Inverter Switch Failure Detection Using Mid-Pack Voltage
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Solution Overview
Problem
In hybrid vehicles, diagnosing failures in electric power trains is challenging due to the difficulty in distinguishing between electric machine and inverter failures, leading to unnecessary replacements and expenses, as existing methods lack efficient instrumentation for identifying individual power electronic switch failures.
Innovation Solution
A method that uses existing mid-pack voltage sensors to detect common mode voltage by commanding all power electronic switches to open and then opening and closing one switch at a time at a specific duty cycle and frequency, identifying functional or non-functional switches based on mid-pack voltage measurements, without requiring additional hardware and allowing for on-line status determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If visual inspection of high voltage cables is performed, then cable faults can be easily identified, but inverter and electric machine failures cannot be distinguished
Solution Approach 1:
The patent segments the inverter system into individual testable units by isolating each power electronic switch and its associated diode through discrete testing circuits. This allows each component to be tested independently, enabling precise identification of which specific switch or diode has failed, rather than treating the entire inverter as a single unit.
Solution Approach 2:
The patent introduces intermediary testing circuits including test voltage sources, current indicators, and measurement devices that mediate between the power electronic switches and the diagnostic system. These intermediaries enable indirect observation of switch and diode functionality through measurable electrical parameters without requiring direct access to the switching components during operation.
2Productivity
If power inverter is replaced without confirmation, then vehicle may be restored, but unnecessary expenses are incurred
Solution Approach 1:
The patent performs preliminary diagnostic testing of power electronic switches and diodes before any replacement decisions are made. By conducting advance tests that definitively identify faulty components, the system enables informed replacement decisions that avoid unnecessary part replacements while ensuring that actual failures are addressed, thus optimizing both cost and restoration efficiency.
3Measurement precision
If additional instrumentation is added to detect switch failures, then diagnostic precision improves, but device complexity increases
Solution Approach 1:
The patent designs testing circuits that can universally test multiple types of power electronic switches (IGBTs, MOSFETs, BJTs) and diodes using the same basic test architecture. The test circuits are configured to work with different switch types through standardized connection points and measurement methods, eliminating the need for separate specialized instrumentation for each component type.
Solution Approach 2:
The patent enables the power electronic components to self-test by incorporating test functions that utilize the components' own electrical characteristics. The testing method uses the inherent diode recovery behavior and switching characteristics of the power devices themselves as the basis for diagnosis, reducing the need for external complex testing equipment.
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 reliably identifies individual power electronic switch failures quickly, potentially saving costs by accurately determining the source of electrical power train failures and enabling on-line monitoring of switch status, without additional hardware, and can be applied during vehicle operation or maintenance.
Implementation Method 1
a mid-pack voltage is measured by using the mid-pack voltage sensor; the closed switch is identified as functional in case a common mode voltage is detected by the mid-pack voltage sensor
Data Source
AI summary
In a method for detecting an inverter hardware failure in an electric power train comprising high voltage cables, at least one electric machine and at least two inverter legs with two power electronic switches respectively for pulse-width-modulating a DC voltage from a high voltage battery for energizing the at least one electric machine, and including at least one mid-pack voltage sensor for detecting isolation faults, wherein all power electronic switches are demanded to open; at least one of the power electronic switches of one of the inverter legs is opened and closed at a time at a given duty cycle and a given frequency; a mid-pack voltage is measured using the mid-pack voltage sensor; the closed switch is identified as functional in case a common mode voltage is detected by the mid-pack voltage sensor or otherwise the closed switch is identified as non-functional.