Power Systems Research and Operation

Load–frequency control is one of the principal tasks of providing the reliability of power system operation considering the increasing share of renewable energy sources. This chapter covers the various aspects of providing the power system operation with renewables. The chapter consists of three parts. In the first part, the identification methodology of the overloaded elements in the power system is presented. The proposed methodology is based on the “N-1 principle” allowing identifying weak elements in the network. The second part covers the issue of the participation of windfarms in the secondary frequency control. In the third part of the chapter, the simulation results of the windfarm controller and energy storage system to improve primary frequency control are provided.

In this chapter one approach to the problem’s solving of distribution electrical networks’ (ENs) state estimation under telemetered information incompleteness conditions is presented. This approach is focused on the use in the dispatching system and in addition to telemetered EN operational condition parameters involves also using of the results of seasonal control measurements processing and expert fuzzy estimates on the possible boundary values of the loads’ active power of the so-called unobservable nodes. Such expert information is formalized in the form of corresponding trapezoidal membership functions. Problem solving results are expert-calculation estimates of EN operational condition parameters. An example of EN scheme’s fragment with the rated voltage of 110 kV and corresponding results illustrating the proposed approach application are presented.

The main requirements for the volume of ancillary services in the IPS of Ukraine, in particular, the frequency containment reserve and frequency restoration reserves are considered. The influence of renewable energy sources (RESs) on the balance of production and consumption of electricity is shown. The place of hydroelectric power plants in the modern conditions of functioning of the IPS of Ukraine and the structure of the market of ancillary services is considered. It is shown that with the existing structure of production capacities in the IPS of Ukraine, in fact, only HPP and PSHPP units are able to balance the fast-changing load schedule of renewable energy sources due to their high maneuverability. Features of operation of HPP units in normal and emergency modes are provided. The plan of HPPs/PSHPPs operation in the electricity market is provided, which takes into account the indicators of the forecast balance of the IPS of Ukraine (monthly electricity production volumes of each HPP), water management constraints, current marks of the levels of HPP reservoirs, specific consumption of hydro resources, etc. Prospects for the development of ancillary services in the IPS of Ukraine are identified. According to the results of the operation feature analysis of the IPS of Ukraine, the need for updating the regulatory framework is set out, in particular as for updating the requirements for the minimum required reserves volumes to adjust frequency and active capacities in the IPS of Ukraine given the growing share of unregulated RESs in the production capacity structure. Certain measures are provided to increase the level of operational security of modes in the conditions of further development of RES and plans for synchronization of the IPS of Ukraine with ENTSO-E energy systems. Measures are provided to correct the situations related to the imbalance of HPP hydro modes. The model of optimal distribution of production capacities of the HPP cascade by segments of the electricity market under the conditions of observance of the predetermined balance of hydro resources is provided. Using the provided model allows to maximize the economic effect of HPPs/PSHPPs operation in the electricity market.

The study is devoted to the issue of creating an effective automatic load and frequency control system using modern electric energy storage systems based on high-capacity batteries. As part of the study, different types of regulators are considered. The authors proposed an approach to the implementation of a control system using battery energy storage systems. Comparative calculations of different control systems are performed and the advantage of the proposed approach is demonstrated. The study was carried out by numerical simulation of an automatic load and frequency control system with emergency disturbance. The efficiency of regulation was determined on the basis of the analysis of the accepted indicators of the regulation quality, namely, the maximum frequency deviation and the duration of the transient process. It was found that the use of high-speed battery energy storage systems in the automatic load and frequency control system shows the best performance in frequency stabilization, satisfying the regulatory requirements established in the power system.

The reliability of electrical networks and systems largely depends on the accuracy of load forecasts used to calculate losses, imbalances, and modes of operation of power systems. The use of modern forecasting methods allows us to obtain more accurate results, faster calculations, flexible enough to solve a wide range of problems. Artificial neural networks today are one of the most common tools for building complex mathematical models depending on the tasks. This spread of artificial neural networks is due to the significant development of computer technology. Depending on the characteristics of electrical networks and their loads, the accuracy of different forecasting methods may vary. Additional factors also have a significant impact on forecasting accuracy. Therefore, accurate load forecasts for different load levels require modern and effective methods that could take into account the relationship of additional factors. Among the factors that have a significant impact on changes in the electrical load of the power system are meteorological factors, namely temperature. To determine the exact relationship between load and external factors, the method of decomposition of graphs using the Hilbert-Huang method is considered. This chapter discusses the possibilities and prospects for the application of modern forecasting methods based on artificial neural networks, respectively, for forecasting electrical networks of different hierarchies with the possibility of taking into account temperature.

