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Power Systems, IEEE Transactions on

Issue 4 • Date Nov. 2006

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Displaying Results 1 - 25 of 63
  • Table of contents

    Page(s): c1 - 1470
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    Freely Available from IEEE
  • IEEE Transactions on Power Systems publication information

    Page(s): c2
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  • Efficient Computation of Multivariable Transfer Function Dominant Poles Using Subspace Acceleration

    Page(s): 1471 - 1483
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB) |  | HTML iconHTML  

    This paper describes a new algorithm to compute the dominant poles of a high-order multiple-input multiple-output (MIMO) transfer function. The algorithm, called the Subspace Accelerated MIMO Dominant Pole Algorithm (SAMDP), is able to compute the full set of dominant poles efficiently. SAMDP can be used to produce good modal equivalents automatically. The general algorithm is robust, applicable to both square and nonsquare transfer function matrices, and can easily be tuned to suit different practical system needs View full abstract»

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  • Definition of an Efficient Transmission System Using Cooperative Games Theory

    Page(s): 1484 - 1492
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    Under a context of transmission open access, a methodology to define a common transmission trunk system using economic and technical criteria is proposed. A transmission trunk system is defined as a unique and common system constituted by electrical lines and substations that are economically efficient and necessary to allow the development of an electrical market and the supply of demand in the respective electrical system at a minimum cost and in an efficient manner. The principles of cooperation and interaction between agents that are the base for the cooperative games theory are used. Simple games and the Shapley value approach are used. The proposal responds to the need to identify a common main system, common to supply and demand agents, needed in system open access schemes in electricity markets View full abstract»

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  • Probabilistic Wind Farms Generation Model for Reliability Studies Applied to Brazilian Sites

    Page(s): 1493 - 1501
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    This paper presents a computer model for the probabilistic representation of wind farms generation for reliability studies, which can provide an annual estimation of energy production and calculate several performance indexes. The model combines the stochastic characteristics of wind speed with the operational information of the turbines, such as the failure and repair rates, representing the wind farm by a Markov process. The simulations are made with real time series of wind speed of several Brazilian regions and actual turbine models. The influence of some wind farm and installation site characteristics on the results are evaluated, such as the wind speed statistical clustering technique, the number and type of the turbines, and the failure and repair rates. The results obtained reproduce successfully the behavior of the components considered in the model View full abstract»

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  • Measuring Efficiency of Hydropower Plants in Nepal Using Data Envelopment Analysis

    Page(s): 1502 - 1511
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    This paper evaluates the performance of hydropower plants of Nepal Electricity Authority (NEA) using data envelopment analysis (DEA). Input-oriented DEA models are used for various efficiency measurements. DEA models are solved using general algebraic modeling systems (GAMS). The average technical efficiency of hydropower plants of NEA is found to be around 74%, whereas the scale efficiency of the plants is found to be 71%. Similarly, average overall efficiency is found to be around 50%. Classification based on the sensitivity analysis shows that around 80% of hydropower plants fall under the category of distinctly inefficient plants with base technical efficiency scores below 90%. There are a few hydropower plants like Kaligandaki and Sundarijal that are found to be robustly efficient with technical efficiency scores of 100% for most of the conditions View full abstract»

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  • Managing Price Risk in a Multimarket Environment

    Page(s): 1512 - 1519
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (641 KB) |  | HTML iconHTML  

    In a competitive electricity market, a generation company (Genco) can manage its trading risk through trading electricity among multiple markets such as spot markets and contract markets. The question is how to decide the trading proportion of each market in order to maximize the Genco's profit and minimize the associated risk. Based on the mean-variance portfolio theory, this paper proposes a sequential optimization approach to electric energy allocation between spot and contract markets, taking into consideration the risks of electricity price, congestion charge, and fuel price. Especially, the impact of the fuel market on electric energy allocation is analyzed and simulated with historical data in respect of the electricity market and other fuel markets in the U.S. Simulation results confirm that the proposed analytic approach is consistent with intuition and therefore reasonable and feasible for a Genco to make a trading plan involving risks in an electricity market View full abstract»

