Battery Pack SOC Estimation Using Adaptive Model Correction
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Solution Overview
Problem
Current battery state of charge (SOC) estimation methods, such as ampere counting and equivalent circuit models, face challenges in accurately determining SOC due to measurement errors and nonlinear battery behavior, making it difficult to adjust reliability based on operational states and environments.
Innovation Solution
A battery management apparatus and method that determines multiple candidate SOC values in each cycle, using a sensing unit to detect current, voltage, and temperature, and a control unit to adjust the equivalent circuit model's time constants and correction values based on these measurements, thereby improving the accuracy of SOC estimation and reliability of ampere counting and equivalent circuit models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ampere counting is used to estimate SOC, then the SOC can be calculated based on cumulative current, but measurement errors and external noise cause discrepancy between estimated and actual SOC
Solution Approach 1:
The patent introduces an equivalent circuit model as an intermediary to bridge the gap between ampere counting and actual SOC. The equivalent circuit model simulates battery electrochemical properties and provides a reference for correcting ampere counting errors, thereby improving SOC estimation accuracy while maintaining the simplicity of cumulative current calculation
Solution Approach 2:
The patent implements a feedback mechanism where the equivalent circuit model continuously monitors the battery state and provides correction signals to the ampere counting method. By comparing the voltage and temperature predictions from the equivalent circuit model with actual measurements, the system adjusts the SOC estimation to compensate for cumulative current errors and external noise interference
2Adaptability or versatility
If equivalent circuit model is used to simulate battery properties, then electrochemical behavior can be modeled, but the nonlinear feature of battery makes it difficult to perfectly simulate
Solution Approach 1:
The patent applies dynamics by making the equivalent circuit model parameters adaptive rather than fixed. The model parameters are dynamically adjusted based on real-time battery operating conditions such as temperature, charge/discharge rate, and state of charge, allowing the model to accurately track the nonlinear behavior of the battery across different operational states
Solution Approach 2:
The patent changes the parameters of the equivalent circuit model based on battery operating conditions. By adjusting resistance, capacitance, and other circuit parameters according to temperature and SOC levels, the model can accurately represent the battery's nonlinear electrochemical properties under varying conditions, improving simulation reliability
3Ease of operation
If fixed values are allocated to process noise in extended Kalman filter, then the filter can be implemented, but it is difficult to adjust reliability of ampere counting and equivalent circuit model for different operational states
Solution Approach 1:
The patent makes the process noise values dynamic by linking them to battery operating conditions. The process noise for ampere counting and equivalent circuit model are adjusted based on temperature, SOC, and charge/discharge rate, allowing the extended Kalman filter to adaptively weight the reliability of each method according to current operational state, thereby improving both ease of implementation and adaptability
Data Source
AI summary
There are provided a battery management apparatus, a battery management method and a battery pack. The battery management apparatus generates a first data set including a first current value, a first voltage value and a first temperature value indicating a current, a voltage and a temperature of a battery. The battery management apparatus generates a second data set from the first data set using an error generator. The battery management apparatus determines a first candidate value, a second candidate value and a third candidate value for a state of charge (SOC) respectively from the first current value, the first data set and the second data set. The control unit updates a correction value when a second difference value between the first candidate value and the third candidate value is smaller than a first difference value between the first candidate value and the second candidate value.