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Beckers, Peter C. "Design of a Self Regulated and Protected Electrification Transformer." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/335.
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Van, Jaarsveld Barend Jacobus. "Wide-band modelling of an air-core power transformer winding." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85823.
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Thesis (MScEng)-- Stellenbosch University, 2013.ENGLISH ABSTRACT: The objective of this project is to develop an electromagnetic model that can be used to accurately calculate the voltage distribution in a transformer winding structure when excited with standard impulse excitation waves. This voltage distribution is required during the design stage of a power transformer to ensure that the insulation is capable of withstanding the occurring electric field stresses during these tests. This study focuses on the modelling of a single disk-type power transformer winding without the presence of an iron-core. Methods of calculating self- and mutual-inductances of transformer windings are presented and validated by means of finite element method software simulations. The same is done for the calculation methods used for calculating the capacitances in and around the winding structure. The calculated and FEM-simulated results are compared to measured values as a final stage of validation. The methods used to calculate the various model parameters seem to produce results that agrees well with measured values. The non-linear frequency dependant dissipative nature of transformer windings is also investigated and a methodology to take this into account is proposed and implemented. The complete modelling methodology proposed in this thesis, which includes the calculation of the model parameters, model synthesis and solver algorithm, are applied to an actual case study. The case study is performed on an air-core reactor manufactured using a disk-type power transformer winding. The reactor is excited with standard lightning impulse waves and the voltages along the winding are measured. The calculated and measured voltage wave forms are compared in both the frequency and time-domain. From the comparison it is found that the model accurately represents the actual transient voltage response of the testunit for the frequency range of interest during standard factory acceptance tests.
AFRIKAANSE OPSOMMING: Die doel van hierdie projek is om 'n elektromagnetiese model te ontwikkel wat gebruik kan word om die spanningsverspreiding in 'n transformatorwindingstruktuur te bereken as standaard weerligimpulstoetse toegedien word. Hierdie spanningsverspreiding word vereis tydens die ontwerpstadium van ‘n kragtransformator om te verseker dat die isolasie in staat is om die elektriese veldsterkte tydens hierdie toetse te weerstaan. Hierdie studie fokus op die modelering van 'n enkele skyftipe-kragtransformatorwinding sonder die teenwoordigheid van 'n ysterkern. Metodes van berekening van self- n wedersydse-induktansie van transformatorwindings word aangebied en getoets deur middel van Eindige-Element-Metode (EEM) simulasies. Dieselfde word gedoen vir die metodes wat gebruik word vir die berekening van die kapasitansies in en rondom die windingstruktuur. Die berekende en EEM-gesimuleerde resultate word vergelyk met die gemeete waardes as 'n finale vlak van bekragtiging. Die metodes wat gebruik word om die verskillende modelparameters te bereken vergelyk goed met gemete waardes. Die nie-lineêre frekwensie-afhanklike verliese van transformatorwindings word ook ondersoek en 'n metode om hierdie in ag te neem is voorgestel en geïmplementeer. Die volledige voorgestelde modeleringsmetodiek in hierdie tesis, wat die berekening van die modelparameters, modelsintese en oplosingsalgoritme insluit word toegepas op 'n werklike gevallestudie. Die gevallestudie is uitgevoer op 'n lugkern-reaktor wat 'n skyftipe-kragtransformatorwinding. Die reaktor word onderwerp aan die standaard weerligimpuls golwe en die spanning al langs die winding word gemeet. Die berekende en gemete spanning golf vorms word met mekaar vergelyk in beide die frekwensie- en tyd-vlak. Uit die vergelyking blyk dit dat die model die werklike oorgangspanningsweergawe van die toetseenheid akkuraat verteenwoordig vir die frekwensie reeks van belang tydens standaard fabriekaanvaardingstoetse.
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Wolf, Marko. "Design and implementation of a modular converter with application to a solid state transformer." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2773.
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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.ENGLISH ABSTRACT: The purpose of a solid state transformer (SST) is to use power electronic converters to mimic the operation of the conventional distribution transformer. These power electronic converters are proposed to overcome the disadvantages of the conventional distribution transformer. The advantages of a SST include near perfect voltage regulation and harmonic isolation between the primary and secondary windings of the transformer. This thesis discusses the design and development of the different converters in a solid state transformer (SST). A prototype modular back-to-back converter is developed for the input and isolation stage of the SST. The isolation stage consists of a high voltage DC-DC converter, which transfers power across the isolation barrier of the SST. This stage is evaluated in the laboratory with special attention being paid to the efficiency of the converter. The second aspect that this thesis addresses is the output stage of the SST, namely a three phase inverter. The discussion of the output stage focuses on the losses occurring in the inverter. The switching device losses are calculated by means of an adapted numerical method as opposed to using conventional analytical methods. The presented numerical method is compared to the existing analytical method and the findings are discussed. A double loop control strategy is implemented for the output stage inverter. The inner current loop utilizes a predictive control strategy. The control analysis of the double loop controller is discussed and evaluated in the laboratory. All the converters that are discussed in this thesis are evaluated in the laboratory and the relevant measurements are included.
AFRIKAANSE OPSOMMING: Die doel van ’n drywingselektroniese transformator (DET) is om drywingselektroniese omsetters te gebruik om die werking van die konvensionele distribusietransformator na te boots. Hierdie drywingselektroniese omsetters word voorgestel ten einde die nadele van die konvensionele distribusietransformator te bowe te kom. Die voordele van ’n DET sluit in: feitlik perfekte regulering van spanning en harmoniese isolasie tussen die primˆere en sekondˆere windings van die transformator. Hierdie tesis bespreek die ontwerp en ontwikkeling van die verskillende omsetters in ’n drywingselektroniese transformator (DET). ’n Prototipe modulˆere rug-aan-rug-omsetter word ontwikkel vir die intree- en isolasiefase van die DET. Die isolasiefase bestaan uit ’n hoogspanning- GS-GS omsetter, wat drywing oor die isolasiegrens van die DET heen oordra. Hierdie omsetter word in die laboratorium ge¨evalueer met besondere aandag aan die doeltreffendheid van die omsetter. Die tweede aspek waarna in hierdie tesis gekyk word, is die uittreefase van die DET, naamlik ’n driefaseomsetter. Die bespreking van die uittreefase fokus egter op die verliese wat in die omsetter voorkom. Die verliese van die skakelaars word bereken deur middel van ’n aangepaste numeriese metode teenoor die gebruik van konvensionele analitiese metodes. Die numeriese metode wat aangebied word, word vergelyk met die bestaande analitiese metode en die bevindings word bespreek. ’n Dubbellus-beheerstrategie word vir die uittreefase-omsetter ge¨ımplementeer. Die binneste stroomlus word ge¨ımplementeer deur van ’n voorspelbare beheerstrategie gebruik te maak. Die beheeranalise van die dubbellusbeheerder word bespreek en in die laboratorium ge¨evalueer. Al die omsetters wat in hierdie tesis bespreek word, word in die laboratorium ge¨evalueer en die relevante metings word ingesluit.
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Bell, Simon Colin. "High-voltage partial-core resonant transformers." Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/2161.
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This thesis first describes the reverse method of transformer design. An existing magnetic model for full-core shell-type transformers, based on circuit theory, is summarised. A magneto-static finite element model is introduced and two sample transformers are analysed. The magnetic model based on finite element analysis is shown to be more accurate than the model based on circuit theory.
Partial-core resonant transformers are then introduced and their characteristics are explained using an equivalent circuit model. A method of measuring the winding inductances under resonant operation is developed and used to investigate the characteristics of two different tuning methods. A finite element model of the partial-core resonant transformer is developed by adopting the model for full-core shell-type transformers.
The model results accurately match the measured inductance variation characteristics of three sample transformers and predict the onset of core saturation in both axial-offset and centre-gap arrangements. A new design of partial-core resonant transformer is arrived at, having an alternative core and winding layout, as well as multiple winding taps. The finite element model is extended to accommodate the new design and a framework of analysis tools is developed. A general design methodology for partial-core resonant transformers with fixed inductance is developed. A multiple design method is applied to obtain an optimal design for a given set of specifications and restrictions. The design methodology is then extended to devices with variable inductance.
Three design examples of partial-core resonant transformers with variable inductance are presented. In the first two design examples, existing devices are replaced. The new transformer designs are significantly lighter and the saturation effects are removed. The third design example is a kitset for high-voltage testing, with the capability to test any hydro-generator stator in New Zealand. The kitset is built and tested in the laboratory, demonstrating design capability. Other significant test results, for which no models have yet been developed, are also presented. Heating effects in the core are reduced by adopting an alternative core construction method, where the laminations are stacked radially, rather than in the usual parallel direction. The new kitset is yet to be used in the field.
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Rincon-Mora, Gabriel Alfonso. "Current efficient, low voltage, low drop-out regulators." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/13359.
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Olajubutu, Michael Olaolu. "Utilizing microprocessor based relays as predictive tools to mitigate voltage instability problems that stem from the fast voltage collapse and delayed voltage recovery phenomena." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Theses/OLAJUBUTU_MICHAEL_35.pdf.
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Benwell, Andrew L. Kovaleski Scott D. "A high voltage piezoelectric transformer for active interrogation." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6847.
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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 23, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Scott D. Kovaleski. Vita. Includes bibliographical references.
