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Highlights • Energy exchanges between interconnected utilities has been performed. • Electric energy production is estimated from different fuel sources. • Oligopolistic energy market models with uncertainty/certainty have been proposed. • The power-flow study verifies the quantitative nature of the energy exchange. Abstract An analysis of estimating the electric energy production from different fuel sources and its exchanges between interconnected utilities has been performed, based on the historical trend of economic growth. We used a model that considers meeting the load by committed generators where capacity weighted availability has been factored in for generating units run by same types of fuel. The focus is on Bangladesh, in particular, studying energy exchanges between its different regions as well as potential international energy trading between selected countries in South East Asia (SEA). Another aspect of the paper is to study the utilization of energy resources with less possible negative environmental impacts. Our model also accommodates the effect of gradual/impulsive changes of energy generation and availability of different energy sources. The estimated values match well with the actual energy generation, as reported in Bangladesh power authority's publication. Based on the evaluated expected energy generation, oligopolistic energy market models with uncertainty/certainty have been proposed here to show the probable trading in private sector, and in the mix of private and public sector utilities. Market models also consider the potential cross-border trading. In addition, a power-flow study has been conducted to verify the quantitative nature of energy exchanges between regions. This analysis is intended to facilitate energy system planners and designers with the necessary tools to predict energy distribution in growing electric power systems. [ABSTRACT FROM AUTHOR]

The identification of topological vulnerabilities is a prerequisite for the study of security analysis. This paper presents a graph-theoretic framework to detect the minimum set of transmission lines interconnecting subnetworks inside of a power network. Moreover, the framework is used to develop a method to classify the criticality of substations. The approach can be used with power transfer distribution factors information to gain an insight about the power system security. Sometimes the power network exhibits high vulnerability related to critical transmission lines interconnecting critical substations from a physical point of view. The quantification of structural properties can provide meaningful information needed to assess and enhance the reliability and security of power system networks. The capabilities for the topological approach are illustrated on two large-scale networks. The proposed approach provides an effective tool for both real-time and offline environments for security analysis and control. [ABSTRACT FROM AUTHOR]

Online extraction and characterization algorithms to the distributed damping factor that can accurately monitoring the transient response in large interconnected power systems has attracted much attention, principally to maximize the multi-area functions in energy control centers. In this paper we present an online estimation algorithm to the distributed damping factor of inter-area electromechanical oscillations in power systems. The method is based on a statistical analysis of multi-area matching patterns (MPs) modes from spatially coupled empirical coefficients, and derived with a network partitioning method by coherent signal blocks into data clusters from the phase domain. This provides a distributed global picture on the modal behavior, which is derived using synchronized-time multi-area signals simultaneously recording from wide-area monitoring schemes (WAMS). For purposes as our multi-area online approach, a sliding data window frame for estimating the distributed damping factor of low-frequency electromechanical oscillations based on Prony and Fourier methods with multiple empirical orthogonal functions (EOFs) analysis is presented. In order to demonstrate the usefulness and adaptivity to obtain an online damping factor estimation and global picture of inter-area electromechanical modes from dynamic oscillations in distributed power systems, the proposed algorithm is applied in detail to the 16 machine-68 bus New England test system. [ABSTRACT FROM AUTHOR]

This paper discusses new criterion for the evaluation of load frequency control (LFC) performance. The proposed LFC performance evaluation is based on a standard deviational ellipse that characterizes a bivariate relationship between the frequency deviation and the area's interchange power variation. The standard deviational ellipse is evaluated using Tyler's maximum-likelihood estimator, which is distribution-free within the family of elliptical distributions. In addition, a target standard deviational ellipse is proposed, using predefined values for a target frequency bound and the area's frequency bias. The presented approach is based on the accordance of the estimated ellipse with the target ellipse, resulting in several grades for the LFC performance. A comparison of the proposed criterion is made with other LFC performance criteria known from the literature. Extensive measurements were applied, and the obtained results show the correctness of the proposed approach. [ABSTRACT FROM AUTHOR]

The tie-line bias control (TBC) method has been widely used in the load frequency control (LFC) of multi-area interconnected systems. However, it should be questioned whether the conventional TBC can still apply to LFC when considering the complication of structures of power systems. LFC, in essence, is to stabilize system frequency/tie-line power by controlling controlled outputs' area control error (ACE). In this paper, relations between LFC control variables and controlled outputs are expressed as a system of equations, based on which an exemplary ring network is studied. Sufficient and necessary conditions for TBC applicability is presented, and a novel LFC mode is proposed for a general ring network where TBC cannot work. Finally, TBC applicability to multi-area systems with general topology is studied, and a general LFC mode is proposed for systems where TBC is not definitely applicable, thus rendering routines that may guide LFC design of future power systems with more complex topologies. [ABSTRACT FROM AUTHOR]

