Showing papers on "Power-flow study published in 1987"
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.
66 citations
TL;DR: The various optimization criteria are discussed for determining the optimal capacitor for power factor correction and the performance of the obtained capacitor is discussed by means of numerical examples.
Abstract: This paper deals with the correction of the power factor of the load when the bus voltage contains harmonics. The various optimization criteria are discussed for determining the optimal capacitor for power factor correction, The performance of the obtained capacitor is discussed by means of numerical examples.
28 citations
TL;DR: From the results of experiment, it was demonstrated that stabilizing effect by means of SMES is very significant.
Abstract: This paper presents the experimental results of stabilization of a model power transmission system by using a Superconducting Magnet Energy Storage (SMES). The SMES, which was composed of two sets of GTO (Gate Turn Off thyristor) power converters and a superconducting coil, is capable of controlling active power (P) and reactive power (Q) simultaneously in four quadrants by changing the firing angles of power converters. The model power transmission system was designed to simulate the behavior of a real scale long distance bulk power transmission system with voltage of 500 kV, capacity of 2000 MVA and length of 280 km. In this study, we have experimented power system stabilizing control by applying P-Q simultaneous control ability of SMES. From the results of experiment it was demonstrated that stabilizing effect by means of SMES is very significant.
21 citations
21 citations
Proceedings Article•
01 Jan 1987
TL;DR: In this article, the authors present the mathematical techniques to quantify the energy replacement and capacity benefits of wind power in thermal and large hydroelectric power systems using a modified version of the WASP-program.
Abstract: The subject of this paper is to present the mathematical techniques to quantify the energy replacement and capacity benefits of wind power in thermal and large hydro-electric power systems. The paper is an extension of the paper "Modelling of wind power" presented at the 8th PSCC in Helsinki, 1984.Wind power is represented as a multistate model which is convolved into the equivalent load duration curve. A modified version of the WASP-program, which handles the wind power model, is used to perform the calculations. WASP uses probabilistic production costing techniques.Results obtained from a case study with a future Swedish system including wind power is presented.
13 citations
TL;DR: The proposed method, which is derived from a Z-loop analysis, is very straightforward and simple without unnecessary mathematical approximations, and is attractive for accurate or approximate off-line and on-line routines and contingency calculations for radial systems.
12 citations
01 Dec 1987
TL;DR: In this paper, an efficient two stage monitoring technique for power system stability was developed in the course of a DOE sponsored project at Washington University, which utilizes an unusually effective technique for identifying coherent dynamic clusters within a power system and the connections between the clusters and critical swings in the power system.
Abstract: This paper summarizes an efficient two stage monitoring technique for power system stability which was developed in the course of a DOE sponsored project [9] at Washington University. The process utilizes an unusually effective technique [6] for identifying coherent dynamic clusters within a power system and the connections between the clusters and critical swings in the power system. In the first stage transient energy injected into the power system is compared with critical energies which can drive the cluster into separation. Failing this sufficiency test the condition then is evaluated by testing the initial states position directly with respect to the stability boundary. An efficient expansion which is easily derived on the computer is used. Only one scalar value needs to be computed for each candidate. Theoretical basis for this work was developed in [9] and is to be published soon in the AC Transactions [4]. New theoretical, computational results on identifying order N-1 equilibria is also given in this paper.
12 citations
TL;DR: In this paper, a detailed reconstruction of the dynamic behaviour of the West European Power System was made in which all main transmission lines and power plants were reproduced individually. But the accuracy and the efficiency of this reconstruction with up to 413 power plants, 984 nodes, and a corresponding number of dynamic loads was verified by the comparison with real disturbance cases, e.g. switching off of power plants and transmission lines.
10 citations
01 Dec 1987
TL;DR: In this paper, a general review of the small signal analysis of power systems is given and the special requirements for the analysis of very large systems are stressed and a number of methods, recently developed for such analysis, are discussed in detail.
Abstract: The size of the interconnected power system in North America has grown to such an extent that, if dc links are included, all utilities in the U.S. and Canada form constituent parts. Recent economic and environmental pressures have caused the system to become more highly stressed than in the past and this has caused low frequency, highly oscillatory modes to have been observed on the system on a number of occasions. These low frequency modes have been found to be caused by groups of relatively closely coupled machines, oscillating across weak transmission links. For such modes, the normally used reduction techniques may not be sufficiently accurate and, consequently there is a need to study the problem using very large power sytem models. In this paper, a general review of the small signal analysis of power systems is given. The special requirements for the analysis of very large systems are stressed and a number of methods, recently developed for such analysis, are discussed in detail. Those problem areas still to be resolved are identified and suggestions are made for the future development of power system small signal analysis programs.
9 citations
TL;DR: In this article, the authors present a model for the full AC load-flow calculation based on a simplifying assumption which will allow decoupling of the problem and which is the basis of the algorithm called FLF (Flow Load-Flow algorithm).
Abstract: Operational research methods, and particularly flow and transportation methods have many applications in the power system field: optimization of hydroelectric power system operation, seasonal or short-time planning of a hydro-thermal system and finally power system security. The purpose of this paper is to specify the network simplex method of the load-flow calculation in a power system. This study is not limited to the DC-flow calculation but particularly presents a model for the full AC load-flow calculation. The proposed model is an imaginary and real current one. It is based on a simplifying assumption which will allow decoupling of the problem and which is the basis of the algorithm called FLF (Flow Load-Flow algorithm). Power system elements such as lines, transformers, generators and voltage control busses are represented with adapted models. Systematic tests have been performed on some existing power systems, such as the IEEE 24-bus Reliability system. The performance of this method is compared with the results of a decoupled Newton-Raphson load-flow. The accuracy of the FLF algorithm is competitive with the Newton-Raphson method, but its speed still has to be improved. However the load-flow calculation is only a part of the power system security problem, where properties and characteristics of flow and transportation algorithms will offer greater perspective.
TL;DR: In this article, a new power-flow formulation based on Newton's method is described which can aid in determining the area of the power system in which a load has been incorrectly estimated.
Abstract: Design of a mine electric power system requires that power flow studies be conducted to guarantee that all motor operating and starting loads can be met while maintaining acceptable bus voltage levels. If future loads are overestimated, then the iterative technique used to solve for the system voltage profile will often diverge, leaving no clue for the designer as to the cause of the divergence. A new power-flow formulation based on Newton's method is described which can aid in determining the area of the power system in which a load has been incorrectly estimated. Experimentation with this formulation shows that mismatches tend to be concentrated at an overloaded bus. Inspection of the mismatches saves the system designer time by pointing out areas of the system where a problem, such as an incorrectly specified bus load, may exist.
01 Jan 1987
TL;DR: An overall view of thePLF problem and methods of solution is presented and in order to illustrate the main features of the probabilistic analysis over the conventional one, the PLF technique is applied to a part of the brazilian system to provide adequacy indices for the operation planning phase.
Abstract: The load flow analysis is undoubtedly the most useful study made for designing and operating power systems. The necessary input data for these studies are better described by random variables considering the probabilistic nature of loads, generation and network. The effects of these uncertainties on the steady-state behaviour of power systems are evaluated by a stochastic or probabilistic load flow (PLF) analysis. This paper presents an overall view of the PLF problem and methods of solution. Also, in order to illustrate the main features of the probabilistic analysis over the conventional one, the PLF technique is applied to a part of the brazilian system (69/138 KV network with 84 busbars) to provide adequacy indices for the operation planning phase. Details on the collection and modelling of probabilistic data, utility's operating policy and other constraints of the studied system are included.
14 Jun 1987
TL;DR: In this article, the reliability and availability performance of a telecom power system is evaluated using Markov chains in steady-state conditions assuming expotential distributions, and the results together with their dependence on various system parameters are discussed.
Abstract: Methods used to evaluate reliability and availability performance of telecom power systems are described. The models are based on Markov chains in steady-state conditions assuming expotential distributions. The models and methods normally used have been developed further in order to obtain more numerical information on the effects of monitoring systems and operating practices of maintenance staff on power system reliability and availability performance. In addition, a telecom power system is analyzed, and results together with their dependence on various system parameters are discussed.
TL;DR: In this paper, a decoupled and decomposed power flow solution method is derived and discussed, in which the active power flow model is decomposed into the mutually connected generator active and load reactive power flow models.
TL;DR: In this paper, a general approach to modeling and synthesis of harmonic-free power conversion systems is presented, where the desired power conversion is achieved by controlling the transfer ratio of a time-varying network which couples the load to the source.
Abstract: A general approach to modeling and synthesis of harmonic-free power conversion systems is presented. The desired power conversion is achieved by controlling the transfer ratio of a time-varying network which couples the load to the source. Applying this method, harmonic-free volt-amperes reactive (var) power generation can be achieved by systems which do not include any storage elements. On the other hand this approach is suitable for simple modeling of existing efficient var compensators and power conversion circuits.
01 Dec 1987
TL;DR: In this article, an attempt is made to formulate potential problems in the operation of large electric power systems under the changing strategies currently taking place and the control actions are needed to compensate for this factor.
Abstract: In this paper an attempt is made to formulate potential problems in the operation of large electric power systems under the changing strategies currently taking place. The system operates at the conditions for which it was not originally designed and the control actions are needed to compensate for this factor. If the normal operating conditions are such that large reactive power is transferred over the large distances, any unplanned event (line, generator, load outage) could lead the system to severe voltage problems. Control means for preventing this from happening are illustrated on two system examples.
TL;DR: In this paper, a real-time algorithm for solving the optimal control strategies of reactive power and voltage in distribution systems is proposed, under the conditions of bus voltage, branch reactive power used as controlled variables and the setting of the Tap Changing Under Load Transformers, reactive power compensation used as control variables.
TL;DR: From the view of economy and security of a power system, a synthetic mathematical model is presented for minimizing system losses and improving voltage level and the algorithm available for optimal control of voltage and reactive power of power system is presented.