Showing papers in "IEEE Transactions on Power Systems in 1987"
TL;DR: In this paper, a mathematical framework for the solution of the economic dispatch problem with security constraints is presented, which can take into account the system corrective capabilities after the outage has occurred, and the solution algorithm is based on mathematical programming decomposition techniques that allow the iterative solution of a "base-case" economic dispatch and separate contingency analysis with generation rescheduling to eliminate constraint violations.
Abstract: This paper describes a mathematical framework for the solution of the economic dispatch problem with security constraints, which can take into account the system corrective capabilities after the outage has occurred. The solution algorithm is based on mathematical programming decomposition techniques that allow the iterative solution of a "base-case" economic dispatch and separate contingency analysis with generation rescheduling to eliminate constraint violations. The resulting dispatch has the same security level as the usual security-constrained dispatch, but with lower operating costs. Case studies with the IEEE 118-bus are presented. The extension of the methodology to the probabilistic case will be discussed in a forthcoming paper.
621 citations
TL;DR: In this paper, a dynamic programming formulation of the unit commitment problem is presented, which features the classification of generating units into related groups so as to minimize the number of unit combinations which must be tested without precluding the optimal path.
Abstract: A field-proven dynamic programming formulation of the unit commitment problem is presented. This approach features the classification of generating units into related groups so as to minimize the number of unit combinations which must be tested without precluding the optimal path. Programming techniques are described which maximize efficiency. Considerations are discussed which determine when generating units must be evaluated and when they may be ignored. The heuristic procedures described in this paper are concerned with supplying all apriori information to the program thereby minimizing its execution time. Results are presented from field testing on a medium size utility. Composite generating unit formulation is described for the economic allocation of constrained fuel to a group of units.
507 citations
TL;DR: It is shown than Box and Jenkins time series models, in particular, are well suited to this application and one of the drawbacks of these models is the inability to accurately represent the nonlinear relationship between load and temperature.
Abstract: The application of time series analysis methods to load forecasting is reviewed. It is shown than Box and Jenkins time series models, in particular, are well suited to this application. The logical and organized procedures for model development using the autocorrelation function and the partial autocorrelation function make these models particularly attractive. One of the drawbacks of these models is the inability to accurately represent the nonlinear relationship between load and temperature. A simple procedure for overcoming this difficulty is introduced, and several Box and Jenkins models are compared with a forecasting procedure currently used by a utility company.
491 citations
TL;DR: In this article, the authors present a review of the present regional secondary voltage control, and the prospects for the evolution towards a co-ordinated system, based on a sensitivity matrix model, closed-loop pole assignment and adaptive techniques.
Abstract: The voltage control of the french power system is organized in three hierarchical levels, which concern distinct geographical areas and time constants. The rapid and random variations are compensated by local primary and automatic actions on the generators A.V.Rs, then the slow variations are regulated by the secondary (at regional level) and tertiary (at national level) actions. The paper gives a review of the present regional secondary voltage control, and the prospects for the evolution towards a co-ordinated system, based on a sensitivity matrix model, closed-loop pole assignment and adaptive techniques. Analog and digital simulations are presented.
285 citations
TL;DR: The IEEE PES System Operation Subcommittee has established the Power System Restoration Task Force to: review operating practices, conduct a literature search, prepare relevant glossaries and bibliographies, and promote information exchange through technical papers.
Abstract: The IEEE PES System Operation Subcommittee has established the Power System Restoration Task Force to: review operating practices, conduct a literature search, prepare relevant glossaries and bibliographies, and promote information exchange through technical papers. This is the first report of the Task Force. The problem of bulk power system restoration following a complete or partial collapse is practically as old as the electric utility industry itself. Many electric utilities have developed over the years system restoration schemes that meet the needs of their particular systems. These plans provide a great deal of insight into how the restorative process is viewed by operating and planning personnel and what concerns and constraints any plan must operate under. The body of the report consists of notes prepared by members of the Task Force. It should not be inferred that a complete reporting on Power System Restoration is undertaken here. The intent is to report upon work of the Task Force to date. The report also reviews several different restoration plans and shows their common concerns and constraints.
222 citations
TL;DR: In this paper, a method for modeling series capacitors protected by metal oxide varistors has been developed for calculations requiring linear impedances, which can now be adapted to perform the previously infeasible calculations on circuits containing these nonlinear protection devices.