Integration of distributed energy resources in power networks make them interconnected and active. Depending upon the type, short circuit capability and location of distributed energy resource in transmission and distribution systems, design of protection coordination schemes becomes very challenging. Complexity further increases in the design of protection coordination schemes, when penetration effect of these resources reaches to upstream transmission lines and coordination among the distance and over current relays requires a review. The protection coordination scheme discussed in this article monitors the state of power network continuously. Depending upon the operational topology of the network, time dial settings as well as plug settings of over current relays and zone-2 setting of distance relays are selected from pre-optimsed relay group settings. Whenever there is any change in the network fault level either due to change in line parameters or incoming of new distributed energy resource, new relay group settings are communicated to corresponding relays. The proposed protection coordination scheme is implemented in RSCAD software for modified eight bus test bus and modified IEEE14 bus system. It is observed that the proposed protection approach is highly flexible to maintain the coordination among the over current and distance relays. [ABSTRACT FROM AUTHOR]

This paper presents a load frequency control (LFC) design, using both of coefficient diagram method (CDM) and ecological optimal technique (ECO) in a multi-area power system. The proposed controller has been designed to reduce the effect of uncertainties owing to variations in the parameters of governors and turbines as well as load disturbance. Each local area controller is designed independently, such that, stability of the overall closed-loop system is guaranteed. The CDM structure is built on the frequency response model of multi-area power system, and physical constraints of the governors and turbines are considered. Also, the standard Kalman filter technique has been employed to estimate the full states of the system including the area frequency deviation, these states has been employed by the (ECO) state feedback optimal controller to produce the optimal control signal. Digital simulations for three-area power systems are provided to validate the effectiveness of the proposed scheme. From the simulation results, it is shown that, considering the overall closed-loop system performance with the proposed CDM + ECO technique, robustness is demonstrated in the face of uncertainties due to governors, turbines parameters variation and loads disturbances. A performance comparison between the proposed controller, CDM alone, and a classical integral controller (I) scheme is carried out, confirming the superiority of the proposed CDM + ECO technique. [ABSTRACT FROM AUTHOR]

A framework for interconnected multi-microgrids (MMGs) optimal power dispatch at smart distribution grids is introduced with network uncertainties. In proposed work, microgrids (MGs) not only exchange power with main grid, but also operate in interconnected mode to increase network reliability. For each small scale energy resources (SSER) and load, a probabilistic model is applied to determine the optimal power sharing of interconnected MGs with minimum operating cost. The power interchange between MGs and the main grid is regulated based on the total operating cost regarding the sold or purchased power either by MGs or by main grid. The stochastic analysis of network variables is done considering optimization constraints and explained as probability distribution function (PDF) and cumulative distribution function (CDF). The imperialist competitive algorithm (ICA) and particle swarm optimization (PSO) algorithms are applied to optimize the object function, and obtained results are compared with Monte Carlo simulation (MCS) method. The results confirm that the optimal power sharing between MGs and main grid can decrease the operating cost of the smart distribution networks. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study presents the load frequency control of an interconnected two-area power system under deregulated environment with area1 as a thermal system having two generating companies and area2 as hydro-thermal system. Appropriate generation rate constraint, and governor dead band are provided in the areas. Three-degree-of-freedom integral-derivative (3DOF-ID) controllers are used as secondary controllers in the areas whose performance is compared with that of two-degree-of-freedom integral-derivative (2DOF-ID) and single-degree-of-freedom controllers such as integral (I), integral-derivative (ID). Biogeography-based optimisation (BBO) technique is used for simultaneous optimisation of controller gains and electric governor parameters. Analysis of the dynamic responses reveal the superiority of 3DOF-ID controller over I, ID, and 2DOF-ID controllers, in terms of settling time, peak deviation and magnitude of oscillation. Sensitivity analysis proved that, BBO optimised parameters obtained at nominal conditions are robust. 3DOF-ID controller parameters obtained at nominal distribution companies participation matrix (DPM) are healthy enough and not necessary to optimise for change in DPMs. Variation in frequency bias coefficient (B) concludes that the best selection for B is equal to area frequency response characteristics. Similarly, selection of governor speed regulation parameter (R) infers higher value for thermal-system, while hydro-system should be kept comparatively low. [ABSTRACT FROM AUTHOR]

