Performance control of distributed generation using digital estimation of signal parameters

The Queensland University of Technology (QUT) allows the presentation of a thesis for the Degree of Doctor of Philosophy in the format of published or submitted papers, where such papers have been published, accepted or submitted during the period of candidature. This thesis is composed of seven published/submitted papers, of which one has been published, three accepted for publication and the other three are under review. This project is financially supported by an Australian Research Council (ARC) Discovery Grant with the aim of proposing strategies for the performance control of Distributed Generation (DG) system with digital estimation of power system signal parameters. Distributed Generation (DG) has been recently introduced as a new concept for the generation of power and the enhancement of conventionally produced electricity. Global warming issue calls for renewable energy resources in electricity production. Distributed generation based on solar energy (photovoltaic and solar thermal), wind, biomass, mini-hydro along with use of fuel cell and micro turbine will gain substantial momentum in the near future. Technically, DG can be a viable solution for the issue of the integration of renewable or non-conventional energy resources. Basically, DG sources can be connected to local power system through power electronic devices, i.e. inverters or ac-ac converters. The interconnection of DG systems to power system as a compensator or a power source with high quality performance is the main aim of this study. Source and load unbalance, load non-linearity, interharmonic distortion, supply voltage distortion, distortion at the point of common coupling in weak source cases, source current power factor, and synchronism of generated currents or voltages are the issues of concern. The interconnection of DG sources shall be carried out by using power electronics switching devices that inject high frequency components rather than the desired current. Also, noise and harmonic distortions can impact the performance of the control strategies. To be able to mitigate the negative effect of high frequency and harmonic as well as noise distortion to achieve satisfactory performance of DG systems, new methods of signal parameter estimation have been proposed in this thesis. These methods are based on processing the digital samples of power system signals. Thus, proposing advanced techniques for the digital estimation of signal parameters and methods for the generation of DG reference currents using the estimates provided is the targeted scope of this thesis. An introduction to this research – including a description of the research problem, the literature review and an account of the research progress linking the research papers – is presented in Chapter 1. One of the main parameters of a power system signal is its frequency. Phasor Measurement (PM) technique is one of the renowned and advanced techniques used for the estimation of power system frequency. Chapter 2 focuses on an in-depth analysis conducted on the PM technique to reveal its strengths and drawbacks. The analysis will be followed by a new technique proposed to enhance the speed of the PM technique while the input signal is free of even-order harmonics. The other techniques proposed in this thesis as the novel ones will be compared with the PM technique comprehensively studied in Chapter 2. An algorithm based on the concept of Kalman filtering is proposed in Chapter 3. The algorithm is intended to estimate signal parameters like amplitude, frequency and phase angle in the online mode. The Kalman filter is modified to operate on the output signal of a Finite Impulse Response (FIR) filter designed by a plain summation. The frequency estimation unit is independent from the Kalman filter and uses the samples refined by the FIR filter. The frequency estimated is given to the Kalman filter to be used in building the transition matrices. The initial settings for the modified Kalman filter are obtained through a trial and error exercise. Another algorithm again based on the concept of Kalman filtering is proposed in Chapter 4 for the estimation of signal parameters. The Kalman filter is also modified to operate on the output signal of the same FIR filter explained above. Nevertheless, the frequency estimation unit, unlike the one proposed in Chapter 3, is not segregated and it interacts with the Kalman filter. The frequency estimated is given to the Kalman filter and other parameters such as the amplitudes and phase angles estimated by the Kalman filter is taken to the frequency estimation unit. Chapter 5 proposes another algorithm based on the concept of Kalman filtering. This time, the state parameters are obtained through matrix arrangements where the noise level is reduced on the sample vector. The purified state vector is used to obtain a new measurement vector for a basic Kalman filter applied. The Kalman filter used has similar structure to a basic Kalman filter except the initial settings are computed through an extensive math-work with regards to the matrix arrangement utilized. Chapter 6 proposes another algorithm based on the concept of Kalman filtering similar to that of Chapter 3. However, this time the initial settings required for the better performance of the modified Kalman filter are calculated instead of being guessed by trial and error exercises. The simulations results for the parameters of signal estimated are enhanced due to the correct settings applied. Moreover, an enhanced Least Error Square (LES) technique is proposed to take on the estimation when a critical transient is detected in the input signal. In fact, some large, sudden changes in the parameters of the signal at these critical transients are not very well tracked by Kalman filtering. However, the proposed LES technique is found to be much faster in tracking these changes. Therefore, an appropriate combination of the LES and modified Kalman filtering is proposed in Chapter 6. Also, this time the ability of the proposed algorithm is verified on the real data obtained from a prototype test object. Chapter 7 proposes the other algorithm based on the concept of Kalman filtering similar to those of Chapter 3 and 6. However, this time an optimal digital filter is designed instead of the simple summation FIR filter. New initial settings for the modified Kalman filter are calculated based on the coefficients of the digital filter applied. Also, the ability of the proposed algorithm is verified on the real data obtained from a prototype test object. Chapter 8 uses the estimation algorithm proposed in Chapter 7 for the interconnection scheme of a DG to power network. Robust estimates of the signal amplitudes and phase angles obtained by the estimation approach are used in the reference generation of the compensation scheme. Several simulation tests provided in this chapter show that the proposed scheme can very well handle the source and load unbalance, load non-linearity, interharmonic distortion, supply voltage distortion, and synchronism of generated currents or voltages. The purposed compensation scheme also prevents distortion in voltage at the point of common coupling in weak source cases, balances the source currents, and makes the supply side power factor a desired value.

