Showing papers on "Power-flow study published in 1972"
TL;DR: The development of a model suitable for power system operation over periods of time of the order of one or more years and based on probability techniques is described.
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
311 citations
TL;DR: In this article, the results of a dynamic optimization procedure in the design of load and frequency control (LFC) of power systems are presented, based on the optimal linear regulator theory, accommodated to satisfy the performance objectives of the LFC in large multi-area interconnections.
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.
153 citations
TL;DR: In this article, the authors defined a dimensionless stability margin which lies between one and zero (steady state in- stability) and is easily computed from a load flow, where the margin of torque is defined as the least change in power flows that will cause instability.
Abstract: The flow function of a power system is the vector of node powers expressed in terms of the node angles The Jacobian is the matrix of partial derivatives of the flow vector with respect to the angle vector The ratio of the determinant of the Jacobian to the value which it has when the node angles are set to zero is a dimensionless stability margin which lies between one and zero (steady-state in- stability) and is easily computed from a load flow The margin of torque is the least change in power flows that will cause instability Maximizing the torque margin or maximizing the stability margin with a load constraint yields the optimum dispatching change to maximize security
106 citations
01 Jan 1972
TL;DR: 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.
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.
98 citations
TL;DR: In this paper, the center of angle is defined as the inertia weighted average of all rotor angles and the angular velocity of the centre of angle accurately describes the frequency of the system.
Abstract: The evaluation of the stability of a power system during a transient requires that the dynamics of the subsystems be decomposed into relative and collective motions. This decomposition must establish a distinction between synchronous and frequency equilibria. Such a decomposition is made possible by specifying a system center of angle which is defined as the inertia weighted average of all rotor angles. The angular velocity of the center of angle accurately describes the frequency of the system. An angular coordinate of each rotating element in the system can be specified relative to the center of angle. In terms of these coordinates a simple expression is obtained for the exact transient kinetic energy of the system. A transformation relating center of angle referenced variables to the usual one machine reference allows the simultaneous use of both references each where best suited.
84 citations
TL;DR: In this article, the optimal linear state regulator for load-frequency control is proposed for a power system, where the incremental power demand in the power system is not always apriori known, and direct application of the optimum linear-state regulator to load frequency control is not possible.
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
66 citations
TL;DR: In this paper, a procedure for locating directly the lowest saddle point of the potential energy function associated with a power transmission network is presented, which 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.
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.
61 citations
61 citations
TL;DR: In this article, it is shown how the dynamical behaviour of loads may have a decisive influence on the stability limit of a power system, and a method based on state space theory is suggested to include an accurate representation of loads in steady state stability investigations.
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.
55 citations
TL;DR: A new method of power flow optimization is developed which exploits this decoupling and consequently reduces problem size and has considerable potential for real time applications such as voltage control, economic dispatch, security analysis, etc., where in many situations the solution of only one subproblem will be required.
Abstract: Guided by the experience that real power is most sensitive to nodal phase angles and reactive power to voltage magnitudes, a new method of power flow optimization is developed which exploits this decoupling and consequently reduces problem size. This decomposition of the real and reactive equations results in the formation of two subproblems-one corresponding to the real power equations and the other to the reactive power equations. In practice, the two subproblems are alternatively solved until the desired accuracy is attained. The method has considerable potential for real time applications such as voltage control, economic dispatch, security analysis, etc., where in many situations the solution of only one subproblem will be required. The algorithm was originally developed for applications related to system security and for this purpose linear programming is used for optimizing each of the subproblems. A test case study of a 38-node network demonstrates the convergence properties of the algorithm.
47 citations
TL;DR: The present paper presents the basic concepts and applications of the probability method for the "on-line" assessment of the near-term future security of an operating bulk power system.
Abstract: The paper is the first of a series describing a probability method for the "on-line" assessment of the near-term future security of an operating bulk power system. The present paper presents the basic concepts and applications of the method; future papers will describe probability models for implementing the method.