Abstract: A method for modeling series capacitors protected by metal oxide varistors has been developed for calculations requiring linear impedances. Fault and stability programs can now be adapted to perform the previously infeasible calculations on circuits containing these non-linear protection devices. The model which is simple yet applicable to virtually any series capacitor installation has been incorporated into BPA's fault and stability programs. This paper describes the development and use of this unique method.
132 citations
TL;DR: In this paper, the status of adaptive control theory in electrical power systems control is reviewed and current mechanisms and methods of electrical power system control are examined, including adaptive generator exciter control and adaptive load-frequency control.
Abstract: Potential applications of adaptive control theory to electrical power systems control are explored. In the first part of the paper, the status of adaptive control theory is reviewed. Current mechanisms and methods of electrical power systems control are then examined. The two areas in adaptive power system control that have received the most attention are adaptive generator exciter control and adaptive load-frequency control. Nine recent papers on adaptive exciter control are described, as also are three papers on adaptive load-frequency control. Potential applications of adaptive control to other power system control problems are noted.
130 citations
TL;DR: In this paper, the power system restoration task force (PSR-TF) reviewed the 1979-83 North American Electric Reliability Council (NERC) Reports on Major Bulk Power System Disturbances (2), identifying restoration problems which have been encountered during that 5-year period.
Abstract: In its second report, the Power System Restoration Task Force (PSR-TF) (1) reviews the 1979-83 North American Electric Reliability Council (NERC) Reports on Major Bulk Power System Disturbances (2), identifying restoration problems which have been encountered during that 5-year period. Generally, these problems fall into three phases of restoration activities: planning for restart, reintegration and restoration of the bulk power supply; control actions during system degradation for saving and retaining critical sources of power; and restoration after a major disturbance when the power system has stabilized. The report also briefly discusses the applicability of several existing programs to the system restoration process. The opinions and conclusions expressed in this paper are those of the authors; they are based on the referenced reports and have not been reviewed with NERC or the reporting utilities.
120 citations
TL;DR: In this paper, a linear programming based methodology for corrective control computations is presented, which computes adjustments of unit real power output, VAR source output, transformer tap settings, capacitor/reactor switching, branch switching or line sectionalization, and if necessary, load shedding.
Abstract: This paper presents a linear programming based methodology for corrective controls computations. The methodology computes adjustments of unit real power output, VAR source output, transformer tap settings, capacitor/reactor switching, branch switching or line sectionalization, and if necessary, load shedding. A previous publication presented the basic algorithm for computing adjustments of continuous controls such as generator real power, transformer tap setting, etc. This paper addresses the problem of incorporating discrete controls such as capacitor/reactor switching and line switching/sectionalization into the overall procedure. Efficient algorithms are presented for the computation of discrete controls such as capacitor bank and transmission line switching. The methodology is illustrated with typical results obtained with the Georgia Power Company's 500 kV/230 kV/115 kV system. The network representation of this system comprises 981 buses and 1175 circuits.
115 citations
TL;DR: In this article, the authors used two different approaches and a customer damage function to evaluate a factor designated as the Interrupted Energy Assessment Rate (IEAR) which can be used in conjunction with the calculated expected energy not supplied in the assessment of reliability worth.
Abstract: Quantitative reliability evaluation is an important aspect of power system planning and operation. The indices produced in these applications are utilized in a wide range of management decisions throughout a utility. One issue which is often debated is the cost associated with a particular level of reliability. In order to make this argument complete, it is necessary to also thoroughly examine the worth or benefit associated with a particular level of reliability. Estimates of the impact of interruptions in service can be obtained by assessing the losses incurred by different customer types and classes. These data can then be used to generate a composite customer damage function for a given utility service area. In order to create a practical tool for assessing reliability worth, interruption costs must be related to the calculated indices used in system planning and operation. This paper uses two different approaches and a customer damage function to evaluate a factor designated as the Interrupted Energy Assessment Rate (IEAR) which can be used in conjunction with the calculated expected energy not supplied in the assessment of reliability worth.
108 citations
TL;DR: From this comparison a new dynamic estimator which incorporates the main advantages of the previous estimators is proposed and a new scheme of detection and identification of bad data properly built for dynamic algorithms is presented.
Abstract: This paper presents a comparison between the performance of dynamic and tracking estimators, in power systems operating under quasi-static conditions, concerning their characteristics of forecasting and filtering. From this comparison a new dynamic estimator which incorporates the main advantages of the previous estimators is proposed. Also, a new scheme of detection and identification of bad data properly built for dynamic algorithms is presented. Numerical results showing the performance of the new algorithm under different operational conditions are discussed.