The coordination of directional overcurrent relays is most commonly studied based on a fixed network topology within an interconnected power system. Due to its complexity and non-linearity, the relay coordination is formulated as an optimisation problem. Distribution systems often suffer consequences due to the dynamic changes of network topology and operation of elements. Such changes are for example the inputs and outputs of generators, lines and loads. The consequences are reduction of sensitivity and selectivity of relays. The principal objective of this study is to coordinate the directional overcurrent relays based on adaptive protection scheme. The secondary objective is to present the formulation of ant colony algorithm and a comparison of it with the genetic algorithm. [ABSTRACT FROM AUTHOR]

Die-to-die interconnects linking multiple functional dies in a modern 3-D or 2.5-D IC by micro-bumps could experience resistance increase after certain time of field operation due to parametric defects or aging. To cope with this reliability threat, we present an “on-line transition-time binning method” that aims to continuously detect excessive transition time occurring at a target die-to-die interconnect. Our method attaches a monitor to the termination end of each target interconnect. Any transition (rising or falling) is converted into a pulse-width first, which is then further compared to a dynamically tunable threshold for a binary pass/fail judgment. By multiple runs of transition-time monitoring while sweeping the threshold incrementally, the “transition-time bin” of each target interconnect can be derived and thereby a timing failure threat can be detected by a monitor center before it actually strikes. [ABSTRACT FROM PUBLISHER]

Global earthing systems (GESs), which are created by the interconnection of local earthing systems, should guarantee the absence of dangerous touch voltages. According to international standards, one of the reasons for this safety characteristic of GESs is that medium-voltage and low-voltage grounding systems form a quasi-equipotential area. Typical examples of GESs are in city centers due to the high number of interconnected grounding systems in the area. For this reason, in addition to ground grids, other metallic parts with different primary functions shall be also considered, e.g., water and gas pipes, tramway tracks, and building foundations can modify the electric potential distribution in the area. In this paper, a model based on the Maxwell's subareas method (MaSM) is used to evaluate how buried metallic parts, which are not intentionally connected to ground grids, modify the electric potential on the soil surface. First, the MaSM model is validated with experimental measurements on a simple electrode configuration. The measured voltages are compared with the MaSM results and with the results obtained with a finite-element method model simulated with COMSOL Multiphysics. Then, the simulations are carried out on a realistic urban test case. [ABSTRACT FROM AUTHOR]

Interconnected power systems not only allow to the areas to provide mutual assistance, but also import or export energy with respect to optimize energy resources assessment where, a cost reduction involved in the generation of power required to meet its demand. To determine the required control actions, in the planning and operation stages, it is important to verify the loading margins for both the normal operation and the different conditions of contingencies that may eventually occur. In this paper a continuation power flow that allows obtaining the loading margin and maximum active power transfer considering the area interchange control is proposed. From the results of the IEEE systems (9 and 118 buses), a difference of up to twelve percent in the active power transfer capacity is verified compared to the cases without area interchange control. The method also highlights the effects of the loop flow which occur as a consequence of the existence of parallel paths in the interconnected network. [ABSTRACT FROM AUTHOR]

This letter presents a novel Laplacian spectrum-based approach to directly solve biobjective network partitioning problems. The proposed approach is applied to a typical power system partitioning problem in context of smart grids, where the resultant Pareto front considering two incompatible objectives can adaptively provide useful clustering information for a flexible and distributed system control. This approach has proven to be effective and computationally efficient through a case study of the IEEE 118-bus system. [ABSTRACT FROM AUTHOR]

Interconnected electricity networks, supergrids, are being considered in Europe as a way to help tackle two current global challenges - rapidly increasing energy demands and rising carbon dioxide emissions. As with any new approach, there is a range of risks associated with developing interconnections, not least the availability of surplus electricity for exportation between various candidate countries. While the future is never certain, the process of generating a range of possible capacities for these interconnections should be considered as a necessary precursor for mitigating risks within decision-making processes. In facilitating this objective, this paper proposes a step-wise methodological framework for assessing the probabilities of achieving surplus capacity provision within a UK pan-European supergrid. This includes application of a newly developed tool for proposing a range of energy supply/demand scenarios in conjunction with the @Risk assessment tool. Through example scenarios it is shown how P80 (80th percentile) interconnection capacities for 2030 can be assessed. The results suggest that, of the nine candidate countries, Germany could provide the greatest (10ṡ97 GW) surplus capacity with an 80% chance. It is concluded that, with further stakeholder engagement, the developed framework will provide a deeper understanding of the key fundamental risks associated with interconnections as well as mitigation measures. [ABSTRACT FROM AUTHOR]

