Modes Of Electric Power Systems Research Articles

On the Determination of the Region Border Prior to the Limit Steady Modes of Electric Power Systems by the Analysis Method of the Tropical Geometry of the Power Balance Equations

The analysis of the known [8] approach in which tropical geometry over complex multifields of active power balances is used to estimate the region of existence of the electric power system mode. Its limitations are shown and a new approach is proposed, a criterion is also represented for determining the boundary that precedes the violation of the stability of the energy system due to the restructuring of the tropical set of solutions. The developed approach allows to determine the approach of the power system mode to the limit by the known parameters of the lines and the dynamics of changes of the nodes voltage modules and the nodes load.

Разработка метода идентификации синхронного сопротивления турбогенератора и критериев выбора состава данных синхронизированных векторных измерений

To enhance power system dependability and efficiency, it is of great importance to obtain correct parameters of the models of key power system components such as a synchronous generator (SG). Technology of synchronized phasor measurements allows us to estimate the SG model parameters through measurements in power system steady states and transients states, without switching the SG off and conducting complex testing procedures. The theory of electric circuits and electric machines, theory of optimization and statistics, and matrix algebra are applied in this study. The developed parameter estimation method has been implemented in the MATLAB software. The method has been verified through real-world measurements captured by a phasor measurement unit installed at a large power plant in the United Power System. This paper presents an algorithm of the turbogenerator synchronous reactance estimation via a set of synchrophasor data taken under steady-state conditions. Also, the paper considers the criteria for an appropriate data array ensuring successful parameter estimation. An algorithm has been developed and implemented in MATLAB software package. To improve the parameter estimation accuracy, an algorithm has been proposed to modify a nominal value for the SG no-load excitation current depending on the heating of the field winding. The algorithm has been successfully tested out based on a set of steady state synchrophasor data captured for one of the turbogenerators in the Russian United Power System. The authors have developed and analyzed quantitative criteria to determine a set of measured parameters of steady-state modes, providing the most accurate results of the turbogenerator synchronous reactance. The developed algorithm allows accurate update of the turbogenerator synchronous parameters through synchrophasor measurements recorded in a steady state modes of electric power systems. Using the criteria for selecting phasor data, it seems possible to automate the process of generating a data array of measurement of various steady-state modes necessary for identification. The proposed procedure that considers the field winding temperature can be employed in math models to estimate SG transient and subtransient parameters based on phasor measurements in transient modes of electric power systems.

RELATIVE ASSESSMENT OF THE COST OF RESERVATION OF RENEWABLE ENERGY SOURCES

The generation of electricity by solar and wind power plants depends on natural conditions, and therefore there are problems with their participation in the process of balancing the modes of electric power systems (EPS). It is difficult for them to carry out the forecasted and approved hourly generation schedule for the next day with the specified accuracy. The UES is forced to keep a capacity reserve to compensate for deviations of renewable energy sources (EPS) from the projected generation schedule. Since these deviations can be both larger and smaller than the permissible ones, it is by this criterion that we can choose and form a means to balance the EPS regimes. The paper proposes a method for researching backup measures of renewable energy sources with unstable generation in EPS. The criterion of optimality for comparing RES reservation methods is their relative costs 
 Among the ways of reserving RES, system reserve is generally used (mainly the maneuverable capacities of thermal and hydroelectric power plants), but since it is not enough, it is suggested to use other means of reserving power available today: electrochemical electricity storage, hydrogen and biogas technologies.
 Mathematical models based on the theory of similarity and the criterion method have been developed to analyze the technical and economic efficiency of certain means of reservation. The criterion method is preferred due to the fact that, with minimal available initial information, it provides an opportunity to compare different methods of reserving RES generation and determine the optimal ones. The method makes it possible to assess their proportionality, as well as to determine the sensitivity of costs to the power of reservation methods.
 Criterion models have been formed that make it possible to build the dependence of the costs and reserve means of variable RES generation on the capacity of the reserve means.. Such dependencies make it possible to more reasonably choose certain reservation methods at the first stage in accordance with the characteristics and requirements of the UES. They can be clarified if the price indicators that are valid at the moment and for the near future are known.

