Battery State Estimation with Qualitative Correction

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Solution Overview

Problem

Existing battery internal state estimation methods, such as the current integration and open circuit voltage methods, suffer from errors due to incorrect battery characteristic parameters, leading to discontinuous changes in estimated state and contradictions with the qualitative properties of batteries, which can affect host systems designed under specific assumptions.

Innovation Solution

A battery internal state estimation apparatus that includes an internal state estimation unit for calculating the state of charge and other parameters based on current and voltage measurements, and an internal state correction unit that adjusts estimates to ensure they align with the qualitative properties of batteries, such as not changing when no current flows and accurately reflecting charging and discharging states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple estimation methods (current integration and open circuit voltage) are used in combination, then the state of charge estimation accuracy is improved, but the estimated value changes discontinuously when switching between methods

Engineering Contradiction:

Improvestate of charge estimation accuracyVSAvoidcontinuity of estimated value

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent implements a feedback mechanism where the estimated state of charge from multiple methods is continuously compared and adjusted. The system uses the differences between current integration method results and open circuit voltage method results as feedback to correct estimation errors, ensuring continuous and accurate state of charge estimation without discontinuous changes when switching between methods.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent combines multiple estimation methods (current integration and open circuit voltage) into a composite estimation system. By integrating the strengths of both methods and using their combined results with error correction, the system achieves both high accuracy and continuity in state of charge estimation.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If adaptive filter is used to continuously correct results from multiple methods, then discontinuous change is prevented, but the estimation becomes contradictory to qualitative properties of the battery

Engineering Contradiction:

Improvecontinuity of estimated valueVSAvoidconsistency with battery qualitative properties

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent dynamically adjusts the correction applied to estimation results based on the charging/discharging state of the battery. During charging, the system applies corrections that ensure state of charge increases, and during discharging, it applies corrections that ensure state of charge decreases. This dynamic adjustment maintains both continuity and consistency with battery qualitative properties.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the correction parameters based on the battery's operational state (charging or discharging). By modifying the correction magnitude and direction according to the current flow direction and magnitude, the system maintains continuity while ensuring the estimated state of charge always aligns with the actual battery state.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If battery characteristic parameters are used for state of charge calculation, then the estimation can be performed, but errors in parameters cause errors in estimation

Engineering Contradiction:

Improvefeasibility of estimationVSAvoidstate of charge estimation accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent uses feedback from multiple estimation methods to identify and correct errors in battery characteristic parameters. By comparing results from current integration and open circuit voltage methods, the system detects parameter errors and applies corrections, maintaining both the feasibility of using simple parameters and the accuracy of estimation.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10180461B2Battery internal state estimation apparatus

Publication Date: 2019.01.15 MITSUBISHI ELECTRIC CORP

AI summary

A battery internal state estimation apparatus including: an internal state estimation unit, which inputs at least one of measured values obtained by a battery measurement unit at preset sampling intervals including a current flowing through a battery, an inter-terminal voltage, a temperature of the battery, and an ambient air temperature, for estimating, based on the measured values, at least one of a state of charge, internal temperature, capacity, and internal resistance of the battery as an internal state of the battery; and an internal state correction unit for correcting estimated values of the internal state obtained by the internal state estimation unit so that the estimated values are not contradictory at least to qualitative properties of the battery, and outputting the corrected values to an output unit.