This thesis is to investigate the voltage sag, transient stability and operation feasibility of power islanding with different types of dispersed generation in distribution systems. One radial distribution feeder of Taiwan Power Company (TPC) is selected for computer simulation. The mathematical models of dispersed generations including exciters, governors of steam turbine and frequency controller of wind-driven induction generator are used in the simulation program of Matlab/Simulink. Applying the dispersed generation system with synchronous and induction generators at different locations of the test feeder by executing the short circuit and motor starting analysis to find the discrepancy in the voltage sag and the relation between the motor voltage with the motor power. Finally the simulation analysis of transient stability is executed for unbalance distribution systems with dispersed generations of steam turbines and wind-driven turbines by considering two different operation scenarios after the distribution system has been disconnected from TPC system. Different load and output power control of dispersed generation are applied to maintain the stable operation of the islanding power system. Based on the transient stability analysis, it is suggested that the service reliability of power system with critical loads can be enhanced by the dispersed power generation with proper design of load shedding and output power control.

Because of the exceptional physical, chemical, electric and mechanical properties of hard and brittle materials, such as ceramics, glass and diamond film etc, those are considerably valued in high technology industry. Although those materials can be machined using the ECDM method, but mostly used for machining hole and wire cutting, there is few application in the polishing aspect. In this study, a high-precision dynamic electrical pitting tester is employed, the electrolyte is KOH(eq), investigate the behavior of static electrochemical discharge of supply voltage and electrolyte highly to the steel ball/glass, and analysis it¡¦s machining characteristic. From the experimental results, which are SEM pictures of machined glass and variations of current and force , we can clearly infer the electrochemical discharge machining mold, and establish electrochemical I-V curve under different electrolyte highly, and furthermore machining area classify for (1) non-machining district (2) precision machining district (3) middle machining district (4) heavy machining district. The experimental results shows, the pitting of damage width and depth and supply voltage are relation in direct ratio. Under three different electrolytes highly, shows the critical voltage of pitting damage are all the same value, namely 29V, and electrolyte highly will be influenced real machining time and damaged form of surface. In the precision machining district, can get the surface roughness (Ra) reach 0.02£gm, machining depth of surface damage reach 0.3649£gm after machined for 60 seconds under the optimum operating parameter.

Two novel ultra-low-voltage (ULV) low-power (LP) variable gain amplifiers (VGA) are presented in this paper. These amplifiers based on complementary MOS transistors operating in weak inversion region are composed of pseudo-exponential current-to-current converters and analog multipliers. The gain of the amplifiers can be controlled by an exponential function circuit. The proposed circuits have been verified with the 0.25£gm CMOS technology by HSPICE simulations. The simulation results confirm the feasibility of the proposed VGAs.

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 reciprocating 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 duration of the friction on the friction electrification are investigated. Results show that the electrification voltage in the lubricated condition is much higher than that in the dry condition for the all-material pairs, but the surface voltage is reverse. The measured voltage is lower for the pair of Fe/PTFE and PTFE/Fe because the capacitance effect of the isolator disappears. When two conductors become a capacitor by inserting an insulator, such as Fe/PTFE-Fe, the frictional voltage is about 2~3 times higher than the other pairs because of the isolator capacitance. Moreover, the rotational speed, the normal load, and the duration also affect the output voltage. Among them, the rotational speed is the most significant parameter. At a certain normal load, the oil and the iron have different polarities, and their voltages increase with increasing rotational speed for Fe/Fe pair. In the polarity study; the tribo-electrification mechanism is proposed for Fe/PTFE, PTFE/Fe and Fe/PTFE-Fe pairs. The output voltages are negative at the lower and the upper specimens for Fe/PTFE and PTFE/Fe pairs, but negative and positive for Fe/PTFE-Fe pairs, respectively. After the surfaces of Fe and PTFE slide together, since the high residual negative voltage appears on PTFE, which causes the separation of induced charge on Fe, the surface residual voltage of PTFE dominates the polarity of output voltage. At Fe/PTFE-Fe pair, the polarity at the upper specimen of Fe is negative. However, the polarity at the lower specimen of Fe is positive, because the lower specimen is also influenced by the surface residual voltage of PTFE.

This dissertation describes the development of voltage regulators for the purpose of power reduction and further scaling in highly integrated system-on-chip products. Emphasis is placed on the architecture and implementation of integrated voltage regulation using commercially available components, standard CMOS technology, and a practical controller. The research spans the fundamental elements, architectural aspects, and detailed analog integrated circuit design. / text

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Multi-phase Buck is widely used in Voltage Regulator Modules design because of its low cost and simplicity. But this topology also has a lot of drawbacks. One of the most fundamental drawback is that it has narrow duty cycles when it operates at high switching frequency with low output voltage (for example 1V). Narrow duty cycles yield high switching loss which limits the switching frequency of Buck; making it difficult to design a Buck based VRM that can achieve high efficiency at a high switching frequency. In this thesis three new non-isolated full bridge topologies will be introduced to solve the aforementioned problems of Buck. One is a new non-isolated full bridge topology, this new topology use a transformer to extend the duty cycle and it capable to achieve zero voltage switching. Experimental results demonstrate that it has significant advantages over multi-phase Buck. In some applications when huge output current is required, several converters are paralleled to supply the current that is not an optimal solution. Two two-phase non-isolated full bridge topologies are proposed to solve this problem. They double the output power of one-phase non-isolated full bridge, and achieve higher efficiency with fewer switches compared with parallel two non-isolated full bridge converters. Non-isolated VRM usually is used for personal computers, VRM for servers is called power pod, and usually isolation is required for power pod due to safety considerations. Server usually require much more power than personal computers, their power consumption is around several KW. To provide the power for the server a few power modules will need to be paralleled, this kind solution is expensive and make current sharing complex. In this thesis two new two-phase isolated full bridge topologies are proposed. They are capable to operate at soft switching mode. And they double the output power compared with conventional full bridge converter. Compared with parallel two full bridge converters, they can achieve higher efficiency with fewer switches. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2008-02-28 09:53:50.23

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The present work describes the development of a control scheme for boost-type switch-mode rectifiers. While controllers for this circuit commonly use a shunt resistor or a magnetic field sensor to measure the instantaneous input or inductor current, here the inductor current is computed from the measured inductor voltage. This calculation requires knowledge of the physical properties of the inductor, most importantly its inductance, which are prone to change with operating conditions of the converter and throughout the lifetime of the inductor. The parameters of the inductor model are estimated during normal converter operation, and the inductor model is adapted accordingly. Simulation and experimental results confirm the effectiveness of the devised scheme in reducing the distortion of the input current. / Graduate / 0544 / aengel@uvic.ca