In order to optimize hydro power plants generator scheduling according to 24-h system demand, a parallel self-adaptive differential evolution algorithm has been applied. The proposed algorithm presents a novel approach to considering the multi-population and utilization of the preselection step for the improvements of the algorithm's global search capabilities. A preselection step with the best, middle, and worst populations' individuals establishes the new trial vectors. This algorithm has been verified on two different models. The first one consists of eight power plants with real parameters, and the second one consists of four power plants, mostly used as a test model in scientific papers. The main goal of the optimization process is to satisfy system demand for 24 h with a decreased usage of water quantity per electrical energy unit. The initial and final states of the reservoirs must also be satisfied. [ABSTRACT FROM PUBLISHER]

This paper proposes a new model reduction algorithm for power systems based on an extension of balanced truncation. The algorithm is applicable to power systems which are divided into a study area which requires a high-fidelity model and an external area, making up most of the power system, which is to be reduced. The division of the power system can be made arbitrarily and does not rely on the identification of coherent generators. The proposed algorithm yields a reduced order system with a full nonlinear description of the study area and a reduced linear model of the external area. [ABSTRACT FROM PUBLISHER]

Many important issues of power system dynamics are often studied by looking at the dynamic responses of generators connected through the power grid, taking their interactions into consideration. In this paper, we present a specific study on the significant impact of grid structure on the power system dynamics with quantitative evidence. Specifically, it is found that the impact of grid structure heavily depends on two types of grid-structure-related variables: 1) electrical distances among the generator internal buses, and 2) electrical distances between the generator internal buses and the faulted bus. Furthermore, with the examples of coherency identification problem, the significance of grid structure is demonstrated by the strong agreement of identification results between using a set of criteria that only takes into account the grid-structure-related variables and dynamic simulations. [ABSTRACT FROM PUBLISHER]

A new method on static external equivalent network is proposed. The method represents the equivalence of different component types and ensures the consistency of both power flow states and sensitivities of variables in the internal network before and after equivalence. Compared to the existing equivalent methods that only consider the power flow state consistency but ignore component particularity representation and sensitivity consistency, the proposed method is more accurate and effective. The simulation results of the 39-bus system and an actual 661-bus utility system demonstrate the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

Energy management systems for the operation of distributed energy resources, distribution storage devices, and responsive loads will be embedded in distribution management systems (DMSs) as advanced functions that rely on accurate input data and fast communication signals. For a proper DMS design, the impact of the state estimation uncertainties and of the communication system delays should be evaluated. The paper presents an integrated software package for the cyber-physical simulation of DMS taking into account the accuracy of state estimation and measurements. The effectiveness of a wireless Wi-Max communication system has been tested on the rural Italian representative network produced by the research project ATLANTIDE. Results proved the need of cosimulation packages in modern distribution systems. [ABSTRACT FROM PUBLISHER]

This paper focuses on the relatively unexplored subject of creating limit-preserving equivalents (LPEs). There is a push to develop LPEs for power system interconnections to be used in markets and reliability studies. The equivalents that exist for these interconnections do not capture thermal limits of equivalent lines, which results in their transmission limits being significantly different from the original interconnection limits. Assigning noninfinite and nonzero limits to equivalent lines is the niche of this paper. This is done by considering an unloaded network, which is operating point independent. A solution method is developed and discussed, which is capable of assigning lower, best, and upper estimates for equivalent line limits and is proposed for use towards developing LPEs. [ABSTRACT FROM PUBLISHER]

Abstract: Islanding detection of distributed generations (DGs) is one of the most important aspects of interconnecting DGs to the distribution system. Islanding detection techniques can generally be classified as remote methods, which are associated with islanding detection on the utility sides, and local methods, which are associated with islanding detection on the DG side. This paper presents a survey of various islanding detection techniques and their advantages and disadvantages. The paper focused on islanding detection using a conventional and intelligent technique. A summary table that compares and contrasts the existing methods is also presented. [Copyright &y& Elsevier]

