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Power Systems, IEEE Transactions on

Issue 2 • Date May 1989

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Displaying Results 1 - 25 of 52
  • Suppression of numerical oscillations in the EMTP power systems

    Page(s): 739 - 747
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    The integration scheme in the electromagnetic transients program EMTP has been modified to solve the problem of sustained numerical oscillations that occur when the trapezoidal rule has to act as a differentiator. These oscillations appear, for instance, on the voltage across an inductance after current interruption. The technique presented prevents these oscillations by providing critical damping of the discontinuity within one Δt of the simulation. The critical damping adjustment (CDA) is achieved by means of two Δt/2 integration steps using the backward Euler rule. With the CDA scheme the trapezoidal rule can still be used throughout the entire simulation without the problem at discontinuities. The effectiveness of the scheme is illustrated with simulation results View full abstract»

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  • Algorithms for a spot price responding residential load controller

    Page(s): 507 - 516
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    A description is given of the algorithms designed for use in residential load control systems. The authors present the functions to be fulfilled by such a price-responsive device and describe the end-user devices available in residences and the control logics applicable to each. It is concluded that there is a need to understand customer attitudes and acceptance in the design of the response strategies and in the design of the man-machine interface View full abstract»

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  • Joint development and consistent bulk transmission outage reporting and analysis procedures by two NERC regions

    Page(s): 517 - 523
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    Two North American Electric Reliability Council (NERC) regions, the Mid-Continent Area Power Pool and the Mid-America Interconnected Network, have individually collected bulk transmission outage data for a number of years. Based on recent research work, the members of the two regions realized that related multiple outages significantly affect bulk transmission system reliability. However, no existing data collection methods provided sufficient data to report and analyze adequately relationships between multiple outages. The experiences of these NERC regions working together to derive a consistent bulk transmission performance analysis package are discussed. The resultant data collection philosophy and format and the expected analysis capability are reviewed. Potential benefits of standardizing data formats and definitions are presented View full abstract»

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  • WRATES: a tool for evaluating the marginal cost of wheeling

    Page(s): 594 - 605
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    A description is presented of a computer program, WRATES (wheeling rate evaluation simulator), which can be used to evaluate the marginal cost of wheeling between utilities, private users, and private generators, taking into consideration the effects of Kirchoff's laws on transmission line flows, losses, and overloads. WRATES can evaluate the resulting marginal cost-based wheeling rates using options for incorporating the effect of capital recovery: that includes network only or network and generators with various levels of disaggregation. The theory underlying WRATES is general and suitable for online implementation. However, WRATES itself is a PC-based, user-friendly program designed for policy-type studies (the present version is for a 25 bus, 200 line, five utility system solved using a DC load flow) View full abstract»

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  • Implications of frequency control bias settings on interconnected system operation and inadvertent energy accounting

    Page(s): 712 - 723
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    Practices for inadvertant energy and time error correction have been discussed in the literature. A description of these practices is presented from the interconnection point of view by considering the resulting constrained coupling effects between control areas. Partial implementations of decomposition theory are suggested as practical solutions to the iniquities and deficiencies of scheme presented here. An implementation scheme for phasing-in decomposition accounting, which can be voluntary, by area, is suggested and explained. An argument is made for an official and essentially constant annual value of frequency bias to be used for decomposition. The frequency bias used in area control error need not be constant or necessarily equal to the decomposition parameter View full abstract»

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  • The inclusion of dynamic factors in statistical power system cost models. II. Part loading and reserve costs

    Page(s): 524 - 529
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    For pt.I see ibid., vol.4, no.2, p.419-25 (1989). Techniques are developed for analyzing the costs of maintaining adequate operating reserver on power systems, within probabilistic production costing models and other based on load distribution functions. The aim is to show that such models can be developed to approximate the full range of dynamic penalties associated with practical power system operation. Algorithms for costing predetermined part loading are presented, taking into account the need for bringing plant online out of strict merit order. The author describes how a prediction error function can be used to estimate the probability that the specified spinning reserve is insufficient and hence approximate for the cost of gas turbine or storage utilization for dynamic control. This allows estimation of optimal reserve levels. The author discusses the analysis of longer term reserve from banked thermal units. Some results of the model are compared to those reported from hourly simulation studies View full abstract»