Digital economy future directions

Advances in information and communication technologies have brought about an information revolution, leading to fundamental changes in the way information is collected or generated, shared and distributed. The internet and digital technologies are re-shaping research, innovation and creativity. Economic research has highlighted the importance of information flows and the availability of information for access and re-use. Information is crucial to the efficiency of markets and enhanced information flows promote creativity, innovation and productivity. There is a rapidly expanding body of literature which supports the economic and social benefits of enabling access to and re-use of public sector information.1 (Note that a substantial research project associated with QUT’s Intellectual Property: Knowledge, Culture and Economy (IPKCE) Research Program is engaged in a comprehensive study and analysis of the literature on the economics of access to public sector information.)

On the robustness and security of digital image watermarking

In most of the digital image watermarking schemes, it becomes a common practice to address security in terms of robustness, which is basically a norm in cryptography. Such consideration in developing and evaluation of a watermarking scheme may severely affect the performance and render the scheme ultimately unusable. This paper provides an explicit theoretical analysis towards watermarking security and robustness in figuring out the exact problem status from the literature. With the necessary hypotheses and analyses from technical perspective, we demonstrate the fundamental realization of the problem. Finally, some necessary recommendations are made for complete assessment of watermarking security and robustness.

Strengthening the role of the adult education sector in training workers for the digital content industries in Australia and Singapore

In 2009, QUT’s Office of Research and the Institute for Adult Learning Singapore funded a six-month pilot project that represented the first stage of a larger international comparative study. The study is the first of its kind to investigate to what extent and how digital content workers’ learning needs are being met by adult education and training in Australia and Singapore. The pilot project involved consolidating key theoretical literature, studies, policies, programs and statistical data relevant to the digital content industries in Australia and Singapore. This had not been done before, and represented new knowledge generation. Digital content workers include professionals within and beyond the creative industries as follows: Visual effects and animation (including virtual reality and 3D products); Interactive multimedia (e.g. websites, CD-ROMs) and software development; Computer and online games; and Digital film & TV production and film & TV post-production. In the last decade, the digital content industries have been recognised as an industry sector of strong and increasing significance. The project compared Australia and Singapore on aspects of the digital content industries’ labour market, skill requirements, human capital challenges, the role of adult education in building a workforce for the digital content industries, and innovation policies. The consolidated report generated from the project formed the basis of the proposal for an ARC Linkage Project application submitted in the May 2010 round.

Re-engaging marginalized youth through digital music production: performance, audience and evaluation

This paper presents two case studies of marginalised youth experimenting with digital music production in flexible education settings. The cases were drawn from a three-year study of alternative assessment in flexible learning centres that enrol 650+ students who have left formal schooling in Queensland, Australia. The cases are framed in reference to the literature on cultural studies approaches to education and the digital arts. Each case describes the student’s histories, cultural background and experiences, music productions, evidence of learning and re-engagement with education. Findings document how digital music production can re-engage and extend participation among students who have left formal education. They do so by theorising the online judgements and blog comments about the digital music production as a social field of exchange. It also raises critical questions about the adequacy of current approaches to evaluating and accounting for the learning and development of such youth, especially where this has occurred through creative arts and digital production.

