Zoltan Vizvari

This paper presents a comprehensive analysis of the dead-time effects in wireless power transfer systems based on LCC-S topology. In these systems operating at high frequencies, the ratio of dead-time versus the operating period becomes critical, and the dead-time issue can cause certain problems regarding power quality, efficiency, and output voltage ripple. The impact of input quantities such as voltage and switching frequency on the efficiency and output power of the LCC-S-tuned WPT system was also investigated. The optimal combination of these parameters used to achieve the maximum efficiency for a target output power and to set the appropriate value of the dead time were determined by running multiple simulations using the MATLAB R2023b software platform. It was also shown that the output voltage remained unchanged with and without a load and up to 1200 ns of dead-time, which provides a simple implementation of the corresponding mathematical model. In the recommended interval of 600–1500 ns, the influence of the dead-time on the value of the output voltage amplitude is less than 10%. The validity of the proposed method was confirmed through the implementation of the experimental prototype, a 5 kW wireless power transmission system, and the obtained results were in accordance with the simulation results.

The inverse conductivity problem in electrical impedance tomography involves the solving of a nonlinear and under-determined system of equations. This paper presents a new approach, which leads to a quadratic and overdetermined system of equations. The aim of the paper is to establish new research directions in handling of the inverse conductivity problem. The basis of the proposed method is that the material, which can be considered as an isotropic continuum, is modeled as a linear network with concentrated parameters. The weights of the obtained graph represent the properties of the discretized continuum. Further, the application of the developed procedure allows for the dielectric constant to be used in the multi-frequency approach, as a result of which the optimized system of equations always remains overdetermined. Through case studies, the efficacy of the reconstruction method by changing the mesh resolution applied for discretizing is presented and evaluated. The presented results show, that, due to the application of discrete, symmetric mathematical structures, the new approach even at coarse mesh resolution is capable of localizing the inhomogeneities of the material.