Examensarbetet går ut på att utreda hur störningsnivån varierar över tid i elnätet samt ett antal olika ställen inom Norrlands universitetssjukhus, Umeå. Elektrisk fältmätning ingick också i arbetet för att undersöka om det fanns ett samband mellan det elektriska fältet och övertoner i sjukhusets elnät. Examensarbetet presenterar grundläggande teori om elnät, elkvalité och parametrar som beskriver elkvalité, t.ex. övertoner, flimmer och transienter. Förslag på hur övertonshalten kan reducera tas även upp. Mätningarna av elkvalitets parametrar genomfördes med ett antal mätinstrument. Insamlat mätdata analyserades i några olika programvaror. Undersökningen visar att övertonshalten varierade mycket över dygnet och var högst på intensivvårdsavdelning där maxvärdet på spänningsövertonshalten THDu var 4,01%. Ström, spänning och frekvens var inte stabila, dvs. transienter och flimmer har uppstått under mätningen. Analysen av mätdata visar att den totala spänningsövertonshalten THDu var under 5% och inte överskred gränsvärdet 8% som anges i standarden SS-EN 50 160. / The aim of the thesis was to examine whether the level of disturbance in the power grid vary between different types of care environment over time at University Hospital of Umeå. Electric field measurement was also included in the thesis to investigate whether there was a connection between the electric field and harmonics in the hospital’s power grid. The thesis presents basic theory about power grid, power quality and parameters which describe power quality, such as, harmonics, flicker and transients. Suggestions on how to reduce the harmonic content will also be discussed. The measurements of the power quality parameters were performed by using different measuring equipment. The data were analyzed using different software. The study shows that the harmonic content often varied and was highest in intensive care unit, where the maximum value of the harmonic voltage distortion THD was 4,01%. The measurement shows that current, voltage and frequency were not stable, that is transients and flicker occurred several times during the measurement. The analysis of the data shows that the harmonic voltage distortion THDu was below 5% and never above the limit 8% which is specified in the standard SS-EN 50 160.

A study of the use of solution adaptive grid (SAG) method for simulations of incompressible flows is carried out in this work. Both laminar and turbulent types of flows are chosen. Investigation on laminar flow simulation starts with mesh adaptation criteria that are based on strong changes of some selected flow parameters; pressure and velocity components. Three most common laminar types of flows are studied; flow in a circular pipe, flow in a channel with sudden expansion and flow in a cavity with a moving lid. It is found that with the use of SAG, a reduction in both computational grid nodes and CPU time can be obtained when compared to those of fixed grid while satisfactory solutions are also achievable. Nevertheless, the refinement criteria setup procedure reveals inconveniences and requirement for several judgments that have to be defined ‘ad hoc’. This hence, makes the refinement criteria dubious for real engineering applications. For the study of turbulent flows with large eddy simulation (LES) and implicit filtering, examination of literature reveals that the lack of connections between the filter width and a physical scale has made LES somewhat unclosed, i.e. in a physical sense. In addition, it is known that numerical and modelling errors are always combined and it is difficult to study each of them separately making the total error magnitude difficult to control. Since both error types are characterised by the grid size, LES users very often find cases where a finer mesh no longer provides better accuracy. An attempt to address this ‘physical’ enclosure property of LES and its complication to implement/setup in FLUENT begins with the construction of a new refinement variable as a function of the Taylor scale. Then a new SAG algorithm is formed. The requirement to satisfy a condition of the selected subgrid scale (SAG) model, the Smagorinsky model, is taken into consideration to minimize the modeling error. The construction of a new refinement algorithm is also aimed to be the key to studying the interaction between the two types of error and could lead to the means of controlling their total magnitude. The validation in terms of its effectiveness, efficiency and reliability of the algorithm are made based on several criteria corresponding to suitability for practical applications. This includes the simplicity to setup/employ, computational affordability, and the accuracy level. For this, two different turbulent flow types that represent different commonly found turbulent phenomena are chosen; plane free jet and the flow over a circular cylinder. The simulations of the two cases were carried out in two dimensions. It is found that there are two key factors that strongly determine the success of the algorithm. The first factor is the Taylor scale definition, with literature only available for the turbulent plane jet study, for which good level of accuracy is expected. Unfortunately, this is not true for the flow over a circular cylinder, indicating a need for further analytical work. The second encountered difficulty results from limited access to software codes, which makes it impossible to implement the proposed scheme. As a result, the algorithm formulation needs be modified with carful judgment. Nevertheless, overall results are in reasonably good agreement with their corresponding experimental data.

