UPS Battery Ground Fault Detection via Impedance Segmentation
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Solution Overview
Problem
Existing methods for detecting ground faults in batteries of uninterrupted power supplies (UPS) are limited, as they cannot reliably localize the fault and are not applicable to all UPS configurations, especially those with non-isolated inputs.
Innovation Solution
A method involving defining multiple individual battery blocks, performing reference and verification impedance measurements, and evaluating changes in measured impedance to identify and localize ground faults using a battery management system (BMS) without requiring complex current measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bridge circuit is used for ground fault detection, then ground fault can be detected in UPS with isolated input, but it is not applicable for UPS with non-isolated inputs
Solution Approach 1:
The patent implements a ground fault detection method that works universally across different UPS configurations (both isolated and non-isolated inputs) by using impedance measurements that can be performed with existing BMS infrastructure. The method adapts to different system topologies without requiring specialized bridge circuits for each configuration.
Solution Approach 2:
The patent replaces the traditional electrical bridge circuit with an impedance-based measurement approach that uses voltage and current measurements. This substitution eliminates the need for physical bridge circuit hardware and makes the detection method applicable to various UPS configurations including non-isolated inputs.
2Reliability
If current sensing summation is used for ground fault detection, then ground fault can be detected in UPS with non-isolated input, but localization of ground fault is not enabled
Solution Approach 1:
The patent divides the battery system into multiple individual battery blocks and performs impedance measurements on each block separately. By comparing impedance changes across different segments (battery blocks), the system can both detect the presence of a ground fault and localize its position within the battery string.
Solution Approach 2:
The patent uses impedance measurements as feedback to continuously monitor the state of individual battery blocks. By analyzing changes in impedance values over time and comparing them across different blocks, the system provides feedback that enables both detection and localization of ground faults.
3Measurement precision
If direct measurement of ground fault impedance is used, then ground fault can be detected, but the technique is limited to certain types of UPS
Solution Approach 1:
The patent uses impedance measurements of individual battery blocks as an intermediary approach. Instead of directly measuring ground fault impedance (which is limited to certain UPS types), the method measures the impedance of battery blocks and uses changes in these measurements to indirectly detect and locate ground faults, making it compatible with all UPS types.
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 reliable detection and localization of ground faults in a simple and cost-effective manner, applicable to various UPS configurations, including those with non-isolated inputs, by utilizing existing BMS functionality for impedance measurements.
Implementation Method 1
performing a reference impedance measurement for the multiple individual battery blocks, performing a verification impedance measurement for the multiple individual battery blocks, evaluating a change of measured impedance between the reference impedance and the verification impedance
Data Source
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AI summary
The present invention provides a method for detecting a ground fault (60) in a battery (22) of a uninterrupted power supply (10, 40), the battery (22) comprises at least one string (26) with multiple battery cells, the method comprising the steps of defining multiple individual battery blocks (28) of battery cells along the at least one string (26), performing an reference impedance measurement for the multiple individual battery blocks (28) at a first point of time, performing a verification impedance measurement for the multiple individual battery blocks (28) at a second point of time, evaluating a change of measured impedance between the reference impedance and the verification impedance for the multiple individual battery blocks (28) of the at least one string (26), and identifying a ground fault (60) based on a correlated change of measured impedance of the multiple individual battery blocks (28) along the at least one string (26). The present invention also provides a battery management system (36) for managing a battery (22) of a uninterrupted power supply (10, 40), which is adapted to perform the above method. The present invention further provides a UPS device (10) and a UPS system (40), each of which comprising an above battery management system (36).