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Suwanapingkarl, Pasist. "Power quality analysis of future power networks". Thesis, Northumbria University, 2012. http://nrl.northumbria.ac.uk/12625/.
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Abdullah, Abdullah. "Power quality analysis at Murdoch University". Thesis, Abdullah, Abdullah (2018) Power quality analysis at Murdoch University. Honours thesis, Murdoch University, 2018. https://researchrepository.murdoch.edu.au/id/eprint/41902/.
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Introduction of new electronic technologies that are more sensitive to disturbances in the power network has made it necessary to monitor the quality of power supplied. This project presents a study of the power quality at Murdoch University, and aims at identifying the causes of poor power quality and provide the solutions to these power quality problems. The main objective of this project is to analyse the power quality of the electricity system of Murdoch University in order to identify the causes of poor power quality and provide solutions to improve the power quality. Furthermore, for all the specific goals that had been set before the commencement of this project have all been accomplished. The most common power quality issues in most electrical networks globally include voltage sags, voltage swells, voltage transients, and frequency harmonics. Other power quality issues that can be experienced include voltage flicker, voltage unbalance, inter-harmonics, brownouts, direct current, short-term and long-term power interruption. A discussion of all these issues has been conducted in this report with their impacts on equipment in the network identified to be wear and tear, overheating, tripping of circuit breakers, and improper functioning of equipment. The compensating devices that can be used for improving power quality such as Active and Passive filters, Distribution Static Compensator, Dynamic Voltage Restorer, and Unified Power Quality Conditioner have also been analysed in this report. The direct and indirect costs of power quality have been reviewed in this project with the finding that 50 % of the global turnover of the electricity sector equating to 500 billion Euros is lost annually due to poor power quality. IEEE 519, AS/NZS 61000.3.2.2003, ANSI C84.1, IEEE 1459, EN 50160, and IEC 61000 are some of the power quality standards that have been discussed in Power Quality Analysis at Murdoch University this project. Based on the data collected from Murdoch University, particularly from 1.330, in substation 12, South Street Building 330, chancellery. Subsequently, the power quality problems experienced at the institution include voltage unbalance of 0.295 or 0.3486 % based on NEMA and IEC formula respectively, a 42.26 % current unbalance, distortions in current angle, power factor, and harmonic distortion in the range of 1.8 to 2.8 %.
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Cartier, J. C. "Power quality analysis in a CC-130 Hercules aircraft power distribution system". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/MQ44836.pdf.
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Palethorpe, Ben. "A novel system impedance measurement for power system analysis and improvement in power quality". Thesis, University of Nottingham, 2002. http://eprints.nottingham.ac.uk/13199/.
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This thesis presents an investigation of on-line supply impedance measurement. Network impedance values are invaluable for power system modelling and simulation. Without knowledge of a network structure and the impedances that make up that structure it is impossible to simulate or predict harmonic propagation within a plant. If the impedance structure for a plant is known then it may be possible to alleviate voltage distortion problems by simply redistributing sensitive loads to points of low harmonic distortion. Alternatively distorting loads may be repositioned thus removing the need for additional filters or compensation equipment. The supply impedance, in particular, is of interest. At a simple level it is important for wiring, fuse and circuit breaker calculations. It is also important when designing filters for power factor correction or harmonic attenuation. Two novel on-line impedance measurement techniques are presented. Both techniques apply a small disturbance to a power network, using measurements of the subsequent transients it is possible to identify the system impedance at the point of measurement. These techniques are implemented both in simulation and experimentally. Excellent identification was possible for linear impedance networks. The performance of the techniques was also investigated in the presence of various non-linear loads. Limitations to both approaches are identified. An active shunt filter was designed and constructed for this work. Experimental impedance measurement was undertaken using this hardware. It was therefore possible to demonstrate the possibility of impedance measurement using an existing active shunt filter and during its normal operation. Finally experimental measurement data was used to demonstrate the operation of the active shunt filter using reference currents determined from supply voltage and supply impedance.
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Chan, Yau Chung John. "A novel electric power quality monitoring system for transient analysis". Thesis, City University London, 2014. http://openaccess.city.ac.uk/5911/.
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Electricity is vital for our daily life in modern cites. In order to ensure its reliability and supply, an electric power monitoring system is indispensable in an electric power system. Currently, most electric power monitoring systems are designed for steady-state monitoring only. They may not be able to monitor instantaneous power disturbances, such as voltage surge, happened in electric power systems. In fact, instantaneous power disturbances are frequently found in electric power systems, which result in equipment failures and cause financial losses. Therefore, a novel electric power monitoring system is proposed in this thesis. Besides traditional functions, the proposed system is capable of monitoring and analyzing instantaneous power disturbances in electric power systems. Novelties of the proposed monitoring system are in the following three major aspects. Firstly, the proposed system is capable of monitoring instantaneous power disturbances. Unlike traditional monitoring systems, the proposed system captures not only statistical power quantities (e.g. kW, kWh), but also voltage and current waveforms. Since a considerable communication network bandwidth is required to transmit electric waveforms in a remote monitoring system, a novel waveform compression algorithm is proposed to realize real-time electric power waveform monitoring on low-speed communication networks (e.g. Zigbee). Secondly, the proposed system is capable of identifying various kinds of power disturbances automatically. It relieves electrical engineers from manned disturbance identification on preserved waveforms. Unlike traditional disturbance identification algorithms, the proposed system can identify not only voltage disturbances, but also current disturbances. Hence, it can provide a better chance in identifying more problems and disturbances in electric power systems. Thirdly, a novel time-frequency analysis method is proposed to analyze preserved waveforms. The proposed method is an improvement to the well-known Discrete Wavelet Packet Transform (DWPT). DWPT has been used by researchers and engineers to analyze disturbances and harmonics in electric power systems. However, DWPT is subjected to a non-uniform leakage problem, which has been discussed intensively in many studies. In order to tackle this issue, a frequency shifting scheme is introduced in the proposed method. A prototype has been implemented to demonstrate the feasibility of the proposed electric power monitoring system. There are two major components – a prototype meter and a central monitoring system. The performance of the prototype has been evaluated by conducting experiments and field tests. The capability of the proposed system for realtime remote monitoring has been verified on Zigbee network, which is a low-power, low speed wireless communication network.
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Omishat, Ahmad Yousef. "A Real-time Harmonic Detector Design to Improve Power Quality in Power Systems". Youngstown State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ysu150413499882562.
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Matusevicius, Tadas. "Analysis of Swedish Wind Power Forecast Quality over Forecast Horizon and Power System Operation Implications". Thesis, KTH, Elkraftteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-213706.