The rise of business-oriented and commercial applications for Grid computing environments has recently gathered pace. Grid computing traditionally has been linked with scientific environments, where heterogeneous resources provided by Grid systems and infrastructures were employed for carrying out computationally-intensive and data-intensive scientific experiments or applications that may have not been possible before. The natural progression is that business-oriented applications will look to build on this success and utilise the large number of heterogeneous Grid resources including computational resources such as CPUs and memory and storage resources such as disk space, potentially available. The success of introducing these applications into the mainstream is directly related to whether service providers can deliver a level of Quality of Service (QoS) to a consumer and the ability of the consumer to request high-level QoS such as the numbers of CPUs required or the RAM required. QoS refers to the guidelines and requirements requested by a user/consumer from the service providers and resources. The communication and agreement establishment processes between user and provider must be defined clearly to accommodate a new type of user where knowledge of the underlying infrastructure cannot be assumed. QoS parameters have generally been defined at the Grid resource level using low level definitions. This tailors to specific applications and models related to scientific domains where brokering, scheduling and QoS delivery is designed for specific applications within specific domains. This thesis presents a flexible model for high-level QoS requests. Business Grid Quality of Service (BGQoS) is introduced for business-oriented and commercial Grid applications which may wish to make use of the resources made available by Grid system environments. BGQoS allows GRCs (Grid Resource Consumers) to specify varying types of high-level QoS requirements which are delivered via querying up-to-date resource information, matchmaking and monitoring operations. Moreover, we present dynamically calculated metrics for measuring QoS such as reliability, increasing the accuracy of meeting the GRC’s requirements. On the other hand GRPs (Grid Resource Provider) are also capable of advertising their resources, their capabilities, their usage policies and availability both locally and globally. This leads to a flexible model that could be carried across domains without altering the core operations and which could easily be expanded in order to accommodate different types of GRC, resources and applications.

Job quality is important: there is a substantial evidence base which illustrates the potential risks of poor quality work. These arise from the occurrence of accidents and disease due to unmanaged hazards, as well as from psychosocial factors such as poor pay and security, shift working or the combination of low control and high demands. There is also a body of evidence which demonstrates a positive impact from good quality work, with contributions to longevity, improved health and happiness, and business success. Despite this recognition of the importance of job quality, there is a lack of agreement around exactly what it is: particularly when trying to define it as a single construct. This research aimed to address this insufficiency by exploring the concept of the good job, and seeking to define job quality from an ergonomics perspective. This approach encourages a broad outlook, taking account of the physical and psychosocial aspects of work, the interactions between them, and the impact of individual variation. A theoretical model is presented to summarise the concept of job quality based on these considerations: this was applied to a study of three bus companies using both a quantitative survey tool and qualitative methods. In developing the model, an initial study was undertaken using repertory grid interviews to explore notions of work and job quality, and to identify the most important areas for further investigation. Interviews were conducted with individuals (n=18) who were employed in a wide range of jobs, and varied substantially in their priorities and preferences. Job content and relationships were often identified as more important than pay levels; but there was also evidence of compromise, where interviewees had prioritised jobs which met their practical needs. Also, individuals perceived a good job differently