Battery State of Charge Estimation Using Kalman Filter Correction
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Solution Overview
Problem
Conventional SOC estimation methods for batteries in electric vehicles face accuracy issues due to differences in statistical characteristics between estimated values and fluctuations caused by uncertainty in chemical reactions, leading to inaccurate estimation of the state of charge.
Innovation Solution
A battery state of charge estimation apparatus that combines a charge and discharge current detection unit, a terminal voltage detection unit, an open circuit voltage method, and a current integration method, using a Kalman filter to calculate error correction values and correct the current integration method state of charge, thereby improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the open circuit voltage method is used to estimate SOC, then monitoring at all times is not required, but the estimation accuracy of SOC variation in short time is insufficient
Solution Approach 1:
The patent merges the advantages of both methods by using the open circuit voltage method as the primary estimation approach (which does not require continuous monitoring) while incorporating the current integration method to capture short-term SOC variations. The system combines the ease of operation of the open circuit voltage method with the short-term accuracy of the current integration method.
Solution Approach 2:
The system performs preliminary calculation of SOC using the open circuit voltage method, which provides a baseline estimation without requiring continuous monitoring. Then, it uses current integration to capture short-term variations from this baseline, effectively preparing the estimation in advance while maintaining responsiveness to rapid changes.
2Device complexity
If conventional SOC estimation methods are used, then the estimation process is simple, but the accuracy is affected by differences in statistical characteristics and chemical reaction fluctuations
Solution Approach 1:
The patent introduces an intermediary correction mechanism that mediates between the current integration method and open circuit voltage method. This intermediary layer calculates the difference between the two estimation results and uses it to correct the cumulative errors, thereby improving accuracy without significantly increasing system complexity.
Solution Approach 2:
The system dynamically adjusts the weighting and correction parameters based on the statistical characteristics of the input data and the state of the battery. By changing parameters such as the correction factor and time constants adaptively, the system maintains high accuracy while keeping the estimation process relatively simple.
Data Source
AI summary
A battery's state of charge estimation apparatus will be provided.The battery's state of charge estimation apparatus includes: a charge and discharge current detection unit; a terminal voltage detection unit; an open circuit voltage method state of charge estimation unit for estimating an open circuit voltage of the battery and an open circuit voltage method state of charge; a current integration method state of charge estimation unit for obtaining a current integration method state of charge as a state variable; and an error correction value calculation unit for calculating an error correction value for correcting the current integration method state of charge. The current integration method state of charge estimation unit corrects the current integration method state of charge by using the error correction value.