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  • Economic Analysis of Establishing Regional Transmission Organization and Standard Market Design in the Southeast

    Page(s): 1520 - 1527
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    With the issue of its Notice of Proposed Rulemaking on Standard Market Design (SMD NOPR) in July 2002, the U.S. Federal Energy Regulatory Commission (FERC) took a major step to ensure consistency in wholesale electricity markets. The SMD NOPR contains the Commission's most definitive guidelines regarding its vision of future competitive wholesale electric markets, their structure, and scope. Regional transmission organizations (RTOs) are at the heart of the order-providing the structure and institutions to support wholesale electricity trade and the management of the nation's transmission grid. Locational marginal pricing (LMP) and congestion revenue rights (CRRs) will be used to manage the operation of the transmission grid. As the geographics of these RTOs will expand across many states and one or more independent system operators (ISOs), the state regulators and ISOs, affected by FERC orders, are particularly interested in the assessment of economic impact in their states and ISO market areas, if these orders were adopted. While one can easily conceptualize the steps required to characterize the economic impact of implementing RTOs and SMD, the modeling and analytical methodology is extremely complex and requires that numerous "reasonable assumptions" be made to approximate the operations of the electric system. Results from a case study are used to illustrate the impact of key assumptions and the inherent imprecision in this type of analysis. These types of issues, modeling, and analytical considerations are relevant for evaluating the impact of changing electricity market structures throughout the world View full abstract»

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  • Ex Post Pricing in the Co-Optimized Energy and Reserve Market

    Page(s): 1528 - 1538
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    This paper discusses an alternative to the ex post pricing model currently under development within ISO New England's (ISO NE) ancillary service market. Since ISO NE's real-time ancillary service market co-optimizes both energy and reserve products, ex post pricing is needed for both energy and reserve. A co-optimization approach for ex post pricing requires defining complex pricing rules and implementing heuristics to ensure consistent binding constraints with the ex ante dispatch. In order to avoid complexity and uncertainty of required heuristics, a new ex post pricing schema is proposed to calculate the ex post energy and reserve prices in a decoupled way while recognizing the coupling effect of energy and reserve. In the proposed approach, ex post energy prices are first computed by incorporating the ex ante marginal opportunity cost of reserve in the energy offer; the ex post reserve prices are then calculated by considering the ex post marginal opportunity cost of energy. This approach simplifies the implementation of ex post pricing rules in the ISO NE market. Numerical examples are presented to further demonstrate the validity of this approach View full abstract»

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  • A Voltage-Behind-Reactance Synchronous Machine Model for the EMTP-Type Solution

    Page(s): 1539 - 1549
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    A full-order, voltage-behind-reactance synchronous machine model has recently been proposed in the literature. This paper extends the voltage-behind-reactance formulation for the electromagnetic transient program (EMTP)-type solution, in which the rotor subsystem is expressed in qd coordinates and the stator subsystem is expressed in abc phase coordinates. The model interface with the nodal-analysis network solution is non-iterative and simultaneous. An example of a single-machine, infinite-bus system shows that the proposed model is more accurate and efficient than several existing EMTP machine models View full abstract»

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  • A Novel Power Injection Model of IPFC for Power Flow Analysis Inclusive of Practical Constraints

    Page(s): 1550 - 1556
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (463 KB) |  | HTML iconHTML  

    This paper describes a novel power injection model (PIM) of interline power flow controller (IPFC) for power flow analysis. In this model, the impedance of the series coupling transformer and the line charging susceptance are all included. In this situation, it is proved that the original structure and symmetry of the admittance matrix can still be kept, and thus, the Jacobian matrix can keep the block-diagonal properties, and sparsity technique can be applied. The IPFC state variables are adjusted simultaneously with the network state variables in order to achieve the specified control targets. Furthermore, the model can take into account the practical constraints of IPFC in Newton power flow. Numerical results based on the IEEE 57-bus and IEEE 300-bus systems are used to demonstrate the effectiveness and performance of the IPFC model View full abstract»

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  • A Probabilistic Approach for Determining the Optimal Amount of Transmission System Usage

