Showing papers on "Electric power system published in 1972"

Electric power systems

Abstract: Basic Concepts Components of a Power System Control of Power and Frequency Control of Voltage and Reactive Power Load Flows Fault Analysis Stability Limits Direct Current Transmission Overvoltages and Insulation Requirements Overhead Lines and Underground Cables Protection Appendices Index.

Power System Simulation Model Based on Probability Analysis

Abstract: The optimisation of power system operation over periods of time of the order of one or more years requires simulation models which combine reasonable accuracy with high computation speed The development of a model suitable for such studies and based on probability techniques is described

Optimal Power System Stabilization Through Excitation and/or Governor Control

Abstract: For an optimal linear regulator design a performance function of the quadratic form must be chosen. The question arises of how to decide the weighting matrix Q of the performance function. A new method is developed in this paper to determine Q in conjunction with a left shift of the dominant eigenvalues as far as the practical controllers permit. The method is then applied to the optimal control design of a typical power system. Three cases are investigated, the first with an optimal excitation control uE, the second with optimal governor controls uG and uG, with and without the dash-pot, and the third with uE plus uG control. The stabilizing signals thus obtained are given nonlinear tests on the same power system. It is found from the results that the optimal controls are more effective than conventional excitation control, that the optimal governor control without dash-pot is just as good as the optimal excitation control, and that the optimal uE plus uG control is the best way to stabilize a power system.

Linear Regulator Design for a Load and Frequency Control

Abstract: The results of a dynamic optimization procedure in the design of load and frequency control (LFC) of power systems are presented. This design is based on the optimal linear regulator theory, accommodated to satisfy the performance objectives of the LFC in large multiarea interconnections. A proportional-plus-integral control law is considered. The paper also analyzes the influence of system and design parameters on power system performance considering two-and three-area interconnections. Finally, the problems of implementation are discussed.

A simplified non-linear model of a drum boiler-turbine unit†

Abstract: In the analysis of power systems it is highly desirable to have models of the different power generators. In this paper we present, a model for a drum boiler whose purpose is to describe the gross behaviour of the boiler. The major control variables are fuel flow and control valve setting. The output variables are drum pressure and active output power. The model is verified by experiments on a 160 Mw boiler.

An optimal formulation and solution of short-range operating problems for a power system with flow constraints

Abstract: The complete problem, to minimize the operating cost of a hydrothermal generation system over one day (or one week) is formulated and solved through a few assumptions: the dc approximation and a linear law for the fuel costs, primarily the methods used mix the combinatorial and the electrical features of the problem. New methods employed are a branch and bound method for the thermal unit commitment, a gradient method to set the hydropower, and an economic dispatch routine with active flow constraints.

Advanced Load Frequency Control

Abstract: The problem of designing a load frequency control law which reduces transient frequency oscillations (swings) and reduces the number of control signals sent to power houses is investigated. A linear model of an area of an interconnected power system is developed, and a discrete time, linear-plus-deadband, feedback control law is designed. Feedback variables include cumulative inadvertent interchange, frequency deviation, integral of frequency deviation, real power absorbed by loads, and governor-turbine variables. This linear-plus-deadband control is an application of a special case of a more general "set-theoretic" class of control laws. A simulation of two areas with two hydro sources is presented. The dynamic response to a step load change is determined for the case of no load frequency control, load frequency control presently used by power companies, and load frequency control designed in this paper.

State Calculation of Power Systems from Line Flow Measurements, Part II

Abstract: Extending the theoretical foundations established in Part I(1), this paper further describes this efficient method of computing the real-time load flow solution for a power system network. An efficient numerical solution technique particularly applicable to this problem is outlined. Relative weighting of the measurements is analyzed in terms of the measurement accuracies. A method is given for dynamic determination of the frequency of the state estimate calculations. The effects of real-time changes in the network are discussed.

Optimum Load-Frequency Continuous Control with Unknown Deterministic Power Demand

Abstract: Since the incremental power demand in a power system is not always apriori known, direct application of the optimum linear- state regulator to load-frequency control is not possible Furthermore, load-frequency control generally requires the use of an integral type control operation to meet the system operating specifications This requirement is introduced into the formulation of the optimum load- frequency control problem presented in this paper

Optimal power-flow solutions for power system planning

Abstract: Since the development of sparsity techniques by Tinney, the power-flow program has become an extremely effective and often used tool for planning electric power networks. This program solves for the unknowns--voltages, phase angles, etc.--of a set of simultaneous nonlinear algebraic equations, the ac power-flow equations. The optimum power flow is likely to replace, in due time, the normal power flow in many important planning functions discussed in this paper. A number of mathematical programming techniques have recently been studied to solve the optimum power flow and several small-to-medium sized experimental programs have been written. The generalized reduced gradient (GRG), one of the most elegant nonlinear-programming techniques, is described and it is shown how it can be extended to solve optimum power flows of very high dimension (of the order of several thousand nodes). This extension consists mainly of using sparsity techniques in several of the solution steps of the GRG.