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  • A theory of electricity tariff design for optimal operation and investment

    Page(s): 606 - 613
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    This study addresses the problem of balancing supply- and demand-side operation and investment activities. Existing theory is extended to cover electricity industry models with uncertainty in future conditions and intertemporal linking such as storage and investment. An optimal pricing structure which takes these into account is presented. It would induce participants (suppliers and consumers) to make profit-maximizing investment and operation decisions which are socially optimal. The structure contains two terms: a short-run marginal cost pricing as well as a new incentive term to account for the interaction of participants at different time points. A probabilistic forecast of pricing structures at future time is required. A justification of the result and three simple illustrative examples are given View full abstract»

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  • Effect of load models on AC/DC system stability and modulation control design

    Page(s): 411 - 418
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    An investigation is conducted of the effect of load models on the modulated AC/DC system. Static load is modeled as a nonlinear function of load bus voltage, and dynamic load is modeled by an equivalent induction motor. DC power and relative power modulations are considered for the modulation controllers. A method for eigenvalue sensitivity calculation is developed to predict the effect of load characteristics on the system stability. Eigenvalue sensitivity and simulation results show that static and dynamic load characteristics can have a considerable effect on the system stability. The impact of static and dynamic load modules on the modulation controller gains obtained via optimal control theory is examined and it is shown that load models can have a marked influence on the controller gains. It is also shown that there are specific situations where the choice of load model can make a difference in system stability prediction View full abstract»

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  • Apparent impedance measuring systems (AIMS)

    Page(s): 575 - 585
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    For the analysis of subsynchronous resonance, computer models of an electric system have generally been based on a modified 60 Hz model with short-circuit equivalents for power sources and with loads neglected. Due to the importance of validating the electric systems model, AIMS has been developed to measure the apparent impedance as a function of frequency seen at the terminals of the study generator. AIMS has been successfully applied to an extensive power system. A description is given of AIMS and the significant modeling improvement realized by it application View full abstract»

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  • Hydrothermal optimal power flow based on a combined linear and nonlinear programming methodology

    Page(s): 530 - 537
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    The author's consider a new formulation of optimal power flow (OPF) that makes it eminently suitable for accurate incremental modeling. G. Zoutendijk's method of feasible directions (1960) for solving the nonlinear programming problems is adapted for the solution of the OPF. Hydraulic modeling of systems with a considerable share of hydraulic generation is considered. The method is very efficient as it is designed to exploit the special structure of the problem View full abstract»

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  • Closing the generation gap [4GLs in the power education curriculum]

    Page(s): 808 - 811
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    The deep inroads made by computers into all aspects of electrical power systems are making greater demands on the power education curriculum. It is suggested that exposure to fourth-generation languages would enhance a student's programming capabilities. Features of fourth-generation languages in the context of power system software development are described. Ways of introducing the fourth-generation languages in power engineering education are outlined. A specific example of distribution system analysis software is presented View full abstract»

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  • Evaluation of unit connected, variable speed, hydropower station for HVDC power transmission

    Page(s): 668 - 676
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    An economic alternative to the conventional design of a hydropower station which feeds power into a HVDC transmission line is described. A method is developed to operate hydraulic turbines under variable speed to maximize the turbine efficiency, taking the loading and water head connections into account. A 10×100 MW unit-connected hydroelectric power station is analyzed. A 500 MW unit-connection scheme which represents one pole of the above station is simulated in the time domain using the electromagnetic transient program. The harmonic currents flowing in the stator and rotor circuits of the generator are computed, and derating factors at 60 Hz and 70 Hz operation are evaluated. Economic evaluation has been performed for a 10×100 MW hydrostation for both conventional and unit-connection configurations. Savings achieved by adopting the unit-connection scheme are presented View full abstract»

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  • Variance of power generating system production costs

