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Showing papers on "Electric power system published in 1990"


Journal ArticleDOI
TL;DR: In this paper, the authors present an energy fundiment analysis for power system stability, focusing on the reliability of the power system and its reliability in terms of power system performance and reliability.
Abstract: (1990). ENERGY FUNCTION ANALYSIS FOR POWER SYSTEM STABILITY. Electric Machines & Power Systems: Vol. 18, No. 2, pp. 209-210.

1,080 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a low-order system frequency response (SFR) model that can be used for estimating the frequency behavior of a large power system, or islanded portion thereof, in response to sudden load disturbances.
Abstract: The authors present the derivation of a simple, low-order system frequency response (SFR) model that can be used for estimating the frequency behavior of a large power system, or islanded portion thereof, in response to sudden load disturbances. The SFR model is a simplification of other models used for this purpose, but it is believed to include the essential system dynamics. The SFR model is based on neglecting nonlinearities and all but the largest time constants in the equations of the generating units of the power system, with the added assumption that the generation is dominated by reheat steam turbine generators. This means that the generating unit inertia and reheat time constants predominate over the system average frequency response. Moreover, since only two time constants predominate, the resulting system response can be computed in closed form, thereby providing a simple, but fairly accurate, method of estimating the essential characteristics of the system frequency response. >

631 citations


Journal ArticleDOI
TL;DR: In this article, the authors describe developments that have transformed the LP (linear programming) approach into a truly general-purpose OPF (optimal power flow) solver, with computational and other advantages over even recent nonlinear programming (NLP) methods.
Abstract: The authors describe developments that have transformed the LP (linear programming) approach into a truly general-purpose OPF (optimal power flow) solver, with computational and other advantages over even recent nonlinear programming (NLP) methods. it is pointed out that the nonseparable loss-minimization problem can now be solved, giving the same results as NLP on power systems of any size and type. Coupled formulations, where for instance voltages and VAr become constraints on MW scheduling, are handled. Former limitations on the modeling of generator cost curves have been eliminated. In addition, the approach accommodates a large variety of power system operating limits, including the very important category of contingency constraints. All of the reported enhancements are fully implemented in the production OPF software described here, and most have already been utilized within the industry. >

517 citations


Book
01 Jan 1990
TL;DR: Role of probability models in power system engineering concepts and theorems of probability random variables functions of random variables stochastic processes decision analysis reliability and Monte Carlo simulation elements of acceptance sampling.
Abstract: Role of probability models in power system engineering concepts and theorems of probability random variables functions of random variables stochastic processes decision analysis reliability probabilistic structural design and analysis of transmission systems preventive maintenance, inspection and replacement probabilistic load flow probabilistic short circuit analysis probabilistic power system stability Monte Carlo simulation elements of acceptance sampling.

363 citations


Journal ArticleDOI
TL;DR: In this paper, a mathematical framework is presented for the solution of the economic dispatch problem, and the application of the Dantzig-Wolfe decomposition method is emphasized to solve the problem.
Abstract: A mathematical framework is presented for the solution of the economic dispatch problem The application of the Dantzig-Wolfe decomposition method for the solution of this problem is emphasized The system's optimization problem is decomposed into several subproblems corresponding to specific areas in the power system The upper bound technique along with the decomposition method are applied to a 16-bus system and a modified IEEE 30-bus system, and numerical results are presented for larger systems The results indicate that the presented formulation of the reactive power optimization and the application of the decomposition procedure will facilitate the solution of the problem The algorithm can be applied to a large-scale power network, where its solution represents a significant reduction in the number of iterations and the required computation time >

