Charge state evaluation method and system of power lithium ion battery

Abstract

The invention is a charge state evaluation method and system of a power lithium ion battery. According to the method, step one is to establish a circuit model of an equivalent battery. Charging and discharging and standing experiments are performed on the battery, and timing sampling is performed so that a voltage time curve is obtained. Model parameters are identified via a formula so that a non-linear relation between an open-circuit voltage OCV and an SoC is obtained. Step two is to obtain an optical estimation value of the SoC by matrixes of state prediction, prediction error variance, filtering gain, state estimation, estimation error variance, etc., according to Kalman algorithm. According to the system, an analog / digital converter, a program storage device, a programmable storage device, a timer and a displayer are respectively connected with a microprocessor. A current sensor and a voltage sensor are respectively connected in a circuit formed by connecting the battery to be tested and a load, and outputs of the current sensor and the voltage sensor are accessed into the analog / digital converter. The programmable storage device stores battery model parameters obtained by the experiments. The program storage device stores estimation program of the method. Estimation precision of the SoC can reach 1%, and the charge state evaluation method and system is more stable; besides, the system provides estimation values of the SoC in real time.

Description

technical field [0001] The invention relates to the technical field of state of charge estimation of automotive power lithium batteries, in particular to a method and system for estimating the state of charge (SoC) of power lithium ion batteries using multi-state decomposition Kalman filtering. Background technique [0002] Power batteries are the key to the development of new energy vehicles. In the field of electric vehicles, lithium-ion batteries are mostly used as power sources. Lithium-ion batteries have the advantages of high energy, long cycle life, no memory effect, safety and pollution-free, fast charging and discharging, and wide operating temperature range. [0003] The state of charge (SoC) of the battery is an important parameter in the power battery management system BMS (Battery Management System), and it is an important parameter to ensure the safe life of the battery. However, SoC estimation is a difficult problem to solve. Due to the uncertainty of battery...

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Problems solved by technology

However, as the actual working conditions fluctuate violently, the change of the statistical characteristics of the noise will cause the estimation error to increase, and even the filtering estimation process will diverge.

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