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Power Systems, IEEE Transactions on

Issue 2 • Date May 1999

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Displaying Results 1 - 25 of 57
  • A hybrid fuzzy, neural network bus load modeling and predication

    Page(s): 718 - 724
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    A hybrid approach utilizing a fuzzy system and artificial neural network for bus load forecasting is proposed in this paper. This approach models the behavior of load on those areas where it is primarily a function of temperature. Load sequences were broken down into a nonweather sensitive, normal load sequence and a pure weather sensitive load sequence. It has been shown that normal load has a stationary characteristic and can be modeled by back propagation neural networks. The weather sensitive load has been modeled by a set of three fuzzy logic systems trained by least square estimation of an optimal fuzzy basis function coefficient. The model was tested with 1994 historical data from the town of Hinton, West Virginia (part of the Appalachian Power Company). The results show an average MAPE (mean absolute percentage error) of 2%, which is comparable with system load forecasting methods reported in the literature View full abstract»

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  • Optimal dispatch under transmission contracts

    Page(s): 732 - 737
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    Open transmission access is now the most topical issue in power system deregulation. Power system operation poses the greatest challenge to a competitive environment incorporating open transmission access and there are some fundamental operational problems that are still unresolved. This paper seeks to provide an approach to the power dispatch problem in a structure dominated by bilateral and multilateral transmission contracts. A framework for price-based operation under these conditions is developed and a methodology for optimal transmission dispatch is proposed. The case study results illustrate that the proposed market arrangement and operating mechanisms are compatible with this new business environment View full abstract»

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  • Optimal active power flow incorporating power flow control needs in flexible AC transmission systems

    Page(s): 738 - 744
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    This paper presents a new method to incorporate the power flow control needs of flexible AC transmission system (FACTS) in studying the optimal active power flow problem. The linearized (DC) network model is used in this paper. Three main types of FACTS devices, namely thyristor controlled series compensators (TCSC), thyristor controlled phase shifters (TCPS) and unified power flow controllers (UPFC), are considered. The proposed method decomposes the solution of such modified OPF problem into two problems' iteration. The first problem is a power flow control subproblem while the second problem is a normal OPF problem. It is shown that the modified active power OFF can be solved by a new iterative strategy where a conventional LP-based technique may be used. Digital simulation studies on the IEEE 30 bus test system are presented to show the effectiveness of the proposed method View full abstract»

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  • Decision analysis tools for GENCO dispatchers

    Page(s): 745 - 750
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    This paper outlines a decision analysis procedure to guide dispatchers in applying corporate policy for economic decisions when risk is involved. These techniques enable dispatchers to implement corporate policies without waiting for an answer from another group or groups within accepted guidelines. The intent of the procedure is to reduce the guidelines to expert system rules, which may be applied without extensive analysis. Such a set of tools is often used in other industries by administrative staff instead of engineering staff. Tools such as the one reported here are needed for the new business environment for profit opportunities to be achieved while maintaining security. The tool described within this paper was designed for a mid-western generation company to handle reserve or contingent contract requests View full abstract»

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  • Noniterative synchronous machine parameter identification from frequency response tests

    Page(s): 553 - 560
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    In this paper, a method to identify synchronous machine parameters from standstill frequency response tests is presented. It is common practice to use iterative techniques first to match a set of time constants with the measured response, and then to solve a set of nonlinear equations to obtain the equivalent circuit parameters. However, there is a difficulty of specifying an initial parameter estimate before any iterations can commence. This problem is overcome by the method presented here, which is able to approximate machine parameters straightforwardly and without the need of iterating. It was found that the transfer functions produced by the calculated parameters very closely resemble the measured frequency responses. Should refinements of the solution become necessary, the obtained parameters will still serve as an excellent initial estimate for standard curve fitting procedures View full abstract»

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  • Power system state scheduling with the two-stage problem

