Battery Impedance Calculation via Frequency Component Extraction
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Solution Overview
Problem
Existing methods for calculating the impedance of chargeable and dischargeable batteries struggle to do so during vehicle travel due to the dependency on specific power patterns generated by driver operations, making it difficult to accurately assess resistance deterioration.
Innovation Solution
A state calculating apparatus and method that measure current and voltage, extract frequency components, and calculate impedance using a phase difference-based approach to identify a local minimum frequency band for stable impedance calculation, allowing for impedance calculation from arbitrary power patterns without generating a dedicated power pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated power pattern is generated and input to the battery to calculate impedance, then measurement precision is improved, but device complexity and ease of operation deteriorate due to the need for dedicated power generation control
Solution Approach 1:
The battery system uses its own operational current and voltage data during normal vehicle travel to perform impedance measurement, without requiring external dedicated power patterns or separate measurement systems. The existing power flow during vehicle operation serves the dual purpose of driving the vehicle and providing measurement signals.
Solution Approach 2:
The same current and voltage measurement systems used for monitoring battery status during normal operation are also utilized for impedance measurement. The power control unit serves both as a vehicle control system and as a signal generation system for impedance calculation, eliminating the need for dedicated measurement hardware.
2Measurement precision
If a dedicated power pattern is generated and input to the battery to calculate impedance, then measurement precision is improved, but productivity deteriorates due to extended measurement time and complex power pattern generation
Solution Approach 1:
Impedance measurement occurs continuously during normal vehicle operation without interrupting the vehicle's travel or requiring separate measurement sessions. The measurement process utilizes the ongoing power flow between battery and motor generator, making the measurement continuous rather than periodic or batch-based.
Solution Approach 2:
The battery system performs self-diagnosis during normal operation by utilizing its own operational data. The existing current and voltage measurements taken for monitoring purposes are repurposed for impedance calculation, eliminating the need for dedicated measurement time or separate testing procedures.
3Ease of operation
If impedance calculation is performed during vehicle travel using arbitrary power patterns, then ease of operation and productivity are improved, but measurement precision deteriorates without a dedicated power pattern
Solution Approach 1:
The system uses feedback from the measured current and voltage to calculate impedance in real-time during vehicle operation. The impedance value is continuously updated based on the actual power flow conditions, allowing the system to adapt to varying operating conditions while maintaining measurement accuracy.
Solution Approach 2:
The system calculates impedance across different frequency components by analyzing the relationship between current and voltage at various frequencies present in the arbitrary power pattern during vehicle operation. This allows extraction of impedance characteristics at multiple frequency points without requiring dedicated sinusoidal test signals.
4Productivity
If impedance calculation is performed during vehicle travel using arbitrary power patterns, then productivity is improved, but measurement precision deteriorates without a dedicated power pattern
Solution Approach 1:
Impedance measurement occurs continuously during normal vehicle operation without interrupting the vehicle's travel or requiring separate measurement sessions. The measurement process utilizes the ongoing power flow between battery and motor generator, making the measurement continuous rather than periodic or batch-based.
Solution Approach 2:
The system uses feedback from the measured current and voltage to calculate impedance in real-time during vehicle operation. The impedance value is continuously updated based on the actual power flow conditions, allowing the system to adapt to varying operating conditions while maintaining measurement accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the calculation of battery impedance during vehicle travel from any power pattern, providing accurate resistance deterioration assessment equivalent to methods requiring dedicated power patterns, with reduced measurement time and improved precision.
Implementation Method 1
search a frequency band in which a phase difference between the current and the voltage of the battery has a local minimum
Data Source
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AI summary
A BMU (100), which is a battery management unit, includes a current measuring unit (10) that measures a current charged to and discharged from a battery (5); a voltage measuring unit (20) that measures a voltage of the battery (5) during measurement of the current by the current measuring unit (10); a BPF processing unit (30) that extracts a component in a prescribed frequency band, of the current measured by the current measuring unit (10); a BPF processing unit (40) that extracts a component in the prescribed frequency band, of the voltage measured by the voltage measuring unit (20); and an impedance calculating unit (50) that calculates an impedance of the battery (5) using the extracted current component and voltage component.