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Al-Hinai, Amer. "Voltage collapse prediction for interconnected power systems." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1639.
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Thesis (M.S.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains xii, 94 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 66-67).
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Hau, King-kuen. "AC mains voltage regulation by solid-state power conversion techniques /." [Hong Kong] : University of Hong Kong, 1990. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13009503.
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Robalino, Vanegas Diego M. "Loss of life of medium voltage oil-immersed current transformers under thermal accelerated ageing a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online, 2009. http://proquest.umi.com/pqdweb?index=0&did=1934058311&SrchMode=1&sid=2&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1264684717&clientId=28564.
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侯經權 and King-kuen Hau. "AC mains voltage regulation by solid-state power conversiontechniques." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1990. http://hub.hku.hk/bib/B31209737.
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Hamrita, Takoi K. "On-line digital signal processing methods for the correction of errors in high voltage power waveform measurements." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15921.
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Milošević, Borka. "On voltage stability monitoring and control using multiagent systems." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/16355.
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Gean, Richard T. "Comparison of PWM and resonant technologies in a high voltage DC application." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42080.
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High voltage transformers inherently contain undesirable parasitic reactances. A resonant circuit formed by the leakage inductance and parasitic reflected capacitance, makes various resonant technologies practical for high voltage dc applications. The components of a typical high voltage power stage will be investigated in order to identify these parasitics and determine their influence on converter operation. Proto-type high voltage converters will be designed and built using PWM and quasi-resonant techniques and experimental results will be given.
Dc analysis will be performed for the PWM and the quasi-resonant designs in order to obtain insight into the actual operation of the two converters. The design of the two proto-type converters will be reviewed and design guidelines will be established.
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Hjartarson, Thorhallur. "Application of catastrophe theory to voltage stability analysis of power systems." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29623.
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In this thesis catastrophe theory is applied to the voltage stability problem in power systems. A general model for predicting voltage stability from the system conditions is presented and then applied to both a simple 2-bus explanatory power system and to a larger more realistic power system.
The model is based on the swallowtail catastrophe which with its three control variables is able to determine the voltage stability of the system. The model is derived directly from the systems equations. The voltage stability of the system at each specified system bus is determined by comparing the values of the swallowtail catastrophe control variables with those of the unique region of voltage stability. The control variables are calculated from the system operating conditions. If the control variables specify a point inside the stability region, the system is voltage stable; otherwise it is voltage unstable.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Lakkaraju, Talpasai. "Selection of pilot buses for VAR support and voltage stability risk analysis." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4844.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xi, 94 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 90-94).
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Su, Jingdong. "A heuristic slow voltage control scheme for large power systems." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Spring2006/j%5Fsu%5F030206.pdf.
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Siebrits, F. B. (Francois Bart). "Field implementation of a transient voltage measurement facility using HV current transformers." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53426.
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Thesis (MScEng)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: The bandwidth of standard HV measurement devices such as capacitive voltage transformers is too limited in order to measure wideband phenomena. This thesis is concerned with the investigation into a non- intrusive HV transient voltage measurement facility using standard substation HV current transformers (CI's) configured in a transconductance topology. The sensing, summation and integration of the CT capacitive earth currents are investigated. This thesis also reports on the development of a optically isolated link using optical fibre for signal transfer and a computer based data acquisition system.
AFRIKAANSE OPSOMMING: Standaard hoogspannings (HS) meettoerusting soos kapasitiewe spannmgs transformators het beperkte bandwydte vir die meet van wyeband verskynsels. Hierdie tesis handel oor die implementering van 'n HS meetstelsel wat op meinbrekende wyse oorgangsverskynsels meet deur middel van HS stroomtransformators wat in 'n transkonduktansie topologie gekonfigureer is. Die meet, sommasie en integrasie van kapasitoewe grondstrome word ondersoek. Hierdie tesis doen ook verslag aangaande die ontwikkeling van 'n optiese geisoleerde koppelvlak wat gebruik word vir seinoordrag en 'n rekenaar gebasseerde data versamelaar.
pdv201406
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Adewole, Adeyemi Charles. "Voltage stability assessment and wide area protection/control using synchrophasor measurements." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2380.
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Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016.Electric power systems are being operated closer to their designed stability limits due to the constraints caused by the continuous increase in system loading, and the lack of new power stations and transmission network infrastructure to support this increase in system loading. This coupled with the practice of long distance bulk power transmission and cascading contingencies, makes system instability and consequently blackouts inevitable. In such scenarios, system instabilities like voltage instability becomes a serious threat to the secure operation of the power system, and voltage collapse (system-wide blackouts) are prone to occur. This is often compounded by the unavailability of real-time system measurements for situational awareness from the existing Supervisory Control and Data Acquisition (SCADA)/Energy Management System (EMS) platforms which are usually based on unsynchronized SCADA measurements with a slow reporting rate of 1 measurement every 2-10 seconds. This Doctoral thesis proposes non-iterative algorithms and methods of solution based on the IEEE C37.118 synchrophasor measurements from Phasor Measurement Units (PMUs) with a high reporting rate of up to 200 measurements every second (200 fps) for voltage stability assessment and automated wide area Centralised Protection/Control (CPC) against catastrophic voltage instabilities/blackouts in power systems. Extended formulations are proposed for the Optimal Placement of PMUs (OPP) in power systems with respect to voltage stability assessment. The impact of zero injection buses, critical buses, and PMU redundancy is considered in the formulation of the OPP problem solution. The extended formulations made use of Binary Integer programming (BIP) and Modal Participation Factors (MPFs) derived from the eigenvalues of the power flow Jacobian.
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Khajjayam, Ramesh Kumar V. "Impact of optimally placed VAR support on electricity spot pricing." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4895.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains x, 105 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 99-105).
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Begovic, Miroslav M. "Analysis, monitoring and control of voltage stability in electric power systems." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54490.
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The work presented in this text concentrates on three aspects of voltage stability studies: analysis and determination of suitable proximity indicators, design of an effective real-time monitoring system, and determination of appropriate emergency control techniques. A simulation model of voltage collapse was built as analytical tool on 39-bus, 10-generator power system model. Voltage collapse was modeled as a saddle-node bifurcation of the system dynamic model reached by increasing the system loading. Suitable indicators for real-time monitoring were found to be the minimum singular value of power flow Jacobian matrix and generated reactive powers. A study of possibilities for reducing the number of measurements of voltage phasors needed for voltage stability monitoring was also made. The idea of load bus coherency with respect to voltage dynamics was introduced. An algorithm was presented which determines the coherent clusters of load buses in a power system based on an arbitrary criterion function, and the analysis completed with two proposed coherency criteria. Very good agreement was obtained by simulation between the results based on accurate and approximate measurements of the state vector. An algorithm was presented for identification of critical sets of loads in a voltage unstable power system, defined as a subset of loads whose changes have the most pronounced effect on the changes of minimum singular value of load flow Jacobian or generated reactive powers. Effects of load shedding of critical loads were investigated by simulation and favorable results obtained. An investigation was also done by sensitivity analysis of proximity indicators of the effects that locations and amounts of static var compensation have on the stability margin of the system. Static compensation was found to be of limited help when voltage instabilities due to heavy system loading occur in power systems. The feasibility of implementation of the analyses and algorithms presented in this text relies on development of a feasible integrated monitoring and control hardware. The phasor measurement system which was designed at Virginia Polytechnic institute and State University represents an excellent candidate for implementation of real-time monitoring and control procedures.Ph. D.
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Law, Yiu-yip Charles, and 羅耀業. "Loss analysis of a stepping inductor VRM converter." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29477918.
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Dike, Damian Obioma. "Index-based reactive power compensation scheme for voltage regulation a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online, 2009. http://proquest.umi.com/pqdweb?index=76&did=1919277961&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1265041751&clientId=28564.
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Kundy, Beda Jerome. "Probabilistic analytical methods for evaluating MV distribution networks including voltage regulating devices." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52414.
