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Power Systems, IEEE Transactions on

Issue 1 • Date Feb 2002

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Displaying Results 1 - 25 of 31
  • Including uncertainty in LOLE calculation using fuzzy set theory

    Page(s): 19 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (150 KB) |  | HTML iconHTML  

    This paper presents a conceptual possibilistic approach using fuzzy set theory to manage the uncertainties in the reliability input data of real power systems. In this paper, an algorithm is introduced to calculate the possibilistic reliability indices according to the degree of uncertainty in the given data. The probability distribution function can be transformed into an appropriate possibilistic representation using the probability-possibility consistency principle (PPCP) algorithm. In this algorithm, the transformation is performed by making a compromise between the transformation consistency and the human experience. Fuzzy classification theory is applied to reduce the number of load data points. The fuzzy classification method determines the closeness of load data points by assigning them to various clusters and then determining the distance between the clusters. The IEEE-RTS with 32-generating units is used to demonstrate the capability of the proposed algorithm View full abstract»

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  • Nash equilibrium bidding strategies in a bilateral electricity market

    Page(s): 73 - 79
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (114 KB) |  | HTML iconHTML  

    This paper examines bidding strategies in a bilateral market in which generating companies submit bids to loads. A load accepts electricity delivery from the generator with the lowest bid at its bid price as long as this price is not higher than the load's willingness to pay. Necessary and sufficient conditions of Nash equilibrium (NE) bidding strategy are derived based on a generic generating cost matrix and the loads' willingness to pay vector. The study shows that in any NE, efficient allocation is achieved. Furthermore, all Nash equilibria are revenue equivalent for the generators. Based on the necessary and sufficient conditions, this problem is formulated as an optimal assignment problem. Network optimization techniques are applied to calculate NE bid prices for the generators View full abstract»

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  • Incremental transmission loss allocation under pool dispatch

    Page(s): 26 - 33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (183 KB) |  | HTML iconHTML  

    Incremental transmission loss analysis has been used for decades, but recent interest in its application to loss allocation calls for new in-depth results. This paper demonstrates that, for incremental methods to be applied correctly in loss allocation, it is first necessary to specify the load distribution and loss supply strategies. Incremental loss allocation among bus power injections is shown to be arbitrary and, therefore, open to challenge as discriminatory. Loss allocation is possible among incremental loads and/or generators, but the proportion of the total losses assigned to either one is arbitrary. Unique, nonarbitrary incremental loss allocations are however possible among the "equivalent" incremental bilateral exchanges between generators and loads. From these basic components it is possible then to calculate the allocation among generators or loads in any specified proportion. The main results, although developed initially for small increments, are extended to large variations. Finally, a general incremental loss allocation algorithm is developed and tested View full abstract»

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  • Locational market power screening and congestion management: experience and suggestions

    Page(s): 180 - 185
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (102 KB) |  | HTML iconHTML  

    The existing New England electricity market follows a uniform pricing system: inframarginal generators are paid a uniform clearing price while constrained-on generators are paid bid prices subject to a locational market power screen. In this paper, we first report the operation experience of this approach during the market's first two years. We then briefly review the New England power system (NEPOOL) locational pricing proposal being implemented. Two new approaches for locational market power screening are presented. The first one is based on a zonal network model and the second is based on a nodal transmission model. Both approaches are being evaluated by an independent consultant and are be to recommended to NEPOOL. Test results of both approaches are included View full abstract»

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  • An integrated virtual learning system for the development of motor drive systems

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (133 KB) |  | HTML iconHTML  

    This paper describes the basic concept of an integrated virtual learning system as an instructional tool for the development of digital signal processor (DSP)-based control schemes for motor drive applications. The system is comprised of a graphical user interface (GUI) front-end and a hardware-in-the-loop custom DSP for rapid prototyping and efficient testing of digital control algorithms. The circuit design and control algorithm development of a pulse width modulation (PWM) voltage source inverter (VSI) for 3-phase brushless DC (BLDC) motor control applications is used to describe the functions of the system. It is shown that the virtual learning system provides a cost-effective learning tool for students or engineers in training and can serve as a supplement to a conventional laboratory based system View full abstract»