The chapter is devoted to the development of theoretical and methodological bases for the synthesis of models of the complex electric power systems with distributed generation and renewable energy sources. When distributed generation (DG) sources are connected to the united power system (UPS) of Ukraine separately, as active consumers (prosumers), as part of microgrids and as separate generating facilities, a number of issues arise related to ensuring proper synchronization of the parameters of aforementioned systems, their electromagnetic compatibility, quality of electricity, occurrence of additional losses and reliability of their work. This chapter of the monograph discusses the technical means (and their parameters) and economic models and methods that should be used in the process of synthesis of the complex power systems with DG to ensure their optimal functioning. The chapter provides a game-theoretic approach of addressing a hard task of synthesis of complex power systems with DG and renewable energy sources. Game theory attempts to mathematically simulate strategic behavior in game situations. Various mathematical formulations of cooperative game theory have been applied for loss and cost allocation. Shapley, Aumann-Shapley, and Nucleolus-Based are the most common. The proposed game allows not only to combine both technical and economic models for power systems with DG sources and RES, but also to find an optimal solution in the process of synthesis of complex power systems. This optimal solution is found as Nash equilibrium for the proposed game.

The chapter shows that for the analysis of the optimality of processes in local power supply systems (LPSS) are crucial for improvement and further additional development of methods for demand response effectiveness assessment in systems with active consumers. The main differences between the existing LPSS and next generation, based on the Smart Grid concept, mechanisms of influence and effects from implementation of Demand Side Management (DSM) were assessed, what allowed to choose the minimisation of Frieze reactive power Q_F as a criterion for cost reduction. Proposed method for estimating the impact of uneven electricity consumption on the level of losses in LPSS in contrast to the existing ones, uses modified Frieze Q_F power decomposition indicators and common determinations of Frieze Q_F power for an arbitrary time interval, which considers the influence of uneven power levels on electricity consumption, as well as k_Δopt, which characterizes the efficiency of regulation and determines the level of suboptimal energy transfer in terms of eliminating its losses. The system of energy efficiency indicators has been expanded by Frieze Q_F power loss criterion, which assess the influence of uneven electricity consumption factors and operation modes of LPSS for a certain time interval. The obtained values for the calculation of losses from the uneven generation modes and consumption of electricity are used in the case of retrospective, prospective and real-time analysis, changes in cosφ, voltage deviations, the influence of higher harmonic components. A methodology for optimizing power consumption schedules using Q_F power decomposition in the case of targeted power consumption mode management and implementation of electricity demand management programs is proposed. Methodology is implemented as an algorithms and suitable software for detailed transmission, accumulation, and consumption time period T analysis for management improvement by the distribution system operator (DSO). The LPSS daily electricity consumption schedule optimisation method was improved on the example of residential complex an optimisation problem was formed for prosumers: energy costs reduction and daily consumption schedule optimisation, considering it consumption modes and values of equipment flexibility index k_flex.

Over the last decade, there has been a growing in the dependence of electricity production by solar power plants (SPPs) in Ukraine. Therefore, there is a need to optimize the structure of the energy balance of the state, based on the requirements of energy security and ensure the share of renewable energy at 25%. However, with the development of renewable energy sources (RESs) there is a problem of ensuring the appropriate maneuverability of the power system. This is due to the fact that the structure of generating capacity of the United Power System of Ukraine in terms of effective regulation of frequency and power in the power system is suboptimal. Among the reasons for this, the main ones are unregulated and variable operation of a SPP, which is exacerbated by the lack of tools and approaches for the power generation modes forecasting. That is why the issue of accurate forecasting of the possible electricity generation volume has become acute. However, solar energy forecasting is a rather difficult task, as it largely depends on climatic conditions that change over time. This study presents an analysis and application of the seasonal autoregressive integrated moving average (SARIMA) method to develop a model that can support and provide forecasting the amount of power produced by SPP. Data for the development of the model were obtained from the time series of electricity generation on the example of the SPP in the village of Velyka Dymerka, Kyiv region. The data consisted of more than 26 thousand samples collected from July 1, 2020, to December 31, 2020, which characterize the operating conditions of solar panels with a capacity of 9 MW. This led to the choice of the SARIMA model. The coefficient of determination (R²) for the obtained model was 92%. This indicates the ability of the final model to accurately represent and give forecast based on data set of the SPP power generation.