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Thesis (PhD)--Stellenbosch University, 2001.ENGLISH ABSTRACT: Accurate load models are required for the computation of load flows in MV distribution networks. Modem microprocessors in recent times enable researchers to sample and log domestic loads. The findings show that they are stochastic in nature and are best described by a beta probability distribution. . In rural areas two different load types may be present. Such loads are domestic and pump loads, the latter may be modelled as constant P - Q loads. An analytical tool for computing voltage regulation on MV distribution networks for rural areas feeding the mentioned loads is therefore required. The statistical evaluation of the consumer voltages requires a description of load currents at the time of the system maximum demand. To obtain overall consumer voltages at any specified risk for the two types of the loads, the principle of superposition is adopted. The present work deals with conventional 22kV three-phase distribution (te:. - te:.) connected networks as used by ESKOM, South Africa. As the result of the connected load, MV networks can experience poor voltage regulation. To solve the problem of voltage regulation, voltage regulators are employed. The voltage regulators considered are step-voltage regulators, capacitors and USE (Universal Semiconductor Electrification) devices. USE devices can compensate for the voltage drops of up to 35% along the MV distribution network, thus the criteria for the application of the USE devices is also investigated. The load currents are treated as signals when assessing the cost of distribution system over a period of time due to power losses. The individual load current signal is modelled by its mean and standard deviation. The analytical work for developing general expressions of the total real and total imaginary components of branch voltage drops and line power losses in single and three-phase networks without branches are presented. To deal with beta-distributed currents on MV distribution networks, new scaling factors are evaluated at each node. These new scaling factors are derived from the distribution transformer turns ratio and the deterministic component of the statistically distributed load currents treated as constant real power loads. In the case of an individual load current signal, the transformation ratio is evaluated from the distribution transformer turns ratio and the average value of the· signal treated as constant real power load. The evaluation of the consumer voltage percentile values can be accurately evaluated up to 35% voltage drop. This is possible by the application of the expanded Taylor series, using the first three terms. The coefficients of these three terms were obtained using a search engine imbedded in the probabilistic load flow. The general expressions for evaluating the overall consumer voltages due to statistical and non-statistical loads currents are also given. These non-statistical currents may be due to constant P - Q loads, line capacitance and the modeling of voltage regulators. The Newton-Raphson algorithm is applied to perform a deterministic load flow on singlephase networks. A backward and forward sweep algorithm is applied to perform a deterministic load flow on single and three-phase systems. A new procedure for modelling step-voltage regulators in three-phase (te:. - te:.) connected networks is outlined. Specifying a transformation ratio of 1.1 and 1.15 respectively, identifies the open-delta or closed-delta configuration for three-phase networks. The algorithms and the developed general expressions for single and three-phase networks without branches are presented in this work. A new algorithm is developed to enable the developed general expressions to be applied to practical MV distribution networks. The algorithms were tested for their accuracy by comparing the analytical results with Monte Carlo simulation and they compared well. An illustrative example to show the application of the present work on a practical MY distribution networks is presented. A criterion for the application of the USE devices is outlined. It is anticipated that, the work presented in this thesis will be invaluable to those involved in the design of MY distribution systems in developing countries.
AFRIKAANSE OPSOMMING: Akkurate lasrnodelle word benodig vir drywingsvloei analises in MV distribusiestelsels. As gevolg van nuwe digitale verwerkers is dit deesdae moontlik om huishoudelike laste te monitor. Die lasdata dui daarop dat laste stochasties is en kan met behulp van die Beta verdeling beskryf word. In landelike gebiede is daar twee tipes laste. Hulle is eendersyds huishoudelike laste en andersyds pomp-tipe laste wat as konstante P-Q laste beskou kan word. Dit is dus belangrik om toepaslike analitiese metodes te gebruik om die spanningsvalle by hierdie laste te bereken met inagname van die las-tipes. By die statistiese berekening van die verbruiker se spanning moet 'n statistiese model van die lasstroom verskaf word op die tydstip van maksimum aanvraag. Daarna moet die prinsiep van superposissie gebruik word om die spannings by verskeie nodes by 'n gespesifiseerde vertrouensinterval te bepaal. Hierdie proefskrif is gebaseer op konvensionele 22kV, drie fase distribusie (delta na delta) netwerke, soos deur Eskom, Suid Afrika gebruik. Hierdie stelsels ondervind dikwels nadelige spanningsvlakke en spanningsreëlaars word derhalwe aangewend. Hierdie reëlaars is gewoonlik van tap-tipe of daar kan ook gebruik gemaak word van kapasitore en ook elektroniese reëlaars soos die USE tipe toestelle. Laasgenoemde kan op LV vir spanningsvalle tot 35% kompenseer. In hierdie werk word die werkdrywing verliese in die geleiers bereken met behulp 'n seinmodel van die lasstrome. Die individuele lasstrome word by wyse van gemiddeldes en variasies beskryf. Om die algemene algoritmes vir die berekening van die reële en imaginêre spanningsvalle, asook die verliese in enkelfase en driefase stelsels daar te stel word aanvanklik gebruik gemaak van stelsels sonder vertakkings. Om die statistiese lasbeskrywing op die laagspanningskant na die MV vlak oor te dra word van nuwe skaalfaktore gebruik gemaak. Hierdie faktore word bereken op die basis van die transformator se verhouding en die deterministiese komponent van die statistiese verspreide lasstrome, as konstante reële drywingslaste beskou. Met die ontwikkelde metode kan die verbruiker se spanning by 'n gegewe vertrouensinterval akkuraat bereken word vir spanningsvalle tot 35%. Dit word moontlik gemaak deur die Taylor-reeks tot drie terme toe te pas. Daar moet egter gebruik gemaak word van toepaslike koëffisiënte wat bepaal word deur 'n geprogrammeerde soektog. 'n Algemene stel vergelykings om die spanning by enige verbruiker te bereken, ongeag die topologie van die netwerk, word ook gegee. Die Newton-Raphson metode word aangewend om die deterministiese drywingsvloei op enkelfase stelsels te bereken. A truwaartse-voorwaartse metode is gebruik om die drywingsvloei te bepaal vir driefase stelsels. 'n Nuwe prosedure is ontwikkel vir die modellering van die spanningsreëlaars in driefase, delta-delta netwerke. Deur gebruik te maak van 'n transformatorverhouding van 1.1 of 1.15 kan die oop-delta of toe-delta netwerke voorgestel word. 'n Nuwe algoritme is ontwikkelom multi-vertakkings in 'n netwerk te hanteer. Al die prosedures is deeglik met behulp van Monte Carlo simulasies getoets en die resultate is heel bevredigend. Om die metodes te illustreer word 'n gevallestudie ingesluit waar die metodes gebruik word om 'n netwerk te evalueer met en sonder die sogenaamde USE toestelle. Kriteria vir die aanwending van hierdie toerusting word voorgestel. Daar word verwag dat die werk soos in hierdie proefskrifuiteengesit is die ontwerp van MV distribusiestelsels, veral in ontwikkelende lande, heelwat sal verbeter.
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Turkmen, Coskun Aziz. "Calibration Of Conventional Measurement Transformers Against Harmonic Components By Using Field Measurements Of Optical Transducers And Resistive-capacitive Voltage Transformers." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611920/index.pdf.
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It is known from the literature that conventional voltage and current transformers measure inaccurate values for voltage and current harmonics which are parts of power quality. Maximum bandwidth of conventional current transformers, which are used in electricity transmission and distribution systems, is 1.5-2 kHz and it is lower for conventional voltage transformers. Also, it is known thatvoltages in some frequency spectrum are measured higher and voltages in another frequency spectrum are measured lower by the conventional voltage transformers. Furthermore, because of the phase shift of fundamental component caused by the conventional current and voltage transformers, losses and efficiency can not be calculated accurately. In this work, through the simultaneous measurements taken at the same feeder by both conventional transformers and new technology measurement transformers
amplitude and phase shift errors which are caused by conventional transformers depending on frequency and so harmonics, are examined and evaluated. Amplitude coefficients and phase shifts are determined for different types of conventional transformers to be able to calibrate measurement deviation. Through this work, measured data by conventional transformers will be accurate and realistic in terms of harmonic components. This matter is important to determine whether the accurate limits which will be set in the future possibly concerning with harmonics and interharmonics, are surpassed or not
also for punitive sanction.
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Markovic, Dejan. "Induced currents in gas pipelines due to nearby power lines." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060807.155002/index.html.
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Twining, Erika. "Voltage compensation in weak distribution networks using shunt connected voltage source converters." Monash University, Dept. of Electrical and Computer Systems Engineering, 2004. http://arrow.monash.edu.au/hdl/1959.1/9701.
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Ndimurwimo, Alexis. "Optimised small scale reative compensation for Eskom's Albany-Wesley 66/22Kv transmission system." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1008156.
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Reactive power compensation, as generated by capacitors, has been used to mitigate the constraints of power transmission and improve the power transfer of the transmission system of the South African power utility, Eskom‟s 66/22kV Albany-Wesley transmission system. An investigation was carried out on a number of current compensation schemes, and their operations, by means of load flow analysis. Different capacitor qualities and technologies were applied to alter the transmission line characteristics that resulted in acceptable voltage regulation. This resulted in easing the load on the lines and transformers and hence reducing line losses. For long transmission lines, utilities need voltage support, as provided for by different voltage compensators, to keep the terminal voltage within standard voltage regulation, and meet the designed power demand. The approach to large and small scale compensation was tested and the outcomes revealed distinct patterns that were used to confirm the hypothesis and improve the transfer of power. The templating temperature and thermal perspective as used by Eskom on line design was discussed and used to design a new transmission line. Load flow solutions were also used to plan and design the optimised transmission system as well as to determine the specification and location of the compensating capacitor banks. Capacitor banks, as a source of reactive power, were used to model the compensation in this research. Electrical protection and faults associated with the capacitors banks were discussed, as prevention to total blackout or load shedding on the transmission line in case of established contingency. Long term investment plans, to meet future electricity demands, require substantial investment hence a financial survey was carried out. Finally this dissertation selects a viable solution to meet the electrical power demands and then recommends a way forward for the Eskom‟s 66/22kV Albany-Wesley line.
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Baldwin, Thomas L. "Real-time phasor measurements for improved monitoring and control of power system stability." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06062008-170758/.
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Jacobs, D. M. (Danver Maxwill). "Voltage control of medium to high power three-phase inverter supply systems." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52608.