System and method for operating industrial gas turbine apparatus and gas turbine electric power plants preferably with a digital computer control system

Abstract: A gas turbine power plant is provided with an industrial gas turbine which drives a rotating brushless exciter generator coupled to a power system through a breaker. One or more of the turbine-generator plants are operated by a hybrid digital computer control system during sequenced startup, synchronizing, load, and shutdown operations. The program system for the computer and external analog circuitry operate in a multiple gas turbine control loop arrangement. Logic macro instructions are employed in programming the computer for logic operations of the control system.

System and method employing a digital computer with improved programmed operation for automatically synchronizing a gas turbine or other electric power plant generator with a power system

Abstract: A gas turbine power plant is provided with an industrial gas turbine which drives a rotating brushless exciter generator coupled to a power system through a breaker. One or more of the turbine-generator plants are operated by a hybrid digital computer control system during sequenced startup, synchronizing, load and shutdown operations. The program system for the computer and external analog circuitry operate in a multiple gas turbine control loop arrangement. Automatic synchronization is achieved with a hybrid subsystem which includes the programmed computer and external phase detection circuitry. An automatic synchronization program for the computer is divided into rough speed and voltage matching, fine speed matching and breaker closure subprograms.

Stability Analysis of Power Systems

Abstract: A procedure for locating directly the lowest saddle point of the potential energy function associated with a power transmission network is presented. This procedure is used to compute a margin of stability that specifies the maximum asynchronous transient energy that can be retained by the system while in synchronism. The potential function is shown to be convex in the principal region of the angle space. A unique solution is shown to exist for the load flow problem if the algorithm of solution is initiated at the origin.

Hybrid vehicular power system

Abstract: A hybrid drive system is provided for a vehicle whereby an internal combustion engine and an electric motor may be used to drive the vehicle; the tow motors being coupled to the drive shaft of the vehicle through a planetary gear transmission system. The planetary gear system permits full control to be achieved of the vehicular speed while the internal combustion engine is operated at constant speed, and it permits either the electric motor or the internal combustion engine, or both, to be used to drive the vehicle.

Effect of Load characteristic on the Dynamic Stability of Power Systems

Abstract: In order to include an accurate representation of loads in steady state stability investigations a method based on state space theory is suggested which due to its flexibility can be applied to any type of terminal equipment. In the present paper it is shown how the dynamical behaviour of loads may have a decisive influence on the stability limit of a power system.

Power Reliability Cost vs Worth

Abstract: Properly fitting a power system to the society it serves is an exceedingly difficult and important problem. Service reliability, a very important factor in this fit, has been determined somewhat arbitrarily in the past. Errors here are costly both to the supplier of electric power and to the power consumer. This paper presents the first method for determining economic optimum service reliability. A method for estimating ating the cost of service interruptions is proposed and the cost obtained is compared with values determined by others. A primary purpose of the paper is to provoke discussion and further research into the cost of power r interruptions and the optimizing of system design considering this cost.

Effects of Power Supply Variations on AC Motor Characteristics

Abstract: Voltage level variations are shown to be only one of eight different types of voltage deviations which can affect motor characteristics. Each of these is discussed in relation to possible detrimental effects on operating costs or motor reliability. The timeliness of the paper is demonstrated, especially for continuous process and automated industries. Remedial measures, when indicated, are shown to cover a wide gamut from redesigning control systems to reappraising the electrical system one line diagram.

System and method employing a digital computer for automatically synchronizing a gas turbine or other electric power plant generator with a power system

Abstract: A gas turbine power plant is provided with an industrial gas turbine which drives a rotating brushless exciter generator coupled to a power system through a breaker. One or more of the turbine-generator plants are operated by a hybrid digital computer control system during sequenced startup, synchronizing, load, and shutdown operations. The program system for the computer and external analog circuitry operate in a multiple gas turbine control loop arrangement. Automatic synchronization is achieved with a hybrid subsystem which includes the programmed computer and external phase detection circuitry. An automatic synchronization program for the computer is divided into rough speed and voltage matching, fine speed matching and breaker closure subprograms.

Method of controlling supply of power

Abstract: A digital computer system is employed to produce power system control. The computer system employs an economic dispatch program, a unit selection program and a tie line interchange program to determine off line a tie line schedule and unit commitments needed to satisfy economically and safely a load forecast over a selected time interval such as 24 hours. In on line closed control loop operation, the computer system employs a load and frequency control program which uses the tie line schedule and other quantities in determining area control error. The control program develops a system error representation which reflects a smoothed present and anticipated area control error. The system error representation is distributed into individual generator plant control signals under economic dispatch program and unit selection program control and under constraint of programmed plant limits to assure that each generation move is error correcting as well as optimally economic.

