EV High-Voltage Insulation Monitoring Against Charger Bus Interference
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Solution Overview
Problem
Existing insulation monitoring systems for electric vehicles may incorrectly detect insulation faults when multiple vehicles are charged simultaneously, leading to erroneous termination of the charging process due to interference between multiple insulation monitoring devices and ground interference couplings.
Innovation Solution
A method is introduced to cyclically check for the presence of additional insulation monitoring devices on the high-voltage bus, by deactivating the active portion of the insulation monitoring device for a defined plausibility-check time, and evaluating the measured potential differences for a low-frequency, cyclic pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple insulation monitoring devices are activated simultaneously on the high-voltage bus, then continuous insulation monitoring is maintained, but erroneous detection of insulation faults occurs due to interference between devices
Solution Approach 1:
The patent implements periodic action by cyclically activating and deactivating the insulation monitoring device. The device is deactivated for a defined plausibility-check time period to check for the presence of other monitoring devices, then reactivated for insulation monitoring. This periodic on-off cycle prevents continuous interference while maintaining monitoring functionality.
Solution Approach 2:
The patent applies preliminary action by performing a plausibility check before conducting insulation resistance determination. The system first checks whether other insulation monitoring devices are present on the high-voltage bus, and only proceeds with insulation monitoring if the check confirms no other devices are active, thereby preventing erroneous detections from the outset.
2Measurement precision
If insulation monitoring devices are continuously active, then insulation faults can be detected in real-time, but charging interruptions occur due to false fault detections
Solution Approach 1:
The patent implements feedback by evaluating measured potential differences for characteristic patterns that indicate the presence of other monitoring devices. The system uses the measured values from the three-voltmeter method to determine whether other devices are active, and based on this feedback, decides whether to proceed with insulation resistance determination or terminate the charging process to avoid false fault detections.
3Measurement precision
If the three-voltmeter method is used for insulation monitoring, then insulation resistances can be calculated from potential differences, but ground interference couplings cause erroneous insulation fault detections
Solution Approach 1:
The patent uses the plausibility check as an intermediary step between potential difference measurement and insulation resistance calculation. Before calculating insulation resistances from the measured potential differences, the system performs an intermediary check to detect the presence of other monitoring devices, thereby filtering out ground interference couplings that would otherwise cause erroneous fault detections.
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 method effectively prevents erroneous detections of insulation faults, thereby avoiding charging interruptions and improving overall charging availability by distinguishing between actual insulation faults and interference from other monitoring devices.
Implementation Method 1
Two insulation monitoring devices monitor two different power supply units. The insulation monitoring devices alternately are connected to ground and disconnected from ground by a contactless switch.
Implementation Method 2
A first and a second pulse width modulation are carried out on the two semiconductor switches. A first and a second pair of resistance values of the two series circuits are modulated by means of the respective pulse width modulations.
Data Source
AI summary
A method is provided for checking the plausibility of insulation monitoring of a high-voltage system (100) of an electric vehicle during the charging of a traction battery of the electric vehicle. The electrical insulation of the high-voltage system (100) is monitored by an insulation monitoring device (101), and a check is carried out cyclically to determine whether a further insulation monitoring device is active on a high-voltage bus of the high-voltage system (100).