Incorporating Components’ Mean Time To Failure in the Design of a New Family of Reliable and Fault-Tolerant Multilevel Inverters
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Authors
Akbari, Amirhosein
Date
2024-10-04
Type
thesis
Language
eng
Keyword
Multievel , Inverter , Reliability , Fault-tolerant , Structure , MTTF
Alternative Title
Abstract
Renewable energy systems, particularly photovoltaic systems, increasingly use multilevel inverters due to their lower voltage stress on switches, reduced harmonic components at the output, and higher efficiency than traditional two-level converters. However, the high number of switching devices in these structures leads to higher power losses, costs, and more complex control systems. Moreover, it negatively affects the reliability of the inverter, more specifically its mean time to failure (MTTF), which is a vital factor in determining life expectancy. Therefore, it is essential to accurately evaluate the reliability of power electronic converters to address the company’s investment during manufacturing, to plan at a system level, and to implement effective operating and maintenance strategies.
This thesis first introduces a new multisource inverter structure that can generate eleven voltage levels using three DC sources or seven voltage levels using one DC source and two flying capacitors. The proposed structure offers higher reliability compared to other multisource inverter structures. A further reduction in the number of conducting devices results in higher reliability and efficiency. Therefore, the next part of this thesis proposes a five-level inverter structure utilizing only two conducting devices for each voltage level, resulting in a higher MTTF and reduced losses compared to state-of-the-art competitors. To accurately calculate the MTTF of an inverter, this thesis introduces a novel analytical method based on an evaluation of the failure rate of its switches.
The improvement of MTTF directly contributes to an increase in inverter reliability. Moreover, a fault-tolerant structure extends the MTTF even further. Correspondingly, the final part of this thesis proposes a five-level fault-tolerant inverter structure that can handle both open-circuit and short-circuit faults across single- and multi-switches. The proposed inverter maintains rated output power and efficiency under both healthy and faulty operations. A comprehensive evaluation of the proposed inverter is conducted in terms of quantitative aspects, efficiency, and cost, as well as a comprehensive assessment of its reliability in comparison with other fault-tolerant structures.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.