Power Converter Isolation Loss Detection in Electric Vehicles
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Solution Overview
Problem
Existing technologies struggle to quickly and accurately diagnose a loss of isolation in electric motors of vehicles, which can lead to degradation and inoperability due to mechanical stresses or short-circuiting, necessitating prolonged maintenance and downtime.
Innovation Solution
A method and apparatus for monitoring normalized voltage in a vehicle's electrical system to detect alternating current (AC) and direct current (DC) loss of isolation events by analyzing voltage extremas and thresholds, initiating remedial actions when predefined conditions are met, and providing diagnostic codes or notifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional monitoring methods are used, then system complexity is reduced, but detection speed and accuracy of loss of isolation deteriorates
Solution Approach 1:
The patent segments the voltage monitoring into multiple discrete analysis steps: obtaining raw voltage signals, filtering to remove noise, detecting zero-crossing points, calculating phase differences, and comparing against thresholds. This segmentation transforms a complex diagnostic problem into manageable sequential operations that improve detection accuracy without requiring overly complex hardware
Solution Approach 2:
The system performs preliminary filtering and preprocessing of voltage signals before actual loss of isolation detection. By pre-processing the signals to remove noise and extract relevant features (zero-crossing points, phase information), the system prepares the data in advance, enabling faster and more accurate detection when a fault condition occurs
2Speed
If continuous monitoring is implemented, then detection speed improves, but energy consumption increases
Solution Approach 1:
The patent implements periodic monitoring at the power conversion module's switching frequency rather than continuous monitoring. The system analyzes voltage signals at regular intervals synchronized with the inverter switching cycles, which maintains detection speed by capturing critical fault information while significantly reducing computational load and energy consumption compared to continuous analysis
3Measurement precision
If sophisticated diagnostic algorithms are used, then measurement precision improves, but computational requirements increase
Solution Approach 1:
The patent uses a simplified computational model that copies only the essential features of the electrical system behavior needed for diagnosis. Instead of simulating the entire power conversion system, the algorithm extracts and analyzes key indicators (voltage phase relationships, zero-crossing timing) that replicate the diagnostic information needed to detect loss of isolation, reducing computational requirements while maintaining accuracy
Data Source
AI summary
Vehicles and related systems and monitoring methods are provided for detecting a loss of isolation on one side of a power converter. One method involves monitoring a normalized voltage input to a power conversion module coupled to the electric motor, in response to the normalized voltage exceeding a diagnostic activation threshold, determining a first number of instances of a range between successive extremas of the normalized voltage exceeding a loss of isolation range threshold over a diagnostic window of time, and automatically initiating a remedial action when the first number is greater than a loss of isolation detection threshold.