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Wind power, as one of the fastest growing means of generation, can oer environmentalbenets. However, due to its stochastic nature it is dicult to designaccurate prediction tools, thus the forecast errors are inherently present. Goodunderstanding of the errors that may occur is imperative for greater penetrationof wind power into the system as it can facilitate power system planning andoperation.In this paper, wind power forecasts for dierent price areas in Sweden areanalysed and compared. For this purpose, data starting November 2015 weredownloaded every hour from the Nord Pool spot database and Python code forparsing and analysis was written. Common indicators, such as the root-meansquare(RMSE) and bias error were used to characterise the accuracy of theforecasts. As expected, it was shown that in general the RMSE decreases as theforecast hour approaches the delivery hour. In addition, systematic bias erroraround the day-ahead market closure time was identied and discussed.The paper continues to analyse wind power forecast error distribution withrespect to the forecast time and dierent production levels. Four statistical momentsof distribution function were calculated and compared. It was shown thatfor the forecast horizons between 0 and 36 hours the forecast error distributionfunctions are negatively skewed leptokurtic.The temporal wind power forecast error correlations between dierent horizonsas well as the spatial correlations between dierent price areas are calculatedand discussed. As expected, a stronger correlation was identied betweenneighbouring price areas. In addition, correlation coecients between the forecasterrors and the up and down regulation prices were calculated.Finally, a model was developed to quantify the amount of operating reservelevel needed to compensate the uncertainty in the system due to wind powerand load forecasts. Future scenarios with an increasing wind power penetrationlevel are simulated and the amount of operating reserve level for individualprice areas is calculated. It was shown that with rapidly increasing wind powerpenetration, especially price area SE3 will need to plan for higher operatingreserve levels to successfully cope with the uncertainty in the load and windpower forecasts.Vindkraft, som den mest okande satt for elproduktion, kan skapa miljofordelar.Pa grund av sin stokastiska karaktar ar det svart att skapa ett exakt vindkraftprognosverktyg utan prognosfel. Lamplig uppfattning om fel ar avgorande foratt underlatta driften och planeringen av elsystemet.I den har uppsatsen analyseras och jamfors vindkraftprognoser for olika prisomradena i Sverige. Analys har utforts av data som hamtats fran och mednovember 2015 med en timmes mellanrum fran Nord Pool-spot databasen. Vanligaindikatorer, som RMSE (root-mean-square) och metodfel anvandes for attkarakterisera prognosens noggrannhet. Det visar att RMSE i allmanhet minskarnar prognostiden nar leveranstiden. Dessutom identierades och diskuteradessystematiska fel runt den dagen-forre marknaden's stangningstid.Uppsatsen fortsatter att analysera vindkraftprognosfelfordelning med hansyntill prognostid och olika produktionsnivaer. Fyra statistiska moment av fordelningsfunktionenberaknades och jamfordes. Det visades att for prognoshorisonternamellan 0 och 36 timmar ar prognosfelfordelningsfunktionerna negativaskevade leptokurtiska.Den tidsmassiga vindkraftprognosfelkorrelationen mellan olika horisonter samtde rumsliga korrelationerna mellan olika prisomraden beraknas och diskuteras.Som forvantat identierades en starkare korrelation mellan narliggande prisomraden. Dessutom beraknades korrelationskoecienter mellan prognosfel ochupp- och nedreguleringspriser.Slutligen utvecklades en modell for att kvantiera mangden av drift reservniva som behovs for att kompensera osakerheten i systemet pa grund avosakra vindkraft och lastprognoser. Framtidsscenarier med okande vindkraftspenetrationsniva simuleras och mangden driftsreservniva for enskilda prisomradenberaknas. Det visar att, med en snabbt okande vindkraftspenetration, sarskiltprisomradet SE3 kommer att behova planeras for hogre driftsreservnivaer foratt framgangsrikt klara osakerheten i last- och vindkraftprognoserna.
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Carlstedt, Tobias. "Algorithms for analysis of GSM phones’ modulation quality". Thesis, Linköping University, Department of Electrical Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-17248.
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Castillo, Luis Reguera. "Analysis and practical assessment of converter-dominated power systems : stability constraints, dynamic performance and power quality". Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30404.
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For years, large power systems have been predominantly managed using the very well known synchronous machine on the generation side. With the increasing penetration of load and generation interfaced by converter-based systems, the conventional syn-chronous machine is being gradually replaced by these new devices. However, this slow and steady change of the generation technology has led to side-effects which can affect to the local stability and, if no remedial action is taken, system-wide stability. The main objective of this thesis is to understand, expose and overcome the weak-nesses of converter-dominated grids within a laboratory environment. To do so, a converter of 10kVA has been built implementing the standard D-Q axis Current Injection (DQCI) control and, for first time to date, the Virtual Synchronous Machine with Zero Inertia (VSM0H). Further developments have been made to this control strategy to implement this theoretical algorithm into a real system. The solutions proposed in this thesis for converter-dominated grids are based on the Grid Forming Nodes (GFN) solution. This composition suggests the usage of a combination of DQCI and Virtual Synchronous Machine (VSM) converters to achieve stability within converter-dominated grids. However, there is limited understanding about VSM functioning. Initially, the application of VSM-style converters was proposed as a natural replacement of the real synchronous machine present in the system without understanding which are the specific weaknesses that affect to this type of grid. Due to the aforementioned reasons, this thesis aims to provide a more scientific and rigorous explanation of why the GFN solution can provide stability for converter-dominated power systems. Using the converter built, it is possible to recreate scenarios where the technical challenges involved in power systems can be understood. Going from well-established solutions for relatively low Levels of Penetration (LoP), such as grid-friendly or smart converters, to an insightful explanation of why these solutions are not valid for converter-dominated grids with high values of LoP. This thesis puts more emphasis on the latter case, assessing experimentally the GFN solution for representative scenarios and control strategies used in the converter built explicitly for this project. Initially, three experiments are conducted to identify the weaknesses of converter-dominated grids. During these initial scenarios, it has been found that DQCI converters behave as current sources from the grid point of view, following an already imposed voltage signal. As current sources, DQCI converters do not provide effective voltage regulation. On the contrary, GFN/VSM converters behave as voltage sources behind an inductance from the grid point of view. Thus, they contribute to the entire grid stability by assuring the local voltage stiffness. However, further experiments with unbalanced and non-linear loads have found that this capability is finite and directly dependent on the equivalent converter filter impedance. During the execution of the experiments, there have been additional contributions explained throughout this thesis: The virtual resistor technique. Incorporating an additional feed-forward term into the inner current loop, the stabilizing effect of the parasitic inductor resistance is simulated. As result, the inner control loop operates in a more stable manner. The explanation, implementation and validation of a novel control strategy which makes the converter operate with variable speed response depending on the grid events. This adaptive functioning leads to a more robust operation for both the converter and the grid. A new control strategy based on the VSM0H (so called in this thesis as VSM0H+). Measuring the negative sequence voltage present in the grid, it is possible to add a compensation term which can provide an almost perfect voltage regulation under the presence of heavily unbalanced loads.
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Palani, Kevin. "Power Quality Analysis of a Three-Phase Cycloconverter under Variable Operating Conditions". DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/314.
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The objective of this study is to observe the correlations between variable operating conditions and power quality parameters for a three-phase to single-phase cycloconverter. The cycloconverter is examined in its most straightforward form without additional output filters or elaborate control methods. Variable operating conditions include input frequency, output frequency, and resistive load size. The power quality parameters of interest are power factor, input current total harmonic distortion (THD), output voltage THD, and efficiency. The scope of the project includes analytical calculations, PSpice simulations, as well as a hardware implementation. The results show that output frequency has minimal effect on power quality. High input frequencies tend to yield less efficiency and larger loads yield higher efficiency. Total harmonic distortion undesirably peaks at a combination of low input frequency and high output frequency. Extrapolations can be made for the cycloconverter operating at different frequencies and loads based on the trends observed within the test matrix.
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Eriksson, Simon. "System Analysis of Energy-Constrained Quality of Service and Power Management Techniques". Thesis, KTH, Maskinkonstruktion (Inst.), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-99457.
