Electric Power Quality Indicators Research Articles

Study of electric power quality indicators by simulating a hybrid generation system

Currently, as part of the distributed generation paradigm, photovoltaic energy has a growing development. The diversity of the loads, their nonlinearity, and the penetration of the renewable energy sources (RES) cause a worsening of the energy quality indicators. The main quality indicators that affect hybrid photovoltaic systems are voltage and current harmonic distortion, voltage deviation, and voltage and current asymmetry in the system. The construction of physical and mathematical models in software applications, such as MATLAB, Simulink, and Simscape, makes it possible to simulate the operating conditions of these systems and determine the values of the indicators that account for the quality of the electric power supplied. In this work, the modeling and simulation of a photovoltaic system connected to the network that feeds a mixed industrial area are carried out to determine the indicators of energy quality.

Reliable power supply to power consuming units via isolated distributed generation: problematic issues and approaches to their solution

The present study considers solutions to problematic issues concerning the integration of distributed generation facilities into the internal power supply network of power consuming units. The possibility of ensuring reliable power supply using verified models of generating plants and power consuming units is analysed along with a description of principles for the selection of control systems for generating plants. Full-scale measurements recording significant deviations in power quality indicators, were carried out. A total capacity of distributed generation facilities operating as a part of isolated energy districts is estimated at 8.5–9 GW. In addition, in the case of operation as a part of power systems, this capacity is equal to 13.5–14 GW. Therefore, the total capacity of these facilities is 22–23 GW or 9.5–10% of the total capacity of all generating facilities in Russia. The necessity of using verified mathematical models of generating plants, as well as main synchronous and asynchronous motors, along with the correct consideration of rotated mechanism types and real load factors, is substantiated. Principles for selecting the excitation systems of generating plants, as well as coordinating parameter settings for relay protection devices in generating plants and other elements in the internal power supply networks of power consuming units are considered. Recommendations regarding the permissibility of commutations and guaranteed correspondence between electric power quality indicators and regulatory requirements in island (autonomous) operating mode are provided. Thus, the need on the part of organizations that have necessary software systems and experience in conducting complex mode calculations to implement projects for integrating distributed generation facilities is substantiated. Here, the volume and complexity of calculations is higher than in the design of standard power plants and power supply systems.

Control of electric power quality indicators in distribution networks comprising a high share of solar photovoltaic and wind power stations

Mass-scale integration of renewable power stations into distribution power networks is a main trend of power industry development aimed at its decarbonation. All solar photovoltaic (SPVS) and wind power (WPS) stations are connected to the existing medium- and high-voltage distribution networks, excluding large capacity wind power and photoelectric fields. Modern SPVS and WPS are integrated into energy systems with the use of inverters/converters into which control algorithms for output power and protection have to be included. Critical deviations of electric power quality indicator (EPQI) from their normal operation values may occur, in networks, in these inverters/converters low-load conditions. Such deviation appears in low irradiance conditions in SPVS and low wind speed in WPS. It has to be noted that various electric loads of industrial consumers can be connected to the distribution networks for which such EPQI deviations are critical. This article deals with the newly developed method and device for EPQI sampling control enabling to automatically detect EPQI deviations including short-term ones. Results of preliminary simulation modeling, in various operation conditions, of distribution network including SPVS and WPS are used in the newly developed device. Besides, the device implements automatic Wald’s sequential analysis procedure on the basis of a multiple-choice indicator distributed in accordance with the binomial law. The effectiveness of EPQI sampling control based on the mathematical statistics methods has been demonstrated. It has been proposed to apply an integrated indicator, i.e. the absolute value of intercorrelation coefficient, for current and voltage signals, in order to take account of the complex effect of EPQI on the electric loads. Implementing the developed method and device for sample-based EPQI control makes it possible to prevent considerable and long-term EPQI deviations, in order to ensure reliable operation of consumers’ electric receivers, in distribution networks comprising a high share of SPVS and WPS.

