Battery Equivalent Circuit Modeling for Frequent Charge-Discharge Cycles
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Solution Overview
Problem
Existing secondary battery models fail to accurately simulate charge-discharge behavior in actual vehicle conditions due to frequent charge and discharge cycles, leading to insufficient accuracy in charge-discharge control.
Innovation Solution
A development support apparatus and method using an equivalent circuit model that reflects the state of charge (SOC)-operating voltage characteristic in a high change-amount region, incorporating a DC resistance component and RC parallel circuits to simulate polarization characteristics, allowing for accurate estimation of energy storage device behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an equivalent circuit model based on SBA-IS test data is used, then the model structure is simple and parameters are easily set, but the accuracy of charge-discharge control in actual vehicles is insufficient
Solution Approach 1:
The patent divides the SOC range into multiple regions (high SOC region, middle SOC region, low SOC region) and assigns different RC parallel circuits to each region based on their specific polarization characteristics. This local differentiation allows the model to accurately capture region-specific behavior without uniformly increasing complexity across the entire SOC range.
Solution Approach 2:
The equivalent circuit model is segmented into multiple RC parallel circuits, each corresponding to a specific SOC region. The high SOC region uses one RC circuit, the middle SOC region uses another, and the low SOC region uses a third. This segmentation allows the model to adapt to different polarization characteristics in different regions while maintaining overall model manageability.
2Adaptability or versatility
If a model ignoring frequent charge-discharge cycles is used, then the model is simpler, but it cannot accurately reflect actual vehicle usage patterns
Solution Approach 1:
The patent implements dynamic switching between different RC parallel circuits based on the current SOC region. As the battery transitions between charge-discharge cycles and SOC levels, the model automatically activates the appropriate RC circuit for the current region, enabling the model to adapt to frequent charge-discharge patterns in actual vehicle usage while maintaining accuracy.
3Measurement precision
If region-specific RC parallel circuits are introduced for different SOC ranges, then the accuracy in high SOC regions is improved, but the model complexity increases
Solution Approach 1:
The patent applies local quality by introducing RC parallel circuits with specific time constants tailored to each SOC region's polarization characteristics. The high SOC region receives a dedicated RC circuit with time constant optimized for that region's behavior, improving local accuracy without requiring complete model redesign.
Solution Approach 2:
The patent implements partial action by selectively applying different RC parallel circuits only to specific SOC regions where they are most needed. Rather than using a single complex circuit for the entire SOC range, the model applies simplified circuits in regions where polarization effects are less critical and more complex circuits only where necessary, balancing accuracy and complexity.
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 model accurately estimates energy storage device behavior, particularly in frequent charge-discharge cycles, reproducing current and voltage behavior corresponding to polarization changes, improving estimation accuracy and reproducing actual vehicle conditions.
Implementation Method 1
utilizing an equivalent circuit model that reflects SOC-operating voltage characteristics in high change-amount regions, incorporating RC parallel circuits to simulate polarization characteristics
Data Source
AI summary
A development support apparatus includes: an estimation unit that estimates behavior of an energy storage device by using an equivalent circuit model reflecting a state of charge (SOC)-operating voltage characteristic in a high change-amount region where an amount of change in an operating voltage with respect to an amount of change in the SOC is relatively higher than in other regions among SOC-operating voltage characteristics during constant current charge and discharge of the energy storage device; and an output unit that outputs a result of an estimation by the estimation unit.