Fluid Path Resistance Measurement via Isolation Switching in EVs
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Solution Overview
Problem
Existing isolation resistance monitoring systems in electrified vehicles fail to accurately assess the resistance contributions of individual components within the electrical network, particularly in the presence of electrically conducting fluid paths, leading to potential safety hazards and inefficiencies.
Innovation Solution
A computer system and method that determines the electrical resistance of electrically conducting fluid paths by short-circuiting portions of the path and comparing isolation resistance data before and after short-circuiting, allowing for the calculation of fluid resistance and conductivity, thereby eliminating the need for dedicated conductivity sensors and enhancing safety monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional isolation resistance monitoring systems are used to measure resistance between high voltage buses and chassis, then the overall isolation resistance of the network can be assessed, but the resistance contributions of individual components (particularly electrically conducting fluid paths) cannot be determined
Solution Approach 1:
The patent divides the electrical network into separable measurement segments by introducing isolation switches that can disconnect specific components (such as fluid paths) from the main voltage bus. This allows the total isolation resistance to be measured in different configurations, enabling the calculation of individual component resistance contributions through mathematical decomposition of the segmented measurements.
2Measurement precision
If conductivity sensors are used to measure coolant electrical conductivity, then fluid conductivity can be monitored, but the system becomes more expensive and the sensors are susceptible to contamination
Solution Approach 1:
The patent extracts the measurement function from dedicated conductivity sensors and implements it using the existing isolation resistance monitoring infrastructure. By measuring isolation resistance with and without specific fluid paths connected, and applying mathematical calculations, the system derives fluid conductivity information without requiring separate conductivity sensors in the coolant stream, thereby avoiding their associated costs and contamination risks.
Solution Approach 2:
The patent uses isolation switches as intermediary components that enable indirect measurement of fluid conductivity. Instead of placing sensors directly in the coolant, the switches mediate the measurement process by selectively connecting or disconnecting fluid paths from the voltage bus, allowing conductivity inference through resistance measurements taken in different switch states.
3Reliability
If isolation resistance monitoring is performed while the vehicle is operating, then continuous safety monitoring is achieved, but individual component isolation resistance cannot be assessed due to system connectivity
Solution Approach 1:
The patent introduces dynamic reconfigurability to the measurement system through isolation switches that can change the electrical connectivity topology on demand. During operation, the switches can dynamically alter which components are connected to the voltage bus, enabling the system to transition between different measurement states without shutting down, thus maintaining continuous monitoring capability while obtaining component-level data.
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 approach provides reliable and cost-effective monitoring of fluid path resistances, reducing the risk of electrical hazards and improving diagnostic capabilities in vehicles with fuel cell stacks and immersion cooled batteries.
Implementation Method 1
obtain first isolation resistance data between the traction voltage pole and the ground potential
Implementation Method 2
electrically short-circuit a first portion of the first fluid path
Data Source
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AI summary
A computer system is provided. The computer system comprises processing circuitry configured to: electrically connect at least one vehicle subsystem (10) to a traction voltage pole (16, 16A, 16B) of a vehicle (1) and to a ground potential (P), said at least one vehicle subsystem (10) comprising at least a first electrically conducting fluid path (20, 21); obtain first isolation resistance data (224) between the traction voltage pole (16, 16A, 16B) and the ground potential (P); electrically short-circuit a first portion of the first fluid path (20, 21); obtain second isolation resistance data (228) between the traction voltage pole (16, 16A, 16B) and the ground potential (P) when the first portion of the first fluid path (20, 21) is shortcircuited; and determine the electrical resistance of the fluid of the first fluid path (20, 21) of the at least one vehicle subsystem (10) based on the first isolation resistance data (224) and the second isolation resistance data (228).