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Thesis (MScEng)--University of Stellenbosch, 2001.ENGLISH ABSTRACT: In this thesis a new voltage control method is developed for a three-phase inverter supply system. The inverter supply system consist of a Permanent Magnet Generator, a three-phase rectifier, a three-phase inverter plus LC-filter and a three-phase transformer in series. This system supplies power to a network or to a stand-alone load. The main focus of this thesis is on the control aspects of the inverter and the LC-filter. Different voltage control systems are investigated and compared to each other. From these methods the proposed voltage control method is developed where only the output voltages are measured to establish good voltage control. All these voltage control methods are also simulated with a software package. The proposed voltage control method compares very well with other voltage control methods. The results that are obtained in the simulations are satisfactory. The proposed voltage control method is also implemented in an 8 kW laboratory scale model and, again, very good practical results are obtained. A TMS320F240 nsp controller is used to implement the proposed voltage control method. The controller compensates well for load steps, and these results compare well to an alternative voltage control method, which was also evaluated practically.
AFRIKAANSE OPSOMMING: In hierdie tesis IS 'n nuwe spanningsbeheermetode ontwikkel VIr 'n drie-fase wisselrigter kragtoevoerstelsel. Die wisselrigter kragtoevoerstelsel bestaan uit 'n Permanent Magneet Generator, 'n drie-fase gelykrigter, 'n drie-fase wisselrigter plus Le-filter, en 'n drie-fase transformator in serie. Hierdie stelsel voorsien krag aan 'n netwerk sowel as aan 'n alleenstaande las. Die hooffokus van hierdie tesis is op die beheeraspekte van die wisselrigter en Le-filter. Verskillende spanningsbeheermetodes is deeglik ondersoek en vergelyk met mekaar. Uit hierdie metodes is dan die voorgestelde beheermetode ontwikkel waar slegs die uittreespanning gemeet word om goeie spanningsbeheer te kan doen. Al hierdie spanningsbeheermetodes is dan gesimuleer met 'n sagteware pakket. Die voorgestelde spanningsbeheermetode vergelyk baie goed met die ander spanningsbeheermetodes. Die resultate verky in die simulasies is ook baie bevredigend. Die voorgestelde beheermetode is ook geïmplementeer op 'n 8 kW laboratorium skaalmodel en weereens is baie goeie praktiese resultate verky. 'n TMS320F240 DSP-beheerder is gebruik om die voorgestelde beheermetode mee te implementeer. Die beheerder kompenseer baie goed vir lastrappe en vergelyk ook goed met 'n ander spanningsbeheermetode wat prakties ge-evalueer is.
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Makowski, Nathanael Jared. "Proposal and Analysis of Demagnetization Methods of High Voltage Power System Transformers and Design of an Instrument to Automate the Demagnetization Process." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/431.
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Present demagnetization methods for large power system transformers are time consuming and can be dangerous to persons performing demagnetization. The work of this thesis was to develop improved demagnetization methods and to construct an automated instrument that would implement the methods developed. One previously developed method was analyzed for effectiveness. Then, two new methods for demagnetization were developed and also analyzed for effectiveness. An automated test instrument prototype was redesigned to be able to accommodate these methods and to improve the safety of the user. The previously developed method attempts demagnetization based on current flow behavior characteristics. The first new method is a magnetic flux estimation based on saturation time. The second new method is also based on measuring saturation time, modified to account for the variable voltage loss due to wire resistance. The second of the two new methods developed proved to be the most effective for demagnetization and was able to demagnetize a transformer within an error margin of 2%. The instrument designed to perform the demagnetization with this new routine is now in early production stages for an expanded field trial with transformer maintenance teams.
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Madan, Sandhya. "Optimal allocation of reactive power to mitigate fault delayed voltage recovery." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34749.
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The Masters Thesis research focuses on reactive power and voltage control during and following major power system disturbances such as faults and subsequent loss of transmission line(s) or generator(s), voltage recovery phenomena following successful fault clearing, dynamic swings of power systems and local voltage suppression, etc. During these events, load and other system dynamics may cause reactive power deficiencies and system voltage issues such as delayed voltage recovery. These phenomena may lead to secondary events such as tripping of loads and/or circuits. Dynamic VAr sources such as generators, static VAr compensators (SVCs), STATCOMs etc and to a lesser degree static VAr sources such as capacitor or reactor banks, can help the system recover from these contingencies by providing fast modulation of the reactive power. Because of the higher cost of dynamic VAr resources, it is important to optimize the deployment of these devices by minimizing the total installed capacity of dynamic VAR resources while meeting the technical requirement and achieving the necessary performance of the system. We refer to this problem as the optimal allocation of dynamic VAR sources (OAODVARS). OAODVARS has been addressed with traditional analytic methods as well as with Artificial Intelligence methods such as genetic algorithms and Tabu search using mostly power flow type models. Both type of methods, as reported in the literature, have not provided satisfactory solutions because they ignore system dynamics and especially load dynamics, in other words they are based on power flow type models. In addition the AI methods have been proved to be extremely inefficient. We propose a new approach that has the following two advantages: (a) it is based on a realistic model that captures system dynamics and (b) it is based on the efficient successive approximation dynamic programming. The solution is provided as a sequence of planning decisions over the planning horizon. The proposed method will be demonstrated on the IEEE 24-bus reliability test system.
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Nye, Jonathan Mark. "Increasing distributed generation penetration when limited by voltage regulation." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86605.
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Thesis (MEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: This work investigated the influence of photo-voltaic generators on the voltage control of distribution feeders and the methods that can be used to increase the maximum penetration levels of these feeders. Initially, a brief overview of the reasons why it is necessary to increase the generation penetration levels on distribution feeders was provided. A review of various issues associated with connecting generation to the distribution network; methods and technologies that can be used to increase penetration levels; and ways to improve voltage regulation on MV feeders was given. The grid code for renewable power plants and the voltage apportionment standard were reviewed to determine what limits penetration levels and what can be done to increase them. The operation and control of a typical distribution network, without any connected generation, was initially investigated. A control strategy was implemented that provided suitable voltage regulation on the feeder during both high and low load. The influence of connecting generation to this typical distribution network, without making any modifications to the control of the feeder, was investigated. Base penetration levels, for various generation connection cases, were found. It was shown that the penetration is limited by the rapid voltage change or voltage rise. The base penetration levels were compared to the optimal amount of generation that provides the lowest losses. It was shown that the penetration needs to be increased by between 100% and 200% for the feeder’s losses to be minimised. Voltage regulator and capacitor control was influenced by the generation and they could not function as expected. It was shown that flicker will not be an issue, even with penetration limits well above the current allowable limits. Various methods that can be used to increase the amount of generation that is connected to the typical network were investigated. On-load tap changer setpoint reduction, reactive power control and electronic voltage regulators are some of the methods or technologies that can be used to increase penetration levels. It was shown that each of the technologies can assist, depending on the circumstance, in increasing penetration. The individual modifications can increase penetration up to 100% at the cost of increased tap changes and in some cases losses. Two proposed control strategies were assessed, that combine the investigated technologies. The results showed that it is possible to increase penetration levels by 50-80%, while improving power quality and reducing losses when compared to the base generation connection case.
AFRIKAANSE OPSOMMING: Hierdie werk ondersoek die invloed van die foto- voltaïes kragopwekkers op die spanning beheer van die verspreiding voerder asook die metodes wat gebruik kan word om die maksimum penetrasie vlakke van hierdie voerders te verhoog. Aanvanklik is 'n kort oorsig van die redes waarom dit nodig is om die opwekking penetrasie vlakke op die verspreiding voerders, te verhoog voorsien . Eerstens word 'n hersiening van verskeie kwessies wat verband hou met die koppeling van generasie na die verspreidingsnetwerk gegee. Tweedens word metodes en tegnologie wat gebruik kan word om penetrasie te verhoog gegee en laastens word maniere om spanning regulasie op medium spanning voerders te verbeter, gegee. Die rooster kode "grid code => probeer liewer netwerk regulasies" vir hernubare krag aanlegte en die spanning toedeling standaard is hersien om te bepaal wat beperk die penetrasie vlakke en wat gedoen kan word om dit te verhoog. Die werking en beheer van 'n tipiese verspreiding netwerk, sonder enige verbonde generasie, is aanvanklik ondersoek. 'n Beheer-strategie is toe geïmplementeer wat geskikte spanning regulasie op die voerder tydens beide hoë en lae belasting verskaf. Die invloed van die koppeling van opwekking tot hierdie tipiese verspreiding netwerk, sonder om enige veranderinge aan die beheer van die voerder, is ondersoek. Basis penetrasie vlakke, vir verskeie generasie verband gevalle, is gevind. Daar is bewys dat die penetrasie word beperk deur die vinnige spanning verandering of spanning styging. Die basis penetrasie vlakke word vergelyking met die optimale aantal generasie wat die laagste verliese bied. Daar is bewys dat die penetrasie moet met tussen 100% en 200% verhoog word sodat die voerder se verliese beperk kan word. Die spanning reguleerder en kapasitor beheer is beïnvloed deur die opwekking en hulle kon nie reageer soos verwag nie. Daar is getoon dat flikker nie 'n probleem sal wees nie; selfs al is die penetrasie vlakke ver bo die huidige toelaatbare grense. Verskillende metodes wat gebruik kan word om die aantal generasie wat gekoppel is aan die tipiese netwerk te verhoog is ondersoek. Aan-las tap wisselaar vermindering, reaktiewe krag beheer en elektroniese spanning reguleerders is 'n paar van die tegnieke wat gebruik kan word om penetrasie te verhoog. Daar is bewys dat elkeen van die tegnologieë kan help, afhangende van die omstandighede, vir toenemende penetrasie. Die individuele veranderinge kan penetrasie verhoog tot 100% by die koste van 'n verhoogde tap veranderinge en in sommige gevalle verliese. Twee voorgestelde beheer strategieë is beoordeel, wat die ondersoek tegnologie kombineer. Die resultate het getoon dat dit moontlik is om penetrasie te verhoog met 50% tot 80%, terwyl die verbetering van gehalte en die vermindering van krag verliese in vergelyking met die basis generasie verband hou.
