A multi-variable equalization control method for power battery

Abstract

The invention discloses a multi-variable equalization control method for a power battery, which includes establishing an equalizing circuit topology, collecting the voltage and current of a battery pack in a BMS; estimating the SOC value of the battery by using a UKF algorithm; calculating each battery cell according to the SOC value and determine the relationship between it and the equalization start threshold; if the difference is greater than the equalization start threshold, calculate the average state and difference of SOC and voltage and perform fuzzy control respectively to obtain the SOC average value and the equalization current value; The SOC mean value and the equalization current value are subjected to adaptive fuzzy control to obtain a PWM duty cycle; if the duty cycle is less than the equalization start threshold, the equalization control ends. Segmented hybrid control is carried out according to the working state of the battery, which effectively improves the difference of the battery pack, greatly improves the energy utilization rate of the battery pack, avoids the overcharge and overdischarge of the battery pack, and protects the safety of the battery.

Description

technical field [0001] The invention relates to the technical field of balance management systems, in particular to a multi-variable balance control method for power batteries. Background technique [0002] In recent years, under the two-way guidance of national policies and market mechanisms, the development momentum of my country's new energy vehicle industry has continued to improve. According to the statistics of the China Automobile Association, by the end of 2019, the number of new energy vehicles in my country reached 3.81 million, and the power battery loading capacity exceeded 174GWh. value. Batteries go through multiple processes during production, and the production environment and manufacturing process of each process are inevitably different, which leads to subtle inconsistencies in key parameters such as open circuit voltage, internal resistance, and capacity of each factory battery. In order to meet the user's requirements for energy storage capacity and powe...

AI Technical Summary

Problems solved by technology

The battery SOC is estimated by the open circuit voltage method, and improved on the basis of the traditional Buck-Boost circuit. By controlling the bidirectional flow of energy between the battery pack and the battery cells, the battery cells beyond the set SOC threshold are balanced. The experiment The results verified the effectiveness of the equalization strategy, but the estimation error of the open circuit voltage method is relatively large, and it is not suitable for online estimation, which has great limitations

The remaining capacity of the battery is used as the judgment standard of the balanced state to ensure that all single cells can be fully charged or discharged at the same time, without the need for the equalization circuit to work all the time, thereby reducing circuit loss and finally achieving battery balance in the battery pack. However, the capacity test error is large and the complexity is high, resulting in the equalization speed is too low, it is difficult to meet the rapidly changing working conditions

A modular active equalization of battery packs based on flyback transformers is proposed, which can realize power balance for any monomer in the module and any module in the battery pack at the same time, so the equalization speed is fast, but the equalization efficiency is low, and the control The method is also more complicated, and the equalization system cost is higher

[0004] Existing equalization technologies mostly use the voltage, SOC or capacity of the single battery as the equalization target in terms of equalization variables, but the acquisition of relevant parameters of the battery will cause errors due to the accuracy of sensors and estimation algorithms, so no matter which variable is selected, there will be flaw

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