High-Power Electrical Energy Conversion Systems for Industrial Production with Reduced Environmental Impact

Scientific consensus on anthropogenic climate change calls for drastic emissions reduction. Electrification is the cornerstone of this transition and needs backing by clean energy generation and modern grids. Both aspects rely on large-scale deployment of power converters and energy storage systems since the power quality and stability of traditional power systems are challenged by renewable energy sources’ non-dispatchable nature. Indeed, electrification’s growing energy demand drives a widespread need for high-power converter systems. At generation and distribution levels, converters actively control power flows and integrate storage to ensure power quality and resilience. High-power isolated converters (i.e., solid-state transformers, SSTs), supported by advanced control and communication, will constitute smart grids capable of supplying high power to, e.g., electric vehicles (EVs), datacenters, and high-power industrial loads. The rapid pace of deployment calls for careful attention to all aspects that can catalyze their series production and adoption. In this context, the scope of this research project is to improve power converters in some of their aspects (e.g., efficiency, power density, material use, control performance) for lessening, either directly or indirectly, the environmental impact of the industry and transportation sectors, possibly by catalyzing new applications for an electrified economy. Towards this end, modularity is identified as a key feature, e.g., low-power power electronic building blocks (PEBBs) can be purposely combined to obtain a high-power system, enabling scalability, cost reduction, and increasing availability, with the drawback of increased complexity. Prominent modular high-power converters, isolated and nonisolated, have been studied. In Part I, SSTs are discussed, also focusing on the conversion from medium-voltage AC (MVAC) to low-voltage DC (LVDC) as the most promising applications (e.g., for datacenters and fast EV charging). A modular SST has been investigated as derived from a recent patent that claimed hardware simplification. This work provided the first analyses on this new SST, greatly advancing its modeling, control, and high-level design, also providing a comparative evaluation against another SST and testing with refined simulations. In SSTs, the isolation is provided by high-density transformers operating at increased frequencies that makes their design nontrivial. To contribute on this issue, this thesis studied a high-frequency transformer for a resonant CLLC converter working as a DC solid-state transformer (DCX), experimentally evaluating different winding configurations to explore the trade-off between electrical performance and ease of manufacturing. In Part II, this work focuses on a prominent application for the heavy industry, proposing, motivating, and analyzing the application of the modular multilevel converter (MMC) to accelerate the deployment of next-generation electric arc furnaces (EAFs) for steelmaking with extended modularity than the state-of-the-art. A first feasibility study shows that the novel solution can match the existing one in power density but with improved modularity and scalability. Then, a novel control strategy tailored for this peculiar non-linear load (i.e., the electric arc) is provided and validated through advanced simulations, and a scaled-down prototype has been designed. Several original scientific contributions have already been presented at the most relevant international conferences and have been the result of fruitful collaboration with national and international partners. Ultimately, recognizing both the importance of innovation and industrial adoption, these findings pave the way for future research into SSTs and expanded MMC applications to ensure that power electronics remain at the forefront of the global transition toward cleaner and more resilient energy systems.