ANPC Converter Switch Failure Detection During Turn-Off Blocking
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Solution Overview
Problem
Existing methods for detecting switching device failure conditions in multi-level power converters, such as those used in wind turbines and solar power generation systems, are inadequate as they do not detect failures when the switching device is turned OFF, leading to potential chain reactions and damage to the converter.
Innovation Solution
A computer-implemented method and system that uses a failure detection algorithm to generate blocking state logic signals by comparing switching device voltages with a threshold reference voltage, determining expected voltage blocking states based on gate drive signals and output current direction, and detecting failures in switching devices within an active neutral point clamped topology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a desaturation circuit is used for failure detection, then failure conditions during turn-ON can be detected, but failure conditions during turn-OFF cannot be detected
Solution Approach 1:
The failure detection function is segmented into two independent detection paths: one for turn-ON failures (using desaturation detection) and one for turn-OFF failures (using voltage blocking state detection). This segmentation allows each path to specialize in detecting specific failure conditions without interfering with the other, thereby achieving comprehensive failure coverage.
Solution Approach 2:
The control circuit is designed to perform multiple functions: it既能 detect turn-ON failures through desaturation detection,又能 detect turn-OFF failures through voltage blocking state detection. By integrating these two detection capabilities into a single control circuit, the system achieves universal failure detection coverage without requiring separate independent systems.
2Power
If switching devices operate under high electrical and thermal stress, then power conversion capability is maintained, but thermal breakdown and voltage breakdown occur leading to device destruction
Solution Approach 1:
The control circuit continuously monitors the voltage blocking state of switching devices before actual failure occurs. By detecting abnormal voltage blocking conditions in advance (during both turn-ON and turn-OFF states), the system can trigger protective actions before thermal breakdown or voltage breakdown destroys the device, thereby preventing catastrophic failure while maintaining normal power conversion operation.
3Measurement precision
If switching devices are monitored only during turn-ON state, then turn-ON failures are detected, but turn-OFF failures remain undetected
Solution Approach 1:
The detection mechanism dynamically adapts to the switching device's operational state. The control circuit switches between different detection methods based on the device state: using desaturation detection during turn-ON and voltage blocking state detection during turn-OFF. This dynamic adaptation ensures precise failure detection across all operational phases of the switching device.
Data Source
AI summary
A method for operating a multi-level bridge power converter includes arranging a plurality of switching devices including at least four inner switching devices and at least two outer switching devices in an active neutral point clamped topology. The method also includes determining whether any of the switching devices is experiencing a failure condition by implementing a failure detection algorithm. The failure detection algorithm includes generating a blocking state logic signal by comparing a switching device voltage and a threshold reference voltage for each of the switching devices, determining an expected voltage blocking state for each of the switching devices based on gate drive signals of the switching devices and an output current direction, and detecting whether a failure condition is present in any of the switching devices based on the blocking state logic signals and the expected voltage blocking states of the switching devices.