Time structure of the distortion source identification of the electric power quality indicators and hardware and software system for its reduction

THE PURPOSE. Investigation of the time structure forthedistortion source identification of the electric power quality and a method for its reduction using of a mobile software and hardware instrumentation system.METHODS. The analysis of the number of complaints regarding low-quality electric power, the structure and values of the time spent on the identification of the distortion sources of the electric power quality indicators (PQI) for the standard values, taking into account all its components, was carried out.RESULTS. It is determined that the number of complaints received by the power grid company regarding lowquality electric powerremains high. At the same time, it takes a long time to identify the distortionsource before putting in place the necessary remedial measures. According to the analyzed data, it can take up to 21 days. The number of cases when the distortion source of the PQI couldn’t be detected within two days was 117 cases of 419 analyzed. The solutions to reduce this time are proposed.CONCLUSIONS. The solutions presented in the article make it possible to reduce the time spent on the source distortion identificationofthe PQI due to the use of a mobile hardware and software instrumentation system (HSIS). A variant of the HSIS structure is proposed, which includes sensors and the HSIS central unit. The proposed HSIS can be used in the absence of external communication channels through the use of data transmitted from the sensors of the system to the central unit using Long Range (LORA) or Wireless Fidelity (Wi-Fi) technologies. In addition, the HSIS provides time synchronization of all the sensors.

Improving the electric power quality in the networks adjacent to the railroad traction substations

A significant deterioration in the electric power quality indicators (EPQI) is observed in the 110-220 kV electrical networks, which are directly adjacent to the traction substations of the Trans-Siberian Railway. Such situations are typical of many regions of Siberia and the Far East. The article presents the results of research aimed at improving the electric power quality in the networks adjacent to the traction substations. The simulation algorithms used were based on application of phase coordinates and lattice equivalent circuits. Software tools Matlab and AnyLogic were used to model transition processes and evaluate the effectiveness of the concept of an intelligent electricity quality controlling system. On the basis of the results, technical solutions have been proposed to bring the electric power quality indicators to standard values. It is shown that a comprehensive approach, including the following segments, is needed to address the problem of reduced electric power quality: the use of technology to improve electric power quality indicators; reinforcing 110-220 kV networks that feed traction substations; technologies of smart customization and control of technical means.

Investigations of Electrical and Optical Parameters of Some LED Luminaires—A Study Case

In the paper, the electrical and optical parameters of wirelessly controlled LED lamps of the Hue type are analysed. Features of this class of wirelessly controlled LED lamps given by the producer are described and a measuring setup for the electrical and optical parameters of the considered LED lamps is proposed. The results of measurements of the two investigated lamps with variable hue, based on RGB chips or emitted white light of different CCTs (correlated colour temperatures), are shown and discussed. Attention was given to the parameters characterising the influence of the tested LED lamp on such electric power quality indicators as PF (power factor) and THD (total harmonic distortion). Therefore, the influence of voltage supply and the selected value of power density of the emitted light on the THD and PF is analysed and discussed.

Travel Activity Based Stochastic Modelling of Load and Charging State of Electric Vehicles

The uptake of electric vehicles (EV) is increasing every year and will eventually replace the traditional transport system in the near future. This imminent increase is urging stakeholders to plan up-gradation in the electric power system infrastructure. However, for efficient planning to support an additional load, an accurate assessment of the electric vehicle load and power quality indices is required. Although several EV models to estimate the charging profile and additional electrical load are available, but they are not capable of providing a high-resolution evaluation of charging current, especially at a higher frequency. This paper presents a probabilistic approach capable of estimating the time-dependent charging and harmonic currents for the future EV load. The model is based on the detailed travel activities of the existing car owners reported in the travel survey. The probability distribution functions of departure time, distance, arrival time, and time span are calculated. The charging profiles are based on the measurements of several EVs.

Исследование показателей качества электроэнергии на этапе проектирования авиационного синхронного генератора

The article addresses a comprehensive study of the quality indicators of the voltage produced by an aircraft synchronous generator. The study is carried out by applying a finite element analysis performed using the ANSYS Maxwell software package taking as an example the three-phase 115/200 V AC aircraft power supply system with a constant frequency of 400 Hz. To check the possibility of applying a finite element analysis, an analytical calculation of an aircraft synchronous generator was performed; its model was constructed in the ANSYS Maxwell software package environment, and the generator operation was simulated in its idle running mode and under the conditions of its balanced and unbalanced load. A finite element analysis of the model with an external electrical circuit connected to it is carried out. The construction and connection of electrical circuits makes it possible to implement the generator operation in different modes for obtaining the output phase voltage waveforms. Based on the simulation results, the electric power quality indicators (the amplitude coefficient, voltage modulation, voltage imbalance, phase voltage shift, distortion coefficient and harmonic components) have been estimated in the steady-state mode for their compliance with the normative values specified by the State Standard GOST R 54073-2017. By using the proposed method, it is possible to estimate the generated voltage quality indicators at the stage of developing an electromechanical converter, which will help reduce the time and cost of electrical machine design process.

