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Voltage fluctuations are one of the most common problems in low-voltage networks. Very often, these disturbances cause damage to or the incorrect operation of electrical devices. Unfortunately, at present, the monitoring of these disturbances relies on short-term and long-term flicker indicators, which only assess the severity of one of the effects of voltage fluctuations. Another measure of voltage fluctuations that has greater diagnostic potential is voltage fluctuation indices, i.e., the amplitude and rate of voltage fluctuations. One advantage of these indices that has been highlighted in recent years is their potential ability to recreate voltage fluctuations using these indices. This article presents research results that allow for the verification of the potential of voltage fluctuation indices as a method for recreating voltage fluctuations. For verification purposes, various cases of voltage variation recorded in a modern low-voltage network are used. The analysis of the possibility of recreating voltage fluctuations from voltage fluctuation indices presented in this article, in association with previously carried out numerical simulation studies and experimental laboratory studies, constitutes a complementary whole and indicates further directions in voltage fluctuation research in terms of the electromagnetic compatibility of low-frequency conducted disturbances.

Voltage regulation based upon cyber systems has been extensively used with the development of cyber-physical systems. Still, cyber failure may result in controlling failure, which inevitably has an effect on the overall voltage performance of distribution networks. In order to access the influence of a cyber fault on voltage regulation, a cyber system validity model considering cyber soft failure is proposed. The analytical approach of voltage fluctuation and measurement indices of voltage fluctuation are also developed. Based on a simulation of a IEEE 33-bus system, the proposed model is proved to simulate the voltage regulation process taking cyber soft failure into consideration. Each influence of different fault factors is analyzed, which provides practical technical support for the planning and operation of the distribution system. This paper provides strategies for the research into cyber fault of distribution networks, which has critical significance along with follow-up value.

The paper presents the propagation assessment and power quality parameters improvement system in power distribution grid. In this work main functionalities of the system are described focusing on the individual assessment module. The module is using CIRED/CIGRE C4.109 method which is based on the 10-minutes aggregated data. Three cases of individual emission assessment using real measurement data in the distribution system operator environment ware analyzed. The obtained results confirmed the legitimacy of using 10-minute data to assess the emissions of harmonics.

Arc furnaces, due to their high unit power and load nature, belong to the receivers affecting the power quality. A dynamically changing electric arc is the main source of disturbances generated by arc devices. This current article presents the results of model tests of disturbances caused by arc furnaces. It also presents the attempts to estimate the power supply conditions for arc furnaces, so that they do not generate unacceptable disturbances to the power system. Various models of the electric arc are proposed. The values of the elements making up the furnace supply system were based on actual parameters. In these networks, measurements of electricity quality indicators were carried out, which allowed us to refer to the obtained results of model tests with the real values. Accordingly, to the real conditions, the values of the short-circuit power of the network and the power of furnace transformers were also adopted in the tests.

In the case of three-phase arc furnaces, two types of asymmetry can be distinguished: constructional and operational. The structural asymmetry is related to the construction of high-current circuits supplying the arc furnace. The knowledge of the parameters of the high-current circuit allows to determine the operating characteristics of the arc device. The author proposed a method for calculating the real values of the resistance and reactance of the high-current circuit. For this purpose, tests were made to short-circuit the electrodes with the charge. During the short-circuit, with the use of a power quality analyzer, measurements of electrical indicators were carried out, which allow to determine the parameters of the high-current circuit. A new method for determining voltage operational unbalance is also presented in this paper. The theoretical considerations presented in the article were verified in industrial conditions.

The growing share of distributed energy resources in the power system increases the number of power quality issues. The variable nature of their generation contributes to voltage fluctuations. This paper proposes a method for compensating voltage fluctuations utilising reactive power generated by a doubly fed induction generator (DFIG). The proposed method was first evaluated using a simulation model developed in the Matlab Simulink R2025a environment and subsequently validated experimentally under laboratory conditions. The results obtained are highly satisfactory, with the compensation time in laboratory tests not exceeding 500 ms. Since DFIGs are used in approximately 50% of wind power plants and the implementation of the proposed approach does not require additional hardware—only modifications to the generator control software—the method appears highly promising. It offers the possibility of rapid deployment without incurring significant costs.

Sinusoidal voltage fluctuations can be considered a specific result of the occurrence of voltage subharmonics and interharmonics, which are components of low frequency or not being an integer multiple of the frequency of the fundamental voltage harmonic. These components—symmetrical subharmonics and interharmonics—are of the same magnitude, while their frequencies are symmetrical with respect to the fundamental frequency. Depending on their phase angles, various kinds of voltage fluctuations can be distinguished: amplitude modulation, phase modulation and intermediate modulation. In this study, the effect of phase angles on noxious phenomena in induction motors was analyzed. Additionally, torque pulsations and vibrations of an induction motor under sinusoidal voltage fluctuation and a single voltage subharmonic or interharmonic were compared. The investigations were performed with the finite element method and an experimental method. Among other findings, it was found that for some phase angles torque pulsations could be about ten times higher than for other angles, roughly corresponding to the amplitude modulation.

The article presents the susceptibility coefficients active power kp and reactive power kq, as proposed by the author. These coefficients reflect the reaction of arc furnaces (change of the furnace operating point) to supply voltage fluctuations. The considerations were based on the model of the arc device in which the electric arc was replaced with a voltage source with an amplitude dependent on the length of the arc. In the case of voltage fluctuations, such a model gives an assessment of the arc device’s behavior closer to reality than the model used, based on replacing the arc with resistance. An example of the application of the kp and kq coefficients in a practical solution is presented.

Increased grid integration of photovoltaic (PV) has aggravated the uncertainty of distribution network operations. For a distribution network with PV, the impact of the PV location on the network power losses and voltage fluctuations is investigated with analytical derivations reflected by the line impedance. Optimization approaches of the PV location with consideration of two aspects, i.e., minimum network power losses and minimum voltage fluctuations, are analyzed. A particle swarm optimization (PSO) algorithm is used to synthesize an optimal compromised solution so as to determine the PV location. A 10 kV distribution network with one PV is established on the time-domain simulation environment PSCAD/EMTDC. The simulation results justify the theoretical analysis and indicate that when the active power of the PV is more/less than twice that of the overall loads/end loads, the network power losses and node voltage fluctuations are both minimum when the PV is integrated into the head/tail end of the network. When the active power of the PV is between the above two conditions, nodes t/f can be identified for the integration of the PV between the head/end nodes of the network to achieve the minimum network power losses/voltage fluctuations, respectively. The effectiveness of the proposed optimization approach is verified and can provide a reference for selecting the PV location in the distribution network.

This work shows an alternative method to determine the Voltage Unbalance Factor in a power grid by using both the mean value of the line voltages and Current Unbalance Factor in induction motors. Twenty unbalanced voltage points on three induction motors were used in order to compare the two methods. The influence of the measurement error of both the voltmeters and the ammeters on the resulting Voltage Unbalance Factor was studied, and the validation was made with laboratory data for one of the three motors analyzed, in addition to the simulations carried out. The proposed Voltage Unbalance Factor was compared with the most typical method in the standards to obtain this factor, showing that the proposed factor has a better approach than the standard factor to determine the value of the Voltage Unbalance Factor in an unbalanced power system.