Electric vehicle SOC estimation algorithm

Abstract

The invention discloses an electric vehicle SOC estimation algorithm which comprises the steps of: establishing a second-order circuit model of a battery; according to a charge and discharge experiment, carrying out model parameter identification; carrying out first-order Taylor extension on the second-order circuit model by using extended Kalman filtering so as to obtain a linear model; then carrying out Kalman filtering on the obtained linear model so as to estimate a system state; and correcting an EKF state SOC by a SOC measured by an ampere-hour method so as to obtain an optimized SOC. Bythe electric vehicle SOC estimation algorithm disclosed by the invention, not only can the SOC be rapidly converged within an error range and problems of inaccurate initial value and accumulated error of the ampere-hour method can be solved, but also the large data processing operation of an EKF algorithm can be avoided, a load for a processor is reduced, and estimation accuracy of the SOC is greatly improved.

Description

technical field [0001] The invention relates to the field of electric vehicle batteries, in particular to the field of SOC estimation algorithms for electric vehicles. Background technique [0002] The SOC of the battery is affected by many factors and will continue to change as the usage conditions change. Continuously improving the estimation accuracy of the battery SOC is an important task in the research of the battery management system. The accurate estimation of SOC is the premise to ensure the normal charge and discharge of the battery within the working range, and it also helps the driver to drive safely, prolong the service life of the battery and optimize the control strategy of the electric vehicle. [0003] In the application of pure electric vehicles, SOC is an important parameter used to describe the remaining capacity of the battery. The accurate estimation of SOC is one of the core functions of the battery management system. The estimation of SOC is very chal...

AI Technical Summary

Problems solved by technology

[0010] 2. The ampere-hour integral is dependent on the initial SOC of the battery

If the initial value has some error, then the current estimate will be affected by the same

Due to the sampling frequency of the device, the measurement accuracy of the current sensor, and the interference of the signal, there will be a certain error between the current used for integration and the real value.

As time changes, the estimation error of the state of charge will become larger and larger. In order to eliminate the cumulative error, the SOC value must be corrected frequently, thus reducing the practicability of this method

[0011] 3. There is a functional relationship between the internal resistance of the battery and the battery, but the internal resistance of the battery is very unstable. These uncertain factors make the relationship between the internal resistance of the battery and the SOC very complicated, making it difficult to determine the corresponding relationship

In addition, the internal resistance of the battery is too small to be measured accurately, and the internal resistance method is not commonly used in electric vehicles.

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