Stanimir Valtchev

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Would it be necessary to charge rapidly the electric vehicle (EV) and hybrid electric vehicle (HEV)? It is not easy to answer without a thorough look at the capability of the modern propulsion battery and the power necessities of the EV and HEV. The different possible solutions are compared and maximum speed of charging is analysed. The wired connection for charging is compared to the wireless energy transfer and because of the limitations imposed by the modern and future batteries, the contactless energy transfer is chosen as the future charging method.

The proposed regulation strategy consists in obtaining at the right time the correct information about the energy contained in the resonant tank. This information allows a stable operation of the switches and a higher efficiency of any Series Loaded Series Resonant (SLSR) power converter, especially when contactless energy transfer is concerned. The strategy is based on guaranteeing the correct portion of energy transported by the resonant tank to the load. The portion has to vary corresponding to the error signal taken from the output voltage and remains unchanged if the error signal is at its minimum. In a certain way this method is similar to the Current Mode Control of the classical power converters. The viability of the idea is demonstrated by simulation of a realistic analogue circuit (on preparation for a digital implementation in the near future).

Recent issues of global heating and energy shortages are imposing a need to change our paradigm around transportation. Somehow, electric vehicles are progressively standing as a strong and necessary alternative for the society. Technically and technologically the acceptance of the EV is easier now than ever but the psychology of the consumers and the running business of internal combustion vehicles, the whole existing infrastructure are too much conservative to be changed easily. The changes in technology require changes in the engineering society and its human resources. The objective of this paper is to give a contribution to the discussion and reflection of potential future scenarios where EV?HEV?s are spread across the society. It gives an overview of the range of knowledge and competences necessary for a sustainable and streamlined development of those. In fact, it is expected that a new kind of professional profiles need to be created or developed to supply the work market with the right human resources. The paper provides some discussion on the creation of new profiles or adaption of existing ones. Among different possible scenarios the creation of post-graduation courses for students holding undergraduate profiles in the fields referred to earlier would be an interesting and viable solution for fast response. The post graduation would be focused in specific key areas of the EV?HEV. Several factors are pointed out to endorse this scenario

The electromagnetic resonance became irreplaceable tool for wirelessly transfer energy and information. Since long this effect is widely used in communications but recently it is deeply studied and applied at the contactless transfer of energy. The electric?hybrid car battery charging is an urgent need and the knowledge about the resonant contactless transfer became very important. The study of the Series Loaded Series Resonant converter shows it as well suitable for the contactless energy transfer. The idealized Series Resonant Power Converter is used as a base for defining the best (most efficient) modes of operation. Based on the magnetic parameters of the loosely coupled transformer (magnetic link), the characteristics of the contactless power converter are described in approximated form, thus permitting an easier and faster calculation of the converter variables. This is used for instantaneous control of the converter, free from previously known defects.

This dissertation tries to track the route of power production from photovoltaic sources. A worldwide look into the photovoltaic solar power production is given. The theory behind the PV cell and its application in PV power modules is presented. The DC ? DC power converters usually associated with solar PV panels are showed. The main maximum power point tracking (MPPT) algorithms are also showed. A solar PV system was dimensioned using the theoretical models and the solar PV modules (BS ? 40) available at the Departamento de Engenharia Electrotécnica (DEE). This system was used as a reference for designing a simulator implemented in MatLab?Simulink. This simulator includes all the components needed to test the different MPP tracking algorithms. Those components are: A PV solar module, which can be associated with others to form a solar panel; A Flyback DC ? DC power converter and a classic perturb and observe (P&O) tracking algorithm. A solar power meter that gives values in W?m2 was built in order to validate simulation values of the solar PV modules. Measuring the solar module characteristics (tension ? current) and knowing the solar irradiation at that given time it is possible to check if the simulated values and the measured ones agree. With the data collected in the simulation a new MPP tracking algorithm was presented. This is based in the classic P&O algorithm, but using modules that try to overcome the local maxima problem. It also tries to minimize the control oscillations in the converter?inverter, this is done in order to minimize losses and to maximize power production.

Would it be necessary to charge rapidly the electric vehicle (EV) and hybrid electric vehicle (HEV)? It is not easy to answer without a thorough look at the capability of the modern propulsion battery and the power necessities of the EV and HEV. The different possible solutions are compared and maximum speed of charging is analysed. The wired connection for charging is compared to the wireless energy transfer and because of the limitations imposed by the modern and future batteries, the contactless energy transfer is chosen as the future charging method.

