M.Ing. / Line commutated thyristor converters are proven to be natural line harmonic currentgenerating sources regardless of their operating modes. The quality of harmonic current components induced back to the lines is commonly described to be similar under both states of operation. This however does not seem to be quite obvious as far as the aggregate harmonic current contribution to the phase inputs per operating region of thyristor converters. It becomes thus important to examine the degree of association between thyristor converter operating states and the magnitude of current harmonic pollution induced back to the input lines to subsequently establish the most current harmonic polluting region of operation. For the purpose of this study, the Nyquist-Shannon theorem, best known as the sampling theorem, whereby the converter output signal or waveform is sampled by the switching function to reconstruct the input waveform, is numerically applied in conjunction with the MatLab/Simulink 7.0 which enables the simulation of the two-quadrant operation of direct current variable speed drive (DC VSD) and that of high voltage direct current link (HVDC) converter station operation, as well as physical measurements on the twoquadrant operation of the DC VSD (Saftronics DC2L) with the aid of the digital scope meter (DSO)1200 series. However, numerical analysis based on the sampling theorem, practical measurements obtained and the MatLab/Simulink simulations indicate that the converter operating states cause a randomly distributed harmonic current generation trend in the input lines as the firing angle is increased and the most harmonic current contribution cannot be attributed to a specific region of the controlled converter firing angle.

Present trends toward long distance extra high voltage transmission lines and static excitation can cause a reduction in the stability margins of a typical power system unless measures are taken to improve the system damping. Practical applications of stabilizing signals are investigated in this thesis and limitations of the design techniques discussed. An optimal control signal is derived from modern control theory. All signals are obtained from a common linearized power system and the performance is tested for large disturbance conditions on a single machine-infinite bus system where the machine, exciter and governor are represented in detail. Both types of signals are also tested on a practical four machine system model and it is shown that a similar improvement in damping can be obtained with either a stabilizing signal derived using conventional frequency response techniques or a proportional feedback controller obtained from solution of the algebraic matrix Riccati equation. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

The Wiener theory of the minimum mean square error ·criterion is well furnished by knowing the autocorrelation function of the input to the linear system. This input signal is generally an additive mixture of a piecewise continuous message and a noise. The problem considered in this paper is the determination of the autocorrelation function and also their power density spectrum of the noise component for the random base and height modulated square wave whose leading edges are periodic functions of time. We note that the adopted probability density function for heights of random square wave have Gamma-Distribution Density Function. In addition to this distribution function, we consider the rectangular and Beta-density function on the base of square waves. In fact, the leading edges of most periodic-random base function can be simply described by using the rectangular and Beta-Density function. Another matter under consideration is the visualization of the variations noise power density spectrum immersed in the masked signal (mixtured signal) with respect to the variance σ² and s² of Gamma and Beta-distribution, respectively. / M.S.

A model of the accurate harmonic allocation methods is developed to improve the current emission limits of IEEE Std.519. IEC 61000-3-6 and IEEE Std. 519 have by now been accepted as two well known standards for interconnecting the MV and HV-EHV customers to utility systems and widely adopted as standards to many power utilities. It is worth noting that the harmonic current emission limits of both standards have not been compared and justified with analytical proofs because there is still no explanation that discusses the origin of the emission limits in IEEE Std. 519, or the complex feature of IEC 61000-3-6. Two new novel methods of allocating the harmonic current emission limits for MV customers and HV-EHV customers have been proposed. Both methods have been developed in accordance with the principles of IEC 61000-3-6. Task II has compared and investgated the emission limits of both IEC 61000-3-6 and IEEE Std. 519. The difference, inconsistency and inaccuracy have been proven with the perspective of practical evaluations based on their own principles. The investigations focus on the specific numerical proofs of the resulting voltage distortions and the current emission limits in the MV and HV-EHV systems rather than on the philosophies. The proposed methods strongly support IEC 61000-3-6 and IEEE Std. 519, and add to their value; these methods could also help utilities allocate fairly and accurately harmonic emission limits to their MV and HV-EHV customers.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / This thesis presents the design and implementation of a Neutral-Point-Clamped (NPC) shunt Active Filter (AF) for non-linear loads. A NPC shunt AF is an attractive solution for AFs at the medium volage level, because it eliminates the need for cosly injection transformers. The balance of the capacitors of the direct current (dc) bus of the NPC inverter needs to maintained for stable and satisfactory operation though. Modulation techniques and their associated balancing techniques of the NPC inverter are analysed and discussed in the shunt AF setup. Specifically, the effect of Power Factor (PF), harmonics and unbalance of non-linear loads are considered. The practical design and implementation of the NPC shunt AF is presented. Practical and simulation results are presented which validates the presented theory.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographies. / by Martin Frederick Schlecht. / Sc.D.

by Yuen-Pat Lau. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 127-[129]). / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- VLSI Interconnects in Circuits --- p.1 / Chapter 1.2 --- Propagating Waves on Interconnects --- p.4 / Chapter 2 --- Theory: FDTD --- p.6 / Chapter 2.1 --- Modelling Microstrips in FDTD Mesh Space --- p.6 / Chapter 2.2 --- FDTD Implementation of a Unit Cell --- p.8 / Chapter 2.3 --- FDTD Implementation of a Lumped Element --- p.12 / Chapter 2.4 --- FDTD Implementation of a Circuit --- p.14 / Chapter 3 --- Theory: TDMS --- p.20 / Chapter 3.1 --- FDTD Circuit Simulation --- p.20 / Chapter 3.2 --- TDMS: Microstrip Characterization --- p.22 / Chapter 3.3 --- TDMS: Parameter Extraction --- p.23 / Chapter 3.4 --- TDMS: Circuit Simulation --- p.26 / Chapter 4 --- TDMS Simulations --- p.30 / Chapter 4.1 --- Example One: Loaded Diode --- p.30 / Chapter 4.2 --- Example Two: Unbalanced Mixer --- p.38 / Chapter 5 --- TDR Experiments --- p.54 / Chapter 5.1 --- Example Three: Uniform Microstrip --- p.54 / Chapter 5.2 --- Example Four: Coupled Microstrip --- p.61 / Chapter 5.3 --- Example Five: Change-in-width Microstrip --- p.67 / Chapter 6 --- Conclusion --- p.78 / Chapter 7 --- Program Listing --- p.80 / Chapter 7.1 --- Example Two: Unbalanced Mixer --- p.80 / Chapter 7.2 --- Example Five: Change-in-width Microstrip --- p.110 / Bibliography --- p.127

A new method for solving jitter noise in estimating high frequency waveform is proposed. It reduces the bias of the estimation in those points where all the other methods fail to achieve. It provides preliminary models for estimating percentiles in Normal, Exponential probability density function. Based on the model for Normal probability density function, a model for any probability density function is derived. The resulting percentiles, in turn, are used as estimates for the amplitude of the waveform. Simulation results show us with satisfactory accuracy.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 253-261). Available also in a digital version from Dissertation Abstracts.