342 citations


Journal ArticleDOI
TL;DR: In this paper, the authors expanded on the physical meaning of the reactive power in nonsinusoidal situations, and showed that the total reactive power Q/sub F/ is composed from four distinctive types of elementary reactive powers.
Abstract: The author expands on the physical meaning of the reactive power in nonsinusoidal situations. The sinusoidal waveform case is surveyed, viewing the active current as a component of identical waveform with the voltage. This approach, when extended to nonsinusoidal waveforms, supports Fryze's model for apparent power, S/sup 2/=p/sup 2/+Q/sup 2//sub F/. It is proved that the total reactive power Q/sub F/ is composed from four distinctive types of elementary reactive powers. Each of the basic reactive powers is identified as the amplitude of an oscillation of instantaneous power. The separation of Q/sub F/ in Q/sub 1/, the reactive power at the system frequency, and in Q/sub H/, the reactive power at harmonic frequencies, is recommended as an effective mean for monitoring filter efficacy and power-factor compensation. Two major recommendations are supported by the results of this study: abolish the power model using distortion power, and measure the active power of the system frequency separately from the active power of the harmonics. >

265 citations


Journal ArticleDOI
TL;DR: A knowledge-based expert system was developed for the short-term load forecasting of the Taiwan power system and it is found that a mean absolute error of 2.52% for one year is achieved by the expert system approach as compared to an error of 3.86% by the statistical method.
Abstract: A knowledge-based expert system was developed for the short-term load forecasting of the Taiwan power system. The developed expert system, which was implemented on a personal computer, was written in PROLOG using a 5-year database. To benefit from the expert knowledge and experience of the system operator, eleven different shapes, each with different means of load calculations, were established. With these load shapes at hand, some peculiar load characteristics pertaining to the Taiwan Power Company can be taken into account. The special load types considered by the expert system include the extremely low load levels during the week of the Chinese New Year, the special load characteristics of the days following a tropical storm or a typhoon, the partial shutdown of certain factories on Saturdays, the special event caused by a holiday on Friday or on Tuesday, etc. A characteristic feature of the knowledge-based expert system is that it is easy to add new information and new rules to the knowledge base. To illustrate the effectiveness of the system, short-term load forecasting is performed on the Taiwan power system by using both the developed algorithm and the conventional Box-Jenkins statistical method. It is found that a mean absolute error of 2.52% for one year is achieved by the expert system approach as compared to an error of 3.86% by the statistical method. >

251 citations


Book
14 Dec 1990
TL;DR: This book describes the main computer modelling techniques that constitute the framework of modern power system analysis and covers load or power flow, AC system faults, and the electromechanical behavior of power systems.
Abstract: This book describes the main computer modelling techniques that constitute the framework of modern power system analysis. After describing the main computational and transmission system developments influencing power system analysis, the book covers load or power flow, AC system faults, and the electromechanical behavior of power systems. Dynamic models of power system plants and their use in multi-machine transient stability analysis are discussed, and chapters also cover the electromagnetic transients program, harmonic flow analysis, and power system security and optimization analysis. Recent advances in interactive power system analysis and developments in computer graphics are also presented.

232 citations


Journal ArticleDOI
TL;DR: An active power filter using quad-series voltage-source pulsewidth-modulated (PWM) converters to suppress AC harmonics by injecting compensating currents into the AC system is described in this article.
Abstract: An active power filter using quad-series voltage-source pulse-width-modulated (PWM) converters to suppress AC harmonics by injecting compensating currents into the AC system is described. The circuit used to calculate the compensating current references, the compensation characteristics, and the capability of the DC capacitor are discussed theoretically and experimentally. A control circuit for the DC capacitor voltage is proposed. The discussions focus on transient states, based on the instantaneous reactive power theory. A passive LC filter is designed to remove the switching voltage and current ripples caused by the PWM converters at the AC side. Some experimental results that illustrate the details of the study are shown. >

228 citations


01 Aug 1990
TL;DR: In this paper, the authors investigated the possibility of using high speed thyristor based control of HVAC power system elements to enhance the carrying capacity of existing transmission circuits without compromising reliability.
Abstract: This is the first of two scoping studies of the Flexible ac Transmission System (FACTS). It investigates the possibility of using high speed thyristor based control of HVAC power system elements to enhance the carrying capacity of existing transmission circuits without compromising reliability. A study system representative of existing power systems were developed. The studies were conducted on this system to evaluate the economic and technical issues of loading transmission lines to their thermal limits. Two scenarios were considered, a multi-line corridor and a long radial interconnection. The issues addressed were transient and dynamic stability, loop flow control, power flow control, reactive support and voltage stability. 4 refs., 29 figs., 11 tabs.