    Page(s): 439 - 445
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    Traditional statements of optimization problems in power system state scheduling lead to complexities at the on-line correction of variables. This paper considers a stochastic optimization problem with corrective functions of the given analytical type. The problem solution gives scheduled values of the state variables and the adjustment coefficients for corrective functions. The corrective functions represent a response of the control system to the unforeseen deviations in operation conditions. The preliminarily obtained coefficients of corrective functions allow a very easy and quick organization of the on-line optimal state correction. Dual variables of the optimization task can be corrected as well for fast spot price adjustment. A case study demonstrating the efficiency of state control using the suggested approach is considered View full abstract»

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  • Frequency response of prime movers during restoration

    Page(s): 751 - 756
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    In the initial phase of restoration, operators are often concerned with the size of load which can safely be picked-up, and the effectiveness of the generation reserve. There has been a need for a methodology to readily address these concerns by providing simple guidelines to facilitate an orderly power system restoration. In this paper, a simple approach is developed based on an approximate frequency response rate of prime movers for determining: (a) the maximum load pickup within the allowable system frequency dip, and (b) the amount and distribution of reserve for maintaining firm generation View full abstract»

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  • Teaching distribution system reliability evaluation using Monte Carlo simulation

    Page(s): 397 - 403
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    Analytical techniques for distribution system reliability assessment can be effectively used to evaluate the mean values of a wide range of system reliability indices. This approach is usually used when teaching the basic concepts of distribution system reliability evaluation. The mean or expected value, however, does not provide any information on the inherent variability of an index. Appreciation of this inherent variability is an important parameter in comprehending the actual reliability experienced by a customer and should be recognized when teaching distribution system reliability evaluation. This paper presents a time sequential Monte Carlo simulation technique which can be used in complex distribution system evaluation, and describes a computer program developed to implement this technique. General distribution system elements, operating models and radial configurations are considered in the program. The results obtained using both analytical and simulation methods are compared. The mean values and the probability distributions for both load point and system indices are illustrated using a practical test system View full abstract»

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  • Bayesian network model for reliability assessment of power systems

    Page(s): 426 - 432
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    This paper presents an application of Bayesian networks (BN) to the problem of reliability assessment of power systems. Bayesian networks provide a flexible means of representing and reasoning with probabilistic information. Uncertainty and dependencies are easily incorporated in the analysis. Efficient probabilistic inference algorithms in Bayesian networks permit not only computation of the loss of load probability but also answering various probabilistic queries about the system. The advantages of BN models for power system reliability evaluation are demonstrated through examples. Results of a reliability case study of a multi-area test system are also reported View full abstract»

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  • Thermal power generation scheduling by simulated competition

    Page(s): 472 - 477
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    This paper presents a new method for solving the unit commitment problem by simulation of a competitive market where power is traded through a power exchange (PX). Procedures for bidding and market clearing are described. The market clearing process handles the spinning reserve requirements and power balance simultaneously. The method is used on a standard unit commitment problem with minimum up/down times, start-up costs and spinning reserve requirement taken into account. Comparisons with solutions provided by Lagrangian relaxation, genetic algorithms and Chao-an Li's unit decommitment procedure demonstrate the potential benefits of this new method. The motivation for this work was to design a competitive electricity market suitable for thermal generation scheduling. However, performance in simulations of the proposed market has been so good that it is presented here as a solving technique for the unit commitment problem View full abstract»

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  • Competitive procurement of ancillary services by an independent system operator

    Page(s): 498 - 504
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    This paper discusses the competitive procurement of ancillary services by an independent system operator (ISO). The paper assumes the existence of an underlying market for energy and explains why this energy market must be accompanied by a market for ancillary services. These services include operating reserves and automatic generation control (AGC) both of which may require generators that are infra-marginal in the energy market to choose between supplying energy or ancillary services. The paper discusses the design of an auction for these services that has formed the basis for the California ISO's ancillary services market. The paper also discusses the real-time dispatch of ancillary services View full abstract»

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  • A new model for outaging transmission lines in large electric networks

    Page(s): 412 - 418
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    This paper presents a new method for calculating line currents for multiple line outages in large electric networks at extremely high computational speeds. An example is given showing that only one minute of computation time is needed to test 160 k N-3 line outage configurations for a large network. Resulting line overloads are shown to agree well with AC load flow. The new method: (1) calculates line currents and powers for any set of multiple line outages; (2) tests for system separation due to lines outaged; (3) tests for electrical remoteness of lines being outaged; and (4) updates real power line distribution factors used in linear programming and probabilistic models. The method is restricted to passive networks in which tapped transformers are near unity View full abstract»

