Method and device for estimating state of charge based on electric vehicle

Abstract

The invention presents a method and a device for estimating the state of charge based on an electric vehicle. The method comprises the following steps: conducting an HPPC experiment on the power battery of an electric vehicle in advance, and getting a first function relation between the open circuit voltage and the state of charge and a second function relation between the DC internal resistance and the state of charge through fitting according to the experimental result; substituting measured values of open circuit voltage of the power battery in multiple cycles to the first function relation to get calculated values of state of charge in multiple cycles; substituting the calculated values of state of charge in multiple cycles to the second function relation to get calculated values of DC internal resistance in multiple cycles; and carrying out recursive estimation through use of an observation equation and a state equation of an extended Calman filter algorithm to get an estimated value of state of charge. The technical problem that the estimation accuracy of state of charge is low and cannot meet the applicability of project development in the prior art is solved.

Description

technical field [0001] The invention relates to the technical field of vehicle control, in particular to a method and device for estimating the state of charge of an electric vehicle. Background technique [0002] Accurate estimation of battery state of charge (State of Charge, SOC) is an important basis for electric vehicle battery charge and discharge control and power optimization management, which directly affects the service life of the battery and the power performance of the vehicle. The battery pack of an electric vehicle usually includes several single cells to satisfy the larger output power and longer mileage of the electric vehicle. [0003] The existing method for estimating the SOC of a battery pack usually uses a combination of a simple open-circuit voltage method and an ampere-hour integration method. The open-circuit voltage method is based on the static open-circuit voltage (Open Circuit Voltage, OCV) data to estimate the initial SOC value of the battery. ...

AI Technical Summary

Problems solved by technology

The open circuit voltage method requires the power battery to stand for a long enough time, which is obviously not easy to achieve under working conditions

The ampere-hour integration method has high requirements for current sampling accuracy. If the power battery is charged and discharged at the high end of the SOC for a long time, large accumulated errors will occur.

In addition, the use range of SOC of automotive power batteries is generally between 30-70%. If there is no low-end correction for a long time, using the ampere-hour integration method will cause large errors

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