Battery Hysteresis Modeling for More Accurate SOC Estimation
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Solution Overview
Problem
Battery management systems in electric and hybrid vehicles face challenges in accurately estimating the state of charge (SOC) and hysteresis voltage due to variations in charging and discharging states, which affects the overall performance and longevity of battery systems.
Innovation Solution
A system and method that calculates hysteresis state components based on measured current and transit rates, incorporating relaxation factors and weighting factors to determine the overall hysteresis state and voltage, which is then used to accurately estimate the SOC of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single hysteresis transit rate is used to calculate hysteresis voltage, then the calculation is simple, but the accuracy of battery state estimation deteriorates due to variations in charging and discharging states
Solution Approach 1:
The patent segments the hysteresis voltage calculation into multiple discrete transit rate components (e.g., first transit rate, second transit rate, third transit rate) corresponding to different charging and discharging states. Each transit rate component is calculated based on specific current conditions, allowing the system to capture the complex nonlinear hysteresis behavior more accurately while maintaining a structured calculation framework.
Solution Approach 2:
The patent implements dynamic selection of hysteresis transit rates based on real-time current conditions. The system dynamically switches between different transit rate components depending on whether the battery is charging or discharging, and adjusts the contribution of each component based on the current rate, making the hysteresis model adaptive to varying operating conditions rather than using a fixed single rate.
2Measurement precision
If multiple hysteresis transit rates are incorporated to improve accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent applies partial action by selectively activating only the necessary hysteresis transit rate components based on current operating conditions. Instead of always calculating all possible transit rate components, the system activates only those relevant to the current charging or discharging state, reducing unnecessary computational complexity while maintaining accuracy when needed.
Solution Approach 2:
The patent changes the parameters of the hysteresis model dynamically by adjusting which transit rate components are active and their respective weights based on current conditions. The system modifies the hysteresis voltage calculation parameters (transit rates, relaxation factors) according to the battery's state, allowing accurate modeling across different operating regimes without requiring a permanently complex structure.
3Measurement precision
If relaxation factors are applied to account for voltage relaxation after charging or discharging, then measurement precision improves, but calculation complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing relaxation factor values for different current conditions and time periods. Instead of performing complex real-time calculations during operation, the system uses pre-determined relaxation factors that are selected based on current conditions, reducing real-time computational complexity while maintaining accuracy in accounting for voltage relaxation effects.
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
This approach enhances the accuracy of battery state estimation, improving the management and operation of battery systems by accounting for multiple hysteresis transit rates and relaxation, leading to better performance and longevity.
Implementation Method 1
A system and method that calculates hysteresis state components based on measured current and transit rates, incorporating relaxation factors and weighting factors to determine the overall hysteresis state and voltage
Implementation Method 2
incorporating relaxation factors and weighting factors to determine the overall hysteresis state and voltage, which is then used to accurately estimate the SOC of the battery
Data Source
AI summary
A system for an electric vehicle includes a hysteresis module configured to calculate a plurality of hysteresis state components of a battery based on a measured current and a respective hysteresis transit rate, calculate an overall hysteresis state of the battery based on the plurality of hysteresis state components, and calculate a hysteresis voltage of the battery based on the overall hysteresis state, and a state of charge (SOC) module configured to calculate an SOC of the battery based in part on the hysteresis voltage.