HARVEST
University of Saskatchewan's Repository for Research, Scholarship, and Artistic Work
Welcome to HARVEST, the repository for research, scholarship, and artistic work created by the University of Saskatchewan community. Browse our collections below or find out more and submit your work.
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Recent Submissions
The Impacts of Climate Change on Water-, Food-, Vector- and Rodent-Borne Diseases
(Health Canada, 2008) Charron, Dominique; Fleury, Manon; Lindsay, Robbin; Ogden, Nicholas; Schuster Wallace, Corinne
THEORETICAL AND EXPERIMENTAL INVESTIGATIONS ON RESONANT FREQUENCIES AND NATURAL RESPONSE OF STATORS OF ELECTRICAL MACHINES
(1978-02) Girgis, Ramsis Sedhom; Verma, S. P.
Accurate assessment of values of resonant frequencies and natural response of stators is essential for the purpose of acquiring a quiet operation of electrical machines. In this thesis, an analysis of a general nature is developed for the determination of values of resonant frequencies and natural response of stators of encased construction. The derived frequency equation is applicable to all modes of vibration and can deliver information about all possible resonant frequencies of a stator. The analysis is based on the three-dimensional theory of elasticity; and it is capable of delivering information about not only the radial vibrations of stators but also about the torsional and axial vibrations.
Simplified frequency equations are also derived from the general frequency equation for the special cases of uniform vibrations along the stator circumference and along the stator length.
In order to examine the validity of the analysis, extensive experimental investigations were carried out on nine different models which represent stators of small, medium, and large electrical machines. The comparisons made between the experimental and the analytical results prove the general validity of the analysis. The experimental results also confirm the actual existence of several important phenomena predicted by the analysis. These are the phenomenon of dual resonance, the phenomenon of coupling between components of displacement, and the phenomenon of multiple resonances.
The thesis also presents a fundamental experimental study of the manner in which values of resonant frequencies, amplitudes of vibration and frequency response of stators at resonance are affected by the dynamics of teeth, windings, frame, and laminations. The findings of this study would be helpful for proper incorporation of the effects of teeth, windings, frame, and laminations in the process of accurate determination of resonant frequencies and natural response of stators. The physical interpretations of the results given in the thesis would also help in acquiring a better understanding of the vibration behavior of stators in relation to the problem of electromagnetic acoustic noise in electrical machines.
A LEAST ERROR SQUARES TECHNIQUE FOR ESTIMATING THE MAGNITUDE AND FREQUENCY OF A VOLTAGE SIGNAL
(1986-10) Giray, Mahmut Mustafa; Sachdev, M. S.
The use of digital processors in implementing protective relaying functions has attracted considerable attention in the past several years. A major part of a digital processor based relay is the algorithm which estimates the system parameters such as voltage, current and frequency, using the- digitized samples obtained from the system. Developments of suitable algorithms to detect these parameters have been a major challenge to many researchers.
This project is concerned with the development of an algorithm for estimating the magnitude and frequency of a voltage signal using the least error squares curve fitting technique. One of the main considerations is the validity of the algorithm when the magnitude and/or the frequency of the voltage substantially deviate from their nominal values. The effective use of the algorithm under such conditions has been accomplished. The use of the proposed algorithm for implementing a software based volts-per-hertz relay is also demonstrated in this project.
A DIGITAL FREQUENCY-CUM-RATE OF CHANGE OF FREQUENCY RELAY
(1978-11) Giray, Mahmut Mustafa; Sachdev, M. S.
Under-frequency relays are often used to detect deficiency of generation in a power system and to shed load to restore generation-load balance. These relays operate somewhat after the frequency falls to a prespecified level. The difference between the set frequency and the frequency at which load shedding is initiated depends on the rate at which the frequency continues to change. To eliminate this delay frequency-cum-rate of change of frequency relays have been proposed, developed and used. These relays are designed using analog electronic circuits.
The availability of digital processing devices has considerably increased during the last few years while the cost of these devices has been rapidly decreasing. The use of digital processors in system control and protection is at the verge of becoming economically competitive.
This thesis examines the presently used methods of measuring frequency and rate of change of frequency at a power system bus. A few new and novel approaches are then proposed. Also examined are the relative advantages and suitability of these approaches for use in relays based on digital processors. A relay design using the selected techniques of measuring frequency and rate of change of frequency is then outlined. Implementation of this design and relay tests performed in the laboratory are also described.
DESIGN AND IMPLEMENTATION OF A DIGITAL CONTROLLER DEVELOPMENT SYSTEM
(1977-11) Gilchrist, Rodney Dale; Bollinger, K. E.
This thesis describes the design and implementation of a minicomputer based system to develop and evaluate general purpose digital feedback controllers that will operate in the frequency range below ten hertz. An immediate area of application is in the control of turbo generators where additional signals, beyond the standard terminal voltage feedback, are used to provide damping. The feedback of such signals as the machine output electrical power has recently proved advantageous. The controller development system will be a powerful tool in further research in this area. It will allow the development of digital control techniques that could not previously be conveniently tested.
Field test results are described where, as a convenient test case, the digital system satisfactorily emulated an existing power system stabilizer on Calgary Power's Sundance unit 3. Stripchart traces are included that, illustrate the performance of the digital controller relative to the existing installed analog controller. These tests were performed with the generator operating on-line near rated load conditions. The tests point out some of the attributes and shortcomings of the prototype digital controller.