Analysis of photovoltaic power station (PPS) modeling using artificial neural network and PVsyst software

The possibility of using the method of artificial neural networks to analyze the modes of complex electric power systems with integrated large photovoltaic stations is considered. Based on the correlation analysis, the main factors influencing the energy parameters of photovoltaic power plants were selected and the boundary conditions for the Pearson coefficient were determined. The algorithm of the developed program for calculating the modes of electric power systems using neural networks is described, which makes it possible to more accurately predict generation, taking into account climatic conditions. On the example of calculations of the modes of the South-Western part of the energy system of Uzbekistan, taking into account the change in power flows as the generation of the Navoi photovoltaic plant with a capacity of 100 MW changes, a comparative analysis of the results obtained by calculation with real measurements was carried out.

Experimental and statistical methods for studying the modes of electric power systems under conditions of uncertainty

The issues of mathematical modeling of the modes of electric power systems in conditions of inhomogeneities such as time drift of the main indicators are considered. In conditions of incomplete knowledge of the mechanism of phenomena, mathematical modeling was carried out by experimental and statistical methods, namely: experiment planning was used.

On the problem of calculating steady state modes of electric power systems under conditions of interval data uncertainty

Currently, there are several approaches for dealing with uncertain (inaccurate) data. The main ones are methods of probabilistic analysis, fuzzy set theory and interval analysis. In this paper, we consider the problem of calculating the parameters of steady-state modes of electric power systems with interval uncertainty of the initial data. The main reasons and the relevance of the use of interval methods for calculating the parameters of steady-state modes of networks of electrical systems are described. First, an interval calculation model is formulated, and then some interval iterative methods for solving nonlinear nodal equations of electrical networks are studied. Algorithms for the interval methods of Gauss-Seidel and Newton-Raphson are proposed for solving nonlinear nodal equations of steady state electrical networks. To demonstrate the level of efficiency of the developed algorithms, several test calculations were carried out with interval parameters formed through the middle and radius of the interval. The results of numerical calculations using these methods show that the Newton-Raphson method is superior to the Gauss-Seidel method in terms of the number of iterations and optimality (with a smaller width) of interval solutions.

An algorithm for optimizing short-term modes of electric power systems, taking into account the conditions of the nature of the probability of the information flow of data

The work contains the results of the analysis of studies that were carried out to improve the operating modes of power facilities, taking into account uncertain data and the possibility of changing the load. A mathematical model of energy objects is formulated taking into account various types of restrictions. A comparative analysis of methods for solving problems was carried out and a method based on a penalty matrix was chosen. The results of the experiment showed the effectiveness of the proposed method for optimizing the modes of power facilities during changes in loads in different periods.

Topology Optimization of the Network with Renewable Energy Sources Generation Based on a Modified Adapted Genetic Algorithm

The article presents an adaptive genetic algorithm developed by the authors, which makes it possible to optimize the topology of a power network with distributed generation. The optimization was based on bioinspired methods. The objects of the study were a 15-node circuit of a power net-work with photovoltaic stations and a 14-node IEEE augmented circuit with distributed generation sources (three wind farms and two photovoltaic plants). The simulation of the modes of electric power systems was performed using the Pandapower library for the Python programming language, which is in the public domain. Three types of electric load of consumers were considered, reflecting the natures of electricity consumption in the nodes of real electric power systems, the results of numerical studies were presented. The proposed genetic algorithm used two different functions of interbreeding, the function of mutation, selection of the best individuals and mass mutation (complete population renewal). At the end of each iteration of the algorithm operation, statistical dependencies were de-rived that characterized its work: the best (minimal losses) and average adaptability in the population, a list of the best individuals throughout all iterations, etc. The verification was carried out in comparison with the results obtained by a complete search of possible radial configurations of the system, and it showed that the developed genetic algorithm had fast convergence, high accuracy and was able to work correctly with different configurations of electrical circuits, generation and load structures. The algorithm can be used in conjunction with renewable energy sources generation forecasting systems for the day ahead when planning the operating modes of power units in order to minimize the costs of covering electricity losses and improve the quality of electricity supplied.