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Van, Schalkwyk Christine. "Analysis and design of a voltage regulator based on an AC-to-AC converter." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53254.
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Thesis (MScEng)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: This thesis discusses the analysis and design of a voltage regulator based on an AC-to-AC converter. A background study was performed on the best topology for the purpose. The chosen topology was analysed and the converter was designed in detail. A voltage sign-detector and an over-current detector were designed and built. They were used for control and protection. Three methods of control were investigated. The first was a slow but reliable method of computing the RMS value of the input voltage and then using that value and the RMS value of the desired output voltage to compute the duty ratio of the converter. The second method was fast and is an open-loop control method, where the measured input voltage and a reference value of the desired output voltage are used to compute the duty ratio. The third method is a closed-loop control method in which the input voltage, output voltage and the same reference values used in the second method are used to compute the duty ratio. All of these methods were implemented and tested.
AFRIKAANSE OPSOMMING: Hierdie tesis bespreek die analise en die ontwerp van 'n spannings reguleerder wat gebaseer is op 'n WS-na-WS omsetter. 'n Ondersoek was ingestelom die beste topologie te vind vir die doel. Die topologie wat gekies is, is toe geanaliseer en die omsetter is in detailontwerp. 'n Spannings-tekendetektor baan as ook 'n oorstroombeskermings baan was ontwerp en is gebou. Hierdie bane word gebruik vir die beheer en die beveiliging van die stelsel. Daar is drie metodes van beheer wat ondersoek is. Die eerste metode is stadig, maar betroubaar. Die metode bereken die WGK waarde van die intree spanning en gebruik dan die waarde en die WGK van die gewenste uittree spanning om die diens siklus van die omsetter uit te werk. Die tweede metode van beheer is vinnig en is 'n oop-lus metode van beheer. Hierdie metode maak gebruik van die gemete intreespanning en 'n verwysing van die gewensde uittree spanning om die dienssiklus uit te werk. Die derde metode is 'n geslote-lus beheer wat van die gamete intreespanning, die gemete uittreespanning en die verwysing soos die in die tweede beheermetode gebruik maak on die diens siklus uit te werk. AI die metodes was geimplementeer en getoets.
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Gong, Yanfeng. "Development of an improved on-line voltage stability index using synchronized phasor measurement." Diss., Mississippi State : Mississippi State University, 2005. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
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Khaniya, Dina. "Development of three-phase continuation power flow for voltage stability analysis of distribution systems." Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-11142008-101009.
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Rossouw, Frans Jacobus. "Analysis of voltage regulation and network support technologies." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51588.
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Thesis (MEng)--University of Stellenbosch, 2000.ENGLISH ABSTRACT: Recent advances in semiconductor device development pushed a large number of network devices onto the market. These devices can solve network problems more effectively and economically than ever before. Network planners need tools to analyse and implement such devices to help solve the largest network problem in South Africa: voltage regulation. Rural networks experience the majority of voltage-regulation problems in South Africa. The networks are long sub-transmission and reticulation networks and are modelled by two generic networks, namely a radial network and a two-source ring network. The equations describing voltage regulation for the generic networks are developed and implemented in PSAT, a software analysis tool. The voltage regulation for two case studies that represent the two generic networks are analysed. Four generic network devices are defined and various control methods for these devices are developed to solve the network problem. The aim of PSAT is to help the network planner to quickly evaluate a number of possible solutions and to choose the best solution for further studies. This is demonstrated with the aid of the case studies. PSAT provides a sturdy platform on which future developments, such as stability analyses, can be built. However, PSAT can already function as a stand-alone analysis tool to solve voltage regulation as a network problem.
AFRIKAANSE OPSOMMING: Onlangse vooruitgang in halfgeleier ontwikkeling het 'n groot aantal netwerktoestelle op die mark geplaas. Hierdie toestelle kan netwerk probleme doeltreffender en meer ekonomies oplos as ooit vantevore. 'n Behoefte aan 'n pakket wat netwerkbeplanners in staat stelom die netwerktoestelle te analiseer, is geïdentifiseer. So 'n pakket sal hulle help om die vernaamste netwerkprobleem in Suid-Afrika, nl. spanningsregulasie, op te los. Die oorgrote meerderheid spanningsregulasie probleme word op die platteland ondervind. Plattelandse netwerke word gekenmerk deur lang sub-transmissie en retikulasie netwerke. Hierdie netwerke word met behulp van twee generiese netwerke gemodelleer. 'n Radiale netwerk en 'n dubbelbron ringnetwerk word aangewend om enige plattelandse netwerk te analiseer. Vergelykings is vir spanningsanalise ontwikkel en in PSAT, 'n analitiese sagteware pakket, geïmplementeer. Twee gevallestudies is gedoen om die twee netwerke afsonderlik voor te stel en die vergelykings van PSAT te evalueer. Alle netwerktoestelle is in een van vier generiese kategorieë geklassifiseer. Modelle is vir elk van die kategorieë ontwikkel vtr spanningsregulasie analise. Die doel van PSAT is om die netwerk beplanner te help om vinnig en effektief soveel moontlik opsies te ondersoek as oplossings vir 'n spesifieke netwerk probleem. PSAT is reeds 'n alleenstaande pakket wat in die toekoms uitgebrei sal word om na die analise van stabilitietsprobleme te kyk.
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Li, Yun. "Voltage balancing on three-phase low voltage feeder." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/voltage-balancing-on-threephase-low-voltage-feeder(4320ec9a-f287-4e83-86fd-c8e29e8d49f4).html.
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Voltage imbalance in low voltage (LV) networks is expected to deteriorate as low carbon technologies, e.g. electric vehicles (EVs) and heat pumps (HPs) are increasingly deployed. The new electrical demand attributable to EVs and HPs would increase the voltage magnitude variation, increasing the possibility of voltages moving outside the statutory LV magnitude limits. Moreover, the single-phase nature of EVs and HPs, which will be connected via a single-phase 'line & neutral' cable to a 3-phase four-wire LV mains cable buried beneath the street, further entangles this voltage management problem; the non-balanced voltage variations in the three phases boost the levels of voltage imbalance. Excessive voltage imbalance and magnitude variation need to be mitigated to limit their adverse effects on the electric network and connected plant. The voltage imbalance in LV networks is conventionally reduced by reinforcing the network, generally at a high cost. Some modern methods for voltage imbalance mitigation have been introduced in recent years. The power electronic converter based methods are inadequate due to the generation of harmonics, significant power losses and short lifetime. Besides, automatic supply phase selection and smart EV charging rely on an advanced smart communication system, which currently is not available. This project aims to develop alternative solutions that mitigate the voltage imbalance seen in LV networks. A voltage balancing method based on Scott transformer (ST) is proposed. This method does not generate harmonics and is independent of the smart communication system. Computer simulations demonstrated the proposed method is able to convert a non-balanced 3-phase voltage into a balanced 3-phase voltage at either a point on the LV feeder or a 3-phase load supply point with the predefined voltage magnitude. Besides, a physical voltage balancing system was created based on the proposed method and it was tested in an LV network in the laboratory. The test results show the balancing system is capable of maintaining a low level of voltage imbalance on the LV feeder by rapidly compensating for the voltage rises and sags caused by single-phase load variations. This voltage balancing method is a potential solution for the network utilities to accommodate the significant penetration of low carbon technologies without breaching the network voltage limits. The impact of EVs and HPs on the LV network voltages is investigated based on a Monte Carlo (MC) simulation platform, which comprises a statistical model of EV charging demand, profiles generators of residential and HP electrical demand, and a distribution network model. The MC simulation indicates the impact of EVs and HPs is related to their distribution; when more than 21EVs and 13HPs are non-evenly distributed on a 96-customer LV feeder, the voltage limits are likely to be violated. Moreover, the effectiveness of the ST based voltage balancing method and the demand response based TOU tariff, implemented either alone or together, in mitigating the impact of EVs and HPs is investigated based on the established MC simulation platform. The results indicate the ST based balancing method alone is able to completely mitigate the voltage limit violations regardless of the penetration levels of EVs and HPs. Moreover, using both of the two investigated methods further enhances the balancing effectiveness of the ST based voltage balancing method.
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Tennakoon, Sankika. "Flicker propagation in radial and interconnected power systems." School of Electrical, Computer and Telecommunications Engineering - Faculty of Informatics, 2008. http://ro.uow.edu.au/theses/96.
