DC Intermediate Circuit Ground Fault Detection Modulation
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Solution Overview
Problem
Detecting ground faults in DC voltage intermediate circuits, particularly in floating designs, is challenging as it is difficult to distinguish between faults within the auxiliary device and those affecting the intermediate circuit.
Innovation Solution
A ground fault detection device is integrated into the DC voltage intermediate circuit, comprising a voltage divider with a center connection at ground potential, a modulation device that modulates the intermediate circuit voltage, and an evaluation device that uses partial voltage values to determine if a ground fault has occurred by analyzing the proportionality between the intermediate circuit voltage and the voltage at the voltage source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage divider is connected to the DC link for ground fault detection, then ground faults can be detected, but it is difficult to distinguish between faults within the auxiliary device and those affecting the intermediate circuit
Solution Approach 1:
The patent applies periodic action by modulating the DC link voltage using a modulation device that varies the voltage at a defined modulation frequency. This periodic modulation allows the evaluation device to distinguish between auxiliary device faults and intermediate circuit faults by analyzing the frequency characteristics of the measured partial voltage, thereby resolving the ambiguity in fault location detection
Solution Approach 2:
The patent changes the voltage parameter by modulating the DC link voltage between different levels (first and second voltage levels) at a defined modulation frequency. This parameter change enables the detection system to differentiate fault locations by observing how the partial voltage responds to the voltage modulation, solving the problem of indistinguishable fault conditions
2Stability of the object's composition
If the DC link voltage is kept constant for stable operation, then system stability is maintained, but ground faults within the auxiliary device cannot be reliably detected
Solution Approach 1:
The patent introduces periodic voltage modulation superimposed on the stable DC link voltage. The modulation device periodically varies the voltage between first and second levels at a defined modulation frequency, enabling fault detection while maintaining overall system stability through controlled, periodic perturbations
Solution Approach 2:
The patent transitions from a static DC link voltage to a dynamic modulated voltage by introducing a modulation device that continuously varies the voltage according to a defined modulation pattern. This dynamic approach enables fault detection capabilities while the modulation is designed to maintain system operational stability
3Difficulty of detecting and measuring
If voltage modulation is applied to enable ground fault detection, then auxiliary device faults can be distinguished from intermediate circuit faults, but system complexity increases
Solution Approach 1:
The patent achieves multi-functionality by integrating the modulation device and evaluation device into the existing ground fault detection system. The modulation device not only modulates the voltage for detection purposes but also provides diagnostic information about fault locations, while the evaluation device processes multiple measurement signals to identify both auxiliary device and intermediate circuit faults
Solution Approach 2:
The patent introduces a modulation device as an intermediary between the DC link and the measurement system. This intermediary modulates the voltage in a controlled manner, enabling the evaluation device to extract fault location information from the measured partial voltage without requiring direct access to all system components
Data Source
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AI summary
The invention relates, among other things, to a vehicle (10) with a DC intermediate circuit (60) and at least one auxiliary device (100) comprising a DC voltage converter (110) and a voltage source (120) connected to the DC intermediate circuit (60) by means of the DC voltage converter (110).According to the invention, a ground fault detection device (200) is connected to the DC link (60), comprising: a voltage divider (210) with a center terminal (M) connected to ground potential (GND), a voltage measuring device (220) connected to a divider element (R2) of the voltage divider (210), a modulation device (240) that modulates the DC link voltage (Uzk) of the DC link (60) over time, and an evaluation device (230) that determines, on the basis of a partial voltage value (Um) indicating the voltage at the divider element (R2) and a modulated DC link voltage value (Uz) indicating the modulated DC link voltage (Uzk) at the DC link (60), whether one of the terminals (Q1, Q2, 61, 62) of the voltage source (120) or of the DC link (60) is affected by a ground fault.