Showing papers on "Power system simulation published in 1970"

Composite Representation of a Multireservoir Hydroelectric Power System

Abstract: A composite model for multireservoir hydroelectric power systems is constructed for studying the monthly decision conceming total hydrogeneration. This is an important decision when the inflows are uncertain and when hydro, with zero marginal cost, can be used not only to satisfy firm load commitments but also to displace other firm resources or to serve secondary loads. In such a case, the tradeoff between savings at the present and expected benefits in the future is determined mainly by the total hydrogeneration. The construction of a composite representation for the multireservoir hydroelectric power system in the Pacific Northwest is described. The composite model is based on a single measure "potential energy" which is indicative of the system's generating capability. This results in a one-dam representation of the multireservoir system which, in effect, receives, stores, and releases potential energy, in a statistical model for the potential energy inflow and in a generation function which relates potential energy released to actual electric power generated. It has applications in the study of different operating policies, market structures, and investment programs through simulation or optimization. As an example, it is used to obtain the net operating revenues as a function of the excess thermal in the system.

A Mathematical Optimization Technique for the Expansion of Electric Power Transmission Systems

Abstract: Planning the expansion of a high-voltage transmission system involves deciding which new lines will enable the system to satisfy forthcoming loads with the required degree of reliability. Since these decisions involve considerable investment and operating costs, the planner will wish to keep the present worth of all costs as low as possible. The difficulties of the problem come from the tremendous number of possible alternatives, the need to make the best use of information about future loads, and the complexity of the reliability constraints: The outages of some specific combinations of lines (highest capacity lines among them, perhaps) must not at any time overload any other line in the system. A new computational procedure for system planning is presented; this procedure combines and optimizes the formerly separate computations of load flow, reliability analysis, and economic evaluation. This procedure has been applied successfully to a 17-node system studied by the Bonneville Power Administration.

Simulation of AC System Impedance in HVDC System Studies

Abstract: In some studies of HVDC system design, ac system impedance is represented by its inductance at power frequency. However, for several studies better simulation of the impedance- frequency characteristic (from power frequency to a few kilohertz) of the ac system is important. This paper presents a simple approach to calculating an approximate equivalent network consisting of parallel LCR branches and having an impedance-frequency characteristic similar to that given for the ac system. For given typical ac system impedance diagrams (usually obtained from ac system models and simulators), simulation of an ac system by corresponding equivalent networks during studies of certain HVDC problems would provide a more accurate means of designing HVDC systems.

Stability Analysis of a DC Power System

Abstract: A stability study of a dc power system is performed by applying Nyquist stability criterion to a mathematical model that describes the behavior of the system during small disturbances about a steady-state operating point. The operating-point stability, as predicted by this linearized model, is compared with the response of the hybrid computer simulation of the actual system. Regions of instability for various system parameters, including the impedance of the ac system and the transmission line length, are established by a digital computer study. The delay and attenuation of the transmission line as well as the action of the converters with typical controllers are accurately taken into account. The linearized model presented should be helpful in the design and development of converter control systems for two-terminal dc power systems. Moreover, this method of analysis may be readily extended to include multiterminal dc power systems.

Long-term power system expansion planning by dynamic programming and production cost simulation

Abstract: This paper extends previously published results on the application of a dynamic programming optimization approach to the planning of systems, with special emphasis on the long-term expansion of power systems. Future uncertainties about loads, equipment costs, etc. are considered explicitly in the method described. A practical computational solution to the resulting stochastic optimization is obtained by means of the recently developed open-loop feedback approximation. Further, it is shown how various known approaches of production cost simulation can be used in conjunction with the dynamic programming optimization to accommodate large systems that may be represented with great technical detail.

Evaluation and Comparison of Some Methods for Calculating Generating System Reliability

Abstract: A number of methods of calculating reliability figures of merit for generating systems exist, but to date absolute comparisons of the accuracy of the various methods do not seem to have been made. Comparisons of some of these methods are made here, using a typical power system as a test system and results from a digital computer simulation as the basis for comparison. The paper also presents a modified calculation technique that is easy to apply and whose results closely approximate results obtained by system simulation.