Method for estimating state of charge of power battery of electric automobile

Abstract

The invention relates to a power battery management system of an electric automobile. In order to improve the estimating precision, the invention provides a method for estimating a charge state of a power battery of the electric automobile. The method comprises the following steps: acquiring the terminal voltage, the charging and discharging current and the battery surface temperature of the power battery; according to a corresponding relationship between the open-circuit voltage and the state of charge of the power battery, analyzing to obtain an open-circuit voltage model, and according to an input matrix, a parameter matrix and an output matrix of a dynamic voltage system of the power battery, establishing a dynamic voltage model of the dynamic voltage system; updating time and measurement of a state observer to obtain priori estimated values and posteriori estimated values of a system state as well as a covariance matrix of a system state estimating error at a time point k, and circulating the updating operation till the end of estimation to obtain the state of charge (SoC) of the power battery. By the method, the estimating precision of the SoC can be improved to be within 5%, and when a set value of the SoC of the power battery is deviated from a reference value of the SoC of the power battery, the SoC is rapidly converged to the reference value.

Description

technical field [0001] The invention relates to a power battery management system of an electric vehicle, in particular to a method for the power battery management system to estimate the state of charge of the power battery. Background technique [0002] In electric vehicles, the state-of-charge (State-of-Charge, referred to as SoC, denoted by the symbol z) of the power battery is one of the decision-making factors for the energy management of electric vehicles. The capacity and energy utilization of the power battery, avoiding overcharging and / or over-discharging of the power battery, improving the safety of the power battery, and prolonging the service life of the power battery 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 three types of methods for estimating the state of...

AI Technical Summary

Problems solved by technology

However, this estimation method uses a single mapping relationship to establish a power battery model, and the established power battery model is fixed, resulting in the estimation accuracy of the state of charge SoC of the power battery due to changes in the power battery's cycle conditions, ambient temperature, and aging state. And lower, usually between 5%-10%, the estimation accuracy is lower,

[0016] In summary, the existing methods for estimating the SoC of the power battery state of charge have low estimation accuracy.

Images