Introduction to Energy Storage Battery Management System

2021-11-22 09:48:08 POWER GEN 18

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 end control and management unit (BCMU).

2. Internal communication of 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, minimum cell temperature, ambient temperature, and battery abnormal warning, protection and other related information.

Receiving 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 unit management layer.

The single battery management layer is called BMU and has 1 CAN2.0 bus. It is composed of battery acquisition unit BCU and battery equalization unit BEU. It collects various cell information (voltage and temperature) of the battery, calculates and analyzes the SOC and SOH of the battery, realizes the active balance of the 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 hardware dry 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 more than 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 of 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.

Main functions of energy storage battery management module

Online automatic detection of cell voltage, temperature, etc.;

Perform 2A lossless equalization online to achieve charge equalization;

Real-time alarm function to achieve over-limit alarm for voltage and temperature;

On-site alarm, dry node output is closed, remote computer alarm can be realized and the alarm content can be displayed;

With RS485 communication interface, it can be connected to the monitoring system or on-site acquisition unit to realize the uploading of data and alarm information to achieve the purpose of remote monitoring of the battery pack;

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