213 citations


Journal ArticleDOI
TL;DR: In this paper, a new method for determining the voltage stability condition in a power system is presented, based on sensitivity techniques, taking into account the limits on reactive power generation capacities.
Abstract: A new method for determining the voltage stability condition in a power system is presented. The method is based on sensitivity techniques, taking into account the limits on reactive power generation capacities. A distance to voltage collapse in terms of MVAr is defined as a measure of system security. Results from calculations on a 480-bus network with 140 generators are presented. The method can be efficiently used for reactive power security evaluation in both system planning and operation. >

Journal ArticleDOI
P. Kundur1, G.J. Rogers1, D.Y. Wong1, L. Wang1, M.G. Lauby 
TL;DR: A package of integrated programs for small-signal stability analysis of large interconnected power systems is described, which has extensive modeling capability and uses alternative eigenvalue calculation techniques, making it suitable for the analysis of a wide range of stability and control problems.
Abstract: A package of integrated programs for small-signal stability analysis of large interconnected power systems is described. The package has extensive modeling capability and uses alternative eigenvalue calculation techniques, making it suitable for the analysis of a wide range of stability and control problems. Results of eigenvalue calculations for three power systems of differing size and complexity are presented and the accuracy, consistency and convergence of the alternative calculation methods are discussed. >

Journal ArticleDOI
G.A. Maria1, C. K. Tang1, J. Kim1
TL;DR: In this article, a hybrid method of power system transient stability analysis, which combines the desirable features of both the time-domain simulation technique and the direct method of transient analysis, is presented.
Abstract: The hybrid method of power system transient stability analysis, which combines the desirable features of both the time-domain simulation technique and the direct method of transient stability analysis, is presented. The hybrid method first computes the actual system trajectory using time-domain simulation, then evaluates the transient energy function in order to derive a stability index for fast derivation of transient stability limits. Proper criteria are proposed to stop the time-domain simulation of the system trajectory to reduce CPU time, once the status of the system has been identified. The method was successfully applied to three test systems varying in size from four generators to 50 generators. The method is shown to be a potential tool for online calculation of transient stability limits. >

Journal ArticleDOI
TL;DR: In this paper, it is shown that a load flow solution with feasible voltage magnitude for radial distribution networks always exists and is unique and demonstrated that different patterns of load demand require different power supply from the substation.
Abstract: On the basis of voltage level, an electric power system can be viewed as consisting of a generation system, a transmission system, and a distribution system. The steady-state operation of a power system requires that the power supply, transmission losses, and load demand be balanced, as described by the load flow equations. The configuration of a transmission network is that of a loop while the configuration of a distributed network is radial. It is well recognized that the number of load flow solutions for transmission networks, if they exist, are multiple. In contrast, it is shown here that a load flow solution with feasible voltage magnitude for radial distribution networks always exists and is unique. These results demonstrate the weak ability of radial distribution networks to meet load demands in the sense that different patterns of load demand require different power supply from the substation. >

Journal ArticleDOI
TL;DR: The security measure captures nonlinear effects such as VAR limits on generators that can influence the systems vulnerability to collapse and the behavior of the index with respect to network load increases is nearly linear over a wide range of load variation, facilitating prediction of the onset of collapse.
Abstract: A security measure is defined to indicate vulnerability to voltage collapse based on an energy function for system models that includes voltage variation and reactive loads. The system dynamic model, the energy function, and the security measure are first illustrated in a simple radial system. Application of the security measure and its computational aspects are then examined in a standard 30-bus example (New England System). The security measure captures nonlinear effects such as VAR limits on generators that can influence the systems vulnerability to collapse. The behavior of the index with respect to network load increases is nearly linear over a wide range of load variation, facilitating prediction of the onset of collapse. >

