Battery SOC Estimation With OCV-Based FCC Correction
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Solution Overview
Problem
The current integration method for estimating the state of charge (SOC) of storage batteries is affected by measurement errors and storage battery state errors, leading to inaccurate SOC estimation when using full charge capacity (FCC) with low accuracy.
Innovation Solution
A storage battery management device that includes a current measurement unit, a coulomb counting processing unit, an SOC estimation unit, an OCV acquisition unit, and a correction unit. The device corrects the FCC based on a correction SOC within the second region of the SOC-OCV characteristics, improving the accuracy of SOC estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the current integration method is used to estimate SOC, then the SOC can be estimated without being affected by the limitation of the period during which the OCV is available or by the plateau region, but the SOC may not be accurately estimated due to measurement errors in the current measurement unit and storage battery state error
Solution Approach 1:
The patent combines the current integration method and the OCV method into a hybrid SOC estimation system. The current integration unit continuously estimates SOC using current measurements, while the OCV acquisition unit periodically corrects this estimation using open-circuit voltage measurements. This merging allows the system to maintain continuous SOC monitoring without OCV limitations while periodically eliminating integration errors and storage battery state errors through OCV-based corrections.
Solution Approach 2:
The patent implements a feedback mechanism where the OCV acquisition unit periodically measures the actual OCV and compares it with the SOC estimated by the current integration unit. When the correction condition is satisfied (OCV is available and within valid range), the system uses this feedback to correct the FCC value, thereby compensating for measurement errors and storage battery state errors that have accumulated during continuous operation.
2Measurement precision
If the FCC with low accuracy is used in the current integration method, then the SOC estimation continuously contains errors caused by the storage battery state error in addition to measurement errors, but correcting the FCC requires additional complexity
Solution Approach 1:
The patent performs preliminary correction of the FCC value by using OCV measurements taken during periods when the battery is in a stable state (charging or discharging). By proactively correcting the FCC before significant errors accumulate, the system maintains high SOC estimation accuracy without requiring continuous complex correction mechanisms. The correction unit stores the corrected FCC for future use, eliminating the need for real-time complex calculations.
Solution Approach 2:
The patent changes the parameter being corrected from direct SOC correction to FCC (full charge capacity) correction. Instead of continuously adjusting the SOC estimate, the system periodically updates the FCC parameter used in the current integration method. This parameter change simplifies the correction process because FCC is a single value that can be updated periodically rather than requiring continuous adjustment of the SOC calculation itself.
3Measurement precision
If the OCV method is used to estimate SOC, then the period for estimating the SOC can be limited to the period when the OCV of the storage battery is available, but the SOC of the storage battery may not be estimated accurately for storage batteries with SOC-OCV characteristics that include a region where the absolute value of a change amount of the OCV relative to the change amount of the SOC is relatively small
Solution Approach 1:
The patent merges the strengths of both methods by using current integration for continuous SOC estimation (providing availability) and OCV method for periodic correction (providing accuracy in plateau regions). The current integration unit ensures SOC can be estimated at all times regardless of OCV availability, while the OCV acquisition unit provides periodic corrections that are particularly valuable in plateau regions where current integration errors accumulate.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution accurately corrects the FCC and enhances the accuracy of SOC estimation in the current integration method by reflecting the actual state of the storage battery, reducing errors caused by measurement and state differences.
Implementation Method 1
a coulomb counting processing unit that calculates the capacity of the storage battery by integrating the current measured by the current measurement unit
Implementation Method 2
The OCV (open circuit voltage) method is known as a method for estimating the SOC (state of charge or charge rate) of storage batteries... The OCV method acquires the OCV of a storage battery to estimate the SOC based on the correspondence between the acquired OCV and the SOC-OCV (open circuit voltage) characteristic curve
Data Source
AI summary
A storage battery management device manages a storage battery having SOC-OCV characteristics including a first region in which an OCV change rate is a predetermined value or less and a second region in which the OCV change rate exceeds the predetermined value. The device includes a coulomb counting processing unit that calculates capacity of the storage battery an SOC estimation unit that estimates the SOC of the storage battery, an OCV acquisition unit that acquires the OCV of the storage battery, and a correction unit that corrects the FCC of the storage battery used in the SOC estimation unit based on the correction SOC when a correction condition is satisfied that includes as a necessary condition that the correction SOC is within the second region.