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  • Cooperative coevolutionary algorithm for unit commitment

    Page(s): 128 - 133
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (117 KB) |  | HTML iconHTML  

    This paper presents a new cooperative coevolutionary algorithm (CCA) for power system unit commitment. CCA is an extension of the traditional genetic algorithm (GA) which appears to have considerable potential for formulating and solving more complex problems by explicitly modeling the coevolution of cooperating species. This method combines the basic ideas of Lagrangian relaxation technique (LR) and GA to form a two-level approach. The first level uses a subgradient-based stochastic optimization method to optimize Lagrangian multipliers. The second level uses GA to solve the individual unit commitment sub-problems. CCA can manage more complicated time-dependent constraints than conventional LR. Simulation results show that CCA has a good convergent property and a significant speedup over traditional GAs and can obtain high quality solutions. The "curse of dimensionality" is surmounted, and the computational burden is almost linear with the problem scale View full abstract»

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  • Simulation and evaluation of optimization problem solutions in distributed energy management systems

    Page(s): 57 - 62
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (79 KB) |  | HTML iconHTML  

    Deregulation in electricity markets requires fast and robust optimization tools for a secure and efficient operation of the electric power system. In addition, there is the need of integrating and coordinating operational decisions taken by different utilities acting in the same market. Distributed energy management systems (DEMS) may help to fulfil these requirements. The design of a DEMS requires detailed simulation results for the evaluation of its performance. To simulate the operation of a DEMS from the optimization standpoint, a general purpose distributed optimization software tool, DistOpt, is used, and its capabilities are extended to handle power system problems. The application to the optimal power flow problem is presented View full abstract»

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  • Optimal dispatch of generating units of the Itaipu hydroelectric plant

    Page(s): 154 - 158
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (99 KB) |  | HTML iconHTML  

    This paper is concerned with the optimal dispatch of generating units of Itaipu, the world's largest hydroelectric plant in operation. Itaipu is a 12.6 GW hydro plant, located on the Parana river, in South America, composed of 18 identical 700 MW generating units. A dynamic programming model has been developed to optimize the number of generating units in operation at each hour of the day in order to attain the total generation scheduling of the plant in the most economic way. The model highlights the tradeoff between start-up/shut-down of generating units and hydro power efficiency, taking into account variations in tailrace elevation, penstock head losses and turbine-generator efficiencies. The methodology has been tested for a typical generation scheduling, and the results show that the number of the turbine-generator sets dispatched has a major influence on the overall hydroplant efficiency, and therefore it is a key aspect to be considered in the dispatch of hydro generating units. In the case of Itaipu, the economic benefits, in terms of greater power efficiency with respect to actual operation, are in the range of millions of dollars per year View full abstract»

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  • Application of a robust algorithm for dynamic state estimation of a power system

    Page(s): 141 - 147
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (203 KB) |  | HTML iconHTML  

    In this paper, a computation algorithm using the exponential function to increase the robustness of the dynamic state estimation is proposed. The merit of this approach lies in its immunity to the polluted measurements, while the implementation of the method is not complicated when compared with other methods. To validate the effectiveness of the proposed method, it was tested through several example power systems under different scenarios that include normal operation, bad measurements, sudden load change, and topology error conditions. From test results, they help support the feasibility of the method for state estimation applications View full abstract»

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  • Model predictive control and the optimization of power plant load while considering lifetime consumption

    Page(s): 186 - 191
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB) |  | HTML iconHTML  