TL;DR: In this paper, a Lagrangian decomposition and successive approximation technique is used to solve the unit commitment problem in the presence of fuel constraints, where the generation, reserve and fuel constraints are adjoined onto the cost function using Lagrange multipliers.
Abstract: The unit commitment problem involves finding the hourly commitment schedule for the thermal units of an electrical system, and their associated generation, over a period of up to a week. For some utilities, contractual or other factors limit the amount of fuel available to certain of the units or plants. This paper describes a new method which solves the unit commitment problem in the presence of fuel constraints. The method uses a Lagrangian decomposition and successive approximation technique for solving the unit commitment problem where the generation, reserve and fuel constraints are adjoined onto the cost function using Lagrange multipliers. All important operating constraints have been incorporated including minimum up and down times, standby operation, ramping limits, time-dependent start-up cost, spinning and supplemental reserve. The method is being applied to a production-grade program suitable for Energy Management Systems applications.
TL;DR: In this article, a new method for minimizing transmission line losses and improving voltage profile in a given system by adjusting control variables, i.e., tap position of transformers and reactive power injection of VAR sources, is presented.
Abstract: This paper presents a new method for minimizing transmission line losses and improving voltage profile in a given system by adjusting control variables, i.e., tap position of transformers and reactive power injection of VAR sources. Transmission losses are considered as a function of voltage increments. The control variables and voltage increments are related by a modified Jacobian matrix. Linear Programming (LP) is used to calculate the voltage increments which minimize the transmission losses, and the adjustments of control variables are obtained by a modified Jacobian matrix. Since this method does not need any matrix inversion, it will save computational time and memory space.
TL;DR: In this article, a new method for simultaneously selecting the power system stabilizer (PSS) parameters in multimachine power systems is presented, where exact model reduction based on modal control theory is proposed to make the determination of PSS parameters highly efficient.
Abstract: This paper presents a new method for simultaneously selecting the power system stabilizer (PSS) parameters in multimachine power systems. Design of local output feedback power system stabilizer using local signal of the generator (e.g. speed or power) is formulated as a decentralized modal control (DMC) problem. Exact model reduction based on modal control theory is proposed to make the determination of PSS parameters highly efficient. Results obtained from the coordinated tuning of the parameters of three power system stabilizers equipped on a multimachine power system show that exact assignment of the eigenvalues associated with the poorly damped electromechanical modes can be achieved in a very efficient manner.
TL;DR: In this article, the authors examined the various factors affecting the damping characteristics of low frequency oscillations which caused dynamic instability problem in the operation of Taiwan power system and showed that power system stabilizers can be employed as an effective means for improving dynamic stability.
Abstract: Sustained low frequency oscillations have been observed in Taiwan power system which is of longitudinal structure. It is the purpose of this paper to examine the various factors affecting the damping characteristics of these oscillations which caused dynamic instability problem in the operation of Taiwan power system. It is observed that the amount of power flow on the EHV transmission line and the characteristics of load have a significant effect on the damping of the system while the speed-governing system and the gain of automatic voltage regulator have only a minor one. Detailed investigation using both the frequency domain and time domain approaches also reveals that power system stabilizers can be employed as an effective means for improving dynamic stability of Taiwan power system.
TL;DR: In this paper, an investigation of several methods for aggregating induction motors is described and the accuracy of the methods is compared using frequency-domain techniques, and a new method involving the use of one or two aggregate motors was described and shown to be superior to other methods.
Abstract: An investigation of several methods for aggregating induction motors is described. The accuracy of the methods is compared using frequency-domain techniques. A new method involving the use of one or two aggregate motors is described and shown to be superior to other methods.
TL;DR: In this article, the authors presented a novel methodology for feasibility analysis and design of optimal decentralized load frequency control for multi-area interconnected electric power systems, where the eigenvalue sensitivity expressions were used to determine decentralized feedback gains that will result in system transient performance similar to the one obtained with a centralized optimal control law.
Abstract: The paper presents a novel methodology for feasibility analysis and design of optimal decentralized load frequency control for multi-area interconnected electric power systems. Feasibility of the proposed decentralized control scheme is determined with a fixed mode evaluation algorithm based on eigenvalue dynamics. The eigenvalue sensitivity expressions are also used to determine decentralized feedback gains that will result in system transient performance similar to the one obtained with a centralized optimal control law. The methodology is illustrated with a two-area power system example.
TL;DR: In this article, a new method for solving efficiently a large-scale optimal unit commitment problem is presented, which includes three types of units (i) usual thermal units, ii) fuel constrained thermal units and iii) pumped-storage hydro units.
