Contributions to the characterization and design optimization of power converters based on switching-cell arrays

(English) The search for standardization in power converter design is motivated by the potential of a significant decrease in design time, a significant decrease in converter cost, and an increase in converter performance features. A systematic design process of power converters employing standard components is to be found. One recent approach to reach this goal consists of the design of power converters based on the so-called switching-cell arrays (SCAs). An SCA is a matrix arrangement of highly optimized switching cells (SCs) that can be interconnected in different ways to implement active neutral-point-clamped converter legs with different voltage and current ratings. These legs can then be used to implement the complete switching block of power converters. Each SC is composed of an active switch with an antiparallel diode controlled by a self-powered gate driver. The design process of power converter legs based on SCAs offers several degrees of freedom and advantages, and a thorough exploration of the potential of this new promising approach remains a pending issue. The general purpose of this thesis is to explore the potential of the power converter design based on SCAs built upon a limited number of different SCs. This research is focused on the search for the optimal diversity of SCs, SCAs configurations, and switching strategies to implement optimized SCA-based power converter legs considering efficiency, reliability, and simplicity. To be able to compare different possible designs of SCA-based power converter legs, firstly, an appropriate steady-state average thermo-electrical model is derived to allow estimating the losses and temperature of all power semiconductor devices within the converter leg. The effectiveness and accuracy of this model in capturing the main performance features of the system are verified through analytical and experimental comparisons. Secondly, to further extend the performance analysis, a fast reliability assessment of neutral-point-clamped topologies through Markov models is developed. Model assumptions are verified through experimental tests. Besides, the reliability comparison of different converter leg configurations based on the proposed model is presented. Then, employing the proposed thermo-electrical and reliability models, the thermal and reliability benefits of configuring the power semiconductor block of power converters with several small standard power semiconductor devices instead of a few larger ones at a