Electric power quality indicators of electric arc industrial DC installations

Electric power quality indicators of electric arc industrial DC installations

Результаты исследования электрических параметров агрегата «печь-ковш» большой мощности и его влияния на питающую сеть

The steel refinement and its chemical composition and temperature finalization processes in a pouring ladle carried out by heating the metal with electric arc have received wide use at modern metallurgical enterprises. The article considers the electrical operating conditions of the ladle furnace unit (LFU) equipped with a 40 MVA electric furnace transformer. It was expected that the LFU load would vary insignificantly, because the electric arc burns between the electrodes and the surface of already molten metal, without the occurrence of short circuits. However, the accomplished studies testify that the LFU load is abruptly variable and nonlinear in nature, and gives rise to significant voltage fluctuations and harmonic distortions in the power supply network. The flicker intensity (severity) factor has been estimated, and the level of current harmonic components generated due to LFU operation has been determined. By using the obtained results, it becomes possible to predict the influence of LFU electric operating conditions on the levels of electric power quality indicators in changing the power supply network parameters, and to adopt circuit engineering solutions for assuring the electric power quality in the plant electric power supply system.

Электроснабжение высокоэнергоемких потребителей Мурманской области.

The systematization and analysis of the results of monitoring registrations of electric power quality indicators (PQS) on substation buses feeding large industrial enterprises of the Murmansk region was carried out. The example of existing substations shows the problems of high-energy facilities that have consumers with non-linear parameters. The problems of electromagnetic compatibility of industrial consumers with the mains have been identified. The need for research to identify the causes of non-compliance is proved. A number of the most common and effective measures to limit the distortion of the SCE are proposed.

Development of hierarchical functional models for diag-nostics of asynchronous electric motors using IDEF0 methodol-ogies

The paper proposes an approach to diagnostics of asynchronous electric motors based on the application of hierarchical functional models that are built using the IDEF0 methodology for integrated consideration of the influence of electric power quality indicators. A brief analysis of the problems of diagnostics for asynchronous electric motors is given, which justifies the relevance of developing new methods and models of diagnostics. A distinctive feature of the proposed hierarchical functional diagnostic models of asynchronous electric motors is a formalized representation of the necessary process functions using the IDEF0 methodology. This allows one to identify the main data flows in the diagnosis process, extract knowledge about the process, and reveal the cause-and-effect relationships of failures of asynchronous electric motors, complementing traditional methods of technical diagnostics by analyzing compliance with regulatory requirements concerning the electrical energy quality. A brief description of the developed methods, models and algorithms, as well as the results of experimental research, efficiency analysis of the proposed methodology is provided.

Improving the optimal system of automated control over the level of electric power quality indicators in electric networks

This paper reports solving an important scientific task of minimizing the economic losses caused by the established deviation and the asymmetry of voltage in the distributing electrical networks with a rated voltage of 10 kV.It has been found that the existing systems of automated control over the mode parameters of distributing electrical networks do not fully take into consideration the multifunctional influence of symmetry-compensating devices at the level of electricity quality indicators.It has been proposed to use, as the criteria functions for the task on automated control over the electric power quality indicators, the functional dependences that assess the level of losses caused by the established deviation and asymmetry of voltage in electrical networks. That has made it possible, in contrast to existing control systems, to better account for the negative impact of the established deviation and asymmetry of voltages on the modes of electric network operation.We have determined the functional dependences between the input and output parameters of the control object (a distributing electric network with a voltage of 10 kV with a symmetry-compensating device), which formed the basis of the criteria functions for a multi-criteria optimization problem. The ultimate solution to the problem on a multi-criteria optimization based on a method of approaching a utopian point in the criteria space was derived by minimizing the Chebyshev distance from the utopian point to a Pareto-optimal set of solutions. Based on the obtained solution to the problem on a multi-criteria optimization, we have built an algorithm for determining the vector of optimum control.Computer simulation of the optimal automated control system for the power quality indicators in distributing electrical networks has been performed.Analysis of the simulation results has revealed that the automated control system proposed in this work, when compared with the existing ones, makes it possible to reduce the negative effect exerted by the above-the-norm values of the established deviation and asymmetry of voltage on the operation of electrical networks

Analysis of the Power Quality of a Grid-Connected Photovoltaic System

The use of Grid-Connected Photovoltaic Systems is increasingly on the rise in Brazil. Faced with this growth, it is necessary to evaluate the impacts of this source in the electric energy systems. Based on this scenario, the present work aims to analyze and quantify the impact of a grid-connected photovoltaic system connection, evaluating the Electric Power Quality indicators based on the levels specified in Module 8 of the Electric Energy Distribution Procedures in the National Electric System. To perform the data collection, an energy analyzer device was installed at the output of the grid-connected system inverter located in the Energy Laboratory of the Federal Rural Semi-Arid University, located in the city of Mossoró-RN. Using the collected data, it was possible to analyze parameters of voltage and current distortion, power factor, active, reactive and apparent power, voltage, frequency variations, and voltage unbalance. It was observed that the criteria analyzed were within the appropriate standards although there were also verified cases that there was an elevation in tension levels. Finally, it is concluded that the impacts caused are relevant within the electric system, and grid connected system performance was satisfactory, although there are still possibilities for improvements.

COMPREHENSIVE METHODOLOGY FOR DETERMINING THE PARTIAL PARTICIPATION OF CONSUMERS IN THE RESPONSIBILITY FOR VIOLATION OF ELECTRICITY QUALITY INDICATORS

In the power industry, one of the most important aspects of energy conservation and environmental friendliness is to improve the quality of electricity and ensure electromagnetic compatibility. The quality of electricity is directly related to the efficiency of production, distribution and consumption of electric energy. In a market economy, the grid company and the consumer act as equal commercial partners, subjects of a single process of distribution and consumption of electric energy. To ensure interest in improving the quality of electricity, it is necessary to ensure conditions under which the losses incurred by the subjects of the process of electric energy distribution are paid by the true culprits. In international practice, the definition of responsibility for violation of the quality of electricity is dominated by two principles for determining the admissibility of a consumer connecting to the network in case of violation of the requirements for indicators of quality of electricity, which can be expressed in logical formulas: "pays the last" and "everyone pays his share". For Ukraine, a country with developed electric grids in which measures to comply with the quality of electric power are world practice of operating electric grids. According to this principle, each subject of the electric energy distribution process has the right to introduce its own share of distortions, but it is obliged to compensate for losses from the reduction in the quality of electricity, according to this share. It is advisable to assign an objective assessment of equity participation in compensation for damage to deterministic calculations, without the factor of influence on their result from the supplier or consumers of electric energy. A methodology for the comprehensive definition of liability for violation of the quality of electric energy is proposed. The methodology for determining the weighted coefficient of responsibility allows us to take into account: the possibility of simultaneous distortion of several indicators of electric power quality, such as steady-state voltage deviation, voltage unbalance, voltage non-sinusoidality, by one subject, the possibility of simultaneous distortion of one electric power quality indicator by different entities, the possibility of simultaneous distortion by several entities of various electric power quality indicators.

Electric power quality control in electro-technical complexes of oil processing plant

The paper deals with electric power quality research, in the load buses of the electrical networks of oil processing plant (“Production Association “Kirishinefteorgsintez”, LLC). Measurements were carried out under conditions of operating equipment at the distribution substations of the enterprise and at the division boundary of inventory responsibility with the power-supply system at the points of power transmission from the power-supply system to the industrial consumer. Assessment of the allowed contribution to the deterioration of electric power quality showed that at the increase in the rated capacity of drives based on frequency converters over 12% of the total installed capacity of electricity receivers of oil processing plant, the maximum allowed voltage waveform distortion coefficient values at the points of power transmission will be exceeded. To implement normalizing the electromagnetic environment and lowering non-sinusoidality of voltage, proposed is a system of measures, that allows controlling electric power quality indicators within the limits, stipulated by regulatory documents, resulting to reducing the risk of penalties by the power-supply authority and large scale undersupply of products under conditions of continuous technological cycle.

Применение дискриминаторных методов для оценки параметров режима энергорайонов с объектами распределенной генерации

The specific features of electrical operation modes in power districts containing distributed generating facilities under different conditions in terms of their circuit configurations and operation are analyzed. The analysis has revealed significant deviations of electric power quality indicators and occurrence of short-term fluctuations of operating parameters in a wide dynamic range under the conditions of fast electromechanical transients. The basic principles used to set up discriminator methods are outlined, and the possibility of using them in estimating the operating parameters under the conditions of deviations from normal electric power quality indicators and influence of various distorting factors is shown. Simplified and complete structural diagrams of the discriminator frequency and voltage measuring device are presented, and their advantages are shown. Application of the Goertzel algorithm for minimizing the computation effort in implementing the discrete Fourier transform is substantiated. The results from investigations into the dynamic characteristics of the discriminator measuring device for estimating the operating parameters as applied to emergency control are presented. It is shown that under harsh conditions for digital processing of signals with the level of interference components up to 15% of the voltage amplitude, the errors of estimating the voltage signal frequency and amplitude do not exceed 2,5%. Based on the simulation results, the effectiveness of using discriminator methods in digital processing of signals has been proven.

Статистические методы оценки параметров аварийного режима энергорайонов с объектами распределенной генерации

Different techniques for digital processing of the current and voltage signals used in estimating the operating parameters of electric power systems are analyzed. The drawbacks limiting the possibility of applying widely used digital methods for measuring the operating parameters in power districts containing distributed generation facilities are revealed. The effectiveness of applying statistical approaches to estimating the parameters of signals under the conditions in which the electric power quality performance indicators deviate from their normal values and various distortion factors have their effect is shown. The structural diagrams of measuring devices using which it is possible to produce the most plausible estimate with examples of estimating the emergency operation mode parameters are presented. An algorithm for operation of a multichannel measurement device with digital signal processing is proposed, which is able to simultaneously estimate several voltage parameters and featuring high accuracy under the conditions of the variable frequency and electric power quality indicators. Based on the computation and simulation results, the possibility to essentially reduce the measurement errors and increase the parameter estimation speed by using the maximal plausibility method is shown.

The evaluation of the operation of continuous monitoring system control of power quality at mining enterprises

In the paper, theoretical and experimental studies including measuring of the electricity quality indices at mining enterprises were made. The evaluation of the efficiency of the applied means of high-harmonic compensation was fulfilled. The proposals to create the system for continuous monitoring of power quality indices were developed. Electrical devices of surface and underground complexes of mines connected to distribution networks 6 kV and used in mining and processing of diamondiferous ores were considered as the research objects. The results of installation of the monitoring system of electric power quality indices at electric drives and frequency converters of some process units were studied. Technical and economic analysis was carried out, and the guidelines concerning the improvement of energy efficiency of frequency-controlled electric drives were formulated.

Влияние характеристик трансформатора на качество автоматического регулирования в системах электроснабжения

The necessity of applying the basic laws and rules of the automatic control theory with respect to the processes that take place in a classical transformer is substantiated. It is noted that transformers can be referred to the class of self-tuned automatic control systems. A transformer operating on an active load is considered, and the equations describing the processes occurring in this system are presented. In solving the equations, the magnetic material main magnetization curve was used as the magnetic characteristic. The solution of the equations is based on using the magnetization curve linear part, taking into account that the magnetization depends on the core material. The equations were solved in the form of Laplace transforms, and the structural-dynamic schemes were constructed using the automatic control theory. It is shown that improvement of the magnetic circuit is a method for obtaining linearity of the transformer nonlinear characteristics, due to which its performance is improved. In terms of power supply reliability, the Russian Electrical Installations Code (PUE) distinguishes consumers of the first, second and third categories, for which the permissible time of power supply interruption and the power supply network design features are determined: the number of independent power supply sources and feed lines. In case of network operation in the post-emergency mode, the deviations of electric power quality indicators shall not exceed the maximum permissible values, the duration of which cannot be more than 5% of the operation time. The country's power supply system includes many transformers, which are located in different regions and interconnected by a unified electrical network. For general-purpose electrical networks, the permissible and maximum voltage deviations equal to ±5 and ±10%, respectively, have been established. Changes take place in the measurement limits and in the set of additional functions, such as measurement of reactive component impedances and frequency. The current and voltage measurement limits are established individually. Under field conditions, the conclusion about the compliance of electric power quality with the requirements of GOST 13109-97 can only be drawn from the results of electrical network examination during a week. Counterload control of reactive power balance is also widely used to control the network operation mode.