Abstract: This paper presents a new method for solving efficiently a large-scale optimal unit commitment problem. Our problem includes three types of units (i) usual thermal units, (ii) fuel constrained thermal units and (iii) pumped-storage hydro units. The solution method uses a Lagrangian relaxation. For maximizing the Lagrangian function, a 'variable metric method' is tried instead of the subgradient method. Moreover, a new device for efficiently obtaining a feasible solution is proposed. This leads to very good numerical results. All important operating constraints are incorporated.
TL;DR: The technique known as the waveform relaxation has been extensively used in transient analysis of VLSI circuits and it can take advantage of new architectures in computer systems such as parallel processors.
Abstract: In this paper, a new methodology for power system dynamic response calculations is presented. The technique known as the waveform relaxation has been extensively used in transient analysis of VLSI circuits and it can take advantage of new architectures in computer systems such as parallel processors. The application in this paper is limited to swing equations of a large power system. Computational results are presented.
TL;DR: In this article, an approach to modeling, analysis, and design of slow distributed voltage control schemes is proposed, in particular, a dynamical voltage model governed by the under load tap-changing transformers as control tools is studied.
Abstract: In this paper, an approach to modeling, analysis, and design of slow distributed voltage control schemes is proposed. In particular, a dynamical voltage model governed by the under load tap-changing transformers as control tools is studied. Rigorous conditions are derived to predict when the LTC based scheme may be poorly coordinated and not able to maintain voltages within the limits. The proposition is that nonconvergence of LTC control scheme is one of the causes of a systemwide voltage collapse.
TL;DR: A method is given for computing matrix reductions for power flow equivalents that is many times faster than presently used methods and produces extremely sparse equivalents and it is possible to embed the method in a power flow solution algorithm so that equivalencing can be performed automatically and transparently.
Abstract: A method is given for computing matrix reductions for power flow equivalents that is many times faster than presently used methods and produces extremely sparse equivalents. It is possible to embed the method in a power flow solution algorithm so that equivalencing can be performed automatically and transparently. The method is based on a property of sparse matrix factorization. When a matrix has been factorized, most of the operations for any reduction of the matrix have already been performed. Any desired reduction can be computed from the factors with relatively few additional operations. The performance of the method has been verified on large practical problems.
TL;DR: The main feature of the HSA code is a dynamic base choice that enables the decision maker to improve the convergence of the optimization procedure by the use of his practical experience.
Abstract: In this paper a Hydrothermal Scheduling Algorithm (HSA) for deterministic inflows is presented. A nonlinear network flow model representing the hydrothermal scheduling problem is used. By exploiting the special network structure, a temporally expanded arborescence [1], the HSA code attains important computational savings in processing time and memory requirements allowing the use of microcomputers even for large scale problems. The main feature of the HSA code is a dynamic base choice that enables the decision maker to improve the convergence of the optimization procedure by the use of his practical experience. The performance of the algorithm is tested on the Southeast Brazilian Power System.
TL;DR: In this paper, a Newton optimal power flow program was developed for the Ontario Hydro Energy Management System, which combines the fast convergence of the Newton technique with the speed and reliability of Linear Programming.
Abstract: A Newton optimal power flow program was developed for the Ontario Hydro Energy Management System. Each iteration minimizes a quadratic approximation of the Lagrangian. All the equations are solved simultaneously for all the unknowns. A new technique based on linear programming is used to identify the binding inequalities. All binding constraints are enforced using Lagrange multipliers. The algorithm combines the fast convergence of the Newton technique with the speed and reliability of Linear programming. Most cases converged in three iterations or less.
TL;DR: In this article, an adaptive, weather sensitive, short term load forecast algorithm was developed for two South Carolina Power Systems: CEPCI (Central Electric Power Cooperatives, Inc., Central for short) and Combined System.
Abstract: This paper introduces an adaptive, weather sensitive, short term load forecast algorithm that has been developed for two South Carolina Power Systems: CEPCI (Central Electric Power Cooperatives, Inc., Central for short) and Combined System. The model is based on a State Space formulation specially tailored for this application. A detailed correlation study is performed to identify the most relevant weather variables. Different models are used for Summer and Winter, since different weather variables are found to be relevant in both seasons. Adaptivity is attained through careful usage of Kalman filtering and Bayesian techniques. An appropriate methodology is developed to identify and correct anomalous load data and to model nonconforming loads. A new technique is introduced for "filling in" weather forecasts. The model has been sucessfully implemented using state-of-the-art data-base and man-machine techniques. Implementation results are reported. This model benefits from the experience gained using a variety of tools and represents important enhancements over existing methods.
