Electrotechnical faculty

A proof-of-concept prototype of a heterogeneous catalytic reactor has been developed for continuous production of hydrogen via formic acid (FA) dehydrogenation. A laboratory-type polymer electrolyte fuel cell (PEFC) fed with the resulting reformate gas stream (H2 + CO2) was applied to convert chemical energy to electricity. To implement an efficient coupling of the reactor and PEFC, research efforts in interrelated areas were undertaken: (1) solid catalyst development and testing for H2 production; (2) computer modeling of heat and mass transfer to optimize the reactor design; (3) study of compatibility of the reformate gas fuel (H2 + CO2) with a PEFC; and (4) elimination of carbon monoxide impurities via preferential oxidation (PROX). During the catalyst development, immobilization of the ruthenium(II)–meta-trisulfonated triphenylphosphine, Ru-mTPPTS, catalyst on different supports was performed, and this complex, supported on phosphinated polystyrene beads, demonstrated the best results. A validated mathematical model of the catalytic reactor with coupled heat transfer, fluid flow, and chemical reactions was proposed for catalyst bed and reactor design. Measured reactor operating data and characteristics were used to refine modeling parameters. In turn, catalyst bed and reactor geometry were optimized during an iterative adaptation of the reactor and model parameters. PEFC operating conditions and fuel gas treatment/purification were optimized to provide the best PEFC efficiency and lifetime. The low CO concentration (below 5 ppm) in the reformate was ensured by a preferential oxidation (PROX) stage. Stable performance of a 100 W PEFC coupled with the developed reactor prototype was successfully demonstrated.

Optical losses in a photoelectrochemical (PEC) cell account for a substantial part of solar-to-hydrogen conversion losses, but limited attention is paid to the detailed investigation of optical losses in PEC cells. In this work, an optical model of combined coherent and incoherent light propagation in all layers of the PEC cell based on spectroscopic measurements is presented. Specifically, photoelectrodes using transparent conductive substrates such as F:SnO 2 coated with thin absorber films are focused. The optical model is verified for hematite photoanodes fabricated by atomic layer deposition and successfully used to determine wavelength-dependent reflection, transmission, layer absorptances, and charge generation rates. Furthermore, the calculated absorptances enable 20-30% more accurate calculations of the absorbed photon-to-current efficiency of PEC cells. Our optical model is a powerful tool for the optimization of the optical performance of PEC cells focusing on single absorber or tandem configurations and represents a cornerstone of a complete (optical and electrical) model for PEC water splitting cells.

Stredná priemyselná škola dopravná, Sokolská 911/94, 960 01 Zvolen Kód ITMS projektu: 26110130667 Názov projektu: Zvyšovanie flexibility absolventov v oblasti dopravy "Moderné vzdelávanie pre vedomostnú spoločnosť/Projekt je spolufinancovaný zo zdrojov EÚ" UČEBNÉ TEXTY Vzdelávacia oblasť: Moderné vzdelávanie pre vedomostnú spoločnosť Predmet: Meranie a diagnostika Ročník, triedy: Tretí, triedy III.B, III.C Tematický celok: Meranie snímačov a akčných členov Vypracoval: Ing. A. Španiel Dátum: 2014-2015

This paper deals with mathematical modelling of impulse waveforms and impulse switching functions used in electrical engineering. Impulse switching functions are later investigated using direct and inverse z-transformation. The results make possible to present those functions as infinite series expressed in pure numerical, exponential or trigonometric forms. The main advantage of used approach is the possibility to calculate investigated variables directly in any instant of time; dynamic state can be solved with the step of sequences (T/6, T/12) that means very fast. Theoretically derived waveforms are compared with simulation worked-out results as well as results of circuit emulator LT spice which are given in the paper.

The paper deals with modeling and simulation of chosen operational modes of HEV vehicle with direct AC/AC transfer and five-phase IM traction motors. Such configuration yields smaller voltage drops com-pared with the serial AC/DC/AC converter and five-phase machines offer some inherent advantages over their three-phase counterparts. The advantages include reduced electromagnetic torque pulsation and also noise characteristics of the five-phase drives are better when compared with the three-phase ones. Charging and braking regimes were chosen as possible operational modes for modeling and analyses. The result of the simulation. carried out with using of Matlab/Simulink are given in the paper.

Artykuł dotyczy uproszczonej konfiguracji pojazdów hybrydowych HEV. Uproszczenie polega na zmniejszeniu konwertera 4QC wymaganego w trybach hybrydowych. Poza tym tryb pracy w trybie autonomicznej trakcji w trybie akumulatorowym wykorzystuje bezpośrednią konfigurację 0x5 trakcyjnego konwertera macierzy 3x5 McX. Taka konfiguracja może być uzyskana z tego głównego konwertera trakcyjnego. Głównymi zaletami uproszczonego połączenia jest mniejsza wielkość konwertera 4QC - możliwa nieco lepsza wydajność układu napędowego HEV. Dostępne są tryby pracy, modelowanie i układ napędowy układu napędowego skoncentrowany na rozruchu i napędzie trakcyjnym HEV napędzanego przez ICE, rozruch ICE zasilany akumulatorem AB z wykorzystaniem SG jako rozrusznika i napęd trakcyjny zasilany przez AB accu - bateria i hamowanie silnika trakcyjnego, które przenosi energię do akumulatora AB. Wyniki wszystkich eksperymentów symulacyjnych podano w pracy.

Paper deals with analysis and mathematical modelling of pulse-width-modulated impulse rectangular signals in Z-domain. These signals are widely used electrical engineering application both in signal processing also in power electronic systems. Presented approach uses direct-and inverse z-transformation for pulse-width-modulated impulse waveforms description. The main advantage of this description is that step or period of the calculation can be equal to carrier signal period, and the calculation is possible to provide directly at any step of impulse series. Theoretically derived waveforms are compared with simulation worked-out results.