The ways to increase the reliability of time-synchronization signals of power systems are considered. The features of the development, research, and implementation of a system for automated multi-channel monitoring of time-synchronization devices are presented. The necessity of simultaneous measurements of several signals of time-synchronization devices and the use of IP technologies for the transmission of digital measurement data is determined. The description of the developed schemes of the multi-channel monitoring device, which includes: LPC2378 microcontroller, programmable logic chips “ALTERA”, electronic elements of the RS-232 interfaces, Ethernet, is presented. Theoretical and probabilistic studies of the stability of characteristics of multi-channel monitoring device in real operating conditions on the objects of electric power networks are carried out. The influence of changes in the ambient temperature, supply voltage, frequency-dependent parameter, and frequency of the time-synchronization signal on the variable of deviation of pulse duration of the finite signal of single vibrator from the nominal value are considered. Analytical dependencies were obtained to determine the estimation of the actual value and confidence area for the deviation of the variable of pulse duration of the finite signal of single vibrator in the real operating conditions of the device. The actual operating variable of the deviation of pulse duration of the finite signal of single vibrator and the conditions of optimal temperature stability of the device for multi-channel monitoring of time-synchronization signals of power systems are determined. Laboratory samples of functional parts and a prototype of multi-channel monitoring device were made; their adjustment and testing were performed. Experimental studies were conducted using the receivers of the GPS satellite navigation system, which confirmed technical capability of the device to carry out a reliable real-time monitoring of four time-synchronization signals simultaneously. The use of the obtained digital monitoring data allows to improve the quality of time-frequency support and, as a result, to increase the reliability and energy efficiency of SMART Grid power systems.

Ensuring the quality of electricity is one of the ways to increase the efficiency of the entire energy complex of Ukraine and its individual energy systems. At the same time, it is necessary to note the following. Analysis of the current state of Ukraine’s electricity industry shows that its current integration with the electricity sector of the EU requires compliance with the necessary conditions for compliance with strict requirements for electricity quality parameters, which must be within acceptable levels set in a number of regulations. It should be noted the following. The development of measures to ensure the required quality of electricity is possible only after assessing its actual state in all nodes of the country’s electricity system. Therefore, the system of real-time monitoring of electricity quality should be based on real-time monitoring system. This study considers the model of information flow in the electrical network, which is a hierarchical structure of comparative, frequency calculation of local maxima of wavelet transform coefficients with time shift, adaptive to the singular behavior of the signal. This model allows from a single mathematical standpoint based on the analysis of frequency-time and spectral characteristics of comparative wavelet coefficients to conduct the full range of data processing on power consumption modes, definition, identification and classification of distortions of electricity quality. Based on the analysis of the detailed coefficients of the wavelet composition, a generalized identifier of the distortion of the quality of electric energy is presented, which serves as a basis for the express analysis of the quality of electric energy in real time. Its application allows, regardless of the type of distortion, its direct detection, beginning and/or end. Further identification of the type of distortion and its classification is carried out using the developed modified vector of features of the classification of distortions of electricity quality. Whereas, as a result of wavelet decomposition of the information signal and analysis of the obtained wavelet coefficients, time-localized information on its distortion (deviation from the nominal values of its parameters) from the high- and low-frequency ranges is obtained, therefore, the frequency-energy properties of these coefficients are the basis of the method of classification of distortions in the quality of electrical energy. The presented approach to the formation of the system of monitoring the quality of electricity, in contrast to the existing approaches in which sequential processing of the measurement signal to determine individual indicators of quality of electricity, allows building a system of monitoring the quality of electricity in real time.