from one which was good for their health, and overall did not consider good health to be an essential outcome of a good job. Two subsequent studies were undertaken with a focus on jobs commonly done by those with low formal education, who may have more to gain from improved job quality. Semi-structured interviews were carried out firstly with cleaners and manufacturing employees (n=30) and then with bus drivers (n=80). A number of job features such as safety and job/employment security were found to be important for almost all interviewees, and thus were identified as core features of a good job. Other factors such as autonomy and preferences for particular working patterns were more variable, highlighting the importance of job-employee fit. The theoretical model of job quality constructed was based on these findings and the literature. The model was applied in a qualitative study of bus and coach drivers in three companies to assess whether this was a good job, whether it could be a good job, and what the barriers to this might be. In two of the companies bus driving was found to be a poor job, with low pay and inadequate health and safety management. In the third company it was better but there were still challenges: particularly time pressures, low physical activity, and varied and unsociable working patterns. It was identified that some of the barriers to good job quality for bus drivers and potentially in jobs more generally are difficult to address as they are intrinsic to the job. The best solution to these difficulties is to ensure a good fit between job and employee. Other barriers were identified which appeared to be financial, such as low pay in the two smaller companies, but they could also reflect cultural factors within the organisation or within wider society. A final study considered the measurement of job quality, in the light of the importance and extent of individual variation highlighted throughout the research. The DGB-Index (Deutscher Gewerkschaftsbund Index), a questionnaire tool designed and used in Germany which specifically accounts for this, was used in the same three bus companies (n=423). The results were compared with those from the qualitative study and reached similar conclusions, thus confirming the utility of the DGB-Index for job measurement and comparison when translated into English. The research demonstrated that it is possible to define and measure job quality and to compare it between organisations. The model of a good job constructed to facilitate this differs from those found in the literature: it takes into account the variation between individuals and the fact that they construe good jobs in different ways. Thus it highlights the importance to job quality of a good fit between job and individual in addition to the need for work to be good in terms of the more universal features such as job security, safety and adequate pay.

As the number of autonomous decision-making entities in the electricity grid increases, it is necessary to develop (1) new decision-making capabilities embedded within the grid's control and management, and (2) new grid architecture models ensuring that both individual and system objectives are met. This work develops (1) new decision-making mechanisms enabling residential energy users and electricity providers to interact through the use of dynamic price signals, and (2) policy recommendations to facilitate the emergence of shared architecture models describing the future state of the electricity grid. In the first part, two optimization models that capture the emerging flexible consumption, storage, and generation capabilities of residential end-users are formulated. An economic dispatch model that explicitly accounts for end-users' internal dynamics is proposed. A non-iterative pricing algorithm using convex and inverse linear programming is developed to induce autonomous residential end-users to behave cooperatively and minimize the provider's generation costs. In the second part, several factors that make the development of grid architecture models necessary from a public policy standpoint are identified and discussed. The grid architecture problem is rigorously framed as both a market failure legitimizing government intervention, and a meta-problem requiring the development of non-conventional methods of solution. A policy approach drawing on the theoretical concepts of broker, boundary object and boundary organization is proposed.

