Analysis of equalization technology of series lithium-ion battery pack based on power frequency modulation

Lithium-ion batteries have gained rapid development in the feld of frequency regulation of energy storage power stations. In order to meet the voltage and power requirements of the frequency modulation power station, a large number of battery cells need to be connected in series, then battery cells imbalance problem may occur. Moreover, the high rate and frequent switching of the charge and discharge state of battery packs in the frequency modulation process increase the degree of inconsistency, which seriously affects the cycle life and safety performance of the battery packs. In view of the problems mentioned above, this paper summarizes the causes of the inconsistency problem of series-connected lithium-ion battery packs, and evaluates the strategies which are used to improve the consistency of the battery packs. Among them, the balancing topologies are sorted according to the energy flow, while the balancing strategies are based on the different objectives. On this basis, the development trend of equalization technology for lithium-ion frequency modulation battery packs is prospected.