DESIGN AND IMPLEMENTATION OF A VLSI SYSTOLIC ARRAY FOR THE TRANSPORTATION SIMPLEX ALGORITHM
(1989-07) Ghatraju, Lakshmikanth; Bolton, R. J.; Abd-Al-Barr, M. H.
The increasing demand for high speed and improved performance in modem signal and image processing applications, and the availability of low-cost, high-density, high-speed VLSI devices have facilitated the design and implementation of massively parallel processors. The decreasing hardware cost and the emerging computer-aided design facilities have inspired many innovative designs in array processor architecture. One of the important advances in array processor architecture is the "systolic architecture".
In this thesis, a design of a systolic array for the transportation simplex algorithm is proposed. The transportation problem is one of the most important linear programming problems. It is a general problem of allocating limited resources among competing activities in an optimal way. A basic systolic cell design for the transportation matrix array of size n x m is presented.
A simulator for the transportation simplex algorithm was written to verify the proposed design and architecture. The initial basic feasible solution was obtained using Russell's approximation method. Another algorithm to obtain the initial basic feasible solution to the transportation problem based on the "greedy" approach is proposed. The hardware implementation of the basic cell was carried out using the QUISC silicon compiler and the associated standard cell library. The fabricated chips were found to be operational as expected at a maximum operational speed of 10 MHz.
OPTIMIZATION OF A SYSTEM USING STATISTICAL CONTROL THEORY
(1970-01) Ganesan, Krishnamurthy; Fleming, R. J.
The earlier methods for finding the optimum settings of the variable control parameters of a speed governor of a hydro-electric turbine employed arbitrary performance indices and assumed deterministic system disturbances. In this thesis, the Generalized Mean Square Error, the GMSE, is used as a performance index. The GMSE is a function of the correlation functions of input and output and is ideally suited for situations where the disturbance is non-deterministic. A method is developed to describe the random input disturbance statistically and hence to evaluate the input autocorrelation. The other correlation functions required for the evaluation of the GMSE are then derived using the input autocorrelation function and the frequency response function of the system under study. The model used in this study is a particular example of a non-minimum phase, time invariant feedback control system with a transport delay subject to a random disturbance. It is an electric turbo-generator supplying an isolated load. The turbine is provided with the conventional mechanical type governor. The trends in the variations of the GMSE resulting from changes in the statistics of the input disturbance and in the control parameters are shown.
UTILIZATION OF MONTE CARLO SIMULATION IN GENERATING CAPACITY PLANNING
(1986-09) Ghajar, Raymond; Billington, Roy
This thesis presents a formalized and practical approach using Monte Carlo simulation to assess the adequacy of generating systems. A Monte Carlo simulation method is developed to model base load generating units and utilized to calculate the state probabilities in both Markovian and non-Markovian systems. The results obtained from the simulation method are compared with those calculated by analytical methods to determine the effectiveness of simulation. A range of studies for selected unit models is conducted to examine the effect of various distributions on the system state probabilities. The basic simulation model is extended to include the duty cycle of peaking units and to examine the effect of distributional assumptions on the conditional probabilities of failure. The generating capacity models which were developed are then combined with the load model to produce generating capacity adequacy indices. These models provide a method of analysis which relaxes many of the traditional assumptions incorporated in the analytical methods used to calculate reliability indices. The models which were developed are applied to the IEEE Reliability Test System (RTS) and a test system (RBS) developed at the University of Saskatchewan. The potential application of Monte Carlo simulation to calculate an estimate of reliability worth from the individual load loss event data is also illustrated in this thesis.
The models developed in this thesis are capable of explicitly recognizing many unit and system operating considerations which influence system reliability. These models can be utilized to study a wide range of alternatives which differ in terms of unit function and system operation.
MULTIVARIABLE CONTROL OF ELECTRIC GENERATORS
(1968-03) Fleming, Ronald James; Booth, A. D.
This thesis develops a technique which can be used to analyse the performance of a frequency and voltage controlled electric generator taking into account the inherent cross coupling between the control loops. This technique is based on the fundamental concepts of multivariable control theory.
The operating characteristics of the various power system elements are formulated in the multivariable form and the matrix and signal flow graph techniques required for analysis and design are developed by way of specific numerical examples.
It is shown that this cross coupling of the frequency and voltage control loops has a significant effect on the regulating performance and that cognizance of this should be taken when the controllers are designed. It is demonstrated that the multivariable control methods can be utilized in this problem to take account of these factors and that they lead to physically realizable controller designs.
THREE SOLID STATE POWER SYSTEM PROTECTIVE RELAY DEVICES
(1961-10) Fleming, Ronald James
Three power system protective relays, a Mho Relay, a Differential Current RP ay, and a Percentage Differential Current Relay, have been designed and tested in the laboratory under simulated field conditions. Solid state semiconductor circuitry was used through-out, with particular emphasis being placed on the utilization of the unique characteristics of the Silicon Controlled Rectifier in all three devices.
This thesis discusses the principles of operation, the circuit design details and the results of the tests on the three devices. Sufficient background information on the general field of power system protection has been included to indicate the uses and methods of application of these relay devices in power system practice.