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This master’s thesis is a part of the GEODES project, Global Energy Optimization for Distributed Embedded Systems, and deals with the issues regarding energy-constrained Quality of Service , QoS, in real time embedded systems. Due to the development in the areas of embedded systems, new demands have arisen. Especially for mobile devices, the increase of functionality has overrun the development of batteries. To deal with these kinds of problems a new aspect of QoS has become of interest. The new aspect is to bring power awareness into the system. Power awareness means to enable enhancements or guarantees for the lifetime of a device through intelligent software. For online decision making a software component, an energy-constrained QoS manager, is needed. The manager module may be distributed in a system or dispatched locally. The mission is to decrease power consumption by the cost of lesser performance of the system. This procedure is called to introduce system degradation into the system. A lot the research in the power management field targets single components. This thesis aims to investigate the possibilities in system level management. An analysis of existing energy-constrained QoS and power management frameworks and techniques has been made, both on system level and on component level. As a result of the analysis a specification for the interface and policies of an energy-constrained QoS power manager is presented. A fundamental choice in the specification and design was that the system in hand consist of power manageable components , PMCs, which can be seen as atomic black boxes. This modeling choice was shown to be complicated to apply in real life systems and a solution proposal for interdependencies of PMCs is discussed. A design and a prototype, the Power Manager E , PME, module, has been implemented that tries to fulfill the specifications created from the analysis. The design handles both hardware and software as PMCs and optimizes for system performance under an energy constraint, expressed through desired system runtime, set by the user of the system. The prototype is implemented on an i.MX31 platform from Freescale and runs as a module to operating system OSE 5.4 Delta provided by ENEA.Examensarbetet är en del av GEODES projektet, Global Energy Optimization for Distributed Embedded Systems. Arbetet hanterar frågor som rör energistyrd Quality of Service , QoS, i inbyggda realtidssystem. Genom den senaste utvecklingen inom området inbyggda system har nya krav introducerats. Speciellt för mobila enheter, där tillkomsten av ny funktionalitet har gått snabbare än utvecklingen av batterikapacitet. För att hantera detta så har en ny aspekt av QoS fått större intresse. Den nya aspekten är att utveckla system med en medveten energikonsumtion. Energimedvetenhet innebär mjukvara som möjliggör förbättringar eller garantier för körtiden av systemet, online eller offline. För beslut online krävs en mjukvarukomponent, en mjukvarumodul för energistyrd QoS. Uppdraget för mjukvarumodulen är att minska strömförbrukningen till kostnaden av lägre prestanda hos systemet. Detta förfarande kallas för att införa kontrollerad system degradering i systemet. Forskningen inom området koncentrerar sig mest på att minska energikonsumtionen för enskilda komponenter. I detta examensarbete så är siktet ställt på att hitta metoder som fungerar på systemnivå. En analys av befintliga ramverk och tekniker för mjukvarukontrollerad energikonsumtion samt energistyrd QoS har genomförts, både på systemnivå och på komponentnivå. Resultatet av analysen presenteras av en specifikation för en energistyrd QoS styrmodul anpassad för kontroll på systemnivå. Ett grundläggande antagande i specifikationen och implementeringen var att systemet i fråga består av komponenter med ställbar energiförbrukning. Dessa komponenter kan ses som fristående oberoende funktionaliteter. Modellantagande visade sig vara komplicerat att tillämpa på verkliga system och ett lösningsförslag vid beroenden mellan komponenter diskuteras. En design och en prototyp Power Manager E , PME, har skapats enligt den specifikation som tagits fram i rapporten. Den hanterar både hårdvara och mjukvara som ställbara komponenter och försöker optimera systemets prestanda under krav på energikonsumtion. Kravet ställs av användaren genom en önskad körtid av systemet. Protoypen är byggd på en i.MX31-plattform från Freescale och är en tilläggsmodul till OSE5.4 Delta från ENEA.
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Kondabathini, Anil Kumar. "Accurate method to measure harmonics and interharmonics in shipboard power quality analysis". Master's thesis, Mississippi State : Mississippi State University, 2006. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
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da, Silva Larsson Stefan. "Electric quality measurements and analysis of the electric power net at Händelöverket". Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-96301.
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Electric quality is a common concept for a energy delivery without interference. In time with he development of the technology which produce more complex devices connected to the lectric mains increase the demands on a electric delivery without interference. The purpose ith this report was to investigate the electric quality to chosen places at the combined power nd heating plant of E.ON in Händelö. The degree thesis is performed at the company ES lektroSandberg which have their manning/crew at Händelö. From the analyse it was suppose o show the result and give proposal to any problem that may arise. The last 10-15 years it’s been a great focus on harmonics and its influence on the electric ains. It’s easy to make the conclusion that harmonics are a great problem in our electric ains but it isn’t always like that. Certainly a net which shows a lot of harmonics can be a roblem but the greatest problem in the electric mains is the variation of voltage. That’s the eason why this report doesn’t only limits to harmonics but also includes other factors in elation to electric quality. The measurements are performed with a power quality analyser C.A 8334, from the company A Mätsystem AB. The duration for the measurements are 24 hours. When the measurements ere done, the data transfers to the PC where it can be analysed. he report begins with a general theory to give such a good platform as possible for the nalysis and the conclusion. After the theory the companies are presented. This follows by an ccount of the results that power quality analyser received. The report ends with a conclusion nd a discussion about the result. The conclusion treats interesting problems where it’s essential to inspect more in the process. hrough the result it can be concluded that the level of harmonics are pretty low in the plants. t result shows that the levels of harmonics are greatest at the converters which should not e such a surprise. In the transient analysis you will find several big transients which could ead to damages on equipments if they are not designed for big transients. The discussion does lso presents some proposals to carry through in future on the plants of Händelö.Elkvalite är ett samlingsnamn för störningsfri energileverans. I takt med att eknikutvecklingen producerar mer komplexa apparater anslutna till elnätet så ökar kraven på törningsfri elleverans. Syftet med rapporten var att sätta sig in i begreppet elkvalite för att edan undersöka elkvaliten på utvalda platser vid E.ONs kraftvärmeverk på Händelö. xamensarbetet är utfört hos företaget ES ElektroSandberg som har bemanning på Händelö. tifrån analysen var det meningen att resultat skulle redovisas samt att eventuella tgärdsförslag ges. De senaste 10-15 åren har det fokuserats mycket på övertoner och dess inverkan på elnätet när an talar om elkvalite. Det är då lätt att dra slutsatsen att övertoner skulle vara ett stort roblem i våra elnät men så är inte fallet. Visserligen kan ett nät som uppvisar större mängder ara ett problem men det största problemen i elnäten är de spänningsvariationer som erhålls. ärför har det i rapporten inte bara fokuserats på övertoner utan på fler störningsmoment som ehandlar elkvalite. Mätningar har utförts med en inlånad nätanalysator C.A 8334, från företaget CA Mätsystem B. Mätningarna har skett under ett dygn där data sedan överförts till en dator för att sedan unna analyseras. Rapporten inleder med övergripande teori för att ge en så bra plattform som möjligt för nalysen och slutsatsen. Efter teorin presenteras företagen. Detta följs av en redovisning av de resultat som nätanalysatorn erhöll. Slutligen avslutas rapporten med en slutsats och diskussion ring resultatet. Slutsatsen behandlar vissa problematiseringar där det är nödvändigt att granska mer rocessmässigt. Generellt är det inga större övertonsnivåer i de ställverk där mätningar har tförts. Övertonsnivån är störst vid frekvensomriktarna vilket inte var någon överraskning. I ransientanalysen påträffas flera stora transienter som kan medföra skador på utrustningar om e inte är dimensionerade för stora transienter. I diskussionen presenteras också förslag till framtidaarbeten inom anläggningen.
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Zhou, Long. "Smart grid analysis with particular references to power quality and load forecast". Thesis, City University London, 2010. http://openaccess.city.ac.uk/8709/.
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The electricity industry was designed more than 50 years ago when the load and generation was less, now we are in the information age with a digital society where the demand is very high, this has forced the electricity infrastructure to its limits which was not designed for, in addition, the electricity demand continues to grow. So the focus of the question becomes what we need to do from technology prospective to meet that growing demand for electricity, and do it in a way that we don't create a greater carbon footprint. Smart grid is the next generation of the electricity infrastructure based on the optimisation of the current system in all levels. Since the current system is facing various problems from increasing disturbances, system is operating on the limit, aging equipments, load change etc. therefore an improvement is essential to minimize these problems. To enhance the current system and resolve the issues that it's facing, Smart grid must have the right tools to solve it and reduce it. First of all, this thesis gives a brief concept of smart grid and summarizes many issues about smart grid, such as strategy planning, drivers for develop the Smart Grid, key characteristics, technologies of the Smart Grid, benefits in implementing Smart Grid, key Challenges, implementation sequence. And then this thesis discusses smart metering system and its standards. Secondly, this thesis reports on development of a new approach to deal with power quality problem. Wavelet Transform (WT) is used for the new approach. Complex Morlet Wavelet (CMW) is selected for the new approach introduced in this thesis. The proposed algorithm is able to identify all harmonic components including integer, non-integer and sub-harmonics. Comparing with DFT, the proposed algorithm achieves exact estimation of the harmonic frequency. Thirdly, reports on the development of a WT-based dynamic waveform reconstruction algorithm which is able to identify amplitude variations of harmonic components of the distorted waveform in the examined period. At last, this thesis reports a new Wavelet-GA-ANN based hybrid model for accurate prediction of short-term load forecast. Finally, the conclusions and future work will be given.
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Simons, Rowena Chrystal. "An exploratory analysis of quality management audit findings at a nuclear power station". Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2382.
