Cells to cells equalization circuit and method based on switch matrix and lc resonant transformation

Abstract

The invention discloses a switch matrix and LC resonant transformation based cells to cells equalization circuit and a method. The circuit comprises a microcontroller, a matrix switch module, an equalization bus, an LC resonant transformation module and a filtering capacitor. Zero current switch equalization from any adjacent cells to any adjacent cells or any cell in a pack can be achieved, and the equalization efficiency is greatly improved; the magnitude of the equalization current is adjusted by controlling the difference of the optimal discharging and optimal charging cells, and the inconsistency between the cells is improved; the problem of low equalization efficiency of charging and discharging during equalization of traditional pack to cell equalization circuits is solved, and the problem of the limitation of improvement of the equalization current of the Cell to Cell equalization circuits is solved.

Description

technical field [0001] The invention relates to a cells-to-cells equalization circuit and method based on switch matrix and LC resonance transformation. Background technique [0002] Lithium-ion batteries are widely used as power sources in electric vehicles and hybrid electric vehicles due to their high energy density, low discharge rate and no memory effect. However, in practical applications, in order to obtain a higher voltage level, batteries are mostly used in series. However, series-connected lithium battery packs bring a more serious problem: Even small differences in the internal resistance or capacity of the battery cells in the series-connected battery pack may lead to extreme imbalances in voltage or SOC between battery cells. In addition, after several charge-discharge cycles, this imbalance will become more and more serious, which greatly reduces the usable capacity and cycle life of the battery pack. Even, safety accidents may be caused, such as explosion, f...

AI Technical Summary

Problems solved by technology

However, series-connected lithium battery packs bring a more serious problem: even small differences in the internal resistance or capacity of the battery cells in the series-connected battery pack may lead to extreme imbalances in voltage or SOC between battery cells

[0007] (1) The open circuit voltage of lithium-ion batteries is relatively flat when the SOC is between 30% and 70%. Even if the SOC differs greatly, the corresponding voltage difference is very small. The equalization current is very small, which may even cause the power electronic devices to fail to conduct normally;

[0008] (2) Due to the conduction voltage drop of power electronic devices, it is difficult to achieve zero voltage difference balance between battery cells

However, the main problem of this invention is: because it belongs to the Cell to Cell type equalization circuit, even if Boost boost conversion is used, the increased equalization current is limited, which is far from meeting the equalization requirements of large-capacity power batteries of electric vehicles; and Boost conversion itself also has energy waste

Images