The development of the digital technology industry, the growing dependence of industry and household consumers on electricity, and the world’s entry into the fourth industrial revolution (Industry 4.0) are factors in the growing need for smart, efficient and reliable next-generation energy systems. Building a new generation of smart grids (“Smart grid”) involves the use of advanced information, communication and computing technologies to ensure the flexibility and efficiency of the grid at all stages of electricity from its production to consumption. It should also be borne in mind that the main purpose of electrical systems in general and electrical networks in particular is to meet the needs of consumers to ensure a sufficiently stable and reliable supply of electricity. Stable and reliable supply of electricity caused by power outages is generally undesirable, and in some cases can lead to very unpleasant consequences—disruption of communication systems, shutdown of technological processes of industrial enterprises, the impossibility of normal living conditions and activities of the population. To prevent this, special measures using for during the design and operation of electrical networks and systems to improve the operation of all their elements and increase the reliability of electricity supply to consumers. One of the key measures is the construction of backup systems, the use of special protection devices and automation, more careful supervision of electrical installations during their operation, etc. All this requires significant of biggest capital investment for energy industry. In many cases, in existing electrical networks, it is advisable to use factual monitoring tools that allow obtaining telemetry data and control and diagnostic parameters from a sufficient number of grid points to ensure automatic power recovery or damage detection to minimize the consequences of failures, localization of damage. Therefore, damage to any element in the electrical network or the system as a whole, there are transients that occur quickly. The mode parameters are significantly different from the allowable ones. Faults indicators for overhead and cable power lines are an effective means of monitoring that increase the efficiency of locating damage to electrical networks. Faults indicators its tools that allow automatic indication of the damaged section of the line, and used to determine interphase short circuits and SPGFs, detection of stable and unstable damage, depending on the type of neutral in low and medium voltage distribution networks. Therefore, this section of the monograph is devoted to issues related to ensuring the use of faults indicators for LV and MV distribution networks, and was contains:

Consideration and solution of the above issues allowed forming within these work requirements for the use of faults indicators as part smart monitoring system of distribution power network of IPS of Ukraine. Moreover, need to use faults indicators for LV and MV power grid to ensure recovery power supply associated with unplanned interruptions in the operation of electrical networks.

The chapter examines the development problems of specialized tools for mathematical and computer modeling, information technology support for automation of the preparation and decision-making process by appropriate organizational management systems (OMS) with advanced tools for meaningful data processing and user interface of competitive electricity market participants operating in complex relationships and potential risks. The peculiarities of the electricity market functioning are determined, which require advanced computer simulation tools that provide market participants with the opportunity to formulate and accept strategies for their own behavior in different segments of the competitive market. Existing solutions and research in the field of creating modern software tools for modeling, forecasting and optimizing the functioning of energy markets in the world are analyzed. The development direction of such tools is determined and the structural-functional composition of the information technology platform for OMS is proposed, that is represented by the functional components of the preparation and decision-making process to develop a strategy for market participant`s own behavior on its segments. The basics of creating an information technology platform for building decision support systems (DSS) for energy companies as entities/subjects of the electric energy market, a feature of which is a new formalization of the components of the DDM (Data-Dialog-Model) paradigm, are considered. In particular, typical operations of the decision maker interaction in the performance of functional tasks that are interrelated with data processing methods are classified. A unified model of the DSS data structures is proposed, which defines common approaches to representing market entities at all management levels through the selection of their properties and relationships and creation of a unified system of classifiers, reference catalogs that ensure the operation of the entire set of mathematical models of computational and analytical problems that are logically and informationally interconnected between itself according to its intended purpose, input and output data parameters of energy companies on the market, optimization and forecasting algorithms.

The lightning protection system can become a factor in super-powerful electric fields, which is very dangerous for technical means that are located in such field, as example, unmanned aerial vehicles. But it is difficult to predict the cases when lightning strikes the current-carrying parts of electrical equipment. Therefore, it is necessary to have calculations on the distribution of fields during a lightning strike. This chapter presents models of the electric field in the vicinity of long thin wire rods and a model of the distribution of electric fields in the presence of an ionized streamer zone near the lightning top. The processes of corona at the tops of grounded rods, which imitate protected objects and lightning rods, are analyzed. The physical modeling of electromagnetic processes during the development of the corona on rod electrodes with different vertices has been performed.

Increasingly widespread integration of local sources of energy generation and accumulation in electrical distribution systems sharply reduces the efficiency of the traditionally used methods and technical means of their modes of operation control. First of all, this concerns such a popular task as choosing the optimal places of the normally open points in the circuits of distribution networks with objective to minimize loss of electrical energy. In this regard, this paper discusses the possibility, feasibility and efficiency of selective use of remotely controlled switching devices in the distribution networks with an open loop topology. The conditions for the expediency of such switching devices implantation are determined. An algorithm of economically optimal operation of remotely controlled switches is proposed, taking into account their limited switching resource. It is shown that in many cases, in order to achieve the required effect, it is advisable to focus on the so-called «soft open points» technologies, which allow independent optimal control of active and reactive power flows and to coordinate the requirements for ensuring high reliability and for minimization of electrical energy losses. A general approach to the control of the corresponding power electronic equipment is proposed to ensure optimal load flow in the distribution feeder in real time.