Ievgen Verbytskyi

Spectrum calculation of frequency pulse modulation voltage using double Fourier series

The features of using double Fourier series for calculation spectrum of pulse-width modulated (PWM) signals are described. Restriction of implementation double Fourier series for signal with other type of modulation are indicated and approach for signals with arbitrary modulation on basis double Fourier series are proposed. The example of spectrum calculation of pulse-frequency signal (PFM) is demonstrated. Numerical check of calculation are performed.

Control features of multicell-type current regulator for resistance welding

The features of resistance welding process are considered. A multiceli buck converter as a simplest, efficient and stable topology for resistance welding power supply is proposed. The efficiency of a buck converter cell is analyzed. The particularities of welding pulse generation are described. Relay control as an appropriate method for minimizing the welding pulse curve error is analyzed. The restrictions of relay method use for multiceli converter topology are shown. A modified strategy to reduce the error of welding pulse generation by multiceli converter is proposed. The theoretical aspects of the converter design are verified with MATLAB Simulink.

Features of compensation of a reactive power at the transient mode

The problem of reactive power compensation in power grids with variable load is analyzed. An inefficient implementation of existing methods of reactive power compensation for this case is shown. The method of analysis of the transmitting energy between the source and the load during the transition process based on the theory of instantaneous power is proposed. The efficiency of energy transfer from source to load based on the instantaneous value of power factor, which is calculated on the basis of the measured values of grid current and voltage is proposed. The proposed method realization on the example of the linear circuit of the first order is shown. The principles of reactive power compensation in transient mode is given.

Multicell-type current regulator based on Cuk converter for resistance welding

Resistance welding technology features are discussed. The ways of improving the efficiency of the system, which consists of energy storage unit, current regulator and welding load, are analyzed. A multiceli structure of the output current regulator with a cell topology based on Cuk converter is suggested. The maximal inductance values of input and output inductors are calculated. Cuk converter efficiency is estimated using its mathematical model. Theoretical considerations are proved with developed Simulink model of current regulator.

A Problem of a Displacement Calculation of Tissue Surface in Non-Contact Photoacoustic Tomography

Background. Photoacoustic tomography (PAT) is a relatively new imaging modality,which allows e.g. visualizing the vascular network in biological tissue noninvasively. This tomographic method has an advantage in comparison to pure optical/acoustical methods due to high optical contrast and low acoustic scattering in deep tissue. The common PAT methodology, based on measurements of the acoustic pressure by piezoelectric sensors placed on the tissue surface, limits its practical versatility. A novel, completely non-contact and full-field PAT system is described. In noncontact PAT the measurement of surface displacement induced by the acoustic pressure at the tissue/air border is researched. Objective. To solve a simulation problem of the displacement calculation based on the medium pressure, which consists in deriving a formula for recalculating the pressure in the surface displacement based on the momentum conservation law, developing a simulation technique, and comparing the error of the proposed technique with the earlier used one. Methods. Comparing the experimental data with simulated pressure data in the k-Wave toolbox. The criterion of comparison is the relative quadratic error. Results. The simulation results of the displacement based on a new approach are more consistent with the experimental data than previous. The quadratic error numerical value of the new approach is 18 % and the previous is 71 %. Conclusions. The theoretical features of the surface displacement simulation are investigated and the solution of this problem is proposed based on momentum conservation law. The implementation of the proposed methodology has a four times smaller simulation error compared to the previous technique, so it can be implemented in the non-contact PAT. The residual error can be caused by the properties of the tissue, which are not taken into account in the model, which requires further research.

Nonlinear Bang–Bang Eigenproblems and Optimization of Resonances in Layered Cavities

We study optimization of quasi-normal-eigenvalues

Power grid converter control improvement based on contextual data

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Контекстний підхід керування системою електроживлення

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