Search

The sequential direct start-up of four asynchronous machines (AM) with a capacity of 8 MW each from a 6 kV electrical network is considered. The start-up transient modes that arise in the network as a result of such an AM start-up are investigated, as well as the possible consequences for the network. To facilitate the direct start of AM with a capacity of 8 MW, it is proposed to use a conditional twelve-phase controlled compensating converter, which limits the amount of starting over currents in the network. References 10, figures 6. [ABSTRACT FROM AUTHOR]

The optimal power flow (OPF) in electrical power systems focuses on optimizing objective parameters such as generating costs by altering control factors while remaining within operational restrictions and supply-demand balance. Grid power balance, specifically the upper and lower bounds of generator power exports, and the upper limit of reactive power compensator capacity are all employed as constraints in the optimal power flow problem, and a mathematical model of the problem is developed. The Nutcracker Optimization Algorithm (NOA) is implemented to resolve the optimal power flow issue, which is then assessed an IEEE-30 bus system-The objective functions used for this study encompass generating cost, active power losses, voltage stability, and bus voltage variations. The results were then compared to those obtained using Gray Wolf Optimizer (GWO), Sand Cat Swarm Optimization (SCSO), Whale Optimization Algorithm (WOA), and Dung Beetle Optimizer (DBO). The NOA can indeed deal with the optimal power flow problem, as the simulation results show. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of the efficiency of Soft Open Point (SOP) usage — modern power electronic devices that are integrated into the distribution networks of distribution system operators. SOPs are installed between adjacent feeders instead of traditional normally open disconnectors and are able to perform a number of important functions, such as redistribution of active power between feeders, compensation of reactive power, automatic control of the network structure, which, in turn, leads to increased reliability of electricity supply to consumers, reduction of electricity losses and stabilization of the voltage level in the network. The article proposes a SOP control method for active and reactive power. The control is based on the criterion of the minimum loss of active power, for the implementation of which the indirectly related drops of complex voltages in the connection nodes of the device are used, which enables to improve the accuracy of control and minimize the loss of active power. The results of Soft Open Point modeling in distribution electric networks with a random nature of the load are given. In the course of the study, SOP control algorithms were simulated for active and reactive power for different types of load. In particular, simulations showed that when installing SOP on adjacent feeders, it is possible to achieve a significant reduction in active power losses and stabilize the voltage in the load nodes. The maximum value of voltage losses in the relatively small 4 km long feeders was reduced from 0.16 kV to 0.12 kV by the SOP optimization, and the average power losses were reduced from 5.1 kW to 2.5 kW. The presented results prove the effectiveness of the implementation of SOP for the optimization of distribution electric networks of distribution systems operators in conditions of random nature of loads. [ABSTRACT FROM AUTHOR]

The process, in which the internal voltage with time-varying amplitude and frequency (A/F) regulated by equipment generates the electric network’s terminal power variations, plays a critical role in the system dynamic. For the system dynamic analysis, the relationship between the time-varying A/F and the power response, as well as its characteristics, is required. However, this subject has yet to be emphasized and thoroughly studied due to insufficient attention to the fact that the frequency is time-varying. In traditional power system analysis, since the network’s time constant is often fast enough compared to synchronous generators, the electric network is generally depicted by the static relationship with the assumption of constant frequency, although it is not consistent with the practice of frequency time-varying. Moreover, in the present renewable generation scenario, the fast A/F dynamics of internal voltages can impact the power response, and further the system dynamics. So that adequate investigations around the electric network’s power response in relation to the time-varying A/F are more urgent. Motivated by these considerations, this paper studies the network’s original relationship between the internal voltage’s A/F stimulation and the active/reactive power response, which contains the oscillatory integral problem in math. By using the method of integration by parts, an explicit expression of this relationship is given. Further, a simplified relationship is presented to help understand the dynamic characteristics of the network. Several unusual observations, including the composition and consumption on the line of the active/reactive power in relation to the time-varying A/F, are obtained.

