Performance evaluation of three-level Z-source inverters under semiconductor-failure conditions

This paper evaluates and proposes various compensation methods for three-level Z-source inverters under semiconductor-failure conditions. Unlike the fault-tolerant techniques used in traditional three-level inverters, where either an extra phase-leg or collective switching states are used, the proposed methods for three-level Z-source inverters simply reconfigure their relevant gating signals so as to ride-through the failed semiconductor conditions smoothly without any significant decrease in their ac-output quality and amplitude. These features are partly attributed to the inherent boost characteristics of a Z-source inverter, in addition to its usual voltage-buck operation. By focusing on specific types of three-level Z-source inverters, it can also be shown that, for the dual Z-source inverters, a unique feature accompanying it is its extra ability to force common-mode voltage to zero even under semiconductor-failure conditions. For verifying these described performance features, PLECS simulation and experimental testing were performed with some results captured and shown in a later section for visual confirmation.

Dual Z-source inverter with three-level reduced common mode switching

This paper presents the design of a dual Z-source inverter that can be used with either a single dc source or two isolated dc sources. Unlike traditional inverters, the integration of a properly designed Z-source network and semiconductor switches to the proposed dual inverter allows buck-boost power conversion to be performed over a wide modulation range with three-level output waveforms generated. The connection of an additional transformer to the inverter ac output also allows all generic wye- or delta-connected loads with three-wire or four-wire configuration to be supplied by the inverter. Modulation-wise, the dual inverter can be controlled using a carefully designed carrier-based pulse-width modulation (PWM) scheme that always will ensure balanced voltage boosting of the Z-source network, while simultaneously achieving reduced common-mode switching. Because of the omission of dead-time delays in the dual inverter PWM scheme, its switched common-mode voltage can be completely eliminated, unlike in traditional inverters where narrow common-mode spikes are still generated. Under semiconductor failure conditions, the presented PWM schemes can easily be modified to allow the inverter to operate without interruption and for cases where two isolated sources are used, zero common-mode voltage can still be ensured. These theoretical findings together with the inverter practicality have been confirmed both in simulations using PSIM with Matlab/Simulink coupler and experimentally using a laboratory implemented inverter prototype.

Dual Z-source inverter with three-level reduced common-mode switching

This paper presents the design of a dual Z-source inverter that can be used with either a single dc source or two isolated dc sources. Unlike traditional inverters, the integration of a properly designed Z-source network and semiconductor switches to the proposed dual inverter allows buck-boost power conversion to be performed over a wide modulation range, with three-level output waveforms generated. The connection of an additional transformer to the inverter ac output also allows all generic wye-or delta-connected loads with three-wire or four-wire configuration to be supplied by the inverter. Modulationwise, the dual inverter can be controlled using a carefully designed carrier-based pulsewidth-modulation (PWM) scheme that will always ensure balanced voltage boosting of the Z-source network while simultaneously achieving reduced common-mode switching. Because of the omission of dead-time delays in the dual-inverter PWM scheme, its switched common-mode voltage can be completely eliminated, unlike in traditional inverters, where narrow common-mode spikes are still generated. Under semiconductor failure conditions, the presented PWM schemes can easily be modified to allow the inverter to operate without interruption, and for cases where two isolated sources are used, zero common-mode voltage can still be ensured. These theoretical findings, together with the inverter practicality, have been confirmed in simulations both using PSIM with Matlab/Simulink coupler and experimentally using a laboratory-implemented inverter prototype.

Reconceptualizing digital service quality : a call-to-action and research approach

The nature of services and service delivery has been changing rapidly since the 1980’s when many seminal papers in services research were published. Services are increasingly digital, or have a digital component. Further, a large and heterogeneous literature, with competing and overlapping definitions, many of which are dated and inappropriate to contemporary digital services offerings is impeding progress in digital services research. In this conceptual paper, we offer a critical review of some existing conceptualizations of services and digital services. We argue that an inductive approach to understanding cognition about digital services is required to develop a taxonomy of digital services and a new vocabulary. We argue that this is a pre-requisite to theorizing about digital services, including understanding quality drivers, value propositions, and quality determinants for different digital service types. We propose a research approach for reconceptualising digital services and service quality, and outline methodological approaches and outcomes.

Road infrastructure vulnerability to groundwater table variation due to sea level rise

This study was conducted to assess the vulnerability of coastal road infrastructures due to climate change induced sea level rise and extreme weather conditions through the estimation of road subgrade strength reduction as a result of changes in soil moisture content. The study area located in the Gold Coast, Australia highlighted that the risk is significant. In wet seasons or areas with wet condition, the groundwater table is already high, so even a small change in the groundwater table can raise the risk of inundation; particularly, in areas with existing shallow groundwater. The predicted risk of a high groundwater table on road infrastructure is a long-term hazard. Therefore, there is time to undertake some management plans to decrease the possible risks, for instance, some deep root plants could be planted along the roads with a high level of risk, to decrease the groundwater table elevation.