Chinese online literature : creative consumers and evolving business models

Purpose – The internet is transforming possibilities for creative interaction, experimentation and cultural consumption in China and raising important questions about the role that “publishers” might play in an open and networked digital world. The purpose of this paper is to consider the role that copyright is playing in the growth of a publishing industry that is being “born digital”. Design/methodology/approach – The paper approaches online literature as an example of a creative industry that is generating value for a wider creative economy through its social network market functions. It builds on the social network market definition of the creative industries proposed by Potts et al. and uses this definition to interrogate the role that copyright plays in a rapidly-evolving creative economy. Findings – The rapid growth of a market for crowd-sourced content is combining with growing commercial freedom in cultural space to produce a dynamic landscape of business model experimentation. Using the social web to engage audiences, generate content, establish popularity and build reputation and then converting those assets into profit through less networked channels appears to be a driving strategy in the expansion of wider creative industries markets in China. Originality/value – At a moment when publishing industries all over the world are struggling to come to terms with digital technology, the emergence of a rapidly-growing area of publishing that is being born digital offers important clues about the future of publishing and what social network markets might mean for the role of copyright in a digital age.

Preface to special issue on digital human modelling for vehicle design and manufacturing

The automotive industry has been the focus of digital human modeling (DHM) research and application for many years. In the highly competitive marketplace for personal transportation, the desire to improve the customer’s experience has driven extensive research in both the physical and cognitive interaction between the vehicle and its occupants. Human models provide vehicle designers with tools to view and analyze product interactions before the first prototypes are built, potentially improving the design while reducing cost and development time. The focus of DHM research and applications began with prediction and representation of static postures for purposes of driver workstation layout, including assessments of seat adjustment ranges and exterior vision. Now DHMs are used for seat design and assessment of driver reach and ingress/egress. DHMs and related simulation tools are expanding into the cognitive domain, with computational models of perception and motion, and into the dynamic domain with models of physical responses to ride and vibration. Moreover, DHMs are now widely used to analyze the ergonomics of vehicle assembly tasks. In this case, the analysis aims to determine whether workers can be expected to complete the tasks safely and with good quality. This preface provides a review of the literature to provide context for the nine new papers presented in this special issue.

Preserving the past in digital memory

The process of researching children’s literature from the past is a growing challenge as resources age and are increasingly treated as rare items, stored away within libraries and other research centres. In Australia, researchers and librarians have collaborated with the bibliographic database AustLit: The Australian Literature Resource to produce the Australian Children’s Literature Digital Resources Project (CLDR). This Project aims to address the growing demand for online access to rare children’s literature resources, and demonstrates the research potential of early Australian children’s literature by supplementing the collection with relevant critical articles. The CLDR project is designed with a specific focus and provides access to full text Australian children’s literature from European settlement to 1945. The collection demonstrates a need and desire to preserve literature treasures to prevent losing such collections in a digital age. The collection covers many themes relevant to the conference including, trauma, survival, memory, survival, hauntings, and histories. The resource provides new and exciting ways with which to research children’s literature from the past and offers a fascinating repository to scholars and professionals of ranging disciplines who are in interested in Australian children’s literature.

Nurse staffing levels and the incidence of mortality and morbidity in the adult intensive care unit : a literature review

