Showing papers in "IEEE Power & Energy Magazine in 1981"
TL;DR: In this paper, the general concepts associated with applying power system stabilizers utilizing shaft speed, ac bus frequency, and electrical power inputs are developed in the first part of a three-part paper.
Abstract: The general concepts associated with applying power system stabilizers utilizing shaft speed, ac bus frequency, and electrical power inputs are developed in this first part of a three-part paper. This lays the foundation for discussion of the tuning concepts and practical aspects of stabilizer application in Parts II and III. The characteristics of the "plant" through which the power system stabilizer must operate are discussed and the implications upon stabilizer tuning and performance are noted. A general approach for analyzing stabilizers utilizing an arbitrary input signal is described and applied to the frequency and electrical power input signals.
940 citations
TL;DR: A load flow calculation method for ill-conditioned power systems is developed, and it is found that the solution does not exist for the 11 and 43 bus systems though the given data are said to be operational, and also that the answer does not converge with the single precision due to the precision deficiency of the computer.
Abstract: In this paper, a load flow calculation method for ill-conditioned power systems is developed. The proposed method is very simple, has no mathematical approximations, and requires almost no additional storage and computation time when incorporated into the normal Newton-Raphson program. Using the method, the load flow solution never diverges, and also the existence of the solution from the initial estimate can be easily judged. To examine the effectivenesst two ill-conditioned power systems, i.e., 11 and 43 bus systems are studied by the method, and it is found that the solution does not exist for the 11 bus system though the given data are said to be operational, and also that the solution does exist for the 43 bus system but does not converge with the single precision due to the precision deficiency of the computer.
411 citations
TL;DR: In this article, the authors introduce the concept of an ideal (superconducting) current return plane placed below the ground surface at a complex distance p equal to the complex penetration depth for plane waves.
Abstract: For modelling current return in homogeneous ground, the paper introduces the concept of an ideal (superconducting) current return plane placed below the ground surface at a complex distance p equal to the complex penetration depth for plane waves. This "complex" plane appears as a mirroring surface, so that conductor images can be used to derive very simple formulae for self and mutual impedances under ground return conditions. Such equations, without proofs, were originally proposed by Dubanton and published by Gary.1 In this paper, plausibility arguments serve to initially justify the procedure, then the equations are analytically related to those of Carson and, finally, the errors, which in most cases are less than a few percent, are numerically evaluated. The ideal return plane at complex depth can also be used for multi-layer earth return.
378 citations
TL;DR: This paper presents a new method for obtaining a probabilistic load flow solution using a discrete frequency domain convolution technique that has greater accuracy while providing a breakthrough in computational speed.
Abstract: This paper presents a new method for obtaining a probabilistic load flow solution using a discrete frequency domain convolution technique. It is shown that this method has greater accuracy while providing a breakthrough in computational speed. A detailed example compares the numerical results with a Monte Carlo simulation. The effects of nonlinearity in the network equations are discussed.
373 citations
TL;DR: In this paper, a mathematical formulation of the optimal reactive power control (optimal VAR control) problem and results from tests of the algorithm are presented in order to minimize the real power losses in the system.
Abstract: A mathematical formulation of the optimal reactive power control (optimal VAR control) problem and results from tests of the algorithm are presented in this paper. The model minimizes the real power losses in the system. The constraints include the reactive power limits of the generators, limits on the load bus voltages, and the operating limits of the control variables, i.e., the transformer tap positions, generator terminal voltages and switchable reactive power sources. Real power economic dispatch is accomplished by standard techniques.
367 citations
TL;DR: In this article, it is shown that normal wind variations can excite this mode resulting in large oscillatory fluctuations in the drive train torques as well as in the generated electric power.
Abstract: Common in the design of wind turbine generators of the multi-megawatt size is a soft shaft in the low speed part of the drive train. The presence of the soft shaft gives rise to a low frequency torsional mode involving an oscillation where the hub and blades swing relative to the generator. It is shown that normal wind variations can excite this mode resulting in large oscillatory fluctuations in the drive train torques as well as in the generated electric power. Methods of improving the dynamic performance are examined.
303 citations
TL;DR: In this article, the authors compared the performance of four unit commitment methods, three of which are based on the dynamic programming approach, and presented the modeling of inter-area flow constraints by linear flow network, so that such multi-area representation recognizes any existing transmission limitations.
Abstract: This paper compares the performance of four unit commitment methods, three of which are based on the dynamic programming approach. The paper also presents the modeling of inter-area flow constraints by linear flow network, so that such multi-area representation recognizes any existing transmission limitations which are normally ignored in most unit commitment methods. To assure realistic results, data for two large systems (up to 96 units) were used: EPRI Scenario System C and a midwestern utility. Unit commitment results for these two systems are presented in the paper and they demonstrate the importance of multiple area representation of a system in unit commitment. Such representation affects the schedule costs and assures the determination of realizable schedules.
