adjusted according to the requirements of the equalization rules, with a maximum current of 2A; at the same time, it supports an equalization method with a maximum adjustable current of 2A. The battery monitoring module adopts point-to-point equalization.
After using the energy storage battery management module balance management system, the consistency of every single cell during charging and discharging is greatly improved, and the lithium battery pack is effectively balanced.
2.5.3 Battery pack control unit BCMU
The battery pack control unit collects the voltage and current data of the entire battery in real-time, has the function of controlling the on and off of the DC loop, and can detect the status of the on-site alarm equipment in real-time, and upload the data to the energy storage system management unit.
The main functions of the energy storage battery pack control module:
Ø Automatically detect the voltage, current, and ambient temperature of the entire battery pack online;
Ø With DC loop on-off function;
Ø Real-time alarm function to achieve over-limit alarm for the entire group of voltage and current;
Ø On-site alarm, switch detection function, can realize remote computer alarm and display alarm content;
Ø With 3 CAN and 2 RS485 communication interfaces, it can be connected to the battery cluster management unit BAMS to realize the upload of data and alarm information and achieve the purpose of remote monitoring of the battery pack.