Photovoltaic (PV) systems are electric power systems designed to supply usable solar power by means of photovoltaics, which is the conversion of light into electricity using semiconducting materials. PV systems have gained much attention and are a very attractive energy resource nowadays. The substantial advantage of PV systems is the usage of the most abundant and free energy from the sun. PV systems play an important role in reducing feeder losses, improving voltage profiles and providing ancillary services to local loads. However, large PV grid-connected systems may have a destructive impact on the stability of the electric grid. This is due to the fluctuations of the output AC power generated from the PV systems according to the variations in the solar energy levels. Thus, the electrical distribution system with high penetration of PV systems is subject to performance degradation and instabilities. For that, this project attempts to enhance the integration process of PV systems into electrical grids by analyzing the impact of installing grid-connected PV plants. To accomplish this, an indicative representation of solar irradiation datasets is used for planning and power flow studies of the electric network prior to PV systems installation. Those datasets contain lengthy historical observations of solar energy data, that requires extensive analysis and simulations. To overcome that the lengthy historical datasets are reduced and clustered while preserving the original data characteristics. The resultant clusters can be utilized in the planning stage and simulation studies. Accordingly, studies related to PV systems integration into the electric grid are conducted in an efficient manner, avoiding computing resources and processing times with easier and practical implementation. [ABSTRACT FROM AUTHOR]

Electromagnetic transient processes in a network with a conventionally twelve-phase thyristor compensator designed to adjust the value of the starting transient current of the network in the case of direct start from the network of asynchronous motors of comparable power to the network with a jump-like change in the control angle of the thyristors in the bridges were studied. A comparison was made with such a change in the control angle of thyristors of transient currents in the circuits of a two-bridge controlled thyristor compensator with parallel connection of bridges with transient currents in a conventionally twelve-phase thyristor compensator, where these bridges are switched on in series with each other relative to the supply voltage. The advantages of the technical and economic and mass-dimensional parameters of the conventional twelve-phase converter and its operational characteristics when applied in practice in comparison with analogues are indicated. Ref. 5, fig. 6, table.

The efficiency of an enterprise’s power supply system depends on the quality of electricity and the losses of the latter in electrical networks; both being largely determined by the modes of voltage control and reactive power compensation. In practice, the problems of voltage control and reactive power compensation in power supply systems of industrial enterprises, including electric networks with a voltage of up to 1 kV, as well as 6, 10 kV and higher, are often solved separately. It triggers an irrational use of existing voltage control devices, underutilization of the installed capacity of compensating devices, and affects the voltage control in the electrical networks of the power supply organization. Since voltage management and compensation modes of reactive power are inseparable, they can be correctly determined only with the use of an integrated approach based on technical and economic criteria and taking into account technical requirements and local conditions. This article analyzes the mutual influence of voltage control and reactive power compensation modes in the electrical networks of industrial enterprises from the point of view of ensuring the quality of electricity and minimizing load power losses. The method and results of calculations (on the example of a specific industrial facility) for determining voltage deviations and losses in the electrical network as well as for selecting parameters for voltage control and reactive power compensation are presented. Due to the close relationship of these modes that affect all voltage levels, the effectiveness of measures cannot be ensured without the use of multifunctional devices for controlling the equipment of transformer substations.