278 citations
TL;DR: In this paper, a general, physically based, probabilistic model of power system load has been developed for short-term prediction of system demand by composition, and accounts for lifestyle dependency and weather dependency as well as effects of other exogenous processes.
Abstract: A general, physically based, probabilistic model of power system load has been developed [1]. The model is suitable for short-term prediction of system demand by composition, and accounts for lifestyle dependency and weather dependency as well as effects of other exogenous processes. The conceptual framework and notation applicable to a wide range of load modeling problems have been the key issues in developing a general model.
276 citations
TL;DR: In this paper, a set of Generalized Generation Distribution Factor (GGDF) is developed to replace the conventional GDF's, which are especially suitable for constraint formulation in mathematical programning, such as optimal generation dispatch with security contingencies considered.
Abstract: A set of Generalized Generation Distribution Factors (GGDF's) is developed to replace the conventional Generation Shift Distribution Factors (GSDF's). This model relates the line flows with generations for a given network configuration. Being in an integral form, new flows on lines can be obtained directly without running load flows when total system generation changes. Conforming load change is also demonstrated. These new factors are especially suitable for constraint formulation in mathematical programning, such as optimal generation dispatch with security contingencies considered
263 citations
TL;DR: In this paper, the performance objectives of power system stabilizers in terms of the type of oscillations for which they are intended to provide damping, operating conditions for which the requirement for stabilization is greatest, the need to accommodate multiple modes of oscillation, and the significance of interplant modes.
Abstract: This part of a three-part paper deals first with the performance objectives of power system stabilizers in terms of the type of oscillations for which they are intended to provide damping, the operating conditions for which the requirement for stabilization is greatest, the need to accommodate multiple modes of oscillation, and the significance of interplant modes of oscillation. It next treats stabilizer tuning. General tuning guidelines are developed as well as variations required for different input signals. The operating conditions under which each type of stabilizer should be tuned are identified. The relationship between phase compensation tuning and root locus analysis is presented. Finally, the relative performance characteristics of the three types of stabilizers are examined for both small perturbations and large disturbances.
214 citations
TL;DR: In this article, the authors present an advanced contingency selection algorithm, which is essentially equivalent to a ranking based on the results of a DC load flow of each case, only at a fraction of the calculation time.
Abstract: This paper reports on the development of an advanced contingency selection algorithm giving superior results compared to earlier techniques. Problems inherent in the earlier algorithm resulted in occasional misranked contingency cases. The new algorithm gives results which are essentially equivalent to a ranking based on the results of a DC load flow of each case, only at a fraction of the calculation time. A complete derivation, test results and applications are given in the paper.
TL;DR: In this article, a technique for selecting the parameters of stabilizers in multimachine power systems is presented, which enables the selection of the stabilizers such that specified improvements in the damping ratios of the poorly damped modes of oscillation are realized approximately.
Abstract: This paper presents a technique for selecting the parameters of stabilizers in multimachine power systems. The technique enables the selection of the parameters of stabilizers such that specified improvements in the damping ratios of the poorly damped modes of oscillation are realized approximately. A numerical example of a multimachine system is presented to illustrate the proposed technique.
TL;DR: In this article, the practical considerations associated with applying power system stabilizers are addressed in this final part of the paper and procedures are described whereby the tuning concepts developed in Part II may be implemented in the field.
Abstract: The practical considerations associated with applying power system stabilizers are addressed in this final part of the paper. Procedures are described whereby the tuning concepts developed in Part II may be implemented in the field. An approach is described for determining the "plant" characteristics for which a stabilizer must compensate. Guidelines are presented for adjustment of stabilizer parameters, inclduing frequency-response, gain, and output limits. Techniques are described for verification of proper stabilizer set-up.
TL;DR: In this article, the authors describe the system outline and the operating results of a new type of 20MVA Static VAR Generator (SVG), which is already in operation in electric power field since January of 1980.
Abstract: This paper describes the system outline and the operating results of a new type of 20MVA Static VAR Generator (SVG), which is already in operation in electric power field since January of 1980. This SVG consists of force-commutated inverters of the voltage source and can be operated in both, inductive and capacitive modes, by simple control of the output voltage of the inverter. Special emphasis is placed on the system outline, electrical designing features and the operating results which coincide with the theoretical analysis.
TL;DR: In this paper, a hierarchical concept is used to solve the static state estimation problem for large-scale composite power systems, and the solution is obtained by performing a two-level calculation.
