HV Circuit Isolation Control for Vehicle Water Exposure
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Solution Overview
Problem
High voltage (HV) circuits in vehicles, such as hybrid electric vehicles, face shutdown due to loss of isolation upon water contact, rendering the vehicle temporarily unusable even after the cause of isolation loss is removed, as existing systems lack the ability to re-enable the HV circuit based on changing isolation resistance and driver intent.
Innovation Solution
A method and system that detect changes in isolation resistance and driver inputs, such as speed intentions, to re-enable the HV circuit when conditions become safe, using contactors to manage the HV battery connection and prioritizing low voltage circuit operation for critical vehicle functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the HV circuit is shut down upon detection of isolation loss, then safety is improved, but vehicle usability deteriorates
Solution Approach 1:
The system dynamically adjusts the isolation resistance threshold for HV circuit shutdown based on vehicle operating conditions, particularly water depth detection. When water contact is detected, the threshold is temporarily adjusted to allow higher isolation resistance values, enabling the HV circuit to remain operational during legitimate water exposure while still protecting against actual isolation failures.
Solution Approach 2:
The system changes the parameter of isolation resistance threshold dynamically based on detected conditions. By adjusting this parameter according to water depth sensors and operational context, the system distinguishes between temporary water-induced resistance changes and permanent isolation failures, thereby maintaining usability while ensuring safety.
2Reliability
If the HV circuit is immediately shut down upon isolation loss detection, then safety response time is improved, but operational continuity deteriorates
Solution Approach 1:
The system performs preliminary assessment of the isolation loss condition by checking multiple parameters including water depth, rate of change of isolation resistance, and operational context before initiating shutdown. This preliminary action allows the system to distinguish between reversible water contact scenarios and permanent failures, maintaining operational continuity when appropriate while ensuring rapid shutdown when necessary.
Solution Approach 2:
The system continuously monitors isolation resistance and provides feedback to the control logic, which adjusts the shutdown decision based on the trend and context of the isolation change. This feedback mechanism enables the system to respond appropriately to developing conditions, maintaining operation during temporary disturbances while ensuring rapid shutdown when isolation loss becomes permanent.
3Ease of operation
If the HV circuit operates during water contact, then vehicle mobility is improved, but risk of electrical contact deteriorates
Solution Approach 1:
The system introduces water depth sensors and contextual monitoring as intermediaries between the HV circuit and the water environment. These intermediaries provide information about the nature and extent of water contact, enabling the control system to make informed decisions about continued operation while implementing additional safety measures such as adjusted isolation thresholds and enhanced monitoring protocols.
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 the HV circuit to resume operation when isolation status improves and vehicle speed exceeds a threshold, allowing the vehicle to continue moving and extending its operational range, especially in off-road conditions, while ensuring safety by disabling the HV circuit during hazardous conditions.
Implementation Method 1
detecting a change in an isolation resistance of the high voltage circuit from the low voltage circuit
Data Source
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AI summary
A method of controlling an isolated high voltage circuit of a vehicle comprising the high voltage circuit and a low voltage circuit wherein the high voltage circuit is isolated from the low voltage circuit, the method comprising: detecting a change in an isolation resistance of the high voltage circuit from the low voltage circuit; determining a speed of the vehicle; operating the high voltage circuit in dependence on the change in the isolation resistance and the speed of the vehicle.