    This paper describes a decision support system that indicates to a power plant operator the effect of daily operation on plant lifetime consumption and maintenance costs, and recommends a short-term operating strategy that optimizes plant economic performance efficiency. The recommended operating strategy is based on the optimization of an objective function that includes terms for revenues from energy sales, penalties, production costs and plant aging. Plant aging is based on models that are directly load dependent and incorporate a memory aspect, a feature that is missing from common lifetime modeling techniques. The optimization results in a tradeoff between maximization of immediate profits (i.e., earnings achieved by selling heat and power) and minimization of lifetime consumption. A model predictive control (MPC) and mixed logical dynamic (MLD) approach are used to solve the posed optimization problem and optimize this tradeoff and support the plant operator View full abstract»

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  • Coordinating fuel inventory and electric power generation under uncertainty

    Page(s): 13 - 18
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (135 KB) |  | HTML iconHTML  

    The authors discuss the problem of hedging between the natural gas and electric power markets. Based on multiple forecasts for natural gas prices, natural gas demand, and electricity prices, a stochastic optimization model advises a decision maker on when to buy or sell natural gas and when to transform gas into electricity. For relatively small models, branch-and-bound solves the problem to optimality. Larger models are solved using Benders decomposition and Lagrangian relaxation. They apply their approach to the system of an electric utility and succeed in solving problems with 50000 binary variables in less than 4 min to within 1.16% of the optimal value View full abstract»

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  • Power engineering education and the Internet: motivation and instructional tools

    Page(s): 7 - 12
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (119 KB)  

    Alternatives in the application of the Internet are applied to power engineering education. Because the student perception of power engineering is often that this is an old technology, new ways to effectively present the challenges, and the opportunities as well, are needed. The Internet and innovative graphic and textural materials are suggested to effectively present the case for power engineering as a valuable career. This is suggested to build on student interest in these computer technologies. The contents of web sites for this purpose are described, and the educational pedagogy of the method is discussed View full abstract»

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  • An improved tabu search for economic dispatch with multiple minima

    Page(s): 108 - 112
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (107 KB) |  | HTML iconHTML  

    This paper develops an improved tabu search algorithm (ITS) for economic dispatch (ED) with noncontinuous and nonsmooth cost functions. ITS employs a flexible memory system to avoid the entrapment in a local minimum and developed the ideal of "distance" to the fitness to accelerate optimization. The new approach extends simple tabu search algorithm (STS) to real valued optimization problem and applies parallelism to weaken the dependence of the convergence rate of modified tabu search algorithm (NITS) on the initial condition. Effectiveness of the method was compared with many conventional methods. Results show that the proposed algorithm can provide accurate solutions with reasonable performance and has a great potential for other applications in the power system View full abstract»

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  • Optimal selection of conductors for distribution feeders

    Page(s): 192 - 197
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (98 KB) |  | HTML iconHTML  

    Designing a distribution system requires many stages of planning and rigorous calculations. Selection of conductors for design and upgrade of distribution systems is an important part of the planning process. An ideal conductor set should have the most economic cost characteristics, sufficient thermal capacity in the largest conductor to take care of situations with very high load and it should provide proper voltage at the farthest end under peak load conditions. In this paper, a method for selection of optimal set of conductors is presented. Several financial and engineering factors are considered in the solution. The intent is to arrive at a solution, which will be the most economical when both capital and operating costs are considered. Simulations have been performed to obtain results based on different criteria and the results are compared View full abstract»

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  • Sensitivity of transfer capability margins with a fast formula

    Page(s): 34 - 40
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (101 KB) |  | HTML iconHTML  

    Bulk power transfers in electric power systems are limited by transmission network security. Transfer capability measures the maximum power transfer permissible under certain assumptions. Once a transfer capability has been computed for one set of assumptions, it is useful to quickly estimate the effect on the transfer capability of modifying those assumptions. This paper presents a computationally efficient formula for the first order sensitivity of the transfer capability with respect to the variation of any parameters. The sensitivity formula is very fast to evaluate. The approach is consistent with the current industrial practice of using DC load flow models and significantly generalizes that practice to more detailed AC power system models that include voltage and reive power limits. The computation is illustrated and tested on a 3357 bus power system View full abstract»