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Thesis (MTech (Quality))--Cape Peninsula University of Technology, 2016.The quality assurance role is an essential function in high risk industries such as the nuclear power industry where process failures can potentially have catastrophic results. As part of mitigating the risk inherent in such industries, the need for reliable quality assurance cannot be over-emphasised. Underpinning a reliable quality assurance function, lies the need for effective identification of risk; as well as effective decision making processes by competent auditors. A nuclear quality assurance (QA) department has noted an increase in the variability of its audit outcomes, which has resulted in the value of the audit process being questioned by various stakeholders. The research endeavoured to: explore and describe the practice amongst auditors when rating audit findings; potentially identify reasons for inconsistencies amongst auditors when rating findings; and provide recommendations to improve both the consistency amongst auditors when rating audit finding and the overall performance of the audit process. An exploratory study using the Delphi technique was adopted to enable multiple iterations of qualitative and quantitative data collection and analysis, mimicking elements of a sequential exploratory strategy.
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Gupta, Gunjan. "An analysis and improvement of selected features of power quality of grid-tied alternative energy systems". Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2696.
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Thesis (PhD (Electrical Engineering))--Cape Peninsula University of Technology, 2018.Electrical energy can be easily used and converted to other forms of energy for various applications. Technological advancement increases the dependency on electricity to a great extent. Various internal and external factors are responsible for the bad quality of power in power systems. The performance of the system is greatly affected by the presence of harmonics, as well as voltage and frequency variations, which leads to the malfunctioning of the device and decline of power quality and supply at load side. The reactive power compensation is carried out for better power quality. The literature survey is done to find the best and efficient scheme for reactive power compensation and mitigation of various power quality problems. The devices which are used to measure various power quality factors are discussed. Various mitigating schemes are surveyed in order to compensate reactive power and to improve the power quality at the distribution end. The integration of the most widely used renewable energy, wind energy in the distribution system creates technical issues like stability of the grid, harmonic distortion, voltage regulation, active and reactive power compensation etc. which are restricted to IEC and IEEE standards. One of the topics this thesis addresses is regulation in the reactive power generated along with voltage regulation by using an effective power electronics device known as a STATCOM. The main power quality factors like overvoltage and voltage flickers are mitigated by establishing STATCOMs in small wind farms. The wind farms are equipped with three wind turbines. These three wind turbines found in the wind farm can be operated together or one after another with an introduced delay. A glitch in even a little piece of a power grid can result in loss of efficiency, income and at times even life. In this manner, it is basic to outline a system which can distinguish the faults of the power system and take a faster response to recover it back to required reactive power. Two devices STATCOM and D-STATCOM are used for this purpose in this thesis. The D-STATCOM circuit and operating principle are also discussed in thesis. Different topologies of D-STATCOM discussed with their benefits and shortcomings. The voltage, current and hybrid technologies of D-STATCOM are also discussed.
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Ballukja, Erjon. "Power Quality Analysis in DC/DC Converters under Steady State and Transient Conditions". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Znajdź pełny tekst źródłaStreszczenie:
The modern electric power systems are going through significant changes because of continuous increasing demand of electric power. Further, a growing number of renewable energy systems that directly deliver DC power jointly considered with the advance in DC technology allows a more efficient and affordable use of energy. Furthermore, a rising use of DC systems and microgrids in a wide number of applications has motivated the study of Power Quality (PQ). The concept of power quality in DC systems and microgrids brings many challenges and the aim of this thesis is to understand the delivered power quality in DC microgrid systems. In this thesis, the effects of low frequency range (0-2 kHz) conducted emissions on power quality from a microgrid based DC/DC converter under steady state and transient loading conditions represent the main purpose of this work. Indeed, for a DC distribution network there is a lack of standards and guidelines concerning power quality issues and acceptable levels of conducted disturbances in the aforementioned frequency range. Consequently, the objective of this thesis is to quantify adequate power quality indices for DC systems or networks with connected loads such as Low Frequency Sinusoidal Disturbance (% LFSD) and Amplitude Probability Distribution (APD) indices.
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Valdyke, Brad E. "A cost-benefit analysis of power quality management in the avionics repair facility". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA352954.
Pełny tekst źródłaStreszczenie:
Thesis (M.S. in Management) Naval Postgraduate School, March 1998."March 1998." Thesis advisor(s): Katsuaki L. Terasawa, Keebom Kang. Includes bibliographical references (p. 81-82). Also available online.
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Näslund, My. "Power Quality Analysis of a 110 MW Wind Farm in a 130 kV Switchyard". Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-181193.
Pełny tekst źródłaStreszczenie:
Good power quality is not only determined by uninterruptable power supply, voltage deviations also affect the function of the network and the equipment connected. Electromagnetic disturbances as flicker, harmonics, interharmonics and unbalance are decreasing the power quality. How are the measurement methods and restrictions stated, to keep the voltagedeviations within reasonable limits and thereby maintaining the networkfunction? Lillgrund wind farm has power quality restrictions set by E.ON Elnät to fulfil in the connection point to the subtransmission network. In addition isa fault ride through requirement set by SVK. All equipment connected tothe network are introducing voltage changes, which can be measured at the point of connection. The scope of the thesis has been to explicitly determine Lillgrund‟s emissions. Three-phase voltage and current measurements have been performed, with measurement systems comprising different bandwidth, to analyse the power quality parameters.Comparisons between standard documentation and technical specifications have been made in order to precise what is considered as good power quality and how it can be measured accurately.
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Todeschini, Grazia. "Wind Energy Conversion Systems based on DFIG Technology used as Active Filters: Steady-State and Transient Analysis". Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/97.
Pełny tekst źródłaStreszczenie:
This thesis deals with the performance of a Wind Energy Conversion System operating as a power generator and Active Filter simultaneously. As a power generator, the Wind Energy Conversion System converts wind energy into electric energy; as an Active Filter, it sinks the harmonic currents injected by Non-Linear Loads connected at the same feeder. Three control systems are developed to ensure the described operation; a specific study regarding the compensation of the triplen harmonics is carried out; Doubly-Fed Induction Generator derating is defined; and an engineering economic analysis is performed to determine the profitability of the proposed operation. The Wind Energy Conversion System performance as generator and Active Filter has been studied for steady-state analysis, fast transients and low transients. It is concluded that the proposed control systems allow operating the Wind Energy Conversion System as power generator and harmonic compensator both during steady state and transient operation; the described operation causes power loss increase and voltage distortion that determine the choice of the component and require system derating.
21
Musoni, Nkusi Emmanuel. "Analysis of the effect of renewable generation on the power quality of the grid, modelling and analysis of harmonic and voltage distortion". Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2805.
Pełny tekst źródłaStreszczenie:
Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018.As the electric energy demand grows, there is a significant increase in the penetration of renewable generation (RG) in the existing electrical grid network. Interconnecting of renewable generation technologies to an existing distribution system has proven to provide various benefits such as meeting the growing load demand and its contribution to energy system decarbonisation, long-term energy security and expansion of energy access to new energy consumers in the developing urban and rural areas. However, the aim of this thesis is to conduct a study on the impacts of renewable generation on the power quality of electrical grid. Therefore, this work aims at assessing the potential effects of Distributed Generation (DG) on the operation of electric power system by modelling of harmonics and voltage distortion. With different types of renewable generation available at present, it is believed that some designs contribute significantly to electrical network’s Power Quality (PQ). After the analysis of harmonic currents (chapter 6 and 7 of this thesis) introduced by renewable generation technologies, their negative impact on the power quality of the grid is seen to be apparent at point of connection (POC) but only within controlled limits. Analytical method for modeling of harmonic interactions between the grid and aggregated distributed generation technologies are investigated using DIgSILENT Power Factory software and the results obtained are discussed.
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Rosado, Sebastian Pedro. "Analysis of Electric Disturbances from the Static Frequency Converter of a Pumped Storage Station". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34448.
Pełny tekst źródłaStreszczenie:
The present work studies the disturbances created in the electric system of a pumped storage power plant, which is an hydraulic generation facility where the machines can work as turbines or pumps, by the operation of a static frequency converter (SFC). The SFC is used for starting the synchronous machines at the station when in the pump mode. During the starting process several equipment is connected to the SFC being possible to get affected by the disturbances generated. These disturbances mainly include the creation of transient overvoltages during the commutation of the semiconductor devices of the SFC and the introduction of harmonics in the network currents and voltages. This work analyzes the possible effects of the SFC operation over the station equipment based on computer simulations. For this purpose, the complete system was modeled and the starting process simulated in a computer transient simulator program. The work begins with a general review of the effects of electric disturbances over high voltage equipment and in particular of the disturbances generated by power electronics conversion equipment. Then the models for the different kind of equipment present in the system are discussed and formulated. The control system that governs the operation of the SFC during the starting process is analyzed later as well as the operation conditions. Once the model of the system is set up, the harmonic analysis of the electric network is done by frequency domain and time domain methods. Time domain methods are also employed for the analysis of the commutation transient produced by the SFC operation. Finally, the simulation results are used to evaluate the impact of the SFC operation on the station equipment, especially on the generator step up transformer.Master of Science
23
Royer, Loic. "Unraveling the Structure and Assessing the Quality of Protein Interaction Networks with Power Graph Analysis". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-62562.