    Page(s): 1557 - 1564
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    Over the past decade, electric power systems have been restructured based on different models to introduce competition among market participants. Transmission open access for suppliers and customers is one of the most prevailing unbundling services. Usually, a connection tariff is established based on different market factors, including the actual usage of the transmission network. In Brazil, most vertically integrated companies owned by the federal and state governments were unbundled, and new transmission companies are being created. These companies make their assets available to the independent system operator, designated as Operador Nacional do Sistema Eleacutetrico (ONS). One of the main objectives of ONS is to manage transmission services, over a certain voltage level, to ensure nondiscriminatory access to the grid. All transmission users, including regional distribution companies, pay wheeling transmission charges at each delivery or connection point with the major Brazilian network administrated by ONS. This paper presents a methodology for determining the optimal amount of transmission system usage (ATSU) that must be contracted by a regional distribution company, at each connection point. In the proposed approach, the maximum flow at each connection is represented as a random variable in order to obtain the distribution probability of the transmission charges as a function of the ATSU parameter. Besides providing the optimal amounts to be contracted, the proposed probabilistic methodology allows quantifying the risks of violation of each contract and estimating possible penalties. All methodology development steps are described and illustrated through numerical examples. An application to a typical Brazilian regional distribution company is also discussed View full abstract»

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  • Transmission Network Expansion Planning Considering Uncertainty in Demand

    Page(s): 1565 - 1573
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (222 KB) |  | HTML iconHTML  

    This paper presents two mathematical models and one methodology to solve a transmission network expansion planning problem considering uncertainty in demand. The first model analyzed the uncertainty in the system as a whole; then, this model considers the uncertainty in the total demand of the power system. The second one analyzed the uncertainty in each load bus individually. The methodology used to solve the problem, finds the optimal transmission network expansion plan that allows the power system to operate adequately in an environment with uncertainty. The models presented are solved using a specialized genetic algorithm. The results obtained for several known systems from literature show that cheaper plans can be found satisfying the uncertainty in demand View full abstract»

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  • Method Combining ANNs and Monte Carlo Simulation for the Selection of the Load Shedding Protection Strategies in Autonomous Power Systems

    Page(s): 1574 - 1582
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1096 KB) |  | HTML iconHTML  

    This paper describes an efficient computational methodology that can be used for calculating the appropriate strategy for load shedding protection in autonomous power systems. It extends an existing method that is based on the sequential Monte Carlo simulation approach for comparing alternative strategies by taking into account the amount of load to be shed and the respective risk for the system stability. The extended methodology uses artificial neural networks (ANNs) for determining directly the parameters of the most appropriate load shedding protection strategy. For this purpose, the system inputs are the desirable probabilistic criteria concerning the system security or the amount of customer load interruptions. Using this methodology, the utility engineers can adopt a specific strategy that meets the respective utility criteria. The methodology was tested on a practical power system using a computer simulation for its operation, and the obtained results demonstrate its accuracy and the improved system performance View full abstract»

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  • Hierarchical Multiobjective Optimization for Independent System Operators (ISOs) in Electricity Markets

    Page(s): 1583 - 1591
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (547 KB) |  | HTML iconHTML  

    The creation of competitive electricity markets has increased the complexity of the economics of system operation. Independent system operators (ISOs) perform optimizations based on a market-driven objective function. However, there may be other objectives that the ISO wishes to consider. These objectives are called secondary objectives, as they are dominated by the economic objective. In this paper, a hierarchical multiobjective (HMO) optimization is developed that, through coordinated control of network devices such as phase shifting transformers and series flexible ac transmission systems (FACTS), allows the market objective to be optimized in a global sense, while the secondary objectives are locally optimized. The method is applied to a modified IEEE 30-bus system incorporating a wide-area impact index-minimizing secondary objective. Formulated in this paper, the wide-area impact index accurately measures the effects of parallel flow over multiple lines in a region. Comparisons are made between the HMO's performance with other single and multiple objective optimizations and between the wide-area impact index and traditional parallel flow calculations View full abstract»

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  • On the Quantification of the Network Capacity Deferral Value of Distributed Generation

    Page(s): 1592 - 1599
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (259 KB) |  | HTML iconHTML  