Abstract: A hierarchical concept is used to solve the static state estimation problem for large-scale composite power systems. The solution is obtained by performing a two-level calculation. In the lower level, a conventional state estimation is carried out simultaneously for all subsystems. The coordination of these local estimations is realized in the upper level. One of the main contributions of the paper lies in the construction of an appropriate second-level algorithm. Its suitability and also the main features of the overall procedure are then explored and illustrated on the basis of the Belgian 380-220-150 kV transmission network. Comparisons with the standard "integrated" state estimation are also performed.
TL;DR: In this paper, the authors developed the theoretical basis for determining the bad measurement detectability properties of the state estimator from the topology of the 1-line diagram and the locations of the measurements.
Abstract: A power system static-state estimator has the ability to detect and purge some measurement errors. This paper develops the theoretical basis for determining the bad measurement detectability properties of the state estimator from the topology of the 1-line diagram and the locations of the measurements. Based on this theory, an algorithm is described that: 1) identifies those measurements that have detectable error residuals; and 2) determines the regions of measurement error residual spread.
TL;DR: In this paper, a new method for calculating electric field and ion current caused by overhead DC transmission lines without using the commonly used approximation, Deutsch's assumption, is described, which is generally applicable to all monopolar and bipolar cases including grounded wires and wind.
Abstract: The paper describes a new method for calculating electric field and ion current caused by overhead DC transmission lines without using the commonly used approximation, Deutsch's assumption. Unknown space functions, i.e. potential, positive and negative ion densities, are iteratively calculated from the coupled differential equations by the finite element method (FEM). The program is generally applicable to all monopolar and bipolar cases including grounded wires and wind. Emphasis is placed on numerical stability and reduced human task in the FEM computation.
TL;DR: In this paper, a distribution planning model is formulated which considers existing and potential substation locations, their capacities and costs, together with the primary feeder network represented by small area demand locations to represent non-uniform loads, and feeder segments having variable distribution costs and limited capacities.
Abstract: A distribution planning model is formulated which considers existing and potential substation locations, their capacities and costs, together with the primary feeder network represented by small area demand locations to represent non-uniform loads, and feeder segments having variable distribution costs and limited capacities. A branch and bound search method is described which utilizes a shortest path table to obtain lower bounds and solutions from a transshipment linear programming model for upper bounds. The solution of a small example is presented in detail, and computational results for several larger problems are summarized.
TL;DR: The slow coherency concept is introduced and an algorithm is developed for grouping machines having identical slow motions into areas as discussed by the authors, where the singular perturbation method is used to separate the slow variables which are the area center of inertia variables and the fast variables which describe the intermachine oscillations within the areas.
Abstract: The slow coherency concept is introduced and an algorithm is developed for grouping machines having identical slow motions into areas. The singular perturbation method is used to separate the slow variables which are the area center of inertia variables and the fast variables which describe the intermachine oscillations within the areas. The areas obtained by this method are independent of fault locations. Three types of simulation approximations illustrated on a nonlinear 48 machine system indicate the validity of this algorithm.
TL;DR: A new technique for modelling the signal and the measurements is developed based on Kalman Filtering theory for the optimal estimation of the 60 Hz information and results indicate that the technique converges to the true 60 Hz quanitities faster than other algorithms that have been used.
Abstract: During the first cycle following a power system fault, a high speed computer relay has to make a decision usually based on the 60 Hz information, which is badly corrupted by noise The noise in this case is the nonfundamental frequency components in the transient current or voltage, as the case may be For research and development purposes of computer relaying techniques, the precise nature of the noise signal is required The autocorrelation function and variance of the noise signal was obtained based on the frequency of occurrence of the different types of faults, and the probability distribution of fault location A new technique for modelling the signal and the measurements is developed based on Kalman Filtering theory for the optimal estimation of the 60 Hz information The results indicate that the technique converges to the true 60 Hz quanitities faster than other algorithms that have been used The new technique also has the lowest computer burden among recently published algorithms and appears to be within the state of the art of current microcomputer technology
TL;DR: In this paper, the probabilistic analysis of transient stability of a simple single machine-infinite bus system is presented. But the authors focus on the most critical line in the system and do not consider the effect of fault clearing and reclosing times on the system stability.
Abstract: The application of probabilistic techniques in the quantitative evaluation of power system reliability is steadily increasing. Probability methods are being used extensively in the assessment of static adequacy. Their application to the evaluation of transient or dynamic phenomena has not yet, however, been widely utilized. The probabilistic nature of the transient stability problem and the inclusion of the probabilities associated with the initiating factors such as the type, location and clearance of faults in the analysis of a simple single machine-infinite bus system has been demonstrated in a recent paper.1 The present paper addresses the problem of transient stability analysis in a practical multimachine system from a probabilistic view-point. The basic concepts developed in Reference ! are applied to a simplified 33 bus model based on the Saskatchewan Power Corporation (SPC) system, to demonstrate the technique of considering the probabilities associated with the occurrence and clearance of faults. Transient stability indices for each line, for different types of faults and a single stability index for any fault are obtained. A single stability index for the overall system is evaluated for different fault types and amy fault using actual system outage statistics. The effect of fault clearing and reclosing times on the system stability is investigated for the most critical line in the system.