Renewable and green energy development is vigorously supported by most countries to suppress the continuously increasing greenhouse gas (GHG) emissions. However, as the total renewable capacity expands, the growth rate of emissions is not effectively restrained. An unforeseen factor contributing to this growth is the regulation service, which aims to mitigate power frequency deviations caused by the intermittent renewable power generation and unbalanced power supply and demand. Regulation services, normally issued by supply-side balancing authorities, leads to inefficient operations of regulating generators, thus directly contributing to the emissions growth. Therefore, it is urged to find solutions that can stabilize the power frequency with an increased energy using efficiency. Demand response (DR) is an ideal candidate to solve this problem. The current smart grid infrastructure enables a high penetration of smart residential electric loads, including heating, ventilation, and air conditioning systems (HVACs), air conditioners (A/Cs), electric water heaters (EWHs), and plug-in hybrid electric vehicles (PHEVs). Beyond simply drawing power from the grid for local electric demand, those loads can also adjust their power consumption patterns by responding to the control signals sent to them. It has been proved that, if appropriately aggregated and controlled, power consumption of demand-side residential loads possesses a huge potential for providing regulation services. The research of DR is pivotal from the the application perspective due to the efficient usage of renewable energy generation and the high power quality. However, many problems remain open in this area due to the load heterogeneity, device physical constraints, and computational and communication restrictions. In order to move one step further toward industry applications, this PhD thesis is concerned with two cruxes in DR program design: Aggregation Modeling and Control; it deals with two main types of terminal loads: Thermostatically Controlled Appliances (TCAs) (Chapters 2-4) and PHEVs (Chapter 5). This thesis proceeds with Chapter 1 by reviewing the state-of-the-art of DR. Then in Chapter 2, the focus is put on modeling and control of TCAs for secondary frequency control. In order to explicitly describe local TCA dynamics and to provide the aggregator a clear global view, TCAs are aggregated by directly stacking their individual dynamics. Terminal TCAs are assumed in a general case that an arbitrary number of TCAs are equipped with varying frequency drives (VFDs). A centralized model predictive control (MPC) scheme is firstly constructed. In the design, to tackle the TCA lockout effect and to facilitate the MPC scheme, a novel approach for converting time-integrated interdependent logic constraints into inequality constraints are proposed. Since a centralized MPC scheme may introduce non-trivial computational load by using this aggregation model, especially when the number of TCAs increases, a distributed MPC (DMPC) scheme is proposed. This DMPC scheme is validated through a more practical case study that all TCAs are subject to pure ON/OFF control. Chapter 3 targets on aggregation modeling and control of TCAs for the provision of primary frequency control. To efficiently reduce the computational load to facilitate the primary frequency control, the explicit monitoring of terminal TCAs must be compromised. To this end, a 2-D population-based model is proposed, in which TCAs are clustered into state bins according to their temperature information and running status. Within the proposed aggregation framework, individual TCA dynamics' evolutions develop into TCA population migration probabilities, thus the computational load of the centralized controller is dramatically reduced. Based on this model, a centralized MPC scheme is proposed for the primary frequency control. The previously proposed population-based model provides a promising direction for the centralized control. However, in traditional population-based model, TCA lockout effect can only be considered when implementing the control signals. This will cause a mismatch between the nominal control signals and the actually implemented ones. To conquer this, in Chapter 4, an improved population-based model is studied to explicitly formulate the TCA lockout effect in the aggregation model. A DMPC scheme is firstly constructed based on this model. Furthermore, since the predictions of regulation signals may not be available or they may include severe disturbances, a control scheme that does not require future regulation signals is urged. To this end, an optimal control scheme, in which a novel penalty is included to maximize the regulation capability, is proposed to facilitate the most practical scenario. Another type of terminal loads that has a huge potential in providing grid services is PHEV. At this point, Chapter 5 presents the aggregation and charging control of heterogeneous PHEVs for the provision of DR. In contrast to using battery state-of-charge (SOC) solely as the system state, a new aggregation model is proposed by introducing a novel concept, i.e., charging requirement index. This index combines the SOC with drivers' specified charging requirements, thus inherently providing the aggregation model with richer information. A centralized MPC scheme is proposed based on this novel model. Both of the model and controller are validated through an overnight valley-filling case study. Finally, the conclusions of the thesis are summarized and future research topics are presented. / Graduate / 0537 / 0544 / 0548 / mingxiliu419@gmail.com

