Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 22 for “"Voltage Unbalance"”.
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Voltage Unbalance-Cognizant Optimization of Distribution Grids
… (DGs) into the distribution grid has exacerbated voltage unbalance issues leading to greater risks of reducing equipment lifetime, equipment damages, and increased ohmic losses. Most approaches to regulating voltage in distribution systems only focus on voltage magnitude and neglect phasor …
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The impact of voltage unbalance and regulation on the life expectancy of LV induction machines
… they have nameplate ratings that stipulate the voltages and currents at which they may be operated. The quality of supply from power utilities can lead to them being operated under unbalanced voltage conditions. Power utilities experience voltage unbalances and voltage dips when they provide …
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Reclosing transients in standard and premium efficiency induction machines in the presence of voltage unbalance
… system which could lead to fluctuating supply voltage levels. This dissertation investigated the restarting of two different efficiency class induction machines and analyses how a shift in the phase between the supply voltage and the residual voltage affects the restarting transients. Previous …
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Impact of plug in electric vehicle battery charging on a distribution system
… battery chargers are mostly connected to the low-voltage grid for charging, hence their increased penetration coupled with uncoordinated charging could impact the distribution system in terms of voltage unbalance and transformer overloading. Although PEV battery charging is increasing, impact on …
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Induction motor variable speed drive performance and impact on energy savings
… distribute power at a line-to-line voltage of 400+/-10%. Hence in theory, the user ends up with a voltage of 340 to 440. In urban areas 2% voltage unbalance is considered acceptable, while 3% voltage unbalance is considered acceptable for rural areas. The combined effects of under or …
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Impact of plug in electric vehicle battery charging on a distribution system based on real-time digital simulator
… on the distribution system in terms of maximum voltage deviation, voltage unbalance at various locations, transformers overloading, and introducing new peaks into the system. In this research, a 12.47 kV real distribution network has been modeled using real time digital simulator, using real …
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Operation of induction machines in the presence of unbalanced supplies
… ratings when supplied with balanced sinusoidal voltages. However, the power system experiences unbalanced voltages, overvoltages, undervoltages, etc, which are seen at the motor terminals. The South African Electricity Supply Utility (Eskom) supplies the commercial and industrial systems with a …
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Voltage Balancing Techniques for Flying Capacitors Used in Soft-Switching Multilevel Active Power Filters
This dissertation presents voltage stabilization techniques for flying capacitors used in soft-switching multilevel active power filters. The proposed active filter has proved to be a solution for power system harmonics produced by static high power converters. However, voltage unbalance of the …
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Design and development of intelligent computational techniques for power quality data monitoring and management
… to handle non-linear loads faces the problem of voltage unbalance, sag, swell, momentary or temporary interruption and ultimately complete outage of EPDS. The PQ problems have motivated power system engineers to design and develop new methodologies and techniques to enhance EPDS performance. To …
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Automated detection and prediction of electrical disturbances in a power transmission system
… learning techniques are also used to predict voltage unbalance on the transmission system above a certain threshold, which yielded an accuracy of over 91%. This work will result in time savings for engineers as well as increased reliability of the transmission system by providing near …
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The Formulation of a Novel Control Framework for Regulation of an Active Low Voltage Network
The low voltage (LV) Network has become more complex due to the addition of loads like Electric Vehicles (EVs) and generation from Renewable Energy Sources (RES). These additions will result in power quality issues arising from excess supply or load unbalance. As LV networks and power systems were …
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ANALYSIS OF COMPOSITE A-C AND D-C SYSTEMS
… the effect of system dissymmetry produced by unbalanced capacitor short circuits. The performance aspects of d-c transmission links have also been examined and the mathematical models of unbalanced convertor operation using constant firing delay- and equidistant firing control have boon …
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Case study comparisons of standard and energy efficient polyphase induction motors subjected to unbalances phase voltages
… efficient polyphase induction motors under unbalanced phase voltage conditions ofup to 5 percent. Motors sizes of 25, 50, 100,150,200, 250 and 300 hp are used in this investigation. Computer simulations are used to study the efficiencies, power losses and economics of motor behavior when …
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Advance control of Dual Active Bridge Multilevel Inverter (DABMI) with Open Winding Transformer (OWT) model
… electronic converters for energy conversion. Voltage unbalance is one of the typical adverse grid disturbances commonly encountered in RES. Power quality (PQ) issues have turned out to be major problem and become extra prominent for users from all levels of usage as more nonlinear equipment …
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Development of a System for Testing Grid-connected Doubly Fed Induction Generators with Implementation of a Three-level Neutral-Point-clamped Converter
… transients during synchronisation. Control voltage excitation for the DFIG rotor circuit was achieved by the implementation of two voltage source converters (VSC’s) connected in a back-to-back configuration via a common DC-link. The rotorside converter (RSC) was responsible for regulating …
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Control Strategies for High Power Four-Leg Voltage Source Inverters
… to inverter-fed, high power systems. No-load, unbalanced loading, and non-linear loading each have unique characteristics that negatively influence the performance of the Voltage Source Inverter (VSI). Ideal, infinitely stiff power systems are uninfluenced by loading conditions; however, …
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Analysis and mitigation of the impacts of integrating fast-charging stations on the voltage fluctuations
… on three power quality phenomena, namely voltage magnitude variations, voltage unbalance, and voltage fluctuation. The Markov Chain Monte Carlo is proposed to estimate the required energy from each fast charging station when it is utilized to charge the electric vehicles, considering their …
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Development of a converter for grid-tied and isolated operation of an interior permanent magnet synchronous generator, coupled to a twin-shaft gas turbine
… control of load-side converter to regulate voltage across the load when the system is supplying power to an isolated load. This control structure also allows the grid-side converter to employ reactive power compensation, without having to regulate the DC-link voltage at the same time. In …
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Modeling of Utility Distribution Feeder in OpenDSS with Steady State Impact Analysis of Distributed Generation
… This thesis develops models for 12.47 kV (medium voltage) distribution feeders in OpenDSS by utilizing the existing models in CYMDIST. The model conversion is achieved by a detailed one-to-one component matching approach for multi phased lines, conductors, underground cables, loads, regulators and …
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Generalized theory of static power frequency changers
… Chapter 4 is devoted to the study of output voltage control. Three basic methods are analysed and detailed quantitative data for output voltage and input current waves, and the related performance indicators, are presented in graphical form. In Chapter 5 special aspects of static frequency …
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