TL;DR: In this article, direct methods of transient stability analysis of a multi-machine power system, using a function describing the system's transient energy, are discussed, and the following fundamental questions are dealt with: the concept of a controlling unstable equilibrium point (u.p.), the manner in which some generators tend to lose synchronism, and identifying-the energy directly responsible for system separation.
Abstract: Direct methods of transient stability analysis of a multi-machine power system, using a function describing the system's transient energy, are discussed. By examining the trajectory of the disturbed system, the following fundamental questions are dealt with: the concept of a controlling unstable equilibrium point (u.e.p.), the manner in which some generators tend to lose synchronism, and identifying-the energy directly responsible for system separation. Resolving these issues will substantially improve transient stability analysis by a direct method.
TL;DR: In this article, a fault location algorithm based on the Fourier analysis of a faulted network is presented, which embodies an accurate location by measuring only a local end data, and its fundamental theory is studied through digital computer simulations on a model power system.
Abstract: A fault location algorithm based on the Fourier analysis of a faulted network is presented. The algorithm embodies an accurate location by measuring only a local end data. Its fundamental theory is studied through digital computer simulations on a model power system. With the practical applications in mind, fast algorithms are then examined. Finally, the experimental results of a computerized fault locator applied to a laboratory system are presented.
TL;DR: An efficient and reliable method for automatic contingency selection is presented based on the prediction of the value of a system wide performance index for each transmission line outage and the subsequent ranking of the severity of the outages according to the predicted values of the performance index.
Abstract: An efficient and reliable method for automatic contingency selection is presented. The method is based on the prediction of the value of a system wide performance index for each transmission line outage and the subsequent ranking of the severity of the outages according to the predicted values of the performance index.
TL;DR: In this paper a sequential algorithm for power system state estimation based on the use of Givens rotations is investigated, and the fact that the rotations are orthogonal transformations assures the numerical stability of the algorithm.
Abstract: In this paper a sequential algorithm for power system state estimation based on the use of Givens rotations is investigated. The fact that the rotations are orthogonal transformations assures the numerical stability of the algorithm. The Jacobian matrix is processed one row at a time, and sparsity can be easily exploited. Also, the method presents some features which are advantageous from the point of view of bad data detection, identification and elimination. Both the description and the implementation of a fast version of the Givens rotations are presented. The method is applied to three different power systems, including real size networks, and the results are used to assess its performance.
TL;DR: In this paper, a two-area reheat thermal system provided with classical controllers has been investigated, and the authors show that the optimal integral gain achieved through the continuous mode analysis is totally unacceptable in the discrete mode for the sampling periods used in practice.
Abstract: This paper deals with some aspects of sampled-data Automatic Generation Control (AGC) of a two-area reheat thermal system provided with classical controllers. Discrete mode optimization of such controllers using margin of stability and Integral Squared Error concepts have been attempted. Investigations rev eal that the optimal integral gain achieved through the continuous mode analysis is totally unacceptable in the discrete mode for the sampling periods used in practice Moreover, for all practical purposes the optimum integral gain in the discrete mode can be achieved by neglecting the generation rate constraints from the mathematical model unlike in the continuous mode. Performances of discrete optimum integral and optimum proportional-integral controllers have also been examined. Recommendation to optimum sampling period selection has also been attempted.
TL;DR: In this article, a numerically more reliable algorithm, known as Golub's method, was used to solve the least-squares problem as formulated in power system state estimation, which used orthogonal transformations, which are perfectly conditioned.
Abstract: It is well known in numerical analysis that the least-squares solution via the conventional Gauss' normal equation used in power system state estimation is prone to ill-conditioning problems by its own nature. Under unfavorable circumstances, this may be detrimental to the method's performance. This paper utilizes a numerically more reliable algorithm, known as Golub's method, to solve the least-squares problem as formulated in power system state estimation. Its improved numerical properties stem from the use of orthogonal transformations, which are perfectly conditioned. Details of the algorithm and its implementation are given, as well as results of its application to three different networks, including an actual 121-bus power system.
TL;DR: In this paper, the authors show that low frequency synchronizing oscillations between the Pacific Northwest and Pacific Southwest have long been a characteristic of the western power system and that these oscillations are due to a swing mode involving the whole western loop.
Abstract: Low frequency synchronizing oscillations between the Pacific Northwest and Pacific Southwest have long been a characteristic of the western power system. Recently new low frequency oscillations have been observed. Simulation results and an analytical model indicate these oscillations are due to a swing mode involving the whole western loop. System measurements show the mode can become poorly damped.