Ground Fault Detector Threshold Adaptation
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Solution Overview
Problem
Existing ground fault detectors for high-tension power systems in vehicles require complex circuitry to detect phase differences and are inaccurate due to changes in common mode capacitor capacitance when relays are switched, making it difficult to precisely locate ground faults.
Innovation Solution
A ground fault detector that adjusts its threshold settings based on the state of the vehicle, specifically the capacitance of the common mode capacitor, allowing for accurate detection without complex circuitry by using multiple thresholds for different relay states (ON or OFF) and inverter types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the detector uses complex circuitry to detect phase differences for admittance component detection, then the detection capability is improved, but the device complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for complex phase difference detection circuits by using a simplified threshold-based detection method. Instead of measuring admittance components through complex circuitry, the system uses a microcontroller to directly compare detected signals against pre-stored thresholds, thereby reducing circuit complexity while maintaining detection accuracy.
Solution Approach 2:
The patent replaces complex analog circuit-based phase difference detection with a digital processing approach using a microcontroller. The microcontroller digitally compares signal characteristics against stored thresholds, substituting the mechanical/analog circuit complexity with software-based decision logic,从而简化了硬件电路结构.
2Device complexity
If the detector uses a fixed threshold for ground fault detection, then the circuitry is simple, but the detection accuracy decreases when vehicle state changes
Solution Approach 1:
The patent implements dynamic threshold adjustment by storing multiple thresholds in the microcontroller corresponding to different vehicle states (e.g., relay ON/OFF, inverter types). The system dynamically selects the appropriate threshold based on the current vehicle state, allowing accurate ground fault detection across varying conditions without changing the physical circuitry.
Solution Approach 2:
The patent changes the detection parameter (threshold value) based on vehicle state conditions. Instead of using a fixed threshold, the system adjusts the threshold parameter according to whether the relay is ON or OFF, or based on the specific inverter type, thereby maintaining high detection accuracy across different operating conditions while keeping the circuit simple.
3Ease of operation
If the relay is switched ON or OFF, then the power supply control is achieved, but the common mode capacitor capacitance changes significantly
Solution Approach 1:
The patent performs preliminary action by pre-storing multiple detection thresholds in the microcontroller before the actual detection occurs. These thresholds are prepared in advance for different relay states and inverter types, allowing the system to immediately select the correct threshold when ground fault detection is needed, thus compensating for the capacitance changes caused by relay switching without requiring additional circuit adjustments.
Data Source
AI summary
A ground fault detector which does not need complicated circuitry and can detect a ground fault with high accuracy in conformity to a capacitance of a common mode capacitor is presented. Upon judging the ground fault on the basis of a threshold for a high-tension power supply system which is electrically isolated and mounted in a vehicle, a controller in a ground fault detector alters the threshold in conformity to a capacitance of a common mode capacitor of which value is different between a first state that a system main relay is ON and a second state that the system main relay is OFF, thereby judges the ground fault on the basis of the altered threshold. Thus the ground fault detector can adequately detect the ground fault in conformity to the capacitance of the common mode capacitor. Thus the detector can detect the ground fault with accuracy without complicated circuitry.