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Power Systems, IEEE Transactions on

Issue 2 • Date May 1999

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Displaying Results 1 - 25 of 57
  • 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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  • Sequential synthesis of structured singular value based decentralized controllers in power systems

    Page(s): 635 - 641
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    This paper presents a systematic procedure for the design of decentralized controllers for multimachine power systems. The robust performance in terms of the structured singular value (SSV or μ) is used as the measure of control performance. A wide range of operating conditions were used for testing. Simulation results have shown that the resulting μ- controllers would effectively enhance the damping torques, providing better robust stability and/or performance characteristics both in the frequency and time-domain compared to conventionally designed power system stabilizers (PSSs) View full abstract»

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  • Teaching distribution system reliability evaluation using Monte Carlo simulation

    Page(s): 397 - 403
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    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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  • Transient stability-constrained maximum allowable transfer

    Page(s): 654 - 659
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    A method is proposed for allocating generation so as to maximize power transfer between areas of interconnected power systems under transient stability constraints. This “transient stability-constrained maximum allowable transfer” (MAT) method consists of screening a large number of contingencies, scrutinizing the dangerous ones and suggesting generation rescheduling patterns to stabilize them. The MAT method is based on SIME, a hybrid transient stability method. Like SIME, MAT is accurate and free from simplifying assumptions about modelling, stability scenarios and instability modes. In addition, by controlling all dangerous contingencies simultaneously, the method succeeds in being fully compatible with requirements for real-time preventive monitoring and control. The method is illustrated on the South-Southeast Brazilian power system, operating under highly stressed conditions imposed by large power transfer between areas 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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  • Unit commitment with transmission security and voltage constraints

    Page(s): 757 - 764
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    In this paper, optimal power flow (with transmission security and voltage constraints) is incorporated in the unit commitment formulation. Using Benders decomposition, the formulation is decomposed into a master problem and a subproblem. The master problem solves unit commitment with prevailing constraints, except transmission security and voltage constraints, by augmented Lagrangian relaxation. The subproblem minimizes violations of transmission security and voltage constraints for a commitment schedule given in the master problem. Since transmission constraints are decoupled from voltage constraints in the subproblem, the subproblem could further be decomposed into two smaller subproblems. The resulting transmission subproblem minimizes transmission flow violations for the worst contingency case by adjusting unit generation and phase shifter controls. The corresponding reactive subproblem minimizes voltage constraints by reactive power generation and tap changing controls. In the case of transmission flow or voltage infeasibility, Benders cuts are produced for unit commitment rescheduling. The iterative process between the master problem and the subproblems provides a minimum production cost solution for generation scheduling while satisfying the constraints. A comprehensive unit commitment software package is developed using Visual C++. A 36-unit system in the IEEE-118 bus network is used to demonstrate the efficiency of the method View full abstract»

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  • 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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  • A data envelopment analysis approach to evaluation of operational inefficiencies in power generating units: a case study of Indian power plants

    Page(s): 419 - 425
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    A nonparametric approach to frontier analysis, data envelopment analysis (DEA), is applied in this work to evaluate the operational inefficiencies of generating units. Three parameters viz. generation per unit of coal consumed, generation per unit of oil consumed and generation per unit of auxiliary power consumption have been considered as indicators of performance. The DEA approach provides with a best practice frontier for each of these parameters, which can then serve as a benchmark for efficiency. Also, the slack analysis indicates the causes of inefficiency. A time series study of units' performance, identifies those units that need renovation and repowering and those units where the performance could be improved by extensive training of operating personnel. The analysis in this paper considers operational performance statistics of all coal based generating units belonging to National Thermal Power Corporation of India over the period 1991 to 1995 View full abstract»

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  • Composite system reliability evaluation based on Monte-Carlo simulation combined with outages screening

    Page(s): 785 - 790
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    A new algorithm for composite system reliability evaluation is proposed. The new algorithm is based on the Monte-Carlo simulation method. Before simulation, an acceleration table is formed according to the screening of all the single and double outages, during simulation, all the multiple outages are considered and evaluated by using the acceleration table. In order to reduce the computational quantity, a heuristics algorithm is adopted. The concepts of relevant regions and regulative regions are proposed based on the concept of central relaxation and are used to judge the relations between the faulted components, which make it efficient to screen possible contingencies. The IEEE RTS (24-bus, 38-line, 32-generator) and the Northeast China Power System (NECPS, 331-bus, 467-line, 179-generator) were evaluated by using the developed algorithm. Results show that the new algorithm is credible and efficient. When the scale of the system is enlarged the computational quantity is increased linearly. So the new algorithm can be used for large scale power system reliability evaluation 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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  • 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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  • Experience with FNN models for medium term power demand predictions

    Page(s): 538 - 546
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    The authors relate experience of predicting medium-term load demand for the Israeli power grid using neural network models. A variety of different regularization procedures are used for training and the results are compared. Furthermore, they make suggestions on combining models and selecting input variables 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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  • Development of BCU classifiers for on-line dynamic contingency screening of electric power systems

    Page(s): 660 - 666
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    A sequence of BCU classifiers for online dynamic contingency screening is developed and their theoretical basis is provided. The design objective of the BCU classifiers is to ensure that unstable (single-swing or multiswing) contingencies be completely captured and that the number of contingencies needed for further analysis be significantly reduced. An architecture for online dynamic security assessments consisting of the BCU classifiers and an online transient stability (time-domain) simulation program is presented. The effectiveness of the developed BCU classifiers and proposed architecture is evaluated with very promising results using 7120 contingencies on a 50-generator, 145-bus power system and a 202-generator, 1293-bus real power system data View full abstract»