In the traditional calculations of the steady-state mode of the electrical network, the dependences of the active resistances of the overhead line wire on the ambient temperature and currents in the branches are not taken into account. However, the temperature is a function of the active power losses, the power losses are a function of the resistance and current, and the resistance is temperature dependent. Therefore, these relations should be related to the traditional equations for stationary regimes. In order to increase the accuracy of steady-state calculations, a temperature correction of the resistance of the branches is required. In this paper, we present a method based on the joint solution of nonlinear equations of the steady-state electric network regime and the thermal balance of the wires of overhead lines. The algorithm and the program of calculation of the steady-state mode of an electric network taking into account dependence of active resistances of a wire of an overhead line on ambient temperature and currents in branches have been developed. The quantitative influence of the load current, wire temperature, wind speed, solar radiation on the active resistance of the wires has been estimated, and the errors in calculating annual variable energy losses have been determined. Numerical experiments were carried out for a 6-node modified version of the IEEE test system and equivalent circuit of 110 kV. The results of the calculations of the steady-state regime on various test circuits showed that the non-account of the temperature dependence of the active resistances might cause errors in power loss for individual loaded lines up to 10 %, and for total losses of the system – up to 30 %. This is unacceptable in simulating the modes of the electric network. The results of simulation of steady-state regimes taking into account the temperature dependence of the resistance of the wires are presented on the example of 6-node and 7-node circuits.

Multi-energy systems (MES) involving networks of different energy carriers can support the balancing of fluctuating renewable generation by co-ordinated joint operation. In this paper, an object-oriented modeling methodology for planning and operations control of MES based on nodal analysis is proposed. The framework provides the modularity to simulate scenarios with varying network configurations. Based on object-oriented programming, classes are formed with regard to common attributes of the network elements. The instances of classes represent physical network elements, such as buses, lines, and power conversion units. The models of the individual network elements involve adjustable and flexible parameters. This is especially advantageous for scenarios with operating-point-dependent efficiencies. The overall framework makes use of a uniform description of the model parameters across the diverse energy carriers. Thus, the methodology is particularly suited for the analysis of MES. The applicability of the modeling framework is demonstrated by two use cases involving a technology campus in Berlin.

Modern conditions for the development of the electric power industry increase the requirements in the field of technical conditions and reliability; thus, in a number of Western countries electric networks are being restructured on the basis of safe, environmentally friendly and reliable composite supports. The article analyzes the structure, design and methods of construction of overhead power lines with composite supports that are more promising than traditional ones. The properties, main characteristics and advantages of materials for the production supports of fiberglass and of wood are considered. The advantages and disadvantages of composite and wooden racks are compared and it is shown that most of the requirements for the supports of overhead power lines are met by composite supports. It is discovered that the existing and promising solutions that enable effective use of composite supports in the construction of an overhead line are quite diverse. Currently, in the electrical networks of Western countries, the most common structural model of the construction of an overhead line is the one the one that alternates composite and wooden supports in a certain sequence. The best option of the use of composite supports along with wood ones is the following ratio: four composite supports to one wooden one (method of construction “4/1”). The advantages of this method of construction of the power line are presented, viz. a significant increase in the mechanical strength of the structure of supports and wires as well as the safety of their maintenance. The results of technical and economic calculation that confirm the advantage of constructing a 10 kV distribution line according to the “4/1” scheme are presented. The implementation of composite supports in the electric networks of the Republic of Belarus in the long term will allow obtaining a tangible financial effect by reducing the cost of operation of the overhead line and because of a significant period of operation of composite racks, which is an undoubted advantage in conditions of the modern market economy.

The aim of this paper is to investigate the sensorless voltage control schemes for the promising wound-rotor brushless doubly-fed induction generator (BDFIG) in both the stand-alone and grid-connected systems. For sensorless target, a new rotor position observer using the space vector flux relations of BDFIG is suggested. The proposed sensorless algorithm does not require any additional observers for obtaining the generator speed by directly detecting the rotor position, which may reduce the cost of the overall control system. For the voltage control purpose, a direct voltage control (DVC) scheme is applied for the stand-alone systems. However, this control strategy did not handle the control of the generated-voltage phase angle and also did not consider the phase sequence issue which are very essential provisions for the smooth connection target in grid-connected applications. Hence, DVC strategy cannot guarantee all the intended provisions for a soft and smooth connection process with the grid side and therefore, an effective grid-synchronization algorithm is proposed. A comprehensive analysis to confirm the functionality of the proposed control strategies is discussed through both simulation and experimental results. The presented study in this paper verifies the efficacy of the proposed schemes for sensorless voltage control target of BDFIG in both the stand-alone and grid-connected applications with a good transient behavior. [ABSTRACT FROM AUTHOR]

