Dual-target direct equalization circuit and equalization method of battery pack

Abstract

The invention discloses a dual-target direct equalization circuit of a battery pack. A series battery pack comprises at least three single batteries and is divided into an upper part and a lower part,each single battery is connected with an equalization sub-circuit, the equalization sub-circuit comprises two metal-oxide-semiconductor field-effect transistors (MOSFETs) and an energy storage inductor, the series battery pack and the equalization sub-circuit bridge between VCC and GND, each equalization circuit is also connected with a control circuit to achieve direct equalization on an equalization target, the control circuit is used for equalizing end voltages and SOC of the single batteries in a stage way within an equalization period by simultaneously taking the end voltages and the SOCof the single batteries as equalization indexes, and dual-target equalization on the end voltages and the SOC of the single batteries is achieved by controlling on/off of the two MOSFETs of the equalization sub-circuit and by an energy storage effect of the energy storage inductor. The equalization circuit and an equalization strategy are applicable to an equalization management system of an energy storage device in a hybrid electric vehicle, a blade electric vehicle and an energy storage power station.

Description

technical field [0001] The invention relates to a dual-objective direct equalization technology and equalization method of a series battery group, which is suitable for a battery management system of a hybrid electric vehicle, a pure electric vehicle or an energy storage device in an energy storage power station. Background technique [0002] Due to the limited capacity of single cells and the low voltage of single cells, power battery packs are generally composed of multiple single cells connected in series and parallel to meet the requirements of use. Due to the inevitable inconsistency between single cells of the same type, it will seriously affect the service life of the battery pack and easily lead to overcharging and overdischarging. After multiple charge-discharge cycles in series battery packs, the distribution of the remaining capacity of each single battery will generally appear in three situations: the remaining capacity of individual single batteries is high; the...

AI Technical Summary

Problems solved by technology

For the research on the control strategy of the equalization circuit, Kobzev, Tae-hoon Kim, etc. all use the battery terminal voltage as the equalization index to balance the battery pack. However, the performance of the battery cannot be measured only by the voltage. When charging or after charging, the terminal voltage of the battery may be higher than that of other batteries. If this equalization method is adopted, the result of equalization is that the battery with low capacity will supplement the energy of the battery with high capacity, which will increase the power of each battery in the battery pack. capacity gap

Danielson, Huang W and others believe that the advantage of using SOC as the balance variable is that when the current changes suddenly under different working conditions, it will not cause the battery state of charge to fluctuate, making the change of the balance target relatively stable, which is conducive to reducing the impact of balance shocks on the battery, but This equalization method can only solve the problem of performance degradation of the battery with a larger capacity in the battery pack due to long-term insufficient charging, and cannot reduce or eliminate the gap in the actual capacity of each battery.

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