Case analysis of energy balance control of lithium battery pack

Lithium battery energy balance control case study Electric vehicle lithium battery packs generally adopt a multi-cell series-parallel structure. Due to the inconsistency of the battery cells themselves, energy balance control must be performed during the charging and discharging process of the battery pack. The double-layer quasi-resonant switched capacitor balancing method is adopted to realize the automatic balance of series battery energy. After improving the traditional double-layer switched capacitor balancing method, a quasi-resonant soft switch is used to terminate the zero-current conduction and cut-off of the switch. Simulation and experimental results show the effectiveness of the method. Both electric vehicles and hybrid vehicles must be powered by lithium-ion battery packs. The current batteries, whether they are lead-acid batteries or nickel-metal hydride batteries, are lithium batteries. Due to the low voltage of a single battery, multiple batteries must be connected in series and parallel to meet the high-voltage requirements of automobiles. Lithium batteries have the highest energy density among commercial batteries, so they are widely used in electric vehicles and hybrid vehicles. During the processing of fruit lithium batteries, it is impossible for the battery characteristics to be completely consistent. Because of the processing problems and the unevenness of the material, the thickness of the battery plate, the porosity, the activation degree of the active material, and other subtle differences, the inside of the battery The inconsistency of structure and material results in the same batch-processed single battery voltage, battery capacity, internal resistance and other parameters. In addition, in the battery loading operation, due to the different orientation of the battery device, the different heat dissipation state, and the different degree of self-discharge, the inconsistent battery parameters are added to a certain extent. This inconsistency leads to the use of lithium batteries in series, which requires the battery processing system to dynamically balance the charging and discharging energy of the batteries to prevent overcharging or overdischarging of single cells, and to ensure that the maximum capacity of each single cell is appropriate, and then to ensure that the battery Longevity and reliability. The current balancing methods adopted by battery packs are mainly divided into two categories: forced balancing and automatic balancing. Forced balance is also called dissipation balance. Its ending method is to connect a controllable resistor in parallel with each battery to consume the remaining energy of the large-capacity battery and end the voltage balance of the entire battery. The automatic balance of energy transfer balance, the way to end is to transfer the low-energy battery cell of the high-energy battery cell, or the single cell with the lowest energy in the entire battery, in the implementation process, an energy storage link is required, and such energy is transferred from this link. Distribute at the beginning. There are many automatic equalization theories, including equalization using switched capacitor converters. On this basis, a.c. Baughman et al. put forward the theory of double-layer switched capacitors, and proposed the power balance of single-layer switched capacitors. An improved resonant double-layer switched capacitor balance control method is proposed. By using the LC series resonant switched capacitor system, the zero-current turn-on and turn-off of the switch can be terminated, further reducing switching losses, improving electromagnetic interference (EMI) problems and stroke balance power. Disclaimer: Some pictures and content of the articles published on this site are from the Internet, please contact to delete if there is any infringement. Previous: Lithium battery: my country's R u0026 D prospects are optimistic