Field approaches are employed to develop a mathematical model of a power network section. The facility consists of two electric power subsystems described with ordinary differential equations and presented as concentrated parameter systems connected with a three-phase power supply line, presented as a distributed parameter system. The model of the electric power line is described with partial differential equations. Mathematically, the supply line model is described utilizing a mixed problem with explicitly indefinite boundary conditions. All electromagnetic state equations of the integrated system are introduced in their matrix-vector forms. The equation of the three-phase long supply line is expressed untraditionally as a system of two first-order differential equations as a function of long line voltage. Since the power supply line is part of the integrated system that includes two subsystems, the boundary conditions at the line’s start and end are implicitly defined, avoiding the traditional application of the Dirichlet first-type boundary condition. An expanded system of ordinary differential equations that describe physical processes in both the supply and loading subsystems is used to calculate the boundary conditions. To this end, third-type boundary conditions, or Poincaré’s conditions, serve to describe the wave equation of the electric power line. Such an integrated model of an electric power system helps analyse transient processes across the supply line when the electric power system is switched on and is single-phase short-circuited at the final point of the electric power line. A comparison of computer simulation results with well-known software packages shows a convergence of approx. 96%.

The author considers results of German energetics development during the legislature duration 2014-2017 against the background of transformation of energetics goals on the base of valid statistics. These results are contradicting ones: on the first hand, substitution of hydrocarbon and nuclear fuels with renewable power sources was in progress; but on the other hand, translation of this tendency outside energetics failed. Thus, the tusk to reduce hydrocarbon emission and increase energy efficiency has been hindered. Furthermore, increase of unstable sources of energy generation and mutation of energetics geography require capital-intensive and knowledge-intensive modernization of nets; the low rate of the modernization hampers further increase of renewable power generation. In such circumstances, in spite of the fact that the new grand coalition government has come to power, one may expect a correction of previous course in the energy policy. The author predicts the perspective lines of such alterations.

This article provides insights to the community-level evaluation of post-earthquake fire suppression capability considering the performance of a water network and its dependence on the electric network. The objective is to examine the effects of three parameters on post-earthquake water availability at fire hydrants: water network design, seismic hazard, and electric network dependency scenario. Results show that topology-based and energy-based network performance metrics need to be used in conjunction with water source performance for accurate representation of network behavior. Ignoring explicit dependence of the water network on the electric network may provide inaccurate and unconservative predictions of available water pressure and flow at fire hydrants. This is particularly true for "medium" to "large" seismic events. Additionally, there may be a quantifiable level of dependence that a water network has on power before dependent analysis is necessary, perhaps as simple a metric as total head available from energy-dependent sources. [ABSTRACT FROM AUTHOR]

Resilience and functionality of a community after an extreme event rely on performance of several interdependent systems. Data from historic events show that power network seems to be the most critical lifeline, given the dependency of water, communication, transportation, and gas networks on power. This paper focuses on modeling of the performance of an electric network, after an earthquake, for application in analysis of interdependent systems. The paper proposes a streamlined approach to analyze post-earthquake performance of an electric network to identify regions in a community without power. The proposed approach quantifies damage at the component level using fragilities and a capacity index parameter that measures operability. System level network analysis, based on the capacity of the network, is completed to measure and compare power flow before and after the earthquake. A limiting ratio is defined to identify dark versus bright regions. The procedure is validated for two case studies. [ABSTRACT FROM AUTHOR]