    This paper presents an approach to the quantification of the distribution network capacity deferral value of distributed generation (DG). Besides different technical benefits such as reliability and power quality improvement, there are a number of economic benefits related to DG, the most important of which being the end-user electricity bill reduction capability. However, since the onset of the implementation of these technologies, the potential of DG to defer investments on distribution wires and transformers was soon realized, to the point that "non-wire solutions" are now considered as an alternative to network upgrades. In this work, a first approximation to the capacity deferral benefits brought about by DG is obtained. Such approach can be the starting point towards the development of a framework of credits to the owners of DG that fully and fairly recognize the deferral benefits provided to the utility. The financial performance of investments on these important technologies can be then improved, thus broadening DG as a viable market alternative for customers and utilities View full abstract»

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  • Impact of Fault Level Constraints on the Economic Operation of Power Systems

    Page(s): 1600 - 1607
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    The aim of this paper is to prove that fault levels may have a significant impact on the economic operation of modern power systems. First, we present a simple method for the incorporation of fault level constraints (FLCs) in the optimal power flow (OPF), the main optimization tool for the economic operation of power systems. The constraints imposed by fault levels are converted to simple nonlinear (inequality) constraints, described by variables of the conventional OPF. Most common OPF-solving engines already have the computational capacity to handle numerous nonlinear constraints, such as the ones described by the power balance equations on buses. Therefore, once FLCs are converted to nonlinear constraints described by OPF variables, they can be directly introduced to any optimization process performing the OPF. We applied this enhanced OPF on a simple 12-bus network. The results verified the significant impact fault levels have on the optimum operating point of the power system View full abstract»

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  • Placement of PMUs to Enable Bad Data Detection in State Estimation

    Page(s): 1608 - 1615
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    As the phasor measurement units (PMUs) start populating the substations, their benefits for different power system application functions are being debated. One of these functions is the bad data processing that is commonly integrated into the state estimation. Bad data detection is closely related to the measurement redundancy in that bad data appearing in critical measurements cannot be detected. Such measurements, however, can be transformed into redundant measurements by adding few PMUs at strategic locations. In this paper, it will be shown that with few extra PMUs, the bad data detection and identification capability of a given system can be drastically improved. Description of the placement algorithm is given, and case studies carried out on different size test systems are presented View full abstract»

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  • A New Distribution System Reconfiguration Approach Using Optimum Power Flow and Sensitivity Analysis for Loss Reduction

    Page(s): 1616 - 1623
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (434 KB) |  | HTML iconHTML  

    This paper presents a new approach for distribution system reconfiguration (DSR) based on optimum power flow (OPF) in which the branch statuses (open/close) are represented by continuous functions. In the proposed approach, all branches are initially considered closed, and from the OPF results, a heuristic technique is used to determine the next loop to be broken by opening one switch. Then the list of switches that are candidates to be opened is updated, and the above process is repeated until all loops are broken, making the distribution system radial. This paper includes results and comparisons on test systems utilized in three classical papers published in the technical literature, as well as in a previous paper by the authors. Results obtained on a real large-scale distribution system are also presented View full abstract»

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  • Local Network Power Flow Analysis: An Accuracy Level Comparison for Two Sets of Equations

    Page(s): 1624 - 1629
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    This paper addresses the problem of network power flow analysis by comparing two sets of power flow equations: power flow equations based on Tellegen's theorem and conventional power flow equations. The comparison is based on local performance. A good local performance of power flow equations is important for network planning as network planning requires many thousands of power flow analyses. This paper shows that the equations based on Tellegen's theorem outperform conventional equations when used in a reduced local model, i.e., for a few selected equations. For the same number of equations selected, Tellegen's equations give much more accurate results. Numerical examples are provided View full abstract»

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  • Shapley Game for Expansion Planning of Generating Companies at Many Non-Coincident Criteria

    Page(s): 1630 - 1637
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB) |  | HTML iconHTML  