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Voltage fluctuations which cause lamp flicker tend to propagate from the point of origin to various parts of a power system exhibiting some level of attenuation depending on factors such as system impedances, composition of loads and frequency components of the fluctuating waveform. Maintaining the flicker levels at various busbars below the planning limits specified by the standards is crucial, and in this regard it is important to develop an insight into the manner in which the flicker propagates via systems operating at different voltage levels. This thesis presents flicker transfer analysis methodologies applicable for radial and interconnected power systems particularly considering the influence of induction motor loads on flicker attenuation.In the first phase of the work, development of the foundations towards flicker transfer analysis methodologies is carried out by investigating the stand-alone behaviour of induction motors that are subjected to regular supply voltage fluctuations. The electrical and mechanical response of induction motors to two types of sinusoidal fluctuations in the supply voltage where (a) a positive or negative sequence sinusoidal frequency component is superimposed on the mains voltage and (b) mains voltage amplitude is sinusoidally modulated are examined. State space representation of induction motors is used to develop a linearised induction motor model describing the response of the stator current and the rotor speed to small voltage variations in the supply voltage. The results from the model reveal that various sub-synchronous and/or super-synchronous frequency components that exist in the supply voltage as small voltage perturbations can influence the dynamic response of the machine in relation to flicker. In particular, oscillations in the electromagnetic torque and rotor speed arising as a result of the applied voltage perturbations are found to be the key influencing factors controlling the stator current perturbations. It has been noted that, the speed fluctuation caused by a superimposed positive sequence voltage perturbation tends to produce extra emf components in the rotor which in turn can reflect back to the stator. This concept of multiple armature reaction has been found to be significant in large motors especially when the superimposed frequencies are closer to the fundamental frequency.The second phase of the work covers the development of systematic methods for evaluation of flicker transfer in radial and interconnected power systems taking the dynamic behaviour of induction motors into account. In relation to radial systems, small signal models are developed which can be used to establish the flicker propagation from a higher voltage level (upstream) to a lower voltage level (downstream) where induction motor loads are connected. Although this method can be applied for regular or irregular voltage fluctuations, emphasis has been given to sinusoidal voltage fluctuations arising from conventional sinusoidal amplitude modulation of upstream voltage. Moreover, the method examines the propagation of sub-synchronous and super-synchronous frequency components that exist in the supply voltage as side bands and hence determines the overall attenuation in the voltage envelope. The contribution of induction motors of different sizes and other influential factors such as system impedance, loading level of the motor are examined. It has been noted that in general higher frequency components of the upstream fluctuating voltage envelope tend to attenuate better at the downstream. A method is also presented which allows aggregation of induction motors at the load busbars in relation to flicker transfer studies.In relation to interconnected systems, a frequency domain approach which can be used to investigate the flicker transfer is presented. This approach can be considered as an extension to the impedance matrix method as described in the literature and can overcome some of the limitations of the latter method. In the proposed approach, induction motor loads are modelled in a more realistic manner to replicate their dynamic behaviour, thus enabling the examination of the frequency dependent characteristics of flicker attenuation due to induction motors and the influence of tie lines in compensating flicker at remote load busbars consisting of passive loads.To verify some of the theoretical outcomes real time voltage waveforms captured from a large arc furnace site have been used, in addition to the experimental work using a scaled down laboratory set up of a radial power system.
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Meyer, Bernard. "Opportunities for in-line, transistorbased technologies on MV and LV power distribution networks." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51864.
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Thesis (MScEng)--University of Stellenbosch, 2000.ENGLISH ABSTRACT: Once more opportunities exist for innovative technologies to be applied on MV and LV power distribution networks to meet the new challenges set by government through its National Electrification Programme (NEP) to electrify a further 2,5 million households of which a large majority are in low-density rural areas. Electronic means of voltage compensation of long MV and LV networks supplying these low-density rural areas are now possible in the form of electronic voltage regulators mounted on the secondary side of distribution transformers and service connection boxes along the LV feeders. Furthermore, it is now possible to provide remote rural agricultural customers with singlephase supplies supported by end-use technologies in the form of electronic phase converters that eliminate the need for three-phase supplies. This hybrid of supply- and end-use technologies together with Eskom's "self-build" policy has made the dream of Eskom grid power a reality.
AFRIKAANSE OPSOMMING: Nuwe geleenthede het na yore getree vir die toepassing van innoverende tegnologie op medium- en laagspannings netwerke in antwoord op die uitdagings gestel deur die regering in die vorm van die Nasionale Elektrifiseringsprogram (NEP). Die elektrifisering van 'n verdere 2,5 miljoen huishoudings waarvan die grootste gedeelte in yl bevolkte plattelandse gebiede is, word in vooruitsig gestel. Spanningskompensasie van lang laag- en mediumspannings netwerke word nou moontlik gemaak deur middel van elektroniese spanningsreguleerders, gemonteer aan die sekondere kant van distribusie transformators en in diensaansluitingskaste op laagspannings voerders. Verder is dit ook nou moontlik om afgelee landelike plase met enkelfase krag, gerugsteun deur eindverbruik tegnologie in die vorm van elektroniese fase omsetters, te voorsien. Die beskikbaarheid van hierdie tegnologie elimineer die vraag na drie-fase krag. Hierdie hibriede kombinasie van toevoer- en eindverbruik tegnologie in kohesie met die selfbou beleid van Eskom, maak dit moontlik dat 'n droom van Eskom voorsiende elektrisiteit, in 'n werklikheid omskep word.
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Molepo, Seaga Abram. "A multilevel inverter for DC reticulation." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53253.
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Thesis (MScEng)--Stellenbosch University, 2003.ENGLISH ABSTRACT: This report presents the design and development of a multilevel inverter for DC reticulation. Two main multilevel inverter topologies are introduced and discussed. The research focusses on the flying capacitor multilevel topology, since it became evident that it is more suitable for DC reticulation than the diode clamped multilevel topology. A bootstrap power supply for the gate drive circuits of a multilevel inverter is developed and its feasibility verified experimentally. A self-starting auxiliary power supply, that aims at addressing the power supply problem of DC to AC and DC to DC converters, is designed and its functionality demonstrated on a flying capacitor multilevel inverter. An FPGA based digital controller for implementing the inverter's control algorithms is also discussed. This controller incorporates a feed-forward output voltage regulation technique. Experimental results obtained with the four-level flying capacitor multilevel inverter, using the FPGA based digital controller and the self-starting auxiliary power supply, are presented in this report.
AFRIKAANSE OPSOMMING: In hierdie verslag word die ontwerp en ontwikkelling van 'n multivlak omsetter vir GS retikulasie bespreek. Twee hoof multivlak omsetter topologië word voorgestel en bespreek. Die navorsing fokus op die "vlieënde-kapasitor" multivlak topologië omdat dit duidelik geword het dat dit 'n beter opsie is vir die GS retikulasie as die diode-klamp multivlak topologië. 'n Kragbron vir die hekaandryfbane van die multivlak omsetter is ontwikkel en die werking daarvan is met experimentele toetse bevestig. 'n Self-begin kragbron, wat die probleem van die kragtoevoer aan die GS na WS en die GS na GS omsetters aanspreek, is ontwerp en die funksionaliteit is gedemonstreer met die "vlieënde-kapasitor" multivlak . omsetter. 'n Digitale beheerder, gebaseer op 'n FPGA, wat gebruik word om die omsetter se beheer algoritmes te implementeer, word ook bespreek. Hierdie beheerder inkorporeer 'n vorentoe-voer uittree spannings regulasie tegniek. Eksperimentele resultate wat gekry is met 'n vier-vlak "vlieënde-kapasitor" multivlak omsetter, wat van die FPGA gebaseerde digitale beheerder en die self-begin kragbron gebruik maak, word ook in die verslag bespreek.
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Serdyn, J. J. "Electronic voltage regulator technology for rural electrification." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/903.
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Burger, I. "Optimisation methods applied to compensator placement." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16265.
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Thesis (MScIng)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: The optimal placement of different types of compensators on electrical networks is a complex task faced by network planners and operations engineers. The successful placement of these devices normally involves a large number of power flow studies and relies heavily on the experience of the engineer. Firstly the operation and application of the different types of compensators must be clearly understood. Secondly the application of combinations of different compensators on a specific network must be investigated. Then the dynamics of the network and interaction between the network and the compensator/s must be studied under a wide variety of network conditions and load levels. This task is further complicated by the non-linear nature of the mathematical equations that govern the power flow and voltage distribution on an electrical network. Yet another complication is the fact that some of the variables that describe an electrical network can be non smooth or discrete. For instance, the discrete value of a tap position of a power transformer can only assume an integer value. To simplify the problem of compensator placement, advanced software tools are available that are capable of solving power flows of networks containing compensators. To a large degree, however, these tools still rely on the user to make intelligent decisions as to the configuration of networks and the placement of compensators. In many cases trial and error is the only way to find a good solution. The purpose of this thesis is to show the different techniques available to implement intelligent algorithms capable of finding optimal solutions specific to the placement of voltage regulators. State of the art algorithms are implemented in Matlab that can place voltage regulators on sub transmission, reticulation and low voltage networks. The sub transmission and reticulation placement algorithm is a combination of an SQP technique and a simple combinatorial algorithm. The low voltage placement program is based on a simple genetic algorithm with a few customized features that has been developed to ensure fast convergence. The programs developed were used to do optimal voltage regulator placement on a number of networks. As far as possible real world networks were used. Where real world networks were not available test networks were used that closely resemble real networks, as they exist on typical networks owned by Eskom Distribution. It was found that SQP is a very efficient algorithm for optimising large non-linear problems such as the placement of a Step Voltage Regulator on a large electrical network. This algorithm however does not handle discrete variables very well and is also limited in handlingany reconfiguration of the network due to the placement of series devices such as voltage regulators. To cater for reconfiguration, it is necessary to combine the SQP algorithm with a combinatorial algorithm. The genetic algorithm used to do optimal placement of multiple Electronic Voltage Regulators on low voltage networks was found to be very efficient and robust. This can be attributed to the simplicity of the algorithm as well as the fact that it does not rely on the availability of derivative and second derivative information to move towards an optimal solution. Instead, it only uses fitness values obtained from function evaluations to optimise the placement problem. Another useful feature of using a genetic algorithm is that the algorithm does not get stuck in sub optimal areas in the solution space. Both the placement programs developed are relatively simple and do not consider all the factors involved in the placement of voltage regulators. However, the addition of any number of factors is however possible with further development of the programs as presented in this thesis.