Monitoring and supervision is an important aspect in view of security of an interconnected power system. The work presented here gives a comparison of various advanced state estimation techniques for optimal placement of Phasor Measurement Units in Power Networks. These techniques meet two requirements i.e. to ensure the complete system observability and at the same time find the optimal locations of Phasor Measurement Units with the minimum cost. The problem is formulated as a mono-objective optimization problem and its resolution is made by implementing seven algorithms which are mentioned in this paper. The proposed algorithms are demonstrated using five test networks that include a practical system. The simulation results ensure the complete system observability. [ABSTRACT FROM AUTHOR]

Variable energy resources (VERs) are growing in the Western Interconnect. To backstop the associated intermittency, the grid needs more firm energy or transmission increased. The low utilization rate of natural-gas-fired generation appears to be preferred over new transmission infrastructure. New ancillary markets may be required to mitigate reliability issues. [Copyright &y& Elsevier]

Abstract: Under-Frequency Load Shedding (UFLS) is a common technique to maintain power system stability by removing the overload in some part of the system. The existing UFLS schemes operate successfully in the interconnected grid system. A particular approach of UFLS scheme is required for an islanded system which is known to be not as strong as the grid. This paper presents a new approach of UFLS scheme for the implementation in an islanded distribution system. The scheme is based on a combination of adaptive and intelligent techniques. The disturbance magnitude for response based and event based is treated differently: (1) event based is based on the power imbalance and (2) response based is based on the swing equation which relies on the frequency and rate of change of frequency measurement. Dynamic simulation on an intentional islanding operation is performed on an existing Malaysian network interconnected with a mini hydro generation. The objective is to investigate the effectiveness of the proposed scheme. The simulation results demonstrate that the proposed scheme is capable of improving the frequency response of the islanded system. A significant finding is that the scheme can successfully reduce the effect of power deficiency following the grid connected to islanding operation transition. [Copyright &y& Elsevier]

Abstract: This paper calls attention to the core issue as to the multi-area generation scheduling algorithm in interconnected electric power systems. This algorithm consists in deciding upon on/off states of generating units and their power outputs to meet the demands of customers under the consideration of operational technical constraints and transmission networks while keeping the generation cost to a minimum. In treating the mixed integer nonlinear programming (MINLP) problem, the generalized Benders decomposition (GBD) is applied to simply decouple a primal problem into a unit commitment (UC) master problem and inter-temporal optimal power flow (OPF) sub-problems. Most prominent in this work is that the alternating direction method (ADM) is introduced to accomplish the regional decomposition that allows efficient distributed solutions of OPF. Especially, the proposed distributed scheme whose effectiveness is clearly illustrated on a numerical example can find the most economic dispatch schedule incorporated with power transactions on a short-term basis where utilities are less inclined to pool knowledge about their systems or to telemeter measured system and cost data to the common system operator and nevertheless the gains from trade such as economy interchange are vital as well. [Copyright &y& Elsevier]

Purpose – High-density interconnect (HDI) continues to be the fastest growing segment of the printed circuit board (PCB) market. The purpose of this paper is to discuss the differences in designing HDI compared to conventional PCB multilayers. This is important for the challenging aspects of very high-speed electronics that require care to control signal integrity and power integrity. Design/methodology/approach – Eight new design principles were studied and illustrated with emphasis on how these differ from conventional PCB design. Findings – HDI implementation can be improved 2X to 4X by employing these new design principles. Densities from 6-12 in. per sq. inch to 18-48 in. per sq. inch have been reported. Design time reductions of 50 percent and cost reductions of 30 percent were also seen. Research limitations/implications – This work was focused on the basic design principles and does not address electronics design automation tools or specific design steps. PCB design is a complex activity and readers are encouraged to obtain and use the references cited. Originality/value – The paper describes various design and layout procedures that the authors have learned over the last 29 years involved in printed circuit design and fabrication. These principles can be combined with other innovations to enable a much more beneficial use of HDI technologies. [ABSTRACT FROM AUTHOR]