    Page(s): 662 - 667
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    Using the framework for production costs of H. Baleriaux (1967), this study provides formulae for computing the variance of the unit energy produced and the variance of the system production costs. Numerical results show that the coefficient of variation of these quantities can be quite large, highlighting the need for considering variances in addition to the expected values in production-costing models. Numerical examples show that the ratio of the standard deviation of unit energy produced to its mean value can be quite high. A similar observation applies for the system production costs. This suggests that basing utility decisions on the mean values only could be misleading and that the currently used production-costing models should be enlarged to include information on variance as well View full abstract»

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  • The inclusion of dynamic factors in statistical power system cost models. I. Assessment of startup and banking costs

    Page(s): 419 - 425
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    Methods are developed for approximating dynamic aspects of power system costs within the load duration and probabilistic framework. The approach uses a transition-frequency function, as applied in frequency and duration methods of system reliability assessment, together with a function expressing the RMS prediction error in load forecasting. The author shows how the transition-frequency function can be used to estimate plant startup and banking costs under various conditions. He demonstrates how the calculations can be performed in terms of cumulants of the functions involved, making possible a very efficient formulation View full abstract»

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  • An enhanced LQ adaptive VAr unit controller for power system damping

    Page(s): 443 - 451
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    An adaptive linear quadratic Gaussian control strategy is presented for static VAr compensators to enhance power system damping and stability. The control strategy utilizes only local information to dampen oscillatory modes present in the network. The controller calculates an appropriate value of static VAr compensator susceptance to present to the network at each sampling interval based on a reduced-order model of the power system. The reduced-order model is obtained online by a least-squares identifier. Simulation results for a nine-bus network are presented View full abstract»

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  • Coal to natural gas seasonal fuel switching: an option for acid rain control

    Page(s): 457 - 462
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    An investigation is conducted of seasonal fuel-switching as a means to control SO2 emissions. There is evidence that strategic control of emissions results in environmental improvements at a lower overall cost. The Electric Generation Expansion Analysis System (EGEAS) was used as the primary analytical tool for the study. The economics of gas substitution versus flue gas desulfurization technology was studied under a variety of economic conditions, taking into account initial capital investment, variable operating and maintenance costs, retrofit costs, pipelining costs, and a number of other factors. Natural gas substitution was found to be an economical means of efficient energy production combining low cost and significant emission reduction under a variety of conditions View full abstract»

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  • Software design and evaluation of a microcomputer-based automated load forecasting system

    Page(s): 782 - 788
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    A discussion is presented of the software design and evaluation of a microcomputer-based automated load forecasting system. This system is based on an IBM RT/PC microcomputer, and Extended Fortran, Ratfor, and C languages. The online load and weather data collection, filtering, archiving, and load forecasting are totally automated. The forecast is based on the relationship between weather and electric utility load (MW) as extracted from historical data. `If. . .then' types of rules and other statistical relationships form the rule-base of the algorithm. This rule-base has been applied to generate the hourly system load forecasts for 1983 and 1986 in the Virginia Power service area. A 24 hour load forecast takes 20 seconds on the IBM-RT/PC. The absolute annual averages of the hourly load forecasts errors are found to be 1.437% and 1.298% for 1983 and 1986, respectively. Out of these two years, there were only nine occasions when the software failed to predict the hour of the daily peak. Moreover, these peaks were missed by only one hour View full abstract»

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  • Structural analysis of the electrical system: application to secondary voltage control in France

    Page(s): 479 - 486
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    The voltage control of the French EHV power system is organized in three levels (primary, secondary, and tertiary) which concern distinct geographical areas and time constants. The authors present studies conducted to reach an automatic determination of zones and pilot nodes based on the examination of the structure of the network. The concept of electrical distance has been developed, and its close relationship with the theory of information is underlined. This concept allows the concept of structural controllability and observability of proximity to be extended to the power system. The combined use of this electrical distance and typological analysis algorithms has proven an effective method for the identification of the secondary voltage control zones of the French grid View full abstract»

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  • Transient stability prediction and control in real-time by QUEP

    Page(s): 627 - 642
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    A method for the real-time analysis and control of power system transient stability has been developed incorporating detailed machine models. The method uses a quasi-unstable equilibrium point (QUEP) energy function approach to evaluate the stability margin of a power system. The mode of disturbance that best predicts stability is determined very rapidly by a novel generating-unit-clustering procedure. Transient stability sensitivity coefficients are calculated for use in a constrained economic dispatch algorithm. Corrective action constraints are developed as simple limits on the sums of generator outputs. A theorem stating the necessary and sufficient conditions for the existence of a power-system energy function is presented View full abstract»