AFRIKAANSE OPSOMMING: Die optimale plasing van verskillende kompenseerders op elektriese kragstelsels is ´n moeilike probleem vir beplanners en operasionele personeel. Die plasing van kompenseerders gaan gewoonlik gepaard met ´n groot hoeveelheid netwerk studies en die sukses daarvan berus gewoonlik op die ondervinding van die ingenieur. Eerstens moet die werking en toepassing van elke kompenseerder behoorlik verstaan word. Tweedes moet die plasing van ´n enkele asook kombinasies van verskillende kompenseerders ondersoek word. Dan moet die dinamika van die netwerk en interaksie met die kompenseerder/s bestudeer word vir al die moontlike netwerk konfigurasies en belasting vlakke. Die taak word verder bemoeilik deur die nie-liniêre vorm van die wiskundige vergelykings wat die netwerk vrag en spanning verspeiding beskryf. Nog ´n komplikasie is die feit dat van die veranderlikes wat die probleem beskryf, diskreet is. Byvoorbeeld die tap posisie van ´n transformator kan slegs ´n heel getal aanneem. Om die plasing van kompenseerders te vergemaklik is gevorderde sagteware beskikbaar wat simulasies kan doen van netwerke wat kompenseerders bevat. Tot ´n groot mate is die sagteware nog steeds afhanklik van intellegente besluitneming deur die gebruiker. In die algemeen moet ´n groot hoeveelheid studies nog steeds gedoen work om ´n goeie oplossing te vind. Die doel van hierdie tesis is om die verskillende tegnieke te wys wat beskikbaar is om intelligente algoritmes te implementeer wat optimale oplossings kan vind vir spesifiek die plasing van spanning reguleerders. Moderne algoritmes is in Matlab geimplementeer wat spanning reguleerders op sub transmissie, retikulasie en laag spanning netwerke kan plaas. Die sub transmissie en retikulasie plasings algoritme is gebaseer op ´n kombinasie van ´n sekwensieële kwadratiese programmering metode en ´n eenvoudige kombinatoriese metode. Die laag spanning plasings program is gebaseer op ´n eenvoudige genetiese algoritme met ´n paar unieke verstellings om vinnige konvergensie te verseker. Die twee programme wat ontwikkel is word dan gebruik on spanning reguleerders te plaas op ´n paar netwerke. So ver moontlik is bestaande netwerke gebruik. Waar bestaande netwerke nie beskikbaar was nie is toets netwerke saamgestel wat gebaseer is op bestaande Eskom netwerke. Daar is gevind dat sekwensieële kwadratiese programmering ´n effektiewe algoritme is om groot nie liniêre optimerings probleme, soos die plasing van spanning reguleerders, op te los. Hierdie algoritme is egter nie geskik om diskrete veranderlikes te hanteer nie. Dit is verder ook nie geskik om enige netwerk rekonfigurasie te hanteer tydens die plasing van seriesgeskakelde kompenseerders soos spanning reguleerders nie. Om die rekonfigurasie moontlik te maak is dit nodig om die sekwensieële kwadratiese programmering te kombineer met ´n kombinatoriese algoritme. Daar is verder gevind dat die genetiese algoritme wat gebruik is om elektroniese spanning reguleerders te plaas op laag spanning netwerke baie effektief en robuust is. Dit is as gevolg van die eenvoudigheid van die algoritme en die feit dat dit nie afhanklik is van afgeleide en tweede afgeleide informasie om na die optimale oplossing te beweeg nie. Die algoritme gebruik slegs fiksheid waardes bereken van funksie evaluasies om die probleem te optimeer. Nog ´n voordeel van genetiese algoritmes is dat dit nie in sub optimale gebiede van die oplossing ruimte stil staan nie. Beide die programme wat ontwikkel is, is redelik eenvoudig en neem nie al die faktore in ag wat gepaard gaan met die plasing van spanning reguleerders nie. Addisionele faktore kan egter maklik ingesluit word deur verdere ontwikkeling van die bestaande programme.
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Visser, Abraham Johannes. "Transformerless series dip/sag compensation with a multilevel cascaded inverter." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52592.
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Thesis (MScEng)--University of Stellenbosch, 2001.ENGLISH ABSTRACT: This thesis covers the development of a multilevel cascaded inverter for the purpose of costeffective transformerless series dip compensation. Of all known power quality problems, voltage dips are the greatest reason for concern. Dips/sags occur more frequently than outages and therefore tend to be more costly for industry as modem technical equipment becomes all the more sensitive to the quality and reliability of supply. A number of devices already exist to compensate for this problem, but the cost of most of these systems does not always justify the financial losses they compensate for. All of these systems are using transformers and/or large filter components that contribute to the size, price and losses to quite a large extent. Series injection dip compensators offer the advantage of only having to compensate for the decrease in supply voltage during a dip. This results in a significant reduction in the converter ratings and energy storage requirements compared to conventional uninterruptible power supplies or shunt injection power quality devices. Existing inverter topologies, including multilevel inverters, were therefore studied and compared as possible solutions for cost-effective transformerless series dip compensation. On the basis of these considerations the multilevel cascaded inverter seems to be the most cost-effective option. The relatively low harmonic content of its unfiltered output also eliminates the need for a large output filter. A single-phase dip compensator, with this topology, was designed and built according to specifications stated by Eskom, the main utility in South Africa. Batteries as energy storage and automotive MOSFETs as switching components, proved to be most cost-effective options for the specified power ratings. Control algorithms for dip compensation with the multilevel inverter were also developed. Some of these algorithms are based on existing techniques, but two new algorithms were also developed to implement force commutation of the thyristors and to share the power dissipation in the dip compensator. Simulations indicated that these algorithms could be suitable and sufficient for their application. This dip compensator with its control algorithms was tested with a dip generator, developed at the University of Stellenbosch, for different types of loads. The experimental results confirmed the simulations and showed a very good performance for the specified conditions. An optimised design of this dip compensator will make it a cost-effective solution for dip compensation.
AFRIKAANSE OPSOMMING: Hierdie tesis dek die ontwikkeling van 'n multivlakwisselrigter, in kaskade, met koste-effektiewe transformatorlose duik kompensasie as mikpunt. Van al die bekende toevoerkwaliteit probleme wek duike in die spanning die meeste kommer. Duike kom meer gereeld voor as kragonderbrekings en neig daarom om 'n groter onkoste te wees vir die industrie soos wat moderne tegnologiese toerusting al hoe meer sensitief raak vir die kwaliteit en betroubaarheid van die toevoer. 'n Aantal toestelle wat vir hierdie probleem kompenseer bestaan reeds, maar die koste van hierdie stelsels regverdig nie altyd die finansiële verliese wat hulle moet elimineer nie. Al hierdie stelsels gebruik transformators en/of groot filter komponente wat grootliks bydra tot die grootte, prys en verliese van hierdie stelsels. Serie-injeksie kompenseerders het die voordeel dat hulle net kompenseer vir die verlies in die toevoerspanning tydens die duik. Dit het 'n beduidende vermindering in die omsetterkenwaardes en energiestoorvereistes tot gevolg in vergelyking met ononderbroke kragbronne (UPS) of newe-injeksie toevoerkwaliteit toestelle. Daarom IS bestaande wisselrigtertopologië, insluitende multivlakwisselrigters, bestudeer en vergelyk as moontlike oplossings vir koste-effektiewe serie duik-kompensasie. Van al hierdie moontlikhede lyk die multivlakwisselrigter, in kaskade, na die mees koste-effektiewe opsie. Die relatiewe lae harmoniese inhoud van sy ongefilterde uittree elimineer die behoefte aan 'n groot uittreefilter. 'n Enkelfase duik kompenseerder, met hierdie topologie, is ontwerp en gebou volgens die spesifikasies wat vasgestel is deur Eskom, die hoof elektriese kragvoorsiener in Suid-Afrika. Dit het geblyk dat batterye, en MOSFETte uit die motorbedryf, die mees koste-effektiewe opsies bied vir onderskeidelik die energiestoor en skakelkomponente. Beheeralgoritmes VIr duik kompensasie met die multivlakwisselrigter is ook ontwikkel. Sommige van hierdie algoritmes is gebaseer op bestaande tegnieke, maar twee nuwe algoritmes is ook ontwikkel vir die kommutering van die tiristors en die deling van die drywingsverkwisting in die duik kompenseerder. Simulasies dui aan dat hierdie algoritmes geskik en voldoende kan wees vir hulle toepassing. Hierdie duik kompenseerder met sy beheeralgoritmes is getoets vir verskillende tipes laste met 'n duikgenerator wat ontwikkel is by die Universiteit van Stellenbosch. Die eksperimentele resultate bevestig dit wat verkry is uit die simulasies en wys 'n goeie werkverrigting vir die gespesifiseerde kondisies. 'n Geoptimeerde ontwerp van hierdie duik kompenseerder sal dit 'n koste-effektiewe oplossing maak vir duik kompensasie.
