Artur Postil’s research while affiliated with Kremenchuk Mykhailo Ostrohradskyi National University and other places

The analysis of the factors of the use of electrical energy sources in microgrids from the point of view of the energy management system is a comprehensive study aimed at studying and evaluating various aspects of the use of electrical energy in small energy systems that can function independently of centralized energy networks. The main purpose of such an analysis is to identify key factors , which affect the efficiency and stability of the microgrid, as well as in the development of strategies to optimize their operation from the point of view of energy management. To achieve this goal, research is conducted covering the following aspects: technical characteristics of electrical sources, economic aspects, environmental consequences, energy management, social aspects. This is an important stage in the development of energy systems, aimed at creating efficient and sustainable energy solutions for the future. The analysis of the efficiency, reliability and power of various energy sources, such as solar batteries, wind turbines, batteries, etc., was considered. The cost of installation and operation of electric energy sources was calculated. , including the costs of maintenance, maintenance and replacement of equipment. The method of analyzing the impact of the use of various energy sources on the environment and the development of strategies for reducing emissions of greenhouse gases and other harmful substances are given. The essence of energy management systems that allow efficient management of production, storage and distribution of electricity in microgrids to ensure maximum efficiency and stability of system operation is considered. The question of the development of alternative energy sources has become particularly relevant, therefore, considering the existing structures of microgrids, it is advisable to notice the peculiarities of the construction of each microgrid, for example, the structure of a microgrid based on a wind generator can be built in several variants, and in a solar power plant, for efficient operation, the MPPT control algorithm is used, which aims to control the step-up converter in that point of the current and voltage characteristics of the photovoltaic battery, where the maximum output power can be obtained. In such microgrid structures, storage batteries are used for reserve, which are charged through step-up converters. Inverters are used to power the AC load. It is advisable to combine the solar power plant and the wind generator system into one microgrid structure, and to ensure the operation of the microgrid in conditions of low generation of one or both generating units, a diesel-generator system is used. In the built hybrid structure of the microgrid, there are operational costs that must be minimized.

Purpose. Development of a method for determining the cable line substitution scheme parameters based on the components of its instantaneous power. Methodology. Determination of unknown parameters of the cable line mode using the harmonic balance method. Determination of the U-shaped substitution scheme elements parameters is performed using power harmonics and their balance at the corresponding frequencies. For frequency-dependent elements, it is taken into account that the same power harmonic can be formed by different current and voltage harmonics. Findings. A method for determining the parameters of the cable line substitution scheme using the power components of its elements is proposed, which is distinguished by the fact that the total number of system equations for determining the parameters can be increased due to the use of power. The study of the proposed method for determining the cable line substitution scheme parameters based on the power components, based on the model compiled in the visual programming package, allowed us to establish that the largest parameter determination error is characteristic of active conduction. Originality. With the instantaneous power determination of the cable line substitution scheme reactive elements, it was found that during the calculation of the instantaneous power there is a peculiarity of taking into account the voltage harmonic number depending on the combination of harmonic numbers. Practical value. The proposed method can be developed on the sectioning of the U-shaped line substitution scheme to determine the change in the cable line substitution scheme parameters during its operation without disconnecting the line, unlike existing methods.

Purpose. Based on the instantaneous electrical power of a three-phase asymmetric system of sinusoidal periodic current, to determine positive, negative, zero-sequences active and reactive power, as well as invariance power factor. Methodology. In the unbalance case in three-phase electrical system, the electrical energy quality is evaluated by means on voltage and current positive, negative, zero-sequences. At the same time, similar components of active and reactive power have not received practical distribution. But it is precisely in terms of power that electricity is accounted for. The instantaneous power orthogonal components in the time domain are determined using the symmetrical components of voltage and current. Active, reactive powers of positive, negative and zero-sequences are allocated. The result obtained has the property of representativeness, which most of the known results lack. Findings. The three-phase system’s instantaneous power components are analytically determined, including the amplitudes of the oscillating power components. The need to take into account the oscillating instantaneous power components has been proven by means of a graphical interpretation of a special case of the three-phase system mode. As an integral indicator that takes into account the oscillating components of the three-phase system instantaneous power, its root-mean-square value over the repetition period is used. Originality. By calculating the transformer efficiency of the studied model according to the active power positive sequence and the same indicator according to the active power as a whole, it was established, that the component sequence separation affects the results of calculating the generalized indicators, including the power transmission system objects. This can lead to erroneous judgments about the efficiency of the specified facilities functioning. Practical value. The invariance power factor was used to characterize the electrical energy quality level of a three-phase sinusoidal current system in an unbalanced mode.

Purpose. Detection the relationship between the level of losses of a three-phase transformer and the power of distortion caused by current harmonics.. Methodology. During the research, the methods of determining power losses and additional losses in the elements of the electrical system from higher current and voltage harmonics, the visual programming method, the experiment planning method, and the orthogonal central composite plan method were used. Findings. An analysis of the indicators characterizing voltage and current distortions was carried out, and it was found that these distortions are most fully characterized by the current distortion power and voltage distortion power. These indicators are used to analyze the transmission of electric energy by a transformer of a traction substation. It is noted that the order of harmonics in the distortion power is not eliminated, and higher harmonics are taken into account by the corresponding effective current of higher harmonics. The specifics of the transformer secondary winding connections to the consumer, namely the grounding of one of the secondary winding phases, were taken into account. A number of combinations of current harmonics were used to simulate current distortions. The experiment was carried out using the planning method. The coefficients of the quadratic regression equation that relates power losses to the level of load current harmonics of the third, fifth, and seventh orders are obtaine To determine the significance of the obtained coefficients of the regression equation, the variances and the corresponding values of the Student's criterion were calculated, as a result, factors that do not affect the process and can be excluded from the regression equation were identified. The adequacy of the obtained regression equation was checked by Fisher's criterion. The analysis of the effects and their interaction showed that the standard error of the sample does not exceed 1.66%. As a result of analyzing the combinations of current harmonics that were set during the experiment, it was noted that some of them lead to the same effective phase current, while the power of current distortion is different. The greatest significance of the level of the third harmonic of the current is determined. The constant level of active power on the high voltage side of the transformer is noted, which is due to the absence of voltage distortions on it. Originality. Cases of combinations of current harmonic levels at which the current distortion power index remains unchanged, while the level of transformer power losses caused by current harmonics changes, have been identified. Practical value. This research can be used to assess and reduce the level of power losses in a transformer by filtering certain current harmonics.

The cable line is one of the main elements in the power transmission system, but due to the cable lines considerable length, monitoring the line condition and tracking its damage is a complex process. In practice, methods quite a variety are used to monitor the line condition, through monitoring the change in current and voltage in high-voltage cable lines with long distances, and control parameters using equivalent circuits. Study object is a short cable line, 6 km long, with a connected source of 6 kV, in a network with a non-linear load. Given its short-length, the overall changes in voltage and current will not have significant deviations between the input and output of the cable line. The main observation is carried out in the high frequencies area at a 2500 Hz frequency with the expectation of evident deviations in the current and voltage caused by the influence a non-linear load. By conducting two experiments, a line without damage and a line with damaged insulation, a number of deviations in the pulses change over time were revealed. The most evident deviations occur in the current, which is expressed due to a change in the main pulses amplitude and the significant appearance low-amplitude fluctuations between damaged phases under the influence of opposite-phase pulses.