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This thesis aims to establish computer methods for the transient stability analysis of electric power systems which operate isolated from the large interconnected system. A typical isolated system is characterized by a compact network in which the size of the load is relatively large when compared to the total, installed generation capacity. The stability problems are thus more severe for this system than for the grid-type system. This results in the need for more accurate representations for the system components in the computer studies. This work considers particularly the prime mover and the induction motor modelling. The accurate modelling for turbo-charged diesel engines and single shaft gas turbines is considered first due to the significative presence of these types of prime movers in the isolated systems. The quasi-steady approach is adopted in the development of these models. The induction motor modelling is then dealt with and an accurate model which accounts for the deep-bar effects and includes the stator transients is presented. In addition, this work also investigates the possibility of substituting all these detailed models by simple, reduced models in the computer simulations since the latter pose less problem in assembling the necessary data than the former ones. Furthermore, some theoretical aspects for the representation of synchronous machines, automatic voltage regulators and transformers are included in the thesis. Some insight on the numerical integration method used in the stability program - the Trapezoidal implicit - is also given in the text with the advantages and disadvantages being stated. Several studies are shown in the thesis which aim firstly to compare the various models for prime mover and induction motor representations and secondly to test the complete simulation package when dealing with stability analyses of typical isolated systems.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Sclenice in Engineering February 20th, 1998 / All available model used to determine the 50% breakdown voltage for rod-type ami conductor-type gaps subject to switching is impulse wave forms has been applied to a tower-conductor window gap configurution. The results for rod-plane, conductor-piane and tower-conductor window gaps have all been compared and correspond well with practical data. III order to app(v the model, a charge simulation technique has been adopted ill conjunction with the 'Coulomb 3D' charge simulation package. Additional tests have been performed where parameters of'the charge simulation method am! the electrode geometl:p hare been adjusted and consequent conclusions made. Recommendations for further application of tile model have been suggested. / MT2017

by Yu Chung Keung. / Chinese title: / Bibliography: leaves 158-164 / Thesis (M.Phil.) -- Chinese University of Hong Kong, 1983

The design and implementation of a dynamic voltage restorer (DVR) is presented in this thesis. The proposed DVR can restore the end-user voltage to its normal level by rapidly injecting a compensating voltage onto the power line against the upstream power disturbances. The control algorithm uses the concept of reference voltage tracking method. Based on the electric circuit theory, the filter of the DVR is also analyzed. Besides, performance of the proposed method is simulated and compared with other different control methods by using Matlab-simulink/PSB. The results show the effectiveness of the proposed method. A 2.18 KVA DVR prototype is implemented to verify the performance of the proposed method.

A low voltage and low power switch mode power amplifier is proposed. It is designed using TSMC 0.35£gm 2p4m CMOS process technology. It can be applied to hearing aids, and the supply voltage is 1.5V. Experimental results show that the proposed amplifier has the total harmonic distortion (THD) of 0.094% and power efficiency around 79.6%. The proposed power amplifier has superior performance in THD and power efficiency, and it is suitable for low-power low-voltage applications.

ABSTRACT Electrostatic discharge (ESD) influences a lot in the industries of petrochemistry, semiconductor, and electronics. ESD is one of the reasons for the deterioration of the lubricant in the lubrication system. In this study, to understand the performance of the frictional electrification of the lubricant, the circumrotating frictional electrification tester with the measurement systems is employed to investigate the friction electrification under the dry and lubricated conditions. The materials of the specimens are made of Fe and PTFE, and the paraffin base oil is used as the lubricant. Furthermore, the effects of the load, the sliding speed, and the sliding distance on the friction electrification are investigated. Results show that the electrification voltage and the surface voltage in the lubricated condition is much lower than in the dry condition for the pair of Fe/PTFE. Because the capacitance effect is almost disappears in the lubricated condition for the pair of Fe/PTFE. When two conductors become a capacitor by inserting an insulator, such as Fe/PTFE in the dry condition, the surface voltage is about 3~4 times higher than in the lubricated condition, and the frictional voltage is about 10 times higher than in the lubricated condition because of the isolator capacitance. Moreover, the oil, the PTFE and the Fe have different polarities. The surface voltage of PTFE and output voltages of Fe are negative, and surface voltage of oil are positive. The normal load, the sliding speed, and the sliding distance also affect the surface voltage of PTFE and output voltage of Fe. Among them, the load is the most significant parameter for surface voltage of PTFE, the sliding speed is the most significant parameter for output voltage of Fe.