A review on distributed generation impacts on electric power system

In 2021, the world's total installed capacity of generation units based on renewable energy sources (not including hydropower) amounted to about 1674 GW: over 825 GW and 849 GW of wind and solar power plants were installed respectively. The growing of the installed capacity of these distributed generators is a response to the increasing the power consumption, global environmental issues and has also become possible due to the development of technology in field of power semiconductor devices. However, on the way of large-scale implementation of distributed generators based on renewable energy sources, traditional electric power system meets new challenges to ensure the reliability and sustainability of new electric power systems with renewable energy sources. In particular, distributed generators change processes in the electric power system, impact to the parameters and power balance, change the magnitude and direction of power flow and short-circuit current, which determines the need to update the settings of the relay protection and automation systems of traditional electric power system and to coordinate their operation with automatic control systems of installed distributed generators. The above-mentioned tasks form a number of scientific research directions, one of which is a task of determining optimal size and location of distributed generators. The main purpose of this optimization task is to reduce power losses, operating and total electricity cost, improve the voltage profile, etc. In addition, the correct and reasonable placement of distributed generators defines an effective planning of the operating modes of electric power system and power plants (especially based on renewable energy sources, the operating modes of which depend on weather conditions and can be sharply variable).The paper highlighted the impacts of distributed generators on power losses, the voltage level, maintaining the power balance and the possibility of participating in the frequency regulation, and short-circuit current in power system. The optimization criteria, the main limiting conditions, as well as methods for solving this optimization problem are considered. This review will help the System operators and investing companies, especially in Russia, to form the main aim, objective function and constraints that will aid to meet their load demand at minimum cost and to choose from the options available for optimization of location and capacity of distributed generators.

Impact of renewable generation unit on stability of power systems

Nowadays, the development of the electric power system is associated with the penetration of power generation units based on renewable energy sources and operated with energy storage systems. However, the operation of such generation units changes and complicates the processes in the electric power system, which determines the need for a number of studies and analyses. This paper presents the results of assessing the impact of the operation of photovoltaic plants on the static stability of the electric power system. To achieve the goal, the EUROSTAG software was used. The results of studies of normal and post-emergency modes of electric power system with the different penetration level of generation units are presented, power system stability coefficients of active power and voltage are determined, damping properties of electric power system based on the calculation of the transient damping coefficient of the damping process are estimated.

A Stochastic Model for Determining Static Stability Margins in Electric Power Systems

This paper aims to develop a method for determining margins of static aperiodic stability for electric power systems equipped with distributed generation plants. To this end, we used generalized equations of limiting modes in a stochastic formulation. Computer simulation showed that the developed methodology can be used in solving problems of operational control of the modes of electric power systems. On the basis of the results obtained, we arrived at the following conclusions: the modified equations do not allow the iterative process to converge to a trivial solution and, therefore, they ensure high reliability of results when determining stability margins in a stochastic statement; a technique based on the introduction of an additional variable can be used to improve the convergence of computational processes when determining the stability margins in a deterministic statement; the parameters of the limiting modes obtained in the deterministic and stochastic formulations may significantly differ; with an increase in the variance of the load graphs, the risk of stability violation significantly increases; at the same time, the amount of the margin determined on the basis of the Euclidean norm remains overly optimistic; in the illustrative example, a significant increase in the risk of stability violation takes place during planned and emergency shutdowns of the EPS elements.

Model of implicit pole electric machine based on mathematical formulation of magnetic field in air gap

When modeling transient processes in electric power systems, the issue of designing reliable models of electrical machines is of great interest. The most difficult task is to design the models of synchronous and asynchronous machines. The purpose of the project is to develop mathematical models of synchronous and asynchronous machines based on a generalized model of an implicit-pole machine that considers the change of rotor speed, geometric shapes, and the type of rotor and stator windings. Methods of mathematical modeling of electromagnetic fields in the air gap based on Maxwell equations and methods of the theory of electrical circuits are applied. A system of nonlinear differential equations is considered as a mathematical model of a generalized implicit-pole machine. The key assumption made is the high magnetic permeability of the stator and rotor cores. Technical data of real electric machines have been used for verification. Mathematical models of an implicit pole synchronous machine and an asynchronous machine with a phase rotor have been developed. These models can be used to analyze transient processes in the aggregate without dividing them into electromagnetic and electromechanical ones. The novelty of the models is the fact of non-sinusoidal distribution of the magnetic field in the air gap, various types of multiphase AC windings and rejecting the principle of constant rotation frequency at the time step of the simulation. The proposed mathematical models can be used to solve design problems, to analyze the modes of electric power systems, the operation of relay protection and automation of electric power facilities, and emergency automation. In the future, the equations that consider the influence of the damper circuits and the peculiarities of the windings will be added to the developed mathematical models. The purpose of further research is to develop models of salient-pole synchronous machines and asynchronous machines with a squirrel-cage rotor.