Converting surplus renewable electricity into hydrogen by electrolyzers has been recognized as a promising scheme to reduce renewable energy spillage and to meet the increasing hydrogen demand. However, the scheme is challenged by the inherent spatiotemporal imbalance between renewable energy and hydrogen demand. Seasonal storages and interregional hydrogen supply chains (HSCs) are commonly employed in the literature to eliminate this imbalance, but long-distance hydrogen transportation can be costly. In this paper, we incorporated the electric network (EN) into the HSC for its ability to promptly and economically deliver energy at long distances. The uniform hierarchical time discretization method is utilized to achieve the unified operation of the HSC and the EN. On this basis, an integrated HSC-EN model is elaborated upon to investigate the optimal investment and operation of electrolyzers and storage. Finally, an industrial case in Sichuan province, China is analyzed to illustrate the benefits of incorporating the EN to reduce the investment cost and improve electrolyzers’ utilization. [ABSTRACT FROM AUTHOR]

The rather high distributed generation (DG) ramp-up observed in the world is largely associated with the progress in low-power generation technologies and the measure of state support for renewable energy sources. Distributed generation delivers sustainable development of low electricity demand areas where centralized power supply is too expensive. In Russia, the installed electrical capacity of DG has reached 37 GW and its contribution to the country's electric power industry turns out to be very significant: approximately 13.7%. Moreover, more than half of the available facilities are used as stand-by, peak-load, and seasonal sources of electricity. The technological basis of the DG in the country is thermal power plants. The article considers in detail the possible options for operating DG plants. It is shown that the priority areas for the DG application are areas with low density of electrical loads, including rural and low population areas. The presence of infrastructural restrictions for connecting new consumers to the electrical network favors the use of DG in the centralized power supply zone as well. Prospects for the further DG application in the world are associated with the development of renewable energy and the improvement of electrochemical technologies, primarily electricity storage devices. In Russia, apparently, DG technologies based on fossil fuels will prevail for a long time. The country's great demand for thermal energy will contribute to the widespread use of cogeneration plants. A significant reserve for DG development is the reconstruction of the country's numerous gas boilers in small CHP plants with a potential of 41 GW of electrical capacity. [ABSTRACT FROM AUTHOR]

Method of operation quality evaluation of electric network, comprising renewable sources of energy (RSE) is considered. Integral index that enables to evaluate the impact of RSE on energy losses and its quality as well as balance reliability in electric network is suggested. Mathematical model is constructed, taking into account the assumption that electric network with RSE may be in various operation modes, characterized by different technical economic indices. To determine the integral index of operation quality of electric network with RSE in all possible states tools of Markov processes theory and criterial method are used.

One of the main tasks to be performed when organizing the operation of the energy system is to ensure high-quality and uninterrupted power supply to consumers. Dips, interruptions and voltage surges of the electrical network are the most common causes of malfunctions in industrial plants and damage to household equipment, causing significant economic damage to both consumers and electricity suppliers.

Mean hitting time for random walks on a network, defined as the average of hitting times over all possible pairs of nodes, has found a large variety of applications in many areas. In this paper, we first prove that among all $N$ -node networks, the complete graph has the minimum mean hitting time $N-1$ , which scales linearly with network size. We then study a random walk mobility model with location heterogeneity, modeled by scale-free networks, which are ubiquitous in realistic systems such as P2P networks. For this purpose, we consider random walks on two sparse scale-free small-world networks. By using the connection between random walks and electrical networks, we derive explicit formulas about mean hitting time for both networks, the dominant scaling of which exhibits the same behavior as that of complete graphs. This paper demonstrates that heterogeneous sparse networks can have low-mean hitting time with a behavior similar to that of dense complete graphs, which is instrumental in designing networks, where search is fast between any pair of nodes. [ABSTRACT FROM AUTHOR]

This paper is a sequel to the authors’ previous work wherein an analytical expression was derived for the harmonic sum of squares of natural frequencies of a lossless LC ladder network, which is a widely accepted means to model a single, isolated winding for analyzing impulse behavior. The present paper extends the previous result, so that it is applicable to multiple windings in actual transformers. The complexities of the previous work, viz., inhomogeneity and an exhaustive consideration of inductive coupling are retained, and additionally all possible capacitive couplings are now considered. Furthermore, the topology considered in this paper is generic enough to accommodate inductive branches emerging from any node. To the best of authors’ knowledge, there exists no compact closed-form expression to relate the natural frequencies to the inductances and capacitances for a network having this extent of arbitrariness in topology. The success of this method can be ascribed to careful inspection of the inductance matrix to identify hidden pattern and/or structure, followed by their deft manipulation guided by the basic law of mutual coupling between inductors. Interestingly, even a physical meaning can be assigned to each term of the derived expression, and this is done with the intention of assisting its use to conjure new applications. [ABSTRACT FROM AUTHOR]