Pełny tekst źródłaStreszczenie:
Molecular biology has entered an era of systematic and automated experimentation. High-throughput techniques have moved biology from small-scale experiments focused on specific genes and proteins to genome and proteome-wide screens. One result of this endeavor is the compilation of complex networks of interacting proteins. Molecular biologists hope to understand life's complex molecular machines by studying these networks. This thesis addresses tree open problems centered upon their analysis and quality assessment.
First, we introduce power graph analysis as a novel approach to the representation and visualization of biological networks. Power graphs are a graph theoretic approach to lossless and compact representation of complex networks. It groups edges into cliques and bicliques, and nodes into a neighborhood hierarchy. We demonstrate power graph analysis on five examples, and show its advantages over traditional network representations. Moreover, we evaluate the algorithm performance on a benchmark, test the robustness of the algorithm to noise, and measure its empirical time complexity at O (e1.71)- sub-quadratic in the number of edges e.
Second, we tackle the difficult and controversial problem of data quality in protein interaction networks. We propose a novel measure for accuracy and completeness of genome-wide protein interaction networks based on network compressibility. We validate this new measure by i) verifying the detrimental effect of false positives and false negatives, ii) showing that gold standard networks are highly compressible, iii) showing that authors' choice of confidence thresholds is consistent with high network compressibility, iv) presenting evidence that compressibility is correlated with co-expression, co-localization and shared function, v) showing that complete and accurate networks of complex systems in other domains exhibit similar levels of compressibility than current high quality interactomes.
Third, we apply power graph analysis to networks derived from text-mining as well to gene expression microarray data. In particular, we present i) the network-based analysis of genome-wide expression profiles of the neuroectodermal conversion of mesenchymal stem cells. ii) the analysis of regulatory modules in a rare mitochondrial cytopathy: emph{Mitochondrial Encephalomyopathy, Lactic acidosis, and Stroke-like episodes} (MELAS), and iii) we investigate the biochemical causes behind the enhanced biocompatibility of tantalum compared with titanium.
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Nduku, Nyaniso Prudent. "Development of methods for distribution network power quality variation monitoring". Thesis, Cape Peninsula University of Technology, 2009. http://hdl.handle.net/20.500.11838/1144.
Pełny tekst źródłaStreszczenie:
Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009The purpose of this project is to develop methods for distribution network power quality' variations monitoring. Power quality (PO) has become a significant issue for both power suppliers and customers. There have been important changes in power system regarding to power quality requirements. "Power quality" is the combination at voltage quality and current quality. The main research problem of the project is to investigate the power quality of a distribution network by selection of proper measurement, applying and developing the existing classic and modern signal conditioning methods for power disturbance's parameters extracting and monitoring. The research objectives are: To study the standard lEC 61000-4-30 requirements. to investigate the common couplings in the distribution network. To identity the points for measurement, to develop MySQL database for the data from the measurement and to develop MATLAB software tor simulation of the network To develop methods based on Fourier transforms for estimation of the parameters of the disturbances. To develop software for the methods implementation, The influence of different loads on power quality disturbances are considered in the distribution network. Points on the network and meters according to the lEC power quality standards are investigated and applied for the CPUT Bellville campus distribution network. The implementation of the power quality monitoring for the CPUT Bellville campus helps the quality of power supply to be improved and the used power to be reduced. MATLAB programs to communicate with the database and calculate the disturbances and power quality parameters are developed.
25
Ami, Sumit Mazumder. "Power quality improvements in low voltage distribution networks containing distributed energy resources". Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/81410/1/Sumit%20Mazumder_Ami_Thesis.pdf.
Pełny tekst źródłaStreszczenie:
In this thesis various schemes using custom power devices for power quality improvement in low voltage distribution network are studied. Customer operated distributed generators makes a typical network non-radial and affect the power quality. A scheme considering different algorithm of DSTATCOM is proposed for power circulation and islanded operation of the system. To compensate reactive power overflow and facilitate unity power factor, a UPQC is introduced. Stochastic analysis is carried out for different scenarios to get a comprehensive idea about a real life distribution network. Combined operation of static compensator and voltage regulator is tested for the optimum quality and stability of the system.
26
Settipalli, Praveen. "AUTOMATED CLASSIFICATION OF POWER QUALITY DISTURBANCES USING SIGNAL PROCESSING TECHNIQUES AND NEURAL NETWORKS". UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_theses/430.
Pełny tekst źródłaStreszczenie:
This thesis focuses on simulating, detecting, localizing and classifying the power quality disturbances using advanced signal processing techniques and neural networks. Primarily discrete wavelet and Fourier transforms are used for feature extraction, and classification is achieved by using neural network algorithms. The proposed feature vector consists of a combination of features computed using multi resolution analysis and discrete Fourier transform. The proposed feature vectors exploit the benefits of having both time and frequency domain information simultaneously. Two different classification algorithms based on Feed forward neural network and adaptive resonance theory neural networks are proposed for classification. This thesis demonstrates that the proposed methodology achieves a good computational and error classification efficiency rate.
27
Yockey, Ron David. "An investigation of the type I error rates and power of standard and alternative multivariate tests on means under homogeneous and heterogeneous covariance matrices and multivariate normality and nonnormality /". Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992945.
Pełny tekst źródła
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Kennedy, Christopher J. "A logistic life cycle cost-benefit analysis of power quality management in the avionics repair facility". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA346903.
Pełny tekst źródłaStreszczenie:
Thesis (M.S. in Management) Naval Postgraduate School, June 1998.Thesis advisor(s): Katsuaki L. Terasawa, Keebom Kang. "June 1998." Includes bibliographical references (p. 75-76). Also available online.
29
Zhan, Ming Hui. "Analysis and evaluation of soft-switching techniques for 3-phase 4-wire shunt power quality compensators". Thesis, University of Macau, 2006. http://umaclib3.umac.mo/record=b1678022.
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Srndovic, Milan <1987>. "Theoretical and Experimental Analysis of Output Power Quality in Single-Phase Cascaded H-Bridge Multilevel Inverters". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/7817/1/PhD%20thesis%20-%20Milan%20Srndovic%20-%20final.pdf.
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In this thesis simple closed-form asymptotic solutions for estimating the output power quality in single-phase cascaded H-bridge multilevel inverters are presented for staircase modulation technique and pulse-width modulation (PWM) technique. The analysis is carried out in the time domain considering the whole harmonic content and being used for an arbitrary inverter level count.
In case of the staircase modulation technique, the voltage and current ripple normalized means square (NMS) expressions are obtained in time domain considering the fundamental period. Voltage and current total harmonic distortions (THDs) as a function of the corresponding NMS values are defined as constrained optimization ones. Optimizing the voltage and current THDs determines the voltage and current optimal switching angles over the modulation index range. The current THD is understood as voltage frequency weighted THD that assumes a pure inductive load, but it is practically accurate for inductively dominant RL-loads. The same approach for estimating the current quality is given for a grid-connected inverter.
In the case of the PWM technique, the voltage and current THDs are estimated supposing that the ratio between switching and fundamental frequencies is (infinitely) large (asymptotic assumption). The voltage and current ripple normalized mean square (NMS) values are obtained in time domain by double integration of their normalized squared ripples over the switching and fundamental periods. They present piecewise continuously differentiable analytical solutions with only elementary functions and can be understood as the time-domain equivalent of the frequency-domain double Fourier transformation. The direct relation between the voltage and current NMS values and their qualities is presented. Considering the same approach, the current THD evaluation in case of a grid-connected system is presented.
