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PhD defence by Brwene Salah Abdelkarim Gadalla on Lifetime Prediction of the Boost, Z-source and Y-source Converters in a Fuel Cell Hybrid Electric Vehicle Application


22.08.2017 kl. 13.00 - 16.00


Brwene Salah Abdelkarim Gadalla, Department of Energy Technology, will defend the thesis "Lifetime Prediction of the Boost, Z-source and Y-source Converters in a Fuel Cell Hybrid Electric Vehicle Application".


Lifetime Prediction of the Boost, Z-source and Y-source Converters in a Fuel Cell Hybrid Electric Vehicle Application


Brwene Salah Abdelkarim Gadalla


Associate Professor Erik Schaltz


Associate Professor Tamas Kerekes 


Associate Professor Weihao Hu, Dept. of Energy Technology, Aalborg University (Chairman)
Leading Researcher Dmitri Vinnikov, Tallinn University of Technology, Estonia
Professor Li Ran, School of Engineering, University of Warwick, UK


Reliability is one of the most important issues in the field of power electronics components and systems. In most of the electro-mobility applications, e.g. electric and hybrid electric vehicles, power electronic are commonly used in very harsh environment. Temperature variations, thermal cycles, power cycles, vibration and other stresses affecting the device may cause unreliable system. Thus, designing reliable power electronic components is important for the aim of reducing the energy losses, maintenance cost and extending the service lifetime as well. Research within power electronics is of high interest as it has a huge impact in the industry of the electro-mobility applications. Boost converters are essentially needed in many applications such as electro-mobility, fuel cell, and renewable energy applications that require the output voltage to be higher than the input voltage. Recently, boost type converters have been attracted by the industrial applications, and hence it has become an extremely hot topic of research. Many researchers proposed the impedance source converters with their unique advantages as having a high voltage gain in a small range of duty cycle ratio. However, the thermal behavior of the semiconductor devices and passive elements in the impedance source converter is an important issue from a reliability point of view and has not been investigated yet. Therefore, a loss distribution comparison between three different types (Conventional boost, Z-source and Y-source) of the boost converters has been analyzed for a wide voltage and power range. The Y-source converter has been selected for validating the influence of heat loss generated from the devices. A simulation model is developed and verified experimentally rated at 300 W.

Fuel cells are a very promising source of energy since they are pollution free, producing only electricity, water, and heat. It has been a significant force in the development of technology over the past 30 years, and is drawing an increasing attention towards the technology today. Fuel cells have been applied to DC/DC converters where the reliability and lifetime are of high priority performance factors. A lifetime prediction model is applied for the power semiconductors, which are used in the fuel cell DC/DC converters. The common used Coffin- Manson lifetime model and Semikron lifetime model for the IGBTs solder and bond wire fatigues are considered and compared in the three DC/DC converters. In order to estimate the lifetime of the converters, a mission profile is taken into account to estimate the impact of the IGBTs junction temperature thus the lifetime during the steady state operation. In addition to the thermal stresses generated due to the power losses during the converter operation, a case study of Artemis motorway mission profile is considered in this analysis. Lifetime consumption and the expected number of years before failure is presented and compared for the Boost, Z-source and Y-source converters. The lifetime estimation results shows that the Z-source converter has a longer lifetime compared with the conventional boost and Y-source converter, due to lowest maximum junction temperature profile of the Z-source converter. Nevertheless, each converter is designed separately according to its current and voltage stresses of the power device, where both the Z-source and Y-source converters have the IGBT modules with the same power rating.

This Ph.D. thesis starts with the state of the art of the reliability of power electronics in the electro-mobility applications, and the FCHEV system configuration. The design, parameter selection, and basic theory of operation of the boost (conventional, Z-source and Y-source) power converters are discussed in Chapter 2. In Chapter 3 the loss modelling and temperature modelling is given at different power loading. Chapter 4 analyze the three compared converters at different voltage and power levels, and validate the loss modelling of the Y-source converter based on the temperature modelling. The reliability assessment for the fuel cell compared converters is given in Chapter 5, where the lifetime modelling, failures mechanisms, and the number of estimated lifetime years of the converters are presented based on the assessment of only one component which is the IGBT power module. Finally, in Chapter 6 the conclusions, main contributions, and future work are given to give full overview of this Ph.D. project.


PhD defence by Brwene Salah Abdelkarim Gadalla on Lifetime Prediction of the Boost, Z-source and Y-source Converters in a Fuel Cell Hybrid Electric Vehicle Application





Department of Energy Technology


Pontoppidanstræde 111, auditorium

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