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  • Genetic algorithms based economic dispatch for cogeneration units considering multiplant multibuyer wheeling

    Page(s): 134 - 140
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (178 KB) |  | HTML iconHTML  

    A new method based on genetic algorithms (GA) is proposed for optimal dispatch among multiplant (cogeneration systems) with multicogenerators, which transmit MW to designated buyers (load buses) via wheeling. The operation constraints in the cogeneration systems and security constraints in the third party (transmission system owner) were considered. Varying weighting coefficients for penalty functions and determination of gene variables for GA were discussed. The IEEE 30- and 118-bus systems were used as test systems to illustrate the applicability of the proposed method View full abstract»

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  • The economics of electricity hedging and a proposed modification for the futures contract for electricity

    Page(s): 100 - 107
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (77 KB) |  | HTML iconHTML  

    First, this paper provides a simple explanation of the economics of electricity hedging and shows why the unique characteristics of electric power make risk management more complex than for other commodities. Second, a change in the futures contract for electric power is proposed that reflects these unique characteristics. These changes would create a unique resettlement mechanism which would make the futures contract more useful for hedgers on both sides of the market. Finally, a sample of data is analyzed to evaluate the effectiveness of this proposal View full abstract»

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  • Risk assessment for special protection systems

    Page(s): 63 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (214 KB) |  | HTML iconHTML  

    Special protection systems (SPS) have been widely used to increase the transfer capability of the network by assisting system operators in administering fast corrective actions. Compared with constructing new transmission facilities, SPS can be placed in service relatively quickly and inexpensively. However, increased reliance on SPS results in additional risks to system security. In this paper, based on existing reliability evaluation methods, a generic procedure for risk-based assessment of SPS is proposed. The procedure can help the system operator to identify the risk brought by SPS and to make SPS-related decisions. An illustrative example which uses a generator rejection scheme (GRS) for transient instability is provided View full abstract»

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  • Production cost minimization versus consumer payment minimization in electricity pools

    Page(s): 119 - 127
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (130 KB) |  | HTML iconHTML  

    Algorithms that involve some kind of optimization have been adopted by several electricity pools as a tool to clear the market. Traditionally, this kind of models were used on a cost minimizing basis, but recent papers have pointed out that alternative dispatches may be obtained that, even with higher production costs, result in lower electricity prices for consumers. This paper studies this new payment-minimization approach, including the long-term economic signals that it provides and their impact on future investments. The authors results show that minimizing consumer payment results in discriminatory scheduling for certain generation resources and may cause, in the long-run, higher prices for consumers View full abstract»

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  • Combined pool/bilateral dispatch. I. Performance of trading strategies

    Page(s): 92 - 99
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (223 KB) |  | HTML iconHTML  

    This three-paper series deals with the dispatch of power networks under mixed pool/bilateral trading. The major questions examined are (i) to what degree does the relative level of pool versus bilateral trading influence performance in terms of individual power levels, costs, prices, revenues and expenditures; (ii) what is the comparative performance of mixed trading with firm and nonfirm bilateral contracts under various curtailment strategies; and (iii) is the revenue derived from the pool and bilateral trading consistent with the corresponding unbundled costs? The above issues are sequentially addressed in each of the three parts. The eventual goal of these results is to help generator and load-serving entities choose appropriate relative levels of pool versus bilateral trades while considering risk, economic performance, as well as physical constraints. This paper proposes a one-step optimal power flow model that dispatches the pool in combination with the privately negotiated bilateral contracts while minimizing cost and accounting for both losses and congestion. In part I, notions of pool/bilateral demand and generation as well as a number of technical and economic performance measures for each competing entity are defined. This dissection of total and individual financial measures according to pool or bilateral trading allows the market participant to evaluate the profitability of each component of its chosen pool/bilateral mix. A number of simulation results illustrate the effect of varying the relative levels of pool/bilateral trading on the values of individual performance measures View full abstract»