Besides analytical developments, simulation and experimental verifications for three-level (one H-bridge), five-level (two cascaded H-bridges) and seven-level (three cascaded H-bridges) single-phase inverters are analysed, presented and compared in details.
31
Thunberg, Erik. "On the Benefit of Harmonic Measurements in Power Systems". Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3219.
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Grobler, Frederik Antonie. "The development of harmonic content and quality of electricity supply measuring system incorporating scada processing". Thesis, Bloemfontein : Central University of Technology, Free State, 2005. http://hdl.handle.net/11462/61.
Pełny tekst źródłaStreszczenie:
Thesis (D.Tech (Engineering Electrical)) - Central University of Technology, Free State, 2005When Thomas Edison invented his carbon filament lamp in 1879, gas shares fell overnight. A committee of inquiry was set up to examine the future possibilities of the new method of lighting, and had reached the conclusion that electric light in the home was fanciful and absurd. Today electric light burns in practically every house in the civilised world, with many great advances in the production and use of electricity and electric power supplied by various utilities. The objective of the electric utility to deliver pure sinusoidal voltage at fairly constant magnitude throughout their system is complicated by the fact that there are currently loads on the system that produce harmonic voltages, which result in distorted voltages and currents that can adversely impact on the system performance in different ways. Because the numbers of harmonic producing loads have increased over the years, it has become necessary to address their influence, when making any additions or changes to an installation. Quality of supply measurements have long been used to characterise non-linearity on the power system, and have traditionally been measured with expensive portable analysers. A potentially faster, more integrated, and more flexible solution to measure the harmonics with a Supervisory System is accomplished by this research. Any script which aspired to cover in full detail the whole field of a subject so enormous as techniques to measure the quality of electricity supply on a SCADA system, would hardly be practical in less than a few volumes. The pretensions of this research are both modest and of a more immediate value to the reader.
33
Lin, Chan-Sheng, i 林展生. "Power Quality Analysis by Wavelet Transform". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/04880971287457796195.
Pełny tekst źródłaStreszczenie:
碩士淡江大學
電機工程學系
91
The wavelet technique is proposed for the analysis of the characteristics of power quality problems. A brief theoretical background on the wavelet theory and suggestions of some applications in the area of power quality are presented. Gauss and Daubechies for wavelet transform are employed to analyze the fault transients for the development of a novel an analysis tool. The method has been tested on the analysis of various simulated disturbances of voltage waveform including harmonics, voltage flicker, momentary interruption voltage, voltage sag and voltage swell. Test results have demonstrated the practicality and advantages of the proposed method for the applications.
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Aldenlid, Jennie. "Power Quality Analysis at Falu Hospital". Thesis, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-360163.
Pełny tekst źródłaStreszczenie:
This is a master thesis performed on behalf of ABB Power Quality Center, aiming to investigate the power quality at Falu hospital. Hospitals can suffer from bad power quality both in the aspect of malfunctioning equipment, and as they can provide disturbances to the power grid. In hospitals it is essential that everything works properly, or the consequences can be fatal. The daily operations at a hospital contains a number of different electrical equipment, from ordinary computers to advanced machines for x-rays or chromatography. This type of equipment can cause disturbances in the power system and other equipment can be affected by this. Therefore, it is very important for hospitals to have good power quality. In order to investigate the power quality, a measurement study was performed at the hospital in Falun. The parameters considered in this study were supply voltage variations, voltage dips, voltage swells, rapid voltage changes, voltage unbalance, voltage harmonics and consumption of active and reactive power. To determine the quality of the power the Swedish statute EIFS 2013:1 was used as a reference for the voltage variations and the grid operator's guidelines for the power parameters. The data from the measurements were analyzed with PQSecure and Matlab. The reults showed that the hospital had no problems regarding the studied parameters of the power quality. They were approved in every case investigated in this study however there could still be improvements regarding the power factor.
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Shah, Syed K. "Power quality analysis for renewable power generation in household". Thesis, 2018. http://hdl.handle.net/1959.7/uws:51576.
Pełny tekst źródłaStreszczenie:
Power quality is becoming essential part of Power Industry. The introduction of smarter and more sensitive equipment at both grid and residential level has created performance issues that need investigation. The cost of the power losses is rising due to power quality problems. The other significant factor that is proving vital is the customer dissatisfaction. The introduction of Renewable Energy (RE) into modern grids has also created Power Quality (PQ) problems. A study is required to narrow down the factors that can cause these PQ issues. The power companies are buying electricity back from the consumer produced by these RE sources. The power produced by RE sources coming into the electrical grid needs to be monitored. The research will focus on the factors that impact PQ especially the Total Harmonic Distortion in a electrical grid powered by renewable sources. The factors impacting power quality will be studied in detail by using an simulation approach aided by an experimental set up. The simulation approach will be used to test the hypothesis that total harmonic distortion increases by changing the nature and size of the load in the electrical system. The load type used for the research will be linear and nonlinear loads. The simulation will use single and three phase electrical system. The simulation results will be analysed and discussed. The experimental setup will be used to verify the simulation result. The experiment will be conducted on different set of load to observe the impact on the total harmonic distortion in particular. The experimental result will be collected over period of time enabling the researcher to study in detail the impact of weather, temperature, and inclination of solar panels. These factors will impact the research result. The collected data will be presented for discussion.
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Yu, Chung-Mine, i 余浚銘. "Analysis and Simulation of Unified Power Quality Conditioner for Improvement of Power Quality". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/80942532090472048369.
Pełny tekst źródłaStreszczenie:
碩士中原大學
電機工程研究所
94
In industries, the non-linear loading is increasing more and more, which causes harmonic in the power system, pollutes the power system and causes the serious quality problem of power. In past, it’s common to use passive filter to reduce the harmonic effect. But this solution has some disadvantages. Recently , there are more and more companies to use Active Power Filter(APF) to improve the power quality. There are three classes of active power filter, (1) parallel active power filter, (2) series active power filter, and (3) hybrid active power filter. Parallel APF can suppress the harmonic current and compensate reactive power. Series APF can compensate the voltage distortion. Hybrid APF is a combination of passive filter and active power filter for reducing APF’s rating. We will discuss about Unified Power Qulaity Conditioner(UPQC) in this paper. It combines two back-to-back converters, and these converters share one DC-Link capacitor. In this paper, the operation theory and control of UPQC has been studied. Then, the reliability for the power quality improvement of this system is analysed by using Matlab/Simulink.
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Abraham, Amit. "Power quality analysis of variable speed drives". Thesis, 2014. http://hdl.handle.net/10539/15367.
Pełny tekst źródłaStreszczenie:
A study was conducted to evaluate the effects of harmonics generated by Variable Speed
Drives (VSDs). A VSD with a technology known as Reduced Harmonics Technology
(RHT) was considered and benchmarked against existing solutions in industry in terms
of cost and effectiveness. The RHT VSD, like the standard VSD, uses a three phase
rectifier but with significantly lower DC bus capacitor banks and an advanced motor
control processor. Simulation results reveal that the RHT VSD model produced current
harmonics of approximately 30% when compared to a standard VSD, without any
additional mitigation solutions, produced current harmonics above 100%.
The RHT VSD was also found to be less expensive than the equivalent rated standard
VSD. Laboratory experiments reveal that the input current of the RHT VSD and the
standard VSD are similar to the input current waveforms from the simulation of the RHT
VSD and the standard VSD respectively. Simulation of the DC bus capacitance and the
source impedance reveal that in a lower range of DC capacitance values (below C1 =
600μF), the size of the DC bus capacitance has more effect on the input harmonics than
the source impedance. An increase in source impedance does not reduce input harmonics.
In the above mentioned range of capacitance values, it was noted that, the DC bus
capacitance dominate the source impedance in its ability to reduce input harmonics.
When the DC capacitance was increased above C1 = 600μF, the source impedance has
more effect on the input harmonics than the size of the DC bus capacitance.
The simulation and experimental results show that there are higher order (above 13th
order) harmonic frequency components appearing at the input of the RHT VSD when
compared to a standard VSD. It is clear that there is a trade off, due to the effect of
the motor control processor, between there being reduced harmonics at the lower orders
(below 13th order) and there being an increase in harmonics at higher orders (above
13th order). It was also noted from the experiment that there is no notable difference
in the harmonic content at the outputs of the two VSDs.