    Liberalization of electric power systems (EPS) considerably changes and sophisticates solution of the expansion problems and their contents. Akey problem here is to coordinate interests of the subjects involved in the EPS expansion planning. The interests may or may not be directly opposite. Very often, the subjects can benefit by cooperation, which affects the decisions on EPS expansion. The theory of cooperative games can be used to solve the problem of coordinating the interests most efficiently. The approach is exemplified by one and two interacting power supply companies, with several subjects each with their interests and different conditions for system expansion View full abstract»

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  • Service Restoration Methodology for Multiple Fault Case in Distribution Systems

    Page(s): 1638 - 1644
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    Current KEPCO's distribution automation system (DAS) provides a very effective restoration solution for the single fault case but cannot handle multiple faults. This paper proposes a two-step restoration scheme-sequential and simultaneous restoration-for multiple fault cases. Efficiency has been achieved by introduction of restoration performance index (RPI) and load-balancing algorithm. Test results to show effectiveness of the proposed scheme are presented, and field experience of DAS in Korea is described as well View full abstract»

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  • Fuzzy Distribution Power Flow for Weakly Meshed Systems

    Page(s): 1645 - 1652
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    This paper presents a fuzzy distribution power flow (FDPF) for weakly meshed balanced and unbalanced distribution systems. Most of the earlier work in this area is for radial distribution systems. In the proposed method, a matrix similar to Jacobian inverse is directly evaluated, in an efficient manner. The method can handle simultaneous presence of several uncertainties in input variables such as network parameters, load model coefficients, load forecast, and bus shunts. Results have been obtained for two test systems to assess the utility of the proposed method View full abstract»

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  • Power Portfolio Optimization in Deregulated Electricity Markets With Risk Management

    Page(s): 1653 - 1662
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (394 KB) |  | HTML iconHTML  

    In a deregulated electric power system, multiple markets of different time scales exist with various power supply instruments. A load serving entity (LSE) has multiple choices from these instruments to meet its load obligations. In view of the large amount of power involved, the complex market structure, the risks in such volatile markets, the stringent constraints to be satisfied, and the long time horizon, a power portfolio optimization problem is of critical importance for an LSE to serve its load, maximize its profit, and manage its risks. In this paper, a midterm power portfolio optimization problem with risk management is presented. Key instruments are considered, risk terms based on semi-variances of spot market transactions are introduced, and penalties on load obligation violations are added to the objective function to improve algorithm convergence and constraint satisfaction. To overcome the inseparability of the resulting problem, a surrogate optimization framework is developed, enabling a decomposition and coordination approach. Numerical testing results show that our method effectively provides decisions for various instruments to maximize profit and manage risks, and it is computationally efficient View full abstract»

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  • The Formulation of the Optimal Strategies for the Electricity Producers Based on the Particle Swarm Optimization Algorithm

    Page(s): 1663 - 1671
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (375 KB) |  | HTML iconHTML  

    In competitive electricity markets, the producer as a market participant strives to find the optimal supply function with the objective of maximizing his/her producer surplus in the market clearing. The model of the producer surplus maximization is a bilevel mathematical programming problem within which the market clearing is taken into account. By using the deterministic approaches, it is difficult to obtain the global solution of the bilevel optimization problem, even for a single hourly market clearing. This is due to the fact that the objective function of such a problem is not concave, and there are nonlinear complementarity terms introduced by using the KKT conditions to represent the market clearing. When the bilevel optimization problem is modified to consider multiple hourly market clearings, such as to maximize the total producer surplus in one day, solving such a problem is almost intractable. A heuristic approach should be another option. For its simplicity and immunity to the local optimum, the particle swarm optimization (PSO) algorithm is employed in this paper to find the optimal supply function of the electricity producer. Based on the IEEE 30-bus test system, different simulation cases with respect to a single hourly market clearing and a daily market clearing are tested to show the efficiency and robustness of the PSO algorithm. In addition, the parameterization techniques used in formulating the optimal supply function are analyzed based on the simulation results View full abstract»

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Aims & Scope

Covers the requirements, planning, analysis, reliability, operation, and economics of electric generating, transmission, and distribution systems for general industrial, commercial, public, and domestic consumption.

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Meet Our Editors

Editor-in-Chief
Antonio J. Conejo
The Ohio State University