Two-stage balance control circuit, system and policy for charge and discharge of lithium battery packs

Abstract

The invention discloses a two-stage balance control circuit, system and policy for charge and discharge of lithium battery packs. The balance control circuit comprises a symmetrical multi-winding transformer and DC-DC converters; the system comprises the lithium battery packs and the two-stage balance control circuit for charge and discharge of the lithium battery packs, connected with the lithium battery packs; the two-stage balance control circuit comprises a data acquisition circuit, a balance circuit, a controller and a driving circuit; according to the control policy, balance control between single lithium batteries in the lithium battery packs is performed firstly; and then balance control between the lithium battery packs is carried out. According to the method, the DC-DC converters are used for performing balance between the single lithium batteries and the improved symmetrical multi-winding transformer is used for performing balance between the lithium battery packs; and therefore, by complementing advantages of the two kinds of topological structures, the problems of complex control, inaccurate balance, slow speed, low efficiency, high cost and the like existing in the lithium battery balance technology are solved.

Description

technical field [0001] The invention relates to the technical field of charging and discharging of lithium battery packs, in particular to a two-stage equalization control circuit, system and control strategy for charging and discharging of lithium battery packs. Background technique [0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, high standard voltage, and no heavy metal pollution. They are very in line with the current green requirements of sustainable human development, especially in the field of electric vehicle power battery energy storage. In order to ensure sufficient mileage of electric vehicles, electric vehicles are often equipped with a large number of battery packs, which are composed of many single cells connected in series and parallel. Avoid the imbalance of power between the monomer and the battery pack, which may cause safety hazards in the battery pack or reduce the mission life of the battery pack. Furthermore, ...

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Problems solved by technology

[0003] The importance of equalization for power battery packs will not be repeated. In the current equalization scheme of electric vehicle BMS (battery management system), the equalization control technology is divided into passive equalization and active equalization. The passive equalization method has a simple structure and is easy to control, but the resistance Energy consumption discharges, wastes energy, generates heat, and balances with energy dissipation, which does not meet the requirements of green energy development; the number of active equalization technology switches is large, and the control is complicated and difficult to implement

For DC-DC converters, it has the advantages of high equalization efficiency and easy modularization. It is a commonly used power supply design circuit. However, when the number of series monomers is large, the equalization time is long; multi-winding transformers have fast equalization speed and low magnetic loss, but increase It is necessary to change the magnetic core when reducing the battery, which is not suitable for the balance between a large number of single batteries

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