Lithium battery pack SOC (state of charge) equalization system and lithium battery pack SOC equalization method

Abstract

The invention discloses a lithium battery pack SOC (state of charge) equalization system and a lithium battery pack SOC equalization method. The equalization problems of lithium battery packs are divided into two levels, including intra-group equalization and intergroup equalization. Lithium batteries are divided into a plurality of groups, every lithium battery group is in parallel connection with a bidirectional DC-DC converter, the output ends of the bidirectional DC-DC converters are in series connection to serve as the output ends of a direct-current bus and a power generation system, and loads are in parallel connection. The batteries in every group are connected through bilateral switches and are in parallel connection with by-pass switches so as to be connected dynamically. Intergroup equalization is achieved by distributing output voltage of every group according to average SOC thereof; intra-group equalization can be achieved by controlling dynamic connection of every single battery in every group. The lithium battery pack SOC equalization system and the lithium battery pack SOC equalization method have the advantages that lithium battery pack SOC is equalized without an extra equalization circuit, so that energy transfer among the batteries is avoided, lithium battery pack equalization is achieved automatically in a charge-discharge process, the equalization speed is greatly increased and the equalization efficiency is greatly improved.

Description

technical field [0001] The invention belongs to the technical field of battery energy storage, and in particular relates to a lithium battery pack SOC (State Of Charge) equalization system and method. [0002] technical background [0003] Considering the unsustainability of fossil energy and the continuous increase of environmental pressure, human beings urgently need a clean and sustainable alternative energy source. Against this background, wind energy, nuclear energy, and solar energy have attracted widespread attention. In practical applications, the energy generated by clean energy often requires energy storage devices to store it to meet various application scenarios. As an energy storage device with high energy density, light weight, relatively long service life, low self-discharge rate, no memory effect, and high and low temperature adaptability, lithium battery has good development prospects and research value. It is used in some mobile devices Such as electric veh...

AI Technical Summary

Problems solved by technology

Due to the limitations of the manufacturing process and the use process, there are often inconsistencies between the single cells connected in series (specifically, the capacity and internal resistance are inconsistent), which leads to the inconsistency of the discharge current rate and temperature of each cell during the use of the battery pack, and vice versa. As a positive feedback, the inconsistency of SOC (State Of Charge) and internal resistance between monomers is exacerbated

This difference will damage individual cells due to overcharge or overdischarge, affect the overall performance and service life of the battery pack, and even cause an explosion in severe cases

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