TL;DR: Dynamic energy balance is a new technique for power system dynamic simulation as discussed by the authors, which requires about one tenth the computatioanl effort of a transient stability study yet gives similar results so far as frequency transients are concerned.
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.
TL;DR: In this article, a direct method is introduced for minimizing the shift of generation required to meet temporary operating criteria, such as the elimination of overload lines or transformers, or fixed flows on inter-ties or critical lines.
Abstract: A direct method is introduced for minimizing the shift of generation required to meet temporary operating criteria, such as the elimination of overload lines or transformers, or fixed flows on inter-ties or critical lines. Also, a linear model for multiple contingencies is presented.
Enel1
TL;DR: In this article, the authors show the advisability of making use of a couple of risk indices in terms of curtailed energy and abruptly disconnected power in considering the reliability of a power system.
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.
TL;DR: In this article, a new 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.
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.
TL;DR: In this article, a technique is described that permits the determination of the amount of power which can be imported from (or exported to) neighboring companies, without overloading "limiting" lines during an emergency situation, when certain "key" lines are out of service.
Abstract: A technique is described that permits the determination of the amount of power which can be imported from (or exported to) neighboring companies, without overloading "limiting" lines during an emergency situation, when certain "key" lines are out of service. The method is a multiple contingency extention of a technique described earlier.[1] The advantage of the method is the reduction in computer running time, as compared to the time required to obtain the equivalent information by complete power flow solutions, for the several conditions to be studied. The program has been extensively used with good success.[2]
TL;DR: In this article, the fundamental principles of applying probability calculations to the analysis of generating capacity reserve requirements for two or more interconnected power systems were developed, and the effect of emergency support interaction between interconnected, but otherwise independent systems was analyzed.
Abstract: This paper developes the fundamental principles of applying probability calculations to the analysis of generating-capacity reserve requirements for two or more interconnected power systems. Building on concepts developed for a single power system, the authors analyze the effect of emergency support interaction between interconnected, but otherwise independent systems.
TL;DR: In this article, the authors considered the non-linear programming problem of short-term optimal operation in a mixed hydro-thermal power system in terms of real, reactive and real and reactive power optimization.
Abstract: The non-linear programming problem of short term optimal operation in a mixed hydro-thermal power system is considered in this paper in terms of real, reactive and real and reactive power optimization. The concepts developed for each of these three cases are illustrated by application to a reduced model of the Saskatchewan Power Corporation System. The results clearly show the benefits associated with real and reactive power optimization in a system of this type.
TL;DR: The primary message of this paper is to show how this control system, scheduled to be in service in late 1972, is planned to improve the security of the power system through the implementation of several innovations in the areas of security analysis, trouble analysis, automatic circuit restoration, generalized operation load flow, interconnection modelling, and operator training.
Abstract: This paper describes the functions to be performed by a new control system designed for the operation of the generation- transmission system of the Cleveland Electric Illuminating Company. The primary message of this paper is to show how this control system, scheduled to be in service in late 1972, is planned to improve the security of the power system through the implementation of several innovations in the areas of security analysis, trouble analysis, automatic circuit restoration, generalized operation load flow, interconnection modelling, exact economic dispatch, man-machine interfaces and display, and operator training.
TL;DR: In this article, the feasibility of rapid a- stability analysis of electric power systems containing as many as 60 generators by using Liapunov functions was explored, some for the first time.
Abstract: This paper explores the feasibility of rapid a- stability analysis of electric power systems containing as many as 60 generators by using Liapunov functions. Many Liapunov functions, approximate integrals, and critical value equations are presented, some for the first time. The results of applying these functions with the aid of a CDC 6600 digital computer to electric ric power systems whose number of generators is 4, 10, 20, or 60 are given for both the computation time and result accuracy. Recommendations are made for additional research on the development of more accurate ate functions for el'ectric power system analysis.
TL;DR: The present paper presents the development of probability models for normally- operating components needed for implementation of the probabilistic security assessment method for operating bulk power systems.