TL;DR: In this article, a systematic procedure is developed to locate reactive power devices in a power system based on a set of indices, that are based on overall system conditions, and after identifying the desired locations, the cost of installation and number of reactive power device, subject to any required practical and real economic constraints, are minimized.
Abstract: A systematic procedure is developed to locate reactive power devices in a power system based on a set of indices, that are based on overall system conditions. After identifying the desired locations, the cost of installation and number of reactive power devices, subject to any required practical and real economic constraints, are minimized. Existing controllers are fully utilized before adding any new devices. Linearized sensitivity relationships of power systems are used to obtain an objective function for minimizing the cost of installation. The constraints include the limits on dependent variables (reactive powers of the generators, load bus voltages) and control variables (generator voltages, tap positions, switchable reactive power sources). A parametric linear programming technique based on active set analysis is proposed to solve the reactive power allocation problem.
TL;DR: In this paper, three simulation models of a typical distribution system are developed and applied to an actual feeder and the results are analyzed to show the advantages and disadvantages of each model and the conclusion is that it is possible to reduce many complex feeders to simple models in the study of feeder voltage profiles and losses with negligible error.
Abstract: Three models of a distribution system are developed in this paper. Included are descriptions of simulation models of the diverse components of a typical distribution system. The three system models are illustrated by examples. They are applied to an actual feeder and the results are analyzed to show the advantages and disadvantages of each model. A unique method is developed for combining the discrete distributed load voltage drop solution with the discrete distributed load losses solution. The development of this combined method is in the form of a tutorial , as are the developments of the components of this method. The conclusion is reached that it is possible to reduce many complex feeders to simple models in the study of feeder voltage profiles and losses with negligible error.
TL;DR: In this article, an alternative approach for power system stabilization based upon the tuning of the existing generator controllers, both governors and A.V.R.'s, is presented, where the sensitivities of the eigenvalues to the controller parameters are evaluated and an optimization technique is developed to maximize the dynamic stability.
Abstract: Dynamic stability problems are usually overcome through the application of Power System Stabilizers. This paper presents an alternative approach for power system stabilization based upon the tuning of the existing generator controllers, both governors and A.V.R.'s. The sensitivities of the eigenvalues to the controller parameters are evaluated and an optimization technique is developed to maximize the dynamic stability. Application of the parameter optimization method on a realistic model of the Hellenic Interconnected System has proved an efficient way to stabilize a number of unstable oscillatory modes by relatively small parameter variations. The results are tested with a nonlinear simulation program and the achieved stabilization, as shown by the rotor angle swings, is found to be significant.
TL;DR: The spectrum of power system operating problems that are believed to be good candidates for Artificial Intelligence (AI) solution are described and their characteristics and why they are candidates for AI are discussed.
Abstract: This paper is one of a series for use in Current Operational Problems (COPS) Forums with the goal of focusing attention on problems faced by electric utility operators. These short notes are intended to describe the problems and the complexity of solution to the problems. The short note papers presented here describe the spectrum of power system operating problems that are believed to be good candidates for Artificial Intelligence (AI) solution. The first short note lists many of these applications and discusses their characteristics and why they are candidates for AI. The second describes an existing application that uses a knowledge base derived from operator experience. The third describes a research project now being conducted toward solving the alarm processing problem and the last short note introduces some of the problems to be encountered in implementing AI in an energy management system.
TL;DR: In this article, a symbolic reduction of the measurement Jacobian matrix without its actual computation is presented, and the results of the algorithm application in the Energy Management System (EMS) of a large electric utility are given.
Abstract: A method of observability analysis for the state estimation in power systems is presented. The method is based on a symbolic reduction of the measurement Jacobian matrix without its actual computation. The algorithm is characterized as being extremely simple and fast. The results of the algorithm application in the Energy Management System (EMS) of a large electric utility are given.
TL;DR: An overview of the analytical and computational problems encountered in the large scale application of the TEF method is presented, and approaches used to overcome the problems are provided.
Abstract: This paper deals with the demonstration of the Transient Energy Function (TEF) method in large, realistic power networks. Documented examples of application in power system operation and associated software development for systems up to 228-generators and 1644-buses are given. An overview of the analytical and computational problems encountered in the large scale application of the TEF method is presented. Approaches used to overcome the problems are provided, and the relevant improvements and modifications to the TEF software are discussed.