Self-adaptive fuzzy balancing control method based on historical balancing speed

Abstract

The invention discloses a self-adaptive fuzzy balancing control method based on the historical balancing speed. The method is suitable for a Pack to Cell balancing circuit; during each time of balancing, energy is supplemented to a battery monomer with the lowest voltage through a battery pack, the time consumed for each time of balancing is determined through the fuzzy control concept and referring to the time consumed for last time of balancing and the improved voltage difference, the time consumed for balancing is greatly shortened, the number of times of balancing switching is greatly lowered, the over-balancing phenomenon is eliminated, inconsistency between the battery monomers is effectively improved, and the balancing efficiency is improved.

Description

technical field [0001] The invention relates to an adaptive fuzzy equalization control method using historical equalization speed for reference. Background technique [0002] Electric vehicles are an important part of the world's energy technology revolution and the national new energy strategy, and one of the country's seven strategic emerging industries. Compared with nickel metal hydride, lead-acid and other batteries, lithium-ion batteries have obvious advantages in size, weight, charging speed, anti-memory effect, etc., and are widely used as power sources in electric vehicles and hybrid electric vehicles. However, due to the inconsistency in the production process of single lithium batteries, after the single batteries are used in series and parallel groups, as the number of charge and discharge increases, the performance difference between the battery packs will gradually increase, resulting in battery packs When overcharging or deep discharging, the phenomenon of ov...

AI Technical Summary

Problems solved by technology

[0008] (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;

[0009] (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 the Boost boost conversion is used, the improved equalization current is limited, which cannot meet the equalization requirements of the large-capacity power battery of the electric vehicle; The voltage conversion itself also has the problem of energy waste

However, due to the non-linear characteristics of the battery and the existence of ohmic internal resistance, when the battery cell is charged, the battery cell will have an instantaneous boost, which may even be higher than the voltage of other battery cells. The voltage of the battery cell will drop instantly, and the battery voltage has a recovery process, so for the voltage-based equalization control strategy, it is difficult to judge when the battery pack reaches equilibrium

If the time of each equalization is too short, it will cause the switch to switch frequently and increase the total equalization time; if the time of each equalization is too long, it will lead to over-equalization and waste energy

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