Feasibility study of electric drives for agricultural tractors and numerical techniques for electric machine design

Today, agriculture industry has a significant impact in global greenhouse gas emissions. A large amount of pollutants come from diesel internal combustion engines, widely used in agricultural machinery. Therefore, emission regulations are becoming tighter worldwide. Since mechanization in agriculture is fundamental to achieve a proper food production for a growing human population, changes are needed in common agriculture engineering to develop new farming machinery that could outperform conventional ones in terms of environmental impact, performance, productivity and safety. Electrification is a feasible solution. A comprehensive review about agricultural machinery electrification is reported, with a particular focus on hybrid electric tractors and their implements. The introduction of electric drives in farming tractors is discussed in detail by looking at the main findings in literature and considering state-of-the-art technology. A methodology to evaluate the economic feasibility of farming tractor electrification is developed. The method is based on an energetic model, input data from field measurements and life cycle cost analysis. A study is conducted on three tractor categories, which differs by power ratings and operating cycles. A parallel hybrid electric architecture is considered, although the approach can be extended to other powertrain configurations. Besides investigations on a system level, also the design of specific components is conducted. Numerical techniques and fast simulation approaches are important for an effective design stage and to reduce R\&D cost and time to market. The potentialities of harmonic balance method are investigated in simulating a basic electric generator front-end for a high-voltage automotive system. The case study comprises a six-pole three-phase surface-mounted permanent magnet generator connected to a six-pulse full-wave diode bridge rectifier. Simulations are performed at fixed generator speed in two operating cases: with a open-circuit DC bus and supplying a load resistance. Both mainstream time stepping and harmonic balance approaches are deeply discussed focusing on the model under study, along with relevant implementation details. Simulation results are commented in the end, together with an evaluation of computational performance. The complete list of publications related to this dissertation is reported at the end.