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  • Integrating research results into a power engineering curriculum

    Page(s): 404 - 411
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    This paper presents summaries of the activities of six research active power engineering educators which were presented in a panel session of the same name at the IEEE Power Engineering Society Winter Meeting on February 3, 1997 in New York City, USA. Each of the panelists discusses how research results are incorporated into courses and how students benefit from this approach View full abstract»

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  • Mitigation of voltage collapse caused by armature current protection

    Page(s): 591 - 599
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    The importance of field current limiter behaviour during voltage instabilities is generally known. A field current limiter will weaken the system by introducing extra reactance. A tripping of the generator by an armature overcurrent relay or the activation of an armature current limiter will severely cripple the power system which often causes the breakdown of the system voltages. One way to alleviate the influence of the armature current protection during the instability is to make small changes in the active power production of the generator and thereby fully utilize the capability of the generator. Depending on the location of the overloaded generator, different actions can be taken to support the critical area as long as sufficient transmission capacity and that active and reactive power reserves are available remotely. This active power rescheduling may also alleviate the influence of a field current limiter. Some simulations are shown for a power system with a radial structure View full abstract»

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  • An Intelligent Data-Acquisition and Control (IDAC) system for energy conversion laboratory

    Page(s): 391 - 396
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    The range of experiments that a typical undergraduate energy conversion laboratory facility can support does not adequately prepare power engineering students for the digital-computer oriented power system industry. Traditional approach to experimentation involves manually reading several meters, logging data, performing necessary calculations and plotting results. In order to correct this problem, an Intelligent Data-Acquisition and Control (IDAC) system is implemented for the energy conversion laboratory at Penn State University, Harrisburg. Using the IDAC system, data gathering and analysis becomes automated. Students are therefore able to devote the bulk of their time to the intellectual aspects of the project View full abstract»

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  • An improved algorithm to aid in post-heat storm restoration

    Page(s): 446 - 451
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    Utilities strive to have quick restoration after a power outage. Extreme conditions, such as storms, create difficult restoration challenges because of the large number of tasks necessary to restore power to many affected customers. Restoration efforts can be further hindered when outage report escalation algorithms predict the wrong location for affected devices. This paper describes a modified topological based algorithm that associates trouble calls with each other to provide more accurate information about outages during heat storms. The heat storm algorithm was tested and verified on two feeders using test cases that simulated the heat storm conditions experienced at Northern States Power Company in Minneapolis, Minnesota in July 1995 View full abstract»

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  • Revenue adequate bidding strategies in competitive electricity markets

    Page(s): 492 - 497
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    Energy trading in a competitive electricity market can be modeled as a two-level optimization. At the top level a centralized economic dispatch (CED) uses a priority list method to solve the fundamental problem of reliable market clearing with price discovery. The lower level consists of a set of decentralized bidding (DB) subproblems. The DB model uses a self-unit scheduling simulator based on parametric dynamic programming to produce hourly bid curves for the central dispatch coordinator. Unit operating constraints and costs such as the unit minimum-up and minimum-down times, ramp rates, and the unit start-up, no-load and sunk capital costs are internalized in the bid curves through the simulator. A special algorithm is presented to solve the revenue adequacy problem for marginal units. Both CED and DB models are based on the revenue maximization in contrast with the cost minimization criteria used in the conventional unit commitment (UC). The proposed method has been tested in a study case and some interesting results have been demonstrated View full abstract»

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  • Application of a multivariable feedback linearization scheme for rotor angle stability and voltage regulation of power systems

    Page(s): 620 - 628
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    This paper investigates the application of a nonlinear controller to the multi-input multi-output model of a system consisting of a hydraulic turbine and a synchronous generator. The controller proposed is based on a feedback linearization scheme. Its main goal is to control the rotor angle as well as the terminal voltage, to improve the system's stability and damping properties under large disturbances and to obtain good post-fault voltage regulation. The response of the system is simulated in the presence of a short-circuit at the terminal of the machine in two different configurations and compared to the performance of a standard IEEE type 1 voltage regulator, PSS and a PID speed regulator View full abstract»