Journal ArticleDOI
01 Jul 1990
TL;DR: The authors present a new method for obtaining the PLF solution, by combining Monte Carlo simulation techniques and linearised power flow equations for different system load levels, through the IEEE 14-busbar test system and through its application in part of the Brazilian network.
Abstract: Load flow analysis is undoubtedly the most useful method of designing and operating power systems. The input data necessary for these studies are best described by random variables, considering the probabilistic nature of loads, generation and networks. The effects of uncertainties on the steady-state behaviour of power systems can be evaluated by a stochastic or probabilistic load flow (PLF) analysis. The authors present a new method for obtaining the PLF solution, by combining Monte Carlo simulation techniques and linearised power flow equations for different system load levels. The performance of the proposed algorithm is illustrated through the IEEE 14-busbar test system, and also through its application in part of the Brazilian network. >

Journal ArticleDOI
TL;DR: An application of the probabilistic load flow techniques to the expansion planning of power systems is presented and special emphasis is given to short-term and long-term modeling using analyses of real system load data.
Abstract: An application of the probabilistic load flow (PLF) techniques to the expansion planning of power systems is presented. A brief review of the PLF formulation and solution is included to identify differences between this technique and other available tools such as composite generation and transmission reliability evaluation algorithms. The potential of the PLF technique is demonstrated by a case study using the Brazilian North/Northeastern system. The network expansion planning of an area of this system is studied using a conventional load flow program and the results are compared with those obtained from a PLF program that models generation capacity unavailabilities and peak load uncertainties. The significant differences demonstrate the benefits of the PLF technique. Special emphasis is given to short-term and long-term modeling using analyses of real system load data. >

Journal ArticleDOI
TL;DR: In this paper, the effect of small-sized magnetic energy storage (MES) units (both superconducting and normal loss types) on load-frequency dynamics of large power areas is investigated.
Abstract: Fast-acting energy storage devices can effectively damp electromechanical oscillations in a power system because they provide storage capacity in addition to the kinetic energy of the generator rotor, which can share the sudden changes in power requirement. The effectiveness of small-sized magnetic energy storage (MES) units (both superconducting and normal loss types) for this application is shown, and means of best utilizing the small energy storage capacity of such units to improve the load-frequency dynamics of large power areas are suggested. The proposed method of improving the load frequency control of power systems has the advantage that it does not require the governor or any other part of the power system to perform any sophisticated control action. The control logic suggested for this purpose takes the area control error as its input and uses inductor current deviation feedback. In a power system with a SMES (superconducting MES) unit, the optimal setting of the integrator gain is altered to a higher value. With the suggested control measure, SMES units of 4-6 MJ capacity would suffice in reducing the maximum deviations of frequency and tie-line power flow by about 40% in power areas of 1000-2000 MW capacity. >


Journal ArticleDOI
TL;DR: In this article, a general package for harmonic-domain computation is described, consisting of a set of routines which can be used by developers of programs for power system harmonic applications, and the most basic routines have been listed.
Abstract: A general package for harmonic-domain computation is described. It consists of a set of routines which can be used by developers of programs for power system harmonic applications. The most basic routines have been listed. The package represents nonlinear characteristics by fitting the characteristic with a polynomial, for which special harmonic domain processing via convolutions has been developed, or by directly applying a fast Fourier transform. A model in the form of a differential equation is derived for the electric arc. It is based on simple energy balance considerations and therefore is expected to be generally valid. The computational results compare well with existing measurements. The arc model can be used for discharge lamps or for arc furnaces. >