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Fu, Thu-Hsun, i 傅祖勳. "Analysis and Compression of Power Quality Data". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/74808171081973423874.
Pełny tekst źródłaStreszczenie:
博士國立臺灣科技大學
電機工程系
90
In this dissertation, power quality analysis and calculation methods are investigated and instantaneous waveform data compression techniques are developed which can be applied to power quality control and improvements. Different power quantities definitions and statistics methods are used to evaluate the load characteristics of DC and AC arc furnaces. The suitable method is need for evaluating and controlling power quality in order to obtain a reasonable charging and regulating standard from the utility to its consumers, which therefore force the consumers to improve their load characteristics. Besides basic power quantities, such as active power, reactive power and apparent power, some new power definitions may be used to evaluate harmonic pollution and three-phase unbalance. The statistics method is for evaluating and displaying the characteristics of those power quantities to express the range of load variation. Since most arc furnaces are operated during off-peak period, voltage flicker is the major power quality problem. In this dissertation, we use indirect demodulation method to calculate the amount of voltage flicker, discuss the effect of frequency leakage, change the calculation window and use the calibration factor to reduce calculation error. According to the results, this method not only reduces the data points in fast Fourier transform calculation, but also increases accuracy efficiently. For the purpose of recording and storing power quality measured data, we also use wavelet transform as basis concept to develop a data compression method for reducing the storage space of instantaneous waveform recording data. We use the multi-resolution method and the reference waveform method, and compare compression effects of the threshold coding and the vector quantization coding. According to the results, the multi-resolution method provides a better compression for voltage flicker waveforms, and the reference waveform method combined with the quantization coding is suitable for harmonic distortion waveforms. Finally, we discuss the accuracy of power quantity calculation from the reconstructed data, and find that there is not much error in the fundamental power but some error in harmonic components and harmonic phase angles. Simulated test signals as well as field-measured data are used to provide practical contribution in the research of power quality.
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GOVIND, DIGAMBAR SINGH. "REACTIVE POWER COMPENSATION IN SOLAR PV SYSTEM WITH POWER QUALITY ANALYSIS". Thesis, 2020. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18074.
Pełny tekst źródłaStreszczenie:
Electricity is a basic need in all developing and developed countries, all kinds of
industries, agriculture, commercial buildings, households etc. required electricity to
function effectively and efficiently, thus electric energy is important to every country
for its development and country growth. The major sources of energy are based on
fossil fuels but they are limited, so nowadays we are moving towards renewable energy
sources like solar, wind, tidal, biogas, hydro etc. Thermal power plants are widely used
in mostly parts of the country, basically thermal power plant based on coal, however,
due to limited availability of fossil fuel and emission of greenhouse gases makes it
necessary to regulate the use of fossil fuels and develop the renewable energy sources
which are sustainable and environment friendly. Renewable energy sources like hydro,
wind and solar have become standard for electrical energy sources these days,
nowadays there are loads of experimentation work happening in the field of renewable
energy to further improve their productivity and efficiency. In the present years in all
over the world power is generated through the photovoltaic system have grown rapidly.
The grid connected PV solar systems have become popular across the globe and have
great scope to cater major portion of electrical energy demand in future. Grid connected
PV solar farm has the capability to transfer the solar energy to the grid and further
improve the power quality of the system at the point of common coupling.
The equivalent electrical model of the PV cell is studied to understand the PV
characteristics and its dependence on solar irradiation and the temperature. Design and
development of a boost converter for MPPT in the PV system are discussed and
modelled. Model of “grid connected photovoltaic solar system” using boost converter is
developed and simulation results are presented and discussed for dynamic solar
irradiation, temperature and load conditions.
This dissertation work “reactive power compensation in solar PV system with power
quality analysis”, focuses on the electrical modelling of PV cell, conventional MPPT
technique “perturb and observe” and reference current generated for the hysteresis
current control using conventional SRFT and unit template current control techniques
are studied. The simulated results of SRFT and unit template current control techniques
are compared with different environmental and load conditions taking into account.
40
吳壯為. "Analysis Technique and Software Design for Power Quality". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/16529639952967070730.
Pełny tekst źródłaStreszczenie:
碩士國立臺灣科技大學
電機工程系
89
The primary step in power quality regulation and improvement is system monitoring. Hence, it is important to establish a complete and perfect numerical analysis method . The cause of power quality pollution is extensive, such as harmonic distortions generated by non-linear load, voltage flickers resulting from the fluctuation loads, and three phase voltage unbalance, voltage sag, etc. Based on the digital signal processing technology, this thesis discusses the calculation algorithm of power quality quantities, which includes using Park’s transform to calculate basic power quantities that is active power, reactive power and complex power; estimating harmonics by average cycle method and analyzing the diversity of different demodulation methods. Furthermore, we use wavelet transform method to compress instantaneous waveform data. In order to exalt its practical application, this thesis uses not only test signals, but also field data for cross-validation. Finally, the combination of each calculation methods is used to design and develop a multi-objective Window-oriented analysis software.
41
Tsai, Kun-Cheng, i 蔡坤成. "Analysis of the spectrum for power quality signals". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/9uc8g2.
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碩士崑山科技大學
電機工程研究所
93
Because of the progress constantly of science and technology, it makes the transition from traditional industry into a high-tech industry. Therefore, this causes the rising of the power consumption, and the reliability of supply power quality is extremely important. Besides this, there are more and more problems about power quality. The bad factors which influence the power quality are quite many. They include harmonics, voltage sag, flickers, voltage swell, voltage interruption, three-phase unbalance, inrush voltage and inrush current. These bad factors may affect the normal operation of the equipment in the factory, and cause the damage of the electrical equipments, even endanger the operator security. In this thesis, besides using the Short Time Fourier Transform (STFT) and the Generalized Time-Bandwidth Product (GTBP) optimal STFT, the Modified STFT method to improve the shortcoming of the two above methods is proposed. The simulation and discussion of many kinds of power quality signals can demonstrate that the proposed method has better accuracy than other methods.
42
Yang, Ming-Chao, i 楊銘超. "Power Quality Measurements and Analysis for Bulk Carrier". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/18057115944698559225.
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碩士國立高雄海洋科技大學
輪機工程研究所
97
A high level of electric supply quality in ships requires not only premium and reliable power generators but also proper system controls. To realistically understand effects of power control schemes on electric power quality (PQ) on ships, a PQ recorder is used in this thesis to record the electric PQ measurements in two bulk carriers with semiautomatic and automatic power schemes. The possible PQ phenomena existing in ships and their international regulation standards are introduced and the analysis method used is also described. Through thoroughly analyzing the PQ measurements, the realistic condition for the supply quality can be clearly understood. Study results can provide engineers useful information to assist them in determining proper PQ mitigation equipment or operation strategy.
43
Liu, Jun-Qin, i 劉俊欽. "Analysis and Design of Unified Power Quality Conditioners". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/10160007078533326802.
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碩士國立清華大學
電機工程學系
96
Electric power quality is one of the most important indicators of power distribution systems. Since the causes of power quality problems are generally complex and difficult to detect, applications of power electronics in power transmission and distribution systems become a new trend in power engineering practice. Unified Power Quality Conditioner (UPQC) is a new power electronic equipment with excellent performance, which can synthetically compensate familiar voltage and current quality problems of power system. However, there’s no control method which is very suitable for UPQC. Among all existing power electronics apparatus, the Unified Power Quality Conditioner (UPQC) seems to be the most advanced and effective way for power quality enhancement. In this thesis, we will focus on the UPQC. Generally speaking, the UPQC and UPFC (Unified Power Flow Controller) have a power circuit the same which is based on series and shunt power converters that share a single DC link. The shunt controller is implemented for load current compensations under harmonic distortion conditions while the series controller is designed for voltage sourced compensations. By applying the (SRF) theory, an improved UPQC control configuration will be developed in this thesis with the following new features: (1) a voltage sag/swell compensator is implemented in the series controller for dynamical voltage restoring, and (2) a reactive power compensation scheme is developed for the shunt controller with considering power ratings of the shunt converter. Practical considerations about UPQC modules and parameters settings are also discussed in details. The proposed control configuration has been validated under the PSCAD simulation environments. Simulation results on various operating conditions have been performed to verify the effectiveness of the proposed control configuration.
