Inverter Abnormality Detection Using Dynamic Thresholds
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Solution Overview
Problem
Existing techniques for detecting short-circuit failures in inverters used to control motor generators are prone to erroneous detection when the reverse voltage of the motor generator is higher than the system voltage, as they fail to distinguish between normal and abnormal current flows under gate blocking conditions.
Innovation Solution
An abnormality detection apparatus that adjusts the threshold value for detecting electric current based on a predetermined process, such as smoothing, to differentiate between normal and abnormal conditions, ensuring accurate detection by using different threshold values depending on the relative magnitudes of reverse and system voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed threshold value is used for detecting short-circuit failures, then the detection method is simple, but erroneous detection occurs when reverse voltage exceeds system voltage
Solution Approach 1:
The threshold value is changed from a fixed constant to a dynamic value that adapts based on system voltage conditions. The controller dynamically adjusts the threshold between a first threshold (when reverse voltage ≤ system voltage) and a second threshold (when reverse voltage > system voltage), eliminating erroneous detection while maintaining simplicity.
Solution Approach 2:
The detection threshold parameter is modified based on the operating condition (voltage relationship between motor generator and inverter). By changing the threshold parameter according to whether reverse voltage exceeds system voltage, the system achieves accurate detection across different operating states without complex additional hardware.
2Reliability
If the threshold value is increased to avoid erroneous detection during high reverse voltage, then false positives are reduced, but detection sensitivity decreases for actual short-circuit failures
Solution Approach 1:
The threshold dynamically switches between two values based on voltage conditions. During normal high reverse voltage operation, the higher second threshold prevents false positives. During actual short-circuit detection, the system returns to using the more sensitive first threshold, ensuring both false positive reduction and maintained detection sensitivity.
Solution Approach 2:
The system preliminarily determines the voltage relationship between motor generator and inverter before setting the threshold. This preliminary assessment allows the system to pre-select the appropriate threshold value, ensuring optimal detection sensitivity or false positive reduction depending on the current operating condition.
Data Source
AI summary
An abnormality detection apparatus configured to detect an abnormality of an inverter provided to control a motor generator when a value obtained by performing a predetermined process for a current value representing electric current flowing between an arm included in the inverter and the motor generator is greater than a threshold value, wherein when a reverse voltage by the motor generator is higher than a system voltage, the threshold value is larger than a value obtained by performing the predetermined process for electric current generated by the reverse voltage.