Recent issues of global heating and energy shortages are imposing a need to change our paradigm around transportation. Somehow, electric vehicles are progressively standing as a strong and necessary alternative for the society. Technically and technologically the acceptance of the EV is easier now than ever but the psychology of the consumers and the running business of internal combustion vehicles, the whole existing infrastructure are too much conservative to be changed easily. The changes in technology require changes in the engineering society and its human resources. The objective of this paper is to give a contribution to the discussion and reflection of potential future scenarios where EV/HEV‘s are spread across the society. It gives an overview of the range of knowledge and competences necessary for a sustainable and streamlined development of those. In fact, it is expected that a new kind of professional profiles need to be created or developed to supply the work market with the right human resources. The paper provides some discussion on the creation of new profiles or adaption of existing ones. Among different possible scenarios the creation of post-graduation courses for students holding undergraduate profiles in the fields referred to earlier would be an interesting and viable solution for fast response. The post graduation would be focused in specific key areas of the EV/HEV. Several factors are pointed out to endorse this scenario

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The electromagnetic resonance became irreplaceable tool for wirelessly transfer energy and information. Since long this effect is widely used in communications but recently it is deeply studied and applied at the contactless transfer of energy. The electric/hybrid car battery charging is an urgent need and the knowledge about the resonant contactless transfer became very important. The study of the Series Loaded Series Resonant converter shows it as well suitable for the contactless energy transfer. The idealized Series Resonant Power Converter is used as a base for defining the best (most efficient) modes of operation. Based on the magnetic parameters of the loosely coupled transformer (magnetic link), the characteristics of the contactless power converter are described in approximated form, thus permitting an easier and faster calculation of the converter variables. This is used for instantaneous control of the converter, free from previously known defects.

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This was a cooperation with Electric Power Processing laboratory of TU Delft. During this stay organized and financed by TU Delft, S.Valtchev supported by teaching some students, PhD students and post-doc associates (in workshops?seminars).

Os motores passo a passo podem ser vistos como motores eléctricos sem comutação electromecânica (escovas e anéis). Tipicamente, todos os enrolamentos no motor são parte do estator, e o rotor ou é um magneto permanente ou, no caso dos motores de relutância variável, um bloco dentado de algum material ferro-magnético macio. Toda a comutação deve ser lidada externamente pelo controlador do motor, e normalmente, os motores e os controladores são dimensionados de modo que o motor possa ser posicionado numa posição fixa, assim como rodar em ambos os sentidos. Os motores passo a passo podem ser usados em sistemas de controlo em malha aberta; estes são geralmente adequados para sistemas que operam em baixas acelerações com cargas fixas, mas o controlo em malha fechada pode ser essencial para acelerações elevadas, particularmente se envolverem cargas variáveis. Se um motor de passo num sistema de controlo em malha aberta sofre um binário demasiado grande, todo o conhecimento da posição do rotor será perdido e o sistema deverá ser reiniciado. Nesta dissertação, é proposto um novo conversor elétrico em malha aberta, especialmente dimensionado para motores de pequenas dimensões e de alto binário, alimentados com correntes unidirecionais. Este conversor é baseado na mudança do declive de subida da corrente em cada enrolamento, através da descarga de um condensador adicional carregado.

A new faster control method is presented, inattempt to achieve stable operation and higher efficiency of anySeries Loaded Series Resonant (SLSR) power converter, andespecially when the application requires contactless energytransfer. This instantaneously reacting control method is basedon calculated individual energy portions delivered to theresonant circuit. Its viability is demonstrated by simulation of ananalogue circuit implementation.

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In this paper, a poly-phase disc motor innovative feeding and control strategy, based on a variable poles approach, and its application to a high temperature superconductor (HTS) disc motor, are presented. The stator windings may be electronically commutated to implement a 2, 4, 6 or 8 poles winding, thus changing the motor's torque?speed characteristics. The motor may be a conventional induction motor with a conductive disc rotor, or a new HTS disc motor, with conventional copper windings at its two iron semi-stators and a HTS disc as a rotor. The conventional induction motor's operation principle is related with the induced electromotive forces in the conductive rotor. Its behaviour, characteristics and modelling through Steinmetz and others theories are well known. The operation principle of the motor with HTS rotor, however, is rather different and is related with vortices' dynamics and pinning characteristics; this is a much more complex process than induction, and its modelling is quite complicated. In this paper, the operation was simulated through finite-elements commercial software (FLUX2D), whereas superconductivity was simulated by the E-J power law. The electromechanical performance of both motor's computed are compared. Considerations about the systems overall efficiency, including cryogenics, are also discussed.