44
Huang, Yi-Ming, i 黃奕鳴. "Embedded Lifting Wavelet Transform Power Quality Analysis System". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/30826684833458698035.
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碩士國立彰化師範大學
電機工程學系
101
With the rapid development of science and technology, whether industry or general users, they used the appliances and equipment that are more sophisticated. Requirements for power quality tend to be more sensitive, especially industrial plant equipment systems and generator more twenty-four hours of uninterrupted operation. Therefore, the power quality becomes power companies, semiconductors and sophisticated industrial plants subject of major concern. Power quality disturbance events monitoring system is more important. This paper aimed at the general power quality events and wind turbine output voltage and current. An analysis of the general common method is discrete wavelet transform, but the calculation amount required quite large and complex structure. It is not conducive to real-time operation. This paper uses the lifting discrete wavelet transform for the electric power quality analysis and feature extraction. Lifting scheme has characteristics of simple structure, low computational complexity and allowable in-place calculation as well as could be reconstructed. It is a more quickly and effective implementation method of wavelet transform. It can effectively reduce the amount of computation. This paper uses Altera DE0-Nano development board as our power quality monitoring system platform. And we use SOPC Builder to create Nios II system with C language to design lifting discrete wavelet transform. Then we analyze different power quality events and verify the results. To ensure the developed system is correctness in this paper, and final we complete the design of power quality analysis system.
45
Yang, Xi-Long, i 楊錫隆. "DSP Based Power Quality Analysis via Discrete Wavelet Transform". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/15625909599875816603.
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碩士國立彰化師範大學
電機工程學系
94
The wavelet theory provides an important application for signal processing. It can detect and analyze the non-stationary waveforms that often occurs in the power quality events. Currently, a number of research focus on the power quality detection by using wavelet transform. A design and implementation of a digital signal processor (DSP) based power quality analysis system is presented in this study. Discrete wavelet transform (DWT) is studied and then implemented in a DSP to detect power disturbances. The features of localization and multi-resolution capability of the wavelet theory enhance the ability of power quality analysis. The characteristic of various power quality events can be observed from the results of discrete wavelet transform. Selecting an appropriate wavelet to analyze various power quality signals is an important task. Thus how to choose mother wavelet for transforming power signals is presented first. The DWT algorithm is implemented on the DSP chip TMS320C6711. DSP-based DWT starts from sampling an external disturbance signal for power quality analysis. The accuracy and efficiency of the proposed approach are verified by various case testing. The results show that the proposed approach can detect and analyze the power quality disturbance effectively.
46
Chuang, Shih-I., i 莊士毅. "Applications of Real-Time Simulation on Power Quality Analysis". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/04032949711328396537.
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碩士國立中正大學
電機工程所
94
Because the nonlinear distorting loads are widely used in the application of industrial equipment, the simulation technique of power system becomes very important. With the advanced development of the simulation techniques, real-time simulation of the power system provides many advantages, such as the smaller size of the real-time system, computational efficiency, and low maintenance cost. This thesis presents new simulation software that allows efficient and accurate fixed-step simulation for complex power system including many power electronic switches. The proposed method accurately simulates linear system with discontinuities occurring anywhere between time steps. This new software effectively overcomes difficult fixed-step simulation case, such as multiple single time-step discontinuities encountered in the simulation of electric drive and PWM converters and is used for the simulation of power system dynamics being implemented in the Matlab/Simulaink. Finally, several simulation cases are illustrated to show the usefulness and computational efficiency with the real-time system simulation.
47
Chen, Jian Heng, i 陳建亨. "Design Power Quality Analysis IC Based on Wavelet Transform". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/36458534193779461463.
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碩士淡江大學
電機工程學系
92
nsulting engineers in recent years. End-use equipment is more sensitive to disturbances that arise both on the supplying power system and within the customer facilities. The increased concern for PQ has resulted in significant advances in monitoring equipment that can be used to characterize disturbances and PQ variations. Moreover, the analysis tools embedded in the monitoring equipment are certainly important. The analysis tools can present the PQ information as individual events (disturbance waveform), trends of statistical summaries. By analysis PQ variation characteristics, causes of the variations can be determined. This will help identify equipment that requires power conditioning and provide specifications for the protection that can developed based on the PQ variation characteristics. It is widely knows that the PQ events produce a wide range of frequency components. Previous studies on the PQ waveforms mainly use Fourier Transform. The basis function used in Fourier analysis, sine waves and cosine waves, are precisely located in frequency, but exist for all time. Although the short-time Fourier Transform (STFT) which windows the input signal over comes the time location problem to a large extent, it does not provide multiple resolution in time and frequency because the window is fixed. Wavelets, however, can be chosen with very desirable frequency and time characteristic as compared to Fourier techniques. In contrast to the STFT, which uses a single analysis window, the wavelet transform uses short windows at high frequencies and long windows at low frequencies. The aim of this work is to investigate the application of wavelets in PQ events analysis. Integrated circuit (IC) technology is the enabling technology for a whole host of innovative devices and system. ICs (chips) are much smaller and consume less power than discrete components used to implement an electronic system. They are also much earliest to design and manufacture and are more reliable than discrete system. In IC technologies, the system on a programmable chip (SOPC) solution with cost reductions and design simplicity is a compelling alternative to traditional system design techniques. In this study, the PQ analysis algorithm based on wavelet transform is implemented by the SOPC technology. As mentioned above, this research proposes an analytical method based on wavelet transform to investigate the characterization of PQ events. In this thesis five typical PQ events, voltage interruption, voltage sag, voltage swell, voltage pulse and voltage flicker are utilized to evaluate the performance of the proposed method. Then, the proposed PQ analysis algorithm is implemented by a SOPC. Finally, simulation and test results are presented to confirm the ability of the PQ analysis IC.
48
Lung, Tsai Han, i 蔡漢隆. "Analysis and Measurement of Power Quality On Wind Farms". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/70877847436516531675.
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碩士國立臺北科技大學
電機工程系碩士班
92
Wind Generator (WG) is one of the country’s aims in energy development. Because the WG is an unstable source, the characteristics fed into the rigid are different from the traditional energy sources. This thesis aims to understand characteristics and applications of WG in Taiwan, and to explore IEC 61400-21 and integrate the latest released regulation, “the technical rules of renewable energy generation connected to the Taipower transmission and distribution system,” so as to provide a clear understanding and helpful solution for the public as references. In order to understand the operation characteristics and the influences of power quality of WG, my study compares the differences of characteristics between Synchronous Generator (SG) and asynchronous Induction Generator (IG). The thesis investigates the power quality of the top three wind generators in Taiwan area, preceding a two-month measurement in the power quality. The measuring data includes wind speeds, power capacities, system voltages and system frequency, the total currents of WG, the total distortion of harmonic currents, voltage fluctuation, voltage flicker and the three phases voltage negative-sequence voltage and zero-sequence voltage. Furthermore, the study analyzes and compares the real measurement results of the power quality between Induction Generator and Synchronous Generator. Finally, the conclusion of the study points out a system impact analysis on WG in order to provide as one of the references for Taipower system to add or equip WG in the future.
49
Wang, An-Chih, i 王安志. "Measurement and Analysis of Power Quality in Kaohsiung Area". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/72161475462525279032.
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碩士國立中山大學
電機工程學系研究所
91
In the past years, due to the rapid growth of high-tech industries, the power supply requirements are becoming much stricter. Many of sensitive equipments are often affected by various power quality (PQ) problems to malfunction, as a result, the customer complaints. Before the mitigations of PQ are decided, the PQ monitoring system should be setup to find out the causes of PQ problems. The aim of this thesis is to establish a PQ monitoring system to investigate the quality of power in Kaohsiung Area for different types of customers. The recorded data not only are used to calculate different PQ of various parameters indices such as harmonics, voltage unbalance, voltage flicker, and voltage events, but also to confer the levels of typical devices affected by voltage sag events. The related measuring techniques include selection of monitoring sites, threshold settings of recorder, the ability to capture events, and the data collection and analysis are included in this thesis. Analysis results are compared to PQ standards to understand the actual quality of power delivery in the Kaohsiung Area.
50
Yu-Po, Tseng, i 曾郁普. "Power Quality Analysis and Design Software for Distribution Systems". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/56211566324184053507.
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