BACKGROUND: Studies have shown that nurse staffing levels, among many other factors in the hospital setting, contribute to adverse patient outcomes. Concerns about patient safety and quality of care have resulted in numerous studies being conducted to examine the relationship between nurse staffing levels and the incidence of adverse patient events in both general wards and intensive care units. AIM: The aim of this paper is to review literature published in the previous 10 years which examines the relationship between nurse staffing levels and the incidence of mortality and morbidity in adult intensive care unit patients. METHODS: A literature search from 2002 to 2011 using the MEDLINE, Cumulative Index to Nursing and Allied Health Literature (CINAHL), PsycINFO, and Australian digital thesis databases was undertaken. The keywords used were: intensive care; critical care; staffing; nurse staffing; understaffing; nurse-patient ratios; adverse outcomes; mortality; ventilator-associated pneumonia; ventilator-acquired pneumonia; infection; length of stay; pressure ulcer/injury; unplanned extubation; medication error; readmission; myocardial infarction; and renal failure. A total of 19 articles were included in the review. Outcomes of interest are patient mortality and morbidity, particularly infection and pressure ulcers. RESULTS: Most of the studies were observational in nature with variables obtained retrospectively from large hospital databases. Nurse staffing measures and patient outcomes varied widely across the studies. While an overall statistical association between increased nurse staffing levels and decreased adverse patient outcomes was not found in this review, most studies concluded that a trend exists between increased nurse staffing levels and decreased adverse events. CONCLUSION: While an overall statistical association between increased nurse staffing levels and decreased adverse patient outcomes was not found in this review, most studies demonstrated a trend between increased nurse staffing levels and decreased adverse patient outcomes in the intensive care unit which is consistent with previous literature. While further more robust research methodologies need to be tested in order to more confidently demonstrate this association and decrease the influence of the many other confounders to patient outcomes; this would be difficult to achieve in this field of research.

The university of the digital future : a reimagining based on the learning strategies of professionals in the digital media sectors

This article explores how universities might engage more effectively with the imperative to develop students’ 21st century skills for the information society, by examining learning challenges and strategies of successful digital media professionals. The findings support a significant body of literature, which argues that legacy university structures and pedagogical approaches are not conducive to optimal professional learning in the digital age. A model of one reimagining of the university is presented, which draws upon the learning preferences of the professionals in this study, as linked with extant theory relating to informal, situated, self-determined learning, communities of practice and personal learning environments.

Ergonomic DHM systems - limitations and trends – a systematic literature review focused on the ‘future of ergonomics’

Digital Human Models (DHM) have been used for over 25 years. They have evolved from simple drawing templates, which are nowadays still used in architecture, to complex and Computer Aided Engineering (CAE) integrated design and analysis tools for various ergonomic tasks. DHM are most frequently used for applications in product design and production planning, with many successful implementations documented. DHM from other domains, as for example computer user interfaces, artificial intelligence, training and education, or the entertainment industry show that there is also an ongoing development towards a comprehensive understanding and holistic modeling of human behavior. While the development of DHM for the game sector has seen significant progress in recent years, advances of DHM in the area of ergonomics have been comparatively modest. As a consequence, we need to question if current DHM systems are fit for the design of future mobile work systems. So far it appears that DHM in Ergonomics are rather limited to some traditional applications. According to Dul et al. (2012), future characteristics of Human Factors and Ergonomics (HFE) can be assigned to six main trends: (1) global change of work systems, (2) cultural diversity, (3) ageing, (4) information and communication technology (ICT), (5) enhanced competiveness and the need for innovation, and; (6) sustainability and corporate social responsibility. Based on a literature review, we systematically investigate the capabilities of current ergonomic DHM systems versus the ‘Future of Ergonomics’ requirements. It is found that DHMs already provide broad functionality in support of trends (1) and (2), and more limited options in regards to trend (3). Today’s DHM provide access to a broad range of national and international databases for correct differentiation and characterization of anthropometry for global populations. Some DHM explicitly address social and cultural modeling of groups of people. In comparison, the trends of growing importance of ICT (4), the need for innovation (5) and sustainability (6) are addressed primarily from a hardware-oriented and engineering perspective and not reflected in DHM. This reflects a persistent separation between hardware design (engineering) and software design (information technology) in the view of DHM – a disconnection which needs to be urgently overcome in the era of software defined user interfaces and mobile devices. The design of a mobile ICT-device is discussed to exemplify the need for a comprehensive future DHM solution. Designing such mobile devices requires an approach that includes organizational aspects as well as technical and cognitive ergonomics. Multiple interrelationships between the different aspects result in a challenging setting for future DHM. In conclusion, the ‘Future of Ergonomics’ pose particular challenges for DHM in regards to the design of mobile work systems, and moreover mobile information access.

