Howard A. Smolleck

A fuzzy logic approach to unit commitment

The application of fuzzy logic to the unit commitment problem is demonstrated. This method allows a qualitative description of the behavior of a power system, the systems characteristics, and response without the need for exact mathematical formulations. It is demonstrated, through a numerical example, that a fuzzy-logic-based approach achieves a logical and feasible economical cost of operation of the power system, which is the major objective of unit commitment.

Modeling and analysis of the induction machine: a computational/experimental approach

A multicomponent approach for communicating an understanding of the behavior of an induction machine to undergraduates is presented. In this approach, students set up and perform laboratory tests to determine equivalent-circuit parameters for the machine, develop software to analyze the circuit model, and compare the simulated results with laboratory observations and theoretical expectations. It is shown how such an approach reinforces the students understanding of both the physical machine and the purpose of equivalent-circuit modeling and simulation in a more general context as well. >

Fuzzy-logic-based speed control of a shunt DC motor

The fundamental equations governing the operation of a DC motor are straightforward and are well presented in most undergraduate curricula, usually in a required energy conversion or electrical machinery class at the junior level. The physical implications of the equations regarding device behavior, and the need for speed control, are easily understood. Furthermore, students can readily develop a mental picture of the physical motor and its response. Speed control of a DC motor represents an ideal application for introducing the concepts of fuzzy logic. Once the fundamentals of fuzzy logic have been presented to the students, their application to the speed control problem can be easily demonstrated. The paper shows how a commercially available fuzzy logic development kit can be applied to the theoretical development of a fuzzy controller for motor speed, which represents a very practical class of engineering problems.

Effects of pulsed-power loads upon an electric power grid

Certain proposed particle-accelerator and laser experiments, and other devices related to fusion research, require multi-megawatt, repetitive power pulses, often at low (subsynchronous) frequency. While some power-delivery technologies call for a certain degree of buffering of the utility demand using capacitive, inductive, or inertial energy storage, considerations have also been made for serving such loads directly from the line. In either case, such pulsed loads represent non-traditional applications from the utilitys perspective which, in certain cases, can have significant design and operational implications. This paper outlines an approach to the analysis of the effects of such loads upon the electric power grid using existing analysis techniques. The impacts studied include busvoltage flicker, transient and dynamic stability, and torsional excitation. The impact of a particular pulsed load is examined and illustrated for the power network serving the Los Alamos National Laboratory. 19 refs., 13 figs.

A comprehensive interactive microcomputer capability for demonstrating AC machine operation

A software package is described for graphically and analytically demonstrating the steady-state behavior of polyphase machines under a variety of operating conditions. Implemented in the C language, the program employs sophisticated screen color graphics to show the slow-motion progression of the appropriate voltage or current waves, the loci of the resulting magnetic fields, and the movement of the machine rotor. It can be used to dynamically illustrate revolving-field concepts, the use of symmetrical components, and the effects of synchronous machine torque angle and induction machine slip. Screen movement can be frozen and significant numerical values displayed at any point during program use. The user may specify stator voltages or currents with any degree of unbalance. The neutral connection is arbitrary and can be altered during program execution. Input data may be specified or altered interactively. The program is completely menu-driven and interactive, and contains help commands and instructions which enable it to be used without additional documentation. >

A simple revolving-field demonstrator for the personal computer

A means is introduced for graphically demonstrating the concept of the revolving stator magnetic field of a polyphase machine. This is implemented on the personal computer by means of a simple Fortran algorithm. A graphics package allows dynamic display of the output. The locus of the revolving phasor may be made to travel at any convenient speed, and the demonstrator is capable of displaying the results of balanced or unbalanced stator currents of any phase sequence. A listing of the interactive Fortran algorithm developed by the author is included. Such a capability has been found useful for inclusion in personal computer-oriented machinery classroom or laboratory courses. >

Guidelines for the selection and operation of bare ACSR conductors with regard to current-carrying capacity

Abstract Factors affecting the thermal ratings of bare overhead power conductors (in particular, ACSR conductors) are reviewed. Equations for calculating the current-carrying capacity (ampacity), loss of strength, and time-temperature characteristics of ACSR conductors are illustrated and parameters used in these equations are explained. Results have been obtained for ampacity, loss of strength and conductor temperature for a typical ACSR conductor (‘Drake’) in terms of various parameters such as ambient temperature, wind velocity, and (solar) insolation by means of Fortran programs written by the authors. These results are presented in graphical form. From them, meaningful conclusions are drawn regarding the means of evaluating permissible loading levels of transmission and distribution lines, especially lines of short to moderate length. The paper has been written primarily from the standpoint of showing how information currently available to utility industry personnel can be applied to evaluate the impact of various parameters on the permissible loading levels of bare conductors. The examples presented are typical of those of interest to the Tucson Electric Power Company and other utilities.

A straightforward method for incorporating mutually-coupled circuits into the bus admittance matrix using the concept of artificial branches

A method is presented for demonstrating the effects of mutual inductive coupling to students which only requires inspection. The method, which is computationally stable for all practical cases investigated by the authors, produces no additional buses and retains the topological structure of the prototype except for the addition of some artificial lines. It is demonstrated that the procedure is applicable to a variety of situations and, once the basic principle is understood, can be immediately applied to yield a coupling-free equivalent network whose parameters are directly amenable to inclusion in the bus admittance matrix. >

Demonstration of AC machine behavior through interactive color graphics

A microcomputer program that graphically illustrates steady-state polyphase machine behavior under a variety of balanced and unbalanced operating conditions is described. Implemented in the C language, the interactive program employs sophisticated screen color graphics to show the slow-motion progression of the appropriate voltage or current waves, the loci of the resulting magnetic fields, and the movement of the machine rotor. It can be used to illustrate dynamically revolving-field concepts, the use of symmetrical components, and the operation of synchronous and induction machines under conditions of sustained electrical unbalance. The motivation for such a program, its operation, and its capabilities are described.<<ETX>>

State estimation with aid of fuzzy logic

The paper presents an approach to power system state estimation based on the application of fuzzy logic. Significant improvements in state estimates are achieved (relative to the weighted least squares algorithm) by using a hybrid estimator incorporating fuzzy logic concepts. The design of the fuzzy estimator is described. The approach is illustrated for two sample systems: a 6-bus and a 30-bus system.