Lithium-iron-phosphate-battery fractional-order equivalent circuit model establishing method based on frequency demultiplication representation

Abstract

The invention provides a lithium-iron-phosphate-battery fractional-order equivalent circuit model establishing method based on frequency demultiplication representation. In view of the irregular performance and the asymmetry performance of a lithium battery material, the circuit characteristics of a lithium battery are represented with a fractional-order differential method defined based on Caputo; due to the memory characteristic of fractional-order differential, an equivalent circuit model obtains the higher freedom degree and the higher stability; when the fractional-order circuit model is solved, the impedance frequency difference between activation polarization and concentration polarization is considered, the medium frequency band and the low frequency band are respectively subjected to discrete approximating through an Oustaloup approximation approaching filter, and therefore the model obtains the higher approximation accuracy and dynamic performance. Finally, the parameters of the frequency-demultiplication fractional-order equivalent circuit model are identified through a pulse charging-discharging experiment, the stability, the dynamic performance and the accuracy of the lithium-battery equivalent circuit model are improved, and practical engineering significance is achieved.

Description

technical field [0001] The invention relates to the equivalent technology of lithium iron phosphate battery circuit. Background technique [0002] The lithium battery equivalent circuit model is used to objectively describe the energy state, internal characteristics and response characteristics of the power battery through the knowledge of circuit theory. An accurate battery equivalent circuit model is the basis and guarantee for the estimation accuracy of the state of charge and state of health of the pure electric vehicle battery. Due to a series of complex nonlinear dynamic reactions such as lithium ion diffusion, electrolyte migration, battery heat generation and conduction inside the lithium battery, there are still many challenges in establishing an accurate and easy-to-engineer lithium battery equivalent circuit model. [0003] Among the equivalent circuit models studied so far, the second-order RC model is most widely used. The order of the second-order RC model is...

AI Technical Summary

Problems solved by technology

However, each component of the equivalent circuit model is fitted to the state of charge of the lithium battery. This method ignores the connection between the model components, which limits the characterization accuracy of the lithium battery model.

At the same time, the existing equivalent circuit model does not take into account the different frequency impedance characteristics of activation polarization and concentration polarization when performing parameter identification, resulting in a large fitting error in the polarization characteristics of lithium batteries.

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