Abstract: A novel multiobjective, multiarea and multistage model to long-term expansion planning of integrated generation and transmission corridors incorporating sustainable energy developing is presented in this paper. The proposed MESEDES model is a “bottom-up” energy model which considers the electricity generation/transmission value-chain, i.e., power generation alternatives including renewables, nuclear and traditional thermal generation along with transmission corridors. The model decides the optimal location and timing of the electricity generation/transmission abroad the multistage planning horizon. The proposed model considers three objectives belonging to sustainable energy development criteria such as: (a) the minimization of investments and operation costs of power generation, transmission corridors, energy efficiency (demand side management (DSM) programs) considering CO2 capture technologies; (b) minimization of Life-Cycle Greenhouse Gas Emissions (GHG); and (c) maximization of the diversification of electricity generation mix. The proposed model consider aspects of the carbon abatement policy under the CDM – Clean Development Mechanism or European Union Greenhouse Gas Emission Trading Scheme. A case study is used to illustrate the proposed framework. [ABSTRACT FROM AUTHOR]

Dynamic regulation models for voltage-sourced converter (VSC) based flexible ac transmission system (FACTS) controllers are described in this paper. The dynamic models can then be used to analyze these FACTS controller's capability to improve the capability of a power transfer path. The contributions of this paper include showing that the benefits of FACTS controllers are proportional to the MVA ratings and the benefits of multiple FACTS controllers are cumulative. Furthermore, the coupling of dc buses allowing active power circulation between multiple VSC FACTS controllers may offer additional improvement in transfer capability. [ABSTRACT FROM AUTHOR]

This paper presents a procedure to study the dynamics of the frequency of the interconnected system Ecuador-Colombia when a generation unit comes out of the system, and when one doesn't have the necessary information of the electric Colombian system, furthermore the paper presents the results obtained when this procedure is applying it to a real example. [ABSTRACT FROM AUTHOR]

In this paper two power elements for power controller in transmission line are presented: Variable Frequency Transformer (VFT) and Rotary Power Flow Controller (RPFC). In addition, here a new Optimal Power Flow (OPF) with these elements is presented. In this paper, it has been made use of the Impedance and Admittance nonsymmetrical matrix and the matrix of loss or coefficient B are calculated in a new method. It has also been indicated that the system is not optimized if optimal power flow is not considered in locating and power of flow controller in line. The proposed method was applied to a 26-bus and 6-generator system and the results were satisfactory. [ABSTRACT FROM AUTHOR]

Optimal reactive power dispatch problem in power systems has thrown a growing influence on secure and economical operation of power systems. However, this issue is well known as a nonlinear, multimodal and mixed-variable problem. In the last decades, computation intelligence-based techniques, such as genetic algorithms (GAs), differential evolution (DE) algorithms and particle swarm optimization (PSO) algorithms, etc., have often been used for this aim. In this work, a seeker optimization algorithm (SOA).based reactive power dispatch method is proposed. The SOA is based on the concept of simulating the act of human searching, where the search direction is based on the empirical gradient by evaluating the response to the position changes and the step length is based on uncertainty reasoning by using a simple Fuzzy rule. In this study, the algorithm's performance is evaluated on benchmark function optimization. Then, the SOA is applied to optimal reactive power dispatch on standard IEEE 57- and 118-bus power systems, and compared with conventional nonlinear programming method, two versions of GAs, three versions of DE algorithms and four versions of PSO algorithms. The simulation results show that the proposed approach is superior to the other listed algorithms and can be efficiently used for optimal reactive power dispatch. [ABSTRACT FROM AUTHOR]

Multistage Benders decomposition (MSBD), also known as dual dynamic programming, is a well-established technique to solve hydrothermal scheduling problems, especially for predominantly hydro systems. The MSBD methodology solves the problem by iterative forward and backward recursions, approximating the cost-to-go function for each stage by Benders cuts, as opposed to traditional dynamic programming approaches that discretize the state space at each time-step. The classical definition of the stages in the MSBD approach is to assign a stage for each time period. In this paper, we propose a new strategy to decompose the problem, where each stage comprises all variables and constraints of several time periods. Numerical results of the application of this strategy to the short- term hydrothermal scheduling problem confirm the advantages of this strategy in terms of CPU time, as compared to the classical stage definition approach. We show that there is an "optimal aggregation factor," which best balances the trade-off between solving a "larger number of shorter subproblems" and solving a "smaller number of larger subproblems." The primal and dual solutions related to different aggregation factors are also compared, and the stability of the results is confirmed. Extensions of the proposed strategy to stochastic problems are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a model for the simulation of the optimal medium-term operation of a hydrothermal system. System stochastic parameters are modeled by Monte Carlo scenarios, which are solved on distributed processors. For each scenario a yearly hydrothermal scheduling (HTS) problem with hourly time resolution is formulated and solved as a large mixed integer linear program (MILP). HTS modeling includes unit commitment, start-up costs and minimum up/down time constraints. The model is applied to the Greek Power System, comprising 29 thermal units and 13 hydroplants; 100 simulation scenarios are generated and solved on 18 distributed processors. Test results include both medium-term objectives, such as reservoir water management, and short-term decisions such thermal unit start-up decisions. [ABSTRACT FROM AUTHOR]

