Valtchev, S., and J. P. Teixeira,
"The Charging of Hybrid and Electrical Vehicles? Batteries: Contactless Energy Transfer as the key to the future",
2010 International Symposium on Electric Vehicle and 2-nd Annual Conference of Polish Society for Environment Friendly Vehicles, July, 2010.
AbstractWould 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.
Valtchev, S.,
"Contactless Power Transfer",
Seminar of S.Valtchev on Contactless Power Transfer, July, 2008.
AbstractThis seminar was a presentation of S.Valtchev on the methods of wireless energy transfer. The seminar was invited by the colleagues of the Power Processing Laboratory of TU Delft, the Netherlands.
Valtchev, S., and S. Valtchev,
"Control for the Contactless Series Resonant Energy Converter",
Emerging Capabilities and Applications of Wireless Power Transfer: IGI Global, pp. 102–140, 2019.
AbstractThis chapter presents control methods applied in the operation of the series loaded series resonant (SLSR) power converters in a most efficient operation zone. The choice of the control method is affected by the objective to guarantee suitably the efficiency, being this method in the same time, relatively easy to apply. The first part of the chapter compares three basic principles of regulation: frequency mode (FM), pulse width mode (PWM), and their combination (PWM/FM). Finally, a new method for instantaneous regulation is developed. The proposed technique consists of a simplified observation of a state variable value to limit each portion of supplied energy, depending on the requirement for power in each half period. The result of this regulation is comparable to the current mode (CM) control applied to the hard-switching power converters. The viability of this new regulation method is demonstrated by simulations of its analogue circuit implementations and experimentally proved. The circuit is also prepared for the changes in the magnetic coupling (contactless energy transfer).
Valtchev, S., R. Miletiev, R. Arnaoudov, and S. Valtchev,
"Control strategy for efficient operation of super-resonant SLSR (contactless) converters",
XLIV INTERNATIONAL SCIENTIFIC CONFERENCE ON INFORMATION, COMMUNICATION AND ENERGY SYSTEMS AND TECHNOLOGIES (before 1990 was: "Day of the Radio Conference"), pp. 527–530, June, 2009.
Inácio, D., J. A. Inácio, J. Pina, S. Valtchev, M. Neves, J. Martins, and A. Rodrigues,
"Conventional and HTS Disc motor with pole variation control",
2nd International Conference on Power Engineering, Energy and Electrical Drives (POWERENG'2009), pp. 513–518, 2009.
AbstractIn 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.
Valtchev, {S. S. }, and {J. J. } Pamies-Teixeira,
"Culture of the European Student with an Insight to the Future Needs of the Global (European) Labour Market",
Proceedings of the European Politechnical University, vol. 1, no. NA, pp. 78–82, 1, 2012.
AbstractRecent 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