Vehicle Battery SOC Estimation Using Dynamic Method Switching
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Solution Overview
Problem
Existing SOC detection methods for batteries with long plateau regions, such as olivine batteries, face challenges in accurately estimating state of charge due to the flat OCV region, leading to increased detection errors over time.
Innovation Solution
A control apparatus that employs a dual estimation method using battery voltage and current integration, switching between a first estimation method for regions with significant OCV changes and a second method for plateau regions, and temporarily adjusts the battery state to improve estimation accuracy by moving it to regions with a slope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If current integration method is used to detect battery SOC, then the method can be applied to batteries with plateau regions, but detection error accumulates over time leading to reduced measurement precision
Solution Approach 1:
The system dynamically switches between two SOC estimation methods based on real-time battery operating conditions. When the battery operates in the plateau region, the system uses current integration method; when it exits the plateau region, it switches to voltage-based estimation method, thereby adapting to changing battery states and maintaining accuracy throughout the charging cycle
Solution Approach 2:
The system changes the estimation parameter from current integration to voltage measurement based on the battery's operating region. By detecting whether the battery is in the plateau region or outside it, the system selects the appropriate parameter (current or voltage) for SOC estimation, resolving the contradiction between adaptability and precision
2Measurement precision
If voltage-based SOC estimation is used, then measurement precision is improved in non-plateau regions, but it becomes ineffective in plateau regions where OCV remains constant
Solution Approach 1:
The system employs dynamic method selection that transitions between voltage-based estimation and current integration based on the battery's real-time operating state. This dynamic adaptation ensures that the system uses the most appropriate method for the current battery region, maintaining both precision and versatility across all operating conditions
Solution Approach 2:
The system introduces an intermediary mechanism (the switching logic that monitors battery region) that coordinates between the two estimation methods. This intermediary detects the battery's operating region and seamlessly transitions between methods, ensuring continuous accurate SOC estimation without gaps or conflicts between the voltage-based and current integration approaches
3Productivity
If the battery operates continuously in the plateau region, then operational efficiency is maintained, but SOC estimation error increases due to inability to use voltage-based method
Solution Approach 1:
The system implements periodic switching strategies where it intentionally exits the plateau region at scheduled intervals to perform voltage-based SOC estimation. This periodic action resets the accumulation error from current integration by using the more accurate voltage-based method, thereby maintaining long-term accuracy without compromising overall operational efficiency
Data Source
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AI summary
A control apparatus (30) estimates a status of charge (SOC) by a first estimation method by temporarily changing the SOC of a battery (B) so that the SOC of the battery (B) falls within a first region in the case a period, during which the estimated value of the status of charge of the battery (B) falls within a second region, exceeds a prescribed period.