Abstract: The paper continues the discussion of a probability method for the "on-line" assessment of the near-term future security of an operating bulk power system begun in Reference [1]. The present paper presents the development of probability models for normally- operating components needed for implementation of the probabilistic security assessment method.
IBM1
TL;DR: A step in this direction of an interactive load flow program (ILF) is presented, which could serve a number of important uses in the power industry.
Abstract: An interactive load flow program (ILF) differs from a conventional load flow program in its interface with the user. By means of a display device the user specifies his input and the program presents its output. Such a program could serve a number of important uses in the power industry. A step in this direction is presented in this paper.
TL;DR: This paper presents the impedance and admittance forms of diakoptic solution of the load-flow problem on the basis of graph- theoretic concepts that does not assume a fixed slack bus voltage but takes into account the equation for total transmission line losses as an integral part of the scheme.
Abstract: This paper presents the impedance and admittance forms of diakoptic solution of the load-flow problem on the basis of graph- theoretic concepts. The formulation does not assume a fixed slack bus voltage but instead takes into account the equation for total transmission line losses as an integral part of the scheme. Finally, test data based on this alternative formulation are presented for purposes of comparison With existing methods.
TL;DR: The utilization of EHV networks and underground cables in today's modern power system has created a reactive power control problem as discussed by the authors, in particular, system generators are being forced to absorb large quantities of reactive power to maintain system voltage.
Abstract: The utilization of EHV networks and underground cables in today's modern power system has created a reactive power control problem. In particular, system generators are being forced to absorb large quantities of reactive power to maintain system voltage.
TL;DR: This paper presents a general, systematic formulation of the problem of dynamic analysis of multi-machine power systems for digital simulation using a generalized machine model which enables one to consider the affect of network response in more detail than described in the literature.
Abstract: This paper presents a general, systematic formulation of the problem of dynamic analysis of multi-machine power systems for digital simulation. The analysis utilizes a generalized machine model which enables one to consider the affect of network response in more detail than described in the literature. The techniques of solution are discussed in order to indicate the structure of numerical computation.
TL;DR: In this article, the analysis of power system faults including the simultaneous ones has been undertaken with the help of phase coordinates, i.e., the actual system phase voltages, currents and impedances.
Abstract: The analysis of unbalanced power systems depends usually on transformation methods by which the phase quantities are substituted by, for example, symmetrical component quantities. These transformations had the computational advantages in the past, but with the use of digital computer, they no longer appear to be necessary. In this paper the analysis of power system faults including the simultaneous ones has been undertaken with the help of phase coordinates, i. e., the actual system phase voltages, currents and impedances. This approach is found to be simple and readily adaptable to digital computer techniques. Symmetrical components are, however, used as a measure of the system unbalance.
TL;DR: In this paper, an analysis of simultaneous unbalances and transient recovery voltages of a power system has been undertaken, which requires only the assembly of the nodal admittance or impedance matrices and subsequent solution of sets of linear algebraic equations subjected to constraints.
Abstract: Analysis of simultaneous unbalances and transient recovery voltages of power system has been undertaken in this paper. The approach is similar to the one developed in Part I of this paper. The method requires only the assembly of the nodal admittance or impedance matrices of various elements of a power system and subsequent solution of sets of linear algebraic equations subjected to constraints. The transient analysis of a power system having untransposed transmission lines can be carried out by the application of modified Foruier transform and the steady state theory of natural modes. Finally a digital computer can be programmed to calculate the magnitudes of the fault currents and active recovery voltages.
TL;DR: In this article, a method for finding time-optimal (or suboptimal) excitation control for power system stability is presented, where the control is found directly as a function of the states of the system, which can be measured.
Abstract: A method is presented for finding time-optimal (or suboptimal) excitation control for power system stability. The control is found directly as a function of the states of the system, which can be measured. A closed-loop control is found for the linearized system first, then the method is extended to the nonlinear model. The results obtained for the single-machine infinite bus problem are compared with those obtained by a steepest descent method. For small disturbances where linearity holds, the closed-loop scheme gives optimal solutions, while, for large disturbances, it yields a sub-optimal solution.