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  • Application of a novel fuzzy neural network to real-time transient stability swings prediction based on synchronized phasor measurements

    Page(s): 685 - 692
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    The ability to rapidly acquire synchronized phasor measurements from around a power system opens up new possibilities for power system protection and control. In this paper, the authors develop a novel class of fuzzy hyperrectangular composite neural networks which utilize synchronized phasor measurements to provide fast transient stability swings prediction for use with high-speed control. Primary features of the method include constructing a fuzzy neural network for all fault locations, using a short window of realistic-precision post-fault phasor measurements for the prediction, and testing robustness to variations in the operating point. From simulation tests on a sample power system, it reveals that the proposed tool can yield a highly successful prediction rate in real-time View full abstract»

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  • Improving an interior-point-based OPF by dynamic adjustments of step sizes and tolerances

    Page(s): 709 - 717
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    This paper presents an efficient interior point algorithm for optimal power flow (OPF) problems, in particular, the real power dispatch and the reactive power dispatch problems. The nonlinear OPF problem is solved by a predictor-corrector primal-dual log-barrier (PCPDLB) method as a sequence of linearized sub-problems. Besides discussing the problem formulation, the paper offers a detailed description of the PCPDLB algorithm; it also addresses several implementation issues such as the determination of barrier parameter and the customization of initial points for OPF problems. In addition, practical issues on how to choose linear step sizes and convergence criteria are investigated to evaluate their impact on the performance of the algorithm. Some heuristics of dynamically adjusting step sizes and tolerance are proposed which significantly improve OPF solution speed. Computational results on power systems of 118 and 1062 buses are presented and discussed. Comparisons with other variants of primal-dual log-barrier methods are also provided to demonstrate the superiority of the proposed predictor-corrector interior point algorithm View full abstract»

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  • A framework of voltage stability assessment in power system reliability analysis

    Page(s): 484 - 491
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    This paper provides a novel framework for extending conventional probabilistic reliability analysis to account for system stability limits. The scheme integrates a voltage stability index with existing reliability tools for offline assessment. The index relates the probability of instability to the proximity of voltage collapse. The scheme is successfully tested using the IEEE Reliability test system View full abstract»

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  • Hybridizing rule-based power system stabilizers with genetic algorithms

    Page(s): 600 - 607
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    A hybrid genetic rule-based power system stabilizer (GRBPSS) is presented in this paper. The proposed approach uses genetic algorithms (GA) to search for optimal settings of rule-based power system stabilizer (RBPSS) parameters. Incorporation of GA in RBPSSs design will add an intelligent dimension to these stabilizers and significantly reduce the time consumed in the design process. It is shown in this paper that the performance of RBPSS can be improved significantly by incorporating a genetic-based learning mechanism. The performance of the proposed GRBPSS under different disturbances and loading conditions is investigated for a single machine infinite bus system and two multimachine power systems. The results show the superiority of the proposed GRBPSS as compared to both conventional lead-lag PSS (CPSS) and classical RBPSS. The capability of the proposed GRBPSS to damp out the local as well as the interarea modes of oscillations is also demonstrated 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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  • 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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  • Real-time preventive actions for the enhancement of voltage-degraded trajectories

    Page(s): 561 - 568
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    This paper deals with the development of a nonlinear programming methodology for evaluating preventive actions to improve the dynamic security of power systems when poor voltage transients are detected. For the proposed power system modeling, voltage-degraded trajectories arise from both angle and voltage instability on the transient time scale. The rescheduling of the generation improves power system security by ensuring an acceptable voltage transient behavior and constraining the system to be stable. The algorithm is implemented and tested on an actual power system 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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  • Application of design patterns for object-oriented modeling of power systems

    Page(s): 532 - 537
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    This paper introduces the concepts of design patterns and demonstrates the potential of applying this technique for power system modeling. Captured by experienced object-oriented designers, design patterns solve specific design problems and make object-oriented designs more flexible, extensible and elegant. This technique has been successfully applied in the design of a generic distribution circuit object model. Some of the more powerful design patterns, such as object composition, delegation, recursive composition and proxy etc., have been effectively used to help determine modeling granularity, find appropriate objects and achieve modeling flexibility. When properly applied, the design patterns can help solve many of the design problems in the object-oriented modeling of power systems View full abstract»

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  • Dynamic modeling of high power static switching circuits in the dq-frame

    Page(s): 678 - 684
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    With the proliferation of static switching circuits in power systems, there is a need to understand not only their steady-state behaviour but their dynamic interaction with the network as well. Analysis is difficult due to the nonlinear nature of switching processes associated with such devices. Linear, time-invariant (LTI) dynamic models are needed for standard analytical tools such as eigenanalysis for the study of inter-area as well as higher frequency modes of the system. To this end, LTI small-signal dynamic models are developed for high power static switching circuits in a synchronous rotating dq-reference frame. Two conventional devices are chosen for study: a thyristor controlled series capacitor (TCSC) and a HVDC power converter. The proposed models are shown to represent the dynamic response of the static switching circuits to nominal changes in operating point. In particular, the damping characterizing the dynamic behaviour of the TCSC is shown to vary significantly with operating point. This accounts for the observed responses arising from field tests and simulations but not accounted for by the quasi-static model. On the other hand, the damping characterizing the dynamic behaviour of the HVDC converter is shown to vary little with operating point. The linearized models are validated by digital time-domain simulation of the nonlinear static switching circuits 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