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

Abstract

The invention relates to a power cell management system of an electric vehicle, particularly relates to a method for estimating a charge state of a power cell of the electric vehicle and aims to improve charge state estimation precision and charge state estimation stability of the power cell in the cell management system of the electric vehicle. The method comprises steps that an end voltage and charging and discharging currents of the power cell are acquired; a system model of the power cell is established; an ampere-hour integral method and state observers CDKF, AEKF and H infinity are employed to cooperate with the system model to respectively estimate charge states of the power cell to acquire zk, Ah, zk, CDKF, zk, AEKF and zk, Hinf, weight calculation of the zk, Ah, zk, CDKF, zk, AEKF and zk, Hinf is carried out to acquire final estimation values zk, zk=w1zk, Ah+w2zk, CDKF+w3zk, AEKF+w4zk and Hinf, and weight coefficients w1+w2+w3+w4=1. According to the method, multiple methods are employed for estimation, the final estimation value is acquired through weight calculation, accuracy can approach 2%, most of accuracy can approach 1%, and properties of non-easy divergence and high stability are realized.

Description

technical field [0001] The invention relates to a power battery management system of an electric vehicle, in particular to a method for estimating the state of charge of a power battery by the power battery management system. Background technique [0002] In an electric vehicle, the state of charge (SOC, denoted by the symbol z) of its power battery is one of the decision-making factors for managing the energy of the electric vehicle. Capacity and energy utilization, avoiding overcharging and / or over-discharging of power batteries, improving the safety of power batteries, and prolonging the service life of power batteries all play an important role. However, SOC is an implicit state quantity of the power battery, which is difficult to obtain directly through testing or calculation, and can only be estimated through estimation methods. [0003] At present, there are two commonly used methods for estimating the SOC of a power battery as follows: [0004] First, the method of...

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Problems solved by technology

In this way, although it can effectively resist the current, the measurement noise of the current sensor and the random interference of the environment, and correct the inaccurate initial value of the state of charge SOC of the power battery, however, due to the characteristics of various filters themselves, in the process of use It is easy to cause the estimation divergence of the filter due to the inappropriate setting of the initial value or the generation of random interference, which seriously reduces the estimation accuracy and stability of the state of charge SOC of the power battery.

[0008] In summary, the existing methods for estimating the SOC of the power battery have low estimation accuracy and are unstable.

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