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Title: Power module condition monitoring for offshore wind applications with focus on the die attach degradation
Author: Konaklieva, Syliva
ISNI:       0000 0004 7657 7551
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2017
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This thesis documents the research for a field-deployable on-line condition monitoring method which can be applied to the IGBT modules inside power electronic converters in offshore wind turbines. The main focus is on determining the health condition of the module packaging and on finding a viable means for tracking its gradual in-service degradation. Of the two main packaging degradation mechanisms - solder fatigue and bond-wire lift off - greater attention is paid to the former, although the researched condition monitoring method may also allow the detection of the latter. The signature considered here as most indicative of module degradation is the increase of its internal power loss for the same electrical operating point (defined by current level, power factor, switching frequency, etc.). Power loss and junction temperature affect each other in a circular fashion, progressively increasing, especially when the heat flow path to the outside cooling system is compromised by increasing levels of solder fatigue. The method explored here for assessing the device power losses in operation relies on external case and heat sink temperature signals and the novel use of ANNs in place of a thermal model. Although the explored concept is not yet ready for industrial use, it shows potential for further development. Power loss modelling with thermal feed-back is undertaken to develop a better understanding of the devices' operation. Special focus is paid to the current sharing and temperature profiles of paralleled chips inside the same packaging experiencing different degradation levels. High resolution scans of the die-attach solder layer of power cycled modules are also performed to gain understanding of their degradation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TA Engineering (General). Civil engineering (General) ; TK Electrical engineering. Electronics Nuclear engineering