Battery system integration design in energy storage projects
Lithium iron phosphate battery system configuration: The lithium iron phosphate batteries (LFP) used in the energy storage components of the system have the characteristics of high specific energy, longer cycle life, larger charge and discharge rates, and safety and pollution-free. They have been widely applied in energy storage fields such as electric vehicles, peak shaving and valley filling, frequency regulation, peak shaving, and emergency backup power. Energy storage batteries generally adopt a modular composition method, with cells forming modules, modules placed in battery boxes, and battery boxes forming battery cabinets to become an energy storage unit. A 2.46MWh battery system is composed of 12 battery clusters of 281.6kWh each; each 281.6kWh battery cluster is formed by 19 battery plug-in boxes connected in series. A 2MWh battery system is composed of 9 battery clusters of 281.6kWh each, with each 281.6kWh battery cluster formed by 19 battery plug-in boxes connected in series.
Battery cluster integration design: For a 2.46MWh battery system, every 19 battery plug-in boxes form a battery cluster, and every 6 battery clusters are connected to a 630kW PCS. For a 2MWh battery system, every 19 battery plug-in boxes form a battery cluster, and every 4-5 battery clusters are connected to a 500kW PCS. Each battery cluster is controlled by a high-voltage box (including BCU) for the input and output of battery power. Through the reasonable configuration and packaging of cells, effective management and full utilization of cells are achieved.
Vanadium redox flow battery system configuration: Vanadium redox flow batteries are safe, environmentally friendly, have a long cycle life, good charge and discharge characteristics, and good uniformity of each single cell. However, flow batteries have low energy density and occupy a large space. A 500kWh battery system is composed of 48 battery clusters of 10.6kWh each, with each 10.6kWh battery cluster formed by one 5.3kW vanadium battery module.
Battery management system design: In this project, a set of energy storage battery management system (BMS) that matches the characteristics of the cells is configured in each 2.46MWh battery container. Each BMS system is managed in three levels: module-level BMU, battery cluster-level MBMS, and unit battery system-level BAMS.
The main functions of each level of BMS are as follows: BMU (module-level, built-in the module): Monitors the voltage and temperature of individual cells, the current of a single module, and the total voltage, and transmits the above information to the upper-level BMS in real time through the CAN protocol. It can control the voltage balance of individual cells. MBMS (battery cluster-level, built-in the central control box): Detects the total voltage and total current of the entire battery cluster, and transmits the above information to the upper-level BMS in real time through the CAN protocol. It can display the capacity and health status of the battery during charging and discharging, and predict power and calculate internal resistance. BAMS (unit battery system-level): Collects information from the lower-level MBMS, and can estimate the remaining capacity and health status of the battery in real time. It communicates with the upper-level and external systems through RS-485 or Modbus-TCP/IP. The general design of the BMS management system framework is shown in the following figure, and the specific design will be further detailed in the next stage.