To schedule the distributed energy resources (DERs) and smart buildings of a microgrid in an optimal way and consider the uncertainties associated with forecasting data, a two‐stage scheduling framework is proposed in this study. In stage I, a day‐ahead dynamic optimal economic scheduling method is proposed to minimise the daily operating cost of the microgrid. In stage II, a model predictive control based intra‐hour adjustment method is proposed to reschedule the DERs and smart buildings to cope with the uncertainties. A virtual energy storage system is modelled and scheduled as a flexible unit using the inertia of building in both stages. The underlying electric network and the associated power flow and system operational constraints of the microgrid are considered in the proposed scheduling method. Numerical studies demonstrate that the proposed method can reduce the daily operating cost in stage I and smooth the fluctuations of the electric tie‐line power of the microgrid caused by the day‐ahead forecasting errors in stage II. Meanwhile, the fluctuations of the electric tie‐line power with the MPC based strategy are better smoothed compared with the traditional open‐loop and single‐period based optimisation methods, which demonstrates the better performance of the proposed scheduling method in a time‐varying context. [ABSTRACT FROM AUTHOR]

Abstract The recycling of carbon dioxide (CO 2) into synthetic fuels via Power-to-Gas (PtG) could represent an important instrument for achieving the complete decarbonization of the energy sector. To address such issue, this paper calculates the investments in PtG units, grid reinforcements and renewable installations that allow the almost complete recycling of the CO 2 emissions of a countrywide electric power system. Furthermore, this work evaluates the feasibility of gas and electric operations in the new system configuration. The analysis is enabled by coupled gas and electric network modelling. The necessary PtG station installations and overhead line reinforcements are identified via scenario-based cost optimization. Hourly operations of electric power plants are scheduled as a sequence of day-head security-constrained unit commitment problems. A transient gas flow model assesses the capability of the gas network to act as short- and long-term storage of synthetic gas. The developed framework is applied to the electric and gas transmission networks of Great Britain, whose investments and operations are investigated for increasing renewable capacity levels based on the 2030 Gone Green case. Results show that almost complete CO 2 recycling is achieved if the installed renewable capacity is approximately three times as large as the 2030 Gone Green estimates. The investments comprise 114 GW of PtG capacity and the construction of 23 electric parallel lines. Remarkably, gas network operations do not represent a limit to the storage of large amount of synthetic methane. Moreover, PtG stations are preferentially installed at locations with large RES capacity and foster large renewable penetration; only small curtailments occur even for large renewable capacity levels. These results support decision makers by quantifying the techno-economic implications of the presented extensive CO 2 recycling strategy. Highlights • We investigate the techno-economic implications of extensive CO 2 recycling. • Complete CO 2 recycling is achievable via PtG if enough RES power is available. • CO 2 recycling in the British system requires 114 GW of PtG and 23 new power lines. • Gas network operations do not limit the injection of synthetic methane. • The gas infrastructure can serve as long-term energy storage of RES. [ABSTRACT FROM AUTHOR]

Power grid is faced with abnormal operating situations they must deal with exposure to weather factors. In winter, the power lines are exposed to frosts, snow, rain and lightning, and summer heat and sandstorms. In our article, we will look at the influence of weather factors on the network by the summer or the temperature reaches its maximum values using the design of experiments. [ABSTRACT FROM AUTHOR]

