Battery Discharge Estimation from Partial SOC Profiles
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Solution Overview
Problem
Existing methods for diagnosing the capacity of energy storage devices require stopping the operation of the system, leading to inaccuracies in capacity estimation due to partial discharge characteristics being used, which do not accurately represent the overall discharge characteristics.
Innovation Solution
An estimation device that acquires time-series data of current and voltage, calculates electricity and state of charge (SOC), generates a partial charge/discharge profile, and estimates the overall discharge characteristic using an adjusted internal state amount parameter to match the partial profile, allowing estimation without system shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the complete charge and discharge method is used to diagnose energy storage device capacity, then measurement precision is improved, but the system operation is interrupted and productivity is reduced
Solution Approach 1:
The system performs preliminary characterization of the energy storage device by acquiring current-voltage time-series data and calculating state of charge during normal operation. This preliminary action builds a partial charge/discharge profile that serves as the foundation for subsequent capacity estimation without requiring complete discharge, thus maintaining system operation while gathering necessary diagnostic information.
Solution Approach 2:
The system creates a computational model that copies the essential characteristics of the complete charge/discharge curve by using the partial profile obtained during operation. By adjusting the internal state amount parameter to match the partial profile and extrapolating to estimate the overall discharge characteristic, the system generates a virtual representation of complete discharge behavior without actually performing complete discharge, thereby avoiding system interruption.
2Productivity
If partial discharge characteristic data is used during system operation, then productivity is maintained, but measurement precision deteriorates due to insufficient discharge characteristic information
Solution Approach 1:
The system changes the parameter representation from raw current-voltage-time data to state of charge-based profiles. By calculating state of charge from current integration and transforming the partial discharge data into SOC-voltage relationships, the system creates a standardized representation that can be compared with and used to estimate the overall discharge characteristic, improving measurement precision from partial data.
Solution Approach 2:
The system uses feedback by comparing the calculated partial charge/discharge profile with the estimated overall discharge characteristic. The internal state amount parameter is adjusted iteratively to minimize the difference between the partial profile (from actual measurement) and the corresponding section of the overall discharge characteristic (from estimation), thereby improving accuracy through continuous refinement.
Data Source
AI summary
An estimation device includes: an acquisition portion acquiring time-series data of a current and a voltage of an energy storage device; a calculation portion calculating time-series data of an amount of electricity or an SOC, based on the time-series data of the current and the voltage acquired by the acquisition portion; a generation portion generating a partial charge/discharge profile of the energy storage device, based on the time-series data of the current and the voltage acquired by the acquisition portion and the time-series data of the amount of electricity or the SOC calculated by the calculation portion; and an estimation portion estimating an overall discharge characteristic of the energy storage device, based on a parameter representing an internal state amount of the energy storage device, the parameter being adjusted in such a way that a profile of a predetermined section in the overall discharge characteristic of the energy storage device approaches the partial charge/discharge profile.