An in-depth analysis of lossless reciprocal periodic structures of transmission lines (TLs) is presented. Interestingly, it is found that periodic structures can provide both non-negative (NNCR) and negative characteristic resistances (NCR). In addition, the magnitude of the voltage reflection coefficient associated with an equivalent model of periodic structures terminated with passive loads can be less than or equal to unity for the NNCR case, and can exceed unity and even approach infinity for the NCR case. However, associated powers are still conserved for both cases. Furthermore, an alternative derivation based on short- and open-circuited terminations for determining characteristic impedances and propagation constant of equivalent TLs is also introduced. An example of finite periodic TL structures, providing both NNCR and NCR cases, with varying the number of unit cells is also given. In addition, implementation and measurement are set up to verify theoretical and simulated results. It is found that these results are reasonably in good agreement. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents the status of electricity transmission grids in the Energy Community of South East Europe (ECSEE): Albania, Bosnia–Herzegovina, Bulgaria, Croatia, Macedonia, Montenegro, Romania, Serbia, UNM in Kosovo. It overviews political and legal aspects of transmission, explaining the impact of the Energy Community Treaty and of the acquis communautaire on energy on the transmission sector. It summarizes the status and the capacity of the interconnections among countries and the current level of cross-border electricity trades. It discusses the need and criteria for electricity transmission investments in the ECSEE. [Copyright &y& Elsevier]

A spectral transmission-line method (TLM) is developed for computing dispersion diagrams and eigenmodes of photonic-bandgap structures. By terminating the unit cell with periodic boundary conditions and allowing complex-valued voltages on the mesh, the system's modes may be found as solutions to an elgenvalue equation describing the system at steady state. A combination of sparse matrix techniques that exploit the spectral properties of the TLM scattering matrices enable efficient calculations despite the dimensionality of the eigenvalue equation. In contrast to conventional applications of the TLM, this formulation does not require selection of arbitrary mesh points to compute band diagrams and produces eigenmodes directly from band structure calculations without requiring a time history of the entire mesh and its Fourier transform, or additional frequency-domain computation. [ABSTRACT FROM AUTHOR]

The unit commitment is one of the most important problems in power system operation. Restructured power system operation is performed as a single area in most countries. In this environment, GENCOs compete in order to contribute in power market. Generation scheduling in a power system considers network security constraints and system's reliability indices. Hence, economic operation of the network is in the second preference. One of the methods to enhance the reliability of a power system is incorporating the adjacent units through tie-lines, in this paper, security constrained unit commitment problem of interconnected power systems is modeled and the results are evaluated using the IEEE 118-bus network. [ABSTRACT FROM AUTHOR]

The Lungmen Nuclear Power Project (LMNPP), under construction in Taiwan, consists of two GE Advanced Boiling Water Reactor (ABWR) units, each with 1350 MW electrical output. Major Human-System Interfaces (HSIs) of LMNPP are different from traditional operating BWRs or ABWRs. Video display units (VDUs) are the main human-system interface for operators to manipulate and to know the status of the equipment and plant information. Based upon NUREG-0711, the applicable human factors engineering (HFE) guideline in the design of HSIs has been adopted. An important aspect of the Lungmen HFE program has been the direct involvement of the end user, Taiwan Power Company (TPC), throughout the design development and implementation to ensure that the process for the design is compliant with the HFE principles, and that the necessary displays, control, and alarms are provided to support the identified personnel tasks. This paper reviews the applicable HFE principles and the HSI design process including verification and validation (V&V) process in the design of HSIs for the LMNPP. This paper also presents three topics of interest in the LMNPP HSI design development and implementation process-validation with simulator, alarm auto reset, and VDU operational configuration strategy. The objective for developing the VDU operational configuration strategy was, after appropriate V&V, to reinforce operation discipline and optimize operator crew task assignments and workload during typical operations, and to confirm the need for an intensive training program that addresses the knowledge and skill requirements of the operators to meet the task characteristics and the responses of the plant processes. The results to date and implications for going forward from this process are also presented. [ABSTRACT FROM AUTHOR]

