Traction Battery SOC Estimator Gain Calibration at Charge Extremes
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Solution Overview
Problem
Existing systems for monitoring the operating characteristics of traction batteries in electrified vehicles face challenges in accurately estimating power capability and state-of-charge, especially at low and high SOC levels, leading to potential over-discharge or over-charge issues.
Innovation Solution
A controller dynamically adjusts the estimation gain based on the state-of-charge (SOC) and temperature of the traction battery, using an equivalent circuit model to estimate operating characteristics. The estimation gain is reduced at low and high SOC levels, and also when the temperature is colder than a threshold, to prevent overshooting and ensure accurate power capability and SOC estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed estimation gain is used in the equivalent circuit model, then the system is simple to operate, but the estimation accuracy deteriorates at low and high SOC levels
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed estimation gain to a dynamic estimation gain that changes based on SOC levels. The controller automatically adjusts the estimation gain according to the current SOC state, making the system adaptive to different operating conditions. This resolves the contradiction by enabling high estimation accuracy across the full SOC range while maintaining operational simplicity through automated adjustment.
Solution Approach 2:
The patent implements parameter changes by modifying the estimation gain parameter based on SOC thresholds. When SOC falls below a lower threshold or rises above an upper threshold, the estimation gain is adjusted to appropriate values. This parameter adaptation allows the system to maintain high measurement precision across different SOC conditions without requiring complex manual intervention.
2Measurement precision
If the estimation gain is reduced at low and high SOC levels, then the SOC estimation accuracy improves, but the response speed deteriorates
Solution Approach 1:
The patent uses dynamics to create a responsive estimation gain adjustment mechanism that adapts to different SOC conditions. By dynamically switching the estimation gain based on real-time SOC measurements, the system achieves both accurate estimation (through reduced gain at extreme SOC levels) and fast response (through automated real-time adjustment). This resolves the speed-accuracy tradeoff by making the system adaptively fast and accurate where needed.
Solution Approach 2:
The patent implements feedback by continuously monitoring SOC levels and using this information to adjust the estimation gain. The controller receives feedback about the current SOC state and automatically modifies the estimation parameters accordingly. This closed-loop feedback mechanism ensures that the system maintains both accuracy and responsiveness by adapting to changing conditions in real-time.
3Measurement precision
If the estimation gain is dynamically adjusted based on temperature, then the estimation accuracy improves in cold conditions, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by adjusting the estimation gain based on temperature conditions. When the battery temperature falls below a threshold, the controller modifies the estimation gain to account for cold-temperature effects on battery performance. This parameter adaptation improves measurement precision in cold conditions while maintaining system simplicity through automated temperature-based adjustment.
Solution Approach 2:
The patent implements universality by creating a multi-functional estimation gain adjustment mechanism that responds to both SOC levels and temperature conditions. The same estimation framework handles both SOC-based and temperature-based adjustments, making the system versatile and adaptable to different operating conditions without requiring separate complex systems for each function.
Data Source
AI summary
A traction battery controller of an electrified vehicle dynamically adjusts an estimation gain based on a state-of-charge (SOC) of the traction battery and controls the vehicle according to an operating characteristic of the traction battery estimated from an equivalent circuit model of the traction battery that depends on the estimation gain. The controller may reduce the estimation gain while the SOC is low or high and may otherwise maintain the SOC. The controller may dynamically adjust the estimation gain based further on a temperature of the traction battery. The operating characteristic may be a power capability of the traction battery or an updated SOC of the traction battery.