This paper dals with design of optimized electronic control for diesel engines for all-terrain vehicles. In paper the detailed proposal of control algorithm, as well as procedure for turbocharger innovation is described. Designed optimization algorithm is verified on real Land Rover Defender vehicle. In last part of paper, the measurements on electrodynamic dynamometer are discussed.

The paper deals with analysis and modelling of a new type of single-phase supplied AC/AC converter with two phase outputs. It consists of one-leg half-bridge matrix converter loaded by the resistive-inductive load in series connection. As harmonic analysis of the voltage of both phases gives very high value of total harmonic distortion (roughly 86 %) the current waveforms should be improved by using of serial L-C filter-which brings much lesser value acceptable for application. The simulation is resulting in a recommendation for the fair and right design of the converter, and demands to single-or two-phase input supply voltage, respectively, under passive R-L or motoric load.

The paper deals with a novel enhanced connection of AC/AC powertrain for Hybrid Electric Vehicles (HEV). The substantial contribution of such a connection is the absence of 4QC auxiliary converter needed for autonomous and hybrid operational modes and its compensation by power-lesser 0×5 matrix converter. The main advantages of a simplified connection are, beside smaller auxiliary converter sizing, also possible better efficiency of the HEV powertrain. So, powertrain operation in autonomous traction accu-battery modes uses direct 0×5 configuration of traction 3×5 M×C matrix converter, and in hybrid modes of Internal Combustion Engine (ICE) and accu-battery uses besides traction 3×5 M×C matrix converter the auxiliary 0×5 matrix converter. Modeling and simulation using Matlab-Simulink environment of traction powertrain configuration in autonomous modes are presented in the paper as well as all simulation experiment results.

The paper deals with testing device designed for experimental examination of processes in power electronics devices during various switching modes is described. Through the use of auxiliary circuits additional switching modes (ZVS, ZCS) are realized except hard switching, and turning-off with reduced current respectively. The device´s advantage is possibility of fine dead time setting, allowing us analyzing the effects of phenomenon noted above, on measurements of commutation losses.

Paper deals with mathematical modelling of impulse waveforms and impulse switching functions used in electrical engineering. Impulse rectangular waveforms are created by periodical trigonometric functions with modulo π, so, the waveforms are discontinuous and strongly non-harmonic ones. Impulse switching functions are investigated using direct-and inverse z-transformation. The results make it possible to present those functions as infinite series expressed in pure numerical-, exponential-or trigonometric forms. Theoretical derived waveforms are compared with simulation worked-out results.

This paper is dedicated to the recent unprecedented boom of SiC electronic technology. The contribution deals with brief survey of those properties. In particular, the differences (both good and bad) between SiC electronics technology and well-known silicon VLSI technology are highlighted. Projected performance benefits of SiC electronics are given for several large-scale applications on the end of the contribution. The basic properties of SiC material have been discussed already on the beginning of 80’s, also at our university.

The paper deals with testing device designed for experimental examination of processes in power electronics devices during various switching modes is described. Through the use of auxiliary circuits additional switching modes (ZVS, ZCS) are realized except hard switching, and turning-off with reduced current respectively. The device ́s advantage is possibility of fine dead time setting, allowing us analyzing the effects of phenomenon noted above, on measurements of commutation losses.

The paper deals with Euler'sand Taylor's expansio n methods for next numerical solution in Matlab environment. There are many appl ications in technical practise described and modelled by linear or non-linear diff erential equation (DE) systems. A fictitious exciting functions method makes possible numerical solution of this DE system with non-stationary matrices. The solution o f examples with non-linear inductance is presented as well in the paper. 1 ODE System in Matrix State-Space Form There are many applications in technical practise m odelled linear or non-linear differential equation (DE) systems. Let’s have system of two fir st order ODEs (which can be given/rewritten as one ODE of the 2 nd order) d d − − = , d d − − = . The system can be also presented in matrix state-sp ce form d̅ d = ̅ + , where (1) =  , = are systemand transition matrices, ̅ =  and = are state (state-variables)and exciting vectors, respectively. Such a linear system of ODE can be solved analyt...

The novel approach of analysis and modelling of power single-phase voltage source inverter with resistive inductive load is introduced in the paper. The mathematical description of this system is using state space model with Z-transform method and series. Created impulse switching functions are used as exciting functions of this state space model. It makes possible to obtain the state variables in steady state and transient state in time domain using simulation model.

The paper deals with direct AC-AC propulsion system using [nx5] matrix converter and five-phase traction induction motor (IM) for hybrid electric vehicle (HEV) including electronic differential. Using the direct AC-AC system, in comparison to classical rectifier-inverter with DC link, features smaller on-state semiconductor switches losses and consequently higher efficiency of power train of the vehicle. The major advantage of using a five-phase machine instead of three-phase one is in smaller torque pulsation and better fault tolerance under one phase of supply. There are presented comparative analyses of [3x5], [5x5], [2x5], [1x5], [0x5] matrix converter feeding five-phase induction motor for HEV vehicle. Modeling and simulation are done using Matlab-Simulink environment, and simulation experimental results are given in the paper.

Paper deals with digital generating quadrature wave, their measurement and monitoring using LabView virtual instrumentation system. Beside classical triangular digital quadrature oscillator there are investigated rectangular-and meander-type waveforms and also three-phase Clarke transformed orthogonal waveforms. There is shown-using digital computation of total harmonic distortion-that meander-type quadrature waves reache minimum THD equal 5 %. The block scheme of virtual implementation of those system using LabView is given.