This study presents a new method to protect the radial feeders on marine vessels. The proposed protection method is effective against phase–phase (PP) faults and is based on evaluation of the ratio between the negative sequence and positive sequence of the fault currents. It is shown that the magnitude of the introduced ratio increases significantly during the PP fault, hence indicating the fault presence in an electric network. Here, the theoretical background of the new method of protection is firstly discussed, based on which the new protection algorithm is described afterwards. The proposed algorithm is implemented in a programmable digital relay embedded in a hardware‐in‐the‐loop (HIL) test set‐up that emulates a typical maritime feeder using a real‐time digital simulator. The HIL set‐up allows testing of the new protection method under a wide range of faults and network conditions and the experimental results demonstrate its effectiveness in all scenarios conducted. The proposed protection method offers a solution to the protection challenges associated with variability of the short‐circuit currents in radial feeders, advancing in this way the traditional mean of protection in maritime feeders, represented by overcurrent relays. [ABSTRACT FROM AUTHOR]

One of the important problems of efficient function of electric networks containing load nodes of nonlinear character of power consumption is reactive power compensation and maintaining voltage quality in a grid. The commonly used methods for compensation of harmonic currents by filtering devices make it possible to solve the problem in a narrow band of variation of current of a nonlinear load. In the reality stochastic character of power consumption of nonlinear load reveals itself in appropriate changes in harmonic components of voltage and their share in total load current. This could considerably change the magnitude and direction of reactive power flow in a grid and impair the existing processes of reactive power control. The scheme and the algorithm of control of capacitor banks in networks with non-linear load that are based on the use of fuzzy logic software are presented in the article. The results of model experiments analysis of the modes of the harmonic of the power flows on behalf of the 14-nodal scheme recommended by IEEE as well as the schemes of a real grid with powerful traction substation are presented. The mentioned results demonstrate that when harmonic components of voltages exceed normative magnitudes, the use of the proposed algorithm eliminates additional loading on the capacitor banks with higher harmonic currents whereas the control procedure acquires quality, the number of commutations is being reduced, the capacitor battery functions longer and the probability of its malfunction decreases.

Copyright of Technical Electrodynamics / Tekhnichna Elektrodynamika is the property of National Academy of Sciences of Ukraine, Institute of Electrodynamics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the increasing utilization of power electronic equipment in power systems, there has been an increase in the occurrence of oscillatory behavior from unknown sources in recent years. This paper puts forward the concept of electric network resonance stability (ENRS) analysis and tries to classify the above-mentioned oscillations into the category of ENRS. With this method, many complex power system oscillations can be analyzed with the linear network theory, which is mathematically mature. The objective of this paper is to establish a systematic approach to analyze ENRS. By introducing the s-domain nodal admittance matrix (NAM) of the electric network, this paper transforms the judgment of ENRS into the zero-point solution of the determinant of the s-domain NAM. First, the zero-points of the determinant of the s-domain NAM are proved to correspond to the eigenvalues of the system. Then, a systematic approach is proposed to analyze ENRS, which includes the identification of the dominant resonance region and the determination of the key components related to resonance modes. The effectiveness of the proposed approach for analyzing ENRS is illustrated through case studies. [ABSTRACT FROM AUTHOR]

The efficiency of installation of the phase-shifting transformer (PST) in the power supply system of St. Petersburg and the Leningrad Oblast’ is examined, making it possible to execute power flow management within the specified range and limit short-circuit currents to values that do not exceed the breaking capacity of the switching equipment. Its optimal parameters were found, based on analysis of various PST operating modes. Proceeding from this, design calculation of the magnetic core and transformer windings was performed. [ABSTRACT FROM AUTHOR]

State estimation (SE) usually serves as the basic function of the energy management system (EMS). In this paper, we propose an SE approach for EMS of combined heat and electric network (CHEN) that consists of ‘active’ heating networks. The proposed two-stage estimator deals with the time delay of heat power transmission in the pipeline. Test results show that the proposed estimator can track the temperature variation in the heating network well, and has good convergence in both steady and dynamic processes. [ABSTRACT FROM AUTHOR]