Electric Drives with Permanent Magnet Synchronous Machines Connected toInternal Combustion Engines

In recent years, the increasing cost of oil and Earth global warming due to greenhouse gases have pushed the scientific research, the governments and thus the markets in the direction of a higher efficiency of the systems in order to reduce the use of this fuel and therefore its associated emissions of CO2. Nowadays, the most involved sectors of this technological revolution are the fields of electricity generation and the transportation. In fact, these two sectors are the main accountable of CO2 global emission, that are associated for about 45% to electricity generation and for about 30% to transport. Moreover, it should be noted that although the oil is not a renewable energy source, currently about 40% of the production world energy depends on oil and the level of dependence rises to about 80% in the transportation sector where the majority of vehicles is powered by an engine fueled by oil derivatives. For these reasons, the scientific research in the last decade was focusing on these issues in particular in emerging fields such as distributed cogeneration and hybrid electric vehicles. In particular, new systems of distributed energy are studied, which are capable to increase the energy efficiency of the plant because the electrical and thermal energy are produced in combined way and directly in the site where they are required. In this way the losses of the network can be reduced. Instead, in the field of hybrid electric vehicles the use of the electric machine can help to increase the efficiency of the power-train in the various working points. These hybrid systems allow to reduce up to 30% the fuel consumption and associated emissions compared to a conventional vehicle. With this historical context this thesis is focused in the study of a power-train structure of domestic cogeneration system or a vehicle, namely the analysis of a system composed by an internal combustion engine directly connected to an electric machine. The two principal tasks of the electric machine are: startup of the internal combustion engine and generate on electric energy. In the case of a hybrid electric vehicle, in addition to those listed above, there are other two operation modes that are: increase the engine torque during the acceleration and recovering the energy during braking phase. Among the various types of electrical machines existing in the market, the permanent magnet synchronous machines take up an important position in the cogeneration and hybrid vehicle fields. In fact, this kind of electric machine allows to obtain: a high performance, high torque density, high overload capacity, a good robust construction, compact volume, and therefore low weight. Furthermore this type of electric machine can work at variable speeds and operate as motor and as generator with comparable performance. For this reason in this Ph.D. thesis the electrical drives composed by an internal combustion engines direct connected to permanent magnet synchronous electric machines will be presented. The author’s doctoral thesis has been carried out at the Electric Drive Laboratory of University of Padova, which since more than twenty years is active in the design of electrical machines and their control through research projects with industrial partners and scientific publications in journals and in international conferences. Therefore, although in the literature there are several books discussing an electric drives, thanks to the experience acquired in this laboratory the author intention is to emphasize with greater detail the aspects and basic notions which in his opinion are fundamental to the design of on electric drive devoted to the applications subject of this work. In addition, in the opinion of the author, unlike a paper on journal or conference the doctoral thesis should be reasonably self-contained and should be understandable even by a non expert of this field of research; therefore also basic aspects of an electric drive and its control have been reported with detail. So the work reported in this thesis is essentially composed by two parts, the first part is made up by the first four Chapters and the second one is composed by the last two Chapters. In the first part of Ph.D. thesis the basic aspects, that are required for a good knowledge on the electric drives field, have been reported. In particular the design aspects and fundamental characteristics of electric machine control, operating limits of a permanent magnet synchronous machine, and power converter have been pointed out. The second part of Ph.D. thesis is focused on the design aspects of electric drive for a domestic cogeneration system and for hybrid electric motorcycle. In particular for CHP system some effective techniques, that can help to reduce the vibration and noise problems due to the internal combustion engine, have been described. In the field of hybrid electric motorcycle the main design choices carried out in order to achieve a hybrid electric motorcycle prototype with good performance are reported.