Modular Inverter Open-Circuit Fault Detection Using Temperature Sensors
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Solution Overview
Problem
Existing open-circuit fault detection methods for modular general purpose inverters are either not applicable or require additional sensors/circuits, making them unsuitable for cost-effective solutions.
Innovation Solution
A self-diagnostic method that uses temperature data from existing sensors to detect, identify, and localize open-circuit faults in modular inverters, without the need for dedicated fault detection sensors or additional circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prior-art open-circuit diagnostic methods based on current symmetry are used, then fault detection is possible in classical inverters, but they are not applicable to modular inverters where current symmetry is maintained by parallel healthy blocks
Solution Approach 1:
The patent introduces temperature as an intermediary parameter to detect open-circuit faults in modular inverters. Instead of relying on current symmetry which is maintained by parallel healthy blocks, the method uses temperature differences of power semiconductor devices as a mediator to identify faulty switches, making the diagnostic method applicable to modular inverter architecture
Solution Approach 2:
The patent replaces the electrical measurement approach (current symmetry analysis) with a thermal measurement approach (temperature monitoring). This substitution allows fault detection in modular inverters where electrical symmetry is maintained, by detecting thermal asymmetries caused by open-circuit faults in parallel-connected power devices
2Measurement precision
If additional dedicated sensors and circuits are added for fault detection, then diagnostic accuracy is improved, but device complexity and cost increase making it unsuitable for cost-sensitive applications
Solution Approach 1:
The patent makes temperature sensors serve multiple functions: their primary function for thermal management and their secondary function for open-circuit fault detection. This multi-functionality eliminates the need for dedicated fault detection sensors and circuits, reducing device complexity and cost while maintaining diagnostic accuracy
Solution Approach 2:
The patent enables the inverter's existing temperature monitoring system to perform self-diagnosis of open-circuit faults. The system uses its own temperature sensors and control unit to automatically detect, identify, and locate faults without requiring external diagnostic equipment or additional dedicated sensing circuits
3Reliability
If modular inverter architecture with parallel blocks is used, then fault tolerance and repairability are improved, but fault localization becomes more difficult since healthy blocks maintain normal output waveforms
Solution Approach 1:
The patent applies local quality monitoring by individually measuring the temperature of each power semiconductor device in parallel blocks. Instead of monitoring overall phase current symmetry, the method locally monitors temperature of each switch (Q1-Q6) to identify which specific device has an open-circuit fault, enabling precise fault localization in modular architecture
Solution Approach 2:
The patent segments the monitoring approach by individually tracking temperature of each power device in parallel blocks rather than monitoring the aggregate phase current. This segmentation allows identification of the specific faulty device (e.g., Q3 in block B1) even when other parallel blocks maintain normal operation and current symmetry
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
The method provides reliable detection and accurate localization of open-circuit faults, allowing for timely repair and minimizing the risk of secondary failures, all while maintaining the operational integrity of the inverter.
Implementation Method 1
said method comprising a first loop comprising: sampling and storing temperatures data Tkp of said n blocks (k=1 . . . n) in a phase leg measured by said temperature sensors
Data Source
AI summary
Self-diagnostic method (100) of open-circuit fault, in power switching blocks of a modular inverter comprising a plurality (k=1 . . . n) of blocks (31a, 32a, 33a, 34a, 31b, 32b, 33b, 34b, 31c, 32c, 33c, 34c) in parallel per phase leg (5, 5a, 5b, 5c), and being provided with temperature sensors (6), said method comprising: —sampling and storing (130) temperatures data (I) of said n blocks in a phase leg measured by said temperature sensors at relevant sampling times tSD with a relevant sampling interval ΔtSD; —comparing (150) said temperature data (I) of each (k) block with previously sampled and stored temperature data (II) of said each (k) block and considering a possible fault (FF) on one of said blocks if the following condition is not fulfilled: (III) where Th is a predefined temperature deviation threshold; or —comparing (250) current temperature data (I) of each (k) block with current average temperature data (VI) and considering a fault (OF) on one of said blocks if the following condition is not fulfilled: (V) where ThAV is a predefined average temperature deviation threshold. The invention concerns also a test comprising a shoot-through procedure to identify open circuits in a block.