Statistical Multimode Accounting in the Problem of Optimal Reactive Load Compensation when Constructing Smart Grids

The article deals with the development prospects for smart grids. An approach to optimizing the modes of electric power systems in terms of reactive power is presented in detail. The solution of this problem considers the multimodality, determination of the integral characteristics of the modes, etc. Analytical modeling of load changes by means of the method of factor analysis allows to reduce the amount of information drastically without a significant loss of the accuracy of the obtained solutions. For this purpose, the actually correlated electrical loads of various nodes of electric power systems are represented in the form of a linear combination of independent random variables, namely, generalized load graphs. It is shown that the inclusion of multimode by orthogonal graphs results in a significant simplification of the solution of multimode problems. The choice of the dependent and independent variables composition when solving the optimization problem with the power consumption modes has a fundamental effect both on the modeling of constraints, the formation of the reduced gradient and the main calculation expressions, and on the speed of the optimization search as a whole

Analysis of the most common methods for determining the stability of energy systems

Problem. There are many methods for determining the stability of the energy system. In normal operating condition (normal rated mode), the power system must reliably ensure the consumption of electricity of normalized quality. However, in addition to the normal state, there are emergency and transient states caused by various transients. This is due to the fact that the energy system is constantly changing its parameters. Such changes are determined by variations in the amount of power produced and consumed, as well as the changes in system configuration. Goal. The goal is studying the possibilities of various methods of determining the power systems stability and drawing up the general algorithm of actions for maintenance of their stability. Methodology. When determining the stability of energy systems by the Lyapunov method, two methods can be used: the direct method and the first approximation method. Lyapunov direct method refers to differential methods. To conclude about the stability of the system we do not find a general or particular solution of differential equations, but with their help we find a mathematical function, the complete derivative of which over time allows to obtain a conclusion about the stability of the system. Results. Many methods can be used to determine whether a sustainable energy system is stable or not. The most common are the Lyapunov methods and the Moiseev method. It is determined that the direct Lyapunov method refers to differential methods. The application of the direct Lyapunov method for energy problems is limited. Currently, it can be used only for some individual cases. The method of the first approximation (Lyapunov first method) has received wider application in the solution of power problems. When applying this method, which belongs to the group of methods of full integration, the right-hand sides of the equations are decomposed into power series. Originality. It is determined that one of the perspective directions of increasing the efficiency of the mathematical device work is using the methods of the second order in modeling and optimization of operating modes of electric power systems. This allows you to increase the speed and reliability of the convergence of iterative processes. Practical value. Based on the analysis of various existing methods for solving the problems of stability of energy systems, an algorithm of actions is proposed and developed, which will help to solve the problem of stability in practice.

МІНІМІЗАЦІЯ ВПЛИВУ НАСИЧЕННЯ МАГНІТОПРОВОДІВ ТРАНСФОРМАТОРІВ СТРУМУ НА ТОЧНІСТЬ ВИСОКОВОЛЬТНИХ ТРИФАЗНИХ ПЕРВИННИХ ВИМІРЮВАЛЬНИХ КАНАЛІВ З ЦИФРОВИМ ВИХОДОМ

The classification is carried out and the characteristics, capabilities and disadvantages of the known methods of programmed correction of the output current of a single-phase primary measuring channel (PMC) of the current are determined. A discretized model of short-circuit current (SCC) is proposed. A method and an algorithm for increasing the accuracy of a three-phase current PMC in transient modes of electric power systems (EPS) under the condition of saturation of the magnetic circuits of its phase current transformers have been developed. The reliability of the developed method is confirmed by simulation of the PMC output current under the condition of phase-to-phase short-circuit of phases A and B without correction and with correction of its phase currents. It is shown that the developed method makes it possible to reduce the total error of the PMC in the transient modes of the EES under the condition of saturation of the magnetic circuits of the CT from 70-90% to 6-15%. References 47, figures 6, table 1.

