From Battery Cells to EMS, Energy Storage System Design

I. The composition of the battery

 • Positive electrode material (lithium iron phosphate, ternary lithium), negative electrode material (graphite), and aluminum foil as the positive electrode and negative current collector (positive), copper foil (negative), positive and negative pole tabs (that is, led from the current collector).

 • In addition, there are separators, electrolytes, aluminum-plastic films, and battery protection panels.

 • The principle is that when discharging, Li ions migrate from the negative electrode to the positive electrode; and when charging, Li ions migrate from the positive electrode To the negative terminal, it's a rocking chair battery.

• Manufacturing process: rolled type (cylindrical), laminated type (square).

II. Adverse effects caused by parallel connection of cells and battery life protection measures

When different cells are connected in parallel, circulating currents will occur inside the battery. The charging and discharging speeds of each cell are inconsistent, and some cells are overcharged and discharged. As the parallel connection increases, the available DOD will gradually decrease, affecting the output power of the entire battery pack. Due to the constant control of the output power, the current of the cell with large internal resistance is small, and the other cells operate at over-rate, which will affect the performance and life of other cells. 

Measures to extend battery life and ensure safety:

• 1. Battery core: good battery core (good consistency, long cycle life, safe and reliable): the battery factory is responsible.

• 2. BMS (passive balancing, active balancing): BMS manufacturer is responsible;

• 3. Design of energy storage system (battery grouping method, series connection, parallel connection): the design unit, integrator, and research unit are responsible.

• 4. Strengthen testing, experiments, and standard construction: testing institutions and owners are responsible. 

III. Design of energy storage system

Battery cluster (stack) and system: The battery pack (stack) is the energy storage component of the energy storage system and is the basis of the battery energy storage system.

Power converter (PCS): The energy storage power converter converts alternating current from the grid into direct current to charge and store the battery pack (stack) when charging is required, and converts the energy stored in the battery pack (stack) into alternating current to feed back to the battery when discharging is required. Grid device. 

Battery Management System (BMS):

• Components that implement battery parameter (V/I/T) monitoring, battery status SOX calculation, balancing management, fault alarm, protection and communication management for battery clusters (stacks)

• Ensure battery cluster (stack) charge and discharge depth and cycle life, and ensure system safety

Energy Management System (EMS):

• Real-time monitoring of power plant operating status and data storage

• Real-time, reliable, complete data collection system and reliable safety monitoring mechanism ensure the correctness of power station remote control and remote adjustment operations. The energy dispatch management system realizes full life cycle management of energy storage and optimal energy dispatch. System components and auxiliary parts: air conditioning system, container, fire protection system, access control video, gas detection, secondary water fire protection wait.