The location patterns of artistic clusters : a metro- and neighborhood-level analysis

Analysing census and industry data at the metro and neighbourhood levels, this paper seeks to identify the location characteristics associated with artistic clusters and determine how these characteristics vary across different places. We find that the arts cannot be taken overall as an urban panacea, but rather that their impact is place-specific and policy ought to reflect these nuances. However, our work also finds that, paradoxically, the arts’ role in developing metro economies is as highly underestimated as it is overgeneralised. While arts clusters exhibit unique industry, scale and place-specific attributes, we also find evidence that they cluster in ‘innovation districts’, suggesting they can play a larger role in economic development. To this end, our results raise important questions and point toward new approaches for arts-based urban development policy that look beyond a focus on the arts as amenities to consider the localised dynamics between the arts and other industries.

Evaluation of emerging intelligent transport systems to improve safety on level crossings : an overview

Safety at railway level crossings (RLX) is one part of a wider picture of safety within the whole transport system. Governments, the rail industry and road organisations have used a variety of countermeasures for many years to improve RLX safety. New types of interventions are required in order to reduce the number of crashes and associated social costs at railway crossings. This paper presents the results of a large research program which aimed to assess the effectiveness of emerging Intelligent Transport Systems (ITS) interventions, both on-road and in-vehicle based, to improve the safety of car drivers at RLXs in Australia. The three most promising technologies selected from the literature review and focus groups were tested in an advanced driving simulator to provide a detailed assessment of their effects on driver behaviour. The three interventions were: (i) in-vehicle visual warning using a GPS/smartphone navigation-like system, (ii) in-vehicle audio warning and; (iii) on-road intervention known as valet system (warning lights on the road surface activated as a train approaches). The effects of these technologies on 57 participants were assessed in a systematic approach focusing on the safety of the intervention, effects on the road traffic around the crossings and driver’s acceptance of the technology. Given that the ITS interventions were likely to provide a benefit by improving the driver’s awareness of the crossing status in low visibility conditions, such conditions were investigated through curves in the track before arriving at the crossing. ITS interventions were also expected to improve driver behaviour at crossings with high traffic (blocking back issue), which were also investigated at active crossings. The key findings are: (i) interventions at passive crossings are likely to provide safety benefits; (ii) the benefits of ITS interventions on driver behaviour at active crossings are limited; (iii) the trialled ITS interventions did not show any issues in terms of driver distraction, driver acceptance or traffic delays; (iv) these interventions are easy to use, do not increase driver workload substantially; (v) participants’ intention to use the technology is high and; (vi) participants saw most value in succinct messages about approaching trains as opposed to knowing the RLX locations or the imminence of a collision with a train.

An investigation approach to test protection intelligent electronic devices (IEDs) in IEC 61850 based substation automation systems (SAS) at station level

This thesis has developed a new approach to trace virtual protection signals in Electrical substation networks. The main goal of the research was to analyse the contents of the virtual signals transferred, using third party software. In doing so, a comprehensive test was done on a distance protection relay, using non-conventional test equipment.

A multi-level ecological model of psychotropic prescribing to adults with intellectual disability

Purpose – Simple linear accounts of prescribing do not adequately address reasons “why” doctors prescribe psychotropic medication to people with intellectual disability (ID). Greater understanding of the complex array of factors that influence decisions to prescribe is needed. Design/methodology/approach – After consideration of a number of conceptual frameworks that have potential to better understand prescribing of psychotropic medication to adults with ID, an ecological model of prescribing was developed. A case study is used to outline how the model can provide greater understanding of prescribing processes. Findings – The model presented aims to consider the complexity and multi-dimensional nature of community-based psychotropic prescribing to adults with ID. The utility of the model is illustrated through a consideration of the case study. Research limitations/implications – The model presented is conceptual and is as yet untested. Practical implications – The model presented aims to capture the complexity and multi-dimensional nature of community-based psychotropic prescribing to adults with ID. The model may provide utility for clinicians and researchers as they seek clarification of prescribing decisions. Originality/value – The paper adds valuable insight into factors influencing psychotropic prescribing to adults with ID. The ecological model of prescribing extends traditional analysis that focuses on patient characteristics and introduces multi-level perspectives that may provide utility for clinicians and researchers.

Communicating engagement in corporate social responsibility : a meta-level construal of engagement

Organizations are increasingly seeking stakeholder support through engagement to demonstrate their corporate social responsibility (CSR) credentials. These credentials are in turn used to support claims of legitimacy for organizational operations. This paper uses a process model of antecedents, implementation, and consequences to study the connection between engagement and CSR. CSR reports show organizations perceive engagement in CSR as both communication and activities between organizations and their stakeholders; and as a second, meta-level of communication about that engagement with stakeholders beyond those directly involved, thereby broadening the scope of organizational claims to legitimacy. Understanding what engagement is and how and why it is carried out in CSR provides a framework for understanding engagement in public relations.