Визначення ризику порушення нормального режиму енергосистеми при плановому і аварійному виведенні з експлуатації електрообладнання

The development of competitive relations in the electricity sector, the increase the number of large-scale systemic accidents in the world that have occurred in market economies, improves the importance of the reliability factor for the electric power system (EPS). In this regard, the tasks of taking into account and analyzing all risks, especially the EPS risk operation due to electrical equipment failures, which currently has a significant level of wear and depletion of resources, are relevant in power industry of Ukraine. To solve these problems, it is necessary to develop models for assessing of technical condition and risk of electrical equipment failures. Equally important are the issues of decision-making on the strategy of operation of defective electrical equipment and emergency risk assessment in the power system when the equipment is disconnected. The conditions of functioning of modern electric power systems are analyzed. The problem of estimating the operation reliability of the power system based on the definition of risk indicators is formulated. The necessity of complex modeling of technical condition and modes of EPS for determination of quantitative indicators of emergency risk of a normal mode of EPS under electric equipment failures is substantiated. A generalized linguistic model is proposed to assess the subjective probability of electrical equipment failure under the presence of a defect. An algorithm of complex modeling of the EPS mode for estimating the emergency risk of the normal mode in case of electrical equipment failures by statistical modeling is proposed. An assessment of the subjective probability of failure of a power transformer actually functioning in the EPS has been performed. A comprehensive modeling of the EPS mode was performed to assess the emergency risk of the normal mode during emergency decommissioning of the power transformer. The advantage of the proposed development is the ability to determine the probability of failure of electrical equipment due to unsatisfactory technical condition based on the use of quality information, to form a priority for decommissioning electrical equipment based on risk indicators in the power system.

The Concept of Constructing an Artificial Dispatcher Intelligent System Based on Deep Reinforcement Learning for the Automatic Control System of Electric Networks

The concept of the Artificial Dispatcher autonomous intelligent control system for integrating into modern automatic control systems of electric networks in order to improve the efficiency of managing the modes of electric power systems is proposed. This intelligent control system is implemented based on the deep machine learning technology and joint use of the Monte Carlo tree search method and deep artificial neural networks. It is shown that the efficient training of the Artificial Dispatcher intelligent control system is achievable through an innovative self-play algorithm, without using large databases of circuit-mode situations and expertise in managing the modes of electric power systems. Calculation examples of using agents created based on the concept of the Artificial Dispatcher intelligent control system in the problems of the automation of substation technological processes (managing voltage and reactive power controllers) and industrial enterprises (DC servomotor control) are presented.

Impact of the configuration and condition of the power system on the damping of low-frequency oscillations

ABSTRACT The current stage of power system development is characterised by the transformation from local electric power systems to global interconnections. It provides economic benefits, improves the reliability of power system operation and increases the quality level. However, such large interconnected systems have some technical and economical limitations, for instance, long distance transmission, and almost have a weak tie between the electric power systems. One of the main problems of the reliability of such large interconnected systems is low-frequency oscillations, which significantly reduces network capacity and leads to dynamic instability. Therefore, the analysis of the influence of various topologies and regime modes of electric power system to the low-frequency oscillations for the development of control actions and recommendations for their effective damping and reduction is relevant. In this paper, simulation and analysis was done by using of two-area electric power systems and using «EUROSTAG» software. The factors, such as the previous steady-state condition and the structure of the electric power system, affecting the damping properties of electric power system and the impact of the Back-to-Back High-Voltage Direct Current link based on voltage source converters to the damping of low-frequency oscillations were considered.

ОСОБЕННОСТИ КОМПЕНСАЦИИ РЕАКТИВНОЙ МОЩНОСТИ В ЭЛЕКТРОЭНЕРГЕТИЧЕСКИХ СЕТЯХ И СИСТЕМАХ

The article considers the conceptual issues of the specifics of optimizing the modes of electric power systems by compensating for reactive power, taking into account the voltage level. Taking into account the level of electric power quality, load change modes, specific cost of the control means and functional tasks, it is determined the algorithmic requirements for the optimization process: according to the criterion of the minimum loss of electric power in the networks and the minimum damage of specific consumers (consumer groups), respectively. The most efficient hardware based on static devices of the FACTS process platform is proposed.

Optimization of modes of the electric power systems by genetic algorithms

In article discusses issues for solving optimization problems based on the use of genetic algorithms. Nowadays, the genetic algorithms for solving various problems. This includes the shortest path search, approximation, data filtering and others. In particular, data is being examined regarding the use of a genetic algorithm to solve problems of optimizing the modes of electric power systems. Imagine an algorithm for developing the development of mathematical models, which includes developing the structure of the chromosome, creating a started population, creating a directing force for the population, etc.