Battery Equivalent Circuit Parameter Updating for Accurate SOC Estimation
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Solution Overview
Problem
Existing battery management systems fail to accurately estimate State of Charge (SOC) due to inaccuracies in current sensors and external noise, and the parameters of equivalent circuit models do not adapt to changes in battery electrochemical properties caused by manufacturing deviations or repeated charging/discharging.
Innovation Solution
A method and system for periodically updating the parameters of an equivalent circuit model using a recursive least square algorithm, based on terminal voltage and current measurements, to adaptively adjust resistance values and accurately predict terminal voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If ampere counting is used to estimate SOC, then the estimation is simple to implement, but the accuracy deteriorates over time due to current sensor precision errors and external noise
Solution Approach 1:
The patent implements a feedback mechanism where the estimated SOC is continuously corrected based on terminal voltage measurements. The open-circuit voltage (OCV) corresponding to the estimated SOC is compared with the actual terminal voltage, and the difference is used to adjust the SOC estimation, thereby maintaining accuracy over time while keeping the system relatively simple.
Solution Approach 2:
The patent introduces an equivalent circuit model as an intermediary between the current sensor and the SOC estimation. This model includes voltage sources and resistance elements that help filter out sensor errors and noise, providing a more accurate SOC estimation without requiring direct reliance on the current sensor alone.
2Ease of manufacture
If fixed parameter values from parameter map are used, then the equivalent circuit model is simple to update, but the parameters fail to reflect changes in battery electrochemical properties due to manufacturing deviations or repeated charging/discharging
Solution Approach 1:
The patent transitions from static fixed parameter values to dynamic parameters that are periodically updated based on terminal voltage and current measurements. The equivalent circuit model parameters (such as resistance values) are adjusted over time to reflect actual battery conditions, enabling the system to adapt to battery degradation while maintaining a relatively simple update mechanism through periodic measurements.
3Measurement precision
If periodic parameter updates using measured data are implemented, then the equivalent circuit model accurately reflects battery degradation, but the computational complexity increases
Solution Approach 1:
The patent applies partial updates to the equivalent circuit model parameters rather than complete re-estimation. Only the necessary parameters (such as resistance values) are updated periodically based on terminal voltage and current measurements, while other parameters remain unchanged. This reduces computational complexity while maintaining sufficient accuracy for battery state prediction.
Data Source
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AI summary
Provided is a method and a battery management system for estimating the parameters of an equivalent circuit model. The equivalent circuit model includes a first resistor, a second resistor connected in series to the first resistor and a capacitor connected in parallel to the second resistor. The method according to an embodiment of the present disclosure individually estimates the resistance of the first resistor and the resistance of the second resistor based on a first number of terminal voltages and a first number of currents measured in a sequential order at each time step in a sliding time window having a predefined size, and stores data indicating the estimated results in the memory.