A three-level flying-capacitor rectifier based supercapacitor direct integration scheme for distributed generation systems

Supercapacitors are increasingly used as short term energy storage elements in distributed generation systems. The traditional approach in integrating them to the main system is the use of interfacing dc-dc converters which introduce additional costs and power losses. This paper therefore, presents a novel direct integration scheme for supercapacitors and thereby eliminates associated costs and power losses of interfacing converters. The idea is simply to replace ordinary capacitors of three-level flying-capacitor rectifiers with supercapacitors and operate them under variable voltage conditions. An analysis on the reduction of power losses by the proposed system is presented. Furthermore, supercapacitor sizing and implementation issues such as effects of the variable voltage operation and resistive behavior of supercapacitors at high frequencies are also discussed. Simulation results are presented to verify the efficacy of the proposed system in suppressing short term power fluctuations in wind generation system.

The impact of employment-level characteristics on work-life interference in school aged children

Work–life interference is important for school-aged workers because it influences their educational outcomes/career aspirations. Although research highlights the role of work hours in determining work–life interference for these workers, work/job-level characteristics have received limited attention. Using survey data from Queensland school students who work part-time, we assess the influence of a range of employment-level variables on work–life interference. The results of multiple regression analysis indicate work–life interference is exacerbated by having low trust in managers and limited scope to refuse work hours and stability in work hours, emphasising the importance of organisational variables in integrating work and non-work spheres for school-aged workers.

Design research for the real world : a design-led innovation model for action research

The aim of this paper is to aid researchers in undertaking action research within industry with a particular focus on the study of design-led innovation. This paper presents the research design of a case study shaped to solve real world problems concerning a major Australian Airport Corporation by bridging the chasm between academia and industry. The researcher’s role is one of design-innovation catalyst, facilitating the integration of design as a new strategic capability and innovation approach within an organisation’s fabric. A discussion of the researcher experience within industry will provide evidence on the challenges facing such a research role, with strategies for overcoming these barriers presented. Based on the authors’ experience as a researcher within industry and reflection within practice, a project progression model for action research is presented to enable the improved management of industry based research.

The 1989 Comprehensive Plan of Action (CPA) and refugee policy in Southeast Asia : twenty years forward what has changed?

In 2012, the only South East Asian countries that have ratified the 1951 Convention relating to the Status of Refugees and the 1967 Protocol Relating to the Status of Refugees (hereafter referred to as the 1951 Convention and 1967 Protocol) is Philippines (signed 1954), Cambodia (signed 1995) and Timor Leste (signed 2001). Countries such as Indonesia, Malaysia and Thailand have annual asylum seeking populations from Myanmar, South Asia and Middle East, that are estimated to be at 15 000-20 000 per country (UNHCR 2012). The lack of a permanent and formal asylum processing process in these countries means that that asylum-seeking populations in the region are reliant on the local offices of the United Nations High Commission for Refugees based in the region to process their claims. These offices rely upon the good will of these governments to have a presence near detection camps and in capital cities to process claims of those who manage to reach the UNHCR representative office. The only burden sharing mechanism within the region primarily exists under the Bali Process on People Smuggling, Trafficking in Persons and Related Transnational Crime (the Bali Process), introduced in 2002. The Bali Process refers to an informal cooperative agreement amongst the states from the Asia-Pacific region, with Australia and Indonesia as the co-chairs, which discusses its namesake: primarily anti-people smuggling activities and migration protocols. There is no provision within this process to discuss the development of national asylum seeking legislation, processes for domestic processing of asylum claims or burden sharing in contrast to other regions such as Africa and South America (i.e. 2009 African Union Convention for the Protection and Assistance of the Internally Displaced, 1969 African Union Convention Governing the Specific Aspects of Refugee Problems in Africa and 1984 Cartagena Declaration on Refugees [Americas]) (PEF 2010: 19).

Climbing the design ladder : step by step

This research presents findings of a research project where the first author worked with a small to medium sized enterprise (SME) manufacturing company in order to integrate design at a strategic level within the company. This study aims to identify the changes experienced in the participating company while shifting the perspective of design from a product focus towards a strategic focus. Staff interviews at two points in time and a reflective journal were used as data sources within an action research methodology. A shift in the perspective of design was noted in three cultural changes within the firm over time: a focus on long term as well as short term outcomes, on indirect as well as direct value and on intangible as well as tangible benefits. These three components are proposed as ‘cultural stepping stones’ that describe how a company transitions from an exclusively product- focused utilisation of design, to a process-level application of design. Implications of this research are provided as considerations for businesses that are attempting to facilitate a similar transformation in the future.