Design of a surface permanent magnet synchronous machine with external rotor for variable speed screw turbines

In an attempt to mitigate CO2 emissions and combat climate change, the role of green energy generation systems has become increasingly critical. Hydropower, one of the oldest and most environmentally friendly methods of generating electricity, remains a cornerstone of renewable energy solutions. This thesis delves into the realm of small hydropower plants, examining their diverse technologies with a particular emphasis on the innovative use of screw turbines. These systems are not only sustainable but also adaptable to a variety of environmental conditions and geographical settings. This thesis introduces an innovative approach to the design of small hydropower screw turbines, specifically focusing on the integration between screw turbines and electric generators to enhance plant efficiency and reduce maintenance requirement. The core of this study focuses on the integration of screw turbines with electric generators, specifically Surface Permanent Magnet (SPM) synchronous machines. SPM machines are renowned for their high efficiency and robust performance, making them ideal for small-scale hydropower applications. We explore the design intricacies of these electric generators, detailing the processes and engineering principles that underpin their construction. By leveraging advanced magnetic materials and cutting-edge design techniques, we aim to enhance the performance and reliability of these generators. Control systems play a crucial role in the efficient operation of SPM generators. This thesis investigates various power electronics control strategies, with a spotlight on the field-oriented control (FOC) method. FOC is celebrated for its precision and effectiveness in managing the torque and speed of electric machines. We provide a comprehensive analysis of its implementation, highlighting its advantages in optimizing the performance of SPM generators in hydropower systems. A detailed cost estimation is conducted, reflecting the economic aspects of SPM generator deployment within the Italian market context of 2023. This analysis includes a breakdown of material costs, manufacturing expenses, and market trends, providing a holistic view of the financial viability of small hydropower projects. Furthermore, we address one of the significant challenges in SPM machine operation: eddy current losses. These losses can significantly impact on the efficiency and longevity of electric generators. Our research proposes an innovative approach to reduce eddy current losses by altering the winding configurations without changing the machine geometry. This method promises to enhance efficiency and reduce operational costs, contributing to the overall sustainability and effectiveness of small hydropower plants. In conclusion, this thesis not only advances the understanding of SPM generators in small hydropower applications but also introduces novel solutions to enhance their performance and economic feasibility. By bridging the gap between traditional hydropower techniques and modern engineering innovations, this work paves the way for more efficient, reliable, and eco-friendly energy generation systems.