Apparatus for estimating state of secondary battery including blended positive electrode material and method thereof

Patent metadata

Field	Value
Publication number	US-2016259011-A1
Application number	US-201415029048-A
Country	US
Kind code	A1
Filing date	Oct 14, 2014
Priority date	Oct 14, 2013
Publication date	Sep 8, 2016
Grant date	—

Abstract

An apparatus for estimating a state of a secondary battery by using an Extended Kalman Filter is provided, in which the secondary battery includes a positive electrode including a first positive electrode material and a second positive electrode material having different operating voltage ranges from each other, a negative electrode including a negative electrode material, and a separator interposed therebetween. The apparatus includes a sensor unit which measures voltage and current of the secondary battery at time intervals, and a control unit electrically connected with the sensor unit, and estimates the state of the secondary battery including a state of charge of at least one of the first positive electrode material, the second positive electrode material, or the negative electrode material, by implementing an Extended Kalman Filter algorithm using a state equation including, as a state parameter, the state of charge of at least one of the first positive electrode material, the second positive electrode material, or the negative electrode material, and an output equation including, as an output parameter, the voltage of the secondary battery. The state equation and the output equation are derived from a circuit model which includes a first positive electrode material circuit unit and a second positive electrode material circuit unit connected in parallel with each other, and a negative electrode material circuit unit connected in series with these two circuit units.

First claim

1 . An apparatus for estimating a state of a secondary battery comprising a blended positive electrode material, wherein the secondary battery comprises a positive electrode including a first positive electrode material and a second positive electrode material having different operating voltage ranges from each other, a negative electrode including a negative electrode material and a separator interposed therebetween, the apparatus comprising:
a sensor unit configured to measure, at time intervals, voltage and current of the secondary battery; and a control unit electrically connected with the sensor unit, and configured to estimate the state of the secondary battery, wherein the state of the secondary battery comprises a state of charge of at least one of the first positive electrode material and the second positive electrode material, by implementing an Extended Kalman Filter algorithm using a state equation and an output equation, wherein the state equation comprises, as a state parameter, the state of charge of at least one of the first positive electrode material and the second positive electrode material, and the output equation comprises, as an output parameter, the voltage of the secondary battery, wherein the state equation and the output equation are derived from a circuit model comprising a first positive electrode material circuit unit and a second positive electrode material circuit unit respectively corresponding to the first and the second positive electrode materials and being connected in parallel with each other, and optionally, a negative electrode material circuit unit corresponding to the negative electrode material and being connected in series with the first and the second positive electrode material circuit units, and each of the first positive electrode material circuit unit, the second positive electrode material circuit unit, and the negative electrode material circuit unit comprises, as an optional element, an open-circuit voltage element varying voltage according to the state of charge of a corresponding electrode material, and/or an impedance element.

2 . The apparatus of claim 1 , wherein the state parameter further includes a state of charge of the negative electrode material.

3 . The apparatus of claim 1 , wherein the state parameter includes at least one voltage selected from the group consisting of:
a voltage formed by the impedance element of the first positive electrode material circuit unit; a voltage formed by the impedance element of the second positive electrode material circuit unit; and a voltage formed by the impedance element included in the negative electrode material circuit unit.

4 . The apparatus of claim 1 , wherein the state equation includes, as an input parameter, a first current flowing through the first positive electrode material circuit unit, and a second current flowing through the second positive electrode material circuit unit, and
the control unit determines the first current and the second current, by using a current distribution equation derived from the circuit model, and the current measured by the sensor unit.

5 . The apparatus of claim 1 , wherein the output equation is derived from voltage analysis of the circuit model, and includes a plurality of input parameters, and the plurality of input parameters include:
a current measured by the sensor unit; an open-circuit voltage component of the first positive electrode material circuit unit; an open-circuit voltage component of the second positive electrode material circuit unit; optionally, an open-circuit voltage component of the negative electrode material; optionally, an impedance voltage component of the first positive electrode material circuit unit; optionally, an impedance voltage component of the second positive electrode material circuit unit; and optionally, an impedance voltage component of the negative electrode material circuit unit.

6 . The apparatus of claim 1 , wherein the state equation is defined such that the states of charge of the first positive electrode material and the second positive electrode material are determined by adding up currents flowing through the first positive electrode material circuit unit and the second positive electrode material circuit unit according to time, respectively, and
the control unit time-updates the states of charge of the first positive electrode material and the second positive electrode material by implementing [state estimate time update] of the Extended Kalman Filter algorithm, by using the state equation.

7 . The apparatus of claim 2 , wherein the state equation is defined such that the states of charge of the first positive electrode material, the second positive electrode material, and the negative electrode material are determined by adding up currents flowing through the first positive electrode material circuit unit, the second positive electrode material circuit unit, and the negative electrode material circuit unit according to time, respectively, and
the control unit time-updates the states of charge of the first positive electrode material, the second positive electrode material, and the negative electrode material, by implementing [state estimate time update] of the Extended Kalman Filter algorithm, by using the state equation.

8 . The apparatus of claim 3 , wherein the state equation is defined such that voltage formed by the impedance element varies according to time, by an impedance voltage formula derived from circuit analysis of the impedance element included in the first positive electrode material circuit unit, the second positive electrode material circuit unit, and the negative electrode material circuit unit, and
the control unit time-updates the voltage formed by each impedance element, by implementing [state estimate time update] of the Extended Kalman Filter algorithm, by using the state equation.

9 . The apparatus of claim 1 , wherein the control unit implements [error covariance time update] of the Extended Kalman Filter algorithm, by using Jacobian matrix derived from the state equation.

10 . The apparatus of claim 1 , wherein the control unit estimates voltage of the secondary battery, by implementing [output estimate] of the Extended Kalman Filter algorithm, by using the output equation.

11 . The apparatus of claim 9 , wherein the control unit implements [Kalman gain determination] of the Extended Kalman Filter algorithm, by using Jacobian matrix derived from the output equation and the time-updated error covariance.

12 . The apparatus of claim 11 , wherein the control unit implements [state estimate measurement update] of the Extended Kalman Filter algorithm, by reflecting the determined Kalman gain to a difference between the measured secondary battery voltage and the estimated secondary battery voltage.

13 . The apparatus of claim 11 , wherein the control unit implements [error covariance measurement update] of the Extended Kalman Filter algorithm, by using the time-updated error covariance and the determined Kalman gain.

14 . The apparatus of claim 1 , wherein the state equation includes a process noise, and the output equation includes a sensor noise.

15 . The apparatus of claim 1 , wherein the control unit estimates the state of charge of the secondary battery, by using a state of charge of the first positive electrode material and a state of charge of the second positive electrode material, and a capacity of the first positive electrode material and a capacity of the second positive electrode material.

16 . The apparatus of claim 1 , wherein the impedance eleme

Assignees

• Lg Chemical Ltd

Inventors

• Joe Won-Tae

Classifications

• G01R31/389

  Measuring internal impedance, internal conductance or related variables · CPC title

• G01R31/367 Primary

  Software therefor, e.g. for battery testing using modelling or look-up tables · CPC title

• G01R31/3835

  involving only voltage measurements · CPC title

• G01R31/3648 Primary

  comprising digital calculation means, e.g. for performing an algorithm · CPC title

• G01R31/3842

  combining voltage and current measurements · CPC title