A method for estimating the state of charge of a traction battery pack of an electric vehicle

Abstract

The invention relates to the electric automobile vehicle cell management system design field, particularly relates to a method for estimating a charge state of a power cell set of an electric vehicle and aims to improve charge state estimation precision and estimation result reliability of the power cell set. According to the method, an end voltage and charging and discharging currents of the power cell set are acquired; a Thevenin model, a dual polarization model and a three-order RC network model of the power cell set are established, the models respectively cooperate with state observers to estimate the charge state of the power cell set to acquire z<^>1,k, z<^>2,k and z<^>3,k, weight calculation of the z<^>1,k, the z<^>2,k and the z<^>3,k is carried out to acquire an estimation value zfusion,k of the charge state of the power cell set, and zfusion,k=w1(k)z<^>1,k+w2(k) z<^>2,k+w3(k) z<^>3,k, at the k moment, weight coefficients satisfy that w1(k)+ w2(k)+w3(k)=1. Through the method for estimating the charge state of the power cell set of the electric vehicle, relatively high precision and estimation result stability and estimation result reliability are realized.

Description

technical field [0001] The invention relates to the design field of a vehicle battery management system of an electric vehicle, in particular to a method for estimating the state of charge of a power battery pack of an electric vehicle. Background technique [0002] The increasingly serious energy crisis and environmental pollution problems have prompted the automobile industry to change from traditional vehicles using internal combustion engines as power sources to new energy vehicles. As the main force of new energy vehicles, electric vehicles have become the focus of research and development in the automotive field, and the power battery pack of electric vehicles, as the energy source of electric vehicles, is currently the main technical bottleneck hindering the development of electric vehicles. [0003] The state of charge (SOC for short, represented by the symbol z) of the power battery indicates the ratio of the remaining power in the power battery to its rated capacit...

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Problems solved by technology

This method uses a closed-loop feedback mechanism to compare the estimated value of the terminal voltage with the measured value, that is, the sampled value, and feeds back the difference between the two to the state observer, so that the system state of the power battery can be adaptively adjusted to its accurate value. convergence, but this method has high requirements for the accuracy of the equivalent circuit model of the power battery and the computing power of the battery management system (BMS) of the electric vehicle, and the reliability of the estimation results increases with the power battery. The accuracy of the equivalent circuit model and the algorithm of the BMS vary greatly

[0014] In summary, the existing methods for estimating the SOC of the power battery either have low estimation accuracy or unstable estimation results.

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