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  • Composite security boundary visualization

    Page(s): 725 - 731
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    Based on a security assessment methodology using automatic training data generation software and neural networks, a composite security boundary visualisation approach is proposed for power system operations. This approach can draw a single continuous boundary given multiple individual security problems. It can be conveniently accessed on-line and can be easily integrated into the energy management system. Examples are given for demonstration of the effectiveness of the proposed approach View full abstract»

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  • Available transfer capability and first order sensitivity

    Page(s): 512 - 518
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    A method of calculating available transfer capability and the exploration of the first order effects of certain power system network variables are described. The Federal Energy Regulatory Commission has ordered that bulk electrical control areas must provide to market participants a “commercially viable” network transfer capability for the import, export and throughput of energy. A practical method for deriving this transfer capability utilizing both linear and nonlinear power flow analysis methods is developed that acknowledges both thermal and voltage system limitations. The available transfer capability is the incremental transfer capability derived by the method reduced by margins. A procedure for quantifying the first order effect of network uncertainties such as load forecast error and simultaneous transfers on the calculated transfer capability of a power system snapshot are explored. The quantification of these network uncertainties can provide information necessary for system operation, planning and energy market participation View full abstract»

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  • Deregulation, privatization, and competition: transmission planning under uncertainty

    Page(s): 460 - 465
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    Competitive markets expose transmission planners to new uncertainties. These are handled using a decision-analysis approach whose key contribution is quantifying and minimizing risk. The method is applied using existing and generally-available software tools. The result is transmission plan which is robust in the face of uncertainties. A study of a major proposed Central-American interconnection illustrates the problem and the method View full abstract»

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  • Short term load forecasting using a self-supervised adaptive neural network

    Page(s): 779 - 784
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    We developed a self-supervised adaptive neural network to perform short term load forecasts (STLF) for a large power system covering a wide service area with several heavy load centers. We used the self-supervised network to extract correlational features from temperature and load data. In using data from the calendar year 1993 as a test case, we found a 0.90 percent error for hour-ahead forecasting and 1.92 percent error for day-ahead forecasting. These levels of error compare favorably with those obtained by other techniques. The algorithm ran in a couple of minutes on a PC containing an Intel Pentium -120 MHz CPU. Since the algorithm included searching the historical database, training the network, and actually performing the forecasts, this approach provides a real-time, portable, and adaptable STLF View full abstract»

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  • The stability of power system markets

    Page(s): 505 - 511
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    Market equilibrium conditions can be derived from more general dynamic equations describing the marketplace. Dynamic equations provide insights into the behavior and stability of markets which are not available from static models. For example, markets with a single supplier with declining linear costs (economies of scale) may or may not be stable, depending on specific cost characteristics. Markets with more than one supplier with declining linear costs are always unstable. This paper illustrates a situation where the removal of congestion makes a market unstable View full abstract»

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  • Augmented Hopfield network for constrained generator scheduling

    Page(s): 765 - 771
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    Many scheduling algorithms do not incorporate all the physical constraints of the problem. However, as their operational environments change many power systems are operated closer to physical limits and scheduling algorithms that consider all constraints are required. This paper presents an augmented Hopfield neural network scheduling algorithm that unifies the unit commitment and generation dispatch functions. This algorithm successfully considers ramp rate, transmission and fuel constraints in addition to the more common constraints. Results show that feasible solutions can be obtained in highly constrained circumstances View full abstract»

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  • On-off control of an active load for power system damping-theory and field test

    Page(s): 608 - 613
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    Controlled resistive loads can contribute to damping of electro-mechanical oscillations. This paper presents an on-off damping controller for a single machine system. It was used at a field test in Southern Sweden to damp oscillations of a 0.9 MW hydro power generator. The controller used estimated machine frequency as input and controlled a 20 kW resistive load via thyristor switches. The field measurements are compared to time simulations and a systematic procedure for tuning the controller is given. The results indicate that on-off control of active loads is effective in terms of added damping and that it is simple to tune and implement 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