Thesis (PhD)--Stellenbosch University, 2011. / Technology is a critical component in modern society. Management of Technology (MOT) should be a major focus of management studies. At present the status of MOT is much less than it should be. Part of the reason is that there is little consensus about the body of knowledge for MOT. This can be traced down to as far as an inadequate consensus about the very nature of technology itself. There is a need for a simple and elegant conceptual foundation. There is a need for an accepted paradigm to govern MOT. The paradigm discourse initiated by Thomas Kuhn allows for a comprehensive frame of reference about theory contestation and about the attributes required from a contesting theory to achieve the ultimate status of a paradigm. In order to help create a coherent and streamlined conceptual foundation for MOT, this research evaluates the functionality grid as a paradigm. To realise this goal, this study first assesses the functionality grid’s compliance with the theoretical requirements of a paradigm, and secondly its compliance with the empirical requirements of a paradigm. The theoretical test uses a newly created format, the paradigm template, to establish the necessary criteria. The functionality grid is then subjected to a critical review using the said criteria. It is found that it meets the requirements of a valid paradigm. For measurement of empirical requirements, Kuhn’s own criteria are used. This second part of the study involves three practical exercises to examine the practical descriptive power of the functionality grid, and its ability to help first with the formation of a technology attuned mindset of participants, second with the improvement in technological knowledge and third with an increase in the technological literacy of participants. The outcomes of these tests are positive as well. The dissertation concludes that the functionality grid would be a viable paradigm to serve as a guide for the further development of MOT. The functionality grid becomes confirmed as a paradigm for MOT, because it contains all the attributes to serve as a coherent and streamlined conceptual structure for this discipline. Given this outcome, it is recommended that more effort be invested to understand, promote and popularise the functionality grid; and the various analytical frameworks derived from it. It is recommended that it becomes an explicit part of the book of knowledge for MOT and that it constitutes the basis for an educational curriculum to be shared by every MOT professional and student.

The EU has concluded that it needs a fully functioning and integrated internal electricity market to face the challenges of integrating renewable energy sources into the electricity grid. The European Commission has created guidelines for what the legislation is supposed to contain to create such a market. The so called grid codes are today around ten codes which successively are being implemented in national legislation for all member states. They regard connection-, marketand operation of the electricity grid and consists of several legal requirements for all member states. This study is divided in three parts. In the first part challenges with more renewable energy sources are described and the technical strategies that are suitable to solve those challenges. The second part describes an analysis of the connection- and operational codes on behalf of Ellevio, a distribution system operator in Sweden. They are interested in how the new legislation will affect their work and which new costs that will appear. The third part contains an overall study about the German electricity system since they have a lot of renewable energy sources in their production. The purpose was to see how they have handled challenges within their grid and their view on the new legislation. The overall result in this study was that the grid codes will change the role for Ellevio, which in the following years will have to handle higher information flow between grid users and Svenska kraftnät, which is the transmission system operator in Sweden. An another result was that the technical strategies are included in the legal requirements of the codes and that the legal requirements have been influenced to a great extent by the current German legislation.