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Becker, Martin Gerhard. "Transformerless series dip/sag compensation with ultracapacitors." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16256.
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Thesis (MScIng)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: This thesis covers the development of a transformerless series dip compensator. Of all known power quality problems, voltage dips are the greatest reason for concern. Series injection dip compensators offer the advantage of only having to compensate for the decrease in supply voltage during a dip. This results in significant reduction in converter ratings and energy storage requirements. The aim of this thesis was to take up previous developments and combine them with new technologies to maximize their functionality. The new design was implemented with ultracapacitors to offer a maintenance-free device lifespan of 20 years. As they are very expensive, a new topology was introduced in this thesis to maximize their use so that they become viable for industry. Furthermore, a new method of daisy chaining switches was introduced to minimize costs involved in controlling them. A single-phase compensator, with this new topology and the new way of controlling switches, was designed and built according to specifications stated by Eskom. This ultracapacitor-based dip compensator was tested with a dip generator, developed by the University of Stellenbosch for different load currents. The experimental results confirmed simulations made with identical parameters. This thesis presents a reliable and cost effective solution for dip compensation.
AFRIKAANSE OPSOMMING: Hierdie tesis dek die ontwikkeling van ’n transformatorlose duik kompenseerder. Van al die bekende toevoerkwaliteit probleme wek duike in die spanning die meeste kommer. Serie-injeksie kompenseerders het die voordeel dat hulle net kompenseer vir die verlies in die toevoerspanning tydens die duik. Dit het ’n beduidende vermindering in die omsetterkenwaardes en energiestoorvereistes tot gevolg. Hierdie tesis mik om vorige soortgelyke ontwikkelings op te volg en te verbeter met nuwe tegnologie om die funktionliteit te maksimeer. Die ontwerp is geimplementeer met ultrakapasitore wat die onderhoudsvrye toestel ‘n leeftyd van 20 jaar toelaat. Omdat ultrakapasitore so duur is moes ‘n nuwe topologie onwikkel word om die gebruik van ultrakapasitore meer ekonomies aantreklik te maak. Daar is ook ‘n nuwe manier van skakelaar beheer ontwikkel wat toelaat dat baie skakelaars oor een optise veesel beheer kan word. ‘n Enkel fase dip kompensaeerder is toe onwikkel en gebou volgens Eskom se spesifikasies. Die ultrakapasitor gebaseerde omsetter is getoets met ‘n dip generator wat deur die Universiteit van Stellenbosch ontwikkel is. Die praktiese resultate bevestig die simulasies wat gedoen is met dieselfe parameters. Hierdie tesis lei tot ‘n betroubaare en ekonomiese oplossing vir duik kompensasie.
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Bouhalli, Nadia. "Etude et intégration de convertisseurs multicellulaires parallèles entrelacés et magnétiquement couplés." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2009. http://tel.archives-ouvertes.fr/tel-00554341.
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L'apparition de convertisseurs multicellulaires parallèles entrelacés et magnétiquement couplés a conduit ces dernières années à améliorer les performances des convertisseurs (densité de puissance, efficacité, dynamique,...). Il existe plusieurs topologies d'entrelacement qui utilisent des Transformateurs Interphases. L'objectif principal de cette étude est de trouver parmi ces topologies celles qui sont les mieux adaptées à un contexte d'intégration d'électronique de puissance pour minimiser la taille et réduire les pertes. Une première étape de modélisation a permis d'effectuer une étude comparative de quelques topologies. Un procédé de permutation des phases d'alimentation a été présenté afin de réduire les ondulations du courant de phases et les pertes ohmiques. Les résultats obtenus valident qualitativement l'avantage de la solution retenue par rapport à la solution standard. Enfin, la réalisation pratique d'un prototype de convertisseur modulaire utilisant des Transformateurs Inter-phases est abordé. Il s'agit d'un régulateur chargé d'alimenter les microprocesseurs (1,2V/100A) (Voltage Regulator Module (VRM)) à 5 modules. Les résultats expérimentaux montrent l'avantage de l'utilisation des Transformateurs Inter-phases par rapport à la solution classique.
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Jayam, Prabhakar Aditya. "Application of STATCOM for improved dynamic performance of wind farms in a power grid." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Jayam_Prabhakar_09007dcc804f7428.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 12, 2008) Includes bibliographical references (p. 64-66).
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Chewele, Youngie Klyv. "Model predictive control of AC-to-AC converter voltage regulator." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86339.
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Thesis (MEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: The development of fast and efficient processors, programmable devices and high power semiconductors has led to the increased use of semiconductors directly in the power supply path in order to achieve strict power quality standards. New and advanced algorithms are used in the process and calculated on-line to bring about the required fast response to voltage variations. Losses in high voltage semiconductors increase with increased operating frequencies. A balance between semiconductor power losses and power quality is achieved through control of power semiconductor switching frequencies. A predictive control algorithm to achieve high power quality and limit the power losses in the high power semiconductor switches through switching frequency control is discussed for a tap switched voltage regulator. The quality of power, voltage regulator topology and the control algorithm are discussed. Simulation results of output voltage and current are shown when the control algorithm is used to control the regulator. These results are verified by practical measurements on a synchronous buck converter.
AFRIKAANSE OPSOMMING: Die ontwikkeling van vinnige en doeltreffende verwerkers, programmeerbare toestelle en hoëdrywings halfgeleiers het gelei tot 'n groter gebruik van halfgeleiers direk in die kragtoevoer pad om streng elektriese toevoer kwaliteit standaarde te bereik. Nuwe en gevorderde algoritmes word gebruik in die proses en word aan-lyn bereken om die nodige vinnige reaksie tot spanningswisselinge te gee. Verliese in hoë-spannings halfgeleiers verhoog met hoër skakel frekwensies. 'n Balans tussen die halfgeleier drywingsverliese en spanningskwalteit is behaal deur die skakel frekwensie in ag te neem in die beheer. 'n Voorspellinde-beheer algoritme om ‘n hoë toevoerkwaliteit te bereik en die drywingsverliese in die hoëdrywingshalfgeleier te beperk, deur skakel frekwensie te beheer, is bespreek vir 'n tap-geskakelde spanning reguleerder. Die toevoerkwaliteit, spanningsreguleerder topologie en die beheer algoritme word bespreek. Simulasie resultate van die uittree-spanning en stroom word getoon wanneer die beheer algoritme gebruik word om die omsetter te beheer. Hierdie resultate is deur praktiese metings op 'n sinkrone afkapper.
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Hobbs, Ivan Kevin. "Evaluation and implementation of anti-islanding methods for converter-fed distributed generation." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1559.
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MScEngThesis (MScEng (Electrical and Electronic Engineering))--Univerity of Stellenbosch, 2009.
ENGLISH ABSTRACT: As the number of distributed generation units connected to a distribution network increase, the possibility of island formation increases. An island is formed when distributed generation units continue to energize local loads within a section of the grid, which has been disconnected from the main distribution network. These islands pose significant danger to maintenance personnel as well as to members of the public. In this study, an investigation is done into various anti-islanding methods. The modes of operation of these methods are discussed, as well as their strengths and weaknesses. The slip-mode frequency shift method and the Sandia voltage shift method, in combination with over/under voltage and frequency protection, are simulated and tested to confirm their functionality. The results obtained show that it is possible to prevent distributed generation units from energizing local loads when the grid is disconnected.
AFRIKAANSE OPSOMMING: Die moontlike toekomstige toename in die aantal verspreide generasie eenhede gekoppel aan die verspreidings netwerk, verhoog die moontlikheid van eiland vorming. ‘n Eiland word gevorm wanneer verspreide generasie eenhede energie aan lokale laste voorsien nadat die netwerk ontkoppel is. Dit hou groot gevaar in vir onderhouds personeel asook vir die publiek. In die tesis word ‘n studie gedoen oor die verskillende metodes om die vorming van ongewensde eilande te voorkom. Die glipmode-frekwensieskuif metode en die Sandia spanningskuif metode word gekombineer met die oor/onder spanning en frekwensie beskerming metodes. Die kombinasie van metodes word dan gesimuleer en eksperimenteel getoets. Die verkrygde resultate toon dat dit moontlik is om die vorming van ongewensde eilande effektief te voorkom.
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Gupta, Vishal. "An accurate, trimless, high PSRR, low-voltage, CMOS bandgap reference IC." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-07052007-073154/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Ayazi, Farrokh, Committee Member ; Rincon-Mora, Gabriel, Committee Chair ; Bhatti, Pamela, Committee Member ; Leach, W. Marshall, Committee Member ; Morley, Thomas, Committee Member.