Battery Excitation Circuit With Offset Voltage for High-Voltage EIS
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Solution Overview
Problem
Existing EIS measurement systems require multiple excitation sources and measurement circuits for each battery cell unit, leading to complex and inefficient setups, especially when dealing with high-voltage battery strings.
Innovation Solution
A single battery excitation unit (BXU) incorporating a bidirectional voltage-controlled current source and Offset Voltage Devices (OVDs) is used to inject current into a battery string, with OVDs providing an opposite polarity voltage to reduce the necessary DC voltage generated by the BXU, allowing the BXU to see the impedance of the battery string more effectively, thus reducing power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple excitation sources and measurement circuits are used for each battery cell unit, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple excitation sources into a single excitation unit that can generate multi-sinusoidal current signals for simultaneous excitation of multiple battery cell units. Similarly, multiple measurement circuits are merged into a single measurement unit that can measure voltage responses from all excited cell units, thereby reducing device complexity while maintaining measurement accuracy
Solution Approach 2:
The excitation unit is designed with universal functionality to serve multiple battery cell units simultaneously through a single device. The measurement unit likewise performs multiple measurement functions across different cell units, making each unit multi-functional rather than dedicated to a single cell unit
2Device complexity
If a single excitation source is used for the entire battery string, then device complexity is reduced, but measurement precision deteriorates due to voltage mismatches
Solution Approach 1:
The patent introduces offset voltage devices as intermediary elements between the single excitation source and the battery cell units. These offset voltage devices compensate for voltage mismatches by providing additional voltage in series, ensuring that the excitation voltage matches the required level for each cell unit while using a single excitation source
Solution Approach 2:
The system dynamically adjusts parameters of the excitation signal and offset voltages to match the specific voltage requirements of different battery cell units. By changing voltage parameters and using programmable power supplies, the system maintains measurement precision across varying battery conditions while using simplified single-source architecture
3Adaptability or versatility
If high voltage capability is provided in the BXU to match battery string voltage, then adaptability is improved, but power rating and energy consumption increase
Solution Approach 1:
The patent segments the voltage provision function into two parts: the excitation unit provides only the AC excitation voltage component, while separate offset voltage devices provide the DC offset voltage component. This segmentation allows the excitation unit to have lower power rating while the system as a whole maintains high voltage capability and adaptability to battery string voltage
Solution Approach 2:
Offset voltage devices act as intermediaries that bridge the voltage gap between the low-power excitation unit and the high-voltage battery string. These devices handle the high voltage requirement without requiring the excitation unit itself to have high power rating, thereby reducing energy consumption while maintaining voltage compatibility
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
This approach simplifies the EIS measurement system by decreasing the power rating of the BXU and enabling accurate impedance measurements across high-voltage battery strings with reduced complexity and power consumption.
Implementation Method 1
For an EIS measurement, multi-sinusoidal current signals are usually injected by the BXU in a battery system, which serve as an excitation-function. The ratio of the voltages and the current in the frequency domain represents the impedance spectra of the cells measured by the BMU.
Implementation Method 2
The BXU is connected in series with the at least one OVD, each of which is configured to provide a voltage with opposite polarity to the Battery String to act as an Offset Voltage to the internal voltage of the Battery Cell Units within the Battery String, such that the BXU largely sees the impedance of the Battery Cell Units within the Battery String to be measured.
Data Source
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AI summary
The invention relates to an an EIS measurement system is provided. The EIS measurement system comprises a battery excitation unit, BXU, (1320) incorporating a bidirectional voltage controlled current source for injecting current into a String of Battery Cell Units consisting of Battery Cell Units (1001, 1002) (a "Battery String") of the battery for an EIS measurement, and at least one Offset Voltage Device (OVD) (1350). The BXU is connected in series with the at least one OVD, each of which is configured to provide a voltage with opposite polarity to the Battery String to act as an Offset Voltage to the internal voltage of the Battery Cell Units within the Battery String, such that the BXU largely sees the impedance of the Battery Cell Units within the Battery String to be measured.