Exchanging data between Digital Human Modelling systems : a review of data formats

Digital human modeling (DHM) systems underwent significant development within the last years. They achieved constantly growing importance in the field of ergonomic workplace design, product development, product usability, ergonomic research, ergonomic education, audiovisual marketing and the entertainment industry. They help to design ergonomic products as well as healthy and safe socio-technical work systems. In the domain of scientific DHM systems, no industry specific standard interfaces are defined which could facilitate the exchange of 3D solid body data, anthropometric data or motion data. The focus of this article is to provide an overview of requirements for a reliable data exchange between different DHM systems in order to identify suitable file formats. Examples from the literature are discussed in detail. Methods: As a first step a literature review is conducted on existing studies and file formats for exchanging data between different DHM systems. The found file formats can be structured into different categories: static 3D solid body data exchange, anthropometric data exchange, motion data exchange and comprehensive data exchange. Each file format is discussed and advantages as well as disadvantages for the DHM context are pointed out. Case studies are furthermore presented, which show first approaches to exchange data between DHM systems. Lessons learnt are shortly summarized. Results: A selection of suitable file formats for data exchange between DHM systems is determined from the literature review.

Responding to literature : accessible texts for reluctant readers

The Australian Curriculum: English 5.2 states, across all year level descriptions, that “students engage with a variety of texts for enjoyment”, with the level types of texts and levels of understanding developing over time (ACARA, 2014a). Problems arise when students are unable or unwilling to enjoy texts, and are reluctant to read, view, interpret, and evaluate written texts. This in turn impedes their ability to perform these texts for assessment purposes. The literacy abilities of students can vary widely within a single classroom, and it is a challenge for teachers to source and present texts which are accessible across the spectrum of reading abilities, as well as reflecting themes that are relevant and engaging for students, in addition to being consistent with the General Capabilities and Cross-Curriculum Priorities of the AC:E. In senior English also, the mainstream Qld Senior Syllabus (QSA, 2010, p. 6) requires that students have learning experiences developed through 15-20 literary texts, including the in-depth study of a complete novel. In the leisure context of English Communications, students may also “write stories, poems, or song lyrics” (QSA, 2004, p. 14). Since students’ responses to literature often take the form of other imaginative text creation we address this in this paper. We start by offering synopses of some accessible texts and strategies for teachers with these students who are unwilling or low literacy readers in junior secondary and senior level English. This paper canvases some easily read novels and some films with companion text suggestions which may serve as models for students responses. For the junior secondary texts, we identify how these align with the architecture of the Australian Curriculum’s General Capabilities and Cross Curriculum Priorities. Then, we will outline some suitable imaginative responses as possible assessment outcomes, such as short stories and digital stories.

Boken, berättelsen, pengarna I den digitala tidsåldern [The book, the story and the money in the digital age]

År 2012 är distribution av litteratur via internet inte längre en framtidsvision, utan ett etablerat format vid sidan av traditionella format som exempelvis pocketboken, den inbundna boken och ljudboken (AAP 2011; Amazon 2011; PaidContent 2011). Men den digitala tekniken etablerar inte enbart ett nytt format, utan förändrar också grundförutsättningarna för litterära konstformer och marknader. Detta kapitel behandlar en betydelsefull aspekt av denna förändring, nämligen hur den digitala tekniken påverkar relationen mellan läsare och författare och ökar läsarens inflytande över den kreativa processen. I den digitala tidsåldern är det möjligt att skapa berättelser online i en interaktiv process som involverar både läsare och författare. Kapitlet presenterar modeller för hur sådan “samproducerad e-litteratur” förändrar marknaden för litteratur och hur den påverkar den traditionella litteraturen.

Educating for digital futures : what the learning strategies of digital media professionals can teach higher education

This article explores how universities might engage more effectively with the imperative to develop students’ 21st century skills for the information society, by examining learning challenges and professional learning strategies of successful digital media professionals. The findings of qualitative interviews with professionals from Australian games, online publishing, apps and software development companies reinforce an increasing body of literature that suggests that legacy university structures and pedagogical approaches are not conducive to learning for professional capability in the digital age. Study participants were ambivalent about the value of higher education to digital careers, in general preferring a range of situated online and face-to-face social learning strategies for professional currency. This article draws upon the learning preferences of the professionals in this study to present a model of 21st century learning, as linked with extant theory relating to informal, self-determined learning and communities of practice.