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  • Marginal pricing of harmonic injections

    Page(s): 50 - 56
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (98 KB) |  | HTML iconHTML  

    Proper valuation of harmonic injections and distortion is critical if an efficient solution is to be provided for any harmonic problem, which may exist. Indeed without proper tools to value harmonic distortion, it is not possible to quantify the extent of any problem. This paper demonstrates that it is possible to develop marginal prices for harmonic injections, which will accurately reflect the value of the injections to the rest of the network. Given an allocation of harmonic pollution rights these prices act to coordinate each member of the network to act in a globally optimal manner View full abstract»

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  • One-hour-ahead load forecasting using neural network

    Page(s): 113 - 118
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (113 KB) |  | HTML iconHTML  

    Load forecasting has always been the essential part of an efficient power system planning and operation. Several electric power companies are now forecasting load power based on conventional methods. However, since the relationship between load power and factors influencing load power is nonlinear, it is difficult to identify its nonlinearity by using conventional methods. Most of papers deal with 24-hour-ahead load forecasting or next day peak load forecasting. These methods forecast the demand power by using forecasted temperature as forecast information. But, when the temperature curves changes rapidly on the forecast day, load power changes greatly and forecast error would going to increase. In conventional methods neural networks uses all similar day's data to learn the trend of similarity. However, learning of all similar day's data is very complex, and it does not suit learning of neural network. Therefore, it is necessary to reduce the neural network structure and learning time. To overcome these problems, we propose a one-hour-ahead load forecasting method using the correction of similar day data. In the proposed prediction method, the forecasted load power is obtained by adding a correction to the selected similar day data View full abstract»

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  • Energetic operation planning using genetic algorithms

    Page(s): 173 - 179
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (147 KB)  

    This paper investigates the application of genetic algorithms to optimize large, nonlinear complex systems, particularly the optimization of the operation planning of hydrothermal power systems. Several of the current studies to solve this kind of problem are based on nonlinear programming. This approach presents some deficiencies, such as difficult convergence, oversimplification of the original problem or difficulties related to the objective function approximation. Aiming to find more efficient solutions for this class of problems, this paper proposes and investigates the use of a genetic approach. The characteristics of the GAs such as simplicity, parallelism, and generality, can provide an effective solution to these problems. The paper presents an adaptation of the technique and an actual application on the optimization of the operation planning for a cascade system composed of interconnected hydroelectric plants View full abstract»

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  • Unit commitment solution methodology using genetic algorithm

    Page(s): 87 - 91
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB) |  | HTML iconHTML  

    Solution methodology of unit commitment (UC) using genetic algorithms (GA) is presented. Problem formulation of the unit commitment takes into consideration the minimum up and down time constraints, start up cost and spinning reserve, which is defined as minimization of the total objective function while satisfying the associated constraints. Problem specific operators are proposed for the satisfaction of time dependent constraints. Problem formulation, representation and the simulation results for a 10 generator-scheduling problem are presented View full abstract»

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  • Distribution pricing based on yardstick regulation

    Page(s): 198 - 204
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (67 KB)  

    Transmission and distribution (T&D) pricing has been one of the keystones of the ongoing deregulation and privatization process in the power industry. The electricity market has been established based on the assumption of open access and nondiscriminatory use of the T&D assets. As T&D business remains as a monopoly, it is necessary to provide economic regulation. Many papers have dealt with transmission pricing and certain maturity has been reached in this area, but this is not true in the case of distribution services. This paper focuses on the distribution pricing methods and suggests one that is currently under development in Brazil. This method is based on incremental costs derived from the aggregated expansion plan of a particular utility, named model utility. This utility was obtained by comparisons among the real distribution companies. The method follows the fundamentals of the yardstick regulation 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