Journal ArticleDOI
TL;DR: In this article, a method for the simulation of the composite power system is proposed for the purpose of evaluating the probability distribution function of circuit flows and bus voltage magnitudes, which consists of two steps.
Abstract: A method for the simulation of the composite power system is proposed for the purpose of evaluating the probability distribution function of circuit flows and bus voltage magnitudes. The method consists of two steps. First, given the probabilistic electric load model, the probability distribution function of the total generation of generation buses is computed. Second, circuit flows and bus voltage magnitudes are expressed as linear combinations of power injections at generation buses. This relationship allows the computation of the distribution functions of circuit flows and bus voltage magnitudes. The method incorporates major operating practices such as economic dispatch and nonlinearities resulting from the power flow equations. Validation of the method is performed via Monte Carlo simulation. Typical results are presented, showing that the proposed method matches the results obtained with the Monte Carlo simulations very well. Potential applications of the proposed method are: composite power system reliability analysis and transmission loss evaluation. >

Patent
27 Sep 1990
TL;DR: In this article, a rectifier bridge consisting of rectifying devices (24, 25) connected to an AC source and providing a DC output to DC bus lines was proposed. But the authors did not consider the use of an external DC power source such as a battery.
Abstract: Power conversion apparatus for AC to DC to AC power conversion includes a rectifier bridge formed of rectifying devices (24,25) connected to an AC source (21) and providing a DC output to DC bus lines (27,28). A full bridge of active switching devices (30, 31, 34, 35) is connected across the DC bus lines to which a power source such as a battery (39) may also be connected. The load (36) and the AC power supply (21) share a common neutral line (33). The output of the bridge can provide AC output power to the load through a transformer (74). The power conversion apparatus allows full control of the currents on the load lines and AC input lines, even when the input and output are asynchronous. By providing an external DC power source such as a battery (39), uninterrupted power can be supplied to the load when the AC power source fails.

Journal ArticleDOI
TL;DR: The WR (waveform relaxation) algorithm is extended to a structure-preserving power system model in which the loads are retained, resulting in a system of differential/algebraic equations (DAEs) which enable power systems to obtain more favorable results than were obtained in VLSI simulations.
Abstract: The WR (waveform relaxation) algorithm is extended to a structure-preserving power system model in which the loads are retained. This results in a system of differential/algebraic equations (DAEs). Power system exhibit several unique dynamic properties which may be exploited in an advantageous manner by the WR algorithm. These physical properties include the coherency properties of the power system which lead to the partitions for the textured model approach, the near diagonal dominance which leads to longer windows for uniform convergence, and the localized response from which the multirate capabilities of the WR method can be used. These characteristics enable power systems to obtain more favorable results than were obtained in VLSI simulations. The authors present several theoretical results as well as computational results on parallel implementation. >

Journal ArticleDOI
TL;DR: In this paper, a rule-based stabilizing control scheme is proposed to improve the overall stability of electric power systems, where several simple rules are prepared for each generator in the system.
Abstract: An application of the rule-based stabilizing control scheme to improve the overall stability of electric power systems is presented. Several simple rules are prepared for each generator in the system. The stabilizing signal for each generator is of the discrete type; it is renewed at every sampling time to control the generator excitation levels depending on the speed/acceleration state of the generator, using the measured speed deviation and the control rules. The efficiency of the proposed rule-based stabilizer is demonstrated by using a sample three-machine power system. >

Journal ArticleDOI
TL;DR: In this article, a method of analysis is presented and applied to a model system which is well established and extensively used in studies of HVDC converters connected to weak AC systems.
Abstract: A method of analysis is presented and applied to a model system which is well established and extensively used in studies of HVDC converters connected to weak AC systems. The method is based on fundamental frequency quantities. A variety of phenomena and interactions of the AC/DC system can be analyzed, and basic understanding of the mechanisms can be gained. Some important properties of the system, such as voltage/power stability in different control modes and stability of tap changer action, are analyzed. Furthermore, they dynamics of a system consisting of a static VAr compensator (SVC) and DC converters are analyzed, and the requirements for stable operation are derived within the framework of the method of analysis presented. These results are verified by time simulation done by a transient stability program. >

