With the increasing efforts of the country in the development and utilization of new energy, distributed generation technology and microgrids have also developed rapidly. In order to cope with the large fluctuations and unstable power supply of new energy, and further improve the reliability of power system operation, large-capacity energy storage technology is becoming increasingly important.
The energy storage cell grading and control system divides the energy storage cell into multiple battery clusters connected in parallel to the DC bus. Each battery cluster is composed of several battery cells in series to meet the requirements of the system voltage output. Therefore, each battery cluster can be used as an independent subsystem. When a problem occurs in a cluster, the cluster can be cut off in time, so that the faulty battery cluster does not affect the use of the entire battery system. The management of a particular cluster of batteries can also be divided into multiple battery modules based on the number of series-connected batteries in the cluster. Each battery module includes several battery cells. Managing each battery module separately can reduce the workload of each management unit, improve the response time of the management unit to system faults, and quickly deal with battery failures.
The energy storage cell management system is divided into three levels of management units: the subordinate control unit, the master control unit, and the overall control unit. They correspond to the battery unit, battery module, and battery cluster in the battery system, respectively. This system performs real-time monitoring, safety management, fault alarm, and emergency protection handling of the battery. It also performs safe and optimized control of the battery module, battery cluster, and battery system to ensure the safe, reliable, and stable operation of the battery.
The subordinate control unit mainly includes MCU, battery voltage acquisition module, battery temperature acquisition module, balance module, thermal management module, and communication module. The MCU serves as the unit controller, real-time monitors the voltage of the energy storage cell cells through the voltage detection module, and balances the battery cells using active balancing module based on the collected voltage information. The temperature detection module measures the temperature of the battery and controls heating and cooling of the battery using the thermal management module. The subordinate control unit communicates with the master control unit via the CAN communication module, and uploads real-time battery voltage, temperature information, and battery alarm information.
The voltage detection module consists of two sets of chips, each chip can collect the voltage information of 12 series cells. The module can collect information from a maximum of 24 series battery cells. In order to cope with the capacity barrel effect caused by the uneven voltage of the batteries in the group, the balance module of the subordinate control unit adopts active balancing technology to balance the batteries in the group, transferring the charge from high voltage cells to low voltage cells to ensure the consistency of the battery voltage and increase the battery capacity.
The subordinate control unit is connected to the master control unit via the CAN bus. Each subordinate control unit uploads its own battery voltage and temperature information according to the information request from the master control unit. The temperature and voltage exceeding the limit value are actively uploaded. This enables timely reporting and handling of failures.
The master control unit is responsible for managing several subordinate control units on a battery cluster. It obtains the information of the battery cells in this cluster by sending a request command and receives the alarm information actively uploaded by the subordinate control units. It calculates the charging and discharging current of the battery group of this cluster using the current detection module and calculates the remaining battery capacity of the battery group. It controls the switch of the battery cluster on the DC bus using a controllable switch. It disconnects the connection with the bus when it detects that the battery is fully charged, and closes the switch to charge the battery when it detects that the battery capacity is insufficient. At the same time, it quickly responds to the power demand issued by the overall control unit, closes the switch to supply power to the equipment on the bus. The master control unit can also disconnect the control switch in a timely manner based on the alarm information uploaded by the subordinate control units, achieving the isolation of the faulty battery cluster from the DC bus and ensuring the reliability and safety of the system.
The overall control unit of the energy storage cell is responsible for managing multiple master control units. The overall control unit has on-site display function, can display all individual battery information in the system through a touch screen display system, and performs safe and optimized control of the operation of the battery module, battery cluster, and battery system, ensuring the safe, reliable, and stable operation of the battery. The touch screen can also be used to configure parameters. It can not only modify the parameters of the unit itself, but also issue commands through the CAN bus to modify the parameters of the master control and subordinate control units. The overall control unit has powerful communication capabilities, with multiple RS485 and CAN bus interfaces. It realizes communication with the background monitoring system and the power conversion system (PCS), uploads system information in real-time, and receives monitoring instructions from the monitoring backend and PCS.
In this article, a hierarchical management and control system for energy storage batteries is introduced. This system divides the management of energy storage batteries into three levels, suitable for large-scale energy storage systems. It has fast response to system faults and improves system security and stability.