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  • An adaptive stabilizer for thyristor controlled static VAR compensators for power systems

    Page(s): 403 - 410
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    The authors present the analytical development of a controller scheme for a static VAr system and present detailed simulation results to highlight its effectiveness in comparison with a discrete PI (proportional-integral) stabilizer under a variety of operating conditions for power transmission systems. The adaptive stabilizer is suitable for microprocessor digital implementation as the numerical steps involved are minimal. The adaptive stabilizer uses a stochastic variant simplified parameter estimator routine, thus providing a faster sampling rate and identification of a larger number of parameters in real time. The implementation of this stabilizer is simple as it involves additions, multiplications without matrix inversion, etc View full abstract»

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  • Reduced order models for an induction motor group during bus transfer

    Page(s): 494 - 498
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    A method of modifying the standard reduced-order model of the induction machine to provide improved accuracy during bus transfer of a group of machines with a static load is presented. Two separate modifications are added, one to correct voltage response during the disconnect period and one to improve the mechanical response after reconnect. Accuracy is investigated by a comparison of motor group response during bus transfer using the corrected reduced model, the standard reduced model, and the full-order machine model. It is shown that the corrected model provides improved replication of the full-model voltage during disconnect and current and speed after reconnect. Improved accuracy is obtained through the use of two algebraic correction terms and a state variable change View full abstract»

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  • Unit connected operator with diode valve rectifier scheme

    Page(s): 538 - 543
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    The application of a diode bridge rectifier unit connected to a generator feeding a sending-end HVDC station shows a substantial reduction in the station cost. One of the major problems of this configuration is its slow recovery from a DC line fault. The authors propose and analyze a few types of control and protection schemes for the generator. The minimum time required to restore full power subsequent to a DC line fault is studied for each scheme. The results of a digital computer study are presented, as are some results obtained from a real-time physical component HVDC simulator View full abstract»

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  • A general-purpose version of the fast decoupled load flow

    Page(s): 760 - 770
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    A new version of the fast decoupled load flow, in which a more broad range of power systems can be solved, is presented. The key lies in the different way in which the resistances are ignored and in a different iteration scheme. In the standard algorithm the resistances are ignored while building the B' load flow matrix: it is shown that it is preferable that the resistances are ignored in the B" matrix instead of the B' matrix. For normal test systems there is hardly any difference in the number of iterations. However, the new algorithm iterates faster if one or more problematic R/X ratios are present. An iteration scheme with strict successive P and Q iterations prevents cycling convergence behavior which can be found in some low voltage systems. The advantages of the new version are demonstrated with runs on IEEE test systems, with both uniformly and nonuniformly scaled reactances. R -scaling up to 3 is always possible, and sometimes values up to 5 can be used. X-scaling of at least 0.1 is possible without losing convergence and with iteration counts which are significantly lower than with the standard scheme View full abstract»

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  • The Kansas Electric Utilities Research Program: a model of utility/university cooperation

    Page(s): 812 - 816
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    The Kansas Electric Utilities Research Program (KEURP) is a joint venture by six electric utilities in the state of Kansas to undertake and encourage applied research and development projects which may enhance reliability and minimize the cost of electric service in Kansas. The authors give a brief history of KEURP and describe its structure and operation. Several of the research projects sponsored by KEURP are described. A discussion is presented of the perceived benefits and difficulties with KEURP from a number of viewpoints View full abstract»

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  • VAr planning for power system security

    Page(s): 677 - 686
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    A method is presented for identifying a dispersed reactive power (VAr) supply that can enhance power systems' pre- and post-contingency voltage security, subject to technical and economic constraints. The problem is formulated in two stages. The first stage involves a nonlinear optimization problem which minimizes the amount of reactive supply. The second stage uses a mixed-integer linear program which optimizes the number of candidates buses for VAr support. Results of application of the method to an example system are presented 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.

Full Aims & Scope

Meet Our Editors

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