Browsing by Author "Mishchenko, Tetiana"
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Item Development of a Spectral Theory for Analysis of Non-Stationary Pulse Stochastic Electromagnetic Processes in Devices of Electric Transport Systems(National Technical University of Ukraine "Igor Sikorsky Kiev Polytechnic Institute", Kiev, 2019) Szeląg, Adam; Kostin, Mykola O.; Nikitenko, Anatolii; Mishchenko, Tetiana; Jefimowski, WłodzimierzENG: A spectral analysis of traction voltages and currents is a basis for estimation of electromagnetic compatibility level and quality of consumed power in electric transport systems. However, such an analysis is usually performed for steady-state modes and only under the condition that the time realization of voltages and currents, being deterministic for continuous quantities, have infinite length. De facto, the electric transport devices operate in non-stationary dynamic modes (starting up, coasting, acceleration, iregenerative braking, stopping, wheel spin, voltage surges, etc.). As a result, the voltage across the traction motors and the current flowing through them are noncontinuous pulsed stochastic processes. It is necessary to add that in emergency modes the voltage and current are short-term single pulses.The paper presents the spectral analysis of such random sequences of pulses as well as their fronts and decays, the concepts of actual and instantaneousspectra. The analytical expressions for amplitudes and the initial phases of k-th harmonics are obtained using the discrete Fourier transformation. The numerical calculations of the spectral composition of stochastic pulse processes of voltage and current were performed for the DE1 and VL8 electric locomotives (Ukraine) as well as for trams operating on the i routes of the city of Dnipro. The actual and instantaneous spectra, as well as the spectra of the full correlation functions and their “tails”, were determined for the electric traction voltages and currents.Item Fryze Reactive Power in Electric Transport Systems with Stochastic Voltages and Currents(2020) Kostin, Mykola O.; Mishchenko, Tetiana; Hoholyuk, OksanaENG: The paper presents the theoretical foundations of reactive power and additional power losses in a direct current electric transport system. Numerical calculations of inactive power and losses in the circuits of electric DC locomotives and trams have been carried out. Discrepancy between the sign of the instantaneous power and the presence of exchange processes in non-linear circuits of electric transport systems with stochastic voltages and currents is discussed.Item Inactive Power in Electric-Traction DC Transport Systems(Revijo izdaja Elektrotehniška zveza Slovenije, 2022) Kostin, Mykola O.; Mishchenko, Tetiana; Hoholyuk, OksanaENG: The paper presents a theoretical background to determine the inactive power consumption features, i.e. the reactive power according to S. Fryze approach of the electric transport systems. Traction electric circuits of transport facilities of electric locomotives, feeder traction substations and city trams used in Ukraine demonstrate three features of the reactive power. According to the classical method, the inequality between the active and total power indicates the presence of the reactive power. The second feature is the time variation of an instantaneous impedance or instantaneous conductivity. The third is the inequality between the instantaneous reactive power to zero and the nature of its sign throughout the time of the electric power system consumption. The reactive power consumption gives rise to considerable additional power losses in the electric traction transport systems.Item Instantaneous Reactive Power in Systems with Stochastic Electric Power Processes(National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute, 2019) Nikitenko, Anatolii; Kostin, Mykola O.; Szeląg, Adam; Jefimowski, Włodzimierz; Mishchenko, TetianaENG: The paper is dedicated to the estimation of instantaneous reactive power in a DC traction power system. Currently, the integral and frequency methods are mostly used to define reactive power and do not give high accuracy in the calculations of power balance or cannot describe the essence of physical processes.The problem is complicated in DC electric transport systems due to random impulse character of voltages and currents. As a comparison, the calculation of reactive power according to various approaches was performed for the DE1 electric locomotive. It is suggested that the instantaneous reactive power should be used for the analysis of electromagnetic exchange processes in DC power systems. The paper shows the definition and main formulas for defining the instantaneous reactive power taking into consideration the random character of voltage and current. Numerical calculations together with statistical analysis were performed for two variants of experimentally recorded voltages and currents: the first one – on the bus-bar of traction substation, which supplies the section with the Pendolino trains in Poland and the second one – on the current collector of the VL8 electric locomotive in Ukraine. They confirm the validity of the aforementioned method.Item Transient Stochastic Processes in Power Circuits of Electric Transport Systems(IEEE, 2019) Kostin, Mykola O.; Mishchenko, Tetiana; Liashuk, Vitalii; Hoholyuk, Oksana; Stakhiv, PetroENG: The analytical method for the purpose of analyzing the transient processes occurring in the power traction circuits of DC electric transport systems allowing to take into account existing stochastic character of electric traction voltages and currents has been proposed. The method is based on using a modified form of Duhamel's integral adapted to the theory of random processes, in which the weight function is determined by the solution of the Wiener-Hopf correlation integral equation. Based on relationships of the proposed method the numerical calculations of transient stochastic characteristics (the function of mathematical expectation, the function of correlation, root-mean square deviation and dispersion) of the locomotive current in freight train operation of the Prydniprovsk railway were carried out.