Proceedings ArticleDOI
05 Dec 1990
TL;DR: The use of real-time phasor measurements for voltage stability analysis of power systems is considered and an algorithm which achieves this goal has been developed and tested on several power systems of various sizes and structures.
Abstract: The use of real-time phasor measurements for voltage stability analysis of power systems is considered. Two schemes of phasor measurement unit (PMU) placement have been investigated. In the first scheme, PMUs are used as pilot points for the secondary voltage control of a power system. Several criteria for pilot point selections are reviewed and assessed. In the second scheme, the PMUs are used for the purpose of estimating the whole state of the system. This is a prerequisite for the determination of the voltage stability margins. The goal is to find the minimal set of PMUs that makes the system both linear and observable. By making use of the simulated annealing method, an algorithm which achieves this goal has been developed and tested on several power systems of various sizes and structures. >

Book
01 Feb 1990
TL;DR: In this paper, the analysis of AC and DC circuits is presented. But the authors do not discuss the relationship between the two types of circuits and the physical basis of electromagnetism.
Abstract: I. CIRCUITS. 1. Basic Circuit Theory. 2. The Analysis of DC Circuits. 3. The Dynamics of Circuits. 4. The Analysis of AC Circuits. 5. Power in AC Circuits. 6. Electric Power Systems. II. ELECTRONICS. 7. Semiconductor Devices and Circuits. 8. Digital Electronics. 9. Analog Electronics. III. SYSTEMS 10. Instrumentation Systems. 11. Communication Systems. 12. Linear Systems. IV. MOTORS. 13. The Physical Basis of Electromagnetics. 14. Magnetic Structures and Electrical Transformers. 15. The Synchronous Machine. 16. Induction Motors. 17. Direct-Current Motors. 18. Power Electronic Systems. Index.

Journal ArticleDOI
TL;DR: An adaptive excitation controller for a synchronous generator based on the linear optimal control theory is proposed, which exhibits better performances than an automatic voltage regulator (AVR) with a conventional power system stabilizer (PSS).
Abstract: An adaptive excitation controller for a synchronous generator based on the linear optimal control theory is proposed. The generator operating conditions are tracked by a model whose parameters are identified every sampling interval using the actual input and output of the generator. The control is computed by solving a third-order Riccati equation and the identified model parameters. Studies on a single-machine infinite-bus system and a three-machine infinite-bus system show that the proposed controller exhibits better performances than an automatic voltage regulator (AVR) with a conventional power system stabilizer (PSS). >

Journal ArticleDOI
TL;DR: In this article, the authors present a method and the mathematical formulation for large-scale optimal power flow sensitivity analysis, which has been implemented in a computer program (OPSENS) presently in use in the Pacific Gas and Electric Company.
Abstract: The authors present a method and the mathematical formulation for large-scale optimal power flow sensitivity analysis. The method has been implemented in a computer program (OPSENS) presently in use in the Pacific Gas and Electric Company. The results of using the OPSENS program for calculating the sensitivity of system losses for a 34 bus and a 1700 bus transmission network to bus load changes are reported and compared to the results of multiple OPF (optimal power flow) studies. The effectiveness of OPSENS in this application was demonstrated. >

Journal ArticleDOI
TL;DR: In this paper, an integrated methodology for long-term VAr planning is presented that results in determining the timing (year), the location, and the amount of VAr compensation.
Abstract: An integrated methodology for long-term VAr planning is presented that results in determining the timing (year), the location, and the amount of VAr compensation. The system security and investment and operating economics are taken into account. The proposed methodology is an integration of the Newton-OPF with the generalized Benders decomposition (GBD). The total problem is decomposed into two levels: master and slave. The master level deals with the investment decision of installing discretized new VAr devices. The slave level deals with operating the existing controllers, in conjunction with the new devices solved in the master level, to maintain system feasibility and to reduce MW losses. The overall solution methodology contains numerous extensions to the basic theory. Tests performed on actual Taiwan power system data have been encouraging. Sample results are presented. >