Linear optimal regulators have been designed for power system stabilization by introducing control signals to voltage regulators and/or governors. A new technique is developed in this thesis to determine the state weighting matrix Q of the regulator performance function with a dominant eigenvalue shift of the closed loop optimal system. The technique is used to investigate the stabilization of a typical one-machine infinite system and a multi-machine system with different stabilization schemes. The objective is to find the best way to stabilize a power system. An optimally sensitive controller is also developed to offset the effects of the changing system operating conditions on the effort of the stabilizing signal. The controller automatically adjusts its gains so that it always provides the system with the optimum stabilizing signal. A new multi-machine state variable formulation, necessary for these studies, is developed. It requires minimum computations and retains all the parameter information for sensitivity studies. An exact representation of synchronous machines is investigated and test methods are suggested for the determination of exact circuit parameters. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

A test method is developed to measure the equivalent (driving point) positive sequence impedance, as a function of frequency, of an operating power system. The technique used is to apply a phase-to-phase fault at the system node of interest and record the transient voltage across and current in the fault. These quantities are then transformed into the frequency domain. The system driving point impedance is then taken as the ratio of the fault voltage to the current at each point in the frequency domain. Field results from a phase-to-phase fault at a central location on the B.C. Hydro 500 k-V network are presented and analysed to determine the system driving point impedance. The measured impedance versus frequency characteristic is compared with a predicted impedance characteristic based on an Electro-Magnetic Transient program study of a detailed model of the major B.C. Hydro transmission and generation. Correlation between the measured and calculated impedance is good, with explanations offered for any localized significant disagreement. The explanations offered are subsequently verified by Ontario Hydro's improvements to the analysis of the test data and additions to the computer model data. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

This thesis describes a method for determining weak nodes in power systems which may cause divergence in Newton-Raphson loadflow methods. When divergence occurs in production loadflow programs, information related to the cause of divergence is not available. The "Weak Node Method" of this thesis provides such information by identifying one or more weak nodes. The development of the Weak Node Method required extensive experimentation with the Newton-Raphson method. The behaviour of the vectors and matrices of the Newton-Raphson method during divergence are discussed in an effort to familiarize the reader with observed trends. These trends suggested the techniques which comprise the Weak Node Method. With this method, a "quasi" solution is sought first, and, secondly, three analysis procedures are then used to pinpoint the weak nodes. The method was tested using three test cases which would normally have caused the Newton-Raphson loadflow method to diverge. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

New, fast and reliable algorithms for solving load-flow problems are presented in this thesis. Each of these algorithms iteratively solves a set of linear equations in terms of voltage magnitude squared and phase angles, and converges onto the final solution in a few iterations. Although the line losses of the system are used in deriving the equations of the basic line-loss load-flow algorithm, knowledge of their (approximate) values is not a prerequisite to using the algorithm. The basic line-loss load-flow algorithm is slightly modified to give an incremental-change line-loss algorithm which proves to be always preferable to the basic algorithm. By exploiting the weak interdependence between active power and voltage magnitude, and between reactive power and phase angle, two decoupled versions of the incremental-change line-loss algorithm were also developed. All these algorithms have constant gradient characteristics, and their storage requirements are, at most, the same as those of the standard Newton-Raphson algorithm. If need be, the storage requirements can be reduced to those of the triangularized Y-matrix iterative algorithms. Tests on various systems indicate fast and reliable convergence characteristics better than those of the Newton-Raphson algorithm and comparable, to those obtained by Stott and Alsac with their decoupled Newton-Raphson load-flow algorithm. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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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.

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy