The new formulation of the load-flow problem presented in this thesis yields a set of equations each of which has only one nonlinear term. The equations are derived from the corrections required to make the final values equal to the initial estimated values. The resultant set of equations can be used when the initial estimated values are adjusted to their final values. However, derivation of the equations for this latter case results in a set of equations with (n-1) nonlinear terms in each equation for an n-bus power system. Five algorithms based upon the new formulation are described. Numerical tests on several sample power systems show that some of the new algorithms possess better convergence and speed characteristics than the commonly used Ward-Hale and Newton algorithms. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The effect of local motor loads on power system stability is investigated. The power system consists of a synchronous generator supplying a large system through a long transmission line. The loads studied are an induction motor, a synchronous motor, and the combination of the two, although a general case of any number of local induction and synchronous motor leads can be easily formulated. Stability is determined by observing the response of the generator and the motors of the system with a fault at the transmission line. The response is calculated from the mathematical model and is- also observed from tests on a dynamic power system model in the laboratory. It is found from the studies that all the local motor loads improve the stability of a power system. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

In this dissertation, the problem of multi-area load frequency control in large power systems is investigated. The load frequency control problem is concerned with the minimization of the deviations in the frequencies of the different areas and in the tie line power exchange between these areas, and is a problem of major importance in the satisfactory operation of large power systems. Some new techniques for designing load frequency control systems are presented through the use of concepts from singular perturbation and hierarchical system theory. To provide appropriate vehicles for the design of the new control systems, state variable models for power systems are developed. These models progress from a two-area interconnected power system model to large scale models comprising of N areas. Two centralized state feedback schemes are proposed for the load frequency control by utilizing the separation of the system models into two time scales. In the first scheme, composite controls and reduced order controls are developed to meet the required performance specifications by. The second scheme is obtained by using the theory of variable structure systems where the existence of a sliding regime leads to the design of a single discontinuous state feedback controller that meets the performance requirements. In order to further improve the performance of the closed loop system, a two level hierarchical control scheme is developed. This consists of a set of local controllers that are designed using either the singular perturbation approach or the variable structure system approach as before and a set of global control functions provided by a higher level controller that attempts to coordinate the local controllers. The interaction prediction principle is used as a tool in the design of the global controller. The performance of the presently developed control schemes is examined in detail for the illustrative cases of a two-area and a three-area power system. From this analysis, it is shown that these controllers provide an improved performance compared to the existing control schemes in reducing the frequency and tie line power deviations.

Digitized by Kansas Correctional Industries

A newly-developed technique for short-term load forecasting is generalized. The algorithm combines features from knowledge-based and statistical techniques. The technique is based on a generalized model for the weather-load relationship, which makes it site independent. Weather variables are investigated, and their relative effect on the load is reported. That effect is modeled via a set of parameters and rules that constitute the rule based technique. This technique is very close to the intuitive judgmental approach an operator would use to make his guess of the load. That is why it provides a systematic way for operator intervention if necessary. This property makes the technique especially suitable for application in conjunction with demand side management (DSM) programs. Moreover, the algorithm uses pairwise comparison to quantify the categorical variables, and then utilizes regression to obtain the least-square estimation of the load. Because it uses the pairwise comparison technique, it is fairly robust. Since the forecast does not depend on any preset model, the technique is inherently updatable. A generalized version of the technique has been tested using data from four different sites in Virginia, Massachusetts, Florida and Washington. The average absolute weekday forecast errors range from 1.30% to 3.10% over all four seasons in a year. Error distributions show that the errors are 5% or less around 91 % of the time. / Master of Science

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / Ph.D.

Thesis. 1978. Nucl.E.--Massachusetts Institute of Technology. Dept. of Nuclear Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Gilberto Gomes De Andrade. / Nucl.E.

No description available.

Paper given at MIT conference entitled Energy: Demand, Conservation and Institutional Problems, February 12-15, 1973

M. Phil. / Presently, ESKOM is rated as the fifth largest utility in the world that generates and distributes electricity power to their consumers at the lowest price per kilowatt-hour (kW.h). As a utility, ESKOM is the largest supplier of electrical energy in South Africa and is currently generating and distributing on demand to approximately 3000 consumers. This represents 92% of the South African market. ESKOM was selected as the utility supplying electrical energy for the purpose of this study. ESKOM's objective is to provide the means and systems by which the consumer can be satisfied with electricity at the most cost-effective manner. In order to integrate the consumers into these objectives, ESKOM took a decision in 1994 to change the supply tariff from active power (kW) to apparent power (kVA) for a number of reasons: To establish a structure whereby the utility and the consumer can control the utilisation of electrical power supply to the consumer. To utilise demand and control through power factor correction and implementation of load management systems. To identify some cost implications of electrical power factor correction and load management. Consumers with kW maximum demand tariff options had little or no financial incentives to improve their low power factor (PF) by reducing their reactive current supply. Switching to (kVA) maximum demand will involve steps to be taken to ensure that the reactive component is kept to a minimum with maximum power factor. ESKOM has structured various tariff rates and charges with unique features that would accommodate the consumers in their demand side management and load cost requirements, which, when applied, will result in an efficient and cost effective load profile. These tariffs are designed to guide consumers automatically into an efficient way of using electrical power, as it is designed to recover both the capital investment and the operating cost within two to three years after installation of power factor correction equipment. ESKOM's concept of Time-of-use (TOU) periods for peak, standard and off-peak times during week, Saturday and Sunday periods is discussed as load management. Interruptible loads can be scheduled or shed to suit lower tariff rates and to avoid maximum demand charge. The concept of load management will change the operation pattern of the consumer's electricity demand whereby the consumer will have immediate technical and financial benefits. In the last chapter of this dissertation, a hypothetical case study addresses and concludes on some of the technical and cost implications of electrical power factor correction and load management as a successful and profitable solution to optimize electrical power supply to the consumer. By implementing the above, ESKOM ensures that the consumer utilizes the electrical power supply to its optimum level at the lowest cost per kilowatthour (kW.h) generated.