Dynamic Energy Balance Studies for Simulation of Power-Frequency Transients

Abstract: Dynamic energy balance is a new technique for power system dynamic simulation. It requires about one tenth the computatioanl effort of a transient stability study yet gives similar results so far as frequency transients are concerned. Applications, methodology and comparison with a transient stability study are treated in this paper.

Optimal Scheduling of Hydro-Thermal Power Systems

Abstract: The model studied is comprised of thermal and hydro plants as well as electrical and hydro networks. It incorporates such features as variable water heads and cascaded plants, taking into account time delays as well as spilling. The transmission network is described by electrical equations. The model also includes such constraints as bounds on the equipment ratings and operating conditions.

Engineering aspects of hydrazine-air fuel-cell power systems

Abstract: Over the last few years a number of fuel-cell power systems of various types and power outputs have been built by Shell Research Ltd. The first of these was a relatively primitive hydrazine-air system built in 1962. The paper will trace the development of these power systems from 1962 to the present day. Emphasis will be placed mainly on the engineering design and development that have been needed to take advantage of the improved catalysts and electrodes. Thus, the methods devised to give adequate fluid flows will be outlined, the simplification of components will be considered and the design of ancillaries will be discussed. Present-day fuel batteries have power densities of up to 130–150 W/kg (60–70 W/lb) and, even with commerically available auxiliaries, complete power systems having power/weight ratios of about 52 W/kg (24 W/lb) can be built. These figures are compared with the power densities of conventional electric generators, and future possibilities are discussed.

Space nuclear power systems

Abstract: Space nuclear power systems are considered for use in those particular spacecraft applications for which nuclear power systems offer unique advantages over solar and/or chemical space power systems. Both isotopic and reactor heated space electrical power units are described in an attempt to illustrate their operating characteristics, spacecraft integration aspects, and factory-to-end of mission operational considerations. The status of technology developments in nuclear power systems is presented. Some projections of those technologies are made to form a basis for the applications of space nuclear power systems to be expected over the next 10-15 years.

Dynamic Performance Evaluation of a Computer Controlled Electric Power System

Abstract: The paper presents the general dynamic evaluation problem of an Electric Power System under computer control. The philosophy and design techniques of a state-of-the-art digital load- frequency controller are outlined. Dynamic control criteria which will allow performance evaluation of this class of control are defined. Techniques of applying these criteria are presented, along with consideration of man-machine requirements for their evaluation. A trend recording technique suitable for performance evaluation with a control computer is described. Finally, simulation results and field test data are presented to illustrate dynamic performance evaluation of a controlled system.

Reactive power compensation control system

Abstract: A reactive power compensation control system is provided for a three phase ac electric power supply system which exhibits power factor changes when subjected to large reactive draws by dynamic reactive loads. The control system comprises four capacitor banks switchable in or out of the power system by solid state switches. Each capacitor bank comprises three delta connectible capacitors, one capacitor for each pair of phase lines, and each capacitor is switched by one solid state switch. Each solid state switch comprises a pair of inverse parallel connected SCR''s. Each solid state switch is controlled by an individual firing circuit which comprises a charging circuit (for operating the charging SCR) and a discharging circuit (for operating the discharging SCR). All 12 firing circuits are controlled by a control circuit which comprises a KVAR transducer coupled to the power supply system for sensing reactive power conditions therein and ON and RUN circuits which operate the firing circuits.

Quantitative Evaluation of Power System Reliability In Planning Studies

Abstract: In considering the problem of quantitative evaluation of the reliability of a power system for planning purposes, the authors show the advisability of making use of a couple of risk indices in terms of curtailed energy and abruptly disconnected power.

Circuit breaker monitor for uninterruptable power systems including a static bypass

Abstract: An uninterruptable power system including main apparatus for supplying power to a critical bus, the main apparatus includes electromechanical circuit breakers and a static switch. Bypass apparatus is also provided including a static switch to supply power to the critical bus in high-speed response to the actuation of the circuit breaker trip initiating means.

Simplifications for Area Security Analysis: A New Look at Equivalence

Abstract: Analysis of an area within a large interconnected power system under various system configurations and load conditions is often needed in off-and on-line applications. Equivalence isolates the study area and represents the rest of the system by a simplified equivalent model. A new and more comprehensive approach to the equivalence problem is presented which emphasizes the design and operational aspects rather than conventional network reduction, and which is based on meeting application-specified operational requirements. Results from a test case demonstrate the validity and accuracy of the method as applied to outage analysis load flow studies.