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Natural draught wet-cooling tower rain zone performance can be significantly enhanced by reducing the mean drop size in the rain zone with the installation of specially designed grids below the cooling tower fill. Drops enter the rain zone in the form of a polydisperse drop distribution, dripping from below the cooling tower fill, comprising relatively large drops. In order to design and optimize a grid for breaking up these drops, the mechanisms of drop break-up after impingement on the grid surface, referred to as splashing, straddling and dripping, need to be clearly understood. Two of these mechanisms, splashing and straddling, are therefore investigated experimentally using high speed video cameras to measure initial drop sizes, mass fractions and drop size distributions after impingement on different horizontal slats covered with a thin layer of water. The following parameters are varied independently for these experiments: drop fall distance, initial drop size, slat width and the water film thickness on the slats. Dripping from below the grid, is investigated theoretically. The effect of drop interaction on the drop size distribution in the rain zone is also investigated experimentally by measuring the drop distributions at the top and bottom of rain zones with a height of approximately 7.05 m to 7.65 m for different inlet distributions. The experimental drop break-up data, numerically obtained splash drop trajectory data and drop interaction data found in literature are used to develop a theoretical model of a purely counter flow cooling tower rain zone with and without installed grids. The model is compared to experimental data and theoretical data from literature and the predicted thermal and dynamic behaviour of the rain zone are generally found to be in good agreement with these results. Ultimately, this model is used for the optimization of the grid layout in terms of variables such as distance between the grid and the fill, slat width, slat spacing and slat height. It is found that the best drop break-up is achieved for grids comprising narrower slats with lower grid porosities as opposed to grids comprising wider slats. For the determined optimal grid layout it is found that a significant improvement in cooling tower performance can be achieved. / AFRIKAANSE OPSOMMING: Nat-koeltoringreënsonevermoë kan aansienlik verhoog word deur die druppelgrootte in hierdie gebied te verklein deur roosters, wat spesifiek vir hierdie doel ontwerp is, onder die pakkingsmateriaal te installeer. Die inlaatdruppelverdeling aan die bokant van die reënsone bestaan uit ‘n verdeling van relatief groot druppels wat drip van die onderkant van die pakkingsmateriaal. Ten einde ‘n rooster te ontwerp en te optimeer wat hierdie druppels kan opbreek moet die meganismes van druppelopbreking, bekend as spatting, vurking en drip goed verstaan word. Spatting en vurking is om hierdie rede eksperimenteel ondersoek, met behulp van hoëspoed videokameras. Die volgende veranderlikes is onafhanklik verander tydens hierdie eksperimente: valafstand van die druppel, aanvanklike druppelgrootte, latwydte en die dikte van die lagie water bo-op die lat. Die dripmeganisme aan die onderkant van die rooster is slegs teoreties ondersoek. Die effek wat druppelinteraksie in die reënsone het op die druppelgrootte is ondersoek deur die druppelgroottes aan die bo- en onderkant van ‘n 7.05 m tot 7.65 m reënsone te meet vir verskillende druppelinlaatverdelings. Die eksperimentele druppeldata, sowel as numeries berekende data wat die snelheid en trajek van spatdruppels beskryf, tesame met data vir druppelinteraksies wat uit die literatuur verkry is word gebruik om ‘n teoretiese model te ontwikkel vir ‘n suiwer teenvloei koeltoringreënsone met en sonder roosters. Hierdie model word vergelyk met eksperimentele data en data wat uit die literatuur verkry is en daar is gevind dat daar oor die algemeen ‘n goeie ooreenstemming is tussen die voorspelde en gemete termiese en dinamiese gedrag van die reënsone. Uiteindelik word die model gebruik vir die optimering van die rooster in terme van die volgende veranderlikes: afstand tussen rooster en pakkingsmateriaal, latwydte, latspasiëring en lathoogte. Daar word gevind dat beter druppelopbreking verkry word deur gebruik te maak van smaller latte en ‘n laer roosterporeusiteit. Daar is gevind dat die bepaalde optimale roosteruitleg in die reënsone van ‘n koeltoring ‘n wesenlike verbetering in koeltoringvermoë tot gevolg kan hê.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The electromagnetic and mechanical design aspects of optimally designed doublesided rotor radial flux permanent magnet wind generators with non-overlap aircored (iron-less) stator windings are analysed in this thesis. The wind generator is implemented in a battery charging system for use in rural settlements and farms. The optimal generator and system design is based on an accurate analytical model and is confirmed with finite element analysis. It is shown, amongst other things, that the electromagnetic design and surprisingly not the mechanical design, determines the rotor yoke dimensions and, hence, largely the mass and cost of the generator. Alternative battery charging systems are also considered and discussed. / AFRIKAANSE OPSOMMING: Die elektromagnetiese en meganiese ontwerp aspekte van optimaal ontwerpte dubbel-kant rotor radiale vloed permanente magneet windgenerators met nieoorvleuelende lug kern (sonder yster) statorwindings word in hierdie tesis ontleed. Die windgenerator word geplaas in 'n battery-laai stelsel vir gebruik in landelike nedersettings en plase. Die optimale generator en die stelsel ontwerp is gegrond op 'n akkurate analitiese model en is bevestig met eindige element analise. Daar word onder andere getoon dat die elektromagnetiese ontwerp, en nie die meganiese ontwerp, die rotor juk dimensies en dus grootliks die massa en die koste van die generator, bepaal. Alternatiewe battery-laai stelsels word ook oorweeg en bespreek.