This paper presents a computational approach for an offline measurement-based design of an optimal damping controller using adaptive critics for a new type of flexible ac transmission system device--the gate-controlled series capacitor (GCSC). Remote measurements are provided to the controller to damp out system modes. The optimal controller is developed based on the heuristic dynamic programming (HDP) approach. Three multilayer-perceptron neural networks are used in the design--the identifier/model network to identify the dynamics of the power system, the critic network to evaluate the performance of the damping controller, and the controller network to provide optimal damping. This measurement-based technique provides an alternative to the classical linear model-based optimal control design. The eigenvalue analysis of the closed-loop system is performed with time-domain responses using the Prony method. An analysis of the simulation results shows potential of the HDP-based optimal damping controller on a GCSC for enhancing the stability of the power system. [ABSTRACT FROM AUTHOR]

Advanced communication technologies have allowed the power-line-communication (PLC) channel to be a transmission medium that enables the transfer of high-speed digital data over the classical indoor electrical wires. The development of PLC systems for Internet, voice, and data services requires measurement-based models of the transfer characteristics of the mains network suitable for performance analysis by simulation. This paper presents a deterministic model describing the magnitude and phase of complex transfer functions of power-line networks using only one parameter. First, a PLC channel classification is realized, and an average magnitude and phase channel model by class is proposed. Second, the multipath characteristic of PLC channels is introduced. A statistical-based channel magnitude generator is built, and a group delay-based phase model is suggested. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a framework for assessing information security in power communication systems. The framework consists of dividing the communication system to be analyzed into its subcomponents and linking these to relevant evaluation criteria. In this study, the information security standard ISO 17799 has been used as a point of reference to define such evaluation criteria. The framework involves collecting data to evaluate each individual criterion and aggregating these evaluations using a robust algorithm. To cater for the many uncertainties in evaluating information security, the evaluation of the individual subcomponents is aggregated using a Dempster-Shafer based algorithm for evidential reasoning. This algorithm incorporates the many insecure facts and incomplete data that are inherent in large scale systems. The overall result is a set of indicators which highlight the level of information security within a studied communication system. The paper is concluded with a description of a case study in which the framework was applied to a communication system used for automatic meter reading (AMR). Experiences from this application are described in the paper. [ABSTRACT FROM AUTHOR]

Flexible ac transmission systems (FACTS) devices are attracting an increasing interest both in power system academic research and in electric utilities for their capabilities to improve steady-state performance as well as system stability. Several converter topologies for FACTS applications have been proposed in the recent literature, even if those based upon voltage source inverters (VSI) seem to be more attractive due to their intrinsic capability to rapidly respond to network changes such as perturbations subsequent to a fault and their property of being immune to resonance problem. In this paper, a new topology for inverter-based FACTS is proposed. This configuration, employing a two-leg three-phase inverter is employed for both series and parallel-connected reactive power compensators. The converter utilizes a modular topology for allowing a satisfaction of electronic components rating. A control strategy based on variable structure control technique with sliding mode is employed to track appropriate reference quantities. Design and control, as well as good tracking performances, are also verified through numerical simulations. [ABSTRACT FROM AUTHOR]

This paper first analyzes the electrical parameters of differential-mode (DM) and common-mode (CM) propagation on power interconnects. The impedance-transformation effects of the power interconnects are then investigated. The interactions between the parasitic parameters in electromagnetic-interference (EMI) filters and the transformed impedances by the power interconnects are explored in detail. It is found that the interactions can degrade EMI-filter performance at high frequencies. Simulations and experiments are finally carried out to verify the analysis. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, an indirect modeling approach for static synchronous series compensator (SSSC) is proposed for Newton power flow analysis. This model shows that addition of ‘p’ SSSCs to an existing ‘n’ bus power system can be represented as an equivalent ‘(n + p)’ bus power system, without any SSSC. As a result, standard power flow analysis of the ‘(n + p)’ bus system can be carried out to calculate the steady state operating point of the original system containing SSSCs. Absence of any SSSC in the transformed system eliminates the need of writing new codes for computing the power flow equations and the Jacobian elements pertaining to SSSCs. This results in a substantial reduction in the programming complexity. The proposed model can also easily account for converter switching losses and various practical device constraints. Application of the proposed model for multiple SSSCs in the IEEE 30-bus, IEEE 118-bus and IEEE 300-bus systems demonstrates the feasibility of the model and its excellent convergence characteristics. [Copyright &y& Elsevier]